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Potential use of Rapamycin in HIV infection: Rapamycin for HIV treatment
British Journal of Clinical Pharmacology
Abstract
The strong need for the development of alternative anti-HIV agents is primarily due to the emergence of strain-resistant viruses, the need for sustained adherence to complex treatment regimens and the toxicity of currently used antiviral drugs. This review analyzes proof of concept studies indicating that the immunomodulatory drug rapamycin (RAPA) possesses anti-HIV properties both in vitro and in vivo that qualifies it as a potential new anti-HIV drug. It represents a literature review of published studies that evaluated the in vitro and in vivo activity of RAPA in HIV. RAPA represses HIV-1 replication in vitro through different mechanisms including, but not limited, to down regulation of CCR5. In addition RAPA synergistically enhances the anti-HIV activity of entry inhibitors such as vicriviroc, aplaviroc and enfuvirtide in vitro. RAPA also inhibits HIV-1 infection in human peripheral blood leucocytes-SCID reconstituted mice. In addition, a prospective nonrandomized trial of HIV patient series receiving RAPA monotherapy after liver transplantation indicated significantly better control of HIV and hepatitis C virus (HCV) replication among patients taking RAPA monotherapy. Taken together, the evidence presented in this review suggests that RAPA may be a useful drug that should be evaluated for the prevention and treatment of HIV-1 infection.
... Sirolimus (SIR) is an immunosuppressive agent frequently used in kidney transplantation. 1 SIR exerts its action through inhibition of mammalian target of rapamycin (mTOR), a ubiquitous serine/threonine kinase that regulates multiple intracellular pathways involved in cellular growth, proliferation, differentiation and metabolism. 2 Interestingly, SIR has been shown to determine in vitro 3 and in vivo 4,5 downregulation of C-C chemokine receptor type 5 (CCR5), one of two co-receptors commonly used by HIV-1 to enter and infect CD4-expressing immune cells. 6 Based on these results, SIR may be a potential alternative immunosuppressive agent in the treatment of HIV-infection in solid organ transplant recipients. ...
... 6 Based on these results, SIR may be a potential alternative immunosuppressive agent in the treatment of HIV-infection in solid organ transplant recipients. [3][4][5] In this case report, we describe for the first time the use of SIR to control low-level HIV-1 replication in an HIV þ kidney transplant (KT) recipient. ...
... SIR possesses anti-viral proprieties in the setting of HIV infection. 3 Similarly, to a new class of antiretroviral drugs termed entry inhibitors, SIR reduces the expression of CCR5 on lymphocytes by interfering with IL-2 signaling. A study showed that SIR reaches this effect at blood concentrations lower than those used in KT recipients; therefore, patients treated with SIR may theoretically benefit from its antiretroviral effects without any increases in the total dose of the drug. ...
Sirolimus (SIR) is a potent immunosuppressive agent with multiple proprieties. We report beneficial antiviral effects of SIR in an HIV-positive kidney transplant recipient who experienced low-level HIV-1 replication. The immunosuppressive agent was well tolerated by the patient, and no side effects were reported during follow-up. Despite immunosuppressive monotherapy, SIR ensured stable graft function.
... Similar study revealed that sirolismus; a rapamycin, downregulates CCR5 density on lymphocytes (Heredia et al., 2003). In another study, sirolismus greatly enhances Vicriviroc activity against HIV-1 (Donia et al., 2010). Sirolismus/Vicriviroc combinations demonstrated a considerable synergistic activity that translated into Vicriviroc dose reductions of up to 65-fold (Donia et al., 2010). ...
... In another study, sirolismus greatly enhances Vicriviroc activity against HIV-1 (Donia et al., 2010). Sirolismus/Vicriviroc combinations demonstrated a considerable synergistic activity that translated into Vicriviroc dose reductions of up to 65-fold (Donia et al., 2010). Theoretically, it may not seem appropriate to use immunosuppressive drugs in HIV-1 infected individuals. ...
This study was aimed at identifying two promising generic drugs and conduct an antiviral drug combination studies against HIV. It has two components; computational and in-vitro studies. The computational study entails sequential screening of all FDA approved drugs (1491) against three protein targets; through structural-and ligand-based pharmacophore screening followed by molecular docking of the selected drugs against the viral targets. Two (2) drugs with the best binding affinities against the viral targets were chosen for an in-vitro confirmation of activity. The non-toxic concentrations used for the study were established from MTT cytotoxicity study using C max of the drugs as a guide. Iodixanol and sirolismus had the highest binding affinities against the three protein targets. In the antiviral drug combination studies, synergism (CI<1) were demonstrated at the three graded concentrations.
... [10][11] Upregulated expression of this pathway has been observed in several diseases of neoplastic, autoimmune, and viral origin and is thought to be implicated in the pathogenesis of the disease. 10,[12][13][14] This has led to the hypothesis that single or dual inhibitors of this pathway could ameliorate the course of SARS-CoV-2 infection. Single inhibitors of PI3K, Akt, and mTOR have been approved for the treatment of different conditions, primarily, but not exclusively, of a neoplastic nature. ...
... mTOR inhibitors have previously bee shown to suppress HIV infection in vitro and in vivo, in preclinical settings. 13 In agreement with these data, everolimus significantly reduced HIV RNA levels in ARTsuppressed individuals who received solid organ transplantation. 37 In addition, Kindrachuk et al. showed that rapamycin inhibited MERS infection in vitro by 61% at a 10 lM concentration. ...
Coronavirus disease 2019 (COVID-19) has emerged as a serious threat to global health. The disregulation of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) cell signaling pathway observed in patients with COVID-19 has attracted attention for the possible use of specific inhibitors of this pathway for the treatment of the disease. Here, we review emerging data on the involvement of the PI3K/Akt/mTOR pathway in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the clinical studies investigating its tailored inhibition in COVID-19. Current in silico, in vitro, and in vivo data convergently support a role for the PI3K/Akt/mTOR pathway in COVID-19 and suggest the use of specific inhibitors of this pathway that, by a combined mechanism entailing downregulation of excessive inflammatory reactions, cell protection, and antiviral effects, could ameliorate the course of COVID-19.
... Initial studies report on sirolimus use in HIV-positive KTR in addition to cyclosporine and steroids because of its potential antiviral and milder immunosuppressive effects [11,34]. Reports have shown that mTOR inhibitors can potentiate certain ART (efuvirtide, efavirenz, and CCR5 inhibitors), as well as having in-vivo and in-vitro antiviral activity demonstrated by reducing CCR5 expression, viral reactivation, and postkidney transplantation HIV persistence [40][41][42][43][44][45]. However, studies that reported on the use of sirolimus as maintenance immunosuppression found higher rejection rates. ...
Purpose of study:
The purpose of this review is to provide the current state of immunosuppression therapy in kidney transplant recipients (KTR) with HIV and to discuss practical dilemmas to better understand and manage these patients.
Recent findings:
Certain studies find higher rates of rejection, which raises the need to critically assess the approach to immunosuppression management in HIV-positive KTR. Induction immunosuppression is guided by transplant center-level preference rather than by the individual patient characteristics. Earlier recommendations expressed concerns about the use of induction immunosuppression, especially utilizing lymphocyte-depleting agents; however, updated guidelines based on newer data recommend that induction can be used in HIV-positive KTR, and the choice of agent be made according to immunological risk. Likewise, most studies point out success with using first-line maintenance immunosuppression including tacrolimus, mycophenolate, and steroids. In selected patients, belatacept appears to be a promising alternative to calcineurin inhibitors with some well established advantages. Early discontinuation of steroids in this population carries a high risk of rejection and should be avoided.
Summary:
Immunosuppression management in HIV-positive KTR is complex and challenging, mainly because of the difficulty of maintaining a proper balance between rejection and infection. Interpretation and understanding of the current data towards a personalized approach of immunosuppression could improve management in HIV-positive KTR.
... For example, the mTOR inhibitors, everolimus and rapamycin, have been shown to suppress HIV or MERS infection in preclinical settings. 105,317 Recent reports suggest a role for the PI3K/Akt/mTOR pathway in anti-SARS-CoV-2. Repurposing of targeted inhibitors of this pathway could help downregulate excessive inflammatory responses and exhibit antiviral effects. ...
The coronavirus disease 2019 (COVID-19) pandemic has affected a large portion of the global population, both physically and mentally. Current evidence suggests that the rapidly evolving coronavirus subvariants risk rendering vaccines and antibodies ineffective due to their potential to evade existing immunity, with enhanced transmission activity and higher reinfection rates that could lead to new outbreaks across the globe. The goal of viral management is to disrupt the viral life cycle as well as to relieve severe symptoms such as lung damage, cytokine storm, and organ failure. In the fight against viruses, the combination of viral genome sequencing, elucidation of the structure of viral proteins, and identifying proteins that are highly conserved across multiple coronaviruses has revealed many potential molecular targets. In addition, the time- and cost-effective repurposing of preexisting antiviral drugs or approved/clinical drugs for these targets offers considerable clinical advantages for COVID-19 patients. This review provides a comprehensive overview of various identified pathogenic targets and pathways as well as corresponding repurposed approved/clinical drugs and their potential against COVID-19. These findings provide new insight into the discovery of novel therapeutic strategies that could be applied to the control of disease symptoms emanating from evolving SARS-CoV-2 variants.
... [59] It has been shown that rapamycin, an inhibitor of the mTOR signal pathway, reduces HIV-1 replication and transcription. [66] In the strategy of combination with immune activation, it relieves the effects of various toxic cytokines produced by the inflammatory response. [67] Metformin, a widely used antidiabetic drug, was recently shown to modulate T-cell activation and inflammation by suppressing the mTOR pathway. ...
Acquired immune deficiency syndrome is still one of the most severe global infectious diseases that pose a significant threat to human health. With the successful application of antiretroviral therapy, productive replication of human immunodeficiency virus type 1 (HIV-1) can be effectively blocked; however, antiretroviral therapy alone cannot cure the infection because of the presence of a stable and reactivatable viral latent reservoir. Thus, it is of great importance to have a better comprehension of the mechanisms driving HIV-1 pathogenesis and long-term persistence in infected individuals, based on which to further discover novel targets for therapeutic applications to treat or even cure the infection. Various studies have revealed that cellular metabolism is a critical factor impacting the fate and intracellular activities of immune cells. Emerging evidence implies that the alternations of cellular metabolism induced by HIV-1 infection play an important role in HIV-1 pathogenesis. Consequently, a promising approach of “metabolism as a therapeutic target” raised the possibility of using metabolic reprogramming as a treatment option for chronic HIV-1 infection. In this review, we summarize the latest studies about the interplay of the hosts' reprogramming of glucose metabolism and HIV-1 infection and introduce potential applications of searching for hallmarks and therapeutic targets of metabolic interventions for HIV-1 infection.
... Autophagy can be detected by counting LC3 puncta using confocal microscopy, detecting double-membrane vesicles by transmission electron microscopy or by flow cytometry, however these assays have been used on fluorescent reporter constructs like GFP-LC3 in cell lines and are nor ideal to study mixed populations of primary cells like peripheral lymphocytes. In addition, we cannot rule out that the observed inhibition of HIV replication in HLACs with autophagy modulators is only due to their effect on autophagy since these drugs have an impact in multiple metabolic pathways 38,39 . ...
A complex link exists between HIV-1 and autophagy, and discordant results have been reported in different in vitro models regarding the way HIV and autophagy modulate each other. Despite this, there is very limited knowledge about the interplay between HIV and autophagy in vivo in lymphoid tissue, due in part by the lack of cell models that recapitulate the in vivo setting. Here, we evaluate the interrelationship between HIV and autophagy using human ex vivo lymphoid tissue cultures as an HIV infection model. Our results showed that human lymphoid aggregated cultures (HLACs) from tonsillar tissue displayed fully functional autophagic activity. In this system, HIV infection resulted in an increase in autophagy. Notably, we observed that both, autophagy-enhancing (rapamycin) or blocking drugs (3-methyladenine, chloroquine and bafilomycin), were able to decrease HIV-DNA levels and HIV replication. Therefore, efficient HIV-1 replication requires a fine-tuned level of autophagy, so modifications of this balance will have a negative impact on its replication. Therefore, targeting the autophagic pathway could be a new therapeutic approach to be explored to treat HIV-1 infection. Ex vivo cultures of human lymphoid tissue are a suitable model to obtain further insights into HIV and its intricate relationship with autophagy.
... The use of PI3K inhibitors and mTOR inhibitors, such as rapamycin, is associated with an increase in autophagy, through the relocalization of TFEB (Campbell et al., 2015). Drugs targeting the mTOR pathway and the upstream PI3K/Akt pathway could be used to counter the HIV-1 induced inhibition of autophagy, and therefore alter the viral replication (Donia et al., 2010). Additionally, serum starvation has been show to induce HIV reactivation in in vitro models, and therapeutic approaches derived from it could complement the other strategies (Raja et al., 2018). ...
The protein kinase B or Akt is a central regulator of survival, metabolism, growth and proliferation of the cells and is known to be targeted by various viral pathogens, including HIV-1. The central role of Akt makes it a critical player in HIV-1 pathogenesis, notably by affecting viral entry, latency and reactivation, cell survival, viral spread and immune response to the infection. Several HIV proteins activate the PI3K/Akt pathway, to fuel the progression of the infection. Targeting Akt could help control HIV-1 entry, viral latency/replication, cell survival of infected cells, HIV spread from cell-to-cell, and the immune microenvironment which could ultimately allow to curtail the size of the HIV reservoir. Beside the “shock and kill” and “block and lock” strategies, the use of Akt inhibitors in combination with latency inducing agents, could favor the clearance of infected cells and be part of new therapeutic strategies with the goal to “block and clear” HIV.
... Pharmacological treatment with rapamycin decreased viral spreading [99]. Another study implied that the HIV-1 protein Nef initiates mTOR activation which can be blocked by inhibitors of mTOR or PI3K [100,101], suggesting that drugs that modify the mTORC1 signaling pathway could act as anti-HIV-1 agents [102,103]. ...
Because of their epidemic and pandemic potential, emerging viruses are a major threat to global healthcare systems. While vaccination is in general a straightforward approach to prevent viral infections, immunization can also cause escape mutants that hide from immune cell and antibody detection. Thus, other approaches than immunization are critical for the management and control of viral infections. Viruses are prone to mutations leading to the rapid emergence of resistant strains upon treatment with direct antivirals. In contrast to the direct interference with pathogen components, host-directed therapies aim to target host factors that are essential for the pathogenic replication cycle or to improve the host defense mechanisms, thus circumventing resistance. These relatively new approaches are often based on the repurposing of drugs which are already licensed for the treatment of other unrelated diseases. Here, we summarize what is known about the mechanisms and modes of action for a potential use of antifungals as repurposed host-directed anti-infectives for the therapeutic intervention to control viral infections.
... Hence, it could be hypothesized that kaempferol may also be useful for conditions characterized by dysregulated autophagy, such as HIV-associated neurodegenerative diseases. Additionally, it also can be assumed that kaempferol may be effective against diseases characterized by abnormal activation of the PIK3/Akt/mTOR pathway that benefit from mTOR inhibitors, including infectious diseases, such as HIV and severe acute respiratory syndrome coronavirus 2 (41)(42)(43), and autoimmune diseases, such as multiple sclerosis and systemic lupus erythematosus (44)(45)(46), as well as cancer (47)(48)(49). ...
Kaempferol, a flavonoid compound, has various biological functions, such as anti‑inflammatory and antitumor activities. Acute liver failure (ALF) is a lethal clinical syndrome that occurs due to severe damage of the liver function. In the present study, the mechanisms underlying the therapeutic effects of kaempferol in ALF were evaluated. An ALF mouse model was established using D‑galactosamine (D‑GalN; 700 mg/kg)/lipopolysaccharide (LPS; 10 µg/kg). A total of 2 h before the administration of D‑GalN/LPS, mice were pretreated with different doses of kaempferol (2.5, 5, 10, 20 and 40 mg/kg), and 6 h after injection of D‑GalN/LPS, mice were euthanized. The survival rate, liver function and levels of inflammatory cytokines were assessed. The results demonstrated that kaempferol pretreatment protected hepatocytes from ALF induced by D‑GalN/LPS via regulation of the autophagy pathway, both in vivo and in vitro. Pretreatment with a high dose of kaempferol significantly decreased the survival rates and increased severe liver damage; however, pretreatment with a low dose of kaempferol had the opposite effect. Furthermore, pretreatment with a high dose of kaempferol enhanced the levels of proinflammatory cytokines [TNF‑α, IL‑6, IL‑12p40, IL‑1β, C‑X‑C motif chemokine ligand (CXCL)‑2, CXCL‑10] and markers of the MAPK signaling pathway [phosphorylated (p)‑JNK, p‑ERK, p‑p38], whereas pretreatment with a low dose of kaempferol had the opposite effect. Pretreatment with a high dose of kaempferol decreased autophagy, whereas pretreatment with a low dose of kaempferol increased autophagy in vivo and in vitro. It was also shown that pretreatment with 3‑methyadenine or autophagy related 7 small interfering RNA, to inhibit autophagy, partially abrogated the hepatoprotective effects of pretreatment with 5 mg/kg kaempferol in the ALF mouse model. These results demonstrate that the effects of different doses of kaempferol on D‑GalN/LPS‑induced ALF varies based on the dose, and that kaempferol exerted its effects via regulation of the autophagy pathway.
... 6E and 6F), indicating that mTOR maintains normal NK cell physiology. It has been suggested that mTOR inhibition may serve as an effective intervention to control HIV-1 infection (Besnard et al., 2016;Donia et al., 2010;Heredia et al., 2015;Martin et al., 2017). However, the data obtained here suggests that mTOR inhibition would compromise NK cell effector functions important for viral clearance. ...
Human blood innate lymphoid cells (ILCs), which include ILCs and natural killer (NK) cells, derive from a common CD117+ILC precursor (ILCP). Yet, the relationship among the ILC subsets remains unclear. Bulk and single cell RNA-Seq and ATAC-Seq showed that blood ILC subsets cluster into ILC2s, ILCPs, a mixed cluster of CD56dim and CD56− NK cells, and a separate cluster of CD56hiNK cells that share features with both ILCs and CD56dimNK cells. In surprising contrast to mice, tissue repair protein amphiregulin was produced by human NK cells, with higher levels in CD56hiNK cells than in ILCs. Amphiregulin production by human NK cells was promoted by TCF7/WNT signaling and inhibited by TGFB1, a cytokine elevated in people living with HIV-1. Knockout of RUNX3, a WNT antagonist downstream of TGFB1, increased amphiregulin production in human NK cells. CD4+T cell depletion in people living with HIV-1, or from PBMCs in tissue culture, was associated with expansion of metabolically inert, nonfunctional CD56−NK cells. Experiments in tissue culture and in humanized mice revealed that CD56−NK cells are derived from CD56dimNK cells, and that CD4+T cell-derived IL-2 stimulates MTOR activity in CD56dimNK cells to prevent this transition. These findings clarify how ILC subsets are related to each other and provide insight into how HIV-1 infection disrupts ILC homeostasis and contributes to pathology.
... One of the first evidences that mTORC1 was involved in HIV-1 infection came from the observation that treatment with rapamycin causes down-regulation of CCR5 expression in T cells (335). A number of studies that immediately followed confirmed that rapamycin possessed anti-HIV-1 properties both in vitro and in vivo, thus pointing to the mTORC1 importance during HIV-1 propagation (reviewed in (336,337)). ...
Aggressive B cell lymphomas are the main cause of death in HIV-1 infected individuals, although B cells are not targeted by the virus. The exact mechanisms of the development of these lymphomas are not known. Previous studies of our team revealed that HIV-1 Tat can penetrate B cells, where it can induce ROS production, DNA damage and increase the chances of the oncogenic translocations specific for Burkitt lymphoma. In addition in many immune cells HIV-1 and its proteins (e.g. Tat) can regulate Akt/mTORC1 pathway, a central integrator of many intra and extracellular signals including viral infection and DNA damage. However, no studies have examined the regulation of Akt/mTORC1 pathway by Tat in B cells. In this thesis I have tested the hypothesis that HIV-1 Tat might produce oncogenic effects in B cells by modulating Akt/mTORC1 signaling pathway and regulating expression of genes involved in lymphomagenesis. I found that HIV-1 Tat activated Akt/mTORC1 signaling pathway, which leads to aberrant activation of AICDA (activation induced cytidine deaminase) due to inhibition of AICDA transcriptional repressors c-Myb and E2F8. These perturbations may ultimately lead to an increased genomic instability and proliferation that might cause B cell malignancies.
... Saquinavir, the first HIV protease inhibitor made available in the market, was shown to be ineffective for inhibiting SARS-CoV replication 39,40 . Sirolimus blocked stages after the reverse transcription event in activated human T cells infected by human immunodeficiency virus 1 (HIV-1) 41 . Cetirizine, an antihistamine reported to inhibit the replication of respiratory syncytial virus (RSV) and the expression of interleukin-8 (IL-8), has an unknown property in reducing of RSV infectivity 42 . ...
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for coronavirus disease 2019 (COVID-19). Since its emergence, the COVID-19 pandemic has not only distressed medical services but also caused economic upheavals, marking urgent the need for effective therapeutics. The experience of combating SARS-CoV and MERS-CoV has shown that inhibiting the 3-chymotrypsin-like protease (3CLpro) blocks the replication of the virus. Given the well-studied properties of FDA-approved drugs, identification of SARS-CoV-2 3CLpro inhibitors in an FDA-approved drug library would be of great therapeutic value. Here, we screened a library consisting of 774 FDA-approved drugs for potent SARS-CoV-2 3CLpro inhibitors, using an intramolecularly quenched fluorescence (IQF) peptide substrate. Ethacrynic acid, naproxen, allopurinol, butenafine hydrochloride, raloxifene hydrochloride, tranylcypromine hydrochloride, and saquinavir mesylate have been found to block the proteolytic activity of SARS-CoV-2 3CLpro. The inhibitory activity of these repurposing drugs against SARS-CoV-2 3CLpro highlights their therapeutic potential for treating COVID-19 and other Betacoronavirus infections.
... Indeed, by using an anti-signature computational approach, our analysis showed that the mTOR inhibitor, sirolimus, may be a candidate drug to be used in cOVId-19 patients, which is in line with data on the activation of the phosphoinositol 3-kinase (PI3K)/AKT/mTOR pathway in response to the infection with another coronavirus, MERS-coV (54). Also, mTOR has been recognized as a key factor in regulating the replication of viruses (36,(54)(55)(56)(57), and in patients with H1N1 pneumonia, early treatment with corticosteroids in combination with rapamycin has been associated with improvement in multiple organ dysfunction, virus clearance, and shortened time in ventilators (58). ...
The outbreak of the 2019 coronavirus disease (named, COVID‑19), caused by the novel SARS‑CoV‑2 virus, represents a worldwide severe threat to public health. It is of the utmost importance to characterize the immune responses against the SARS‑CoV‑2 and the mechanisms of hyperinflammation, in order to design better therapeutic strategies for COVID‑19. In the present study, a transcriptomic analysis was performed to profile the immune signatures in lung and the bronchoalveolar lavage fluid samples from COVID‑19 patients and controls. Our data concordantly revealed increased humoral responses to infection. The elucidation of the host responses to SARS‑CoV‑2 infection may further improve our understanding of COVID‑19 pathogenesis and suggest better therapeutic strategies.
... [2][3][4][5][6][7] Despite its immunosuppressant qualities, mTOR inhibition leads to several potential beneficial immune regulatory functions that have activity against various viral pathogens, including HCV, CMV, HHV8, HPV, and HIV. [8][9][10][11][12][13][14][15][16][17] In addition, we previously reported that exposure to the mTOR inhibitor, sirolimus, in HIV-infected, antiretroviral therapy (ART)-suppressed renal transplant recipients was associated with lower post-transplant quantities of CD4+ T cell-associated HIV-1 DNA 11 . ...
Pharmacologic inhibition of the mammalian target of rapamycin (mTOR) in the setting of renal transplantation has previously been associated with lower human immunodeficiency virus 1 (HIV‐1) DNA burden, and in vitro studies suggest that mTOR inhibition may lead to HIV transcriptional silencing. Because prospective clinical trials are lacking, we conducted an open‐label, single‐arm study to determine the impact of the broad mTOR inhibitor, everolimus, on residual HIV burden, transcriptional gene expression profiles, and immune responses in HIV‐infected adult solid organ transplant (SOT) recipients on antiretroviral therapy. Whereas everolimus therapy did not have an overall effect on cell‐associated HIV‐1 DNA and RNA levels in the entire cohort, participants who maintained everolimus time‐averaged trough levels >5 ng/mL during the first 2 months of therapy had significantly lower RNA levels up to 6 months after the cessation of study drug. Time‐averaged everolimus trough levels significantly correlated with greater inhibition of mTOR gene pathway transcriptional activity. Everolimus treatment also led to decreased PD‐1 expression on certain T cell subsets. These data support the rationale for further study of the effects of mTOR inhibition on HIV transcriptional silencing in non‐SOT populations, either alone or in combination with other strategies.
Trial Registration: ClinicalTrials.gov NCT02429869.
... In addition, the inhibitor also helps in the suppression of potent CD4 + effector T cell and promotion of Treg [65,66]. Rapamycin has already been shown to exert antiviral activities against HIV and other viruses like vaccinia and influenza [67][68][69][70][71]. ...
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019. It was first reported in Wuhan, China and has since become a global health concern. Keeping in view, the magnitude of the problem, scientists around the globe are working to develop effective therapeutic strategies. This review focuses on previous findings regarding SARS-CoV, which may prove helpful in future research on SARS-CoV-2. In addition, it also highlights recent developments in medicine and biotechnology toward developing effective drugs and vaccines against SARS-CoV-2. This review will analyze available data on this topic and will help researchers develop new thoughts using information already available as a step toward developing novel therapeutic strategies against SARS-CoV-2.
... Low-dose inhibitors of mTORC1 are also beneficial in the elderly by increasing immune function and reducing infections and complications [48]. We have also generated in vivo proof-of-concept that sirolimus is effective in prevention of HIV replication in a humanized SCID model [49] and have proposed the use of rapamycin in HIV infection and its complications [50,51]. Subsequently, our in vivo data have been replicated in the same model by Heredia et al., using an ATPase inhibitor of mTOR [52], and it has been further extended by Latinoci et al., in a different mouse model of HIV infection, where they showed the synergistic antiretroviral action of rapamycin with standard antiretroviral therapy [53]. ...
The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease (COVID-19) has posed a serious threat to global health. As no specific therapeutics are yet available to control disease evolution, more in-depth understanding of the pathogenic mechanisms induced by SARS-CoV-2 will help to characterize new targets for the management of COVID-19. The present study identified a specific set of biological pathways altered in primary human lung epithelium upon SARS-CoV-2 infection, and a comparison with SARS-CoV from the 2003 pandemic was studied. The transcriptomic profiles were also exploited as possible novel therapeutic targets, and anti-signature perturbation analysis predicted potential drugs to control disease progression. Among them, Mitogen-activated protein kinase kinase (MEK), serine-threonine kinase (AKT), mammalian target of rapamycin (mTOR) and I kappa B Kinase (IKK) inhibitors emerged as candidate drugs. Finally, sex-specific differences that may underlie the higher COVID-19 mortality in men are proposed.
... Low-dose inhibitors of mTORC1 are also beneficial in the elderly by increasing immune function and reducing infections and complications [48]. We have also generated in vivo proof-of-concept that sirolimus is effective in prevention of HIV replication in a humanized SCID model [49] and have proposed the use of rapamycin in HIV infection and its complications [50,51]. Subsequently, our in vivo data have been replicated in the same model by Heredia et al., using an ATPase inhibitor of mTOR [52], and it has been further extended by Latinoci et al., in a different mouse model of HIV infection, where they showed the synergistic antiretroviral action of rapamycin with standard antiretroviral therapy [53]. ...
The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease (COVID-19) has posed a serious threat to global health. As no specific therapeutics are yet available to control disease evolution, more in-depth understanding of the pathogenic mechanisms induced by SARS-CoV-2 will help to characterize new targets for the management of COVID-19. The present study identified a specific set of biological pathways altered in primary human lung epithelium upon SARS-CoV-2 infection, and a comparison with SARS-CoV from the 2003 pandemic was studied. The transcriptomic profiles were also exploited as possible novel therapeutic targets, and anti-signature perturbation analysis predicted potential drugs to control disease progression. Among them, Mitogen-activated protein kinase kinase (MEK), serine-threonine kinase (AKT), mammalian target of rapamycin (mTOR) and I kappa B Kinase (IKK) inhibitors emerged as candidate drugs. Finally, sex-specific differences that may underlie the higher COVID-19 mortality in men are proposed.
... One of the first pieces of evidence that mTORC1 was involved in HIV-1 infection came from the observation that treatment with rapamycin causes downregulation of CCR5 expression in T cells [12]. A number of studies that immediately followed confirmed that rapamycin possessed anti-HIV-1 properties both in vitro and in vivo, pointing to the mTORC1 importance during HIV-1 propagation (reviewed in [13,14]). Pan-inhibitors of mTORC1 block HIV-1 even more efficiently, interfering both with virus entry (by reducing CCR5 levels) and with basal and induced transcription, as shown in preclinical humanized mice models [15]. ...
Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cellular proliferation and survival which controls cellular response to different stresses, including viral infection. HIV-1 interferes with the mTORC1 pathway at every stage of infection. At the same time, the host cells rely on the mTORC1 pathway and autophagy to fight against virus replication and transmission. In this review, we will provide the most up-to-date picture of the role of the mTORC1 pathway in the HIV-1 life cycle, latency and HIV-related diseases. We will also provide an overview of recent trends in the targeting of the mTORC1 pathway as a promising strategy for HIV-1 eradication.
... Selected examples of autophagy modulators are highlighted in specific pathological contexts. AATD, α1 antitrypsin deficiency; AD, Alzheimer's disease; AFLD, Alcoholic fatty liver disease; ALS, Amyotrophic lateral sclerosis; AMPK, 5 adenosine monophosphateactivated protein kinase; Atg, Autophagy-related genes; cAMP, 3 ,5 -cyclic adenosine monophosphate; DMD, Duchenne muscular dystrophy; FSD, Fibrinogen storage disease, FTD, Frontotemporal dementia; GAPR-1, bacterial pathogens both in vitro and in vivo (Donia et al., 2010). ...
Autophagy is an intracellular degradation pathway for malfunctioning aggregation-prone proteins, damaged organelles, unwanted macromolecules and invading pathogens. This process is essential for maintaining cellular and tissue homeostasis that contribute to organismal survival. Autophagy dysfunction has been implicated in the pathogenesis of diverse human diseases, and therefore, therapeutic exploitation of autophagy is of potential biomedical relevance. A number of chemical screening approaches have been established for the drug discovery of autophagy modulators based on the perturbations of autophagy reporters or the clearance of autophagy substrates. These readouts can be detected by fluorescence and high-content microscopy, flow cytometry, microplate reader and immunoblotting, and the assays have evolved to enable high-throughput screening and measurement of autophagic flux. Several pharmacological modulators of autophagy have been identified that act either via the classical mechanistic target of rapamycin (mTOR) pathway or independently of mTOR. Many of these autophagy modulators have been demonstrated to exert beneficial effects in transgenic models of neurodegenerative disorders, cancer, infectious diseases, liver diseases, myopathies as well as in lifespan extension. This review describes the commonly used chemical screening approaches in mammalian cells and the key autophagy modulators identified through these methods, and highlights the therapeutic benefits of these compounds in specific disease contexts.
... Moreover, patients with DLBCL with active PI3K/AKT/mTOR signaling experience a more rapid deterioration, with poor treatment response and shortened survival times (12). The suppression of active PI3K/AKT/mTOR signaling has been studied, and several inhibitors have been discovered; mTOR inhibitors have been shown to be effective in preclinical and clinical settings for the treatment of autoimmune diseases, cancer and infectious diseases, such as HIV (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Furthermore, dual inhibitors of PI3K and mTOR, including GSK2126458A and NVP-BEZ235, are being developed for cancer that show promising chemotherapeutic profiles in different settings (25)(26)(27). ...
Diffuse large B cell lymphoma (DLBCL) represents the most common subtype of non‑Hodgkin lymphoma in China. 1,25‑Dihydroxyvitamin D3 [1,25(OH)2D3] has been shown to possess significant antitumor potential and is degraded by 25‑hydroxyvitamin D‑24‑hydroxylase (CYP24A1). In the present study, the role of CYP24A1 and autophagy, and their underlying mechanisms in the anticancer effects of 1,25(OH)2D3 in DLBCL cells, were investigated. It was found that the levels of CYP24A1 in DLBCL lymph node tissues were higher than in hyperplasia lymphadenitis tissue. Moreover, the expression of CYP24A1 was positively associated with the Ann Arbor stage and the International Prognostic Index in patients with DLBCL, and negatively associated with the clinical response to treatment. Patients >60 years of age were found to have a higher level of CYP24A1. 1,25(OH)2D3 inhibited the proliferation of the Pfeiffer DLBCL cell line and increased the G1 phase population of Pfeiffer cells. Rapamycin (RAPA) in combination with 1,25(OH)2D3 increased the G1 phase distribution of Pfeiffer cells. Furthermore, RAPA blocked the increase of CYP24A1 and vitamin D receptor (VDR) expression induced by 1,25(OH)2D3. 1,25(OH)2D3 induced the formation of autophagosomes, increased the expression of autophagy related protein light chain (LC)3II/LC3I and reduced the expression of the ubiquitin binding protein P62. In addition, 1,25(OH)2D3 decreased the phosphorylation of AKT and mammalian target of RAPA (mTOR), and downstream targets eukaryotic translation imitation factor 4E‑binding protein 1 and ribosomal protein S6 kinase β‑1 in Pfeiffer cells. The results from the present study suggested that CYP24A1 may be a novel prognostic indicator for DLBCL. 1,25(OH)2D3 inhibited proliferation and induced autophagy of Pfeiffer cells. In addition, 1,25(OH)2D3 increased the G1 phase population of Pfeiffer cells. These effects may be mediated by inhibition of the AKT/mTOR/PI3K signaling pathway. RAPA increased the cell cycle arrest induced by 1,25(OH)2D3 by blocking the upregulated expression of CYP24A1 and VDR.
... Studies have demonstrated that mTOR signaling has numerous key regulatory functions in various diseases, including cancer (43-46), infectious diseases (47,48), atherosclerosis, and degenerative and autoimmune diseases (49-51), and has been suggested to be a novel therapeutic target for the treatment of these diseases (43)(44)(45)(46)(47)(48)(49)(50)(51). Other studies have shown that mTOR signaling is also involved in the regulation of multiple aspects of skeletal development (52-54). ...
Previous research indicates that kaempferol (Kae) promotes osteogenesis, but its underlying mechanism of action remains unclear. The present study hypothesized that the osteogenic effects of Kae were mediated through mammalian target of rapamycin (mTOR). To validate this hypothesis, bone marrow mesenchymal stem cells (BMSCs) from ovariectomized (OVX) rats were differentiated into osteoblasts. The bone mineral density and bone microarchitecture of the OVX rats was measured in vivo, while osteogenesis was evaluated in vitro via Alizarin Red S staining and alkaline phosphatase activity measurements in cultured BMSCs. The levels of phosphorylated eukaryotic translation initiation factor 4E‑binding protein 1 (p‑4E/BP1) and phosphorylated ribosomal protein S6 kinase B1 (p‑S6K), and the expression of Runt‑related transcription factor 2 and Osterix, were concurrently quantified by western blot analysis. The data suggested that Kae prevented OVX‑induced osteoporosis in rats by promoting osteoblastogenesis. Furthermore, treatment with Kae in rat BMSCs enhanced mineralization, elevated ALP activity, increased the expression levels of Runx‑2 and Osterix and increased the levels of p‑S6K and decreased the levels of p‑4E/BP1 and, consistent with its ability to promote osteoblast differentiation. In contrast, treatment with rapamycin, an mTOR inhibitor, produced the opposite phenotype. Taken together, these data suggested that the protective effects of Kae in BMSCs and in the OVX rat model resulted from the induction of osteogenesis via mTOR signaling, or at least partially via the regulation of downstream effectors of the mTOR pathway.
... 65 In humans, sirolimus is found to enhance HIV control following liver transplantation 66 and a more general role in HIV control has been suggested. 67 ...
Purpose: To describe the antimicrobial effects of immunosuppressants used for presumed autoimmune uveitis, and to discuss the potential importance of these effects in the context of increasing knowledge of the human microbiomes and their influence on inflammation.
Methods: Literature review
Review of evidence: All immunosuppressants have intrinsic antimicrobial effects; these vary considerably between drugs, and include antibacterial, antiviral and antifungal action. Immunosuppression is known to affect the composition of the gut microbiome, and alterations in microbiome composition are known to affect inflammations including uveitis.
Conclusions: Oral immunosuppressants are assumed to act on presumed autoimmune uveitis by downregulation of, or other interference with, an aberrant immune response. However, their antimicrobial properties are usually forgotten, and in the context of increasing knowledge of the involvement of microbes in the initiation of, and also potentially the perpetuation of, tissue inflammation, these effects may prove to be a fundamental part of their action.
... Homozygosity for the CCR5Δ32 allele leads to loss of expression of CCR5 and has been associated with lower rejection and longterm graft survival in HIV− kidney transplant [125,126]. The MTOR inhibitors also downregulate CCR5 [127] and have been associated with lower HIV DNA levels post-transplant through unclear mechanisms [128]. Ongoing trials are investigating CCR5 blockade and sirolimus in HIV+ recipients (ClinicalTrials.gov ...
Purpose of Review
End-stage organ disease prevalence is increasing among HIV-infected (HIV+) individuals. Trial and registry data confirm that solid organ transplantation (SOT) is efficacious in this population. Optimizing access to transplant and decreasing complications represent active frontiers.
Recent Findings
HIV+ recipients historically experienced 2–4-fold higher rejection. Integrase strand transferase inhibitors (INSTIs) minimize drug interactions and may reduce rejection along with lymphodepleting induction immunosuppression. Hepatitis C virus (HCV) coinfection has been associated with inferior outcomes, yet direct-acting antivirals (DAAs) may mitigate this. Experience in South Africa and the US HIV Organ Policy Equity (HOPE) Act support HIV+ donor to HIV+ recipient (HIV D+/R+) transplantation.
Summary
SOT is the optimal treatment for end-stage organ disease in HIV+ individuals. Recent advances include use of INSTIs and DAAs in transplant recipients; however, strategies to improve access to transplant are needed. HIV D+/R+ transplantation is under investigation and may improve access and provide insights for HIV cure and pathogenesis research.
... In order to overcome some of the limits and side effects of the current treatment regimes, new therapeutic approaches have been investigated for HIV treatment, such as the use of antagonists of CCR5, a receptor involved in the virus entry. In this context, the m-Tor inhibitor rapamycin provides a potential strategy to inhibit HIV, especially in patients with drug resistant HIV strains [6][7][8][9][10]. ...
The pyrimidine nucleus is a versatile core in the development of antiretroviral agents. On this basis, a series of pyrimidine-2,4-diones linked to an isoxazolidine nucleus have been synthesized and tested as nucleoside analogs, endowed with potential anti-HIV (human immunodeficiency virus) activity. Compounds 6a-c, characterized by the presence of an ethereal group at C-3, show HIV reverse transcriptase (RT) inhibitor activity in the nanomolar range as well as HIV-infection inhibitor activity in the low micromolar with no toxicity. In the same context, compound 7b shows only a negligible inhibition of RT HIV.
... In the KEGG pathway enrichment analysis, 'PI3K/AKT signaling pathway' appeared to be the most enriched pathway with the largest number of enriched genes. The PI3K/AKT signaling pathway, including its downstream pathway, mammalian target of rapamycin (mTOR), is well known to be involved in a variety of BPs, and it has been reported that hyperactivation of mTOR has a pathogenetic role in human immunodeficiency virus infection (44)(45)(46). Due to the important role of the AKT pathway in cellular metabolism, growth and division, apoptosis suppression and angiogenesis, the regulation of the AKT signaling may represent a valuable therapeutic strategy. For this reason, AKT inhibitors have become the hotspots of research in a number of clinical diseases (47), and dual PI3K/mTOR inhibitors, including PF-04691502 and NVP-BEZ235, may have important therapeutic applications in cancer (48,49). ...
Tuberculosis (TB) is a globally prevalent infectious disease. The mechanisms of latent TB infection (LTBI) remain to be fully elucidated and may provide novel approaches for diagnosis. As therapeutic targets and molecular diagnostic markers, microRNAs (miRs) have been studied and utilized in various diseases. In the present study, the differentially expressed miRs (DEMs) in LTBI were screened and analyzed to determine the underlying mechanisms and identify potential biomarkers, thereby contributing to the diagnosis of LTBI. The GSE25435 and GSE29190 datasets from Gene Expression Omnibus were selected for analysis. The 2 datasets were analyzed individually using the Bioconductor package to screen the DEMs with specific cut-off criteria [P<0.01 and |log (fold change)|≥1]. Target gene prediction and interaction network construction were performed using Targetscan, the Search Tool for the Retrieval of Interacting Genes and Proteins and Cytoscape individually, and were merged using the latter tool. The hub genes were finally selected based on their degree of connectivity (DC). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed using the KEGG and GENCLIP. A total of 144 DEMs were identified from the 2 datasets. By exploring the overlapping miRs in the two datasets, Homo sapiens (hsa)-miR-29a and hsa-miR-15b were identified to be decreased, while hsa-miR-576-5p, hsa-miR-500 and hsa-miR-155 were identified to be upregulated. hsa-miR-500a-3p and hsa-miR-29a-3p, as well as 4 genes, namely cell division cycle (CDC)42, actin α1, skeletal muscle (ACTA1), phosphatase and tensin homolog (PTEN) and fos proto-oncogene (FOS), were selected as the key factors in this regulatory network. A total of 9 signaling pathways, including phosphoinositide-3 kinase (PI3K)/AKT and 11 biological processes, were identified to be associated with LTBI. In conclusion, the present analysis identified hsa-miR-500a-3p and hsa-miR-29a-3p, as well as CDC42, ACTA1, PTEN and FOS, as the most promising biomarkers and therapeutic candidates for LTBI. The PI3K/AKT signaling pathway is the key signaling pathway implicated in LTBI, and an in-depth investigation of the efficiency of PI3K/AKT signaling inhibitors may be used to prevent a chronic state of infection in LTBI.
... These results agree with previous studies suggesting that activation of PI3K/Akt/mTOR enhances the survival of MSCs under H/SD conditions (32). Currently, inhibition of the PI3K/Akt/mTOR pathway is used as a therapeutic strategy against various diseases, including human immunodeficiency virus and cancer (33)(34)(35)(36). The inhibition of PI3K/Akt/mTOR signaling resulted in increased apoptosis of MSCs. ...
Mesenchymal stem cells (MSCs) have exhibited great potential in the therapy of cardiovascular disease. However, the application of MSCs is hampered by apoptosis, which reduces the number of cells in the host cardiac microenvironment. Ulinastatin (UTI), a broad-spectrum protease inhibitor that can be purified from human urine, has attracted attention for its protective effects through its immunomodulatory and anti-inflammatory properties. The present study aimed to evaluate the effects of UTI on serum deprivation-induced apoptosis of MSCs and investigate its molecular mechanisms. Cell viability was determined by the MTT assay. Apoptosis was assessed by flow cytometric analysis with Annexin V/propidium iodide staining. The protein levels of cleaved caspase-3, B-cell lymphoma-2 (Bcl-2) family proteins, total-Akt and phospho-Akt were evaluated by western blot. The results of the present study demonstrated that UTI exhibited a protective effect in serum deprived MSCs, as indicated by increased cell viability, and a reduction in the rate of apoptosis and caspase-3 activation. In addition, treatment with UTI significantly decreased the expression levels of Bcl-2, Bcl-extra large and Bcl-associated X protein. Furthermore, activation of the Akt signaling pathway was involved in the UTI-induced anti-apoptotic effects. The present findings indicated that UTI is able to promote the survival of MSCs under serum deprivation conditions. The present study may be helpful in improving the therapeutic efficacy of MSC transplantation used to cure chronic ischemic heart disease.
... However, dysregulated autophagy may induce apoptosis and may also cause certain diseases. Several studies demonstrated that the upregulation of autophagy has beneficial effects in some diseases, including AIDS, autoimmune diseases and neurodegenerative diseases (50)(51)(52)(53)(54); however, its role in cancer is controversial (55)(56)(57)(58). The present study revealed that BTXA promoted protective autophagy in HDMECs in an in vitro model of IRI. ...
Botulinum toxin type A (BTXA) has been reported to increase the survival of ischemic skin flaps; however, the exact mechanism underlying this effect remains unclear and needs to be further established. The present study aimed to elucidate whether autophagy caused by BTXA functions as a protection mechanism and to identify the mechanisms of its regulation by BTXA in human dermal microvascular endothelial cells (HDMECs) subjected to hypoxia/reoxygenation (H/R)-induced injury. HDMECs were harvested from the upper eyelid tissues of female blepharoplasty patients. HDMECs were exposed to BTXA treatment for 12 h and then subjected to hypoxia for 8 h, followed by reoxygenation for 24 h. Chloroquine diphosphate salt (CQ) was used as an autophagy inhibitor. H/R led to extreme injury to the HDMECs as indicated by the rise in the apoptosis rate, which was significantly attenuated by BTXA pretreatment. The outcomes demonstrated that H/R caused autophagy, as evidenced by a higher type II/type I ratio of light chain 3 (LC3), increased expression of Beclin-1 and increased autophagosome formation. BTXA enhanced autophagy and attenuated apoptosis in a dose-dependent manner, whereas CQ attenuated the BTXA antiapoptotic effects and inhibited the formation of autopha-golysosomes, which caused clustering of the LC3-II in cells. In conclusion, autophagy promoted by BTXA serves as a potential protective effect on ischemia/reperfusion injury.
... Knowing this, we decided to initiate sirolimus no earlier than POD 14. One of the basic principles of and expectations about the early implementation of sirolimus was the hope of better kidney protection [9,10]. However, in the group of patients who were analyzed in this study, there was a significant deterioration in renal function. ...
Background
Sirolimus, a mechanistic target of sirolimus inhibitor, is an immunosuppression medication for patients undergoing heart and abdominal transplantation. Sirolimus-based immunosuppression administered de novo post-lung transplantation is associated with bronchial anastomosis healing-related complications. We hypothesized that sirolimus administration within the first postoperative month in selected lung transplant recipients is safe and may be associated with favorable short-term and long-term outcomes due to its anti-proliferative properties and minimal adverse side effects.
Material/Methods
Thirteen patients (13.3%; mean age, 46.8±11.9 years) received early sirolimus-based immunosuppression along with cyclosporine and prednisone; 10 patients received single-lung transplantation, 3 received double-lung transplantation, and all received induction immunosuppressants. Patients received early sirolimus-based immunosuppression after an uncomplicated postoperative course and detailed bronchoscopic assessment.
Results
Sirolimus was begun on a mean of 20.6±4.7 days postoperatively (range, 14–32 days). The in-hospital and 30-day mortality rate was 0%. At long-term follow-up, 5 patients died (due to bacterial infection in 4 patients and pneumocystis jiroveci pneumonia in 1 patient). The mean overall survival was 4.4±2.53 (range, 0.8–10.0) years, 1-year survival was 92%, and 5-year survival was 62%. In 4 patients (30.8%), sirolimus was stopped due to infection in 3 patients and re-transplantation in 1 patient. Only one of the 13 patients developed bronchiolitis obliterans syndrome. In patients still taking sirolimus, renal function, systolic blood pressure, and lipid profile were within normal ranges; however, these patients required statin therapy.
Conclusions
In selected lung transplant recipients, early sirolimus-based immunosuppression is safe and associated with beneficial short-term and long-term outcomes.
... URMC-099 assisted nuclear translocation of TFEB and thus overcomes HIV-1 Nef-mediated inhibition of autophagy [35]. Several autophagy inducers including rapamycin have been shown to inhibit HIV-1 infection by enhancing autophagosome and lysosome fusion, which ultimately inhibit HIV-1 infection [64][65][66]. This is clearly seen with rapamycin, clonidine and HBC, and a more significant inhibition is observed with DMC which coincides with lower LC3BII/I ratio suggesting increased autophagosome-lysosome fusion. ...
Aim:
Pharmacologic agents that affect autophagy were tested for their abilities to enhance macrophage nanoformulated antiretroviral drug (ARV) depots and its slow release.
Methods:
These agents included URMC-099, rapamycin, metformin, desmethylclomipramine, 2-hydroxy-β-cyclodextrin (HBC) and clonidine. Each was administered with nanoformulated atazanavir (ATV) nanoparticles to human monocyte-derived macrophages. ARV retention, antiretroviral activity and nanocrystal autophagosomal formation were evaluated.
Results:
URMC-099, HBC and clonidine retained ATV. HBC, URMC-099 and rapamycin improved intracellular ATV retention. URMC-099 proved superior among the group in affecting antiretroviral activities.
Conclusion:
Autophagy inducing agents, notably URMC-099, facilitate nanoformulated ARV depots and lead to sustained release and improved antiretroviral responses. As such, they may be considered for development as part of long acting antiretroviral treatment regimens.
... In this study, we found that curcumin exerted an inhibitory effect on Akt/mTOR phosphorylation. The mTOR pathway, in addition to cancer, is also implicated in the pathogenesis of autoimmune (22,23) and infectious diseases (24)(25)(26). Thus, we hypothesized that curcumin may also have therapeutic potential in autoimmune and infectious diseases, such as HIV infection. ...
Curcumin is a natural compound that appears to be promising for clinical application, as it has been shown in in vitro and in vivo studies to exert antitumor effects by modulating multiple signaling cellular pathways. In the present study, the antitumor effects of curcumin and its mechanism of action were investigated in cultured breast cancer cells. The MTT assay was used to determine the effect of curcumin on breast cancer cell proliferation, flow cytometry was used to detect alterations of the cell cycle, and western blot analysis was used to determine the expression of signaling molecules involved in the cell cycle, proliferation and apoptosis. The results revealed that curcumin significantly inhibited the proliferation of various breast cancer cell lines, such as T47D, MCF7, MDA-MB-231 and MDA-MB-468, with an IC50 at the micromolar level, indicating the potent antitumor activity of curcumin. In-depth study of its mechanism of action revealed that curcumin induced cell cycle arrest at the G2/M phase and decreased the expression of the CDC25 and CDC2 proteins, while increasing the expression of P21. In addition, curcumin inhibited the phosphorylation of protein kinase B (Akt)/mammalian target of rapamycin (mTOR), decreased B-cell lymphoma 2 (BCL2) and promoted BCL-2-associated X protein (BAX) and cleavage of caspase 3, subsequently inducing apoptosis of breast cancer cells. In conclusion, curcumin inhibited the proliferation of breast cancer cells and induced G2/M phase cell cycle arrest and apoptosis, which may be associated with the decrease of CDC25 and CDC2 and increase of P21 protein levels, as well as inhibition of the phosphorylation of Akt/mTOR and induction of the mitochondrial apoptotic pathway. The findings of the present study may provide a basis for the further study of curcumin in the treatment of breast cancer.
... Increasing body of data suggests that alterations in the PI3K/Akt/ mTOR pathway may result in enhanced susceptibility to autoimmunity [1,2]. Beside regulating immune responses, the PI3K/Akt/mTOR has also been proven to be involved in several other functions including, chemoresistance, aging and host response to viral infections [3][4][5][6][7][8]. ...
The PI3K/AKT/mTOR pathway is an intracellular signalling pathway that regulates cell activation. proliferation, metabolism and apoptosis. Increasing body of data suggests that alterations in the PI3K/AKT/mTOR pathway may result in an enhanced susceptibility to autoimmunity. Multiple Sclerosis (MS) is one of the most common chronic inflammatory diseases of the central nervous system leading to demyelination and neurodegeneration.
In the current study, we have firstly evaluated in silico the involvement of the mTOR network on the generation and progression of MS and on oligodendrocyte function, making use of currently available whole-genome transcriptomic data. Then, the data generated in silico were subjected to an ex-vivo evaluation. To this aim, the involvement of mTOR was validated on a well-known animal model of MS and in vitro on Th17 cells.
Our data indicate that there is a significant involvement of the mTOR network in the etiopathogenesis of MS and that Rapamycin treatment may represent a useful therapeutic approach in this clinical setting. On the other hand, our data showed that a significant involvement of the mTOR network could be observed only in the early phases of oligodendrocyte maturation, but not in the maturation process of adult oligodendrocytes and in the process of remyelination following demyelinating injury.
Overall, our study suggests that targeting the PI3K/mTOR pathway, although it may not be a useful therapeutic approach to promote remyelination in MS patients, it can be exploited to exert immunomodulation, preventing/delaying relapses, and to treat MS patients in order to slow down the progression of disability.
... 41 Interestingly, it is this off-target effect on mTOR that has also been shown to play a role in the treatment of HIV infection. 42 Additional pathways implicated in the literature with NFV include oxidative stress mechanisms, 26,43 decreased angiogenesis, 14,44 and cell cycle arrest. 14,26,45 In future clinical trials, the inclusion of NFV in combination, rather than as a single agent, would provide additional benefits for breast cancer 35 and with bortezomib for myeloma. ...
Purpose
Refractory pediatric leukemia remains one of the leading causes of death in children. Intensification of current chemotherapy regimens to improve the outcome in these children is often limited by the effects of drug resistance and cumulative toxicity. Hence, the search for newer agents and novel therapeutic approaches are urgently needed to formulate the next-generation early-phase clinical trials for these patients.
Materials and methods
A comprehensive library of antimicrobials, including eight HIV protease inhibitors (nelfinavir [NFV], saquinavir, indinavir, ritonavir, amprenavir, atazanavir, lopinavir, and darunavir), was tested against a panel of pediatric leukemia cells by in vitro growth inhibition studies. Detailed target modulation studies were carried out by Western blot analyses. In addition, drug synergy experiments with conventional and novel antitumor agents were completed to identify effective treatment regimens for future clinical trials.
Results
Several of the HIV protease inhibitors showed cytotoxicity at physiologically relevant concentrations (half-maximal inhibitory concentration values ranging from 1–24 µM). In particular, NFV was found to exhibit the most potent antileukemic properties across all cell lines tested. Mechanistic studies show that NFV leads to the induction of autophagy and apoptosis possibly through the induction of endoplasmic reticulum stress. Furthermore, interference with cell signaling pathways, including Akt and mTOR, was also noted. Finally, drug combination studies have identified agents with potential for synergy with NFV in its antileukemic activity. These include JQ1 (BET inhibitor), AT101 (Bcl-2 family inhibitor), and sunitinib (TK inhibitor).
Conclusion
Here, we show data demonstrating the potential of a previously unexplored group of drugs to address an unmet therapeutic need in pediatric oncology. The data presented provide preclinical supportive evidence and rationale for future studies of these agents for refractory leukemia in children.
... Phosphorylation of IRS1, which is known to antagonize IRS signaling, is elevated in animal models of obesity and in muscle from type 2 diabetic patients. Insulin resistance is the hallmark for both, obesity and type 2 diabetes [79,84,85]. ...
... IR-induced ROS production leads to mitochondrial dysfunction and endoplasmic reticulum stress, resulting in induction of autophagy (10). IR-induced autophagy involves the mTOR pathway via activation of PI3K and AKT, and a similar strategy to target mTOR with pharmacological inhibitors such as rapamycin (11,44) has been applied to radiation therapy (10). We did not see any additive effect of MnTnHex-2-PyP on IR-induced autophagy, which was determined by LC3 expression (data not shown). ...
Aims:
Cationic manganese (Mn)-substituted N-pyridylporphyrin-based potent mimics of the family of superoxide dismutases (SODs) protect normal tissues from injury related to ionizing radiation (IR) by reducing levels of reactive oxygen and nitrogen species (ROS/RNS). Furthermore, Mn-porphyrins have demonstrated antitumor and radiosensitizing effects on cancer cells by promoting IR-induced tumor vasculature damage and apoptotic processes. In this study, we explored the underlying mechanisms of Mn-porphyrin-mediated tumor radiosensitization using murine mammary carcinoma 4T1 and melanoma B16 cells in vitro and in vivo.
Results:
Combination treatment with MnTnHex-2-PyP and IR substantially reduced cell viability, clonogenic cell survival, and DNA damage repair and synergistically increased IR-induced apoptosis of 4T1 and B16 cells. MnTnHex-2-PyP in combination with IR caused a significant delay in growth of 4T1 and B16 xenograft tumors. MnTnHex-2-PyP dose-dependently enhanced IR-mediated production of H2O2-derived species, but not superoxide. Catalase overexpression reversed MnTnHex-2-PyP-enhanced ROS production and apoptosis. Demonstrated suppression of phosphorylation of several mitogen-activated protein (MAP) kinases and activation of NF-?B by MnTnHex-2-PyP/IR, which presumably inhibited activation of the antiapoptotic pathway, are in agreement with our other data on the apoptosis of cancer cells. Innovation and Conclusions: MnTnHex-2-PyP exerted a radiosensitizing effect on 4T1 and B16 tumor models in vitro and in vivo via pro-oxidative actions and therefore bears a large therapeutic potential. When combined with IR, it attenuated DNA damage repair and triggered a shift from prosurvival pathways to apoptotic cell death, likely due to increased ROS production and disturbed cellular redox balance, acting at the level of nuclear factor ?B (NF-?B). Antioxid. Redox Signal. 00, 000-000.
... Interestingly, HIV-1 is unable to maintain mTORC1 activation in the absence of nutrients (amino acids and glucose), but is capable of redistributing mTOR-associated late endosomes/lysosomes to the cell periphery through a mechanism reliant on the small Rag GTPases A and B [149] (Figure 2). Finally, drugs that modify the mTORC1 signaling pathway also alter HIV-1 replication [150][151][152]. ...
The mammalian target of rapamycin (mTOR) is a central regulator of gene expression, translation and various metabolic processes. Multiple extracellular (growth factors) and intracellular (energy status) molecular signals as well as a variety of stressors are integrated into the mTOR pathway. Viral infection is a significant stress that can activate, reduce or even suppress the mTOR signaling pathway. Consequently, viruses have evolved a plethora of different mechanisms to attack and co-opt the mTOR pathway in order to make the host cell a hospitable environment for replication. A more comprehensive knowledge of different viral interactions may provide fruitful targets for new antiviral drugs.
... Of particular relevance in this context is also the demonstration that the mTOR inhibitor, rapamycin, inhibits progression of hepatic fibrosis in rat model [28], because treatment with this drug has been shown to delay time to progression of liver fibrosis in HCV-transplanted recipients [29]; in addition it seems to favor the clinical course of HCV infection through anti-HCV action [30]. It has been further demonstrated that pathways downstream of mTOR activation, including mTOR complex 1 (mTORC1) and p70S kinases, could be involved in hepatic fibrosis and could represent a suitable therapeutic target [31]. ...
Fibrosis represents a response to chronic injury, aimed at maintaining organ integrity. Hepatic fibrosis is mainly related to chronic viral hepatitis B or C (HBV or HCV), alcoholic and nonalcoholic steatohepatitis (NASH), and biliary diseases. A deep understanding of the cellular and molecular mechanisms underlying liver fibrosis has enabled the development of 'pathogenetic tailored' therapeutic interventions. However, effective drugs to prevent or revert hepatic fibrosis are still lacking. In this review, we discuss the cellular populations and the molecular pathways involved in liver fibrogenesis as well as the novel approaches currently being tested in clinical trials.
... First, sirolimus (rapamycin, Rapamune), a compound that strongly activates autophagy through inhibition of mTORC1 pathway, enhances the efficacy of HIV treatment. Sirolimus represses HIV-1 replication in vitro through different mechanisms including, but not limited to, the downregulation of CCR5 [321,322]. Although this was very surprising due to the known immunosuppressive action of sirolimus, the rapamycin effects might differ depending on the cell type targeted. ...
A consensus is now growing on the fact that autophagy can behave as an antiviral mechanism against incoming pathogens. Therefore, some pathogens have evolved to counteract or benefit from the cellular autophagy machinery. The Human Immunodeficiency Virus (HIV), like many viruses, manipulates autophagy to favor its replication. In particular, HIV-1 envelope (Env) plays an important role in modulating autophagy in CD4 + T cells and phagocytic cells. Env-mediated autophagy is a cell-type dependent mechanism activated in bystander CD4 + T cells but totally inhibited during their productive infection. In both infected myeloid dendritic cells and macrophages, the autophagy flux is progressively shutdown. The modulation of autophagy by HIV in these cell types could be responsible for the onset of HIV-mediated immunopathogenesis and contribute to viral spread. The former effect is responsible for apoptosis of bystander CD4 + T cells and the latter correlates with a viral escape strategy favoring viral replication and transmission by counteracting autophagy-mediated antiviral immunity. Furthermore, HIV-1 can infect different cell types of the central nervous system such as the microglia and, in a restrictive manner, the astrocytes and the neural precursors for which infection has also been correlated with modulation of autophagy. The aim of this review is to provide an overview on the intricate and conflicting relationships that intimately link HIV-1 and autophagy in these different cell types.
Histidine triad nucleotide‑binding protein (HINT) belongs to the histidine triad protein family. Recent studies have demonstrated that HINT1 and HINT2 both play a pivotal role in cancer growth. However, the functions of HINT3 in various types of cancer, including breast cancer (BRCA), have not yet been fully elucidated. In the present study, the role of HINT3 in BRCA was investigated. Based on The Cancer Genome Atlas and reverse transcription‑quantitative PCR analyses, HINT3 was found to be decreased in BRCA tissues. In vitro, HINT3 knockdown promoted the proliferation and colony formation of, and 5‑ethynyl‑2'‑deoxyuridine incorporation in MCF‑7 and MDA‑MB‑231 BRCA cells. By contrast, HINT3 overexpression suppressed DNA synthesis and the proliferation of both cell lines. Apoptosis was also found to be modulated by HINT3. In vivo, HINT3 ectopic expression attenuated the tumorigenesis of MDA‑MB‑231 and MCF‑7 cells in a mouse tumor xenograft model. Furthermore, HINT3 silencing or overexpression also enhanced or inhibited, respectively, the migratory capacity of the MCF‑7 and MDA‑MB‑231 cells. Finally, HINT3 upregulated phosphatase and tensin homolog (PTEN) at the transcriptional level, which resulted in the inactivation of AKT/mammalian target of rapamycin (mTOR) signaling both in vitro and in vivo. Taken together, the present study demonstrates that HINT3 inhibits the activation of the PTEN/AKT/mTOR signaling pathway, and suppresses the proliferation, growth, migration and tumor development of MCF‑7 and MDA‑MB‑231 BRCA cells.
The presence of latent human immunodeficiency virus 1 (HIV-1) in quiescent memory CD4+ T cells represents a major barrier to viral eradication. Proliferation of memory CD4+ T cells is the primary mechanism that leads to persistence of the latent reservoir, despite effective antiretroviral therapy (ART). Memory CD4+ T cells are long-lived and can proliferate through two mechanisms: homeostatic proliferation via γc-cytokine stimulation or antigen-driven proliferation. Therefore, therapeutic modalities that perturb homeostatic and antigen-driven proliferation, combined with ART, represent promising strategies to reduce the latent reservoir. In this study, we investigated a library of FDA-approved oncology drugs to determine their ability to inhibit homeostatic and/or antigen-driven proliferation. We confirmed potential hits by evaluating their effects on proliferation in memory CD4+ T cells from people living with HIV-1 on ART (PLWH) and interrogated downstream signaling of γc-cytokine stimulation. We found that dasatinib and ponatinib, tyrosine kinase inhibitors, and trametinib, MEK inhibitor, reduced both homeostatic and antigen-driven proliferation by 65%, with a reduction in viability less than 45%, ex vivo. In memory CD4+ T cells from PLWH, only dasatinib restricted both homeostatic and antigen-driven proliferation and prevented spontaneous rebound, consistent with promoting a smaller reservoir size. We show that dasatinib restricts IL-7 induced proliferation through STAT5 phosphorylation inhibition. Our results establish that the anti-cancer agent, dasatinib, is an exciting candidate to be used as an anti-proliferative drug in a clinical trial since it efficiently blocks proliferation and is well tolerated in patients with chronic myeloid leukemia (CML).
These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the management of transplantation in HIV infected individuals. Transplantation has become the standard of care for patients with HIV and end stage kidney or liver disease. Although less data exist for thoracic organ and pancreas transplantation, it is likely that transplantation is also safe and effective for these recipients as well. Despite what is typically a transient decline in CD4+ T lymphocytes, HIV remains well‐controlled and infection risks are similar to those of HIV uninfected transplant recipients. The availability of effective directly active antivirals for the treatment of Hepatitis C is likely to improve outcomes in HIV and HCV co‐infected individuals, a population previously noted to have decreased survival. Drug interactions remain an important consideration and integrase inhibitor based regimens are preferred due to the absence of interactions with calcineurin and mTOR inhibitors. Additionally, despite the use of more potent immunosuppression, rejection rates exceed those found in HIV uninfected recipients. Ongoing research evaluating HIV positive organ donors may provide support for utilizing these donors for HIV positive patients in need of transplantation.
This article is protected by copyright. All rights reserved.
Neuroblastoma (NB) is the most predominant extracranial solid tumor of infancy in the world. However, current chemotherapy has limited efficacy for more advanced stages of NB due to acquired chemoresistance or acute toxicity in NB patients. Therefore, effective novel anti-NB drugs are desperately needed. The present study aimed to investigate the effects of dehydroeffusol (DHE), a phenanthrene isolated from J. effuses, on NB cells and its underlying mechanism. The results showed that DHE treatment effectively inhibited NB cell viability in a dose-dependent manner. Moreover, DHE treatment suppressed the epithelial-mesenchymal transition (EMT) process in NB cells by promoting the expression of E-cadherin (E-cad) and restraining the expressions of N-cadherin (N-cad) and vimentin. Also, the invasive capacity and expression of MMP-2 and MMP-9 in NB cells were inhibited by DHE. Furthermore, DHE suppressed the hedgehog (Hh) and the protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathways in NB cells. In conclusion, DHE effectively inhibited the viability and EMT through inactivating the Hh and the Akt/mTOR signaling pathways in NB cells, providing a novel evidence that DHE may be a potential anti-NB drug candidate.
In this study, we investigated the effect of the dual phosphatidylinositol 3-kinase/mechanistic target of rapamycin (PI3K/MTOR) inhibitor dactolisib (NVP-BEZ235), the PI3K/ MTOR/bromodomain-containing protein 4 (BRD4) inhibitor SF2523 and the BET inhibitor JQ1 on the productive infection of primary macrophages with human immunodeficiency type-1 (HIV). These inhibitors did not alter the initial susceptibility of macrophages to HIV infection. However, dactolisib, JQ1 and SF2523 all decreased HIV replication in macrophages in a dose dependent manner via degradation of intracellular HIV through autophagy. Macrophages treated with dactolisib, JQ1 or SF2523 displayed an increase in LC3B lipidation combined with SQSTM1 degradation without inducing increased cell death. LC3B-II levels were further increased in the presence of pepstatin A suggesting that these inhibitors induce autophagic flux. RNA interference forATG5andATG7, and pharmacological inhibitors of autophagosome-lysosome fusion, and of lysosomal hydrolases, all blocked the inhibition of HIV. Thus, we demonstrate that the mechanism of PI3K/MTOR and PI3K/MTOR/BRD4 inhibitor suppression of HIV requires the formation of autophagosomes, as well as their subsequent maturation into autolysosomes. These data provide further evidence in support of a role for autophagy in the control of HIV infection and open new avenues for the use of this class of drugs in HIV therapy.
Antiretroviral drug (ARV) metabolism is linked largely to hepatic cytochrome P450 (CYP) activity. One ARV drug class known to be metabolized by intestinal and hepatic CYP3A are the protease inhibitors (PI). Plasma drug concentrations in are boosted by CYP3A inhibitors such as cobisistat and ritonavir (RTV). Studies of such drug-drug interactions are limited as the enzyme pathways are human specific. While immune-deficient mice reconstituted with human cells are an excellent model to study ARVs during human immunodeficiency virus type 1 (HIV-1) infection, they cannot reflect human drug metabolism. Thus, we created a mouse strain with the human PXR, CAR and CYP3A4/7 genes on a NOD.Cg-PrkdcsaidIl2rgtm1Sug/JicTac background (hCYP3A-NOG) and used them to evaluate the impact of human CYP3A metabolism on ARV pharmacokinetics. In proof of concept studies we used nanoformulated atazanavir (nanoATV) with or without RTV. NOG and hCYP3A-NOG mice were treated weekly with 50 mg/kg nanoATV alone or boosted with nanoRTV (nanoATV/r). Plasma was collected weekly and liver at 28 days post-treatment. Plasma and liver ATV concentrations in nanoATV/r-treated hCYP3A-NOG mice were 2- to 4-fold higher than in replicate NOG mice. RTV enhanced plasma and liver ATV concentrations 3-fold in hCYP3A-NOG mice and 1.7-fold in NOG mice. The results indicate that human CYP3A-mediated drug metabolism is reduced compared to mouse and that RTV differentially affects human gene activity. These differences can affect responses to PIs in humanized mouse models of HIV-1 infection. Importantly, hCYP3A-NOG mice reconstituted with human immune cells can be used for bench to bedside translation.
HIV-infected persons who achieve undetectable viral loads on antiretroviral therapy currently have near-normal lifespans. Liver disease is a major cause of non-AIDS-related deaths, and as a result of longer survival, the prevalence of end-stage renal disease in HIV is increasing. HIV-infected persons undergoing organ transplantation generally achieve comparable patient and graft survival rates compared to their HIV-uninfected counterparts, despite a nearly threefold increased risk of acute rejection. However, the ongoing shortage of suitable organs can limit transplantation as an option, and patients with HIV have higher waitlist mortality than others. One way to solve this problem would be to expand the donor pool to include HIV-infected individuals. The results of a South Africa study involving 27 HIV-to-HIV kidney transplants showed promise, with 3 and 5-year patient and graft survival rates similar to those of those of their HIV-uninfected counterparts. Similarly, individual cases of HIV-to-HIV liver transplantation from the United Kingdom and Switzerland have also shown good results. In the United States, HIV-to-HIV kidney and liver transplants are currently permitted only under a research protocol. Nevertheless, areas of ambiguity exist, including streamlining organ allocation practices, optimizing HIV-infected donor and recipient selection, managing donor-derived transmission of a resistant HIV strain, determining optimal immunosuppressive and antiretroviral regimens, and elucidating the incidence of rejection in HIV-to-HIV solid organ transplant recipients.
Appropriate post-transplant immunosuppressive regimens that avoid acute rejection, while reducing risk of viral reactivation, have been sought, but remain a chimera. Recent evidence suggesting potential regulatory and antiviral effects of mammalian target of rapamycin inhibitors (mTORi) is of great interest. Although the concept of an immunosuppressive drug with antiviral properties is not new, little effort has been made to put the evidence together to assess the management of immunosuppressive therapy in the presence of a viral infection. This review was developed to gather the evidence on antiviral activity of the mTORi against the viruses that most commonly reactivate in adult solid organ recipients: cytomegalovirus (CMV), polyomavirus, Epstein-Barr virus (EBV), human herpesvirus 8 (HHV8), and hepatitis C virus (HCV). A rapid review methodology and evaluation of quality and consistency of evidence based on the GRADE system was used. The existing literature was variable in nature, although indicating a potential advantage of mTORi in CMV, polyomavirus, and HHV8 infection, and a most doubtful relation with EBV and HCV infection. Several recommendations about the management of these infections are presented that can change certain current patterns of immunosuppression and help to improve the prognosis of the direct and indirect effects of viral infection in solid organ recipients. This article is protected by copyright. All rights reserved.
Simian immunodeficiency viruses (SIVs) are a large group of lentiviruses that naturally infect more than 40 African nonhuman primate (NHP) species. SIV prevalence in the wild ranges from 2% to more than 80% in different species. The simian lentiviruses form one of the five serogroups of the Lentiviridae genus, consisting of three species: human immunodeficiency virus 1 (HIV-1), human immunodeficiency virus 2 (HIV-2), and SIV. The SIVs from naturally infected NHPs of African origin hosts are designated by a three-letter abbreviation of the host primate species. In addition, the number of SIVs naturally infecting different African NHP species is high. There are major intrinsic limitations to the development of animal models in different species of African NHP hosts: numerous SIVs are only known from sequences, therefore they cannot be used in pathogenesis/treatment studies; numerous African NHPs that are natural hosts of SIVs are extremely endangered which generally precludes invasive studies in these hosts; and there are no currently available colonies for most of the African NHPs.
Human Immunodeficiency Virus type 1 (HIV-1) is a retrovirus that targets cells from the immune system such as the CD4 T lymphocytes, the macrophages and the dendritic cells (DCs). Although these host cells possess various defense mechanisms to fight this infection, HIV-1 has evolved multiple strategies to counteract them. For the past ten years, researchers have been focused on the identification of HIV-1 restriction factors and their mode of action for the development of new therapeutic strategies [1].
Microbicides are products that can be applied to vaginal or rectal mucosa with the intent of preventing, or at least significantly reducing, the transmission of sexually transmitted infections, including HIV-1. The past 2 or 3 years of microbicide research have generated several disappointments. Large, phase 2B/3 studies failed to demonstrate product efficacy, were stopped prematurely for futility, and in the worst-case scenario possibly demonstrated microbicide-induced harm. The most recently completed efficacy study (HPTN-035) did not reach statistical significance, but did show that use of PRO-2000 was associated with a 30% reduction in HIV acquisition. Current research focuses on much more potent targeted therapy, including reverse transcriptase inhibitors and CCR5 antagonists. Ongoing challenges include optimizing the identification of safety signals in phase 1/2 studies, defining a rationale for advancing products into efficacy studies, and identifying populations with adequate HIV seroincidence rates for these studies.
The number of HIV-infected patients receiving orthotopic liver transplantation (OLTX) is increasing. One major challenge is the severe drug-drug interactions between immunosuppressive drugs such as tacrolimus and ritonavir-boosted HIV-1 protease inhibitors (PIs). The introduction of raltegravir, which is not metabolized by the cytochrome system, may allow concomitant treatment without dose adaptation.
We conducted a retrospective analysis of HIV-1-infected patients receiving tacrolimus concomitantly with different HIV therapies, including 12 h pharmacokinetic assessment of drug levels.
Three OLTX patients received a ritonavir-boosted PI therapy when tacrolimus was added at very low doses of 0.06, 0.03 and 0.08 mg daily. Median tacrolimus blood levels were 6.6, 3.0 and 7.9 ng/mL over a follow-up period of 8, 22 and 33 months, respectively. In two other patients (one after OLTX and one with Crohn's disease), a raltegravir-based HIV therapy was started while patients received 1 or 2 mg of tacrolimus twice daily. No tacrolimus dose adjustment was necessary and drug levels remained unchanged.
Decreasing the dose of tacrolimus to 0.03-0.08 mg daily in patients with concomitant boosted PI therapy resulted in stable tacrolimus blood levels without alteration of PI drug levels. Concomitant use of raltegravir and tacrolimus revealed no clinically relevant drug interaction.
To review the pharmacology, efficacy, safety, and resistance profiles of the integrase inhibitors raltegravir and elvitegravir.
A search of PubMed was conducted (2000-August 2009) using the following key words: raltegravir, MK-0518, elvitegravir, and GS-9137. Articles were evaluated for content and bibliographies were reviewed. Data available exclusively in abstracts from major infectious diseases and HIV conferences were also evaluated for inclusion.
Studies included were in vitro investigations; Phase 1, 2, and 3 clinical trials; retrospective analyses including case reports; and pharmacokinetic and pharmacodynamic evaluations.
Raltegravir is currently approved by the Food and Drug Administration for the management of HIV-1 infection in treatment-naïve or-experienced adults as part of an optimized combination regimen. When combined with other active agents, it has demonstrated similar virologic efficacy after 96 weeks to the combination of efavirenz, tenofovir, and emtricitabine in treatment-naïve patients. Unlike many antiretrovirals, raltegravir does not enter cytochrome P450 metabolism and instead undergoes glucuronidation. Elvitegravir is in the late stages of clinical development. A Phase 2 study has demonstrated virologic efficacy in treatment-experienced patients comparable to protease inhibitor-based regimens after 24 weeks. Boosting of elvitegravir through inhibition of CYP3A4 metabolism has been investigated and suggests a pharmacokinetic profile conducive to once-daily-dosing. Phase 2 and 3 clinical trials evaluating boosted elvitegravir are in process. The Phase 2 trial combines elvitegravir with a non-ritonavir boosting agent plus tenofovir/emtricitabine given once daily as a "quad-pill" formulation. The Phase 3 trial compares once-daily ritonavir-boosted elvitegravir with twice-daily raltegravir, each given with an optimized background regimen. Both integrase inhibitors are well tolerated and raltegravir has few drug-drug interactions. Resistance mutations have been identified in patients experiencing virologic failure and cross resistance between raltegravir and elvitegravir has been confirmed.
The integrase inhibitors provide a novel target for antiretroviral therapy and provide an option for patients harboring resistance to other antiretrovirals.
Sustained inhibition of HIV-1, the goal of antiretroviral therapy, is often impeded by the emergence of viral drug resistance. For patients infected with HIV-1 resistant to conventional drugs from the viral reverse transcriptase and protease inhibitor classes, the recently approved entry and integration inhibitors effectively suppress HIV-1 and offer additional therapeutic options. Entry inhibitors are particularly attractive because, unlike conventional antiretrovirals, they target HIV-1 extracellularly, thereby sparing cells from both viral- and drug-induced toxicities. The fusion inhibitor enfuvirtide and the CCR5 antagonist maraviroc are the first entry inhibitors licensed for patients with drug-resistant HIV-1, with maraviroc restricted to those infected with CCR5-tropic HIV-1 (R5 HIV-1) only. Vicriviroc (another CCR5 antagonist) is in Phase III clinical trials, whereas the CCR5 antibodies PRO 140 and HGS 004 are in early stages of clinical development. Potent antiviral synergy between maraviroc and CCR5 antibodies, coupled with distinct patterns of resistance, suggest their combinations might be particularly effective in patients. In addition, given that oral administration of maraviroc achieves high drug levels in cervicovaginal fluid, combinations of maraviroc and other CCR5 inhibitors could be effective in preventing HIV-1 transmission. Moreover, since CCR5 antagonists prevent rejection of transplanted organs, maraviroc could both suppress HIV-1 and prolong organ survival for the growing number of HIV-1 patients with kidney or liver failure necessitating organ transplantation. Thus, maraviroc offers an important treatment option for patients with drug-resistant R5 HIV-1, who presently account for >50% of drug-resistance cases.
Mammalian target of rapamycin (mTOR) is a protein serine/threonine kinase that controls a wide range of growth-related cellular processes. In the past several years, many factors have been identified that are involved in controlling mTOR activity. Those factors in turn are regulated by diverse signaling cascades responsive to changes in intracellular and environmental conditions. The molecular connections between mTOR and its regulators form a complex signaling network that governs cellular metabolism, growth and proliferation. In this review, we discuss some key factors in mTOR regulation and mechanisms by which these factors control mTOR activity.
Vicriviroc (VCV) is a chemokine (C-C motif) receptor 5 (CCR5) antagonist with potent anti-HIV activity that currently is being evaluated in phase III clinical trials. In the present study, donor CCR5 density (CCR5 receptors/CD4 lymphocytes) inversely correlated with VCV antiviral activity (Spearman's correlation test; r = 0.746, P = 0.0034). Low doses of the transplant drug rapamycin (RAPA) reduced CCR5 density and enhanced VCV antiviral activity. In drug interaction studies, the RAPA/VCV combination had considerable antiviral synergy (combination indexes of 0.1-0.04) in both multicycle and single-cycle infection of lymphocytes. The synergy between RAPA and VCV translated into dose reduction indexes of 8- to 41-fold reductions for RAPA and 19- to 658-fold reductions for VCV. RAPA enhanced VCV antiviral activity against both B and non-B clade isolates, potently suppressing clade G viruses with reported reduced sensitivities to VCV and to the licensed CCR5 antagonist maraviroc. Importantly, RAPA reduction of CCR5 density in lymphocytes sensitized VCV-resistant strains to VCV, inhibiting virus production by approximately 90%. We further demonstrated the role of CCR5 density on VCV activity against resistant virus in donor lymphocytes and in cell lines expressing varying CCR5 densities. Together, these results suggest that low doses of RAPA may increase the durability of VCV-containing regimens in patients by enhancing VCV viral suppression, by allowing the use of lower doses of VCV with reduced potential for toxicity, and by controlling emerging VCV-resistant variants.
A generalized method for analyzing the effects of multiple drugs and for determining summation, synergism and antagonism has been proposed. The derived, generalized equations are based on kinetic principles. The method is relatively simple and is not limited by 1) whether the dose-effect relationships are hyperbolic or sigmoidal, 2) whether the effects of the drugs are mutually exclusive or nonexclusive, 3) whether the ligand interactions are competitive, noncompetitive or uncompetitive, 4) whether the drugs are agonists or antagonists, or 5) the number of drugs involved.
CCR5 and CXCR4 are the major HIV-1 coreceptors for R5 and X4 HIV-1 strains, respectively, and a threshold number of CD4 and chemokine receptor molecules is required to support virus infection. Therefore, we used a quantitative fluorescence-activated cell sorting assay to determine the number of CD4, CCR5, and CXCR4 antibody-binding sites (ABS) on various T cell lines, T cell subsets, peripheral blood dendritic cells (PBDC), and monocyte-derived macrophages by using four-color fluorescence-activated cell sorting analysis on fresh whole blood. Receptor levels varied dramatically among the various subsets examined and typically varied from 2- to 5-fold between individuals. CCR5 was expressed at much higher levels in CD4+/CD45RO+/CD62L-true memory cells compared with CD4+/CD45RO+/CD62L+ cells. Fresh PBDC had the highest number of CCR5 ABS among the leukocyte subsets examined but had few CXCR4 ABS, affording a strategy for sort-purifying PBDC. In vitro maturation of PBDC resulted in median 3- and 41-fold increases in CCR5 and CXCR4 ABS, respectively. We found that macrophage colony-stimulating factor caused the greatest up-regulation of both CCR5 and CXCR4 on macrophage maturation (from approximately 5,000 to approximately 50, 000 ABS) whereas granulocyte-macrophage colony-stimulating factor caused a marked decrease of CXCR4 (from approximately 5,000 ABS to <500) while up-regulating CCR5 expression (from approximately 5,000 to approximately 20,000 ABS). Absolute ABS for CD4 and the major HIV-1 coreceptors serve as a more quantitative measure of cell surface expression, and we propose that this be used for future studies looking at the modulation of CD4 or chemokine receptor expression by cytokines, HIV-1 infection, or receptor polymorphisms.
Memory T cells that home to inflamed tissues typically express the beta-chemokine receptor CCR5 and exhibit a Th1 cytokine profile. The migration of these cells into the genital tract following antigenic exposure has particular relevance to acquisition of HIV-1 infection, because CCR5 functions as the coreceptor for most sexually transmitted HIV-1 strains. We recently established methodology to purify and culture mononuclear cells from the female reproductive tract, and here we analyzed the phenotype, CCR5 expression, and cytokine production of cervicovaginal T cells in up to 16 donors. The proportion of mucosal T cells expressing CCR5 was markedly expanded as compared with peripheral blood (mean 88% vs 24% in 13 donors), but the receptor density on individual CCR5+ T cells was only slightly increased (mean 5837 vs 4191 MEPE (molecules of equivalent PE) units in 6 of 7 donors). Intracellular costaining for IL-2, IFN-gamma, IL-4, and IL-5 revealed a Th1-type pattern in cervical T cells, with significantly higher percentages of IL-2- and IFN-gamma-producing T cells in the mucosa than in blood (mean 67% vs 29%). Coexpression of surface CCR5 with intracellular IL-2 and IFN-gamma was observed only among T cells in the mucosa, but not among those in circulation. Thus, we postulate that T cell homing to the genital mucosa leads to differentiation into the combined CCR5+ Th1 phenotype. Moreover, the predominance of CCR5+ Th1-type T cells in normal cervical mucosa provides targets accessible for the efficient transmission of macrophage-tropic HIV-1 variants in women following sexual exposure.
The intensity of expression of the chemokine receptor CCR5 is involved in in vitro cell infectability by human immunodeficiency
virus (HIV)-1 R5 isolates. Because CCR5 expression varies among individuals, the hypothesis that this expression could determine
virus load in HIV-1-infected persons was tested. The mean number of CCR5 molecules per cell was measured on peripheral blood
CD4+ T lymphocytes (CCR5 density) from HIV-1-infected, asymptomatic, nontreated adults. There was a strong correlation between
HIV RNA plasma level and CCR5 density (P = .009) that was independent of cell activation and was not due to an HIV-induced CCR5 up-regulation. These data are compatible
with the hypothesis that CCR5 density is a key factor governing cell infectability and in vivo virus production and explain
the protective effect of the Δ32CCR5 deletion, which results in low CCR5 expression. CCR5 density might be of critical predictive value in HIV infection.
Conventional immunosuppressive drugs have been used effectively to prevent immunologic rejection in organ transplantation. Individuals taking these drugs are at risk, however, for the development and recurrence of cancer. In the present study we show that the new immunosuppressive drug rapamycin (RAPA) may reduce the risk of cancer development while simultaneously providing effective immunosuppression. Experimentally, RAPA inhibited metastatic tumor growth and angiogenesis in in vivo mouse models. In addition, normal immunosuppressive doses of RAPA effectively controlled the growth of established tumors. In contrast, the most widely recognized immunosuppressive drug, cyclosporine, promoted tumor growth. From a mechanistic perspective, RAPA showed antiangiogenic activities linked to a decrease in production of vascular endothelial growth factor (VEGF) and to a markedly inhibited response of vascular endothelial cells to stimulation by VEGF. Thus, the use of RAPA, instead of cyclosporine, may reduce the chance of recurrent or de novo cancer in high-risk transplant patients.
Primary HIV-1 infection causes extensive immune activation, during which CD4(+) T cell activation supports massive HIV-1 production. We tested the safety and the immune-modulating effects of combining cyclosporin A (CsA) treatment with highly active antiretroviral therapy (HAART) during primary HIV-1 infection. Nine adults with primary HIV-1 infection were treated with CsA along with HAART. At week 8, all patients discontinued CsA but maintained HAART. Viral replication was suppressed to a comparable extent in the CsA + HAART cohort and in 29 control patients whose primary infection was treated with HAART alone. CsA restored normal CD4(+) T cell levels, both in terms of percentage and absolute numbers. The increase in CD4(+) T cells was apparent within a week and persisted throughout the study period. CsA was not detrimental to virus-specific CD8(+) or CD4(+) T cell responses. At week 48, the proportion of IFN-gamma-secreting CD4(+) and CD4(+)CCR7(-) T cells was significantly higher in the CsA + HAART cohort than in the HAART-alone cohort. In conclusion, rapid shutdown of T cell activation in the early phases of primary HIV-1 infection can have long-term beneficial effects and establish a more favorable immunologic set-point. Appropriate, immune-based therapeutic interventions may represent a valuable complement to HAART for treating HIV infection.
Viral entry inhibitors represent an emerging mode of therapy for human immunodeficiency virus type 1 (HIV-1) infection. PRO
542 (CD4-immunoglobulin G2) is a tetravalent CD4-immunoglobulin fusion protein that broadly neutralizes primary HIV-1 isolates.
PRO 542 binds to the viral surface glycoprotein gp120 and blocks attachment and entry of virus into CD4+ cells. Previously, PRO 542 demonstrated antiviral activity without significant toxicity when tested at single doses ranging
to 10 mg/kg. In this study, 12 HIV-infected individuals were treated with 25-mg/kg single-dose PRO 542 and then monitored
for safety, antiviral effects, and PRO 542 pharmacokinetics for 6 weeks. The study examined two treatment cohorts that differed
in the extent of HIV-1 disease progression. PRO 542 at 25 mg/kg was well tolerated and demonstrated a serum half-life of 3
days. Statistically significant acute reductions in HIV-1 RNA levels were observed across all study patients, and greater
antiviral effects were observed in the cohort of patients with more advanced HIV-1 disease. In advanced disease (HIV-1 RNA
> 100,000 copies/ml; CD4 lymphocytes < 200 cells/mm3), PRO 542 mediated an 80% response rate and statistically significant ≈0.5 log10 mean reductions in viral load for 4 to 6 weeks posttreatment. Similar findings were obtained in an analysis of all (n = 11) advanced disease patients treated to date with single doses of PRO 542 ranging from 1 to 25 mg/kg. In addition, a significant
correlation was observed between antiviral effects observed in vivo and viral susceptibility to PRO 542 in vitro. The findings
support continued development of PRO 542 for salvage therapy of advanced HIV-1 disease.
The immunosuppressive macrolide rapamycin is used in humans to prevent graft rejection. This drug acts by selectively repressing the translation of proteins that are encoded by an mRNA bearing a 5'-polypyrimidine tract (e.g., ribosomal proteins, elongation factors). The human immunodeficiency virus type 1 (HIV-1) carries a polypyrimidine motif that is located within the tat exon 2. Treatment of human T lymphoid cells with rapamycin resulted in a marked diminution of HIV-1 transcription when infection was performed with luciferase reporter T-tropic and macrophage-tropic viruses. Replication of fully infectious HIV-1 particles was abolished by rapamycin treatment. The rapamycin-mediated inhibitory effect on HIV-1 production was reversed by FK506. The anti-HIV-1 effect of rapamycin was also seen in primary human cells (i.e., peripheral blood lymphocytes) from different healthy donors. Rapamycin was shown to diminish basal HIV-1 long terminal repeat gene expression, and the observed effect of rapamycin on HIV-1 replication seems to be independent of the virus-specific transactivating Tat protein. A constitutive beta-actin promoter-based reporter gene vector was unaffected by rapamycin treatment. Kinetic virus infection studies and exposure to reporter viruses pseudotyped with heterologous envelope proteins (i.e., amphotropic murine leukemia virus and vesicular stomatitis virus G) suggested that rapamycin is primarily affecting the life cycle of HIV-1 at a transcriptional level. Northern blot analysis confirmed that this compound is selectively targeting HIV-1 mRNA synthesis.
The hepatitis C virus (HCV) replication complex is localized within detergent-resistant membranes or lipid rafts. We analyzed the protein contents of detergent-resistant fractions isolated from Huh7 cells expressing a self-replicating full-length HCV-1b genome. Using two-dimensional gel electrophoresis followed by mass spectrometry, we identified N-Ras as one of the proteins in which expression was increased in the detergent-resistant fractions from HCV genomic replicon clones compared to control cells. N-Ras is an activator of the phosphatidylinositol-3-kinase (PI3K)-Akt pathway. We found that the activities of PI3K and Akt, as well as the activity of their downstream target, mTOR, in the HCV-replicating cells were increased. Both PI3K-Akt- and mTOR-dependent pathways have been shown to promote cell survival. In agreement with this, HCV replicon cells were resistant to serum starvation-induced apoptosis. We also characterized the role of this pathway in HCV replication. Reduction of N-Ras expression by transfection of N-Ras small interfering RNA (siRNA) resulted in increased replication of HCV. We observed a similar increase in HCV replication in cells treated with the PI3K inhibitor LY294002 and in cells transfected with mTOR siRNA. Taken together, these data suggest that increased N-Ras levels in subcellular sites of HCV replication and stimulation of the prosurvival PI3K-Akt pathway and mTOR by HCV not only protect cells against apoptosis but also contribute to the maintenance of steady-state levels of HCV replication. These effects may contribute to the establishment of persistent infection by HCV.
Rapamune is a novel immunosuppressive agent in Phase III clinical trial in renal transplantation. Its unique mechanism of action has created great interest in its use as a biochemical probe of signal transduction pathways that has provided insight into its molecular mechanism of action. This article reviews the current state of our understanding of the mechanism of action of rapamune. Copyright (c) 1998 The Canadian Society of Clinical Chemists.
Significant advances in outcomes have been achieved with combination antiretroviral therapy (cART) in patients living with
HIV. However, several ongoing needs remain with respect to the development of new treatments. The need for new or enhanced
cART may become increasingly apparent as patients live longer with HIV and a greater proportion die from non-AIDS-related
illnesses. Immunological response to cART is variable and immune failure occurs, despite virological control. Moreover, viral
suppression can be incomplete due to insufficient antiviral efficacy, acquired or transmitted drug resistance, suboptimal
pharmacokinetics/pharmacodynamics and lack of adherence. Chronic immune activation may continue even when viral replication
is relatively restrained. Patients continue to experience cardiovascular and metabolic complications, due to disease, treatment
and ageing. In addition, neurocognitive impairment and malignancy are important sources of ongoing morbidity despite cART.
HIV also affects immune system senescence and bone turnover. This review discusses potential unmet needs with respect to these
issues.
To provide an update on viral entry inhibitors focusing on recently published clinical trials, the routine clinical use of these medications, and future drug candidates.
Clinical trials and cohort studies support the efficacy of both enfuvirtide and maraviroc in the management of treatment-experienced patients. In clinical practice, tolerability issues, particularly injection site reactions, have limited the clinical use of enfuvirtide. Providers should be aware of the need for tropism determination and dosing requirements for maraviroc. The novel chemokine (C-C motif) receptor 5-blocking agent, vicriviroc, has shown promise and is currently in phase III clinical development.
The rapid pace of scientific discovery and pharmaceutical development has led to the release of several novel and well tolerated antiretroviral agents, with activity against resistant isolates. Entry inhibitors remain a critical therapeutic option for treatment-experienced patients. Providers need to be familiar with these agents, and future drug development should be encouraged.
Some experimental trials have demonstrated that rapamycin (RAPA) is able to inhibit HIV-1 progression in three different ways: (1) reducing CCR5-gene transcription, (2) blocking interleukin-2 intracellular secondary messenger (mammalian target of rapamycin), and (3) up-regulating the beta-chemokine macrophage inflammatory protein (MIP; MIP-1alpha and MIP-1beta). We present the preliminary results of a prospective nonrandomized trial concerning the first HIV patient series receiving RAPA monotherapy after liver transplantation (LT).
Since June 2003, 14 HIV patients have received cadaveric donor LT due to end-stage liver disease (ESLD) associated or not associated with hepatocellular carcinoma, scored by the model for ESLD system. Patients were assessed using the following criteria for HIV characterization: CD4 T-cell count more than 100/mL and HIV-RNA levels less than 50 copies/mL. Primary immunosuppression was based on calcineurin inhibitors (CI), whereas switch to RAPA monotherapy occurred in cases of CI complications or Kaposi's sarcoma.
Mean overall post-LT follow-up was 14.8 months (range: 0.5-52.6). Six of 14 patients were administered RAPA monotherapy. Mean preswitch period from CI to RAPA was 67 days (range: 10-225 days). Mean postswitch follow-up was 11.9 months (range: 2-31 months). All patients were affected by ESLD, which was associated with hepatocellular carcinoma in seven patients. ESLD occurred due to hepatitis C virus (HCV)-related hepatopathy for nine patients, hepatitis B virus-related hepatopathy for one patient, and hepatitis B virus-HCV hepatopathy for four patients. Significantly better control of HIV and HCV replication was found among patients taking RAPA monotherapy (P=0.0001 and 0.03, respectively).
After in vitro and in vivo experimental evidence of RAPA antiviral proprieties, to our knowledge, this is the first clinical report of several significant benefits in long-term immunosuppression maintenance and HIV-1 control among HIV positive patients who underwent LT.
Highly active antiretroviral therapy (HAART) has significantly reduced mortality, and prolonged life expectancy of human immunodeficiency virus (HIV)-positive patients. Such improvements have led to increasing numbers of HIV-infected patients with end-stage organ disease as potential candidates for transplantation. A HAART regimen usually consists of a combination of nucleoside reverse transcriptase inhibitors (NRTI), non-nucleoside reverse transcriptase inhibitors (NNRTI), and/or protease inhibitors (PI). PI are known to strongly inhibit the cytochrome P450 3A (CYP3A) enzyme system that is responsible for the metabolism of immunosuppressive drugs, such as tacrolimus, sirolimus, and cyclosporine. Besides these pharmacokinetic drug-drug interactions, potential pharmacodynamic drug-drug interactions may also occur with concomitant HAART and antimetabolites, such as mycophenolate mofetil. An approach to immunosuppressive management in HIV-infected organ transplant recipients requires attention to such complexities as unique drug-drug interactions and increased drug-related toxicities.
Despite the availability of 31 antiretroviral agents or fixed-dose combinations in the United States and European Union, there is a continuing need for antiretroviral agents with high genetic barriers to resistance, simple dosing schedules, and favorable tolerability and safety profiles. Vicriviroc is a small-molecule chemokine receptor antagonist that inhibits the binding of R5-tropic HIV-1 to host cells at the CCR5 co-receptor, thus preventing viral entry.
To present an evidence-based assessment of the clinical efficacy, pharmacokinetics, and safety profile of vicriviroc.
We discuss available peer-reviewed publications as well as preliminary data presented at relevant scientific meetings.
Vicriviroc has a favorable pharmacokinetic profile with a half-life that enables once-daily dosing. Minimal drug interactions have been demonstrated with other available antiretrovirals. Early clinical trials have established the safety of vicriviroc in both treatment-naive and treatment-experienced R5-tropic HIV-1 infected individuals. A Phase II study in treatment-experienced patients demonstrated early efficacy of 30 mg vicriviroc in a regimen containing a ritonavir-boosted protease inhibitor (PI/r). Phase III studies using the 30-mg PI/r dosing paradigm in R5-tropic treatment-experienced patients have completed 48 weeks, but data are not yet available. These results will further elucidate the role of vicriviroc in the treatment of HIV-1 infected individuals.
Expert panels have provided guidelines for the treatment of HIV infection for more than a decade. The guidelines have evolved rapidly reflecting the remarkable improvements in HIV therapeutics over this time. From guidelines based mostly on expert opinion - the current guidelines are now primarily evidence-based recommendations - which the vast majority of treating clinicians accept and follow. We will highlight the major guideline recommendations for initiation of antiretroviral therapy - focusing on new data for the asymptomatic patient and those presenting with acute AIDS-related opportunistic infections. Given the number of new drugs available, we are currently able to offer virtually all patients in practice - a fully suppressive regimen, even in patients with substantial multi-drug resistant HIV. A remarkable achievement since AZT was first introduced for the treatment of HIV. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, vol. 85, issue 1, 2010.
Systemic treatment options for advanced renal cell carcinoma (RCC) have expanded considerably with the development of targeted therapies. Clear cell RCC commonly features mutation or inactivation of the von Hippel-Lindau gene and resultant overexpression of vascular endothelial growth factor (VEGF). The first drug to validate VEGF as a target in the treatment of clear cell RCC was the monoclonal antibody bevacizumab. Since then, anti-VEGF receptor therapy with multitargeted kinase inhibitors also has shown substantial efficacy. Sunitinib is now a standard first-line therapy for advanced disease and sorafenib is among the second-line treatment options. Other kinase inhibitors are in development. Mammalian target of rapamycin (mTOR) is a second validated therapeutic target as the mTOR inhibitor temsirolimus has been shown to prolong survival in first-line treatment of poor prognosis RCC of all histologies. Everolimus is an oral mTOR inhibitor and has been shown to prolong progression-free survival when used in second-line treatment. Non-clear cell and sarcomatoid RCC are both underrepresented in completed trials but are the subject of active research. Ongoing and planned studies will also evaluate the use of combinations of targeted agents, a strategy that is not advisable outside of clinical trials. Finally, postnephrectomy adjuvant treatment with targeted agents is not yet standard but is under investigation in phase III trials.
Sirolimus is an antiproliferative immunosuppressive agent that inhibits the mammalian target of rapamycin. It is highly effective in preventing acute renal allograft rejection and can be used with either calcineurin inhibitors, antimetabolites or corticosteroids. Early studies in renal transplantation have provided insight into optimal dosing strategies of sirolimus and of concomitant immunosuppressive agents. Familiarity with the adverse effect profile of sirolimus and pharmacokinetic and dynamic interactions with other immunosuppressive agents allows for earlier recognition and better management of sirolimus-related complications. The role of sirolimus in preserving long-term renal function, post-transplant malignancies and in prevention of atherosclerosis is currently being considered.
Maraviroc, the only CCR5 antagonist HIV inhibitor currently approved, has potent antiviral activity in treatment-experienced individuals infected with CCR5-using HIV-1 (R5 HIV-1). However, recent data from the MOTIVATE trials indicate that R5 HIV-1 can develop resistance to Maraviroc, underscoring the need for additional CCR5 antagonists. The CCR5 antagonist aplaviroc (APL) is active against Maraviroc-resistant viral strains but its clinical development has ended because of dose-related toxicity. Here we demonstrate that reduction of CCR5 density (receptors/cell) with the immunomodulatory drug rapamycin (RAPA) enhances the antiviral activity of APL, allowing lower, non-toxic effective doses. In the presence of RAPA, the concentration of APL required for 90% inhibition of R5 HIV-1 in primary CD4 lymphocytes was reduced by as much as 25-fold. We conclude that low doses of RAPA may reduce the anti-HIV effective dose of APL-derivatives currently in development and thus minimize their potential toxicity. Combinations of RAPA and CCR5 antagonists could provide an effective means to control drug-resistant R5 HIV in patients, most notably those infected with Maraviroc-resistant viruses.
We evaluated the stages of VEGF-A(164) driven angiogenesis that are inhibited by therapeutic doses of rapamycin and the potential role of S6K1 in that response.
We assessed the effects of rapamycin on the several stages of angiogensis and lymphangiogenesis induced with an adenovirus expressing VEGF-A(164) (Ad-VEGF-A(164)) in the ears of adult nude mice. Rapamycin (0.5 mg/kg/d) effectively inhibited mTOR and downstream S6K1 signaling and partially inhibited Akt signaling, likely through effects on TORC2. The earliest stages of angiogenesis, including mother vessel formation and increased vascular permeability, were strikingly inhibited by rapamycin, as was subsequent formation of daughter glomeruloid microvasular proliferations. However, later stage formation of vascular malformations and lymphangiogenesis were unaffected. Retrovirally delivered isoforms and shRNAs demonstrated that S6K1 signaling plays an important role in early VEGF-A(164)-angiogenesis.
Rapamycin potently inhibited early and mid stages of VEGF-A(164)-driven angiogenesis, but not late-stage angiogenesis or lymphangiogenesis. Rapamycin decreased phosphorylation of both Akt and S6, suggesting that both the TORC1 and TORC2 pathways are impacted. Inhibition of S6K1 signaling downstream of mTOR is a major component of the antiangiogenesis action of rapamycin.
The interferon-induced Jak-STAT signal alone is not sufficient to explain all the biological effects of IFN. The PI3-K pathways have emerged as a critical additional component of IFN-induced signaling. This study attempted to clarify that relationship between IFN-induced PI3-K-Akt-mTOR activity and anti-viral action.
When the human normal hepatocyte derived cell line was treated with rapamycin (rapa) before accretion of IFN-alpha, tyrosine phosphorylation of STAT-1 was diminished. Pretreatment of rapa had an inhibitory effect on the IFN-alpha-induced expression of PKR and p48 in a dose dependent manner. Rapa inhibited the IFN-alpha inducible IFN-stimulated regulatory element luciferase activity in a dose-dependent manner. However, wortmannin, LY294002 and Akt inhibitor did not influence IFN-alpha inducible luciferase activity. To examine the effect of PI3-K-Akt-mTOR on the anti-HCV action of IFN-alpha, the full-length HCV replication system, OR6 cells were used. The pretreatment of rapa attenuated its anti-HCV replication effect in comparison to IFN-alpha alone, whereas the pretreatment with PI3-K inhibitors, wortmannin and LY294002 and Akt inhibitor did not influence IFN-induced anti-HCV replication.
IFN-induced mTOR activity, independent of PI3K and Akt, is the critical factor for its anti-HCV activity. Jak independent mTOR activity involved STAT-1 phosphorylation and nuclear location, and then PKR is expressed in hepatocytes.
The purpose of this review is to discuss recent pharmacological, virological, and clinical data that concern enfuvirtide usage in different antiretroviral combinations.
Randomized, recent trials in multidrug-experienced patients suggest that antiretroviral combinations with enfuvirtide have excellent virological responses with new antiretroviral compounds, including darunavir, etravirine, raltegravir, vicriviroc, and maraviroc. Trials confirm long-term safety, in spite of moderate injection-site reactions or pain, and lack of significant interactions. Preliminary data suggest that switching from enfuvirtide to raltegravir is effective and using enfuvirtide in prophylaxis of mother-to-child transmission is well tolerated. To administer enfuvirtide in an intensification strategy in antiretroviral-naïve or experienced populations may accelerate virological decline.
Dosage adaptations to renal insufficiency are not necessary with enfuvirtide. Spinal fluid concentrations and ombilic cord passage are negligible. Durability of virological responses with enfuvirtide in combinations has been confirmed, in spite of injection-site reactions and twice daily subcutaneous administration. Enfuvirtide should be used with at least one other fully active drug in optimized background therapy in multidrug-experienced populations, a possible exception being with entry inhibitors, which may further benefit from the addition of a third active drug. Data concerning enfuvirtide in antiretroviral combinations show accelerated viral load decline, and the possibility of switching from enfuvirtide to raltegravir without modification of optimized background therapy.
Raltegravir is the first approved human immunodeficiency virus type 1 (HIV-1) integrase inhibitor; it targets the strand transfer
step of HIV-1 integration. Clinical trials have demonstrated that raltegravir-containing regimens have potent antiretroviral
activity and are well tolerated in HIV-1–infected individuals. In antiretroviral treatment–experienced persons with drug-resistant
HIV infection, raltegravir-containing treatment with an optimized background regimen was superior to an optimized background
regimen alone. In treatment-naive persons, raltegravir was not inferior to efavirenz when the drugs were administered with
tenofovir and lamivudine or emtricitabine. Raltegravir is metabolized by glucuronidation, not hepatically; thus, the potential
for drug-drug interactions is decreased. Drug resistance, conferred by substitutions in the gene coding for the HIV-1 integrase
enzyme, develops relatively frequently after virologic failure. As an antiretroviral drug with a novel mechanism of action,
raltegravir is an important advancement in HIV-1 treatment options.
Epidemiological and experimental studies support an important role of the phosphoinosite 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway in the biology of human cancers. Over the past few years a number of components of this signaling cascade have been the subject of intense drug discovery activities. This article summarizes progress made in the identification of kinase inhibitors of PI3K and mTOR, with an emphasis placed on drugs currently undergoing clinical trials. Potential combination strategies, safety concerns, and resistance mechanisms for this new generation of anticancer agents are also discussed.
mTOR complex 2 (mTORC2) contains the mammalian target of rapamycin (mTOR) kinase and the Rictor regulatory protein and phosphorylates Akt. Whether this function of mTORC2 is critical for cancer progression is unknown. Here, we show that transformed human prostate epithelial cells lacking PTEN require mTORC2 to form tumors when injected into nude mice. Furthermore, we find that Rictor is a haploinsufficient gene and that deleting one copy protects Pten heterozygous mice from prostate cancer. Finally, we show that the development of prostate cancer caused by Pten deletion specifically in prostate epithelium requires mTORC2, but that for normal prostate epithelial cells, mTORC2 activity is nonessential. The selective requirement for mTORC2 in tumor development suggests that mTORC2 inhibitors may be of substantial clinical utility.
The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is currently one of the most exciting drug targets in oncology. However, only a short time ago, the paradigm existed that drugs targeted to the four PI3K class I isoforms would be too toxic for use in cancer therapy due to effects on physiologic signaling. Since that time, studies have delineated the roles of these four isoforms in nonpathologic signaling as well as their roles in cancer. An extensive effort has gone into developing agents that inhibit one or more PI3K isoforms, as well as closely related proteins implicated in cancer. These agents have proved to be tolerable and therapeutically beneficial in animal studies, and a number are in clinical testing. The agents, their properties, and their molecular targets are discussed in this review.
The capacity of the immunomodulatory drug rapamycin (RAPA) to inhibit replication of the CCR5 strain of human immunodeficiency virus (HIV) in vitro prompted us to test its effects in a murine preclinical model of HIV infection. RAPA (0.6 or 6 mg/kg body weight) or its vehicle were administered daily, per os, to SCID mice reconstituted with human peripheral blood leucocytes (hu-PBL) starting 2 days before the intraperitoneal challenge with the R5 tropic SF162 strain of HIV-1 (1000 50% tissue culture infective dose/ml). Relative to hu-PBL-SCID mice that received no treatment, HIV-infected hu-PBL-SCID mice treated with the vehicle control for 3 weeks exhibited a severe depletion of CD4(+) cells (90%), an increase in CD8(+) cells and an inversion of the CD4(+)/CD8(+) cell ratio. In contrast, treatment of HIV-infected mice with RAPA prevented a decrease in CD4(+) cells and the increase of CD8(+) cells, thereby preserving the original CD4(+):CD8(+) cell ratio. Viral infection also resulted in the detection of HIV-DNA within peritoneal cells and spleen, and lymph node tissues of the vehicle-treated mice within 3 weeks of the viral challenge. In contrast, treatment with RAPA decreased cellular provirus integration and reduced HIV-RNA levels in the blood. Furthermore, in co-cultivation assays, spleens from RAPA-treated mice exhibited a reduced capacity for infecting allogeneic T cells which was dose-dependent. These data show that RAPA possesses powerful anti-viral activity against R5 strains of HIV in vivo and support the use of additional studies to evaluate the potential application of this drug in the management of HIV patients.
Research into mTOR, mammalian Target Of Rapamycin as an important drug target continues to be extremely interesting, both in terms of the increased molecular knowledge being acquired at the basis of various human diseases, and also for possible applications in drug cancer therapy. The mTOR signaling system plays a key role in several transduction pathways that are necessary for cell cycle progression and cellular proliferation. Drugs known as mTOR inhibitors have been included in ongoing and in recently completed cancer trials. New insights into the mTOR signaling system are helping to clarify the functionality of key mTOR components, and especially their possible role in apoptosis, angiogenesis and tumor progression. Three other molecules, already approved for therapeutic use and being commercialized (Everolimius, Temsirolimus and Zotarolimus) are added to Rapamycin (also known as Sirolimus), the parent drug of the mTOR inhibitors. Of these, only Temsirolimus is currently approved in the treatment of renal cell carcinoma, while the others are approved for organ transplant rejection and coronary artery restenosis. There are at least 10 other molecules currently under development for clinical and preclinical studies. This review offers an updated synopsis of the mTOR signaling system, in particular as regards relevant aspects of cancer research, looks at the known mTOR inhibitors and gives a systematic vision of current trials for each individual molecule subject to clinical investigation.
The development of new protease inhibitors, new non-nucleoside reverse transcriptase inhibitors and novel therapeutic drug classes has dramatically changed the approach to managing HIV-1 patients with multidrug resistant virus. This has led many clinicians to reevaluate the clinical utility of enfuvirtide.
To summarize recent literature on enfuvirtide and to reassess enfuvirtide's role in the management of HIV-1 infection.
MEDLINE (1990 to February Week 2 2008) and EMBASE (1990 to 2008 week 8) databases were searched using the following terms: 'enfuvirtide', 'Fuzeon', 'T20', 'HIV fusion inhibitors', and 'HIV entry inhibitor'; limits: English language. Reference lists of articles deemed relevant were hand searched for additional publications. Significant abstracts from recent international HIV conferences were also identified.
Enfuvirtide can optimize the response to new combinations of HIV-1 drug regimens in multiresistant patients. Its inclusion as an active agent is effective but use is impacted by its high cost, inconvenient route of administration and cosmetic side-effect profile.
The emergence of viral resistance is one of the greatest challenges in the treatment of HIV infection. Maraviroc is the first member of a new class of antiretroviral medications, the CCR5-receptor antagonists. It is approved by the US Food and Drug Administration (FDA) for use in combination with other antiretroviral agents in treatment-experienced patients infected with multidrug-resistant, CCR5-tropic HIV-1.
This article provides an overview of the pharmacology, efficacy, and tolerability of maraviroc in the treatment of HIV-1 infection.
Relevant information was identified through a search of MEDLINE (January 2000-May 2008) using the terms maraviroc, UK-427,857, and CCR5-receptor antagonist. Also consulted were abstracts from the International AIDS Society Conference, the Conference on Retroviruses and Opportunistic Infections, and other relevant scientific meetings. Additional publications were found by searching the reference lists of the identified articles and the FDA Web site.
Maraviroc is a selective, reversible, small-molecule CCR5-receptor antagonist. In vitro, it has potent anti-HIV-1 activity, with a mean 90% inhibitory concentration of 2.0 nmol/L. It is widely distributed, with a V(d) of approximately 194 L. Maraviroc is moderately metabolized in the liver (65.3%), primarily via the cytochrome P450 3A4 isozyme. It has an elimination t(1/2) of 15.9 to 22.9 hours. Until more data are available, maraviroc should be avoided in patients with severe hepatic insufficiency; dose adjustment does not appear to be necessary on the basis of age, sex, or renal function. In 2 Phase IIb/III studies, maraviroc 300 mg PO QD or BID was found to be more efficacious than placebo in reducing the viral load at 48 weeks in treatment-experienced, CCR5-tropic HIV-1-infected patients receiving an optimized background regimen (difference vs placebo-QD arm: -0.89 log(10) copies/mL [97.5% CI, -1.17 to -0.62]; BID arm: -1.05 log(10) copies/mL [97.5% CI, -1.33 to -0.78]). The proportion of patients with a viral load < 50 copies/mL was 43.2% in the QD arm and 45.5% in the BID arm, compared with 16.7% in the placebo arm (P < 0.001, both treatment arms vs placebo). In treatment-naive patients infected with CCR5-tropic virus only, maraviroc 300 mg PO BID was not noninferior to oral efavirenz 600 mg QD (difference = -4.2%; lower bound of the 1-sided 97.5% CI, -10.9 [predefined statistical cutoff for noninferiority, -10]). Maraviroc was generally well tolerated in clinical trials. The most frequently reported (> or = 5%) adverse events were upper respiratory tract infection (20.0%), cough (12.7%), pyrexia (12.0%), rash (9.6%), musculoskeletal complaints (8.7%), gastrointestinal and abdominal pain (8.2%), dizziness (8.2%), appetite disorders (7.3%), insomnia (7.0%), herpes infection (6.8%), sinusitis (6.3%), joint complaints (6.1%), bronchitis (5.9%), and constipation (5.4%). The recommended dose of maraviroc differs based on concomitant medications, ranging from 150 to 600 mg BID.
When used in combination with other antiretroviral agents, maraviroc appears to be a promising agent for treatment-experienced patients infected with multidrug-resistant, CCR5-tropic HIV-1.
A streptomycete was isolated from an Easter Island soil sample and found to inhibit Candida albicans, Microsporum gypseum and Trichophyton granulosum. The antibiotic-producing microorganism was characterized and identified as Streptomyces hygroscopicus. The antifungal principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named rapamycin. Rapamycin is mainly active against Candida albicans; minimum inhibitory concentration against ten strains ranged from 0.02 to 0.2 mug/ml. Its apparent activity against Microsporum gypseum and Trichophyton granulosum is lower because of its instability in culture media on prolonged incubation required by these fungi. No activity was observed against gram-positive and gram-negative bacteria. Acute toxicity in mice is low.
Objective:
Rapamune is a novel immunosuppressive agent in Phase III clinical trial in renal transplantation. Its unique mechanism of action has created great interest in its use as a biochemical probe of signal transduction pathways that has provided insight into its molecular mechanism of action. This article reviews the current state of our understanding of the mechanism of action of rapamune.
It has been estimated that, to date, about 48% of all HIV-infected people in the world carry HIV-1 subtype C virus. Therefore, it is of great importance to gain better knowledge about the genetic and biological characteristics of this virus subtype. In the present study, the biological properties of HIV-1 isolates obtained from nine Ethiopian patients with AIDS were studied. DNA sequencing of the V3 loop of gp120 classified the isolates as subtype C. In primary isolation cultures, virus infection was accompanied by syncytium formation and cell lysis. Interestingly, when examining the growth in primary monocyte-macrophage cultures, initial low-level virus replication was followed by a nonproductive state, from which virus could be rescued by cocultivation with Jurkat(tat) cells. Furthermore, none of the isolates replicated in T cell lines (CEM, MT-2, HuT-78, and H9) or in the promonocytic cell line U937 clone 2. All isolates could use CCR5 as coreceptor, whereas no isolates could use CCR2b, CCR3, CCR5, CXCR4, Bonzo/STRL33, or BOB/GPR15. The genotype of the V3 region correlated with the MT-2 negative/non-syncytium-inducing (NSI) phenotype. Comparative studies revealed that the scarcity of CXCR4 usage as well as other phenotypic characteristics of subtype C isolates distinguish this subtype. On the basis of these data, we suggest that in addition, factors other than viral phenotype may govern the pathogenic potential of subtype C isolates.
Sirolimus is a novel macrolide immunosuppressive drug with a mechanism of action distinct from that of both cyclosporine and tacrolimus. Recent clinical studies have demonstrated a decrease in acute rejection episodes in renal transplant patients receiving sirolimus compared with controls. The major toxicities associated with sirolimus treatment are thrombocytopenia and hyperlipidemia. In addition, concern has been raised by the higher serum creatinine levels noted in patients receiving sirolimus and cyclosporine compared with controls receiving cyclosporine and azathioprine.
The objective of the present review is to summarize the efficacy and toxicity data for sirolimus. Special consideration is given to evidence that links these effects to dose or whole-blood concentrations of sirolimus.
The literature indicates that trough concentrations of sirolimus >15 ng/mL appear to be associated with a greater risk of both thrombocytopenia and hyperlipidemia, whereas trough sirolimus concentrations <6 ng/mL have been associated with an increased incidence of acute rejection.
The evidence to date supports target trough sirolimus concentrations of 6 to 15 ng/mL in most patients. In higher-risk groups and patients receiving cyclosporine-sparing regimens, higher concentrations may be necessary to achieve similar efficacy.
Earlier open-label clinical trials have provided conflicting data on the effects of cyclosporin-A (CsA) on the clinical course and immune status of patients with HIV disease. With the prospects for wider use of CsA in the setting of solid organ transplantation in HIV-infected persons, data on the safety and immunologic activity of this agent are needed. We report here the results of a randomized, double-blind, placebo-controlled trial to assess the safety and immunologic activity of CsA administration in early HIV disease.
Twenty-eight patients with confirmed HIV infection, CD4 cell counts greater than 500 x 106/L, and plasma HIV RNA >600 copies/mL were randomized to receive 2 mg/kg of CsA (Neoral) twice daily or identical placebo for 12 weeks. Subjects were stratified for the presence or absence of stable concomitant antiviral therapy. The primary end point was the effect of therapy on immune activation as assessed by the levels of soluble interleukin-2 receptors. Secondary end points included safety and effects of treatment on plasma HIV RNA, CD4 cell count, and other markers of immune activation and function.
The low dose of CsA used in this study did not suppress immune activation or increase circulating CD4 cell counts. Delayed-type hypersensitivity responses were not affected; however, lymphocyte proliferative responses tended to decrease. CsA-treated patients experienced a small but significant rise in plasma HIV RNA levels.
Low-dose CsA has no benefit in patients with stable early HIV disease, and its administration may be associated with an increase in plasma HIV RNA. The use of CsA in HIV-infected patients undergoing organ transplantation should be undertaken with caution
Propagation of R5 strains of HIV-1 on CD4 lymphocytes and macrophages requires expression of the CCR5 coreceptor on the cell surface. Individuals lacking CCR5 (CCR5 Delta 32 homozygous genotype) are phenotypically normal and resistant to infection with HIV-1. CCR5 expression on lymphocytes depends on signaling through the IL-2 receptor. By FACS analysis we demonstrate that rapamycin (RAPA), a drug that disrupts IL-2 receptor signaling, reduces CCR5 surface expression on T cells at concentrations as low as 1 nM. In addition, lower concentrations of RAPA (0.01 nM) were sufficient to reduce CCR5 surface expression on maturing monocytes. PCR analysis on peripheral blood mononuclear cells (PBMCs) showed that RAPA interfered with CCR5 expression at the transcriptional level. Reduced expression of CCR5 on PBMCs cultured in the presence of RAPA was associated with increased extracellular levels of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta. In infectivity assays, RAPA suppressed the replication of R5 strains of HIV-1 both in PBMC and macrophage cultures. In total PBMC cultures, RAPA-mediated inhibition of CCR5-using strains of HIV-1 occurred at 0.01 nM, a concentration of drug that is approximately 103 times lower than therapeutic through levels of drug in renal transplant recipients. In addition, RAPA enhanced the antiviral activity of the CCR5 antagonist TAK-779. These results suggest that low concentrations of RAPA may have a role in both the treatment and prevention of HIV-1 infection.
HIV infection of primary human T cells requires T cell activation signals. However, how strength, duration, and quality of TCR signals affect susceptibility of resting human T cells to HIV infection remains poorly understood. We found that the same threshold and duration of antigen signals that lead to optimal T cell activation are required for HIV to progress beyond the level of reverse transcription within resting T cells. Remarkably, sustained cytokine signaling from the IL-2 receptor following TCR triggering was critical in establishing productive infection. While blockade of TCR signaling pathways with inhibitors of the phosphatidylinositol 3-kinase pathway caused a partial pre-integration block, another inhibitor, rapamycin, completely suppressed the infection. In contrast, cyclosporin A or FK506, inhibitors of NFAT, failed to block infection if the T cells were pre-activated. Collectively, these results bring to light significant parallels between successful HIV infection and optimal thresholds of T cell activation. Furthermore, our results underscore the critical role of IL-2 signaling in establishing productive HIV infection. These findings have important implications for our understanding of the complex interplay of HIV with host factors induced upon T cell activation.
The mammalian TOR (mTOR) pathway integrates nutrient- and growth factor-derived signals to regulate growth, the process whereby cells accumulate mass and increase in size. mTOR is a large protein kinase and the target of rapamycin, an immunosuppressant that also blocks vessel restenosis and has potential anticancer applications. mTOR interacts with the raptor and GbetaL proteins to form a complex that is the target of rapamycin. Here, we demonstrate that mTOR is also part of a distinct complex defined by the novel protein rictor (rapamycin-insensitive companion of mTOR). Rictor shares homology with the previously described pianissimo from D. discoidieum, STE20p from S. pombe, and AVO3p from S. cerevisiae. Interestingly, AVO3p is part of a rapamycin-insensitive TOR complex that does not contain the yeast homolog of raptor and signals to the actin cytoskeleton through PKC1. Consistent with this finding, the rictor-containing mTOR complex contains GbetaL but not raptor and it neither regulates the mTOR effector S6K1 nor is it bound by FKBP12-rapamycin. We find that the rictor-mTOR complex modulates the phosphorylation of Protein Kinase C alpha (PKCalpha) and the actin cytoskeleton, suggesting that this aspect of TOR signaling is conserved between yeast and mammals.
Deregulation of Akt/protein kinase B (PKB) is implicated in the pathogenesis of cancer and diabetes. Akt/PKB activation requires
the phosphorylation of Thr308 in the activation loop by the phosphoinositide-dependent kinase 1 (PDK1) and Ser473 within the carboxyl-terminal hydrophobic motif by an unknown kinase. We show that in Drosophila and human cells the target of rapamycin (TOR) kinase and its associated protein rictor are necessary for Ser473 phosphorylation and that a reduction in rictor or mammalian TOR (mTOR) expression inhibited an Akt/PKB effector. The rictor-mTOR
complex directly phosphorylated Akt/PKB on Ser473 in vitro and facilitated Thr308 phosphorylation by PDK1. Rictor-mTOR may serve as a drug target in tumors that have lost the expression of PTEN, a tumor
suppressor that opposes Akt/PKB activation.
Current antiretroviral therapy has had a significant impact on HIV associated morbidity and mortality. Despite these positive outcomes current antiretroviral regimens have significant deficiencies which include multiple drug-drug interactions, high pill burdens, and considerable financial expense. Perhaps the greatest shortcoming is the apparent inability of current therapy to disrupt low level viremia in certain cellular reservoirs despite maximal virologic control as determined by polymerase chain reaction detection. These drug-resilient reservoirs preclude the ability to discontinue antiretrovirals while maintaining viral control. Additionally, they may be responsible at least in part for the evolution of drug resistant variants. Various researchers have proposed that certain immune modulating agents known as virostatics (i.e., hydroxyurea (HU), mycophenolate mofetil (MMF), and cyclosporine (CSA)) may have some efficacy in managing HIV disease and/or disrupting resilient reservoirs. These agents may act by reducing the pool of activated CD4+ cells which are susceptible to infection thereby inhibiting the characteristic immune over-activation seen in most HIV infected patients. Virostatics have primarily been studied in patients with advanced HIV disease and as components of trials involving structured treatment interruptions. These trials have demonstrated conflicting results with regard to viral load and CD4+ cell counts as well as potential adverse effects including immune suppression. Before widespread use of these agents can be recommended, larger, well controlled trials will need to be conducted to determine which virostatic agents are appropriate for use in HIV infected patients and the most efficacious time course within which to initiate these agents.