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New targets for inhibitors of HIV-1 replication
Abstract
Despite the success of protease and reverse transcriptase inhibitors, new
drugs to suppress HIV-1 replication are still needed. Several other early
events in the viral life cycle (stages before the viral genome is inserted
into host cell DNA) are susceptible to drugs, including virus attachment to
target cells, membrane fusion and post-entry events such as integration, accessory-gene
function and assembly of viral particles. Among these, inhibitors of virus?cell
fusion and integration are the most promising candidates.
... Several members of a new class of inhibitors based on blocking human immunodeficiency virus type 1 (HIV-1) entry into target cells are now in, or approaching, human clinical trials (8,52,77,80,85,90,98). These various compounds antagonize different stages in the multistep pathway by which HIV-1 fuses with susceptible cells. ...
... Both CCR5 and CXCR4 are important targets for pharmacological intervention, and several inhibitors have been identified that are specific for each receptor (8,51,52,77,80,85,90,98). Reductions in the amount of plasma X4 viruses were observed during trials of the CXCR4 inhibitor AMD3100, but the clinical development of this particular compound has been discontinued because of pharmacological and toxicology concerns (26). ...
... Hence, it is prudent to study escape pathways in vitro in order to learn what might happen in clinical use. A particular concern with CCR5 inhibitors is that they might drive the evolution of X4 variants in vivo (35,51,73,77). We have previously reported on the in vitro escape of an R5 HIV-1 isolate, CC1/ 85, from AD101 (SCH 350581), a CCR5 inhibitor structurally related to SCH-C (51,101,108). ...
We have described previously the generation of an escape variant of human immunodeficiency virus type 1 (HIV-1), under the selection pressure of AD101, a small molecule inhibitor that binds the CCR5 coreceptor (A. Trkola, S. E. Kuhmann, J. M. Strizki, E. Maxwell, T. Ketas, T. Morgan, P. Pugach, S. X. L. Wojcik, J. Tagat, A. Palani, S. Shapiro, J. W. Clader, S. McCombie, G. R. Reyes, B. M. Baroudy, and J. P. Moore, Proc. Natl. Acad. Sci. USA 99:395-400, 2002). The escape mutant, CC101.19, continued to use CCR5 for entry, but it was at least 20,000-fold more resistant to AD101 than the parental virus, CC1/85. We have now cloned the env genes from the the parental and escape mutant isolates and made chimeric infectious molecular clones that fully recapitulate the phenotypes of the corresponding isolates. Sequence analysis of the evolution of the escape mutants suggested that the most relevant changes were likely to be in the V3 loop of the gp120 glycoprotein. We therefore made a series of mutant viruses and found that full AD101 resistance was conferred by four amino acid changes in V3. Each change individually caused partial resistance when they were introduced into the V3 loop of a CC1/85 clone, but their impact was dependent on the gp120 context in which they were made. We assume that these amino acid changes alter how the HIV-1 Env complex interacts with CCR5. Perhaps unexpectedly, given the complete dependence of the escape mutant on CCR5 for entry, monomeric gp120 proteins expressed from clones of the fully resistant isolate failed to bind to CCR5 on the surface of L1.2-CCR5 cells under conditions where gp120 proteins from the parental virus and a partially AD101-resistant virus bound strongly. Hence, the full impact of the V3 substitutions may only be apparent at the level of the native Env complex.
... Also, there were approximately 36.9 million people living with HIV at the end of 2014 with 2.0 million people becoming newly infected with HIV in 2014 globally [2]. Various compounds have been reported to inhibit the replication of HIV-1 in vitro [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The HIV-1 Reverse Transcriptase (RT) enzyme shows both RNA-and DNA-dependent polymerase activities, and the lack of RT activity in the eukaryotic cells made RT as one of the most attractive target for the development of anti-VIH-1 agents [6,13]. ...
... Various compounds have been reported to inhibit the replication of HIV-1 in vitro [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The HIV-1 Reverse Transcriptase (RT) enzyme shows both RNA-and DNA-dependent polymerase activities, and the lack of RT activity in the eukaryotic cells made RT as one of the most attractive target for the development of anti-VIH-1 agents [6,13]. The non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) can suppress the virus replication in cell cultures for at least 3 months [23][24][25]. ...
... The non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) can suppress the virus replication in cell cultures for at least 3 months [23][24][25]. The HEPT was the first NNRTI synthesized in 1989 [26] and has been considered as the lead compound [13] and most Quantitative Structure Activity Relationship (QSAR) studies have been carried out on HEPT derivatives [27][28][29][30][31][32][33][34][35][36]. ...
A study of the relationships between electronic structure and anti HIV-1 activities of a series of 1-[2-hydroxyéthoxyméthyl]-6-(phenylthio)thymine (HEPT) derivatives was carried out. The electronic structure was obtained at the B3LYP/6-311G(d,p) level after full geometry optimization. A linear multiple regression analysis was performed with the anti HIV activity as the dependent variable and a set of reactivity indices belonging to the atoms of a common skeleton as independent variables. A statistically significant equation (R= 0.98, R²= 0.95, adj-R²= 0.94, F(6,14)=49.02, p<0.00000 and SD=0.28) was obtained. The process seems to be charge and orbital-controlled. Based on the analysis of the results, a partial two-dimensional anti HIV-1 pharmacophore is proposed.
... Nevertheless, this natural polyphenolic compound has shown potential antiviral activity against several pathogenic human viruses (i.e. HIV, Influenza, Hepatitis virus, Dengue virus, Chikungunya virus, Enterovirus 71 and coxsackievirus A16) (Mishra et al., 2020;Moore & Stevenson, 2000). The possible antiviral mechanisms involve either inhibition of proteins essential for viral entry, inhibition of proteins related to polymerase responsible for viral replication and infection, or regulation of cellular pathways, and anti-oxidative pathway (Hassan et al., 2016). ...
... The possible antiviral mechanisms involve either inhibition of proteins essential for viral entry, inhibition of proteins related to polymerase responsible for viral replication and infection, or regulation of cellular pathways, and anti-oxidative pathway (Hassan et al., 2016). Coumarin derivatives such as 4-Hydroxycoumarins, Pyranocoumarins, Furanocoumarin, 3-Phenylcoumarins, 4-Phenylcoumarins, Hybrid coumarin analogue Toddacoumaquinone have all shown potent antiviral effect against HIV infection because they inhibit HIV protease, integrase, reverse transcriptase and viral DNA replication (Hassan et al., 2016;Moore & Stevenson, 2000). A major limitation of the literature on the antiviral effects of coumarins is that these studies have been performed mainly in silico and in vitro. ...
The search for novel and effective drugs is an important challenge, as a severe acute respiratory syndrome caused by a zoonotic coronavirus (SARS-CoV-2) is affecting the entire world population. As of 18th April 2021 there were over 140 million confirmed cases and more than 3
million deaths due to COVID-19. Natural herbal drugs are a rich resource for novel antiviral drug development. Many studies and traditional medical practices have shown their effectiveness against
various human pathogens like the influenza virus, hepatitis C virus, coronavirus and the human immunodeficiency virus. Although modern synthetic drugs based on Western medicine are used in developed countries, traditional plant-based drugs are an integral part of medical treatment, including Sri Lanka. In Sri Lanka, the administration of crude herbal drug formulations dates back more than 3000 years. Numerous studies have shown that natural herbal drugs possess a wide spectrum of biological and pharmacological properties, such as anti-inflammatory, anti-angiogenic and anti-neoplastic. Accordingly, these herbs have been used for centuries in Sri Lankan traditional
medicine to treat various disorders. Despite the potency, none of these herbal medicines has yet been approved as a therapeutic antiviral agent against SARS-CoV-2 due to a lack of data from clinical trials. This review summarizes the current knowledge and future perspectives of the antiviral effects of potent Sri Lankan herbal drugs as potential sources of effective anti-coronavirus therapies.
... Amino acids are joined together by a special type of covalent bond (peptide bond) to form linear structures called polypeptides. The polypeptides are then folded into specific structures forming the functional bioenergetics of protein molecule conformation [28][29][30]. [28]. b) Coronavirus model showing spikes single-handedly leading viral entry into host cells. ...
... These structural rearrangements are thought to initiate an uncoating process, a controlled, targeted release of the genome to the replication site. Early conditions in the viral life cycle, events before a viral genome is inserted into host cell, are susceptible to drugs, including effects on viral attachment to target cells [30], or by meditative production / preservation of a spiritual corona. The epithelium provides the barrier to pathogen invasion. ...
... The identification of new CCR5-targeting antibodies, chemokines, chemokine analogues, small molecules and peptides, is therefore an important step in the development of new antiviral drugs that target virus entry (Doms, 2000) through mechanisms that differ from those of existing HAART drugs. Several different types of inhibitor for CCR5-mediated HIV-1 entry have now been identified and are in pre-clinical or clinical development as drug candidates (De Clercq, 2002;Horuk, 2003;Kazmierski et al., 2003;LaBranche et al., 2001;Michael & Moore, 1999;Moore & Stevenson, 2000;O'Hara & Olson, 2002;Schwarz & Wells, 2002). In particular we focused our attention on D-Ala-peptide T-amide (DAPTA), or Peptide T, named for its high threonine content (ASTTTNYT). ...
... The development of new powerful drugs acting before HIV-1 infection represents a priority, particularly for cells such as M/M whose infection is persistent and productive for long periods of time. HIV-1 cellular entry inhibitors are a promising new class of potential anti-HIV-1/AIDS drugs (De Clercq, 2002;LaBranche et al., 2001;Michael & Moore, 1999;Moore & Stevenson, 2000). By interacting with the viral envelope glycoproteins (gp120 or gp41), with CD4 or with co-receptors, these inhibitors block different steps in the complex sequence of events leading to virus-cell fusion (Cocchi et al., 1995;Koenig et al., 1986;Meucci et al., 1998;Michael & Moore, 1999). ...
... Once the virions penetrate the host cell, the poorly understood process of uncoating occurs. Uncoating or disassembly, an important early phase of HIV-1 replication, is mainly dependent on capsid stability and determines the nuclear entry of the mature PIC (Moore and Stevenson 2000;Matreyek and Engelman 2013a). The process results in the release of viral RNA from the capsid core into the cytoplasm, where the RNA is reverse transcribed within the reverse transcription complex (RTC) (Fig. 1) (Moore and Stevenson 2000). ...
... Uncoating or disassembly, an important early phase of HIV-1 replication, is mainly dependent on capsid stability and determines the nuclear entry of the mature PIC (Moore and Stevenson 2000;Matreyek and Engelman 2013a). The process results in the release of viral RNA from the capsid core into the cytoplasm, where the RNA is reverse transcribed within the reverse transcription complex (RTC) (Fig. 1) (Moore and Stevenson 2000). Upon uncoating, the viral capsid and nucleocapsid, along with the viral reverse transcripts, reverse transcriptase (RT), IN, protease, and viral accessory proteins Vif, Nef, and Vpr, collectively called the RTC, are released. ...
Retroviruses must integrate their cDNA into the host genome to generate proviruses. Viral DNA-protein complexes interact with cellular proteins and produce pre-integration complexes, which carry the viral genome and cross the nuclear pore channel to enter the nucleus and integrate viral DNA into host chromosomal DNA. If the reverse transcripts fail to integrate, linear or circular DNA species such as 1- and 2-long terminal repeats are generated. Such complexes encounter numerous cellular proteins in the cytoplasm, which restrict viral infection and protect the nucleus. To overcome host cell defenses, the pathogens have evolved several evasion strategies. Viral proteins often contain nuclear localization signals, allowing entry into the nucleus. Among more than 1000 proteins identified as required for HIV infection by RNA interference screening, karyopherins, cleavage and polyadenylation specific factor 6, and nucleoporins have been predominantly studied. This review discusses current opinions about the synergistic relationship between the viral and cellular factors involved in nuclear import, with focus on the unveiled mysteries of the host-pathogen interaction, and highlights novel approaches to pinpoint therapeutic targets.
... A new class of anti-HIV-1 drugs known as entry or fusion inhibitors are under clinical development [192,193]. T20 (enfuvirtide, Trimeris, Durham, NC) is a fusion inhibitor and has now been licensed by the Food and Drug Administration. This is a 36mer synthetic peptide corresponding to the overlapping regions within HR2 [194] of Env gp41 and exerts its antiviral activity by interacting with a target sequence within HR1 that inhibits association with native HR2. ...
... There is a growing number of a new class of anti-HIV-1 drugs known variously as entry or fusion inhibitors under clinical development [192,193]. T20 (enfuvirtide) from Trimeris (Durham, NC) has now been licensed by the Food and Drug administration. It is a 36-mer synthetic peptide corresponding to overlapping regions within HR2 [194], which exerts its antiviral activity by interacting with a target sequence within HR1 that inhibits association with native HR2. ...
... Host-virus interactions are attractive to explore for the development of novel anti-HIV-1 strategies, as many steps of the viral replication involve an intricate interplay between the virus and the host machinery (Moore & Stevenson, 2000;Rowland-Jones et al., 2001). Given the apparent paradox between the minimalist nature of the retroviral genome and the complexity of the HIV-1 lifecycle, it is essential that the virus utilizes the host machinery both to promote its replication and, at the same time, to subvert and evade the antiviral responses of the cell (Freed, 2004;Ott, 2002;Popik & Pitha, 2000;Stevenson, 2003). ...
... SCIENTIFIC REVIEW 1 2 EJBM, Copyright © 2006 HIV-1 Dynamics in the Host Cell contributing both to propagation of the virus, and to cellular defense has been identified in the past couple of years, and paints a fascinating picture of the convoluted relationship that has evolved between the virus and the invaded cell. Clear understanding of cellular and viral contributors to this interplay will not only provide insights into the mechanism of various steps of retroviral replication, but will also likely lead to the development of novel therapeutic strategies to specifically disrupt virus-host protein interactions (Greene & Peterlin, 2002;Moore & Stevenson, 2000;Tang et al., 2002). ...
HIV-1, the causative agent of AIDS, is a sophisticated retrovirus that has both evolved to invade the complex human immune system and adapted to utilize the host machinery for its own propagation. A dynamic interac-tion between the virus and host systems can be observed at every step of the HIV-1 lifecycle. Host factors are involved not only in mounting antiviral responses, but are also hijacked by the virus to enhance viral replication. Host factors are necessary for viral replication during entry, reverse transcription, nuclear import, integration, transcription, nuclear export, translation, assembly, and budding. Recently, a new class of host factors, called "host restriction factors," has been identified that prevent retroviral replication in a specific host cell environment and constitute an important part of intracellular innate immunity against the virus. These restriction factors act as barriers to retroviral replication at various stages within the infected cell. Nevertheless, the HIV-1 virus has learned to subvert these antiviral responses and successfully propagate within the permissive host environment. This review article describes the identification and mechanism of action of several pro-and anti-HIV-1 host factors. It is likely that we are only beginning to get a glimpse of an ongoing complex battle between HIV-1 and the host, the understanding of which should provide valuable information for the development of novel therapeutic strategies against HIV-1.
... In addition, a virucidal test (which measures the efficacy of virucidal disinfectants) proved the antiviral activity (Lazreg Aref et al., 2011). Thus, developing viral entry inhibitors that can be utilized as innovative antivirus medicines to suppressing the replication of ADV, ECV-11, and HSV-1 and this step essential because it allow to the virion to penetrates the host cell (Lin et al., 2002;Moore & Stevenson, 2000). (Najjari et al., 2015). ...
Many studies have been published about the chemical compounds produced by Ficus carica Linn. and benefits toward the health. F. carica used since ancient time and widely for medicinal purpose, the leaves decoction was consumed as a tea. The benefits of F. carica components are still under investigation by many researchers around the globe. This review provides a summary of the constituents of the chemical compounds and toxicity studies, clinical studies and biological activities conducted on F. carica fruit, leaves, latex, bark, and root. Approximately 125 biochemical compounds of Ficus carica Linn were identified and classified under eight categories: triterpenoids, volatile ingredients, coumarins, furanocoumarins, flavonoids, hydroxybenzoic acids, hydroxycinnamic acids, as well as miscellaneous. Numerous scientific studies have demonstrated its antimicrobial, anticholinesterase, anti-diabetic, hepatoprotective, renoprotective, antioxidant, anti-inflammatory, and anticancer properties. We know our review will be a valuable for those looking for scientific evidence resource that support F. carica leaves medicinal properties, as well as the research gaps that need to be filled to enhance the economic value and medical benefits of the F. carica leaf. In this review, extensive literature research was conducted to reveal the benefits of F. carica for human health.
... Anti-HIV activity has been evaluated for chromenes such as warfarin, khellactone (Fig. 4), a furanocoumarin, etc. They were found to inhibit reverse transcriptase, integrase, and protease as well as to arrest cell cycle [50,51]. ...
Chromene is a naturally abundant heterocyclic compound found in alkaloids, tocopherols, terpenes and other compounds. Its derivatives can be used as a scaffold that exhibits pharmacological activity in the human body. Chromene drugs and related bioactive molecules are the prime focus of this reference. It presents 13 thoroughly researched chapters that comprehensively cover all aspects about the molecule. Starting with a detailed introduction to its role and importance in drug discovery, the book goes into the details of chromene structure, synthesis and pharmacology. Readers can gain knowledge of different commercial medicines based on chromene and its pharmacological activity against different diseases. The elaborate topics in the book will help researchers working on chromene based drugs.
Key highlights of the book include:
- Complete coverage of chromene's role in nature and drug development with references to historical background and current developments
- References to commercial and preclinical drugs and patents of interest
- Explanation of chromene bioacivity in different diseases (antioxidant, antidiabetic, antinflammatory, antibacterial and antifungal activities, antitumour, immunomodulatory activity)
- Explanation of chromene activity against SARS-Cov2
... There is another advantage regarding the mechanism of action of AFSMs, i.e., the targeting of several steps in the virus life cycle. For instance, the anti-HIV targets several steps in the virus life cycle, including virushost cell attachment, cell membrane fusion, integration, and assembly, besides the conventional targets like inhibition of the reverse transcriptase, protease, and integrase (Moore and Stevenson, 2000). Another example of the wide spectrum bioactivity of FSMs comes from the endophytic fungi, which has a huge number of bioactive compounds of pharmaceutical importance viz., antitumor, antibiotic, neuroprotective, antioxidant, anti-inflammatory, antiviral, and immunomodulatory agents, etc. (Agrawal et al., 2019;Deshmukh et al., 2017). ...
Profound inspection of the life forms on the earth teaches how to be the complexity of interrelationships among the various systems. Because of the emergence of novel viruses all the time and the inadequate of vaccines and antivirals, viral contagions are amongst the most causative diseases affecting people worldwide. Fungi exemplify a massive source of bioactive molecules as, many fungal secondary metabolities like Oxoglyantrypine, Carneic acid F, Scedapin C, Asteltoxin E, Phomanolide, Norquinadoline A and Quinadoline B have antiviral activity. This review deals with how secondary metabolites of fungi can help in the war against viruses in general and especially Coronaviruses moreover several pieces of literature pointed out that many clusters of fungi in different biotopes are waiting to be exploited.
... Concerning this potential to discover new antiviral drugs, the use of ML techniques has shown important applications in the field of medicinal chemistry, such as studies on the prediction of HIV-1 entry inhibitors from an RNA-based approach with DL and molecular modeling [60]. Furthermore, ML can be applied against many relevant viruses, considering its potential drug targets ( Figure 2), for example, EBOV [61][62][63], DENV/ ZIKV [64][65][66], HCV [66][67][68][69], HIV [69][70][71][72] and SARS-CoV-2 [73][74][75][76][77]. Likewise, ML can still be widely used for the identification and the design of new inhibitors and drug repurposing from old and novel databases, especially in emergency scenarios such as the SARS-CoV-2 pandemic [32,33,58,78]. ...
Introduction: Drug design and discovery of new antivirals will always be extremely important in medicinal chemistry, taking into account known and new viral diseases that are yet to come. Although machine learning (ML) have shown to improve predictions on the biological potential of chemicals and accelerate the discovery of drugs over the past decade, new methods and their combinations have improved their performance and established promising perspectives regarding ML in the search for new antivirals.
Areas covered: The authors consider some interesting areas that deal with different ML techniques applied to antivirals. Recent innovative studies on ML and antivirals were selected and analyzed in detail. Also, the authors provide a brief look at the past to the present to detect advances and bottlenecks in the area.
Expert opinion: From classical ML techniques, it was possible to boost the searches for antivirals. However, from the emergence of new algorithms and the improvement in old approaches, promising results will be achieved every day, as we have observed in the case of SARS CoV-2. Recent experience has shown that it is possible to use ML to discover new antiviral candidates from virtual screening and drug repurposing.
... Currently, anti-HIV approaches are to target several steps in virus life cycle including virus-host cell attachment, cell membrane fusion, integration, assembly besides the conventional target like inhibition of the reverse transcriptase, protease, integrase [45]. Chemical compound coumarins have been shown from many research studies to have anti-HIV effects. ...
Viral infections are responsible for many illnesses, and recent outbreaks have raised public health concerns. Despite the availability of many antiviral drugs, they are often unsuccessful due to the generation of viral mutants and less effective against their target virus. Identifying novel antiviral drugs is therefore of critical importance and natural products are an excellent source for such discoveries. Coumarin is one such natural compound that is a potential drug candidate owing to its properties of stability, solubility, and low toxicity. There are numerous evidences showing its inhibitory role against infection of various viruses such as HIV, Influenza, Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16). The mechanisms involve either inhibition of proteins essential for viral entry, replication and infection or regulation of cellular pathways such as Akt-Mtor (mammalian target of rapamycin), NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), and anti-oxidative pathway including NrF-2 (The nuclear factor erythroid 2 (NFE2)-related factor 2). This review summarizes the present state of understanding with a focus on coumarin's antiviral effect and their possible molecular mechanisms against Influenza virus, HIV, Hepatitis virus, Dengue virus and Chikungunya virus.
... It is worth mentioning that many side effects of such drugs can appear as a consequence of a hard HIV-case, which is why differential diagnostic between side effects and HIV complications can be difficult [121]. Moreover, new drug-resistant mutant HIV strains and their transmission simulate new researches in this area in order to develop new classes of drugs against HIV [122,123] . We will discuss the main results in this research area where fullerene derivatives with amino acids and peptides were used. ...
Fullerene derivatives with amino acids, peptides and proteins have wide perspectives in biomedical applications. Thus, development and up-scaling of synthesis procedures, as well as investigation of the physico-chemical and biological properties of these derivatives, are extremely important. The present paper systematizes the current literature data on synthesis, physico-chemical properties and application of fullerene derivatives with amino acids, peptides and proteins in biomedicine. Experimental and theoretical data presented in the review give a comprehensive overview of these substances and can be valuable for specialists in the fields of nanotechnology, nanomaterials and bionanomedicine.
... The co-receptors that are targeted belongs to a 7 transmembrane GPCR and bind to the chemotactic chemokines that produce cell signals and continue the immune response further. The selectivity of HIV-1 to bind to specific co-receptor determines its tropism that is if HIV-1 binds to CCR5 co-receptor it is known as R5 Tropic HIV-1 if it binds to CXCR 4 co-receptor it is called as X4 Tropic HIV-1 and a Dual-Tropic HIV if it proceeds through both CCR5/CXCR4 co-receptor [15]. The agents that act upon CCR5 are RANTES, MIP-1a, and MIP-1b, Maraviroc, Aplaviroc, Vicriviroc, Cenicriviroc, Nifeviroc (Fig. 5.) [16e18]. ...
The healthcare system faces various challenges in human immunodeficiency virus (HIV) therapy due to resistance to Anti-Retroviral Therapy (ART) as a consequence of the evolutionary process. Despite the success of antiretroviral drugs like Zidovudine, Zalcitabine, Raltegravir WHO ranks HIV as one of the deadliest diseases with a mortality of one million lives in 2016. Thus, there emerges an urgency of developing a novel anti-retroviral agent that combat resistant HIV strains. The clinical development of ART from a single drug regimen to current triple drug combination is very slow. The progression in the structural biology of the viral envelope prompted the discovery of novel targets, which can be demonstrated a proficient approach for drug design of anti-retroviral agents. The current review enlightens the recent updates in the structural biology of the viral envelope and focuses on CCR5 as a validated target as well as ways to overcome CCR5 resistance. The article also throws light on the SAR studies and most prevalent mutations in the receptor for designing CCR5 antagonists that can combat HIV-1 infection. To conclude, the paper lists diversified scaffolds that are in pipeline by various pharmaceutical companies that could provide an aid for developing novel CCR5 antagonists.
... However, escape pathways for these compounds also need to be meticulously explored to exclude changes in the host cell repertoire and unfavorable alterations in viral fitness. Thus far only few studies have been dedicated to study escape from CD4 mimicking and soluble compounds [153,154], with more effort defining escape from CD4bs specific Abs elucidating fitness costs associated with escape [155]. ...
A hallmark of HIV-1 infection is the continuously declining number of the virus’ predominant target cells, activated CD4⁺ T cells. With diminishing CD4⁺ T cell levels, the capacity to utilize alternate cell types and receptors, including cells that express low CD4 receptor levels such as macrophages, thus becomes crucial. To explore evolutionary paths that allow HIV-1 to acquire a wider host cell range by infecting cells with lower CD4 levels, we dissected the evolution of the envelope-CD4 interaction under in vitro culture conditions that mimicked the decline of CD4high target cells, using a prototypic subtype B, R5-tropic strain. Adaptation to CD4low targets proved to severely alter envelope functions including trimer opening as indicated by a higher affinity to CD4 and loss in shielding against neutralizing antibodies. We observed a strikingly decreased infectivity on CD4high target cells, but sustained infectivity on CD4low targets, including macrophages. Intriguingly, the adaptation to CD4low targets altered the kinetic of the entry process, leading to rapid CD4 engagement and an extended transition time between CD4 and CCR5 binding during entry. This phenotype was also observed for certain central nervous system (CNS) derived macrophage-tropic viruses, highlighting that the functional perturbation we defined upon in vitro adaptation to CD4low targets occurs in vivo. Collectively, our findings suggest that CD4low adapted envelopes may exhibit severe deficiencies in entry fitness and shielding early in their evolution. Considering this, adaptation to CD4low targets may preferentially occur in a sheltered and immune-privileged environment such as the CNS to allow fitness restoring compensatory mutations to occur.
... One option to overcome the problem is to explore new therapies that include the study of the viral cDNA integration dynamics of human Lentiviruses. It would permit to understand the underpinnings behinds of alterations of cellular homeostasis when a cell is infected (Moore, 2000). Additionally, analysis of integration process is important in HIV-induced disease, in Lentivirus-based gene therapy and new therapeutic options actually developed (Saayman, et al, 2015;Cereseto y Giacca, 2004). ...
p> Introducción : La distribución del DNAc lentiviral en el genoma hospedero ha sido estudiada usando un enfoque estructural, sin embargo éste es incompleto pues no considera la dinámica y la topología de la cromatina interfásica y las redes de expresión de genes en la célula infectada.
Objetivo . Utilizando un enfoque no linear, correlacionar la multifractalidad de los cromosomas humanos con la composición y el disturbio de la topología de la cromatina como un efecto complejo promovido por la integración de ADNc lentiviral.
Métodos. De 2.409 secuencias genómicas obtenidas del GeneBank y flanqueantes al 5’LTR de lentivirus humanos, (cobertura mayor del 98,6% del genoma humano), se correlacionaron con los valores de multifractalidad (AvΔDq) de la cromatina humana. Adicionalmente se empleó el programa Cytoscape v.2.63 para simular computacionalmente los efectos de la integración sobre las redes de expresión de genes humanos.
Resultados. El 54,21% de la integración lentiviral ocurrió en aquellos cromosomas con valores altos e intermedios de multifractalidad; el 18.14% de estas integraciones se localizo en los cromosomas con más altos valores de multifractalidad (16, 17, 19, 22). La multifractalidad se correlacionó con el porcentaje Alu. Se registraron 2.770 interacciones entre 28 genes localizados cerca de provirus VIH-1 en macrófagos humanos. La integración del DNAc lentiviral alteró dramáticamente, la topología de la red de expresión de genes en macrófagos.
Conclusión . Algunos cambios topológicos asociados a las regiones con elevada frecuencia de integración del ADNc, podrían, de manera sinérgica, reconfigurar localmente la topología del ambiente cromatínica que las redes de expresión de genes en la célula infectada. © 2016. Acad. Colomb. Cienc. Ex. Fis. Nat.</p
... The reverse transcriptase (RT) of HIV-1 has been an important target for the design of anti-HIV drug and two main classes of RT inhibitors (nucleoside and non-nucleoside) have been used in clinic (Jonckheere et al. 2000;Moore and Stevenson 2000). NNRTIs, different from NRTIs, have a definitive place in clinical treatment of AIDS because of their low toxicity, high potency and good selectivity (Tronchet and Seman 2003). ...
The purpose of this study was to characterize the disposition, distribution, excretion and plasma protein binding of 6-benzyl-1-benzyloxymethyl-5-iodouracil (W-1) in rats. Concentrations of W-1 within biological samples were determined using a validated high performance liquid chromatography method. The plasma protein binding of W-1 was examined by equilibrium dialysis method. After oral administration of W-1 (50, 100 and 200 mg/kg, respectively) in self-microemulsifying drug delivery system formulation, the pharmacokinetic parameters of W-1 were as follows: the peak plasma concentrations (C
max) were 0.42, 1.50 and 2.55 μg/mL, the area under the curve (AUC0−t) were 0.89, 2.27 and 3.96 µg/h mL and the plasma half-life (t
1/2) were 5.15, 3.77 and 3.77 h, respectively. Moreover, the prototype of W-1 was rapidly and extensively distributed into fifteen tissues, especially higher concentrations were detected in intestine, stomach and liver, respectively. The plasma protein binding of W-1 in rat, beagle dog and human were in the range of 97.96–99.13 %. This study suggested that W-1 has an appropriate pharmacokinetics in rats, such as rapid absorption, moderate clearance, and rapid distribution to multiple tissues. Those properties provide important information for further development W-1 as an anti-HIV-1 drug candidate.
... H uman immunodeficiency type 1 virus (HIV-1) reverse transcriptase (RT) plays an essential role in the HIV-1 life cycle by converting a single-strand viral RNA into a double-stranded proviral DNA via its polymerase and RNase H activities (1). Therefore, inhibition of reverse transcriptase has been one of the primary therapeutic strategies for developing antiviral agents to suppress the replication of HIV-1 (2,3). There are two classes of RT inhibitors: one is the nucleoside reverse transcriptase inhibitors (NRTIs), which are active-site inhibitors, such as AZT and 3TC, and the other is nonnucleoside reverse transcriptase inhibitors (NNRTIs), which are non-active-site competitive inhibitors, such as efavirenz (EFV), nevirapine (NVP), etravirine (ETR), and rilpivirine (RPV). ...
... Specifically, the V1/V2 loops on HIV-1 gp120 can influence co-receptor usage but not as efficiently as the V3 domain [19][20][21]. Differential interaction with the co-receptors may be related to the higher negative charge of the second extracellular loop of CXCR4 compared to that of CCR5, which may in turn favor binding to a more positively charged gp120 V3 loop [22,23]. Several algorithms/models have been developed to predict HIV-1 co-receptor usage from the amino sequence in Env. ...
Background:
CCR5-using (r5) HIV-1 predominates during asymptomatic disease followed by occasional emergence of CXCR4-using (x4) or dual tropic (r5x4) virus. We examined the contribution of the x4 and r5 components to replicative fitness of HIV-1 isolates.
Methods:
Dual tropic r5x4 viruses were predicted from average HIV-1 env sequences of two primary subtype C HIV-1 isolates (C19 and C27) and from two patient plasma samples (B12 and B19). Chimeric Env viruses with an NL4-3 backbone were constructed from the B12 and B19 env sequences. To determine replicative fitness, these primary and chimeric dual tropic HIV-1 were then competed against HIV-1 reference isolates in U87.CD4 cells expressing CXCR4 or CCR5 or in PBMCs ± entry inhibitors. Contribution of the x4 and r5 clones within the quasispecies of these chimeric or primary HIV-1 isolates were then compared to the frequency of x4, r5, and dual tropic clones within the quasispecies as predicted by phenotypic assays, clonal sequencing, and 454 deep sequencing.
Results:
In the primary HIV-1 isolates (C19 and C27), subtype C dual tropic clones dominated over x4 clones while pure r5 clones were absent. In two subtype B chimeric viruses (B12 and B19), r5 clones were >100-fold more abundant than x4 or r5/x4 clones. The dual tropic C19 and C27 HIV-1 isolates outcompeted r5 primary HIV-1 isolates, B2 and C3 in PBMCs. When AMD3100 was added or when only U87.CD4.CCR5 cells were used, the B2 and C3 reference viruses now out-competed the r5 component of the dual tropic C19 and C27. In contrast, the same replicative fitness was observed with dualtropic B12 and B19 HIV-1 isolates relative to x4 HIV-1 A8 and E6 or the r5 B2 and C3 viruses, even when the r5 or x4 component was inhibited by maraviroc (or AMD3100) or in U87.CD4.CXCR4 (or CCR5) cells.
Conclusions:
In the dual tropic HIV-1 isolates, the x4 replicative fitness is higher than r5 clones but the x4 or x4/r5 clones are typically at low frequency in the intrapatient virus population. Ex vivo HIV propagation promotes outgrowth of the x4 clones and provides an over-estimate of x4 dominance in replicative fitness within dual tropic viruses.
... This is very interesting because human cyclophilins A and B are host cell proteins that bind specifically to the HIV-1 Gag polyprotein p55 gag in vitro and druginduced reductions in virion-associated cyclophilin A levels have been shown to be accompanied by reductions in HIV-1 virion infectivity, indicating that the association is functionally relevant for HIV-1 infectivity [26,27]. Based on the findings that cyclophilins are important for viral capsid assembly, cyclophilins are as such considered drugable targets in antiviral therapy [28,29]. Other studies that lend support to the therapeutic potential of P. alliacea against HIV-1/AIDS is the fact that this plant is credited for having immunomodulatory properties [21,30]. ...
... The three extracellular domains of the receptor are glycosylated and contain four highly conserved cysteine moieties, which form disulphide bonds that stabilize the receptor within the membrane (Figure 1.7 A and B). Moore and Stevenson have elucidated the subtle differences in charge between the surfaces of the two coreceptors, CCR5 has a neutral charge, as opposed to the negatively charged CXCR4 [214]. Despite this low homogeneity between the two major coreceptors, dual tropic viruses can use both CXCR4 and CCR5 relatively efficiently [80,215]. ...
... Therefore, targeting a host factor might require very elaborated modes of action of the inhibitor [265] (discussed in the next subsection), that selectively block the virus-host factor interaction/-or response, but allow the host protein to perform essential host-related functions. Although both viral and cellular factors can be targeted, viral factors should optimally be 'knocked-out', while, if a host protein is targeted, a detailed knowledge about the various protein functions is required in order to circumvent toxicity [266]. The mode of action of a drug that targets a host protein would optimally be selective for the specific interaction that is required by the virus. ...
... The theory of total relative net charge of the V3 peptide may be explained by the fact that charge directly influences the molecular structure or binding capability of viral gp120 [73]. CXCR4 has been shown to be more negatively charged on the surface than CCR5 [245]; therefore, CXCR4-utilizing virus might also have a more positively charged V3 than CCR5-utilizing virus. The net charge rule has exhibited high specificity; however, the sensitivity in defining X4 virus has remained low [74,246]. ...
The evolution of human immunodeficiency virus type 1 (HIV-1) with respect to co-receptor utilization has been shown to be relevant to HIV-1 pathogenesis and disease.The CCR5-utilizing (R5) virus has been shown to be important in the very early stages of transmission and highly prevalent during asymptomatic infection and chronic disease.In addition, the R5 virus has been proposed to be involved in neuroinvasion and central nervous system (CNS) disease.In contrast, the CXCR4-utilizing (X4) virus is more prevalent during the course of disease progression and concurrent with the loss of CD4+Tcells.The dual-tropic virus is able to utilize both co-receptors (CXCR4 and CCR5) and has been thought to represent an intermediate transitional virus that possesses properties of both X4 and R5 viruses that can be encountered at many stages of disease. The use of computationaltools and bioinformatic approaches in the prediction of HIV-1 co-receptor usage has been growing in importance with respect to understanding HIV-1 pathogenesis and disease, developingdiagnostic tools,and improving the efficacy of therapeutic strategies focused on blocking viral entry.Current strategies have enhanced the sensitivity, specificity, and reproducibility relative to the prediction of co-receptor use; however, these technologies need to be improved with respect to their efficient and accurate use across the HIV-1 subtypes. The most effective approach may center on the combined use of different algorithms involving sequences within and outside of the env-V3 loop. This review focuses on the HIV-1 entry process and on co-receptor utilization, including bioinformatic tools utilized in the prediction of co-receptor usage. It also provides novel preliminary analyses for enabling identification of linkages between amino acids in V3 with other components of the HIV-1 genome and demonstrates that these linkages are different between X4 and R5 viruses.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
Structure-based (SBDD) and ligand-based (LBDD) drug design are extremely important and active areas of research in both the academic and commercial realms. This book provides a complete snapshot of the field of computer-aided drug design and associated experimental approaches. Topics covered include X-ray crystallography, NMR, fragment-based drug design, free energy methods, docking and scoring, linear-scaling quantum calculations, QSAR, pharmacophore methods, computational ADME-Tox, and drug discovery case studies. A variety of authors from academic and commercial institutions all over the world have contributed to this book, which is illustrated with more than 200 images. This is the only book to cover the subject of structure and ligand-based drug design, and it provides the most up-to-date information on a wide range of topics for the practising computational chemist, medicinal chemist, or structural biologist. Professor Kenneth Merz has been selected as the recipient of the 2010 ACS Award for Computers in Chemical & Pharmaceutical Research that recognizes the advances he has made in the use of quantum mechanics to solve biological and drug discovery problems.
A clear and precise report on synthetic methods for INSTIs and their intermediates are provided in the present work. HIV Integrase strand transfer inhibitors (INSTIs), a class of antiretroviral agents employed to treat HIV infected patients are placed as the second option of treatment after nucleosides. As INSTIs are employed as first line therapy to newly infected HIV positive individuals, thus synthetic routes must be easily accessible to the medicinal chemists towards lead optimization or process development. The current perspective elaborates synthetic routes of first to next generation INSTIs investigated in two decades of research and their development efforts. Further, drug resistance occurred by mutations against usage of INSTI drugs with respect to their generation also discussed. Later, discussion about synthetic development and investigation of next generation INSTIs against drug resistance HIV infections also covers to fill the gap between first/second generation INSTIs. The current perspective will draw attention of medicinal chemists and multi‐disciplinary researchers in HIV drug discovery.
Accounts in Drug Discovery describes recent case studies in medicinal chemistry with a particular emphasis on how the inevitable problems that arise during any project can be surmounted or overcome. The Editors cover a wide range of therapeutic areas and medicinal chemistry strategies, including lead optimization starting from high throughput screening "hits" as well as rational, structure-based design. The chapters include "follow-ons" and "next generation" compounds that aim to improve upon first generation agents. This volume surveys the range of challenges commonly faced by medicinal chemistry researchers, including the optimization of metabolism and pharmacokinetics, toxicology, pharmaceutics and pharmacology, including proof of concept in the clinic for novel biological targets. The case studies include medicinal chemistry stories on recently approved and marketed drugs, but also chronicle "near-misses", i.e., exemplary compounds that may have proceeded well into the clinic but for various reasons did not result in a successful registration. As the vast majority of projects fail prior to registration, much can be learned from such narratives. By sharing a wide range of drug discovery experiences and information across the community of medicinal chemists in both industry and academia, we believe that these accounts will provide insights into the art of medicinal chemistry as it is currently practiced and will help to serve the needs of active medicinal chemists.
Natural Product Chemistry for Drug Discovery provides a comprehensive summary of where natural product chemistry is today in drug discovery. The book covers emerging technologies and case studies and is a source of up-to-date information on the topical subject of natural products. The authors, all experts in their respective fields, provide compelling arguments as to why naturel products should be considered important tools in the drug discovery process. The book will appeal across the board from scientists to professionals, postgraduates and industrial chemists. The case studies selected for inclusion highlight recently marketed drugs and development candidates that have been derived from natural products. These 'real-life' examples show how new technologies, such as advances in screening, isolation, dereplication and prefractionation, have significantly enhanced the discovery process.
A novel high-throughput strand transfer assay has been developed, using Microarray Compound Screening (μARCS) technology, to identify inhibitors of human immunodeficiency virus (HIV) integrase. This technology utilizes agarose matrices to introduce a majority of the reagents throughout the assay. Integration of biotinylated donor DNA with fluorescein isothiocyanate (FITC)-labeled target DNA occurs on a SAM membrane in the presence of integrase. An anti-FITC antibody conjugated to alkaline phosphatase (AP) was used to do an enzyme-linked immunosorbent assay with the SAM. An agarose gel containing AttoPhos, a substrate of AP, was used for detection of the integrase reactions on the SAM. For detection, the AttoPhos gel was separated from the SAM after incubation and then the gel was imaged using an Eagle Eye II closed-circuit device camera system. Potential integrase inhibitors appear as dark spots on the gel image. A library of approximately 250,000 compounds was screened using this HIV integrase strand transfer assay in μARCS format. Compounds from different structural classes were identified in this assay as novel integrase inhibitors.
Background:
Human immunodeficiency virus (HIV) is an infective microorganism that causes an acquired immunodeficiency syndrome (AIDS). Therefore, the rational design of inhibitors for preventing the progression of the disease is required.
Objective:
This study aims to construct quantitative structure-activity relationship (QSAR) models, molecular docking and newly design of colchicine and derivatives with anti-HIV activity.
Method:
A data set of 24 colchicine and derivatives with anti-HIV activity were employed to develop QSAR models using machine learning methods (e.g. multiple linear regression (MLR), artificial neural network (ANN) and support vector machine (SVM)), and to study a molecular docking.
Results:
The significant descriptors relating to the anti-HIV activity included JGI2, Mor24u, Gm and R8p+ descriptors. The predictive performance of the models gave acceptable statistical qualities as observed by correlation coefficient (Q2) and root mean square error (RMSE) of leave-one out cross-validation (LOO-CV) and external sets. Particularly, the ANN method outperformed MLR and SVM methods that displayed and RMSELOO-CV of 0.7548 and 0.5735 for LOO-CV set, and of 0.8553 and RMSEExt of 0.6999 for external validation. In addition, the molecular docking of virus-entry molecule (gp120 envelope glycoprotein) revealed the key interacting residues of the protein (cellular receptor, CD4) and the site-moiety preferences of colchicine derivatives as HIV entry inhibitors for binding to HIV structure. Furthermore, newly rational design of colchicine derivatives using informative QSAR and molecular docking was proposed.
Conclusion:
These findings serve as a guideline for the rational drug design as well as potential development of novel anti-HIV agents.
Biscoumarin derivatives, a dimeric form of coumarin, are well known derivatives of coumarin, occurred in the bioactive metabolites of marine and terrestrial organisms. On account of pharmacological and biological applications, biscoumarins have long been the subject of innumerable enzyme inhibition studies. In this review the pros and cons of enzyme inhibition studies of biscoumarins as urease inhibitors, aromatase inhibitors, NPPs, α-glucosidase inhibitors, α-amylase inhibitors, HIV-1 integrase inhibition, steroid sulfatase inhibitors and c-Met inhibitors are discussed in a systematic way. Moreover, the review discusses the structure activity relationship of biscoumarin scaffold with enzyme inhibitory potency which would unleash new avenues for further development. The purpose of the current review is to disclose the value of biscoumarins as potent and efficient enzyme inhibitor. This review provides a guideline to elaborate the diversity of biscoumarin inhibitors by exploring the effects of electronic groups linked with biscoumarin nucleus.
Understanding of human immunodeficiency virus (HIV), productive viral entry, and its inhibition helps elucidate viral pathogenesis and further develop therapeutics aiming to block HIV entry. In this thesis, we focus on the cellular pathways that lead to productive infection and mechanisms of its inhibition by membrane-impermeable fusion inhibitors, using fluorescently-labeled HIV as an important tool. Although there have been many studies using fluorescently-labeled virions, understanding of their features in terms of infectivity, labeling efficiency, or intensity profiles has been limited. Our study characterizing fluorescently-labeled HIV-1 give us better understanding of HIV-1 and interpretation of data when using virions for mechanistic studies. Using the characterized HIV-1, we investigated entry pathways that lead to productive HIV-1 infection by seeking the potential correlation between the inhibition of cell endocytosis and the inhibition of HIV-1 infection. The results from different cell lines with various inhibitors blocking endocytosis suggest that endocytosis can indeed lead to productive infection, as revealed by the specific inhibition of HIV-1 infection by dynamin I K44A mutant. However, endocytosis may not be the only productive pathway for HIV-1 infection because all inhibition data that we have observed appear to be partial, which is in contrast to the inhibition by T20. For both antibodies and T20, HIV-1 infection can be blocked close to 100%, indicating that these drugs are efficacious enough although HIV can establish productive infection through endocytosis. These results also demonstrate that endocytosed virions need to fuse with endosomes for productive infection. The conclusion that endocytosis can initiate productive infection of HIV-1 led us to investigate whether the presence of endocytic entry may reduce T20 efficacy by allowing virus to escape from this membrane impermeable drug. To test this hypothesis, we examined the effect of T20 on HIV-1 internalization and the impact of endocytosis on T20 efficacy. These experiments show that endocytosis has no apparent effect on T20 efficacy, suggesting that endocytosis does not offer measurable advantage for the virus to escape from membrane-impermeable T20. Taken together, these studies suggest that endocytosis contributes to the productive entry of HIV-1, however, the efficacy of T20 is not affected by viral endocytosis.
Ideal Drug Target HIV-1 gp41Structure-Based Drug Design of SifuvirtideHigh Potency of SifuvirtideLimited Drug ResistanceEnhancement of the Efficiency of Sifuvirtide by Biomembrane SelectivityPharmacokinetics of Sifuvirtide with Long Half-LifeStratification of Monotherapy20 mg Sifuvirtide Once Daily vs. 100 mg T20 Twice DailyConclusions and Discussion
The human CCR5, a subfamily of G-protein-coupled, seven-transmembrane-domain cell-surface chemokine receptors that binds to β-chemokine, was heterologously expressed in fission yeast, Schizosaccharomyces pombe, through CCR5-GST fusion protein. The CCR5-GST fusion protein was driven by the full-length nmt1 promoter (Pnmt1) derived from S. pombe. The transcription level of CCR5-GST fusion protein was very high when induced by deprivation of thiamine in the media. About 200 μg of highly purified CCR5-GST fusion protein was obtained from 3 g of wet cell paste (one liter of cell culture). The SDS-PAGE and western blot analysis indicated that the human membrane protein was efficiently expressed and purified in fission yeast.
Interactions between human and viral proteins have proved to be the major cause of several critical ailments and research directions in the recent past have focused on predicting potential viralhost protein relations through computational techniques. This research aimed at detecting probable interactions between HIV-1 and human proteins by generating all possible high -confident (>80%) associations between the host and viral protein and utilizing the association rules to predict new interactions. The FP-Growth algorithm was analyzed and found to evolve the exhaustive set of high confidence association rules that were mined further to isolate probable and significant HIV1-Human predictions with improved accuracy, sensitivity and specificity compared to previous work. The identified HIV1-Human protein interactions were further investigated using Gene Ontology based and DAVID functional annotation tool to establish their biological and therapeutic merits. The superiority of the proposed approach to previously applied computational techniques has been discussed. AIDS is one of the most dreaded diseases and we believe the proposed approach and the predicted interactions would be instrumental in expediting biological and molecular researchers towards formulating drugs for AIDS therapy and the biological functionality of the predicted interactions would enable timely diagnosis of the presence of the infectious viral protein and its replication in the host.
Residing at the interface between innate and adaptative immunity, dendritic cells (DC), and particularly Langerhans cells (LC) of epidermis and epithelia and DC of dermis or lamina propria (DDC), play a key role in the initiation of immune responses. In a first time, we analyzed the main phenotypic and functional characteristics of freshly isolated human dermal DC, as they were still barely studied contrary to human LC. We focused especially on the expression of innate receptors such as Toll Like Receptors (TLR) and C-type lectins. In parallel, TLR expression was also assessed in freshly isolated human LC. Thus, by their differential expression of innate receptors, LC and DDC would play each a specific role in cutaneous and mucosal immunity. Notably, within genital mucosa, they contribute to the transmission of HIV infection. Therefore, in a second time, we examined the early events in HIV entry into the vaginal mucosa and the precise role of LC in this transmission. For that purpose, we developed an in vitro model of vaginal mucosa, using human primary vaginal cells, in which LC could be integrated. In conclusion, we provided here a better characterisation of human LC and DDC as well as their potential function in peripheral immunity that should be useful for the development of future immunotherapies in which such DC are targeted.
Since 1980s, HIV/AIDS has escalated into a global pandemic. Although combinatorial antiretroviral therapy (cART) regimens can suppress plasma virus levels to below the detection limit and the survival rate of HIV-1 infected patients has been improving, long-term cART holds the potential to cause a number of chronic diseases. RNA interference (RNAi) is considered as a powerful method for developing new generation of therapeutics. Discovery of small interfering RNAs (siRNAs) shed light on limitations of targets that are "undruggable" with current technologies. However, delivery remains a major hurdle of siRNA-based therapy. Recent progress in technology of engineering nucleic acid enables a targeted delivery of siRNAs using aptamers, which, as often regarded as nucleic acid "antibodies," can recognize/bind to multiple different proteins and small-molecule targets by forming scaffolds for molecular interactions. SELEX technology enabled to isolate highly target specific aptamers from a random sequence oligonucleotide library. A number of aptamers for HIV-1 proteins as well as host proteins that interact with HIV-1 have been developed and some of them have potent viral neutralization ability and inhibition of HIV-1 infectivity. The availability of these aptamers has given an idea of using aptamers for targeting delivery of siRNAs. So far, aptamers against either HIV-1 gp120 or CD4 have been eagerly evaluated as the aptamer portion of the aptamer-siRNA chimeras for the treatment or prevention of HIV-1. In this chapter, we highlight the development and therapeutic potential of aptamer-siRNA chimeras for HIV-1.
Certain monoclonal antibodies (MAbs) directed against CD4 can efficiently block HIV-1 replication in vitro, To explore CD4-directed passive immunotherapy for prevention or treatment of AIDS virus infection, we previously examined the biological activity of a nondepleting CD4-specific murine MAb, mu5A8, This MAb, specific for domain 2 of CD4, blocks HIV-1 replication at a post-gp120-CD4 binding step, When administered to normal rhesus monkeys, all CD4(+) target cells were coated with antibody, yet no cell clearance or measurable immunosuppression occurred, However, strong anti-mouse Ig responses rapidly developed in all monkeys, In the present study, we report a successfully humanized form of mu5A8 (hu5A8) that retains binding to both human and monkey CD4 and anti-AIDS virus activity, When administered intravenously to normal rhesus monkeys, hu5A8 bound to all target CD4(+) cells without depletion and showed a significantly longer plasma half-life than mu5A8, Nevertheless, an anti-hu5AS response directed predominantly against V region determinants did eventually appear within 2 to 4 weeks in most animals, However, when hu5A8 was administered to rhesus monkeys chronically infected with the simian immunodeficiency virus of macaques, anti-hu5AS antibodies were not detected, Repeated administration of hu5A8 in these animals resulted in sustained plasma levels and CD4(+) cell coating with humanized antibody for 6 weeks, These studies demonstrate the feasibility of chronic administration of CD4-specific MAb as a potential means of treating or preventing HIV-1 infection.
The β-chemokine receptor CCR5 is considered to be an attractive target for inhibition of macrophage-tropic (CCR5-using or
R5) HIV-1 replication because individuals having a nonfunctional receptor (a homozygous 32-bp deletion in the CCR5 coding
region) are apparently normal but resistant to infection with R5 HIV-1. In this study, we found that TAK-779, a nonpeptide
compound with a small molecular weight (Mr 531.13), antagonized the binding of RANTES (regulated on activation, normal T cell expressed and secreted) to CCR5-expressing
Chinese hamster ovary cells and blocked CCR5-mediated Ca2+ signaling at nanomolar concentrations. The inhibition of β-chemokine receptors by TAK-779 appeared to be specific to CCR5
because the compound antagonized CCR2b to a lesser extent but did not affect CCR1, CCR3, or CCR4. Consequently, TAK-779 displayed
highly potent and selective inhibition of R5 HIV-1 replication without showing any cytotoxicity to the host cells. The compound
inhibited the replication of R5 HIV-1 clinical isolates as well as a laboratory strain at a concentration of 1.6–3.7 nM in
peripheral blood mononuclear cells, though it was totally inactive against T-cell line-tropic (CXCR4-using or X4) HIV-1.
The chemokine receptor 5 (CKR5) protein serves as a secondary receptor on CD4+ T lymphocytes for certain strains of human immunodeficiency virus-type 1 (HIV-1). The CKR5 structural gene was mapped to human chromosome 3p21, and a 32-base pair deletion allele (CKR5Δ32) was identified that is present at a frequency of ∼0.10 in the Caucasian population of the United States. An examination
of 1955 patients included among six well-characterized acquired immunodeficiency syndrome (AIDS) cohort studies revealed that
17 deletion homozygotes occurred exclusively among 612 exposed HIV-1 antibody-negative individuals (2.8 percent) and not at
all in 1343 HIV-1-infected individuals. The frequency of CKR5 deletion heterozygotes was significantly elevated in groups of individuals that had survived HIV-1 infection for more than
10 years, and, in some risk groups, twice as frequent as their occurrence in rapid progressors to AIDS. Survival analysis
clearly shows that disease progression is slower in CKR5 deletion heterozygotes than in individuals homozygous for the normal CKR5 gene. The CKR5Δ32 deletion may act as a recessive restriction gene against HIV-1 infection and may exert a dominant phenotype of delaying progression
to AIDS among infected individuals.
Dendritic cells (DC) capture microorganisms that enter peripheral mucosal tissues and then migrate to secondary lymphoid organs, where they present these in antigenic form to resting T cells and thus initiate adaptive immune responses. Here, we describe the properties of a DC-specific C-type lectin, DC-SIGN, that is highly expressed on DC present in mucosal tissues and binds to the HIV-1 envelope glycoprotein gp120. DC-SIGN does not function as a receptor for viral entry into DC but instead promotes efficient infection in trans of cells that express CD4 and chemokine receptors. We propose that DC-SIGN efficiently captures HIV-1 in the periphery and facilitates its transport to secondary lymphoid organs rich in T cells, to enhance infection in trans of these target cells.
It is well established that the gp120 V3 loop of T-cell-line-adapted human immunodeficiency virus type 1 (HIV-1) binds both cell-associated and soluble polyanions. Virus infectivity is increased by interactions between HIV-1 and heparan sulfate proteoglycans on some cell types, and soluble polyanions such as heparin and dextran sulfate neutralize HIV-1 in vitro. However, the analysis of gp120-polyanion interactions has been limited to T-cell-line-adapted, CXCR4-using virus and virus-derived gp120, and the polyanion binding ability of gp120 regions other than the V3 loop has not been addressed. Here we demonstrate by monoclonal-antibody inhibition, labeled heparin binding, and surface plasmon resonance studies that a second site, most probably corresponding to the newly defined, highly conserved coreceptor binding region on gp120, forms part of the polyanion binding surface. Consistent with the binding of polyanions to the coreceptor binding surface, dextran sulfate interfered with the gp120-CXCR4 association while having no detectable effect on the gp120-CD4 interaction. The interaction between polyanions and X4 or R5X4 gp120 was readily detectable, whereas weak or undetectable binding was observed with R5 gp120. Analysis of mutated forms of X4 gp120 demonstrated that the V3 loop is the major determinant for polyanion binding whereas other regions, including the V1/V2 loop structure and the NH2 and COOH termini, exert a more subtle influence. A molecular model of the electrostatic potential of the conserved coreceptor binding region confirmed that it is basic but that the overall charge on this surface is dominated by the V3 loop. These results demonstrate a selective interaction of gp120 with polyanions and suggest that the conserved coreceptor binding surface may present a novel and conserved target for therapeutic intervention.
Individuals who are homozygous for the 32-bp deletion in the gene coding for the chemokine receptor and major human immunodeficiency virus type 1 (HIV-1) coreceptor CCR5 (CCR5 −/−) lack functional cell surface CCR5 molecules and are relatively resistant to HIV-1 infection. HIV-1 infection in CCR5 −/− individuals, although rare, has been increasingly documented. We now report that the viral quasispecies from one such individual throughout disease is homogenous, T cell line tropic, and phenotypically syncytium inducing (SI); exclusively uses CXCR4; and replicates well in CCR5 −/− primary T cells. The recently discovered coreceptors BOB and Bonzo are not used. Although early and persistent SI variants have been described in longitudinal studies, this is the first demonstration of exclusive and persistent CXCR4 usage. With the caveat that the earliest viruses available from this subject were from approximately 4 years following primary infection, these data suggest that HIV-1 infection can be mediated and persistently maintained by viruses which exclusively utilize CXCR4. The lack of evolution toward the available minor coreceptors in this subject underscores the dominant biological roles of the major coreceptors CCR5 and CXCR4. This and two similar subjects (R. Biti, R. Ffrench, J. Young, B. Bennetts, G. Stewart, and T. Liang, Nat. Med. 3:252–253, 1997; I. Theodoreu, L. Meyer, M. Magierowska, C. Katlama, and C. Rouzioux, Lancet 349:1219–1220, 1997) showed relatively rapid CD4+ T-cell declines despite average or low initial viral RNA load. Since viruses which use CXCR4 exclusively cannot infect macrophages, these data have implications for the relative infection of the T-cell compartment versus the macrophage compartment in vivo and for the development of CCR5-based therapeutics.
During progression of the Acquired Immune Deficiency Syndrome (AIDS), the human immunodeficiency virus type 1 (HIV-1) is harbored in CD4+ T cells, which act as the primary reservoir for the virus. In vitro, HIV-1 requires activated T cells for a productive infection; however, in vivo, the number of circulating T cells in the activated state that are potential targets for HIV-1 infection is low. We have investigated the ability of HIV-1 to infect resting T cells, and the consequences of such an infection. T cell activation was not required for HIV-1 infection; however, viral DNA was unable to integrate in resting T cells and was maintained extrachromosomally. Subsequent T cell activation allowed integration of extrachromosomal forms and led to a productive viral life cycle. Extrachromosomal forms of viral DNA were found to persist for several weeks after infection of resting T cells and, following T cell activation, these forms maintained their ability to integrate and act as a template for infectious virus. Several lines of evidence, including temporal analysis of HIV-1 replication and analysis of an HIV-1 integrase deletion mutant, indicated that extra-chromosomal HIV-1 DNA genomes were transcriptionally active. These results are compatible with a model whereby HIV-1 can persist in a non-productive extra-chromosomal state in resting T cells until subsequent antigen-induced or mitogen-induced T cell activation, virus integration and release. Thus agents that induce T cell activation may control the rate of HIV-1 replication and spread during AIDS progression.
We previously reported the in vitro generation of a neutralization-resistant variant of the molecularly cloned isolate of human immunodeficiency virus type 1 (HIV-1), HXB2D. The molecular basis for the resistance was shown to be a point mutation in the env gene, causing the substitution of threonine for alanine at position 582 of gp41. Here, we show the variant to be resistant to syncytium inhibition as well as to neutralization by the immune-selecting serum. Moreover, 30% of HIV-positive human sera able to neutralize the parental virus have significantly decreased ability to neutralize the variant. As the A-to-T substitution thus has general relevance to the interaction of HIV-1 with the host immune system, we investigated further the biologic and immunologic bases for the altered properties. Synthetic peptides corresponding to the 582 region failed to compete in infectivity, neutralization, or syncytium inhibition assays and did not elicit neutralizing antibodies. Furthermore, human antibodies, affinity purified on synthetic peptide resins, bound to gp41 and peptides from the 582 region but did not possess neutralizing antibody activity. Some viral constructs in which the AVERY sequence in the 582 region was altered by site-directed mutagenesis were not infectious, indicating that the primary structure in this region is crucial for viral infectivity. Constructs predicted to possess a local secondary structure similar to that of the variant nevertheless behaved like the parental virus and remained neutralization sensitive. These results suggest that the requirements for neutralization resistance in this region are very precise. Our results with synthetic peptides show that the 582 region does not by itself constitute a neutralization epitope. Moreover, the degree of flexibility in amino acid substitution which allows maintenance of neutralization sensitivity suggests that position 582 does not form part of a noncontiguous neutralization epitope. The basis for neutralization resistance of the immune-selected variant is more likely a conformational change altering a neutralization epitope at a distant site.
Strategies for the treatment of human immunodeficiency virus-type 1 (HIV-1) infection must contend with the obstacle of drug
resistance. HIV-1 nucleocapsid protein zinc fingers are prime antiviral targets because they are mutationally intolerant and
are required both for acute infection and virion assembly. Nontoxic disulfide-substituted benzamides were identified that
attack the zinc fingers, inactivate cell-free virions, inhibit acute and chronic infections, and exhibit broad antiretroviral
activity. The compounds were highly synergistic with other antiviral agents, and resistant mutants have not been detected.
Zinc finger-reactive compounds may offer an anti-HIV strategy that restricts drug-resistance development.
We have examined components of the preintegration complex of human immunodeficiency virus type 1 (HIV-1) and have analyzed features which govern the association of these components. HIV-1 nucleoprotein complexes, isolated from nuclear and cytoplasmic extracts of CD4+ cells after acute virus infection, contained viral RNA and DNA in association with viral matrix (MA), integrase (IN), and reverse transcriptase (RT) antigens but not capsid (CA) antigens and possessed integration activity in vitro. Association of IN but not RT or MA antigens with viral DNA was detergent-stable. Analysis of viral DNA synthesis and nuclear import of viral nucleoprotein complexes in the presence of a reversible RT inhibitor demonstrated that reverse transcription of viral RNA could be completed entirely in the host cell nucleus. Our studies demonstrate structural and functional features of the nucleoprotein (preintegration) complex of HIV-1 which are pertinent to the understanding of early events in the lentiviral life cycle.
Cyclophilins are a family of proteins that bind the immunosuppressant cyclosporin A, possess peptidyl-prolyl cis-trans isomerase activity, and assist in the folding of proteins. Human cyclophilins A and B are host cell proteins that bind specifically to the HIV-1 Gag polyprotein p55gag in vitro. Here we report that viral particles formed by p55gag, in contrast to particles formed by the Gag polyproteins of other retroviruses, contain significant amounts of cyclophilin A. Sequences in the capsid domain of p55gag are both required and sufficient for the virion-association of cyclophilin A. The association of cyclophilin A with HIV-1 virions was inhibited in a dose-dependent manner by cyclosporin A as well as by SDZ NIM811 ([Melle-4]cyclosporin), a non-immunosuppressive analogue of cyclosporin A. Drug-induced reductions in virion-associated cyclophilin A levels were accompanied by reductions in virion infectivity, indicating that the association is functionally relevant. Moreover, SDZ NIM811 inhibited the replication of HIV-1 but was inactive against SIVMAC, a primate immunodeficiency virus closely related to HIV-1, which does not incorporate cyclophilin A.
Integrase is the only viral protein necessary for integration of retroviral DNA into chromosomal DNA of the host cell. Biochemical analysis of human immunodeficiency virus type 1 (HIV-1) integrase with purified protein and synthetic DNA substrates has revealed extensive information regarding the mechanism of action of the enzyme, as well as identification of critical residues and functional domains. Since in vitro reactions are carried out in the absence of other viral proteins and they analyze strand transfer of only one end of the donor substrate, they do not define completely the process of integration as it occurs during the course of viral infection. In an effort to further understand the role of integrase during viral infection, we initially constructed a panel of 24 HIV-1 mutants with specific alanine substitutions throughout the integrase coding region and analyzed them in a human T-cell line infection. Of these mutant viruses, 12 were capable of sustained viral replication, 11 were replication defective, and 1 was temperature sensitive for viral growth. The replication defective viruses express and correctly process the integrase and Gag proteins. Using this panel of mutants and an additional set of 18 mutant viruses, we identified nine amino acids which, when replaced with alanine, destroy integrase activity. Although none of the replication-defective mutants are able to integrate into the host genome, a subset of them with alterations in the catalytic triad are capable of Tat-mediated transactivation of an indicator gene linked to the viral long terminal repeat promoter. We present evidence that integration of the HIV-1 provirus is essential not only for productive infection of T cells but also for virus passage in both cultured peripheral blood lymphocytes and macrophage cells.
Bicyclams are a novel class of antiviral compounds which act as potent and selective inhibitors of the replication of human immunodeficiency virus type 1 (HIV-1) and HIV-2. They block an early step in the viral life cycle following adsorption to the CD4 receptor and preceding reverse transcription. To identify the molecular target of these compounds, we genetically analyzed variants of the HIV-1 molecular clone NL4-3, which developed resistance against two structurally related bicyclams, JM2763 and the more potent SID791. The resistant strains were obtained after long-term passaging in MT-4 cells in the presence of progressively increasing compound concentrations. Recombinants between selected genes of the resistant strains and the parental NL4-3 provirus were generated by adapting the marker rescue technique to MT-4 cells. The bicyclam-resistant phenotype was rescued by transferring the envelope gp120 gene of bicyclam-resistant virus into the NL4-3 parental genetic background. In the gp120 genes of the resistant strains, we identified several mutations leading to amino acid substitutions in the V3 loop. Furthermore, two substitutions of highly conserved amino acids in close proximity to the disulfide bridges of the V3 and V4 loops were found in both SID791- and JM2763-resistant strains. Additional mutations in regions encoding V3, C4, V5, and C5 were present in SID791-resistant viruses. Recombination experiments with overlapping parts of the envelope gene indicated that most, if not all, of the mutations were necessary to develop the fully SID791 resistant phenotype. The mutations in the C-terminal part of gp120 downstream of the V3 loop sequence conferred partial resistance to JM2763 but did not significantly decrease susceptibility to SID791. The genetic data and the biological properties of the resistant viruses point to inhibition of entry and fusion as the mode of action of the HIV-inhibitory bicyclams. A possible mechanism of binding of bicyclams to gp120 leading to inhibition of unfolding of gp120 and its shedding from the gp41 fusion domain is discussed.
Several disulfide benzamides have been shown to possess wide-spectrum antiretroviral activity in cell culture at low micromolar to submicromolar concentrations, inhibiting human immunodeficiency virus (HIV) type 1 (HIV-1) clinical and drug-resistant strains along with HIV-2 and simian immunodeficiency virus [Rice, W. G., Supko, J. G., Malspeis, L., Buckheit, R. W., Jr., Clanton, D., Bu, M., Graham, L., Schaeffer, C. A., Turpin, J. A., Domagala, J., Gogliotti, R., Bader, J. P., Halliday, S. M., Coren, L., Sowder, R. C., II, Arthur, L. O. & Henderson, L. E. (1995) Science 270, 1194-1197]. Rice and coworkers have proposed that the compounds act by "attacking" the two zinc fingers of HIV nucleocapsid protein. Shown here is evidence that low micromolar concentrations of the anti-HIV disulfide benzamides eject zinc from HIV nucleocapsid protein (NCp7) in vitro, as monitored by the zinc-specific fluorescent probe N-(6-methoxy-8-quinoyl)-p-toluenesulfonamide (TSQ). Structurally similar disulfide benzamides that do not inhibit HIV-1 in culture do not eject zinc, nor do analogs of the antiviral compounds with the disulfide replaced with a methylene sulfide. The kinetics of NCp7 zinc ejection by disulfide benzamides were found to be nonsaturable and biexponential, with the rate of ejection from the C-terminal zinc finger 7-fold faster than that from the N-terminal. The antiviral compounds were found to inhibit the zinc-dependent binding of NCp7 to HIV psi RNA, as studied by gel-shift assays, and the data correlated well with the zinc ejection data. Anti-HIV disulfide benzamides specifically eject NCp7 zinc and abolish the protein's ability to bind psi RNA in vitro, providing evidence for a possible antiretroviral mechanism of action of these compounds. Congeners of this class are under advanced preclinical evaluation as a potential chemotherapy for acquired immunodeficiency syndrome.
The cellular peptidyl-prolyl isomerase cyclophilin A is incorporated into human immunodeficiency virus type 1 virions via contacts with the proline-rich domain of the Gag polyprotein. Cyclosporine A and nonimmunosuppressive analogs bind with high affinity to cyclophilin A, compete with Gag for binding to cyclophilin A, and prevent incorporation of cyclophilin A into virions; in parallel with the disruption of cyclophilin A incorporation into virions, there is a linear reduction in the initiation of reverse transcription after infection of a T cell. Passage of human immunodeficiency virus type 1 in the presence of the drug selects one of two mutations, either of which alters the proline-rich domain of Gag and is sufficient to confer drug resistance on the cloned wild-type provirus. Neither mutation alters Gag's cyclophilin A-binding properties in vitro, and cyclophilin A incorporation into drug-resistant virions is effectively disrupted by cyclosporine A, indicating that the drug-resistant mutants do not require virion-associated cyclophilin A to initiate infection. That Gag's functional dependence on cyclophilin A can be differentiated genetically from its ability to bind cyclophilin A is further demonstrated by the rescue of a mutation precluding cyclophilin A packaging by a mutation conferring cyclosporine A resistance. These experiments demonstrate that, in addition to its ability to package cyclophilin A into virions, gag encodes the functional target of cyclophilin A.
SID 791, a bicyclam inhibiting human immunodeficiency virus (HIV) replication in vitro by blocking virus entry into cells, is an effective inhibitor of virus production and of depletion of human CD4+ T cells in HIV type 1-infected SCID-hu Thy/Liv mice. Steady levels of 100 ng of SID 791 or higher per ml in plasma resulted in statistically significant inhibition of p24 antigen formation. Daily injections of SID 791 caused a dose-dependent decrease in viremia, and this inhibition could be potentiated by coadministration of zidovudine or didanose. The present study suggests that SID 791 alone or in combination with licensed antiviral agents may decrease the virus load in HIV-infected patients and, by extension, that the infectious cell entry step is a valid target for antiviral chemotherapy of HIV disease. The SCID-hu Thy/Liv model in effect provides a rapid means of assessing the potential of compounds with novel modes of antiviral action, as well as the potential of antiviral drug combinations.
Several members of the chemokine receptor family have been shown to function in association with CD4 to permit HIV-1 entry and infection. However, the mechanism by which these molecules serve as CD4-associated cofactors is unclear. In the present report, we show that one member of this family, termed Fusin/ CXCR4, is able to function as an alternative receptor for some isolates of HIV-2 in the absence of CD4. This conclusion is supported by the finding that (1) CD4-independent infection by these viruses is inhibited by an anti-Fusin monoclonal antibody, (2) Fusin expression renders human and nonhuman CD4-negative cell lines sensitive to HIV-2-induced syncytium induction and/or infection, and (3) Fusin is selectively down-regulated from the cell surface following HIV-2 infection. The finding that one chemokine receptor can function as a primary viral receptor strongly suggests that the HIV envelope glycoprotein contains a binding site for these proteins and that differences in the affinity and/or the availability of this site can extend the host range of these viruses to include a number of CD4-negative cell types.
Chemokine receptors serve as coreceptors for HIV entry into CD4+ cells. Their expression is thought to determine the tropism of viral strains for different cell types, and also to influence susceptibility to infection and rates of disease progression. Of the chemokine receptors, CCR5 is the most important for viral transmission, since CCR5 is the principal receptor for primary, macrophage-tropic viruses, and individuals homozygous for a defective CCR5 allele (delta32/delta32) are highly resistant to infection with HIV-1. In this study, CCR5-specific mAbs were generated using transfectants expressing high levels of CCR5. The specificity of these mAbs was confirmed using a broad panel of chemokine receptor transfectants, and by their non-reactivity with T cells from delta32/delta32 individuals. CCR5 showed a distinct pattern of expression, being abundant on long-term activated, IL-2-stimulated T cells, on a subset of effector/memory T cells in blood, and on tissue macrophages. A comparison of normal and CCR5 delta32 heterozygotes revealed markedly reduced expression of CCR5 on T cells from the heterozygotes. There was considerable individual to individual variability in the expression of CCR5 on blood T cells, that related to factors other than CCR5 genotype. Low expression of CCR5 correlated with the reduced infectability of T cells with macrophage-tropic HIV-1, in vitro. Anti-CCR5 mAbs inhibited the infection of PBMC by macrophage-tropic HIV-1 in vitro, but did not inhibit infection by T cell-tropic virus. Anti-CCR5 mAbs were poor inhibitors of chemokine binding, indicating that HIV-1 and ligands bind to separate, but overlapping regions of CCR5. These results illustrate many of the important biological features of CCR5, and demonstrate the feasibility of blocking macrophage-tropic HIV-1 entry into cells with an anti-CCR5 reagent.
Ligation of CCR5 by the CC chemokines RANTES, MIP-1alpha or MIP-1beta, and of CXCR4 by the CXC chemokine SDF-1alpha, profoundly inhibits the replication of HIV strains that use these coreceptors for entry into CD4(+) T lymphocytes. The mechanism of entry inhibition is not known. We found a rapid and extensive downregulation of CXCR4 by SDF-1alpha and of CCR5 by RANTES or the antagonist RANTES(9-68). Confocal laser scanning microscopy showed that CCR5 and CXCR4, after binding to their ligands, are internalized into vesicles that qualify as early endosomes as indicated by colocalization with transferrin receptors. Internalization was not affected by treatment with Bordetella pertussis toxin, showing that it is independent of signaling via Gi-proteins. Removal of SDF-1alpha led to rapid, but incomplete surface reexpression of CXCR4, a process that was not inhibited by cycloheximide, suggesting that the coreceptor is recycling from the internalization pool. Deletion of the COOH-terminal, cytoplasmic domain of CXCR4 did not affect HIV entry, but prevented SDF-1alpha-induced receptor downregulation and decreased the potency of SDF-1alpha as inhibitor of HIV replication. Our results indicate that the ability of the coreceptor to internalize is not required for HIV entry, but contributes to the HIV suppressive effect of CXC and CC chemokines.
The chemokine receptor CXCR4 is the major coreceptor used for cellular entry by T cell- tropic human immunodeficiency virus (HIV)-1 strains, whereas CCR5 is used by macrophage (M)-tropic strains. Here we show that a small-molecule inhibitor, ALX40-4C, inhibits HIV-1 envelope (Env)-mediated membrane fusion and viral entry directly at the level of coreceptor use. ALX40-4C inhibited HIV-1 use of the coreceptor CXCR4 by T- and dual-tropic HIV-1 strains, whereas use of CCR5 by M- and dual-tropic strains was not inhibited. Dual-tropic viruses capable of using both CXCR4 and CCR5 were inhibited by ALX40-4C only when cells expressed CXCR4 alone. ALX40-4C blocked stromal-derived factor (SDF)-1alpha-mediated activation of CXCR4 and binding of the monoclonal antibody 12G5 to cells expressing CXCR4. Overlap of the ALX40-4C binding site with that of 12G5 and SDF implicates direct blocking of Env interactions, rather than downregulation of receptor, as the mechanism of inhibition. Thus, ALX40-4C represents a small-molecule inhibitor of HIV-1 infection that acts directly against a chemokine receptor at the level of Env-mediated membrane fusion.
Several members of the chemokine receptor family have been shown to function in association with CD4 to permit human immunodeficiency virus type 1 (HIV-1) entry and infection. The CXC chemokine receptor CXCR4/fusin is a receptor for pre-B cell growth stimulating factor (PBSF)/stromal cell-derived factor 1 (SDF-1) and serves as a coreceptor for the entry of T cell line-tropic HIV-1 strains. Thus, the development of CXCR4 antagonists or agonists may be useful in the treatment of HIV-1 infection. T22 ([Tyr5,12,Lys7]-polyphemusin II) is a synthesized peptide that consists of 18 amino acid residues and an analogue of polyphemusin II isolated from the hemocyte debris of American horseshoe crabs (Limulus polyphemus). T22 was found to specifically inhibit the ability of T cell line-tropic HIV-1 to induce cell fusion and infect the cell lines transfected with CXCR4 and CD4 or peripheral blood mononuclear cells. In addition, T22 inhibited Ca2+ mobilization induced by pre-B cell growth stimulating factor (PBSF)/SDF-1 stimulation through CXCR4. Thus, T22 is a small molecule CXCR4 inhibitor that blocks T cell line-tropic HIV-1 entry into target cells.
Bicyclams are a novel class of antiviral compounds that are highly potent and selective inhibitors of the replication of HIV-1 and HIV-2. Surprisingly, however, when the prototype compound AMD3100 was tested against M-tropic virus strains such as BaL, ADA, JR-CSF, and SF-162 in human peripheral blood mononuclear cells, the compound was completely inactive. Because of the specific and potent inhibitory effect of AMD3100 on T-tropic viruses, but not M-tropic viruses, it was verified that AMD3100 interacts with the CXC-chemokine receptor CXCR4, the main coreceptor used by T-tropic viruses. AMD3100 dose dependently inhibited the binding of a specific CXCR4 monoclonal antibody to SUP-T1 cells as measured by flow cytometry. It did not inhibit the binding of the biotinylated CC-chemokine macrophage inflammatory protein (MIP) 1alpha or MIP-1beta, ligands for the chemokine receptor CCR5 (the main coreceptor for M-tropic viruses). In addition, AMD3100 completely blocked (a) the Ca2+ flux at 100 ng/ml in lymphocytic SUP-T1 and monocytic THP-1 cells, and (b) the chemotactic responses of THP-1 cells induced by stromal cell-derived factor 1alpha, the natural ligand for CXCR4. Finally, AMD3100 had no effect on the Ca2+ flux induced by the CC-chemokines MIP-1alpha, regulated on activation normal T cell expressed and secreted (RANTES; also a ligand for CCR5), or monocyte chemoattractant protein 3 (a ligand for CCR1 and CCR2b), nor was it able to induce Ca2+ fluxes by itself. The bicyclams are, to our knowledge, the first low molecular weight anti-HIV agents shown to act as potent and selective CXCR4 antagonists.
We have continuously measured CD4-induced conformational changes of cell surface-expressed human immunodeficiency virus type-1 envelope glycoprotein gp120-gp41 in situ using 4,4'-dianilino-1, 1'-binaphthyl-5,5'-disulfonic acid, a fluorescent probe that binds to hydrophobic groups. CD4-expressing human T cell lines induced significant and rapid conformational changes (<1 min delay) in gp120-gp41 from T cell-tropic strains, and little conformational changes in gp120-gp41 from macrophage-tropic strains, with equivalent levels of envelope expression. Conversely, CD4-expressing human macrophages induced significant and rapid conformational changes in gp120-gp41 from macrophage-tropic strains, and little conformational changes in gp120-gp41 from T cell-tropic strains. Thus, the conformational changes undergone by gp120-gp41, which lead to membrane fusion, are highly cooperative and require both receptor and co-receptor. We used a dye transfer assay to show that neither membrane lipid fusion or fusion pore formation can occur with host cells having different tropism from the envelope.
We have studied the breadth and potency of the inhibitory actions of the CC chemokines macrophage inhibitory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES against macrophage-tropic (M-tropic) primary isolates of human immunodeficiency virus type 1 (HIV-1) and of the CXC chemokine stromal cell-derived factor 1alpha against T-cell-tropic (T-tropic) isolates, using mitogen-stimulated primary CD4+ T cells as targets. There was considerable interisolate variation in the sensitivity of HIV-1 to chemokine inhibition, which was especially pronounced for the CC chemokines and M-tropic strains. However, this variation was not obviously dependent on the genetic subtype (A through F) of the virus isolates. Peripheral blood mononuclear cell donor-dependent variation in chemokine inhibition potency was also observed. Among the CC chemokines, the rank order for potency (from most to least potent) was RANTES, MIP-1beta, MIP-1alpha. Some M-tropic isolates, unexpectedly, were much more sensitive to RANTES than to MIP-1beta, whereas other isolates showed sensitivities comparable to those of these two chemokines. Down-regulation of the CCR5 and CXCR4 receptors occurred in cells treated with the cognate chemokines and probably contributes to anti-HIV-1 activity. Thus, for CCR5, the rank order for down-regulation was also RANTES, MIP-1beta, MIP-1alpha.
A synthetic peptide, DP178, containing amino acids 127 to 162 of the human immunodeficiency virus type 1 (HIV-1) gp41 Env glycoprotein, is a potent inhibitor of virus infection and virus mediated cell-to-cell fusion (C. Wild, T. Greenwell, and T. Matthews, AIDS Res. Hum. Retroviruses 9:1051-1053, 1993). In an effort to understand the mechanism of action of this peptide, we derived resistant variants of HIV-1(IIIB) and NL4-3 by serial virus passage in the presence of increasing doses of the peptide. Sequence analysis of the resistant isolates suggested that a contiguous 3-amino-acid sequence within the amino-terminal heptad repeat motif of gp41 was associated with resistance. Site-directed mutagenesis studies confirmed this observation and indicated that changes in two of these three residues were necessary for development of the resistant phenotype. Direct binding of DP178 to recombinant protein and synthetic peptide analogs containing the wild-type and mutant heptad repeat sequences revealed a strong correlation between DP178 binding and the biological sensitivity of the corresponding virus isolates to DP178. The results are discussed from the standpoints of the mechanism of action of DP178 and recent crystallographic information for a core structure of the gp41 ectodomain.
We recently reported that a cationic peptide, T22 ([Tyr 5,12 , Lys ⁷ ]-polyphemusin II), specifically inhibits human immunodeficiency virus type 1 (HIV-1) infection mediated by CXCR4 (T. Murakami et al., J. Exp. Med. 186:1389–1393, 1997). Here we demonstrate that T22 effectively inhibits replication of T-tropic HIV-1, including primary isolates, but not of non-T-tropic strains. By using a panel of chimeric viruses between T- and M-tropic HIV-1 strains, viral determinants for T22 susceptibility were mapped to the V3 loop region of gp120. T22 bound to CXCR4 and interfered with stromal-cell-derived factor-1α–CXCR4 interactions in a competitive manner. Blocking of anti-CXCR4 monoclonal antibodies by T22 suggested that the peptide interacts with the N terminus and two of the extracellular loops of CXCR4. Furthermore, the inhibition of cell-cell fusion in cells expressing CXCR4/CXCR2 chimeric receptors suggested that determinants for sensitivity of CXCR4 to T22 include the three extracellular loops of the coreceptor.
The HIV-1 gp41 protein promotes viral entry by mediating the fusion of viral and cellular membranes. A prominent pocket on the surface of a central trimeric coiled coil within gp41 was previously identified as a potential target for drugs that inhibit HIV-1 entry. We designed a peptide, IQN17, which properly presents this pocket. Utilizing IQN17 and mirror-image phage display, we identified cyclic, D-peptide inhibitors of HIV-1 infection that share a sequence motif. A 1.5 Å cocrystal structure of IQN17 in complex with a D-peptide, and NMR studies, show that conserved residues of these inhibitors make intimate contact with the gp41 pocket. Our studies validate the pocket per se as a target for drug development. IQN17 and these D-peptide inhibitors are likely to be useful for development and identification of a new class of orally bioavailable anti-HIV drugs.
The phenotype of HIV-1 isolates is defined by the cells in which they replicate in vitro, but these phenotypes can change in vivo with profound implications for viral transmission, pathogenesis and disease progression. Here we propose a new classification system based on co-receptor use, providing a more accurate description of viral phenotype than the present imprecise and often misleading classification schemes.
Nucleocapsid p7 protein (NCp7) zinc finger domains of the human immunodeficiency virus type 1 (HIV-1) are being developed as antiviral targets due to their key roles in viral replication and their mutationally nonpermissive nature. On the basis of our experience with symmetrical disulfide benzamides (DIBAs; Rice et al. Science 1995, 270, 1194−1197), we synthesized and evaluated variants of these dimers, including sets of 4,4‘- and 3,3‘-disubstituted diphenyl sulfones and their monomeric benzisothiazolone derivatives (BITA). BITAs generally exhibited diminished antiviral potency when compared to their disulfide precursors. Novel, monomeric structures were created by linking haloalkanoyl groups to the benzamide ring through −NH−C(O)− (amide) or −S−C(O)− (thiolester) bridges. Amide-linked compounds generally lacked antiviral activity, while haloalkanoyl thiolesters and non-halogen-bearing analogues frequently exhibited acceptable antiviral potency, thus establishing thiolester benzamides per se as a new anti-HIV chemotype. Pyridinioalkanoyl thiolesters (PATEs) exhibited superior anti-HIV-1 activity with minimal cellular toxicity and appreciable water solubility. PATEs were shown to preferentially target the NCp7 Zn finger when tested against other molecular targets, thus identifying thiolester benzamides, and PATEs in particular, as novel NCp7 Zn finger inhibitors for in vivo studies.
Binding of the T-cell antigen CD4 to human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 has been reported to induce conformational rearrangements in the envelope complex that facilitate recognition of the CCR5 coreceptor and consequent viral entry into cells. To better understand the mechanism of virus docking and cell fusion, we developed a three-component gp120−CD4−17b optical biosensor assay to visualize the CD4-induced conformational change of gp120 as seen through envelope binding to a neutralizing human antibody, 17b, which binds to epitopes overlapping the CCR5 binding site. The 17b Fab fragment was immobilized on a dextran sensor surface, and kinetics of gp120 binding were evaluated by both global and linear transformation analyses. Adding soluble CD4 (sCD4) increased the association rate of full-length JR−FL gp120 by 25-fold. This change is consistent with greater exposure of the 17b binding epitope on gp120 when CD4 is bound and correlates with CD4-induced conformational changes in gp120 leading to higher affinity binding to coreceptor. A smaller enhancement of 17b binding by sCD4 was observed with a mutant of gp120, ΔJR−FL protein, which lacks V1 and V2 variable loops and N- and C-termini. Biosensor results for JR−FL and ΔJR−FL argue that CD4-induced conformational changes in the equilibrium state of gp120 lead both to movement of V1/V2 loops and to conformational rearrangement in the gp120 core structure and that both of these lead to greater exposure of the coreceptor-binding epitope in gp120. A 17b binding enhancement effect on JR−FL also was observed with a 32-amino acid charybdotoxin miniprotein construct that contains an epitope predicted to mimic the Phe 43/Arg 59 region of CD4 and that competes with CD4 for gp120 binding. Results with this construct argue that CD4-mimicking molecules with surrogate structural elements for the Phe 43/Arg 59 components of CD4 are sufficient to elicit a similar gp120 conformational isomerization as expressed by CD4 itself.
The chemokine receptor CXCR4 (a receptor for the Cys-X-Cys class of chemokines) is a CD4-associated coreceptor for T-cell-tropic strains of human immunodeficiency virus 1 (HIV-1) and represents a target for antiviral therapy. Infection by T-tropic HIV-1 can be blocked by stromal-cell-derived factor-1 (SDF-1), the natural ligand of CXCR4. The broad variety of cells expressing CXCR4 and the perturbations observed in mice deficient for SDF-1 suggest that antiviral compounds antagonizing the signalling activity of CXCR4 might have severe side effects in vivo. Compounds that interfere selectively with HIV entry and not with SDF-1 signalling would therefore be useful.
A series of peptides, each of 13 residues, spanning the whole SDF-1alpha sequence were tested for their ability to block HIV-1 infection. The antiviral and signalling properties of SDF-1 were retained by a peptide corresponding to its amino terminus. Removal of the first two residues resulted in an antiviral antagonist of the SDF-1-CXCR4 signalling pathway. We prepared 234 single-substitution analogues and identified one antiviral analogue that had drastically reduced agonistic or antagonistic properties. The antiviral peptides competed with the monoclonal antibody 12G5 for CXCR4 binding. Their antiviral activity seems to be due to receptor occupancy rather than induction of receptor endocytosis.
The amino terminus of the SDF-1 chemokine is sufficient for signal transduction via CXCR4 and for inhibition of HIV-1 entry, but these activities could be dissociated in a peptide analogue. This peptide represents a lead molecule for the design of low molecular weight antiviral drugs.
Evidence suggests that CD8+ T lymphocytes are involved in the control of human immunodeficiency virus (HIV) infection in vivo, either by cytolytic mechanisms or by the release of HIV-suppressive factors (HIV-SF). The chemokines RANTES, MIP-1 alpha, and MIP-1 beta were identified as the major HIV-SF produced by CD8+ T cells. Two active proteins purified from the culture supernatant of an immortalized CD8+ T cell clone revealed sequence identity with human RANTES and MIP-1 alpha. RANTES, MIP-1 alpha, and MIP-1 beta were released by both immortalized and primary CD8+ T cells. HIV-SF activity produced by these cells was completely blocked by a combination of neutralizing antibodies against RANTES, MIP-1 alpha, and MIP-1 beta. Recombinant human RANTES, MIP-1 alpha, and MIP-1 beta induced a dose-dependent inhibition of different strains of HIV-1, HIV-2, and simian immunodeficiency virus (SIV). These data may have relevance for the prevention and therapy of AIDS.
A peptide designated DP-107 was synthesized containing amino acid residues 558-595 of the envelope glycoprotein gp160 of human immunodeficiency virus type 1 strain LAI (HIV-1LAI). Algorithms for secondary structure have predicted that this region of the envelope transmembrane protein should form an extended alpha-helix. Consistent with this prediction, analysis by circular dichroism (CD) indicated that, under physiological conditions, DP-107 is approximately 85% helical. The high degree of stable secondary structure in a synthetic peptide of this size suggests self-association typical of a coiled coil or leucine zipper. In biological assays, the peptide efficiently blocked virus-mediated cell-cell fusion processes as well as infection of peripheral blood mononuclear cells by both prototypic and primary isolates of HIV-1. A single amino acid substitution in the peptide greatly destabilized its solution structure as measured by CD and abrogated its antiviral activity. An analogue containing a terminal cysteine was oxidized to form a dimer, and this modification lowered the dose required for antiviral effect from 5 to about 1 microgram/ml. These results suggest that both oligomerization and ordered structure are necessary for biological activity. They provide insights also into the role of this region in HIV infection and the potential for development of a new class of antiviral agents.
Cyclosporin A and FK506 inhibit T- and B-cell activation and other processes essential to an effective immune response. In T lymphocytes these drugs disrupt an unknown step in the transmission of signals from the T-cell antigen receptor to cytokine genes that coordinate the immune response. The putative intracellular receptors for FK506 and cyclosporin are cis-trans prolyl isomerases. Binding of the drug inhibits isomerase activity, but studies with other prolyl isomerase inhibitors and analysis of cyclosporin-resistant mutants in yeast suggest that the effects of the drug result from the formation of an inhibitory complex between the drug and isomerase, and not from inhibition of isomerase activity. A transcription factor, NF-AT, which is essential for early T-cell gene activation, seems to be a specific target of cyclosporin A and FK506 action because transcription directed by this protein is blocked in T cells treated with these drugs, with little or no effect on other transcription factors such as AP-1 and NF-kappa B. Here we demonstrate that NF-AT is formed when a signal from the antigen receptor induces a pre-existing cytoplasmic subunit to translocate to the nucleus and combine with a newly synthesized nuclear subunit of NF-AT. FK506 and cyclosporin A block translocation of the cytoplasmic component without affecting synthesis of the nuclear subunit.
Productive infection of human T lymphocytes by HIV-1 is dependent upon proliferation of the infected cell. Nonproliferating quiescent T cells can be infected by HIV-1 and harbor the virus in an inactive state until subsequent mitogenic stimulation. We use a modification of the polymerase chain reaction method, which is both sensitive and quantitative, to demonstrate that HIV-1 DNA synthesis is initiated in infected quiescent T cells at levels comparable with those of activated T cells. However, unlike that of activated T cells, the viral genome is not completely reverse transcribed in quiescent cells. Although this viral DNA structure can persist in quiescent cells as a latent form, it is labile. We discuss the lability of this HIV-1 DNA structure in relation to a "self-restricting persistent infection" by HIV-1 and propose that this may explain the low percentage of infected cells in the circulation of AIDS patients.
Retroviruses are a family of widespread small animal viruses about 110 nm in diameter, composed of an inner core surrounded by an outer envelope formed of a lipid bilayer of cellular origin in which are anchored viral glycoproteins. The inner core is formed by an outer shell of capsid protein molecules (CA protein) surrounding the dimeric RNA genome in close association with about 2000 molecules of nucleocapsid protein (NC protein) and molecules of reverse transcriptase (RT) and integrase (IN). Conversion of the genomic single-stranded RNA into a double-stranded proviral DNA by RT takes place in the nucleocapsid substructure and involves two DNA strand transfers to generate the long terminal repeats (LTR) required for IN-mediated integration of the proviral DNA into the cellular genome and its expression.
During HIV-1 reverse transcription, the plus-strand of viral DNA is synthesized as two discrete segments. We show here that synthesis of the upstream segment terminates at the center of the genome after an 88 or 98 nucleotide strand displacement of the downstream segment, initiated at the central polypurine tract. Thus, the final structure of unintegrated linear HIV-1 DNA includes a central plus-strand overlap. In vitro reconstitution using only purified reverse transcriptase with appropriate DNA hybrids gave rise to efficient and accurate termination, which was dramatically amplified in the context of strand displacement. Mutation of the sequence immediately upstream of the termination sites almost completely abolished termination both in infected cells and in vitro. This mutation profoundly impaired replication of HIV-1. We conclude that proper central plus-strand termination, mediated by a novel cis-active termination sequence, is a key step in HIV-1 replication.
Little is known about host factors necessary for retroviral virion assembly or uncoating. We have previously shown that the principal structural protein of the human immunodeficiency virus HIV-1, the Gag polyprotein, binds the cyclophilin peptidyl-prolyl isomerases; cyclophilins catalyse a rate-limiting step in protein folding and protect cells from heat shock. Here we demonstrate that cyclophilin A is specifically incorporated into HIV-1 virions but not into virions of other primate immunodeficiency viruses. A proline-rich region conserved in all HIV-1 Gag polyproteins is required for cyclophilin A binding and incorporation. Disruption of a single proline blocks the Gag-cyclophilin interaction in vitro, prevents cyclophilin A incorporation into virions, and inhibits HIV-1 replication. Our results indicate that the interaction of Gag with cyclophilin A is necessary for the formation of infectious HIV-1 virions.
A putative chemokine receptor that we previously cloned and termed LESTR has recently been shown to function as a co-receptor (termed fusin) for lymphocyte-tropic HIV-1 strains. Cells expressing CD4 became permissive to infection with T-cell-line-adapted HIV-1 strains of the syncytium-inducing phenotype after transfection with LESTR/fusin complementary DNA. We report here the indentification of a human chemokine of the CXC type, stromal cell-derived factor 1 (SDF-1), as the natural ligand for LESTR/fusin, and we propose the term CXCR-4 for this receptor, in keeping with the new chemokine-receptor nomenclature. SDF-1 activates Chinese hamster ovary (CHO) cells transfected with CXCR-4 cDNA as well as blood leukocytes and lymphocytes. In cell lines expressing CXCR-4 and CD4, and in blood lymphocytes, SDF-1 is a powerful inhibitor of infection by lymphocyte-tropic HIV-1 strains, whereas the CC chemokines RANTES, MIP-1 alpha and MIP-1 beta, which were shown previously to prevent infection with primary, monocyte-tropic viruses, are inactive. In combination with CC chemokines, which block the infection with monocyte/macrophage-tropic viruses, SDF-1 could help to decrease virus load and prevent the emergence of the syncytium-inducing viruses which are characteristic of the late stages of AIDS.
Chemokines are chemotactic cytokines that activate and direct the migration of leukocytes. There are two subfamilies, the CXC and the CC chemokines. We recently found that the CXC-chemokine stromal cell-derived factor-1 (SDF-1) is a highly efficacious lymphocyte chemoattractant. Chemokines act on responsive leukocyte subsets through G-protein-coupled seven-transmembrane receptors, which are also used by distinct strains of HIV-1 as cofactors for viral entry. Laboratory-adapted and some T-cell-line-tropic (T-tropic) primary viruses use the orphan chemokine receptor LESTR/fusin (also known as fusin), whereas macrophage-tropic primary HIV-1 isolates use CCR-5 and CCR-3 (refs 7-11), which are receptors for known CC chemokines. Testing of potential receptors demonstrated that SDF-1 signalled through, and hence 'adopted', the orphan receptor LESTR, which we therefore designate CXC-chemokine receptor-4 (CXCR-4). SDF-1 induced an increase in intracellular free Ca2+ and chemotaxis in CXCR-4-transfected cells. Because SDF-1 is a biological ligand for the HIV-1 entry cofactor LESTR, we tested whether it inhibited HIV-1. SDF-1 inhibited infection by T-tropic HIV-1 of HeLa-CD4 cells, CXCR-4 transfectants, and peripheral blood mononuclear cells (PBMCs), but did not affect CCR-5-mediated infection by macrophage-tropic (M-tropic) and dual-tropic primary HIV-1.
Synthetic multibranched peptides derived from the V3 domain of human immunodeficiency virus type 1 (HIV-1) gp120 inhibit HIV-1 entry into CD4+ and CD4- cells by two distinct mechanisms: competitive inhibition of HIV-1 binding to CD4-/GalCer+ colon cells and postbinding inhibition of HIV-1 fusion with CD4+ lymphocytes. In the present study, we have characterized the cellular binding sites for the V3 peptide SPC3, which possesses eight V3 consensus motifs GPGRAF radially branched on a neutral polyLys core matrix. These binding sites are glycosphingolipids that share a common structural determinant, i.e., a terminal galactose residue with a free hydroxyl group in position 4: GalCer/sulfatide on CD4-/GalCer+ colon cells; LacCer and its sialosyl derivatives GM3 and GD3 on CD4+ human lymphocytes. These data suggest that the V3 peptide binds to the GalCer/sulfatide receptor for HIV-1 gp120 on HT-29 cells and thus acts as a competitive inhibitor of virus binding to these CD4- cells, in full agreement with previously published virological data. In contrast, SPC3 does not bind to the CD4 receptor, in agreement with the data showing that the peptide inhibits HIV-1 infection of CD4+ cells by acting at a postattachment step. The binding of SPC3 to LacCer, GM3, and GD3, expressed by CD4+ lymphocytes, suggests a role for these glycosphingolipids in the fusion process between the viral envelope and the plasma membrane of CD4+ cells. Since the multivalent peptide can theoretically bind to several of these glycosphingolipids, we hypothesize that the resulting cross-linking of membrane components may affect the fluidity of the plasma membrane and/or membrane curvature, altering the virus-cell fusion mechanism.
In vitro assay systems which use recombinant retroviral integrase (IN) and short DNA oligonucleotides fail to recapitulate the full-site integration reaction as it is known to occur in vivo. The relevance of using such circumscribed in vitro assays to define inhibitors of retroviral integration has not been formerly demonstrated. Therefore, we analyzed a series of structurally diverse inhibitors with respect to inhibition of both half-site and full-site strand transfer reactions with either recombinant or virion-produced IN. Half-site and full-site reactions catalyzed by avian myeloblastosis virus and human immunodeficiency virus type 1 (HIV-1) IN from virions are shown to be equivalently sensitive to inhibition by compounds which inhibit half-site reactions catalyzed by the recombinant HIV-1 IN. These studies therefore support the utility of using in vitro assays employing either recombinant or virion-derived IN to identify inhibitors of integration.
The chemokine receptors CXCR4 and CCR5 have recently been shown to act as coreceptors, in concert with CD4, for human immunodeficiency
virus–type 1 (HIV-1) infection. RANTES and other chemokines that interact with CCR5 and block infection of peripheral blood
mononuclear cell cultures inhibit infection of primary macrophages inefficiently at best. If used to treat HIV-1–infected
individuals, these chemokines could fail to influence HIV replication in nonlymphocyte compartments while promoting unwanted
inflammatory side effects. A derivative of RANTES that was created by chemical modification of the amino terminus, aminooxypentane
(AOP)–RANTES, did not induce chemotaxis and was a subnanomolar antagonist of CCR5 function in monocytes. It potently inhibited
infection of diverse cell types (including macrophages and lymphocytes) by nonsyncytium-inducing, macrophage-tropic HIV-1
strains. Thus, activation of cells by chemokines is not a prerequisite for the inhibition of viral uptake and replication.
Chemokine receptor antagonists like AOP-RANTES that achieve full receptor occupancy at nanomolar concentrations are strong
candidates for the therapy of HIV-1–infected individuals.
The envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) consists of a complex of gp120 and gp41. gp120 determines viral tropism by binding to target-cell receptors, while gp41 mediates fusion between viral and cellular membranes. Previous studies identified an alpha-helical domain within gp41 composed of a trimer of two interacting peptides. The crystal structure of this complex, composed of the peptides N36 and C34, is a six-helical bundle. Three N36 helices form an interior, parallel coiled-coil trimer, while three C34 helices pack in an oblique, antiparallel manner into highly conserved, hydrophobic grooves on the surface of this trimer. This structure shows striking similarity to the low-pH-induced conformation of influenza hemagglutinin and likely represents the core of fusion-active gp41. Avenues for the design/discovery of small-molecule inhibitors of HIV infection are directly suggested by this structure.
Fusion of viral and cellular membranes by the envelope glycoprotein gp120/gp41 effects entry of HIV-1 into the cell. The precursor, gp160, is cleaved post-translationally into gp120 and gp41 which remain non-covalently associated. Binding to both CD4 and a co-receptor leads to the conformational changes in gp120/gp41 needed for membrane fusion. We used X-ray crystallography to determine the structure of the protease-resistant part of a gp41 ectodomain solubilized with a trimeric GCN4 coiled coil in place of the amino-terminal fusion peptide. The core of the molecule is found to be an extended, triple-stranded alpha-helical coiled coil with the amino terminus at its tip. A carboxy-terminal alpha-helix packs in the reverse direction against the outside of the coiled coil, placing the amino and carboxy termini near each other at one end of the long rod. These features, and the existence of a similar reversal of chain direction in the fusion pH-induced conformation of influenza virus HA2 and in the transmembrane subunit of Moloney murine leukaemia virus (Fig. 1a-d), suggest a common mechanism for initiating fusion.
Certain monoclonal antibodies (MAbs) directed against CD4 can efficiently block HIV-1 replication in vitro. To explore CD4-directed passive immunotherapy for prevention or treatment of AIDS virus infection, we previously examined the biological activity of a nondepleting CD4-specific murine MAb, mu5A8. This MAb, specific for domain 2 of CD4, blocks HIV-1 replication at a post-gp120-CD4 binding step. When administered to normal rhesus monkeys, all CD4+ target cells were coated with antibody, yet no cell clearance or measurable immunosuppression occurred. However, strong anti-mouse Ig responses rapidly developed in all monkeys. In the present study, we report a successfully humanized form of mu5A8 (hu5A8) that retains binding to both human and monkey CD4 and anti-AIDS virus activity. When administered intravenously to normal rhesus monkeys, hu5A8 bound to all target CD4+ cells without depletion and showed a significantly longer plasma half-life than mu5A8. Nevertheless, an anti-hu5A8 response directed predominantly against V region determinants did eventually appear within 2 to 4 weeks in most animals. However, when hu5A8 was administered to rhesus monkeys chronically infected with the simian immunodeficiency virus of macaques, anti-hu5A8 antibodies were not detected. Repeated administration of hu5A8 in these animals resulted in sustained plasma levels and CD4+ cell coating with humanized antibody for 6 weeks. These studies demonstrate the feasibility of chronic administration of CD4-specific MAb as a potential means of treating or preventing HIV-1 infection.
The karyophilic properties of the HIV-1 nucleoprotein complex facilitate infection of nondividing cells such as macrophages and quiescent T lymphocytes, and allow the in vivo delivery of transgenes by HIV-derived retroviral vectors into terminally differentiated cells such as neurons. Although the viral matrix (MA) and Vpr proteins have previously been shown to play important roles in this process, we demonstrate here that integrase, the enzyme responsible for mediating the integration of the viral genome in the host cell chromosome, can suffice to connect the HIV-1 preintegration complex with the cell nuclear import machinery. This novel function of integrase reflects the recognition of an atypical bipartite nuclear localization signal by the importin/karyopherin pathway.
The bicyclam AMD3100 (formula weight 830) blocks HIV-1 entry and membrane fusion via the CXCR4 co-receptor, but not via CCR5. AMD3100 prevents monoclonal antibody 12G5 from binding to CXCR4, but has no effect on binding of monoclonal antibody 2D7 to CCR5. It also inhibits binding of the CXC-chemokine, SDF-1alpha, to CXCR4 and subsequent signal transduction, but does not itself cause signaling and has no effect on RANTES signaling via CCR5. Thus, AMD3100 prevents CXCR4 functioning as both a HIV-1 co-receptor and a CXC-chemokine receptor. Development of small molecule inhibitors of HIV-1 entry is feasible.