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Antiviral Actions of Interferons
Abstract
Tremendous progress has been made in understanding the molecular basis of the antiviral actions of interferons (IFNs), as well as strategies evolved by viruses to antagonize the actions of IFNs. Furthermore, advances made while elucidating the IFN system have contributed significantly to our understanding in multiple areas of virology and molecular cell biology, ranging from pathways of signal transduction to the biochemical mechanisms of transcriptional and translational control to the molecular basis of viral pathogenesis. IFNs are approved therapeutics and have moved from the basic research laboratory to the clinic. Among the IFN-induced proteins important in the antiviral actions of IFNs are the RNA-dependent protein kinase (PKR), the 2',5'-oligoadenylate synthetase (OAS) and RNase L, and the Mx protein GTPases. Double-stranded RNA plays a central role in modulating protein phosphorylation and RNA degradation catalyzed by the IFN-inducible PKR kinase and the 2'-5'-oligoadenylate-dependent RNase L, respectively, and also in RNA editing by the IFN-inducible RNA-specific adenosine deaminase (ADAR1). IFN also induces a form of inducible nitric oxide synthase (iNOS2) and the major histocompatibility complex class I and II proteins, all of which play important roles in immune response to infections. Several additional genes whose expression profiles are altered in response to IFN treatment and virus infection have been identified by microarray analyses. The availability of cDNA and genomic clones for many of the components of the IFN system, including IFN-alpha, IFN-beta, and IFN-gamma, their receptors, Jak and Stat and IRF signal transduction components, and proteins such as PKR, 2',5'-OAS, Mx, and ADAR, whose expression is regulated by IFNs, has permitted the generation of mutant proteins, cells that overexpress different forms of the proteins, and animals in which their expression has been disrupted by targeted gene disruption. The use of these IFN system reagents, both in cell culture and in whole animals, continues to provide important contributions to our understanding of the virus-host interaction and cellular antiviral response.
... Recently, viral proteins in HPV were reported to selectively target nucleic acid-sensing protein complexes, including the stimulator of interferon genes (STING) complex, which strengthens the ability of the virus to control host immunity (6). In addition to their antiviral capabilities, IFN-β exhibits anti-proliferative and apoptotic functions in viral infections, including the Encephalomyocarditis (EMC) virus, vesicular stomatitis virus (VSV), Herpes simplex virus (HSV), and hepatitis C virus (HCV) (7), and in vitro in cancer cell lines, including breast and prostate cancer cell lines. Treatment with crude IFN-I preparations has direct antiproliferative and cell cycle modulatory effects (8). ...
... The selected patients were aged 27 ± 17.1 (6-66) years and represented a mixture of adultand juvenile-onset RRP, harbored RRP driven by HPV types 6 or 11, and displayed variable disease severity as measured by the number of clinically indicated interventions in the 12 months before biopsy and a total number of lifetime surgeries (Table S1). IFN-β serves as the major contributor in defending against viruses by obstructing the replication of numerous viruses (7). To better investigate whether this difference affects the local antiviral response, we examined the local tissue IFN-β levels as well as viral load in surgically resected tumors (Fig. 1B). ...
... Therefore, activating the STING pathway in macrophages might yield an unexpected effect on enhancing their antiviral capacity. In addition to the antiviral effect, IFN-β could also exert antiprolifera tive and proapoptotic functions to interrupt the virus replication strategy in host cells by inducing cell death (7). To further investigate the potential role of macrophage-induced IFN-β in RRP, we used the phorbol 12-myristate 13acetatedifferentiated THP-1 cell line as a macrophage model (24), co-cultured with HPV cells in vitro (Fig. 4B). ...
Recurrent respiratory papillomatosis (RRP) is a rare benign tumor caused mainly by the infection of the respiratory tract epithelial cells by the human papillomavirus (HPV) type 6/11. However, the specific mechanisms underlying the inhibition of the host’s innate immune response by HPV remain unclear. For this purpose, we employed single-cell RNA sequencing to analyze the states of various immune cells in RRP samples post-HPV infection and utilized a cellular model of HPV infection to elucidate the mechanisms by which HPV evades the innate immune system in RRP. The results revealed distinct immune cell heterogeneity in RRP and demonstrated that HPV11 E7 can inhibit the phosphorylation of the stimulator of interferon genes protein, thereby circumventing the body’s antiviral response. In vitro co-culture experiments demonstrated that stimulation of macrophages to produce interferon-beta induced the death of HPV-infected epithelial cells, also reducing HPV viral levels. In summary, our study preliminarily identifies the potential mechanisms by which HPV evades the host’s antiviral immune response, as well as the latent antiviral functions exhibited by activated macrophages. This research serves as an initial exploration of antiviral immune evasion in RRP, laying a solid foundation for investigating immunotherapeutic approaches for the disease.
IMPORTANCE
Surgical tumor reduction is the most common treatment for recurrent respiratory papillomatosis (RRP). One of the characteristics of RRP is its persistent recurrence, and multiple surgeries are usually required to control the symptoms. Recently, some adjuvant therapies have shown effectiveness, but none of them can completely clear human papillomavirus (HPV) infection, and thus, a localized antiviral immune response is significant for disease control; after all, HPV infection is limited to the epithelium. Inhibition of interferon-beta (IFN-β) secretion by HPV11 E7 viral proteins in epithelial cells by affecting stimulator of interferon genes phosphorylation may account for the persistence of low-risk HPV replication in the RRP. Moreover, suppression of the IFN-I pathway in RRP cell types might provide clues regarding the hyporeactive function of local immune cells. However, activation of macrophage groups to produce IFN-β can still destroy HPV-infected cells.
... Os IFNs são divididos em três diferentes grupos: Tipo I (INFs virais): inclui os INF-α (alfa), INF-β (beta) (Bekisz et al., 2004;Klaus et al., 1997) e INF-ω (ômega) (Samuel, 2001). Eles são sintetizados pela maioria das células em resposta à uma infecção viral, agindo como antivirais, antiproliferativos e imunoregulatórios (Goodbourn et al., 2000;Samuel, 2001). ...
... Os IFNs são divididos em três diferentes grupos: Tipo I (INFs virais): inclui os INF-α (alfa), INF-β (beta) (Bekisz et al., 2004;Klaus et al., 1997) e INF-ω (ômega) (Samuel, 2001). Eles são sintetizados pela maioria das células em resposta à uma infecção viral, agindo como antivirais, antiproliferativos e imunoregulatórios (Goodbourn et al., 2000;Samuel, 2001). Tipo II (INFs imunes): inclui os INFs-γ (gama). ...
... Os IFNs imunes atuam na regulação das respostas imunológicas e inflamatórias, além de possuírem efeitos antivirais e antitumorais. Eles também reforçam os resultados dos IFNs Tipo I, recrutando leucócitos para o local da infecção e estimula os macrófagos na eliminação de bactérias (Goodbourn et al., 2000;Samuel, 2001). Tipo III (interleucinas 28/29): esses INFs são produzidos por células dendríticas e monócitos na forma λ (lambda) ou interleucinas 28/29. ...
The feline leukemia virus (FeLV) is a retrovirus that belongs to the genus Gammaretrovirus and exclusively affects felids. The virus carries the reverse transcriptase enzyme, which integrates into the host's DNA permanently, leading to different clinical conditions. The main complications caused by FeLV are hematopoietic neoplasms, immune-mediated disorders, neurological alterations and immunosuppression, among other ailments. The disease has no effective treatment, but antiviral and immunomodulatory drugs are still under trial. Using Recombinant Human Interferon Alpha has shown to be helpful in reducing clinical symptoms and controlling opportunistic infections, increasing the quality and life expectancy of cats infected with FeLV. Retroviruses are among the main causes of death in domestic cats. The lack of knowledge about the disease among guardians and growing cat population in Brazil are helping to increase the number of FeLV cases. Although the disease lacks a universal veterinary medical protocol, there are new studies and information available that can help to treat infected animals, improving their quality of life and expectancy and, in some cases, potentially eliminating the virus. This fact clashes with another reality: outdated professionals who are not familiar with the guidelines for Feline Retrovirus Testing and Management from the AAFP (American Association of Feline Practitioners), an international entity that since 1971 has been working to improve feline health by providing evidence-based guidelines for veterinary practices. Population growth and diseases that exclusively affect the species also highlight the need to include a deeper understanding of feline health in the curricula of undergraduate courses, preparing these future professionals to meet the demand for updated veterinarians with sufficient knowledge to care for the species.
... The activation of the JAK/STAT pathway by interferons involves the transmembrane receptors IFNAR1 and IFNAR2, which are subunits of the interferon protein [11,12]. Interferon Regulatory Factors (IRF3) and (IRF7) stimulate IFNtype 1 production, which, in turn, activates the JAK/STAT pathway through the IFNAR1 and IFNAR2 subunits [13,14]. After activation of the JAK/STAT pathway, JAK 1 and tyrosine kinase 2 bind to the homodimer IFNAR1 and IFNAR2, which form a heterodimer, leading to the phosphorylation of STAT 1/2 [13]. ...
... Interferon Regulatory Factors (IRF3) and (IRF7) stimulate IFNtype 1 production, which, in turn, activates the JAK/STAT pathway through the IFNAR1 and IFNAR2 subunits [13,14]. After activation of the JAK/STAT pathway, JAK 1 and tyrosine kinase 2 bind to the homodimer IFNAR1 and IFNAR2, which form a heterodimer, leading to the phosphorylation of STAT 1/2 [13]. Once phosphorylated, STAT1/2 dissociate from the heterodimer and bind to Interferon Regulatory Factor 9 (IRF9), forming the Interferon Stimulated Gene Factor 3 (ISGF3) complex. ...
... In the nucleus, ISGF3 binds to the Interferon-Stimulated Responsive Element (ISRE), which activates the transcription of Interferon-Stimulated Genes (ISGs) like ISG15, MX1, and MX2. These ISGs play a vital role in antiviral functions [13,14]. ...
The OXTR gene encodes the oxytocin receptor, which is responsible for the attachment of the hormone oxytocin to the cell-surface receptor in endometrial and mammary tissues. In domestic ruminants, such as sheep, the expression of OXTR plays a key role in the initiation of luteolysis, which is the process of degeneration and regression of the corpus luteum in the ovary. This is achieved through a signaling cascade that involves the release of prostaglandin F2. However, the expression of OXTR can be regulated by other hormones, such as progesterone, interferon tau and estradiol. Researcher have been investigating the expression pattern of the OXTR gene at various post-conception days in sheep, and how it correlates with pregnancy persistence. A recent study involving six ewes (one serving as the control) found that the expression of the OXTR gene was significantly higher in non-pregnant and open ewes on days 13, 14 and 15. In contrast, the expression of OXTR gene was not detected on all experimental days in pregnant ewes. In non-pregnant ewes, the expression of OXTR gene was detected at a higher level on day 14 compared to days 13 and 15. These findings suggest that the initial expression of OXTR gene in a non-pregnant ewe is responsible for luteolysis and preparing the animal for the next cycle. On the other hand, in a pregnant ewe, interferon tau is activated in the early days of pregnancy and suppresses OXTR gene expression, which inhibits luteolysis and promotes pregnancy. This is a novel method for detecting early pregnancy in a sheep using blood.
... The authors demonstrated that infected cells produced a secreted factor that induced a virus resistant state. IFNs belong to a large family of multifunctional, secreted proteins involved in antiviral defense, cell growth, differentiation, apoptosis and modulation of immune function through autocrine and paracrine mechanisms (Samuel, 2001) [32] . The IFNs are classified into three distinct types depending on the receptor complex they signal through-type I, II and III. ...
... The authors demonstrated that infected cells produced a secreted factor that induced a virus resistant state. IFNs belong to a large family of multifunctional, secreted proteins involved in antiviral defense, cell growth, differentiation, apoptosis and modulation of immune function through autocrine and paracrine mechanisms (Samuel, 2001) [32] . The IFNs are classified into three distinct types depending on the receptor complex they signal through-type I, II and III. ...
... 1,2 Interferon treatment also demonstrates broad antiviral properties, including the possibility of affecting Epstein Barr virus infection, the primary suspected cause in MS etiology. 3,4 In addition, interferon treatment may promote vaccine responses to severe acute respiratory syndrome coronavirus 2 vaccination, 5 including a subcutaneous pegylated version, peginterferon beta-1a. Pegylation extends the elimination half-life and increases systemic exposure of interferon beta-1a, which permits a reduced dosing frequency. ...
... The safety profile in POP is consistent with that observed in the phase 3 ADVANCE/ATTAIN studies. [2][3][4] No new or unexpected safety signals were reported. Consistent with the phase 3 ADVANCE and ATTAIN studies, 2-4 the most common AEs were ISRs and FLS. ...
Background
Interferon beta-1a remains an important treatment option for multiple sclerosis, particularly when safety or tolerability concerns may outweigh the benefits of higher-efficacy disease-modifying therapies. The five-year phase 4 Plegridy Observational Program (POP) study (NCT02230969) collected data on real-world safety and effectiveness of Plegridy® (peginterferon beta-1a) treatment in patients with relapsing multiple sclerosis.
Objective
To explore the real-world safety and effectiveness of peginterferon beta-1a in patients with relapsing multiple sclerosis, including factors influencing treatment discontinuation.
Methods
Data were collected prospectively from patients ≥ 18 years old with relapsing multiple sclerosis for overall population analysis and for subpopulations including newly/previously diagnosed patients, age, and experience with peginterferon beta-1a. Outcome measures included annualized relapse rates, adverse events, and predictors of time to treatment discontinuation.
Results
Mean (SD) treatment duration in the overall population ( N = 1172) was 896.0 (733.15) days. Incidence of adverse events was higher in new than experienced users (79.4% vs. 57.0%). New users were more likely than experienced users to discontinue (hazard ratio = 1.60; P < 0.0001). The adjusted annualized relapse rate was 0.09, and at the end of 5 years, 77.1% of patients were relapse-free.
Conclusions
Peginterferon beta-1a is an effective therapy for managing relapsing multiple sclerosis. The identification of predictors of discontinuation can help inform strategies to enhance treatment persistence.
... Modeling viral resistance for SARS-CoV-2 during treatment with an anti-spike monoclonal antibody these interferons put target cells into an antiviral state that is refractory to viral infection [31, 69,70]. The antiviral state is not permanent, and the model assumes refractory cells return to being susceptible to infection at a constant rate. ...
... Upon viral infection, infected cells as well as plasmacytoid dendritic cells (not modeled), release type-I and type-III interferons, which put neighboring target cells into an antiviral state, protecting them from viral infection [31, 69,70,80]. Thus, a strong interferon response correlates with strong suppression of viral replication [81]. Previous modeling efforts have captured these effects in a different context [22,41,82]. ...
To mitigate the loss of lives during the COVID-19 pandemic, emergency use authorization was given to several anti-SARS-CoV-2 monoclonal antibody (mAb) therapies for the treatment of mild-to-moderate COVID-19 in patients with a high risk of progressing to severe disease. Monoclonal antibodies used to treat SARS-CoV-2 target the spike protein of the virus and block its ability to enter and infect target cells. Monoclonal antibody therapy can thus accelerate the decline in viral load and lower hospitalization rates among high-risk patients with variants susceptible to mAb therapy. However, viral resistance has been observed, in some cases leading to a transient viral rebound that can be as large as 3–4 orders of magnitude. As mAbs represent a proven treatment choice for SARS-CoV-2 and other viral infections, evaluation of treatment-emergent mAb resistance can help uncover underlying pathobiology of SARS-CoV-2 infection and may also help in the development of the next generation of mAb therapies. Although resistance can be expected, the large rebounds observed are much more difficult to explain. We hypothesize replenishment of target cells is necessary to generate the high transient viral rebound. Thus, we formulated two models with different mechanisms for target cell replenishment (homeostatic proliferation and return from an innate immune response antiviral state) and fit them to data from persons with SARS-CoV-2 treated with a mAb. We showed that both models can explain the emergence of resistant virus associated with high transient viral rebounds. We found that variations in the target cell supply rate and adaptive immunity parameters have a strong impact on the magnitude or observability of the viral rebound associated with the emergence of resistant virus. Both variations in target cell supply rate and adaptive immunity parameters may explain why only some individuals develop observable transient resistant viral rebound. Our study highlights the conditions that can lead to resistance and subsequent viral rebound in mAb treatments during acute infection.
... In this model, we include a population of cells that are refractory to infection, R, and call the model the refractory cell model (RCM). Refractory cells are in an antiviral state induced by the innate immune response mediated by type I and type III interferons [105][106][107]. The following system of ordinary differential equations (ODEs) gives the dynamics of the five populations of the RCM: ...
... This suggests that turning target cells into cells refractory to viral infection by establishing an antiviral state in uninfected cells may be a critical host defense mechanism early on in fighting a viral infection. And indeed, there are several reported mechanisms for a cell to accomplish this [105,107,125,126]. However, as far as we know, experimental measurements of the in vivo fraction of cells in an antiviral state during SARS-CoV-2 (or indeed any other) infection are not available and thus limit our ability to compare these predictions to data. ...
Mathematical models of viral infection have been developed, fitted to data, and provide insight into disease pathogenesis for multiple agents that cause chronic infection, including HIV, hepatitis C, and B virus. However, for agents that cause acute infections or during the acute stage of agents that cause chronic infections, viral load data are often collected after symptoms develop, usually around or after the peak viral load. Consequently, we frequently lack data in the initial phase of viral growth, i.e., when pre-symptomatic transmission events occur. Missing data may make estimating the time of infection, the infectious period, and parameters in viral dynamic models, such as the cell infection rate, difficult. However, having extra information, such as the average time to peak viral load, may improve the robustness of the estimation. Here, we evaluated the robustness of estimates of key model parameters when viral load data prior to the viral load peak is missing, when we know the values of some parameters and/or the time from infection to peak viral load. Although estimates of the time of infection are sensitive to the quality and amount of available data, particularly pre-peak, other parameters important in understanding disease pathogenesis, such as the loss rate of infected cells, are less sensitive. Viral infectivity and the viral production rate are key parameters affecting the robustness of data fits. Fixing their values to literature values can help estimate the remaining model parameters when pre-peak data is missing or limited. We find a lack of data in the pre-peak growth phase underestimates the time to peak viral load by several days, leading to a shorter predicted growth phase. On the other hand, knowing the time of infection (e.g., from epidemiological data) and fixing it results in good estimates of dynamical parameters even in the absence of early data. While we provide ways to approximate model parameters in the absence of early viral load data, our results also suggest that these data, when available, are needed to estimate model parameters more precisely.
... This inhibition of protein translation has a number of downstream effects on IFN signaling, including an increased production of type I interferons, activation of the Jak-STAT pathway, and activation of transcription factors and antiviral genes [34,52,53]. Furthermore, EIF2AK2 levels are induced by type I interferons and poly I:C, which is a double-stranded RNA mimetic and a potent inducer of type I interferons constituting a positive feedback loop [54]. Intratracheal instillation of doublestranded RNA (poly I:C) in mouse lungs induces interferon-stimulated transcription factors and the metabolic gene signature with distinct temporal profiles [33]. ...
... This inhibition of protein translation has a number of downstream effects on IFN signaling, including an increased production of type I interferons, activation of the Jak-STAT pathway, and activation of transcription factors and antiviral genes [34,52,53]. Furthermore, EIF2AK2 levels are induced by type I interferons and poly I:C, which is a double-stranded RNA mimetic and a potent inducer of type I interferons constituting a positive feedback loop [54]. Intratracheal instillation of double-stranded RNA (poly I:C) in mouse lungs induces interferonstimulated transcription factors and the metabolic gene signature with distinct temporal profiles [33]. ...
Respiratory viruses are the causative agents responsible for seasonal epidemics and occasional pandemic outbreaks and are a leading cause of death worldwide. Type I interferon (IFNα/β) signaling in the lung epithelial cells plays a major role in the innate immunity to respiratory viruses. Gene signatures are a set of differentially expressed genes in a particular disease or condition and are used to diagnose, monitor, and predict disease progression. These signatures can be used to identify regulatory modules and gene regulatory networks (GRNs) in mammalian signal transduction pathways. Considerable progress has been made in the identification of type I interferon-regulated gene signatures in the host response to respiratory viruses, including antiviral, immunomodulatory, apoptosis, and transcription factor signatures. Respiratory virus infections and host defenses require a dramatic change in the metabolic flux of macromolecules involved in nucleotide, lipid, and protein metabolism. The profiling of IFN-stimulated metabolic genes induced in the host response to several respiratory viruses led to the identification of a common gene signature in human lung epithelial cells and in the lungs of mouse models of respiratory virus infection. The regulation of the metabolic gene signature was correlated with the induction of IFN-beta (IFN-β) and IFN-inducible transcription factors at the RNA level in lung epithelial cells. Furthermore, the gene signature was also detected in response to bacterial lipopolysaccharide-induced acute lung injury. A protein interaction network analysis revealed that metabolic enzymes interact with IFN-regulated transcription factors and members of the unfolded protein response (UPR) to form a module and potentially regulate type I interferon signaling, constituting a feedback loop. In addition, components of the metabolic gene expression signature were differentially regulated in the lung tissues of COVID-19 patients compared with healthy controls. These results suggest that the metabolic gene signature is a potential therapeutic target for the treatment of respiratory virus infections and inflammatory diseases.
... These subtypes collectively interact with a heterodimeric receptor (IFNAR) consisting of IFNAR1 and IFNAR2 [4,5]. Type II IFN (IFN-II) is represented by IFN gamma (γ) that signals through the IFN gamma receptor complex (IFNGR), consisting of IFNGR1 and IFNGR2 [5][6][7][8]. Type III IFN (IFN-III) includes the IFN lambda (λ)-1-4 subtypes that bind to the heterodimeric IFN lambda receptor (IFNLR), consistent with the IL10RB and IFNLR chains [8][9][10]. IFN-I and IFN-III bind to cell surface receptors, activating intracellular signaling pathways, which include Janus kinase 1 (JAK1), Tyrosine kinase 2 (TYK2) [10][11][12], and signal transducer and activator of transcription (STAT) 1 and STAT2 proteins [13,14]. ...
Background: The Tripartite motif (TRIM) family includes more than 80 distinct human genes. Their function has been implicated in regulating important cellular processes, including intracellular signaling, transcription, autophagy, and innate immunity. During viral infections, macrophages are key components of innate immunity that produce interferons (IFNs) and IL27. We recently published that IL27 and IFNs induce transcriptional changes in various genes, including those involved in JAK-STAT signaling. Furthermore, IL27 and IFNs share proinflammatory and antiviral pathways in monocyte-derived macrophages (MDMs), resulting in both common and unique expression of inflammatory factors and IFN-stimulated genes (ISGs) encoding antiviral proteins. Interestingly, many TRIM proteins have been recognized as ISGs in recent years. Although it is already very well described that TRIM expression is induced by IFNs, it is not fully understood whether TRIM genes are induced in macrophages by IL27. Therefore, in this study, we examined the effect of stimulation with IL27 and type I, II, and III IFNs on the mRNA expression profiles of TRIM genes in MDMs. Methods: We used bulk RNA-seq to examine the TRIM expression profile of MDMs treated with IFNs or IL27. Initially, we characterized the expression patterns of different TRIM subfamilies using a heatmap. Subsequently, a volcano plot was employed to identify commonly differentially expressed TRIM genes. Additionally, we conducted gene ontology analysis with ClueGO to explore the biological processes of the regulated TRIMs, created a gene-gene interaction network using GeneMANIA, and examined protein-protein interactions with the STRING database. Finally, RNA-seq data was validated using RT-qPCR. Furthermore, the effect of IL27 on Mayaro virus replication was also evaluated. Results: We found that IL27, similar to IFNs, upregulates several TRIM genes’ expression in human macrophages. Specifically, we identified three common TRIM genes (TRIM19, 21, and 22) induced by IL27 and all types of human IFNs. Additionally, we performed the first report of transcriptional regulation of TRIM19, 21, 22, and 69 genes in response to IL27. The TRIMs involved a broad range of biological processes, including defense response to viruses, viral life cycle regulation, and negative regulation of viral processes. In addition, we observed a decrease in Mayaro virus replication in MDMs previously treated with IL27. Conclusions: Our results show that IL27, like IFNs, modulates the transcriptional expression of different TRIM-family members involved in the induction of innate immunity and an antiviral response. In addition, the functional analysis demonstrated that, like IFN, IL27 reduced Mayaro virus replication in MDMs. This implies that IL27 and IFNs share many similarities at a functional level. Moreover, identifying distinct TRIM groups and their differential expressions in response to IL27 provides new insights into the regulatory mechanisms underlying the antiviral response in human macrophages.
... Pathogenic microorganisms threaten host homeostasis, and hosts have developed various mechanisms to counteract these pathogens. Interferons (IFNs) have been developed in vertebrate cells to induce proteins that effectively eliminate viruses that invade cells [1][2][3]. IFNs are induced by various stimuli-including melanoma differentiationassociated gene 5 (MDA5), retinoic acid-inducible gene I (RIG-I), and viral RNA-sensing proteins-that are expressed in virus-infected cells [4][5][6]. Genes induced by IFNs are referred to as interferon-stimulated genes (ISGs), and several hundreds of such genes have been identified. ...
2′-5′-oligoadenylate synthetase (OAS) is one of the proteins that act as a defense mechanism against foreign RNA in cells. OAS has two functions: an antiviral effect against a wide range of virus species via the OAS/RNase L pathway with synthesized oligoadenylates and inhibition of viral replication specific to viruses of the genus Flavivirus, which is independent of enzymatic activity. Several birds have been reported to possess only one type of OAS family member, OASL, which has both enzymatic activity and inhibitory effects on flaviviral replication. However, the ostrich has two types of OASs, OAS1 and OASL, which show different functions—enzymatic and anti-flaviviral activities, respectively. In this study, emu OASs were cloned to investigate their sequence and function and elucidate the role of OASs in emus. The cloning results showed that emus had OAS1 and OASL, suggesting that emu OASs were more closely related to ostrich than to other birds. Functional investigations showed that emu OAS1 and OASL had enzymatic and anti-flaviviral activities, respectively, similar to those of the ostrich. Emus and ostriches are evolutionarily different from most birds and may be more closely related to mammalian OAS diversity.
... Ultimately, these intracellular signalling events lead to the production of interferons (IFNs) and proinflammatory cytokines and the activation of other downstream signalling effectors [8,9]. During PRRSV infection, RIG-I/MDA5 recognizes dsRNA and activates type I IFN production to exert antiviral effects [10,11]. Correspondingly, PRRSV has evolved numerous strategies to evade type I IFN restriction. ...
Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), has caused substantial economic losses to the global swine industry due to the lack of effective commercial vaccines and drugs. There is an urgent need to develop alternative strategies for PRRS prevention and control, such as antiviral drugs. In this study, we identified ursonic acid (UNA), a natural pentacyclic triterpenoid from medicinal herbs, as a novel drug with anti-PRRSV activity in vitro. Mechanistically, a time-of-addition assay revealed that UNA inhibited PRRSV replication when it was added before, at the same time as, and after PRRSV infection was induced. Compound target prediction and molecular docking analysis suggested that UNA interacts with the active pocket of PTPN1, which was further confirmed by a target protein interference assay and phosphatase activity assay. Furthermore, UNA inhibited PRRSV replication by targeting PTPN1, which inhibited IFN-β production. In addition, UNA displayed antiviral activity against porcine epidemic diarrhoea virus (PEDV) and Seneca virus A (SVA) replication in vitro. These findings will be helpful for developing novel prophylactic and therapeutic agents against PRRS and other swine virus infections.
... IFNs are now licensed as a therapy for multiple sclerosis [ 43]. Interferon type I induces the expression of interferon-stimulated genes (ISG), which facilitate immune signaling and modulation [ 44]. IFN-1 therapy was examined in SARS-CoV patients and in-vitro, with or without antiviral medications [ 45]. ...
... During viral infections, IFI16 recognizes viral DNA, subsequently inducing the expression of type I interferons (IFNs) [38]. These IFNs play a critical role in alerting neighboring cells to the viral threat and triggering an antiviral state [39]. IFI16's ability to modulate viral infection responses demonstrates its dynamic regulatory role in host defense mechanisms. ...
Interferon Gamma Inducible Protein 16 (IFI16) belongs to the HIN-200 protein family and is pivotal in immunological responses. Serving as a DNA sensor, IFI16 identifies viral and aberrant DNA, triggering immune and inflammatory responses. It is implicated in diverse cellular death mechanisms, such as pyroptosis, apoptosis, and necroptosis. Notably, these processes are integral to the emergent concept of PANoptosis, which encompasses cellular demise and inflammatory pathways. Current research implies a significant regulatory role for IFI16 in PANoptosis, particularly regarding cardiac pathologies. This review delves into the complex interplay between IFI16 and PANoptosis in heart diseases, including atherosclerosis, myocardial infarction, heart failure, and diabetic cardiomyopathy. It synthesizes evidence of IFI16’s impact on PANoptosis, with the intention of providing novel insights for therapeutic strategies targeting heart diseases.
... These include Apolipoprotein B Editing Complex 3 (APOBEC3)-, guanylate-binding protein (GBP)-, IFN-inducible (IFI)-, IFN-induced proteins with tetratricopeptide repeats (IFIT)-, IFN-induced transmembrane (IFITM)-, dynamin-like GTPase (MX)-, and oligoadenylate synthase (OAS)-family proteins, together with indoleamine-pyrrole 2,3-dioxygenase 1 (IDO1), ISG15, ISG20, double-stranded RNA-activated protein kinase R (PKR), tetherin, viperin, and others. These AVPs function at various stages of viral replication, including viral entry, replication, assembly, budding, and their spread into the tissues (2)(3)(4)(5)(6). Although the field has mostly focused on ISGs/AVPs, current knowledge indicates that IFNs exhibit a broad spectrum of functions. ...
Interferons (IFNs) are a family of cytokines that activate the JAK-STAT signaling pathway to induce an antiviral state in cells. Interleukin 27 (IL-27) is a member of the IL-6 and/or IL-12 family that elicits both pro- and anti-inflammatory responses. Recent studies have reported that IL-27 also induces a robust antiviral response against diverse viruses, both in vitro and in vivo, suggesting that IFNs and IL-27 share many similarities at the functional level. However, it is still unknown how similar or different IFN- and IL-27-dependent signaling pathways are. To address this question, we conducted a comparative analysis of the transcriptomic profiles of human monocyte-derived macrophages (MDMs) exposed to IL-27 and those exposed to recombinant human IFN-α, IFN-γ, and IFN-λ. We utilized bioinformatics approaches to identify common differentially expressed genes between the different transcriptomes. To verify the accuracy of this approach, we used RT-qPCR, ELISA, flow cytometry, and microarrays data. We found that IFNs and IL-27 induce transcriptional changes in several genes, including those involved in JAK-STAT signaling, and induce shared pro-inflammatory and antiviral pathways in MDMs, leading to the common and unique expression of inflammatory factors and IFN-stimulated genes (ISGs)Importantly, the ability of IL-27 to induce those responses is independent of IFN induction and cellular lineage. Additionally, functional analysis demonstrated that like IFNs, IL-27-mediated response reduced chikungunya and dengue viruses replication in MDMs. In summary, IL-27 exhibits properties similar to those of all three types of human IFN, including the ability to stimulate a protective antiviral response. Given this similarity, we propose that IL-27 could be classified as a distinct type of IFN, possibly categorized as IFN-pi (IFN-π), the type V IFN (IFN-V).
... The IFN response represents an early defense of the host and occurs before the onset of the immune response. IFN has a wide range of biological activities in addition to the characteristics of its antiviral activity (65,66). ...
The high recurrence rate and poor prognosis of non-muscle invasive bladder cancer (BC) are challenges that need to be urgently addressed. Transurethral cystectomy for bladder tumors is often combined with bladder perfusion therapy, which can effectively reduce the recurrence and progression rates of BC. The present review integrated and analyzed currently available bladder perfusion drugs, mainly including chemotherapeutic agents, immunotherapeutic agents and other adjuvant perfusion drugs. Bacillus Calmette-Guerin (BCG) perfusion was the pioneering immunotherapy for early BC and still ranks high in the selection of perfusion drugs. However, BCG infusion has a high toxicity profile and has been shown to be ineffective in some patients. Due to the limitations of BCG, new bladder perfusion drugs are constantly being developed. Immunotherapeutic agents have opened a whole new chapter in the selection of therapeutic agents for bladder perfusion. The present review explored the mechanism of action, clinical dosage and adverse effects of a variety of bladder perfusion drugs currently in common use, described combined perfusion and compared the effects of certain drugs on BC.
... Correspondingly, IFN-γ levels were significantly lower in the sera or lung tissue of FPS-ZM1-treated mice than those of mice with PDPT on day 7 post infection, while higher in the sera of FPS-ZM1-treated mice than those of mice with PDPT on day3 post infection, and similar results were presented in mice treated with oseltamivir. The IFN response, an early defense response of the host，may stimulate innate cells to mediate host immunity through NK cells and accelerate specific cytotoxic immunity, and activate macrophages to exert antiviral effects through the recognition of viral antigens bound to the MHC-associated cell surface [47]. Whereas, IFN-γ is a mediator of immune depletion and acute lung injury in severe influenza virus infection, and anti-IFN-γ therapy could reduce the severity of influenza virus-induced immunopathology [48,49]. ...
... Interferons can be employed to enhance the host's antiviral defenses, stimulating the expression of antiviral proteins within cells [24]. Some antiviral strategies focus on host factors essential for viral replication, such as drugs targeting host cell receptors. ...
This review explores the distinctive challenges and novel strategies associated with antiviral drug discovery, highlighting the unique aspects that set it apart from other therapeutic areas. Antiviral drugs face the daunting task of addressing the remarkable diversity among viruses, which exhibit a broad range of structures, replication strategies, and genetic compositions. Unlike bacteria, viruses lack independent cellular machinery, making it imperative to design drugs that selectively target viral components without compromising host cell integrity. The constant threat of viral mutation adds complexity to drug development, necessitating continuous surveillance and adaptive approaches to combat emerging drug-resistant strains. A comprehensive understanding of host-pathogen interactions is pivotal for identifying potential drug targets, often involving interference with specific stages of the viral lifecycle. The review emphasizes the importance of computational tools, such as molecular modeling and virtual screening, in unraveling complex viral structures and facilitating the identification of promising drug candidates. Additionally, the review delves into the challenges posed by viruses that establish latent or persistent infections, requiring drug development strategies that address both active replication and dormant phases. Collaborative research efforts and global surveillance emerge as essential components in the battle against emerging viral threats. Despite economic considerations, the urgency of managing viral outbreaks underscores the necessity for innovative approaches, international cooperation, and sustained research endeavors in the field of antiviral drug discovery. This comprehensive examination sheds light on the multifaceted nature of antiviral drug discovery, providing insights into the dynamic and evolving landscape of this critical therapeutic discipline.
... The activation of the cGAS-STING pathway has been shown to suppress SARS-CoV-2 replication via recognizing cytoplasmic chromatin of infected cells [9] and also enhances the effects of irradiation by controlling ROS homeostasis and DNA damage [10]. Additionally, multiple RNA sensing pathways have been reported to have synergistic effects in resisting viral infection by recognizing both endogenous and exogenous double-stranded RNA (dsRNA), including RNA sensor RIG-1 (RIG1) and mitochondrial antiviral signaling protein (MAVS) pathway [11], 2 -5 -oligoadenylate synthetase (OAS) and RNase L pathway [12], and others. These pathways recognize endogenous RNA induced by genotoxic stress as if they are the exogenous RNA pathogen [13]. ...
Ionizing radiation (IR) induces severe hematopoietic injury by causing DNA and RNA damage as well as activating the immune responses, necessitating the development of effective therapeutic strategies. Ribonuclease L (RNase L) as an innate immune response pathway is triggered by exogenous and endogenous abnormal dsRNA under viral infection and dyshomeostasis, thereby activating the immune responses. Thus, we investigated the effect of RNase L on irradiation-induced bone marrow damage using RNase L knockout (RNase L−/−) mice. Phenotypic analysis revealed that RNase L knockout mitigates irradiation-induced injury in the bone marrow. Further investigation into the mechanism of RNase L by RNA-seq, qRT-PCR, and CBA analysis demonstrated that RNase L deficiency counteracts the upregulation of genes related to immune responses induced by irradiation, including cytokines and interferon-stimulated genes. Moreover, RNase L deficiency inhibits the increased levels of immunoglobulins in serum induced by irradiation. These findings indicate that RNase L plays a role in the immune response induced by irradiation in the bone marrow. This study further enhances our understanding of the biological functions of RNase L in the immune response induced by irradiation and offers a novel approach for managing irradiation-induced bone marrow injury through the regulation of RNase L activation.
... It is well documented that type I IFN and type II IFN are important in antiviral immunity (33). We have demonstrated that SIRT1 is a negative regulator in both type I and type II IFN-induced signaling. ...
Type I and type II IFNs are important immune modulators in both innate and adaptive immunity. They transmit signaling by activating JAK-STAT pathways. Sirtuin 1 (SIRT1), a class III NAD⁺-dependent deacetylase, has multiple functions in a variety of physiological processes. Here, we characterized the novel functions of SIRT1 in the regulation of type I and type II IFN-induced signaling. Overexpression of SIRT1 inhibited type I and type II IFN-induced interferon-stimulated response element activation. In contrast, knockout of SIRT1 promoted type I and type II IFN-induced expression of ISGs and inhibited viral replication. Treatment with SIRT1 inhibitor EX527 had similar positive effects. SIRT1 physically associated with STAT1 or STAT3, and this interaction was enhanced by IFN stimulation or viral infection. By deacetylating STAT1 at K673 and STAT3 at K679/K685/K707/K709, SIRT1 downregulated the phosphorylation of STAT1 (Y701) and STAT3 (Y705). Sirt1+/− primary peritoneal macrophages and Sirt1+/− mice exhibited enhanced IFN-induced signaling and antiviral activity. Thus, SIRT1 is a novel negative regulator of type I and type II IFN-induced signaling through its deacetylase activity.
IMPORTANCE
SIRT1 has been reported in the precise regulation of antiviral (RNA and DNA) immunity. However, its functions in type I and type II IFN-induced signaling are still unclear. In this study, we deciphered the important functions of SIRT1 in both type I and type II IFN-induced JAK-STAT signaling and explored the potential acting mechanisms. It is helpful for understanding the regulatory roles of SIRT1 at different levels of IFN signaling. It also consolidates the notion that SIRT1 is an important target for intervention in viral infection, inflammatory diseases, or even interferon-related therapies.
... Vertebrates have evolved biological systems to combat invading pathogens and the innate immune system is the first barrier of host defense to against the microbial pathogens invasion. IFNs are the foundation of the host defense to viral infections through binding to the IFNs receptors on the cell surface, which initiate the downstream Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway and lead to the induction of a wide array of ISGs [4,[7][8][9][10][11]. The mechanisms behind the antiviral effects of many ISGs have been described. ...
Background
Viral infection elicits the type I interferon (IFN-I) response in host cells and subsequently inhibits viral infection through inducing hundreds of IFN-stimulated genes (ISGs) that counteract many steps in the virus life cycle. However, most of ISGs have unclear functions and mechanisms in viral infection. Thus, more work is required to elucidate the role and mechanisms of individual ISGs against different types of viruses.
Results
Herein, we demonstrate that poliovirus receptor-like protein4 ( PVRL4 ) is an ISG strongly induced by IFN-I stimulation and various viral infections. Overexpression of PVRL4 protein broadly restricts growth of enveloped RNA and DNA viruses, including vesicular stomatitis virus (VSV), herpes simplex virus 1 (HSV-1), influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) whereas deletion of PVRL4 in host cells increases viral infections. Mechanistically, it suppresses viral entry by blocking viral-cellular membrane fusion through inhibiting endosomal acidification. The vivo studies demonstrate that Pvrl4 -deficient mice were more susceptible to the infection of VSV and IAV.
Conclusion
Overall, our studies not only identify PVRL4 as an intrinsic broad-spectrum antiviral ISG, but also provide a candidate host-directed target for antiviral therapy against various viruses including SARS-CoV-2 and its variants in the future.
... These results again suggested that EA can respond to PEDV infection through immunomodulatory effects. IFN-b is one kind of type I interferon that responses mainly by inducing the expression of IFN stimulate gene (ISGs) and producing a variety of antiviral factors, which not only has a direct antiviral effect, but also has a certain immune enhancement function (30). IFIT1 is a member of the interferoninduced protein with tetratricopeptide repeats family (IFITs) and it has extensive antiviral activity and anti-inflammatory effect. ...
The present study was conducted to decipher the protection effects of ellagic acid (EA) on piglets infected with porcine epidemic diarrhea virus (PEDV). Thirty 7-day-old piglets were randomly assigned to three treatment groups: control, PEDV, and EA + PEDV groups. After a 3-day period of adaption, piglets in the EA + PEDV group were orally administered with 20 mg/kg·BW EA during days 4-11 of the trial. On day 8, piglets were orally administered with PEDV at a dose of 10⁶ TCID50 (50% tissue culture infectious dose) per pig. Additionally, intestinal porcine epithelial (IPEC-1) cells infected with PEDV were used to investigate the anti-PEDV effect of EA in vitro. The results showed that EA at a dose of 10-40 μmol/L increased the viability of PEDV-infected IPEC-1 cells, and EA administration mitigated intestinal edema in piglets challenged with PEDV. Further studies indicated that EA treatment significantly increased the proportion of white blood cells in blood and concentrations of IL-6, IL-1β, and IL-10 in the serum, but decreased the TNF-α content and gene expression of IL-6, IL-1β, TNF-α, and CXCL2 in the jejunum. Moreover, EA intervention considerably elevated the activity of total superoxide dismutase (T-SOD), but decreased the H2O2 concentration in the ileum of piglets. Importantly, EA suppressed the increased expression of antiviral-related genes and proteins (including MXI, ISG15, HSP70, and p-IRF7) induced by PEDV challenge in the jejunum. Furthermore, PEDV infection increased the protein abundance of p-JAK2 and p-STAT3, which were further enhanced by EA supplementation. In conclusion, our results revealed that EA could promote the restoration of intestinal homeostasis by regulating the interferon pathway that was interrelated with the activation of JAK2/STAT3 signaling. These findings provide theoretical basis for the use of EA as a therapy targeting PEDV infection in piglets.
... IFNs secreted from infected cells bind to the IFNAR resulting in activation of JAK1 and TYK2 that phosphorylate STAT1 and STAT2 proteins. Phosphorylated STAT1/STAT2, together with IRF9, constitute the IFN-stimulated gene factor-3 (ISGF3) complex that binds to IFN-sensitive response element (ISRE) promoters resulting in the expression of hundreds of ISGs, including, among others, IFN-induced myxovirus resistance proteins (Mxs), IFNinduced transmembrane (IFITM), PKR, and OAS-RNase L to restrict virus replication (Samuel, 2001;Schneider and Sari, 2014) (Figure 5). ...
Following virus recognition of host cell receptors and viral particle/genome internalization, viruses replicate in the host via hijacking essential host cell machinery components to evade the provoked antiviral innate immunity against the invading pathogen. Respiratory viral infections are usually acute with the ability to activate pattern recognition receptors (PRRs) in/on host cells, resulting in the production and release of interferons (IFNs), proinflammatory cytokines, chemokines, and IFN-stimulated genes (ISGs) to reduce virus fitness and mitigate infection. Nevertheless, the game between viruses and the host is a complicated and dynamic process, in which they restrict each other via specific factors to maintain their own advantages and win this game. The primary role of the non-structural protein 1 (NS1 and Nsp1) of influenza A viruses (IAV) and the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively, is to control antiviral host-induced innate immune responses. This review provides a comprehensive overview of the genesis, spatial structure, viral and cellular interactors, and the mechanisms underlying the unique biological functions of IAV NS1 and SARS-CoV-2 Nsp1 in infected host cells. We also highlight the role of both non-structural proteins in modulating viral replication and pathogenicity. Eventually, and because of their important role during viral infection, we also describe their promising potential as targets for antiviral therapy and the development of live attenuated vaccines (LAV). Conclusively, both IAV NS1 and SARS-CoV-2 Nsp1 play an important role in virus–host interactions, viral replication, and pathogenesis, and pave the way to develop novel prophylactic and/or therapeutic interventions for the treatment of these important human respiratory viral pathogens.
... On the other hand, it has been shown that the severity of host antiviral response could affect the productivity of virus. 20,21 Kinetic studies on rAAV production hence need to be global, at both virus and host cell levels. To that end, a proteomic study using label-free quantification on host cell proteins showed altered proliferation and metabolism upon rAAV production using triple plasmid transfection. ...
Recombinant adeno‐associated virus (rAAV) is among the most commonly used vectors for gene therapy. It is commonly produced by transfection of HEK293 cells with three plasmids each containing the vector genome including gene of interest (GOI), helper functions, and rep and cap genes for genome replication and capsid formation. To meet the potential clinical needs, the productivity of the production system needs to be enhanced. A better process characterization of the production system will further advance our insights into ways to enhance productivity. Here, we employed transcriptomic analysis to quantify the dynamics of different isoforms of viral transcripts and to assess the shift of cellular physiology, and deployed targeted proteomic analysis for absolute quantification of viral proteins and tandem mass tags (TMTs) for assessing cellular responses at the protein level. Functional analysis at transcriptome and proteome levels identified defense and immune response, unfolded protein response, p53 signaling as enriched. The small molecule additive intervention study based on functional analysis showed the potential of such omics‐guided productivity enhancement. Together, multi‐omics analysis advanced understanding of rAAV production and provided insight into enhancing rAAV production by plasmid transfection.
... Interferons, which prevent the generation of viruses in infected cells, are among the most well-known medications in this group [22]. "Interferon alpha" is a well-known kind of human interferon that is frequently used in the standard care for hepatitis B and C and other interferons are also being investigated as treatments for various diseases [23]. ...
Background Ayurved, an ancient system of medicine with rich heritage and antiquity, is well known since Vedic period. Viral infections are responsible for many illnesses, and recent outbreaks have raised public health concerns. Viral infections are being managed therapeutically through available antiviral regimens with unsatisfactory clinical outcomes. The refractory viral infections immune to available antiviral drugs are alarming threats and a significant health concern. For hepatitis, the interferon and vaccine therapies solely aren't ultimate solutions thanks to recurrence of hepatitis C virus. Owing to the growing incidences of viral infections and particularly of resistant viral strains, the available therapeutic modalities got to be improved, complemented with the invention of novel antiviral agents to combat refractory viral infections. It is widely accepted that medicinal plant heritage is nature gifted, precious, and fueled with the valuable resources for treatment of metabolic and infectious disorders. The aims of this review are to assemble the facts and to conclude the therapeutic potential of medicinal plants within the eradication and management of various viral diseases such as influenza, human immunodeficiency virus (HIV), herpes simplex virus (HSV), hepatitis, and coxsackievirus infections, which have been proven in diverse clinical studies. The scientific literature mainly focusing on plant extracts and herbal products with therapeutic efficacies against experimental models of influenza, HIV, HSV, hepatitis, and coxsackievirus were included in the study. Pure compounds possessing antiviral activity were excluded, and plants possessing activity against viruses other than viruses in inclusion criteria were excluded. Hundreds of plant extracts with antiviral effect were recognized. On the basis of the work of several independent research groups, the therapeutic potential of medicinal plants against listed common viral diseases in the region has been proclaimed. In this context, the herbal formulations as alternative medicine may contribute to the eradication of complicated viral infection significantly. The current review consolidates the data of the various medicinal plants, holding promising specific antiviral activities scientifically proven through studies on experimental animal models. Consequently, the original research addressing the development of novel nutraceuticals based on listed medicinal plants is highly recommended for the management of viral disorders
... a protective response to contrast inflammatory injury as demonstrated by elevated levels of pro-inflammatory cytokines we also detected in the hypothalamus (IFN-γ, IL-6, IL-16, and IP-10). IFN-β also possesses anti-viral properties [35], and the fact that ontologies such as "response to virus", "Epstein-Barr virus infection", and "Coronavirus disease" are enriched in our gene expression dataset pinpoints a possible molecular overlap between autoimmune demyelination and viral challenges. In this light, it is intriguing that Epstein-Barr virus (EBV) infection has been recently characterized as the main environmental factor for MS susceptibility [36]. ...
The hypothalamus is a brain structure that is deputed to maintain organism homeostasis by regulating autonomic function and hormonal production as part of the neuroendocrine system. Dysfunction in hypothalamic activity results in behavioral alterations, depression, metabolic syndromes, fatigue, and infertility. Remarkably, many of these symptoms are associated with multiple sclerosis (MS), a chronic autoimmune disorder of the central nervous system (CNS) characterized by focal demyelination, immune cell infiltration into the brain parenchyma, and neurodegeneration. Furthermore, altered hormonal levels have been documented in MS patients, suggesting the putative involvement of hypothalamic deficits in MS clinical manifestations. Yet, a systematic analysis of hypothalamic function in response to neuroinflammatory stress is still lacking. To fill this gap, here we performed a longitudinal profiling of the hypothalamic transcriptome upon experimental autoimmune encephalomyelitis (EAE)-a murine disease model recapitulating key MS phenotypes at both histopathological and molecular levels. We show that changes in gene expression connected with an anti-inflammatory response start already at pre-onset and persist along EAE progression. Altered levels of hypothalamic neuropeptides were also detected, which possibly underlie homeostatic responses to stress and aberrant feeding behaviors. Last, a thorough investigation of the principal endocrine glands highlighted defects in the main steroidogenic pathways upon disease. Collectively, our findings corroborate the central role of hypothalamic dysfunction in CNS autoimmunity.
... It can regulate the presentation of antigens, promotion of inflammation, and activation and polarization of responding leukocytes. Besides, it also exerts direct antiproliferative effects on T cells 6 . Interestingly, IFNγ has been classically considered a pro-inflammatory cytokine, which negatively regulates anti-inflammatory responses by antagonizing the IL10 and TGF-β signaling pathways to suppress the Treg cell function 7 . ...
Targeting tumor-infiltrating regulatory T cells (Tregs) is an efficient way to evoke an anti-tumor immune response. However, how Tregs maintain their fragility and stability remains largely unknown. IFITM3 and STAT1 are interferon-induced genes that play a positive role in the progression of tumors. Here, we showed that IFITM3-deficient Tregs blunted tumor growth by strengthening the tumor-killing response and displayed the Th1-like Treg phenotype with higher secretion of IFNγ. Mechanistically, depletion of IFITM3 enhances the translation and phosphorylation of STAT1. On the contrary, the decreased IFITM3 expression in STAT1-deficient Tregs indicates that STAT1 conversely regulates the expression of IFITM3 to form a feedback loop. Blocking the inflammatory cytokine IFNγ or directly depleting STAT1-IFITM3 axis phenocopies the restored suppressive function of tumor-infiltrating Tregs in the tumor model. Overall, our study demonstrates that the perturbation of tumor-infiltrating Tregs through the IFNγ-IFITM3-STAT1 feedback loop is essential for anti-tumor immunity and constitutes a targetable vulnerability of cancer immunotherapy.
... Our previous studies have identified that MX Dynamin Like GTPase 1 (MX1), involved in I-IFN activation, may partially contribute to the functional disorders observed in DS derived amniocytes (DSACs) through transcriptome analysis. Interestingly, MX1 not only belongs to the known I-IFN inducible effector genes [19,20], but it is also located on chr21, and has been demonstrated shown to be highly expressed in DS [21]. However, the role of MX1 in DS pathogenesis remains elusive. ...
Background
Growing evidence has suggested that Type I Interferon (I-IFN) plays a potential role in the pathogenesis of Down Syndrome (DS). This work investigates the underlying function of MX1, an effector gene of I-IFN, in DS-associated transcriptional regulation and phenotypic modulation.
Methods
We performed assay for transposase-accessible chromatin with high-throughout sequencing (ATAC-seq) to explore the difference of chromatin accessibility between DS derived amniocytes (DSACs) and controls. We then combined the annotated differentially expressed genes (DEGs) and enriched transcriptional factors (TFs) targeting the promoter region from ATAC-seq results with the DEGs in RNA-seq, to identify key genes and pathways involved in alterations of biological processes and pathways in DS.
Results
Binding motif analysis showed a significant increase in chromatin accessibility of genes related to neural cell function, among others, in DSACs, which is primarily regulated by members of the activator protein-1 (AP-1) transcriptional factor family. Further studies indicated that MX Dynamin Like GTPase 1 (MX1), defined as one of the key effector genes of I-IFN, is a critical upstream regulator. Its overexpression induced expression of AP-1 TFs and mediated inflammatory response, thus leading to decreased cellular viability of DS cells. Moreover, treatment with specific AP-1 inhibitor T-5224 improved DS-associated phenotypes in DSACs.
Conclusions
This study demonstrates that MX1-mediated AP-1 activation is partially responsible for cellular dysfunction of DS. T-5224 effectively ameliorated DS-associated phenotypes in DSACs, suggesting it as a potential treatment option for DS patients.
Supplementary Information
The online version contains supplementary material available at 10.1186/s40659-023-00474-x.
... Thus, IFN-α mediates antiviral actions by inhibiting the virion cycle and promoting enzyme synthesis, which interferes with viral particle transport, viral DNA transcription, replication, or RNA translation [11,12]. ...
For more than three decades, IFN-α2b has been widely used for the treatment of multiple human viral infections such as chronic hepatitis B and C, and certain types of cancers. However, IFN-α2b can be immunogenic, and these undesired immune responses can lead to a decrease in therapeutic efficacy. In addition, IFN-α therapy has also been associated with the progression of certain autoimmune diseases. For these reasons, the development of new IFN-α2b versions with reduced (or even null) immunogenicity has become the focus of several investigations. The “de-immunization” strategies usually involve several steps starting with T cell epitope identification and mutation of those immunogenic residues using immuno-informatics tools. Then, further experimental validation through in vitro and in vivo experimental platforms is needed to confirm in silico predictions. In this chapter, we will review the main strategies addressed so far to develop more effective and safer IFN-based therapies.
... The primary innate host defense against viral infections of all types is the interferon (IFN) family of cytokines (12)(13)(14)(15). The question arises as to whether the IFN system plays some significant role in host defense against SARS-CoV2 induced COVID19? ...
The field of antiviral therapeutics is fixated on COVID19 and rightly so as the fatalities at the height of the pandemic in the United States were almost 1,000,000 in a twelve month period spanning parts of 2020/2021. A coronavirus called SARS–CoV2 is the causative virus. Development of a vaccine through molecular biology approaches with mRNA as the inducer of virus spike protein has played a major role in driving down mortality and morbidity. Antivirals have been of marginal value in established infections at the level of hospitalization. Thus, the current focus is on early symptomatic infection of about the first five days. The Pfizer drug paxlovid which is composed of nirmatrelvir, a peptidomimetic protease inhibitor of SARS–CoV2 Mpro enzyme, and ritonavir to retard degradation of nirmatrelvir, is the current FDA recommended treatment of early COVID19. There is no evidence of broad antiviral activity of paxlovid against other diverse viruses such as the influenza virus, poxviruses, as well as a host of respiratory viruses. Although type I interferons (IFNs) are effective against SARS–CoV2 in cell cultures and in early COVID19 infections, they have not been broadly recommended as therapeutics for COVID19. We have developed stable peptidomimetics of both types I and II IFNs based on our noncanonical model of IFN signaling involving the C-terminus of the IFNs. We have also identified two members of intracellular checkpoint inhibitors called suppressors of cytokine signaling (SOCS), SOCS1 and SOCS3 (SOCS1/3), and shown that they are virus induced intrinsic virulence proteins with activity against IFN signaling enzymes JAK2 and TYK2. We developed a peptidomimetic antagonist, based on JAK2 activation loop, against SOCS1/3 and showed that it synergizes with the IFN mimetics for potent broad spectrum antiviral activity without the toxicity of intact IFN molecules. IFN mimetics and the SOCS1/3 antagonist should have an advantage over currently used antivirals in terms of safety and potency against a broad spectrum of viruses.
Coronavirus disease 2019 (COVID-19) continues to cause morbidity and mortality worldwide; therefore, effective treatments remain crucial to controlling it. As interferon-alpha (IFN-α) and -beta (β) have been proposed as COVID-19 treatments, we sought to assess their effectiveness on respiratory, cardiovascular, neurological, and psychiatric signs and symptoms, as well as PASC and death, in hospitalized COVID-19 patients without multiple sclerosis (MS). Using a federated data research network (TriNetX), we performed a retrospective cohort study of hospitalized COVID-19 patients without MS who received IFN-α or -β treatment, comparing them to a similar cohort who did not receive treatment. Following propensity-score matched analyses, we demonstrate that hospitalized COVID-19 patients who were treated with IFN-α or -β had significantly higher odds of death. In contrast, there was no significant difference in any other outcomes between 1–30 days or 1 day to anytime afterward. Overall, hospitalized COVID-19 patients without MS who were treated with IFN-α or -β had similar short- and long-term sequelae (except for mortality) as those who did not receive treatment. The potential benefits of utilizing IFN-α or -β treatment as therapeutics remain to be realized, and our research highlights the need to explore repurposing drugs for COVID-19 using real-world evidence.
Senecavirus A (SVA), a picornavirus, causes vesicular diseases and epidemic transient neonatal losses in swine, resulting in a multifaceted economic impact on the swine industry. SVA counteracts host antiviral response through multiple strategies facilitatng viral infection and transmission. However, the mechanism of how SVA modulates interferon (IFN) response remains elusive. Here, we demonstrate that SVA 3C protease (3C pro ) blocks the transduction of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway to antagonize type I IFN response. Mechanistically, 3C pro selectively cleaves and degrades STAT1 and STAT2 while does not target JAK1, JAK2, and IRF9, through its protease activity. Notably, SVA 3C pro cleaves human and porcine STAT1 on a Leucine (L)-Aspartic acid (D) motif, specifically L693/D694. In the case of STAT2, two cleavage sites were identified: glutamine (Q) 707 was identified in both human and porcine, while the second cleavage pattern differed, with residues 754–757 (Valine-Leucine-Glutamine-Serine motifs) in human STAT2 and Q758 in porcine STAT2. These cleavage patterns by SVA 3C pro partially differ from previously reported classical motifs recognized by other picornaviral 3C pro , highlighting the distinct characteristics of SVA 3C pro . Together, these results reveal a mechanism by which SVA 3C pro antagonizes IFN-induced antiviral response but also expands our knowledge about the substrate recognition patterns for picornaviral 3C pro .
IMPORTANCE
Senecavirus A (SVA), the only member in the Senecavirus genus within the Picornaviridae family, causes vesicular diseases in pigs that are clinically indistinguishable from foot-and-mouth disease (FMD), a highly contagious viral disease listed by the World Organization for Animal Health (WOAH). Interferon (IFN)-mediated antiviral response plays a pivotal role in restricting and controlling viral infection. Picornaviruses evolved numerous strategies to antagonize host antiviral response. However, how SVA modulates the JAK-STAT signaling pathway, influencing the type I IFN response, remains elusive. Here, we identify that 3C pro , a protease of SVA, functions as an antagonist for the IFN response. 3C pro utilizes its protease activity to cleave STAT1 and STAT2, thereby diminishing the host IFN response to promote SVA infection. Our findings underscore the significance of 3C pro as a key virulence factor in the antagonism of the type I signaling pathway during SVA infection.
Abstract
Background
The severe acute respiratory syndrome Coronavirus-2 causing COVID-19 viral infection was first reported in late December 2019, spreading swiftly across all over the world. WHO declared it a pandemic by March 2020. Many problems emerged worldwide healthcare system and economic burden due to viral outbreak. High transmission rate and infectious nature make COVID-19 pandemic. Effectively managing outbreak and controlling spread is challenging. Despite valiant efforts to contain the COVID-19 outbreak, the situation has deteriorated to the point that there were no viable preventive therapies to treat this disease. Developing effective treatment for COVID-19 has been a complex and ongoing endeavor.
Objective
The aim of this systematic review is to evaluate the structure, epidemiology, pathophysiology, potential therapeutic treatments, and preventive measures adopted in Traditional Chinese Medicine (TCM) in the management of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus.
Methods
A systematic methodology has been adopted in this study following PRISMA guidelines. Several keywords like “COVID-19” “SARS-CoV-2” “Coronavirus” and “Traditional Chinese Medicine” were searched in various databases like ScienceDirect, Google Scholar, PubMed, and ResearchGate during the time span of 2010-2023. Clinical trials and studies relevant to this study were identified through a systematic search strategy following PRISMA methodology.
Results
In this systematic review, after careful evaluation and reviewing of literature through PRISMA guidelines, 145 relevant studies were identified, reviewed and included in this systematic review. A detailed study has been summarized on virus structure, etiology, epidemiology characteristics, pathophysiology, and potential therapeutic treatments and preventive measures adopted in Traditional Medicinal System in the treatment of infected COVID-19 patients.
Conclusion
SARS-CoV-2 transmission dynamics and pathogenesis were revealed by the etiology analysis. COVID-19 symptoms and severe disease outcomes can be managed with certain repurposed drugs, Traditional Medicinal System and antivirals, which have been shown to be effective in treating COVID-19 infection.
Type I Interferons (IFNs) generally have a protective role during viral infections, but their function during bacterial infections is dependent on the bacterial species. Legionella pneumophila , Shigella sonnei and Mycobacterium tuberculosis can inhibit type I IFN signaling. Here we examined the role of type I IFN, specifically IFNβ, in the context of Salmonella enterica serovar Typhimurium (STm) macrophage infections and the capacity of STm to inhibit type I IFN signaling. We demonstrate that IFNβ has no effect on the intracellular growth of STm in infected bone marrow derived macrophages (BMDMs) derived from C57BL/6 mice. STm infection inhibits IFNβ signaling but not IFNγ signaling in a murine macrophage cell line. We show that this inhibition is independent of the type III and type VI secretion systems expressed by STm and is also independent of bacterial phagocytosis. The inhibition is Toll-like receptor 4 (TLR4)-dependent as the TLR4 ligand, lipopolysaccharide (LPS), alone is sufficient to inhibit IFNβ-mediated signaling and STm-infected, TLR4-deficient BMDMs do not exhibit inhibited IFNβ signaling. In summary, we show that macrophages exposed to STm have reduced IFNβ signaling via crosstalk with TLR4 signaling, and that IFNβ signaling does not affect cell autonomous host defense against STm.
Viral infections account for a large proportion of the total number of fatal diseases and require close attention from the international public health community. The COVID-19 pandemic has highlighted problems in medicine and healthcare related to the search for effective substances for the prevention, diagnosis and treatment of viral infections. According to many scientific studies, cerium species are very promising biomedical materials for combatting viral infections and have shown encouraging results in killing viruses on non-living objects, reducing viral load both in vitro and in vivo, relieving symptoms and reducing the consequences of viral diseases. This review critically examines the current level of knowledge on cerium species and their practical applications, with a focus on CeO2 nanoparticles (CeNPs). This review also seeks to assess the prospects for their development and use in antiviral theranostics.
Teleost fish type I IFNs and the associated receptors from the cytokine receptor family B (CRFB) are characterized by remarkable diversity and complexity. How the fish type I IFNs bind to their receptors is still not fully understood. In this study, we demonstrate that CRFB1 and CRFB5 constitute the receptor pair through which type I subgroup d IFN (IFNd) from large yellow croaker, Larimichthys crocea, activates the conserved JAK-STAT signaling pathway as a part of the antiviral response. Our data suggest that L. crocea IFNd (LcIFNd) has a higher binding affinity with L. crocea CRFB5 (LcCRFB5) than with LcCRFB1. Furthermore, we report the crystal structure of LcIFNd at a 1.49-Å resolution and construct structural models of LcIFNd in binary complexes with predicted structures of extracellular regions of LcCRFB1 and LcCRFB5, respectively. Despite striking similarities in overall architectures of LcIFNd and its ortholog human IFN-ω, the receptor binding patterns between LcIFNd and its receptors show that teleost and mammalian type I IFNs may have differentially selected helices that bind to their homologous receptors. Correspondingly, key residues mediating binding of LcIFNd to LcCRFB1 and LcCRFB5 are largely distinct from the receptor-interacting residues in other fish and mammalian type I IFNs. Our findings reveal a ligand/receptor complex binding mechanism of IFNd in teleost fish, thus providing new insights into the function and evolution of type I IFNs.
Oncolytic virus (OV) therapy has been shown to be an effective targeted cancer therapy treatment in recent years, providing an avenue of treatment that poses no damage to surrounding healthy tissues. Not only do OVs cause direct oncolysis, but they also amplify both innate and adaptive immune responses generating long-term anti-tumour immunity. Genetically engineered OVs have become the common promising strategy to enhance anti-tumour immunity, safety, and efficacy as well as targeted delivery. The studies of various OVs have been accomplished through phase I-III clinical trial studies. In addition, the uses of carrier platforms of organic materials such as polymer chains, liposomes, hydrogels, and cell carriers have played a vital role in the potentially targeted delivery of OVs. The mechanism, rational design, recent clinical trials, applications, and the development of targeted delivery platforms of OVs will be discussed in this review.
Type I interferon (IFN-I)-induced signaling plays a critical role in host antiviral innate immune responses. Despite this, the mechanisms that regulate this signaling pathway have yet to be fully elucidated. The nucleoporin Ran Binding Protein 2 (RanBP2) (also known as Nucleoporin 358 KDa, Nup358) has been implicated in a number of cellular processes, including host innate immune signaling pathways, and is known to influence viral infection. In this study, we documented that RanBP2 mediates the sumoylation of signal transducers and activators of transcription 1 (STAT1) and inhibits IFN-α-induced signaling. Specifically, we found that RanBP2-mediated sumoylation inhibits the interaction of STAT1 and Janus kinase 1 (JAK1), as well as the phosphorylation and nuclear accumulation of STAT1 after IFN-α stimulation, thereby antagonizing the IFN-α-mediated antiviral innate immune signaling pathway and promoting viral infection. Our findings not only provide insights into a novel function of RanBP2 in antiviral innate immunity but may also contribute to the development of new antiviral therapeutic strategies.
Tilapia are a group of fish belonging to the family Cichlidae. Because of their mild flavor and tasty flesh, tilapia has become the second most important aquaculture species after carp. Two highly cultured species of tilapia are Oreochromis mossambicus and Oreochromis niloticus. Tilapia aquaculture is expanding enormously and up to 6.6 million tons of tilapia is expected by 2030 annually. With the intensification of tilapia culture and the environmental manipulation of culture systems, there is an increase in infectious diseases and economic losses due to disease and stress. A lot of consideration has to be given to health management and the proper use of prophylactics. Various methods are used for disease prevention and control in tilapia aquaculture. Chemotherapeutic agents like antibiotics, biotherapeutic agents like probiotics, prebiotics symbiotics, and medicinal plants are often used. The use of medicinal plants is gaining much attention as they are eco-friendly, sustainable, and have the least environmental impact. Medicinal plants improve growth, appetite, and disease resistance and also boost the immune system of aquatic organisms. Powder of different parts of medicinal plants and extracts are used while routes of administration include oral, immersion, and in form of injections. Oral administration as feed additives is the most commonly used method. This chapter will focus on the use of different medicinal plants in tilapia aquaculture, their routes of administration, and their effects on fish physiology. Moreover, various modes of action of these medicinal plants are also discussed.
Herpes simplex virus encephalitis (HSE) is the leading cause of non-epidemic encephalitis in the developed world and, despite antiviral therapy, mortality and morbidity is high. The emergence of post-HSE autoimmune encephalitis (AE) reveals a new immunological paradigm in autoantibody-mediated disease. A reductionist evaluation of the immunobiological mechanisms in HSE is crucial to dissect the origins of post-viral autoimmunity and supply rational approaches to the selection of immunotherapeutics.
Herein, we review the latest evidence behind the phenotypic progression and underlying immunobiology of HSE including the cytokine/chemokine environment, the role of pathogen-recognition receptors, T- and B-cell immunity and relevant inborn errors of immunity. Secondly, we provide a contemporary review of published patients with post-HSE AE from a combined cohort of 110 patients. Thirdly, we integrate novel mechanisms of autoimmunisation in deep cervical lymph nodes to explore hypotheses around post-HSE AE and challenge these against mechanisms of molecular mimicry and others. Finally, we explore translational concepts where neuroglial surface autoantibodies have been observed with other neuroinfectious diseases and those that generate brain damage including traumatic brain injury, ischaemic stroke and neurodegenerative disease.
Overall, the clinical and immunological landscape of HSE is an important and evolving field, from which precision immunotherapeutics could soon emerge.
TNF-α and IFN-γ are two inflammatory cytokines that play critical roles in immune responses, but they can also negatively affect cell proliferation and viability. In particular, the combination of the two cytokines (TNF-α/IFN-γ) synergistically causes cytotoxicity in many cell types. We recently reported that mouse embryonic stem cells (ESCs) isolated from the blastocyst stage embryo do not respond to TNF-α and have limited response to IFN-γ, thereby avoiding TNF-α/IFN-γ cytotoxicity. The current study expanded our investigation to mouse trophoblast stem cells (TSCs) and their differentiated trophoblasts (TSC-TBs), the precursors and the differentiated cells of the placenta, respectively. In this study, we report that the combination of TNF-α/IFN-γ does not show the cytotoxicity to TSCs and TSC-TBs that otherwise effectively kills fibroblasts, similar to ESCs. Although ESCs, TSCs, and TSC-TBs are dramatically different in their growth rate, morphology, and physiological functions, they nevertheless share a similarity in being able to avoid TNF-α/IFN-γ cytotoxicity. We propose that this unique immune property may serve as a protective mechanism that limits cytokine cytotoxicity in the blastocyst. With molecular and cellular approaches and genome-wide transcriptomic analysis, we have demonstrated that the attenuated NF-κB and STAT1 transcription activation is a limiting factor that restricts the effect of TNF-α/IFN-γ on TSCs and TSC-TBs.
Interleukin-1 beta converting enzyme (ICE) is a mammalian homolog of CED-3, a protein required for programmed cell death in
the nematode Caenorhabditis elegans. The activity of ICE can be specifically inhibited by the product of crmA, a cytokine
response modifier gene encoded by cowpox virus. Microinjection of the crmA gene into chicken dorsal root ganglion neurons
was found to prevent cell death induced by deprivation of nerve growth factor. Thus, ICE is likely to participate in neuronal
death in vertebrates.
We report preliminary characterization of a gene designated β-R1, which is selectively expressed in response to interferon
β (IFN-β) compared with IFN-α. In human astrocytoma cells, β-R1 was induced to an equivalent extent by 10 IU/mL IFN-β or 2500
IU/mL IFN-α2. To address the mechanism of this differential response, we analyzed induction of the β-R1 gene in fibrosarcoma
cells and derivative mutant cells lacking components required for signaling by type I IFNs. β-R1 was readily induced by IFN-β
in the parental 2fTGH cell line, but not by recombinant IFN-α2, IFN-α Con1, or a mixture of IFN-α subtypes. IFN-α8 induced
β-R1 weakly. β-R1 was not induced by IFN-β in mutant cell lines U2A, U3A, U4A, and U6A, which lack, respectively, p48, STAT1,
JAK1, and STAT2. U5A cells, which lack the Ifnar 2.2 component of the IFN-α and -β receptor, also failed to express β-R1.
U1A cells are partially responsive to IFN-β and IFN-α8 but lacked β-R1 expression, indicating that TYK2 protein is essential
for induction of this gene. Taken together, these results suggest that the expression of β-R1 in response to type I IFN requires
IFN-stimulated gene factor 3 plus an additional component, which is more efficiently formed on induction by IFN-β compared
with IFN-α.
The 2–5A system is an interferon-regulated RNA degradation pathway with antiviral, growth-inhibitory, and pro-apoptotic activities.
RNase-L mediates the antiviral activity through the degradation of viral RNAs, and the anticellular effects of the 2–5A system
are thought to be similarly mediated through the degradation of cellular transcripts. However, specific RNase-L-regulated
cellular RNAs have not been identified. To isolate candidate RNase-L substrates, differential display was used to identify
mRNAs that exhibited increased expression in RNase-L-deficient N1E-115 cells as compared with RNase-L-transfected cells. A
novel interferon-stimulated gene encoding a 43-kDa ubiquitin-specific protease, designated ISG43, was identified in this screen.
ISG43 expression is induced by interferon and negatively regulated by RNase-L. ISG43 induction is a primary response to interferon
treatment and requires a functional JAK/STAT signaling pathway. The kinetics of ISG43 induction were identical in wild type
and RNase-L knock-out fibroblasts; however, the decline in ISG43 mRNA following interferon treatment was markedly attenuated
in RNase-L knock-out fibroblasts. The delayed shut-off kinetics of ISG43 mRNA corresponded to an increase in its half-life
in RNase-L-deficient cells. ISG15 mRNA also displayed RNase-L-dependent regulation. These findings identify a novel role for
the 2–5A system in the attenuation of the interferon response.
Major histocompatibility complex (MHC) class I antigens are constitutively expressed yet highly induced by interferon (IFN) during inflammation. We found that not only IFN-induced but also normal basal expression of MHC I required IFN receptors and signal transducer and activator of transcription (STAT)1, providing genetic evidence for continuous IFN signaling. Surprisingly, an IFN-independent requirement for STAT1 was also found, specifically in T lymphocytes, where MHC class I expression was not fully accounted for by IFN signaling. This IFN-independent pathway maintained tyrosine phosphorylation of STAT1 in T but not B lymphocytes even in the absence of IFN receptors. Interestingly, interleukin (IL)-7 selectively activated STAT1 and induced MHC class I in mature T but not B cells. These loss of function studies demonstrate an essential role of endogenous IFN and activated STAT1 for constitutive MHC class I expression in normal mice and define IL-7–dependent but IFN-independent regulation of STAT1 restricted to T lymphocytes.
p58(IPK), a member of the tetratricopeptide repeat and J-domain protein families, was first recognized for its ability to inhibit the double-stranded RNA-activated protein kinase, PKR. PKR is part of the interferon-induced host defense against viral infection, and down-regulates translation initiation via phosphorylation of eukaryotic initiation factor 2 on the alpha-subunit. P58(IPK) is activated in response to infection by influenza virus, and inhibits PKR through direct protein-protein interaction. Previously, we demonstrated that the molecular chaperone heat shock protein 40 (hsp40) was a negative regulator of p58(IPK). We could now report that influenza virus activates the p58(IPK) pathway by promoting the dissociation of hsp40 from p58(IPK) during infection. We also found that the P58(IPK)-hsp40 association was disrupted during recovery from heat shock, which suggested a regulatory role for P58(IPK) in the absence of virus infection. The PKR pathway is even more complex as we show in this report that the molecular chaperone, hsp/Hsc70, was a component of a trimeric complex with hsp40 and p58(IPK). Moreover, like other J-domain proteins, p58(IPK) stimulated the ATPase activity of Hsc70, Taken together, our data suggest that p58(IPK) is a co-chaperone, possibly directing hsp/Hsc70 to refold, and thus inhibit kinase function.
The genes of the family of interferon (IFN) regulatory factors (IRF) encode DNA binding transcriptional factors that are involved
in modulation of transcription of IFN and interferon-induced genes (ISG). The presence of IRF binding sites in the promoter
region of IFNA and IFNB genes indicates that IRF factors recognizing these sites play an important role in the virus-mediated induction of these
genes. We have described a novel human gene of this family, IRF-3, that is constitutively expressed in a variety of cell types.
IRF-3 binds to the interferon-sensitive response element (ISRE) present in the ISG15 gene promoter and activates its transcriptional
activity. In the present study, we examined whether IRF-3 can modulate transcriptional activity of IFNA and IFNB promoter
regions. Our results demonstrate that IRF-3 can bind to the IRF-like binding sites present in the virus-inducible region of
the IFNA4 promoter and to the PRDIII region of the IFNB promoter but cannot alone stimulate their transcriptional activity
in the human cell line, 293. However, the fusion protein generated from the IRF-3 binding domain and the RelA(p65) activation
domain effectively activates both IFNA4 and IFNB promoters. Cotransfection of IRF-3 and RelA(p65) expression plasmids activates
the IFNBgene promoter but not the promoter of IFNA4 gene that does not contain the NF-kB binding site. Surprisingly, activation of the IFNA4 gene promoter by virus and IRF-1
in these cells was inhibited by IRF-3. These data indicate that in 293 cells IRF-3 does not stimulate expression of IFN genes
but can cooperate with RelA(p65) to stimulate the IFNB promoter.
Type I interferons constitute an important part of the innate immune response against viral infection. Unlike the expression of interferon (IFN) B gene, the expression of IFNA genes is restricted to the lymphoid cells. Both IFN regulatory factor 3 and 7 (IRF-3 and IRF-7) were suggested to play positive roles in these genes expression. However, their role in the differential expression of individual subtypes of human IFNA genes is unknown. Using various IFNA reporter constructs in transient transfection assay we found that overexpression of IRF-3 in virus infected 2FTGH cells selectively activated IFNA1 VRE, whereas IRF-7 was able to activate IFNA1, A2, and A4. The binding of recombinant IRF-7 and IRF-3 to these VREs correlated with their transcriptional activation. Nuclear proteins from infected and uninfected IRF-7 expressing 2FTGH cells formed multiple DNA-protein complexes with IFNA1 VRE, in which two unique DNA-protein complexes containing IRF-7 were detected. In 2FTGH cells, virus stimulated expression of IFNB gene but none of the IFNA genes. Reconstitution of IRF-7 synthesis in these cells resulted, upon virus infection, in the activation of seven endogenous IFNA genes in which IFNA1 predominated. These studies suggest that IRF-7 is a critical determinant for the induction of IFNA genes in infected cells.
The interferon (IFN)-induced double-stranded RNA (dsRNA)-activated Ser/Thr protein kinase (PKR) plays a role in the antiviral and antiproliferative effects of IFN. PKR phosphorylates initiation factor eIF2, thereby inhibiting protein synthesis, and also activates the transcription factor, nuclear factor-B (NF-B), by phosphorylating the inhibitor of NF-B, IB. Mice devoid of functional PKR (Pkr°/°) derived by targeted gene disruption exhibit a diminished response to IFN- and poly(rI:rC) (pIC). In embryo fibroblasts derived from Pkr°/° mice, interferon regulatory factor 1 (IRF-1) or guanylate binding protein (Gbp) promoter–reporter constructs were unresponsive to IFN- or pIC but response could be restored by co-transfection with PKR. The lack of responsiveness could be attributed to a diminished activation of IRF-1 and/or NF-B in response to IFN- or pIC. Thus, PKR acts as a signal transducer for IFN-stimulated genes dependent on the transcription factors IRF-1 and NF-B.
The murine influenza virus resistance locus Mx consists of more than one interferon-responsive transcription unit. We isolated clones of the transcripts of a second Mx gene (Mx2) which is closely linked to the well-characterized resistance gene and determined their sequences. Mx2 mRNA is more than 90% identical to Mx1 mRNA in the region corresponding to the amino termini of the encoded proteins. Mx2 mRNAs of mouse strains BALB/c and CBA have open reading frames apparently interrupted by mutations. Interferon-treated cells from strain A2G and other influenza virus-resistant strains failed to express detectable amounts of Mx2 transcripts.
The interferon (IFN)-activated human 2',5'-oligo(A) synthetase E gene contains 11 RNA starts and lacks TATA and CAAT signals. DNA sequences around the promoter make the expression of the chloramphenicol acetyltransferase gene (CAT) inducible over 20-fold by IFN. A 72-base-pair segment (E-IRS) immediately upstream of the RNA starts was defined as being required for IFN-activated expression of the E-gene promoter-CAT constructs and acts in a position-independent manner. It also confers IFN-activated enhancement to the herpes simplex virus thymidine kinase promoter. On this promoter, the 5' part of the E-IRS functions as a constitutive enhancer, while the last 16 base pairs of the E-IRS is sufficient to give IFN-induced expression. On the E-gene promoter, the constitutive enhancer and the IFN-activated sequence are both needed but can be separated. In addition, promoter competition experiments indicate a third regulatory region which helps to repress expression of the E gene in uninduced cells.
The interferon-induced protein kinase DAI, the double-stranded RNA (dsRNA)-activated inhibitor of translation, plays a key role in regulating protein synthesis in higher cells. Once activated, in a process that involves autophosphorylation, it phosphorylates the initiation factor eIF-2, leading to inhibition of polypeptide chain initiation. The activity of DAI is controlled by RNA regulators, including dsRNA activators and highly structured single-stranded RNAs which block activation by dsRNA. To elucidate the mechanism of activation, we studied the interaction of DAI with RNA duplexes of discrete sizes. Molecules shorter than 30 bp fail to bind stably and do not activate the enzyme, but at high concentrations they prevent activation by long dsRNA. Molecules longer than 30 bp bind and activate the enzyme, with an efficiency that increases with increasing chain length, reaching a maximum at about 85 bp. These dsRNAs fail to activate at high concentrations and also prevent activation by long dsRNA. Analysis of complexes between dsRNA and DAI suggests that at maximal packing the enzyme interacts with as little as a single helical turn of dsRNA (11 bp) but under conditions that allow activation the binding site protects about 80 bp of duplex. When the RNA-binding site is fully occupied with an RNA activator, the complex appears to undergo a conformational change.
Eukaryotic viruses have devised numerous strategies to downregulate activity of the interferon-induced, double-stranded (dsRNA)-activated protein kinase (referred to as p68 on the basis of its Mr of 68,000 in human cells). Viruses must exert this control to avoid extensive phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2) by p68 and the resultant negative effects on protein synthesis initiation. To begin to define the molecular mechanisms underlying this regulation, we optimized expression of p68 in an in vitro transcription-translation system utilizing the full-length cDNA clone. The in vitro-expressed kinase was autophosphorylated in response to dsRNAs and heparin in a manner similar to that for the native p68 provided that the kinase inhibitor, 2-aminopurine, was present during the in vitro translation reaction. Further, the activated kinase efficiently phosphorylated its natural substrate, the alpha subunit of eIF-2. Binding experiments revealed that the expressed kinase complexed with the dsRNA activator, reovirus dsRNA, as well as the adenovirus-encoded inhibitor, VAI RNA. Interestingly, both the reovirus RNAs and VAI RNA also complexed with protein kinase molecules that lacked the carboxyl terminus and all catalytic domains. Deletion analysis confirmed that the p68 amino terminus contained critical determinants for reovirus dsRNA and VAI RNA binding. Further, reovirus dsRNA efficiently bound to, but failed to activate, p68 kinase molecules containing a single amino acid substitution in the invariant lysine 295 present in catalytic domain II. Taken together, these data demonstrate that this expression system permits a detailed mutagenic analysis of the regions of p68 required for interaction with virus-encoded activators and repressors.
Human cells treated with interferon synthesize two proteins that exhibit high homology to murine Mx1 protein, which has previously been identified as the mediator of interferon-induced cellular resistance of mouse cells against influenza viruses. Using murine Mx1 cDNA as a hybridization probe, we have isolated cDNA clones originating from two distinct human Mx genes, designated MxA and MxB. In human fibroblasts, expression of MxA and MxB is strongly induced by alpha interferon (IFN-alpha), IFN-beta, Newcastle disease virus, and, to a much lesser extent, IFN-gamma, MxA and MxB proteins have molecular masses of 76 and 73 kilodaltons, respectively, and their sequences are 63% identical. A comparison of human and mouse Mx proteins revealed that human MxA and mouse Mx2 are the most closely related proteins, showing 77% sequence identity. Near their amino termini, human and mouse Mx proteins contain a block of 53 identical amino acids and additional regions of very high sequence similarity. These conserved sequences are also present in a double-stranded RNA-inducible fish gene, which suggests that they may constitute a functionally important domain of Mx proteins. In contrast to mouse Mx1 protein, which accumulates in the nuclei of IFN-treated mouse cells, the two human Mx proteins both accumulate in the cytoplasm of IFN-treated cells.
Previously we described human cell line 2fTGH, in which expression of guanine phosphoribosyltransferase is tightly controlled by the upstream region of interferon (IFN)-stimulated human gene 6-16. After mutagenesis of 2fTGH and selection with 6-thioguanine and IFN-alpha, we isolated 11.1, a recessive mutant that does not respond to IFN-alpha. We now describe U2, a second recessive mutant, selected similarly, that complements 11.1. U2 had no response to IFN-alpha or IFN-beta, and its response to IFN-gamma was partially defective. Although many genes did respond to IFN-gamma in U2, the 9-27 gene did not and the antiviral response of U2 cells to IFN-gamma was greatly reduced. Band shift assays showed that none of the transcription factors normally induced in 2fTGH cells by IFN-alpha (E and M) or IFN-gamma (G) were induced in U2. However, extracts of untreated U2 cells gave rise to a novel band that was increased by treatment with IFN-gamma but not IFN-alpha. Band shift complementation assays revealed that untreated and IFN-gamma-treated U2 cells lack the functional E gamma subunit of transcription factor E and that IFN-alpha-treated U2 cells do contain the functional E alpha subunit.
The phosphorylation of the alpha-subunit of initiation factor eIF-2 leads to an inhibition of protein synthesis in mammalian cells. We have performed site-directed mutagenesis on a cDNA encoding the alpha-subunit of human eIF-2 and have replaced the candidate sites of phosphorylation, Ser-48 and Ser-51, with alanines. The cDNAs were expressed in vitro by SP6 polymerase transcription and rabbit reticulocyte lysate translation, and the radiolabeled protein products were analyzed by high-resolution two-dimensional gel electrophoresis. The wild-type and Ser-48 mutant proteins became extensively phosphorylated by eIF-2 kinases present in the reticulocyte lysate, and when additional heme-controlled repressor or double-stranded RNA-activated kinase was present, phosphorylation of the proteins was enhanced. The Ser-51 mutant showed little covalent modification by the endogenous enzymes and showed no increase in the acidic variant with additional eIF-2 kinases, thereby suggesting that Ser-51 is the site of phosphorylation leading to repression of protein synthesis.
The double-stranded RNA (dsRNA)-dependent protein kinase DAI (also termed dsI and P1) possesses two kinase activities; one is an autophosphorylation activity, and the other phosphorylates initiation factor eIF-2. We purified the enzyme, in a latent form, to near homogeneity from interferon-treated human 293 cells. The purified enzyme consisted of a single polypeptide subunit of approximately 70,000 daltons, retained its dependence on dsRNA for activation, and was sensitive to inhibition by adenovirus VA RNAI. Autophosphorylation required a suitable concentration of dsRNA and was second order with respect to DAI concentration, which suggests an intermolecular mechanism in which one DAI molecule phosphorylates a neighboring molecule. Once autophosphorylated, the enzyme could phosphorylate eIF-2 but seemed unable to phosphorylate other DAI molecules, which implies a change in substrate specificity upon activation. VA RNAI blocked autophosphorylation and activation but permitted the activated enzyme to phosphorylate eIF-2. VA RNAI also blocked the binding of dsRNA to the enzyme. The data are consistent with a model in which activation requires the interaction of two molecules of DAI with dsRNA, followed by intermolecular autophosphorylation of the latent enzyme. VA RNAI would block activation by preventing the interaction between DAI and dsRNA.
The human MxA protein is part of the antiviral state induced by alpha/beta interferon (IFN-α/β). MxA inhibits the multiplication of several RNA viruses in cell culture. However, its antiviral potential in vivo has not yet been fully explored. We have generated MxA-transgenic mice that lack a functional IFN system by crossing MxA-transgenic mice constitutively expressing MxA with genetically targeted (knockout) mice lacking the β subunit of the IFN-α/β receptor (IFNAR-1 −/− mice). These mice are an ideal animal model to investigate the unique antiviral activity of human MxA in vivo, because they are unable to express other IFN-induced proteins. Here, we show that MxA confers resistance to Thogoto virus, La Crosse virus, and Semliki Forest virus. No Thogoto virus progeny was detectable in MxA-transgenic mice, indicating an efficient block of virus replication at the primary site of infection. In the case of La Crosse virus, MxA restricted invasion of the central nervous system. In contrast, Semliki Forest virus multiplication in the brain was detectable in both MxA-expressing and nonexpressing IFNAR-1 −/− mice. However, viral titers were clearly reduced in MxA-transgenic mice. Our results demonstrate that MxA does not need the help of other IFN-induced proteins for activity but is a powerful antiviral agent on its own. Moreover, the results suggest that MxA may protect humans from potential fatal infections by La Crosse virus and other viral pathogens.
In an effort to characterize molecular events contributing to lineage commitment and terminal differentiation of stem/progenitor cells, we have used differential display reverse transcription polymerase chain reaction (DDRT-PCR) and cell lines blocked at two distinct stages of differentiation. The cell lines used were EML, which is representative of normal multipotential primitive progenitors (Sca-1+, CD34+, c-Kit+, Thy-1+) able to differentiate into erythroid, myeloid, and B-lymphoid cells in vitro, and MPRO, which is a more committed progenitor cell line, with characteristics of promyelocytes able to differentiate into granulocytes. One clone isolated by this approach was expressed in MPRO but not in EML cells and contained sequence identical to the 3′ untranslated region of D3, a gene cloned from activated peritoneal macrophages of unknown function. We have observed a novel pattern of D3 gene expression and found that D3 is induced in EML cells under conditions that promote myeloid cell differentiation (interleukin-3 [IL-3], stem cell factor [SCF], and all-trans-retinoic acid [atRA]) starting at 2 days, corresponding to the appearance of promyelocytes. D3 RNA expression reached a maximum after 5 days, corresponding to the appearance of neutrophilic granulocytes and macrophages, and decreased by day 6 with increased numbers of differentiated neutrophils and macrophages in vitro. Induction of D3 RNA in EML was dependent on IL-3 and was not induced in response to SCF or atRA alone or SCF in combination with 15 other hematopoietic growth factors (HGF) tested. Similarly, D3 was not expressed in the normal bone marrow cell (BMC) counterpart of EML cells, Linlo c-Kit+Sca-1+ progenitor cells. D3 RNA expression was induced in these cells when cultured for 7 days in IL-3 plus SCF. A comparison of the expression of D3 RNA in cell lines and normal BMC populations demonstrated that D3 is induced during macrophage and granulocyte differentiation and suggests a potential physiological role for D3 in normal myeloid differentiation.
The 2-5A/RNase L system is considered as a central pathway of interferon (IFN) action and could possibly play a more general physiological role as for instance in the regulation of RNA stability in mammalian cells. We describe here the expression cloning and initial characterization of RLI (for RNase L inhibitor), a new type of endoribonuclease inhibitor. RLI cDNA codes for a 68-kDa polypeptide whose expression is not regulated by IFN. Its expression in reticulocyte extracts antagonizes the 2-5A binding ability and the nuclease activity of endogenous RNase L or the cloned 2DR polypeptide. The inhibition requires the association of RLI with the nuclease and is dependent on the ratio between the two proteins. Likewise RLI is coimmunoprecipitated with the RNase L complex by a nuclease-specific antibody. RLI does not lead to 2-5A degradation or to irreversible modification of RNase L. The overexpression of RLI in stably transfected HeLa cells inhibits the antiviral activity of IFN on encephalomyocarditis virus but not on vesicular stomatitis virus. RLI therefore appears as the first described and potentially important mediator of the 2-5A/RNase L pathway.
2‐5A‐dependent RNase is the terminal factor in the interferon‐regulated 2‐5A system thought to function in both the molecular mechanism of interferon action and in the general control of RNA stability. However, direct evidence for specific functions of 2‐5A‐dependent RNase has been generally lacking. Therefore, we developed a strategy to block the 2‐5A system using a truncated form of 2‐5A‐dependent RNase which retains 2‐5A binding activity while lacking RNase activity. When the truncated RNase was stably expressed to high levels in murine cells, it prevented specific rRNA cleavage in response to 2‐5A transfection and the cells were unresponsive to the antiviral activity of interferon alpha/beta for encephalomyocarditis virus. Remarkably, cells expressing the truncated RNase were also resistant to the antiproliferative activity of interferon. The truncated RNase is a dominant negative mutant that binds 2‐5A and that may interfere with normal protein‐protein interactions through nine ankyrin‐like repeats.
Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens. Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally. However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses. Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response. These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.
To successfully produce disease, a virus must enter its host, replicate within host cells, spread within the host and, in the case of systemic infection, overcome host immune defenses, and damage host tissues. At each stage of the infectious process, a number of viral and host factors determine the ultimate pathogenicity (capacity to produce disease) of the virus. Recent studies using the mammalian reoviruses as a model system have provided insights into the roles of viral and host components in the production of disease. The mammalian reoviruses offer an excellent system for the study of molecular aspects of viral pathogenesis because reovirus genetics has provided a means to identify specific viral components involved in the disease process.
Class II transactivator (CIITA) is a master regulator required for both constitutive and IFN-γ-inducible expression of class II MHC genes. Although the central role of CIITA is greatly appreciated, mechanisms underlying regulation of expression of CIITA are not well understood. This report describes a large (7 kb) fragment of 5′ flanking sequences which mediates the B cell-specific. IFN-γ-induced and TGF-β-suppressed expression of CIITA. Within the 7 kb fragment, sequences which lie between nucleotides -545 and -113 relative to the transcriptional start site are critical for constitutive promoter expression in B cells. In contrast, activation of CIITA by IFN-γin U373-MG glioblastoma cells and 2fTGH fibroblasts requires sequences contained in an additional 4 kb of upstream DNA. This region mediates an IFN-γ response when linked to either the endogenous CIITA promoter or a heterologous promoter. A role for STAT1 in regulation of the CIITA promoter is shown by the rescue of IFN-γ induction by expression of STAT1 in STAT1-defective U3A cells. TGF-3 significantly inhibits IFN-γ-mediated induction of the CIITA promoter in 2fTGH cells. which indicates that the promoter is a target for TGF-β. This inhibition is achieved by suppression at the level of the basal promoter. Understanding the mechanisms of CIITA gene regulation has broad implications in transplantation and in the control of autoimmune diseases.
Mouse macrophages can be stimulated by interferon (IFN)-gamma and bacterial lipopolysaccharide (LPS) to pro duce nitric oxide (NO) as the result of expression of the inducible NO synthase (iNOS; EC 1.14.13.39) gene. The iNOS gene promoter contains a candidate gamma-interferon-activated site (GAS). In transfection studies reported here, it was demonstrated that a luciferase reporter-gene construct, containing four synthetic copies of the iNOS GAS, was inducible when transfected macrophages were stimulated with either IFN-gamma, LPS, or a combination of the two. Consistent with this finding were other transfection analyses, which showed that responsiveness of the intact iNOS promoter to these same agents was significantly reduced when two conserved nucleotide positions within the GAS were mutated. Oligonucleotide probes, which mimicked the iNOS GAS, formed a complex with proteins that appeared in the nuclei of IFN-gamma or IFN-gamma + LPS treated macrophages within 30 min of stimulation, as shown by electrophoretic mobility shift assay. LPS alone also caused the the appearance of a nuclear protein capable of binding the iNOS GAS-containing oligonucleotide; however, in contrast to binding induced by IFN-gamma, approximately 2 h of stimulation with LPS were required. The protein bound to the iNOS GAS containing oligonucleotide reacted specifically with an antibody raised against Stat1 alpha, regardless of the stimulus used. These data collectively support the conclusion that binding of Stat1 alpha to the iNOS promoter's GAS is required for optimal induction of the iNOS gene by IFN-gamma and LPS.
Hepatitis C virus (HCV) infection is a global health problem affecting an estimated 170 million individuals worldwide. We report the identification of multiple independent adaptive mutations that cluster in the HCV nonstructural protein NS5A and confer increased replicative ability in vitro. Among these adaptive mutations were a single amino acid substitution that allowed HCV RNA replication in 10% of transfected hepatoma cells and a deletion of 47 amino acids encompassing the interferon (IFN) sensitivity determining region (ISDR). Independent of the ISDR, IFN-α rapidly inhibited HCV RNA replication in vitro. This work establishes a robust, cell-based system for genetic and functional analyses of HCV replication.
The class II transactivator (CIITA) has been shown to be required for major histocompatibility complex (MHC) class II gene expression in B cells and its deficiency is responsible for a hereditary MHC class II deficiency. Here we show that CIITA is also involved in the inducible expression of class II genes upon interferon gamma (IFN-gamma) treatment. The expression of CIITA is also inducible with IFN-gamma before the induction of MHC class II mRNA. In addition, CIITA mRNA expression does not require new protein synthesis, although new protein synthesis is necessary for the transcription of class II. This suggests that synthesis of new CIITA protein may be essential to induce class II gene expression. We also showed that the JAK1 protein tyrosine kinase activity is required to induce the expression of CIITA upon IFN-gamma stimulation. This finding indicates that CIITA is part of the signaling cascade from the IFN-gamma receptor to the activation of class II genes. In addition, the expression of CIITA is sufficient to activate class II genes in the absence of IFN-gamma stimulation suggesting that CIITA is the major regulatory factor for the inducible expression of class II genes. Together, these data suggest that CIITA is the IFN-inducible cycloheximide sensitive factor previously shown to be required for the induction of MHC class II gene expression.
During a study of the interference produced by heat-inactivated influenza virus with the growth of live virus in fragments of chick chorio-allantoic membrane it was found that following incubation of heated virus with membrane a new factor was released. This factor, recognized by its ability to induce interference in fresh pieces of chorio-allantoic membrane, was called interferon, Following a lag phase interferon was first detected in the membranes after 3 h incubation and thereafter it was released into the surrounding fluid.
Major histocompatibility complex (MHC) class I molecules bind peptides derived from cellular proteins and display them for surveillance by the immune system. These peptide-binding molecules are composed of a heavy chain, containing an antigen-binding groove, which is tightly associated with a light chain (beta 2-microglobulin). The majority of presented peptides are generated by degradation of proteins in the cytoplasm, in many cases by a large multicatalytic proteolytic particle, the proteasome. Two beta-subunits of the proteasome, LMP2 and LMP7, are inducible by interferon-gamma and alter the catalytic activities of this particle, enhancing the presentation of at least some antigens. After production of the peptide in the cytosol, it is transported across the endoplasmic reticulum (ER) membrane in an ATP-dependent manner by TAP (transporter associated with antigen presentation), a member of the ATP-binding cassette family of transport proteins. There are minor pathways for generating presented peptides directly in the ER, and some evidence suggests that peptides may be further trimmed in this location. The class I heavy chain and beta 2-microglobulin are cotranslationally translocated into the endoplasmic reticulum where their assembly may be facilitated by the sequential association of the heavy chain with chaperone proteins BiP and calnexin. The class I molecule then associates with the lumenal face of TAP where it is retained, presumably awaiting a peptide. After the class I molecule binds a peptide, it is released for exocytosis to the cell surface where cytotoxic T lymphocytes examine it for peptides derived from foreign proteins.
Vaccinia virus (VV) has been shown to be relatively resistant to the antiviral effects of interferon-alpha (IFN-alpha) and to rescue replication of IFN-sensitive viruses, such as encephalomyocarditis virus (EMCV) and vesicular stomatitis virus (VSV), from the antiviral effects of IFN. The E3L and K3L gene products have been implicated in the IFN resistance of VV. We have investigated the role that these VV-encoded functions play in the rescue of VSV and EMCV from the effects of IFN, Transient expression of the E3L open reading frame (ORF) was sufficient to rescue VSV but not EMCV from the IFN-induced antiviral state. Rescue of VSV by mutants of E3L correlated with the ability of the mutated E3L gene products to bind dsRNA, Conversely, transient expression of the K3L ORF was sufficient to partially rescue EMCV but not VSV from the effects of IFN, Results with VV deleted of either the K3L or E3L ORFs were consistent with results obtained by transient expression of these genes. These results demonstrate that the VV E3L gene products are likely responsible for the VV-mediated rescue of VSV from the effects of IFN and the K3L gene product is likely at least partly responsible for rescue of EMCV.
Interferon-gamma (IFN-gamma), also known as type II interferon, is an important immunoregulatory gene that has multiple effects on the development, maturation, and function of the immune system, IFN-gamma mRNA and protein are expressed predominantly by T cells and large granular lymphocytes. The IFN-gamma mRNA is induced/inhibited in these cell types by a wide variety of extracellular signals, thus implicating a number of diverse, yet convergent signal transduction pathways in its transcriptional control, In this review, I describe how DNA methylation and specific DNA binding proteins may regulate transcription of the IFN-gamma gene in response to extracellular signals.
The p69/71 2-5A synthetase is an interferon-inducible enzyme that polymerizes ATP to form 2'-5'-linked oligoadenylates when activated by double-stranded RNA, A genomic clone was isolated that contained 12.5 kb of the 5'-flanking region and the first exon of the p69/71 2-5A synthetase gene, The major transcriptional start site was mapped to an A residue located 84 bp upstream of the translational start site within a sequence that matches both a consensus ISRE and an Inr element. Sequencing of the region 972 bp upstream of the translation start site revealed 4 imperfect direct repeats of 70 to 80 bp that contain several putative regulatory elements, This region does not have a TATA or CAAT box but does contain two IRF-1-like elements, an Ets-1 motif, an AP-1 site, an Spl binding site, an NF-kappa B-binding site, and a palindrome containing two overlapping NF-IL-6 consensus motifs in opposite orientation, The region -480 to -850 bp contains PuF, UBP-1, and PEA 3 motifs and another NF-IL-6 motif adjacent to an E2A-binding site, The 5'-flanking sequence binds proteins in DNase I foot printing assays and is a functional interferon-inducible promoter that requires multiple elements for maximal constitutive and interferon-inducible expression.
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Only 15 to 20 percent of patients with chronic hepatitis C have a sustained virologic response to interferon therapy. We compared the efficacy and safety of recombinant interferon alfa-2b alone with those of a combination of interferon alfa-2b and ribavirin for the initial treatment of patients with chronic hepatitis C.
We randomly assigned 912 patients with chronic hepatitis C to receive standard-dose interferon alfa-2b alone or in combination with ribavirin (1000 or 1200 mg orally per day, depending on body weight) for 24 or 48 weeks. Efficacy was assessed by measurements of serum hepatitis C virus (HCV) RNA and serum aminotransferases and by liver biopsy.
The rate of sustained virologic response (defined as an undetectable serum HCV RNA level 24 weeks after treatment was completed) was higher among patients who received combination therapy for either 24 weeks (70 of 228 patients, 31 percent) or 48 weeks (87 of 228 patients, 38 percent) than among patients who received interferon alone for either 24 weeks (13 of 231 patients, 6 percent) or 48 weeks (29 of 225 patients, 13 percent) (P<0.001 for the comparison of interferon alone with both 24 weeks and 48 weeks of combination treatment). Among patients with HCV genotype 1 infection, the best response occurred in those who were treated for 48 weeks with interferon and ribavirin. Histologic improvement was more common in patients who were treated with combination therapy for either 24 weeks (57 percent) or 48 weeks (61 percent) than in those who were treated with interferon alone for either 24 weeks (44 percent) or 48 weeks (41 percent). The drug doses had to be reduced and treatment discontinued more often in patients who were treated with combination therapy.
In patients with chronic hepatitis C, initial therapy with interferon and ribavirin was more effective than treatment with interferon alone.
The protein kinase DAI (the double-stranded RNA activated inhibitor) plays a critical role in controlling translation in uninfected and infected cells. It is induced by interferon as part of the cellular antiviral defense mechanism. When activated, it leads to a blockade of polypeptide chain initiation, thereby interrupting viral propagation. Many viruses have developed means to neutralize the action of DAI: the sheer profusion of these countermeasures makes it clear that DAI is an important component of the host antiviral defense mechanism and a serious concern to the viruses. This chapter focusses on the mechanism of DAI activation and its inhibition by virus-encoded RNA antidotes.