Suppression of Innate Immunity by the Hepatitis C Virus (HCV): Revisiting the Specificity of Host–Virus Interactive Pathways
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PROVIDER: S-EPMC10671098 | biostudies-literature | 2023 Nov
REPOSITORIES: biostudies-literature
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Project description:Activation and viral control of the innate immune response are hallmarks of hepatitis C virus (HCV) infection and are major determinants of spontaneous clearance or progression to chronic infection and liver disease. In this review, we provide a contemporary overview of how HCV is sensed by the host cell to trigger innate immune activation and the mechanisms deployed by the virus to evade this response. Type I and III interferons (IFNs) are crucial mediators of antiviral innate immunity against HCV, and we specifically highlight the importance of IFN-λ host genetics for the outcome of HCV infection. Last, we focus on the proinflammatory responses elicited by HCV infection and describe our current understanding of how interleukin (IL)-1β signaling and cross talk between the IL-1β and IFN signaling pathways lead to sustained inflammation and increased risk of liver pathology.
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Project description:Hepatitis C virus (HCV) is a global public health problem involving chronic infection of the liver, which can cause liver disease and is linked with liver cancer. Viral innate immune evasion strategies and human genetic determinants underlie the transition of acute HCV infection to viral persistence and the support of chronic infection. Host genetic factors, such as sequence polymorphisms in IFNL3, a gene in the host interferon system, can influence both the outcome of the infection and the response to antiviral therapy. Recent insights into how HCV regulates innate immune signaling within the liver reveal a complex interaction of patient genetic background with viral and host factors of innate immune triggering and control that imparts the outcome of HCV infection and immunity.
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Project description:Acute cellular rejection (ACR) and hepatitis C virus (HCV) recurrence (HCVrec) are common complications after liver transplantation (LT) in HCV patients, who share common clinical and histological features, making a differential diagnosis difficult. Fifty-three liver allograft samples from unique HCV LT recipients were studied using microarrays, including a training set (n = 32) and a validation set (n = 19). Two no-HCV-ACR samples from LT recipients were also included. Probe set intensity values were obtained using the robust multiarray average method (RMA) method. Analysis of variance identified statistically differentially expressed genes (P ? 0.005). The limma package was used to fit the mixed-effects models using a restricted maximum likelihood procedure. The last absolute shrinkage and selection operator (LASSO) model was fit with HCVrec versus ACR as the dependent variable predicted. N-fold cross-validation was performed to provide an unbiased estimate of generalization error. A total of 179 probe sets were differentially expressed among groups, with 71 exclusive genes between HCVrec and HCV-ACR. No differences were found within ACR group (HCV-ACR vs. no-HCV-ACR). Supervised clustering analysis displayed two clearly independent groups, and no-HCV-ACR clustered within HCV-ACR. HCVrec-related genes were associated with a cytotoxic T-cell profile, and HCV-ACR-related genes were associated with the inflammatory response. The best-fitting LASSO model classifier accuracy, including 15 genes, has an accuracy of 100% in the training set. N-fold cross-validation accuracy was 78.1%, and sensitivity, specificity and positive and negative predictive values were 50.0%, 90.9%, 71.4% and 80.0%, respectively. Arginase type II (ARG2), ethylmalonic encephalopathy 1 (ETHE1), transmembrane protein 176A (TMEM176A) and TMEM176B genes were significantly confirmed in the validation set. A molecular signature capable of distinguishing HCVrec and ACR in HCV LT recipients was identified and validated.
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Project description:Adenoviruses (Ad) are commonly used as vectors for gene therapy and/or vaccine delivery. Recombinant Ad vectors are being tested as vaccines for many pathogens. We have made a surprising observation that peptides derived from various hepatitis C virus (HCV) antigens contain extensive regions of homology with multiple adenovirus proteins, and conclusively demonstrate that adenovirus vector can induce robust, heterologous cellular and humoral immune responses against multiple HCV antigens. Intriguingly, the induction of this cross-reactive immunity leads to significant reduction of viral loads in a recombinant vaccinia-HCV virus infected mouse model, supporting their role in antiviral immunity against HCV. Healthy human subjects with Ad-specific pre-existing immunity demonstrated cross-reactive cellular and humoral immune responses against multiple HCV antigens. These findings reveal the potential of a previously uncharacterized property of natural human adenovirus infection to dictate, modulate and/or alter the course of HCV infection upon exposure. This intrinsic property of adenovirus vectors to cross-prime HCV immunity can also be exploited to develop a prophylactic and/or therapeutic vaccine against HCV.
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Project description:Whether hepatitis B virus (HBV) activates or represses innate immunity continues to be debated. Toll-like receptor (TLR) 2 has been identified to recognize HBV particles in human hepatocytes. The Hippo pathway, known for growth control, is suggested to play a vital role in immune regulation. Here, molecular interactions between HBV-triggered TLR signaling and the Hippo pathway were comprehensively investigated. Reanalysis of GSE69590 data, in which human hepatocytes have been treated with cell culture-derived HBV particles, identified changes in Hippo and NF-κB signaling. Immunocytochemical staining and western blotting revealed time-dependent nuclear translocation of YAP and NF-κB in HBV-exposed primary human and murine hepatocytes (PMH). Analysis of PMH isolated from MyD88- or IRAK4-deficient mice and the inhibition of TLR2 and MST1/2 in vitro confirmed the relation between TLR2 and Hippo signaling in HBV-induced immunity. Loss and gain of function experiments implied that Hippo-downstream effector YAP directly regulated IκBα expression. Functional investigations confirmed the regulation of Nfkbia promoter activity by the YAP/TEAD4 transcription factor complex. Administration of TLR ligands to mice highlighted the relevance of the TLR2-MyD88-IRAK4-Hippo axis in hepatic immunity. Interestingly, reanalysis of gene expression pattern in liver biopsies of patients chronically infected with HBV (GSE83148, GSE65359) indicated an activation of TLR2 and however, an MST1-dominated Hippo control in the immune clearance phase of patients with chronic HBV infection. We demonstrated that MyD88-dependent TLR signaling activates NF-κB and Hippo signaling, with YAP prompting the IκBα-mediated negative feedback, alongside NF-κB. Imbalance between immune induction and Hippo activation may have implications for the safety of novel HBV cure strategies interfering with pathogen recognition receptors.
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Project description:Experimental studies on the interactions of the positive strand RNA virus hepatitis C virus (HCV) with the host have contributed to several discoveries in the field of antiviral innate immunity. These include revealing the antiviral sensing pathways that lead to the induction of type I interferon (IFN) during HCV infection and also the importance of type III IFNs in the antiviral immune response to HCV. These studies on HCV/host interactions have contributed to our overall understanding of viral sensing and viral evasion of the antiviral intracellular innate immune response. In this review, I will highlight how these studies of HCV/host interactions have led to new insights into antiviral innate immunity. Overall, I hope to emphasize that studying antiviral immunity in the context of virus infection is necessary to fully understand antiviral immunity and how it controls the outcome of viral infection.
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Project description:Infection with Hepatitis C Virus (HCV) causes chronic disease in approximately 80% of cases, resulting in chronic inflammation and cirrhosis. Current treatments are not completely effective, and a vaccine has yet to be developed. Spontaneous resolution of infection is associated with effective host adaptive immunity to HCV, including production of both HCV-specific T cells and neutralizing antibodies. However, the supporting role of soluble innate factors in protection against HCV is less well understood. The innate immune system provides an immediate line of defense against infections, triggering inflammation and playing a critical role in activating adaptive immunity. Innate immunity comprises both cellular and humoral components, the humoral arm consisting of pattern recognition molecules such as complement C1q, collectins and ficolins. These molecules activate the complement cascade, neutralize pathogens, and recruit antigen presenting cells. Here we review the current understanding of anti-viral components of the humoral innate immune system that play a similar role to antibodies, describing their role in immunity to HCV and their potential contribution to HCV pathogenesis.
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Project description:UNLABELLED:Understanding the immunological correlates associated with protective immunity following hepatitis C virus (HCV) reexposure is a prerequisite for the design of effective HCV vaccines and immunotherapeutics. In this study we performed a comprehensive analysis of innate and adaptive immunity following HCV reexposure of two chimpanzees that had previously recovered from HCV-JFH1 infection. One of the chimpanzees, CH10274, became protected from active viremia by repeated challenges with homologous HCV-JFH1 and developed neutralizing antibodies, but was later infected with high-level viremia by a heterologous challenge with the HCV H77 virus that persisted for more than 1 year. The other chimpanzee, CH10273, was protected from a similar, heterologous H77 challenge without any evidence of neutralizing antibodies. Peripheral HCV-specific T-cell responses were present in both chimpanzees after challenges and, interestingly, the overall magnitude of response was lower in uninfected CH10273, which, however, exhibited a more robust CD8+ T-cell response. CH10273 showed higher hepatic expression of CD8 and CD56 (natural killer) markers than CH10274 did shortly after inoculation with H77. The heightened T-cell response was associated with an enhanced hepatic production of interferons (both type I and II) and interferon-stimulated genes (ISGs) in CH10273. Therefore, protection or clearance of HCV reinfection upon heterologous rechallenge depends on the activation of both intrahepatic innate and cellular immune responses. Furthermore, our results suggest that serum neutralizing antibodies may contribute to early control of viral replication and spread after homologous HCV rechallenges but may not be sufficient for a long-term protective immunity. CONCLUSION:Our study shows that protective immunity against HCV reinfection is orchestrated by a complex network of innate and adaptive immune responses.
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Project description:Coronaviruses (CoVs) are positive-sense RNA viruses that infect numerous mammalian and avian species and are capable of causing severe and lethal disease in humans. CoVs encode several innate immune antagonists that counteract the host innate immune response to facilitate efficient viral replication. CoV nonstructural protein 14 (nsp14) encodes 3'-to-5' exoribonuclease activity (ExoN), which performs a proofreading function and is required for high-fidelity replication. Outside of the order Nidovirales, arenaviruses are the only RNA viruses that encode an ExoN, which functions to degrade double-stranded RNA (dsRNA) replication intermediates. In this study, we tested the hypothesis that CoV ExoN also functions to antagonize the innate immune response. We demonstrate that viruses lacking ExoN activity [ExoN(-)] are sensitive to cellular pretreatment with interferon beta (IFN-β) in a dose-dependent manner. In addition, ExoN(-) virus replication was attenuated in wild-type bone marrow-derived macrophages (BMMs) and partially restored in interferon alpha/beta receptor-deficient (IFNAR-/-) BMMs. ExoN(-) virus replication did not result in IFN-β gene expression, and in the presence of an IFN-β-mediated antiviral state, ExoN(-) viral RNA levels were not substantially reduced relative to those of untreated samples. However, ExoN(-) virus generated from IFN-β-pretreated cells had reduced specific infectivity and decreased relative fitness, suggesting that ExoN(-) virus generated during an antiviral state is less viable to establish a subsequent infection. Overall, our data suggest murine hepatitis virus (MHV) ExoN activity is required for resistance to the innate immune response, and antiviral mechanisms affecting the viral RNA sequence and/or an RNA modification act on viruses lacking ExoN activity.IMPORTANCE CoVs encode multiple antagonists that prevent or disrupt an efficient innate immune response. Additionally, no specific antiviral therapies or vaccines currently exist for human CoV infections. Therefore, the study of CoV innate immune antagonists is essential for understanding how CoVs overcome host defenses and to maximize potential therapeutic interventions. Here, we sought to determine the contributions of nsp14 ExoN activity in the induction of and resistance to the innate immune response. We show that viruses lacking nsp14 ExoN activity are more sensitive than wild-type MHV to restriction by exogenous IFN-β and that viruses produced in the presence of an antiviral state are less capable of establishing a subsequent viral infection. Our results support the hypothesis that murine hepatitis virus ExoN activity is required for resistance to the innate immune response.
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Project description:Hepatitis C virus (HCV) is a major human pathogen of chronic hepatitis and related liver diseases. Innate immunity is the first line of defense against invading foreign pathogens, and its activation is dependent on the recognition of these pathogens by several key sensors. The interferon (IFN) system plays an essential role in the restriction of HCV infection via the induction of hundreds of IFN-stimulated genes (ISGs) that inhibit viral replication and spread. However, numerous factors that trigger immune dysregulation, including viral factors and host genetic factors, can help HCV to escape host immune response, facilitating viral persistence. In this review, we aim to summarize recent advances in understanding the innate immune response to HCV infection and the mechanisms of ISGs to suppress viral survival, as well as the immune evasion strategies for chronic HCV infection.
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