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Altstetter SM, Quitt O, Pinci F, Hornung V, Lucko AM, Wisskirchen K, Jung S, Protzer U. Hepatitis-D Virus Infection Is Not Impaired by Innate Immunity but Increases Cytotoxic T-Cell Activity. Cells 2021; 10:3253. [PMID: 34831475 PMCID: PMC8619298 DOI: 10.3390/cells10113253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/08/2021] [Accepted: 11/18/2021] [Indexed: 11/22/2022] Open
Abstract
Approximately 70 million humans worldwide are affected by chronic hepatitis D, which rapidly leads to liver cirrhosis and hepatocellular carcinoma due to chronic inflammation. The triggers and consequences of this chronic inflammation, induced by co-infection with the hepatitis D virus (HDV) and the hepatitis B virus (HBV), are poorly understood. Using CRISPR technology, we characterized the recognition of HDV mono- and co-infection by intracellular innate immunity and determined its influence on the viral life cycle and effector T-cell responses using different HBV and HDV permissive hepatoma cell lines. We showed that HDV infection is detected by MDA5 and -after a lag phase -induces a profound type I interferon response in the infected cells. The type I interferon response, however, was not able to suppress HDV replication or spread, thus providing a persistent trigger. Using engineered T-cells directed against the envelope proteins commonly used by HBV and HDV, we found that HDV immune recognition enhanced T-cell cytotoxicity. Interestingly, the T-cell effector function was enhanced independently of antigen presentation. These findings help to explain immune mediated tissue damage in chronic hepatitis D patients and indicate that combining innate triggers with T-cell activating therapies might allow for a curative approach.
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Affiliation(s)
- Sebastian Maximilian Altstetter
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
| | - Oliver Quitt
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
| | - Francesca Pinci
- Gene Center and Department of Biochemistry, Ludwig-Maximilians—University Munich, 81377 Munich, Germany; (F.P.); (V.H.)
| | - Veit Hornung
- Gene Center and Department of Biochemistry, Ludwig-Maximilians—University Munich, 81377 Munich, Germany; (F.P.); (V.H.)
| | - Aaron Michael Lucko
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
| | - Karin Wisskirchen
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
| | - Stephanie Jung
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
- Institute of Cardiovascular Immunology, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
| | - Ulrike Protzer
- Institute of Virology, School of Medicine, Helmholtz Zentrum München/Technical University of Munich, 81675 Munich, Germany; (S.M.A.); (O.Q.); (A.M.L.); (K.W.)
- German Center for Infection Research (DZIF), Munich Partner Site, 81675 Munich, Germany
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Novotny LA, Evans JG, Su L, Guo H, Meissner EG. Review of Lambda Interferons in Hepatitis B Virus Infection: Outcomes and Therapeutic Strategies. Viruses 2021; 13:1090. [PMID: 34207487 PMCID: PMC8230240 DOI: 10.3390/v13061090] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/27/2021] [Accepted: 06/01/2021] [Indexed: 12/27/2022] Open
Abstract
Hepatitis B virus (HBV) chronically infects over 250 million people worldwide and causes nearly 1 million deaths per year due to cirrhosis and liver cancer. Approved treatments for chronic infection include injectable type-I interferons and nucleos(t)ide reverse transcriptase inhibitors. A small minority of patients achieve seroclearance after treatment with type-I interferons, defined as sustained absence of detectable HBV DNA and surface antigen (HBsAg) antigenemia. However, type-I interferons cause significant side effects, are costly, must be administered for months, and most patients have viral rebound or non-response. Nucleos(t)ide reverse transcriptase inhibitors reduce HBV viral load and improve liver-related outcomes, but do not lower HBsAg levels or impart seroclearance. Thus, new therapeutics are urgently needed. Lambda interferons (IFNLs) have been tested as an alternative strategy to stimulate host antiviral pathways to treat HBV infection. IFNLs comprise an evolutionarily conserved innate immune pathway and have cell-type specific activity on hepatocytes, other epithelial cells found at mucosal surfaces, and some immune cells due to restricted cellular expression of the IFNL receptor. This article will review work that examined expression of IFNLs during acute and chronic HBV infection, the impact of IFNLs on HBV replication in vitro and in vivo, the association of polymorphisms in IFNL genes with clinical outcomes, and the therapeutic evaluation of IFNLs for the treatment of chronic HBV infection.
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Affiliation(s)
- Laura A. Novotny
- Division of Infectious Diseases, Medical University of South Carolina, Charleston, SC 29525, USA; (L.A.N.); (J.G.E.)
| | - John Grayson Evans
- Division of Infectious Diseases, Medical University of South Carolina, Charleston, SC 29525, USA; (L.A.N.); (J.G.E.)
| | - Lishan Su
- Division of Virology, Pathogenesis, and Cancer, Institute of Human Virology, Departments of Pharmacology, Microbiology, and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Haitao Guo
- Department of Microbiology and Molecular Genetics, Cancer Virology Program, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA;
| | - Eric G. Meissner
- Division of Infectious Diseases, Medical University of South Carolina, Charleston, SC 29525, USA; (L.A.N.); (J.G.E.)
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 29425, USA
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3
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Jung S, Altstetter SM, Protzer U. Innate immune recognition and modulation in hepatitis D virus infection. World J Gastroenterol 2020; 26:2781-2791. [PMID: 32550754 PMCID: PMC7284172 DOI: 10.3748/wjg.v26.i21.2781] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 03/30/2020] [Accepted: 05/23/2020] [Indexed: 02/06/2023] Open
Abstract
Hepatitis D virus (HDV) is a global health threat with more than 15 million humans affected. Current treatment options are largely unsatisfactory leaving chronically infected humans at high risk to develop liver cirrhosis and hepatocellular carcinoma. HDV is the only human satellite virus known. It encodes only two proteins, and requires Hepatitis B virus (HBV) envelope protein expression for productive virion release and spread of the infection. How HDV could evolve and why HBV was selected as a helper virus remains unknown. Since the discovery of Na+-taurocholate co-transporting polypeptide as the essential uptake receptor for HBV and HDV, we are beginning to understand the interactions of HDV and the immune system. While HBV is mostly regarded a stealth virus, that escapes innate immune recognition, HBV-HDV coinfection is characterized by a strong innate immune response. Cytoplasmic RNA sensor melanoma differentiation antigen 5 has been reported to recognize HDV RNA replication and activate innate immunity. Innate immunity, however, seems not to impair HDV replication while it inhibits HBV. In this review, we describe what is known up-to-date about the interplay between HBV as a helper and HDV’s immune evasion strategy and identify where additional research is required.
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MESH Headings
- Carcinoma, Hepatocellular/immunology
- Carcinoma, Hepatocellular/pathology
- Carcinoma, Hepatocellular/virology
- Coinfection/complications
- Coinfection/immunology
- Coinfection/pathology
- Coinfection/virology
- Hepatitis B virus/genetics
- Hepatitis B virus/immunology
- Hepatitis B virus/metabolism
- Hepatitis B, Chronic/complications
- Hepatitis B, Chronic/immunology
- Hepatitis B, Chronic/pathology
- Hepatitis B, Chronic/virology
- Hepatitis D, Chronic/complications
- Hepatitis D, Chronic/immunology
- Hepatitis D, Chronic/pathology
- Hepatitis D, Chronic/virology
- Hepatitis Delta Virus/genetics
- Hepatitis Delta Virus/immunology
- Hepatitis Delta Virus/metabolism
- Hepatitis delta Antigens/immunology
- Hepatitis delta Antigens/metabolism
- Humans
- Immune Evasion
- Immunity, Innate
- Interferon-Induced Helicase, IFIH1/metabolism
- Liver/immunology
- Liver/pathology
- Liver/virology
- Liver Cirrhosis/immunology
- Liver Cirrhosis/pathology
- Liver Cirrhosis/virology
- Liver Neoplasms/immunology
- Liver Neoplasms/pathology
- Liver Neoplasms/virology
- Organic Anion Transporters, Sodium-Dependent/metabolism
- RNA, Viral/immunology
- RNA, Viral/metabolism
- Receptors, Pattern Recognition/immunology
- Receptors, Pattern Recognition/metabolism
- Satellite Viruses/genetics
- Satellite Viruses/immunology
- Satellite Viruses/metabolism
- Symporters/metabolism
- Virus Replication/immunology
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Affiliation(s)
- Stephanie Jung
- Institute of Virology, Technical University of Munich/Helmholtz Zentrum München, Munich D-81675, Germany
| | | | - Ulrike Protzer
- Institute of Virology, Technical University of Munich/Helmholtz Zentrum München, Munich D-81675, Germany
- German Center for Infection Research (DZIF), Munich Partner Site, Munich D-81675, Germany
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4
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Suslov A, Boldanova T, Wang X, Wieland S, Heim MH. Hepatitis B Virus Does Not Interfere With Innate Immune Responses in the Human Liver. Gastroenterology 2018; 154:1778-1790. [PMID: 29408639 DOI: 10.1053/j.gastro.2018.01.034] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 01/17/2018] [Accepted: 01/20/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Most viruses are detected at early stages of cell infection and induce an innate immune response mediated by production of interferons (IFNs). IFNs induce expression of hundreds of IFN-stimulated genes (ISGs). Infection of chimpanzees with hepatitis C virus, but not hepatitis B virus (HBV), induces ISG expression in the liver. HBV might not induce an innate immune response because it is not detected by pattern recognition receptors (the stealth properties of HBV) or because HBV suppresses IFN production or signaling despite detection by pattern recognition receptors. We studied innate immune signaling in liver biopsies from patients with different stages of chronic HBV infection and uninfected individuals (controls). METHODS We obtained liver within 10 minutes after collection from 30 patients with chronic HBV infection (hepatitis B e antigen-positive or -negative, with or without hepatitis) and 42 controls (most with fatty liver disease). The liver tissues were analyzed by histology, immunohistochemistry, quantitative reverse-transcription polymerase chain reaction, in situ hybridization, HBV RNA quantification, and HBV genotyping; some specimens were incubated with toll-like receptor (TLR) ligands (polyinosinic-polycytidylic acid) or infected with Sendai virus and then analyzed. RESULTS Liver specimens from patients with HBV infection were not expressing more IFN or ISGs than those from control patients, indicating that chronic HBV infection did not activate an innate immune response. However, liver specimens from patients with HBV infection did produce IFN and induce expression of ISGs following activation of TLR3 with poly(I:C) or Sendai virus infections, so the innate immune response is not suppressed in these tissues. CONCLUSION Liver tissues from patients with chronic HBV infection do not have induction of an innate immune response, but this response can be activated by other factors (TLR3 binding, Sendai virus infection) in HBV-infected liver tissue. These findings support the hypothesis that HBV is invisible to pattern recognition receptors.
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Affiliation(s)
- Aleksei Suslov
- Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland
| | - Tujana Boldanova
- Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland; Division of Gastroenterology and Hepatology, University Hospital Basel, Basel, Switzerland
| | - Xueya Wang
- Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland
| | - Stefan Wieland
- Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland.
| | - Markus H Heim
- Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland; Division of Gastroenterology and Hepatology, University Hospital Basel, Basel, Switzerland.
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5
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Romani S, Hosseini SM, Mohebbi SR, Boonstra A, Sharifian A. Differential expression of innate immune response genes in clinical phases of chronic hepatitis B infection. J Viral Hepat 2017; 24:776-788. [PMID: 28218976 DOI: 10.1111/jvh.12699] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 02/01/2017] [Indexed: 12/16/2022]
Abstract
We investigated innate immune gene expression in clinical phases of chronic hepatitis B infection, including immune tolerant (IT), immune active (IA), inactive carrier (IC) and hepatitis B e antigen (HBeAg)-negative phases, as well as healthy controls. Expression levels of interferon types I, II and III, their receptor subunits, IRFs, TLRs and other IFN-induced genes in peripheral blood mononuclear cells were compared. Forty HBsAg-positive treatment-naïve subjects without co-infection with HIV, HCV or HDV were enrolled. To complement the viral load, the expression levels of 37 innate immune genes were measured by qPCR. The highest response of the innate immune system was observed in the IT and HBeAg-negative phases, and the IC phase had the lowest response; 31 of the 37 studied genes reached their maximum mRNA expression levels in the IT and HBeAg-negative phases, and the minimum expression levels of 23 genes were found in the IC phase. The highest mRNA expression levels of IFNs, IFN receptor subunits, IRFs and TLRs genes in all clinical phases were IFN-λ2 and 3, IFN-γR2, IRF7 and TLR7, and the lowest levels of mRNA expression were observed for IFN-α, IFN-λR1, IRF8 and TLR2. We conclude that innate immune response genes are expressed differentially among chronic HBV phases, and this difference may help to develop new precise and noninvasive methods to determine the progression of disease in chronic HBV patients.
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Affiliation(s)
- S Romani
- Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran
| | - S M Hosseini
- Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran
| | - S R Mohebbi
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - A Boonstra
- Department of Gastroenterology and Hepatology, Erasmus MC University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - A Sharifian
- Basic and Molecular Epidemiology of gastrointestinal Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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6
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Yu Y, Wan P, Cao Y, Zhang W, Chen J, Tan L, Wang Y, Sun Z, Zhang Q, Wan Y, Zhu Y, Liu F, Wu K, Liu Y, Wu J. Hepatitis B Virus e Antigen Activates the Suppressor of Cytokine Signaling 2 to Repress Interferon Action. Sci Rep 2017; 7:1729. [PMID: 28496097 PMCID: PMC5431827 DOI: 10.1038/s41598-017-01773-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 03/31/2017] [Indexed: 12/18/2022] Open
Abstract
Hepatitis B virus (HBV) infection causes acute hepatitis B (AHB), chronic hepatitis B (CHB), liver cirrhosis (LC), and eventually hepatocellular carcinoma (HCC). The presence of hepatitis B e antigen (HBeAg) in the serum generally indicates ongoing viral replication and disease progression. However, the mechanism by which HBeAg regulates HBV infection remains unclear. Interferons (IFNs) are pleiotropic cytokines that participate in host innate immunity. After binding to receptors, IFNs activate the JAK/STAT pathway to stimulate expression of IFN-stimulated genes (ISGs), leading to induction of antiviral responses. Here, we revealed that HBeAg represses IFN/JAK/STAT signaling to facilitate HBV replication. Initially, HBeAg stimulates the expression of suppressor of cytokine signaling 2 (SOCS2). Subsequently, SOCS2 impairs IFN/JAK/STAT signaling through reducing the stability of tyrosine kinase 2 (TYK2), downregulating the expression of type I and III IFN receptors, attenuating the phosphorylation and nucleus translocation of STAT1. Finally, SOCS2 inhibits the expression of ISGs, which leads to the repression of IFN action and facilitation of viral replication. These results demonstrate an important role of HBeAg in the regulation of IFN action, and provide a possible molecular mechanism by which HBV resists the IFN therapy and maintains persistent infection.
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Affiliation(s)
- Yi Yu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China.,Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Pin Wan
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Yanhua Cao
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Wei Zhang
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Junbo Chen
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Li Tan
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Yan Wang
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Zhichen Sun
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Qi Zhang
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Yushun Wan
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Ying Zhu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Fang Liu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China
| | - Kailang Wu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China.
| | - Yingle Liu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China.
| | - Jianguo Wu
- State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, 430071, China.
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7
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Hepatitis B virus spliced variants are associated with an impaired response to interferon therapy. Sci Rep 2015; 5:16459. [PMID: 26585041 PMCID: PMC4653653 DOI: 10.1038/srep16459] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/14/2015] [Indexed: 02/08/2023] Open
Abstract
During hepatitis B virus (HBV) replication, spliced HBV genomes and splice-generated proteins have been widely described, however, their biological and clinical significance remains to be defined. Here, an elevation of the proportion of HBV spliced variants in the sera of patients with chronic hepatitis B (CHB) is shown to correlate with an impaired respond to interferon-α (IFN-α) therapy. Transfection of the constructs encoding the three most dominant species of spliced variants into cells or ectopic expression of the two major spliced protein including HBSP and N-terminal-truncated viral polymerase protein result in strong suppression of IFN-α signaling transduction, while mutation of the major splicing-related sites of HBV attenuates the viral anti-IFN activities in both cell and mouse models. These results have associated the productions of HBV spliced variants with the failure response to IFN therapy and illuminate a novel mechanism where spliced viral products are employed to resist IFN-mediated host defense.
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8
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Yi Z, Chen J, Kozlowski M, Yuan Z. Innate detection of hepatitis B and C virus and viral inhibition of the response. Cell Microbiol 2015; 17:1295-303. [PMID: 26243406 DOI: 10.1111/cmi.12489] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 07/07/2015] [Accepted: 07/17/2015] [Indexed: 12/23/2022]
Abstract
Viral hepatitis caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) infections poses a significant burden to the public health system. Although HBV and HCV differ in structure and life cycles, they share unique characteristics, such as tropism to infect hepatocytes and association with hepatic and extrahepatic disorders that are of innate immunity nature. In response to HBV and HCV infection, the liver innate immune cells eradicate pathogens by recognizing specific molecules expressed by pathogens via distinct cellular pattern recognition receptors whose triggering activates intracellular signalling pathways inducing cytokines, interferons and anti-viral response genes that collectively function to clear infections. However, HBV and HCV evolve strategies to inactivate innate signalling factors and as such establish persistent infections without being recognized by the innate immunity. We review recent insights into how HBV and HCV are sensed and how they evade innate immunity to establish chronicity. Understanding the mechanisms of viral hepatitis is mandatory to develop effective and safe therapies for eradication of viral hepatitis.
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Affiliation(s)
- Zhigang Yi
- Key Laboratory of Medical Molecular Virology, Department of Medical Microbiology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jieliang Chen
- Key Laboratory of Medical Molecular Virology, Department of Medical Microbiology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Maya Kozlowski
- Key Laboratory of Medical Molecular Virology, Department of Medical Microbiology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Zhenghong Yuan
- Key Laboratory of Medical Molecular Virology, Department of Medical Microbiology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.,Institutes of Medical Microbiology and Biomedical Sciences, Fudan University, Shanghai, China
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9
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Tan A, Koh S, Bertoletti A. Immune Response in Hepatitis B Virus Infection. Cold Spring Harb Perspect Med 2015; 5:a021428. [PMID: 26134480 DOI: 10.1101/cshperspect.a021428] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hepatitis B virus (HBV) can replicate within hepatocytes without causing direct cell damage. The host immune response is, therefore, not only essential to control the spread of virus infection, but it is also responsible for the inflammatory events causing liver pathologies. In this review, we discuss how HBV deals with host immunity and how we can harness it to achieve virus control and suppress liver damage.
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Affiliation(s)
- Anthony Tan
- Program Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore 169857
| | - Sarene Koh
- Viral Hepatitis Laboratory, Singapore Institute for Clinical Sciences, A*STAR, Singapore 117609
| | - Antonio Bertoletti
- Program Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore 169857 Viral Hepatitis Laboratory, Singapore Institute for Clinical Sciences, A*STAR, Singapore 117609 School of Immunity and Infection, College of Medical and Dental Science, University of Birmingham, Edgbaston, Birmingham B16 2TT, United Kingdom
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10
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Seeger C, Mason WS. Molecular biology of hepatitis B virus infection. Virology 2015; 479-480:672-86. [PMID: 25759099 PMCID: PMC4424072 DOI: 10.1016/j.virol.2015.02.031] [Citation(s) in RCA: 605] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 02/09/2015] [Accepted: 02/16/2015] [Indexed: 02/06/2023]
Abstract
Human hepatitis B virus (HBV) is the prototype of a family of small DNA viruses that productively infect hepatocytes, the major cell of the liver, and replicate by reverse transcription of a terminally redundant viral RNA, the pregenome. Upon infection, the circular, partially double-stranded virion DNA is converted in the nucleus to a covalently closed circular DNA (cccDNA) that assembles into a minichromosome, the template for viral mRNA synthesis. Infection of hepatocytes is non-cytopathic. Infection of the liver may be either transient (<6 months) or chronic and lifelong, depending on the ability of the host immune response to clear the infection. Chronic infections can cause immune-mediated liver damage progressing to cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of carcinogenesis are unclear. Antiviral therapies with nucleoside analog inhibitors of viral DNA synthesis delay sequelae, but cannot cure HBV infections due to the persistence of cccDNA in hepatocytes.
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11
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Abstract
Hepatitis B virus (HBV) infection acquired in adult life is generally self-limited while chronic persistence of the virus is the prevalent outcome when infection is acquired perinatally. Both control of infection and liver cell injury are strictly dependent upon protective immune responses, because hepatocyte damage is the price that the host must pay to get rid of intracellular virus. Resolution of acute hepatitis B is associated with functionally efficient, multispecific antiviral T-cell responses which are preceded by a poor induction of intracellular innate responses at the early stages of infection. Persistent control of infection is provided by long-lasting protective memory, which is probably sustained by continuous stimulation of the immune system by trace amounts of virus which are never totally eliminated, persisting in an occult episomic form in the nucleus of liver cells even after recovery from acute infection. Chronic virus persistence is instead characterized by a lack of protective T-cell memory maturation and by an exhaustion of HBV-specific T-cell responses. Persistent exposure of T cells to high antigen loads is a key determinant of functional T-cell impairment but also other mechanisms can contribute to T-cell inhibition, including the tolerogenic effect of the liver environment. The degree of T-cell impairment is variable and its severity is related to the level of virus replication and antigen load. The antiviral T-cell function is more efficient in patients who can control infection either partially, such as inactive HBsAg carriers with low levels of virus replication, or completely, such as patients who achieve HBsAg loss either spontaneously or after antiviral therapy. Thus, understanding the features of the immune responses associated with control of infection is needed for the successful design of novel immune modulatory therapies based on the reconstitution of efficient antiviral responses in chronic HBV patients.
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Affiliation(s)
- Carlo Ferrari
- Unit of Infectious Disease and Hepatology, Laboratory of Viral Immunopathology, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy
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12
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Interplay between hepatitis B virus and the innate immune responses: implications for new therapeutic strategies. Virol Sin 2014; 29:17-24. [PMID: 24452540 DOI: 10.1007/s12250-014-3412-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/06/2014] [Indexed: 01/03/2023] Open
Abstract
Hepatitis B virus (HBV) infection is still a worldwide health problem; however, the current antiviral therapies for chronic hepatitis B are limited in efficacy. The outcome of HBV infection is thought to be the result of complex interactions between the HBV and the host immune system. While the role of the adaptive immune responses in the resolution of HBV infection has been well characterized, the contribution of innate immune mechanisms remains elusive until recent evidence implicates that HBV appears to activate the innate immune response and this response is important for controlling HBV infection. Here, we review our current understanding of innate immune responses to HBV infection and the multifaceted evasion by the virus and discuss the potential strategies to combat chronic HBV infection via induction and restoration of host innate antiviral responses.
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13
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Jones SA, Hu J. Hepatitis B virus reverse transcriptase: diverse functions as classical and emerging targets for antiviral intervention. Emerg Microbes Infect 2013; 2:e56. [PMID: 26038488 PMCID: PMC3820986 DOI: 10.1038/emi.2013.56] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/21/2013] [Indexed: 12/12/2022]
Abstract
Hepatitis B virus (HBV) infection remains a global health problem with over 350 million chronically infected, causing an increased risk of cirrhosis and hepatocellular carcinoma. Current antiviral chemotherapy for HBV infection include five nucleos(t)ide analog reverse transcriptase inhibitors (NRTIs) that all target one enzymatic activity, DNA strand elongation, of the HBV polymerase (HP), a specialized reverse transcriptase (RT). NRTIs are not curative and long-term treatment is associated with toxicity and the emergence of drug resistant viral mutations, which can also result in vaccine escape. Recent studies on the multiple functions of HP have provided important mechanistic insights into its diverse roles during different stages of viral replication, including interactions with viral pregenomic RNA, RNA packaging into nucleocapsids, protein priming, minus- and plus-strand viral DNA synthesis, RNase H-mediated degradation of viral RNA, as well as critical host interactions that regulate the multiple HP functions. These diverse functions provide ample opportunities to develop novel HP-targeted antiviral treatments that should contribute to curing chronic HBV infection.
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Affiliation(s)
- Scott A Jones
- Department of Microbiology and Immunology, The Penn State University College of Medicine, Hershey , PA 17033, USA
| | - Jianming Hu
- Department of Microbiology and Immunology, The Penn State University College of Medicine, Hershey , PA 17033, USA
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14
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Huang YW, Lin SC, Wei SC, Hu JT, Chang HY, Huang SH, Chen DS, Chen PJ, Hsu PN, Yang SS, Kao JH. Reduced Toll-like receptor 3 expression in chronic hepatitis B patients and its restoration by interferon therapy. Antivir Ther 2013; 18:877-84. [PMID: 23744559 DOI: 10.3851/imp2630] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Toll-like receptor (TLR)3 gene variants may correlate with clinical significance of chronic viral infections including HBV. We aimed to investigate the expression of TLR3 in peripheral blood mononuclear cells (PBMCs) and liver cells of chronic hepatitis B (CHB) patients and its response to pegylated interferon or nucleoside analogue therapy. METHODS We consecutively enrolled 127 CHB patients and 64 hepatitis B surface antigen-negative, anti-HCV-negative healthy individuals as controls. We compared the TLR3 expressions on fresh PBMCs and liver cells from patients and controls, before and during pegylated interferon or nucleoside analogue therapy. RESULTS Compared to controls, patients had a lower TLR3 mean fluorescence intensity (MFI) on PBMCs (mean ± sd 14.61 ± 13.49 versus 9.70 ± 4.61; P < 0.001), independent of age, gender and alanine aminotransferase (ALT; -13.466, 95% CI -17.202, -9.730; P < 0.001). Patients had limited TLR3 stains on Kupffer cells, whereas controls had diffuse stains on Kupffer and hepatocytes. Hepatic TLR3 messenger RNA was lower in patients than controls (0.47 ± 0.30 versus 1-fold). Using pretreatment TLR3 MFI as a referent, among 5 of 12 pegylated-interferon-treated patients with sustained virological response (SVR), TLR3 MFI was restored to a mean of 1.5- to 1.7-folds immediately after treatment. Among seven non-responders or relapsers, TLR3 MFI reduced to a mean of 0.5- to 0.7-fold. Among 10 entecavir-treated patients with on-treatment virological response, TLR3 MFI gradually was restored to a mean of 1.2-folds during 48-week therapy. CONCLUSIONS CHB patients have reduced TLR3 expression on PBMCs, independent of age, gender and ALT, and on liver cells. Patients with pegylated-interferon-induced SVR have a more significant restoration of TLR3 expression than those under entecavir.
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Affiliation(s)
- Yi-Wen Huang
- Liver Center, Cathay General Hospital Medical Center, Taipei, Taiwan
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15
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Chen J, Wu M, Zhang X, Zhang W, Zhang Z, Chen L, He J, Zheng Y, Chen C, Wang F, Hu Y, Zhou X, Wang C, Xu Y, Lu M, Yuan Z. Hepatitis B virus polymerase impairs interferon-α-induced STA T activation through inhibition of importin-α5 and protein kinase C-δ. Hepatology 2013; 57:470-82. [PMID: 22996189 DOI: 10.1002/hep.26064] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/30/2012] [Indexed: 12/24/2022]
Abstract
UNLABELLED Treatment with exogenous interferon (IFN)-α is not effective in the majority of patients with chronic hepatitis B virus (HBV) infection. Recent evidence suggests that HBV has evolved strategies to block the nuclear translocation of signal transducer and activator of transcription (STAT) 1 to limit IFN-α-induced cellular antiviral responses. However, it remains unclear whether STAT1 translocation is impaired in chronic hepatitis B patients and what mechanisms are involved. Here we report that the expression of HBV polymerase (Pol) in human hepatic cell lines inhibited induction of IFN-stimulated genes and resulted in a weakened antiviral activity of IFN-α. Ectopic expression of Pol suppressed IFN-α-induced STAT1 serine 727 phosphorylation and STAT1/2 nuclear accumulation, whereas STAT1 tyrosine 701 phosphorylation, and STAT1-STAT2 heterodimer formation were not affected. Further studies demonstrated that Pol interacted with the catalytic domain of protein kinase C-δ (PKC-δ) and perturbed PKC-δ phosphorylation and its association with STAT1, which resulted in the suppression of STAT1 Ser727 phosphorylation. Moreover, Pol was found to interfere with nuclear transportation of STAT1/2 by competitively binding to the region of importin-α5 required for STAT1/2 recruitment. Truncation analysis suggested that the terminal protein and RNase H domains of Pol were able to bind to PKC-δ and importin-α5, respectively, and were responsible for the inhibition of IFN-α signaling. More importantly, the inhibition of STAT1 and PKC-δ phosphorylation were confirmed in a hydrodynamic-based HBV mouse model, and the blockage of IFN-α-induced STAT1/2 nuclear translocation was observed in HBV-infected cells from liver biopsies of chronic HBV patients. CONCLUSIONS These results demonstrate a role for Pol in HBV-mediated antagonization of IFN-α signaling and provide a possible molecular mechanism by which HBV resists the IFN therapy and maintains its persistence.
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Affiliation(s)
- Jieliang Chen
- Key Laboratory of Medical Molecular Virology, Ministry of Education and HealthShanghai Medical College of Fudan University, Shanghai, China
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16
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Revill P, Yuan Z. New insights into how HBV manipulates the innate immune response to establish acute and persistent infection. Antivir Ther 2013; 18:1-15. [PMID: 23363957 DOI: 10.3851/imp2542] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2012] [Indexed: 10/27/2022]
Abstract
The mechanisms by which HBV establishes and maintains chronic infection are poorly understood. Although adult acquired HBV is generally cleared by a robust immune response, most individuals infected at childbirth or in very early childhood develop lifelong chronic infection. In addition, acute infections are unresolved in approximately 5% of individuals infected in adulthood. The host cell mechanisms that ensure establishment and resolution of acute infection and persistent infection remain unclear. Currently, two schools of thought suggest that either HBV is a 'stealth' virus, which initially establishes infection by avoiding host innate immune responses, or that HBV facilitates initial infection and progression to persistence by actively manipulating the host innate immune response to its advantage. There is increasing evidence that activation of innate host cell signalling pathways plays a major role in limiting adult acquired HBV infection and that, in turn, HBV has evolved numerous strategies to counteract these defence mechanisms. In this review, we summarize current knowledge regarding innate immune responses to HBV infection and discuss how HBV regulates cell signalling pathways to its advantage, particularly in the setting of chronic HBV infection. In turn, we show how an intimate knowledge of innate immune responses is driving development of novel therapeutic agents to treat chronic HBV infection.
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Affiliation(s)
- Peter Revill
- Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, Australia.
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17
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The hepatitis B virus ribonuclease H is sensitive to inhibitors of the human immunodeficiency virus ribonuclease H and integrase enzymes. PLoS Pathog 2013; 9:e1003125. [PMID: 23349632 PMCID: PMC3551811 DOI: 10.1371/journal.ppat.1003125] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 11/27/2012] [Indexed: 12/26/2022] Open
Abstract
Nucleos(t)ide analog therapy blocks DNA synthesis by the hepatitis B virus (HBV) reverse transcriptase and can control the infection, but treatment is life-long and has high costs and unpredictable long-term side effects. The profound suppression of HBV by the nucleos(t)ide analogs and their ability to cure some patients indicates that they can push HBV to the brink of extinction. Consequently, more patients could be cured by suppressing HBV replication further using a new drug in combination with the nucleos(t)ide analogs. The HBV ribonuclease H (RNAseH) is a logical drug target because it is the second of only two viral enzymes that are essential for viral replication, but it has not been exploited, primarily because it is very difficult to produce active enzyme. To address this difficulty, we expressed HBV genotype D and H RNAseHs in E. coli and enriched the enzymes by nickel-affinity chromatography. HBV RNAseH activity in the enriched lysates was characterized in preparation for drug screening. Twenty-one candidate HBV RNAseH inhibitors were identified using chemical structure-activity analyses based on inhibitors of the HIV RNAseH and integrase. Twelve anti-RNAseH and anti-integrase compounds inhibited the HBV RNAseH at 10 µM, the best compounds had low micromolar IC50 values against the RNAseH, and one compound inhibited HBV replication in tissue culture at 10 µM. Recombinant HBV genotype D RNAseH was more sensitive to inhibition than genotype H. This study demonstrates that recombinant HBV RNAseH suitable for low-throughput antiviral drug screening has been produced. The high percentage of compounds developed against the HIV RNAseH and integrase that were active against the HBV RNAseH indicates that the extensive drug design efforts against these HIV enzymes can guide anti-HBV RNAseH drug discovery. Finally, differential inhibition of HBV genotype D and H RNAseHs indicates that viral genetic variability will be a factor during drug development. Current therapy for HBV blocks DNA synthesis by the viral reverse transcriptase and can control the infection indefinitely, but treatment rarely cures patients. More patients could be cured by suppressing HBV replication further using a new drug in combination with the existing ones. The HBV RNAseH is a logical drug target because it is the second of only two viral enzymes that are essential for viral replication, but it has not been exploited, primarily because it is very difficult to produce active enzyme. We expressed active recombinant HBV RNAseHs and demonstrated that it was suitable for antiviral drug screening. Twenty-one candidate HBV RNAseH inhibitors were identified based on antagonists of the HIV RNAseH and integrase enzymes. Twelve of these compounds inhibited the HBV RNAseH in enzymatic assays, and one inhibited HBV replication in cell-based assays. The high percentage of compounds developed against the HIV RNAseH and integrase that were also active against the HBV RNAseH indicates that the extensive drug design efforts against these HIV enzymes can be used to guide anti-HBV RNAseH drug discovery.
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18
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Cryptic protein priming sites in two different domains of duck hepatitis B virus reverse transcriptase for initiating DNA synthesis in vitro. J Virol 2011; 85:7754-65. [PMID: 21593164 DOI: 10.1128/jvi.00483-11] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Initiation of reverse transcription in hepadnaviruses is accomplished by a unique protein-priming mechanism whereby a specific Y residue in the terminal protein (TP) domain of the viral reverse transcriptase (RT) acts as a primer to initiate DNA synthesis, which is carried out by the RT domain of the same protein. When separate TP and RT domains from the duck hepatitis B virus (DHBV) RT protein were tested in a trans-complementation assay in vitro, the RT domain could also serve, unexpectedly, as a protein primer for DNA synthesis, as could a TP mutant lacking the authentic primer Y (Y96) residue. Priming at these other, so-called cryptic, priming sites in both the RT and TP domains shared the same requirements as those at Y96. A mini RT protein with both the TP and RT domains linked in cis, as well as the full-length RT protein, could also initiate DNA synthesis using cryptic priming sites. The cryptic priming site(s) in TP was found to be S/T, while those in the RT domain were Y and S/T. As with the authentic TP Y96 priming site, the cryptic priming sites in the TP and RT domains could support DNA polymerization subsequent to the initial covalent linkage of the first nucleotide to the priming amino acid residue. These results provide new insights into the complex mechanisms of protein priming in hepadnaviruses, including the selection of the primer residue and the interactions between the TP and RT domains that is essential for protein priming.
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Pagliaccetti NE, Robek MD. Interferon-lambda in the immune response to hepatitis B virus and hepatitis C virus. J Interferon Cytokine Res 2011; 30:585-90. [PMID: 20645875 DOI: 10.1089/jir.2010.0060] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Approximately 500 million people worldwide are chronically infected with the hepatitis B virus (HBV) or hepatitis C virus (HCV), and are therefore at an increased risk for developing fatal liver diseases such as cirrhosis and hepatocellular carcinoma. The intracellular antiviral responses induced by interferon (IFN)-alpha/-beta and/or IFN-gamma play critical roles in the pathogenesis of HBV and HCV infection, and the function of IFN-lambda in the host immune response to these viruses is beginning to be revealed. A better understanding of how IFN-lambda influences HBV or HCV persistence is not only important for understanding the mechanisms of chronic virus infection, but also may lead to new approaches for improved antiviral therapies.
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Affiliation(s)
- Nicole E Pagliaccetti
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520-8023, USA
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20
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Yu S, Chen J, Wu M, Chen H, Kato N, Yuan Z. Hepatitis B virus polymerase inhibits RIG-I- and Toll-like receptor 3-mediated beta interferon induction in human hepatocytes through interference with interferon regulatory factor 3 activation and dampening of the interaction between TBK1/IKKepsilon and DDX3. J Gen Virol 2010; 91:2080-2090. [PMID: 20375222 DOI: 10.1099/vir.0.020552-0] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hepatitis B virus (HBV) infection remains one of the most serious health problems worldwide. Whilst studies have shown that HBV impairs interferon (IFN) production from dendritic cells in chronic hepatitis B patients, it remains unknown whether HBV inhibits IFN production in human hepatocytes. Using transient transfection assays in a primary human hepatocyte cell line (PH5CH8), this study demonstrated that HBV polymerase inhibits IFN-beta promoter activity induced by Newcastle disease virus, Sendai virus or poly(I : C) in a dose-dependent manner, whilst ectopic expression of the HBV core and X proteins had no effect on IFN-beta promoter activity. In addition, HBV polymerase blocked cellular IFN-beta expression and consequent antiviral immunity revealed by an infection protection assay. Furthermore, overexpression of key molecules on the IFN-beta induction axis, together with HBV polymerase, resulted in a block of IFN-beta promoter activity triggered by RIG-I, IPS-1, TRIF, TBK1 and IKKepsilon, but not by an IFN regulatory factor 3 dominant-positive mutant (IRF3-5D), suggesting that HBV polymerase prevents IFN-beta expression at the TBK1/IKKepsilon level. Further studies showed that HBV polymerase inhibited phosphorylation, dimerization and nuclear translocation of IRF3, in response to Sendai virus infection. Finally, it was shown that HBV polymerase-mediated dampening of the interaction between TBK1/IKKepsilon and DDX3 may be involved in the inhibitory effect on IFN-beta induction. Taken together, these findings reveal a novel role of HBV polymerase in HBV counteraction of IFN-beta production in human hepatocytes.
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Affiliation(s)
- Shiyan Yu
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
- Key Laboratory of Medical Molecular Virology, Ministry of Education and Public Health, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
| | - Jieliang Chen
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
- Key Laboratory of Medical Molecular Virology, Ministry of Education and Public Health, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
| | - Min Wu
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
| | - Hui Chen
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
- Key Laboratory of Medical Molecular Virology, Ministry of Education and Public Health, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
| | - Nobuyuki Kato
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
| | - Zhenghong Yuan
- Department of Tumour Virology, Okayama University, Okayama 700-8558, Japan
- Shanghai Public Health Clinical Center affiliated to Fudan University, Shanghai 201508, PR China
- Key Laboratory of Medical Molecular Virology, Ministry of Education and Public Health, Shanghai Medical College, Fudan University, Shanghai 200032, PR China
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21
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Wang H, Ryu WS. Hepatitis B virus polymerase blocks pattern recognition receptor signaling via interaction with DDX3: implications for immune evasion. PLoS Pathog 2010; 6:e1000986. [PMID: 20657822 PMCID: PMC2904777 DOI: 10.1371/journal.ppat.1000986] [Citation(s) in RCA: 164] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 06/04/2010] [Indexed: 12/12/2022] Open
Abstract
Viral infection leads to induction of pattern-recognition receptor signaling, which leads to interferon regulatory factor (IRF) activation and ultimately interferon (IFN) production. To establish infection, many viruses have strategies to evade the innate immunity. For the hepatitis B virus (HBV), which causes chronic infection in the liver, the evasion strategy remains uncertain. We now show that HBV polymerase (Pol) blocks IRF signaling, indicating that HBV Pol is the viral molecule that effectively counteracts host innate immune response. In particular, HBV Pol inhibits TANK-binding kinase 1 (TBK1)/IkappaB kinase-epsilon (IKKepsilon), the effector kinases of IRF signaling. Intriguingly, HBV Pol inhibits TBK1/IKKepsilon activity by disrupting the interaction between IKKepsilon and DDX3 DEAD box RNA helicase, which was recently shown to augment TBK1/IKKepsilon activity. This unexpected role of HBV Pol may explain how HBV evades innate immune response in the early phase of the infection. A therapeutic implication of this work is that a strategy to interfere with the HBV Pol-DDX3 interaction might lead to the resolution of life-long persistent infection.
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Affiliation(s)
- Haifeng Wang
- Department of Biochemistry, Yonsei University, Seoul, Korea
| | - Wang-Shick Ryu
- Department of Biochemistry, Yonsei University, Seoul, Korea
- * E-mail:
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22
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Ait-goughoulte M, Lucifora J, Zoulim F, Durantel D. Innate antiviral immune responses to hepatitis B virus. Viruses 2010; 2:1394-1410. [PMID: 21994686 PMCID: PMC3185716 DOI: 10.3390/v2071394] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 06/22/2010] [Accepted: 07/01/2010] [Indexed: 02/06/2023] Open
Abstract
Hepatitis B virus (HBV) is a major cause of acute and chronic hepatitis in humans. As HBV itself is currently viewed as a non-cytopathic virus, the liver pathology associated with hepatitis B is mainly thought to be due to immune responses directed against HBV antigens. The outcome of HBV infection is the result of complex interactions between replicating HBV and the immune system. While the role of the adaptive immune response in the resolution of HBV infection is well understood, the contribution of innate immune mechanisms remains to be clearly defined. The innate immune system represents the first line of defense against viral infection, but its role has been difficult to analyze in humans due to late diagnosis of HBV infection. In this review, we discuss recent advances in the field of innate immunity to HBV infection.
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Affiliation(s)
- Malika Ait-goughoulte
- INSERM, U871, Molecular Physiopathology and New Treatment of Viral Hepatitis, 151 Cours Albert Thomas, 69003 Lyon, France; E-Mails: (M.A.-g.); (J.L.); (F.Z.)
- Université de Lyon, UCBL, and IFR62 Lyon Est, 69008 Lyon, France
| | - Julie Lucifora
- INSERM, U871, Molecular Physiopathology and New Treatment of Viral Hepatitis, 151 Cours Albert Thomas, 69003 Lyon, France; E-Mails: (M.A.-g.); (J.L.); (F.Z.)
- Université de Lyon, UCBL, and IFR62 Lyon Est, 69008 Lyon, France
| | - Fabien Zoulim
- INSERM, U871, Molecular Physiopathology and New Treatment of Viral Hepatitis, 151 Cours Albert Thomas, 69003 Lyon, France; E-Mails: (M.A.-g.); (J.L.); (F.Z.)
- Université de Lyon, UCBL, and IFR62 Lyon Est, 69008 Lyon, France
- Hospices Civils de Lyon (HCL), Hôtel Dieu Hospital, 69002 Lyon, France
| | - David Durantel
- INSERM, U871, Molecular Physiopathology and New Treatment of Viral Hepatitis, 151 Cours Albert Thomas, 69003 Lyon, France; E-Mails: (M.A.-g.); (J.L.); (F.Z.)
- Université de Lyon, UCBL, and IFR62 Lyon Est, 69008 Lyon, France
- Hospices Civils de Lyon (HCL), Hôtel Dieu Hospital, 69002 Lyon, France
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +33-472-681-970; Fax: +33-472-681-971
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Lucifora J, Durantel D, Testoni B, Hantz O, Levrero M, Zoulim F. Control of hepatitis B virus replication by innate response of HepaRG cells. Hepatology 2010; 51:63-72. [PMID: 19877170 DOI: 10.1002/hep.23230] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Hepatitis B virus (HBV) is currently viewed as a stealth virus that does not elicit innate immunity in vivo. This assumption has not yet been challenged in vitro because of the lack of a relevant cell culture system. The HepaRG cell line, which is physiologically closer to differentiated hepatocytes and permissive to HBV infection, has opened new perspectives in this respect.HBV baculoviruses were used to initiate an HBV replication in both HepG2 and HepaRG cells. To monitor HBV replication, the synthesis of encapsidated DNA, and secretion of hepatitis B surface antigen (HBsAg), was respectively analyzed by southern blot and enzyme-linked immunosorbent assay. The induction of a type I interferon (IFN) response was monitored by targeted quantitative reverse transcription polymerase chain reaction (qRT-PCR), low-density arrays, and functional assays. The invalidation of type I IFN response was obtained by either antibody neutralization or RNA interference. We demonstrate that HBV elicits a strong and specific innate antiviral response that results in a noncytopathic clearance of HBV DNA in HepaRG cells. Challenge experiment showed that transduction with Bac-HBV-WT, but not with control baculoviruses, leads to this antiviral response in HepaRG cells, whereas no antiviral response is observed in HepG2 cells. Cellular gene expression analyses showed that IFN-beta and other IFN-stimulated genes were up-regulated in HepG2 and HepaRG cells, but not in cells transduced by control baculoviruses. Interestingly, a rescue of viral replication was observed when IFN-beta action was neutralized by antibodies or RNA interference of type I IFN receptor. CONCLUSION Our data suggest that a strong HBV replication is able to elicit a type I IFN response in HepaRG-transduced cells.
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Affiliation(s)
- Julie Lucifora
- INSERM (Institut National de la Santé et de la Recherche Médicale), U871, Lyon, France
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24
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Inhibition of woodchuck hepatitis virus gene expression in primary hepatocytes by siRNA enhances the cellular gene expression. Virology 2008; 384:88-96. [PMID: 19064272 DOI: 10.1016/j.virol.2008.11.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2008] [Revised: 10/01/2008] [Accepted: 11/10/2008] [Indexed: 02/07/2023]
Abstract
Small interfering RNA (siRNA) has been shown to be active to inhibit the hepatitis B virus gene expression and replication in transient and stable transfection systems. Here in primary hepatocytes prepared from naturally woodchuck hepatitis virus (WHV)-infected woodchucks, four siRNAs targeting the WHV preS1, S, C, and X region led to a depletion of WHV transcripts and replicative intermediates with different kinetics and a decreased production of viral particles. Two siRNAs targeting WHV S and X region had the highest efficacy to deplete 70% of WHV transcripts and replicative intermediates. In addition, siRNA-mediated suppression of WHV enhanced the expression of cellular genes like MxA and MHC I. Specific siRNAs are able to inhibit the hepadnaviral replication and enhance the expression of cellular genes relevant for antiviral actions. Thus, siRNAs might be useful as novel antiviral agents for the treatment of chronic HBV infection.
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25
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26
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Wu M, Xu Y, Lin S, Zhang X, Xiang L, Yuan Z. Hepatitis B virus polymerase inhibits the interferon-inducible MyD88 promoter by blocking nuclear translocation of Stat1. J Gen Virol 2008; 88:3260-3269. [PMID: 18024894 DOI: 10.1099/vir.0.82959-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Previous studies have suggested that hepatitis B virus (HBV) blocks expression of the alpha interferon (IFN-alpha)-inducible myeloid differential primary response protein (MyD88) gene. To study the molecular mechanism(s) of the inhibition of MyD88 expression by HBV, MyD88 promoter reporter plasmids and vectors expressing different HBV viral proteins were constructed. Co-transfection experiments showed that IFN-induced MyD88 promoter activity was inhibited by HBV polymerase expression in a dose-dependent manner and that the terminal protein (TP) domain of HBV polymerase was responsible for this antagonistic activity. Analysis of site mutants showed that the region targeted by the polymerase protein contained the signal transducer and activator of transcription (Stat) binding site. Chromatin immunoprecipitation analysis showed that the IFN-induced DNA-binding activity of Stat1 was affected. Further study demonstrated that the HBV polymerase protein inhibited the Stat1 nuclear translocation induced by IFN-alpha, but did not induce Stat1 degradation nor interfere with its phosphorylation. In addition, HBV polymerase could inhibit the transcriptional activity of other IFN-stimulated response element-driven promoters and the expression of interferon-stimulated genes (ISGs), such as Stat1 and ISG15. In summary, these results indicate that HBV polymerase is a general inhibitor of IFN signalling and can inhibit IFN-inducible MyD88 expression by inhibiting the activity of the MyD88 promoter through blocking the nuclear translocation of Stat1.
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Affiliation(s)
- Min Wu
- Department of Research, Shanghai Public Health Clinic Center, Fudan University, Shanghai 201508, China.,Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Yang Xu
- Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Shanshan Lin
- Institutes of Medical Microbiology and Biomedical Sciences, Fudan University, Shanghai 200032, China.,Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Xiaonan Zhang
- Department of Research, Shanghai Public Health Clinic Center, Fudan University, Shanghai 201508, China
| | - Li Xiang
- Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Zhenghong Yuan
- Institutes of Medical Microbiology and Biomedical Sciences, Fudan University, Shanghai 200032, China.,Department of Research, Shanghai Public Health Clinic Center, Fudan University, Shanghai 201508, China.,Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
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Peltekian C, Gordien E, Garreau F, Meas-Yedid V, Soussan P, Willams V, Chaix ML, Olivo-Marin JC, Bréchot C, Kremsdorf D. Human MxA protein participates to the interferon-related inhibition of hepatitis B virus replication in female transgenic mice. J Hepatol 2005; 43:965-72. [PMID: 16168514 DOI: 10.1016/j.jhep.2005.06.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Revised: 06/13/2005] [Accepted: 06/15/2005] [Indexed: 12/19/2022]
Abstract
BACKGROUND/AIMS The interferon (IFN) inducible MxA protein is endowed with antiviral activity against a broad range of RNA viruses. In a previous in vitro study, we demonstrated that MxA inhibits hepatitis B virus (HBV) replication, arguing that the antiviral activity of MxA is not restricted to RNA viruses but also includes a DNA virus. The aim of the present study was to further demonstrate in vivo the antiviral action of MxA against HBV. METHODS We generated HBV and HBV/MxA transgenic mice lacking a functional IFN-alpha/beta receptor and thus constituting a good model to evaluate MxA-induced virus resistance. HBV proteins expression, viral load and HBV replication were compared in HBV and HBV/MxA mice. RESULTS An MxA-dependent moderate inhibitory effect on HBV expression was only observed in female HBV/MxA mice, in which MxA downregulates (i) viral HBeAg and capsid protein expression, (ii) viremia and (iii) HBV replication by decreasing the synthesis of HBV DNA replicative intermediates. Furthermore, these effects were not associated with changes to steady-state levels of HBV RNAs. CONCLUSIONS Our results show that in vivo, MxA is able per se to reduce HBV expression by a post-transcriptional mechanism, and thus participates in the antiviral activity of IFN-alpha against HBV.
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Affiliation(s)
- Cécile Peltekian
- INSERM U370/Institut Pasteur, Faculté de Médecine Necker Enfants-Malades, 156, rue de Vaugirard, 75015 Paris, France
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Clarke DTW, Irving AT, Lambley EH, Payne E, McMillan NAJ. A novel method for screening viral interferon-resistance genes. J Interferon Cytokine Res 2005; 24:470-7. [PMID: 15320960 DOI: 10.1089/1079990041689610] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Many viruses have evolved mechanisms to antagonize the interferon (IFN) system, targeting all the major components involved in receptor binding and signaling. Although a number of these vital proteins are homologous to cellular proteins involved in IFN downregulation (e.g., viral IFN regulatory factors [vIRFs]), many share little resemblance to known proteins. To determine the IFN-blocking properties of these proteins, functional assays are required. Here, we present a new and rapid functional screening method, based on the 2fTGH cell line, which is able to determine viral gene products that inhibit the IFN-alpha/Jak-Stat signaling pathway. Expression cloning of viral IFN-blocking genes into 2fTGH and consequent selection with IFN-alpha and 6-thioguanine result in the outgrowth of cells that are no longer responsive to IFN-alpha. We also demonstrate that selection occurs if members of the Jak-Stat signaling pathway are lost. To show the utility of our system, we have used a known suppressor of IFN signaling, the human papillomavirus (HPV) E7 gene. Expression of E7 causes the loss of ability of 2fTGH cells to respond to IFN-alpha treatment because of a functional disruption of the signaling pathway. This approach offers a new strategy for identifying novel viral genes or new functions of already described viral genes that have a role in IFN-alpha signaling inhibition.
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Affiliation(s)
- Daniel T W Clarke
- Centre for Immunology and Cancer Research, Princess Alexandra Hospital, University of Queensland, Brisbane, Australia
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Abstract
More than a half a century ago, interferons (IFN) were identified as antiviral cytokines. Since that discovery, IFN have been in the forefront of basic and clinical cytokine research. The pleiotropic nature of these cytokines continues to engage a large number of investigators to define their actions further. IFN paved the way for discovery of Janus tyrosine kinase (JAK)-signal transducing activators of transcription (STAT) pathways. A number of important tumor suppressive pathways are controlled by IFN. Several infectious pathogens counteract IFN-induced signaling pathways. Recent studies indicate that IFN activate several new protein kinases, including the MAP kinase family, and downstream transcription factors. This review not only details the established IFN signaling paradigms but also provides insights into emerging alternate signaling pathways and mechanisms of pathogen-induced signaling interference.
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Affiliation(s)
- Dhananjaya V Kalvakolanu
- Molecular and Cellular Biology Graduate Program, Greenebaum Cancer Center, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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Thompson ME, Barkhuizen A. Fibromyalgia, hepatitis C infection, and the cytokine connection. Curr Pain Headache Rep 2003; 7:342-7. [PMID: 12946286 DOI: 10.1007/s11916-003-0032-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Fibromyalgia and chronic hepatitis C infection share many clinical features including prominent somatic complaints such as musculoskeletal pain and fatigue. There is a growing body of evidence supporting a link between cytokines and somatic complaints. This review discusses alterations of cytokines in fibromyalgia, including increased serum levels of interleukin (IL)-2, IL-2 receptor, IL-8, IL-1 receptor antagonist; increased IL-1 and IL-6 produced by stimulated peripheral blood mononuclear cell in patients with FM for longer than 2 years; increased gp130, which is a neutrophil cytokine transducing protein; increased soluble IL-6 receptor and soluble IL-1 receptor antagonist only in patients with fibromyalgia who are depressed; and IL-1 beta, IL-6, and TNF-a by reverse transcriptase-polymerase chain reaction in skin biopsies of some patients with fibromyalgia. In addition, this review describes the mechanism by which alterations in cytokines in fibromyalgia and chronic hepatitis C infection can produce hyperalgesia and other neurally mediated symptoms through the presence of cytokine receptors on glial cells and opiate receptors on lymphocytes and the influence of cytokines on the hypothalamus-pituitary-adrenal axis such as IL-1, IL-6, and TNF-a activating and IL-2 and IFN-a down-regulating the HPA axis, respectively. The association between chronic hepatitis C infection and fibromyalgia is discussed, including a description of key cytokine changes in chronic hepatitis C infection. Future studies are encouraged to further characterize these immunologic alterations with potential pathophysiologic and therapeutic implications.
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Affiliation(s)
- Mollie E Thompson
- Division of Arthritis and Rheumatic Diseases, Oregon Health & Science University, 3181 Sam Jackson Park Road OP-09, Portland, OR 97239, USA.
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31
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Blindenbacher A, Duong FHT, Hunziker L, Stutvoet STD, Wang X, Terracciano L, Moradpour D, Blum HE, Alonzi T, Tripodi M, La Monica N, Heim MH. Expression of hepatitis c virus proteins inhibits interferon alpha signaling in the liver of transgenic mice. Gastroenterology 2003; 124:1465-75. [PMID: 12730885 DOI: 10.1016/s0016-5085(03)00290-7] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
UNLABELLED BACKGROUND & AIMS Hepatitis C virus (HCV) is a major cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma worldwide. The majority of patients treated with interferon alpha do not have a sustained response with clearance of the virus. The molecular mechanisms underlying interferon resistance are poorly understood. Interferon-induced activation of the Jak-STAT (signal transducer and activator of transcription) signal transduction pathway is essential for the induction of an antiviral state. Interference of viral proteins with the Jak-STAT pathway could be responsible for interferon resistance in patients with chronic HCV. METHODS We have analyzed interferon-induced signal transduction through the Jak-STAT pathway in transgenic mice that express HCV proteins in their liver cells. STAT activation was investigated with Western blots, immunofluorescence, and electrophoretic mobility shift assays. Virus challenge experiments with lymphocytic choriomeningitis virus were used to demonstrate the functional importance of Jak-STAT inhibition. RESULTS STAT signaling was found to be strongly inhibited in liver cells of HCV transgenic mice. The inhibition occurred in the nucleus and blocked binding of STAT transcription factors to the promoters of interferon-stimulated genes. Tyrosine phosphorylation of STAT proteins by Janus kinases at the interferon receptor was not inhibited. This lack in interferon response resulted in an enhanced susceptibility of the transgenic mice to infection with a hepatotropic strain of lymphocytic choriomeningitis virus. CONCLUSIONS Interferon-induced intracellular signaling is impaired in HCV transgenic mice. Interference of HCV proteins with interferon-induced intracellular signaling could be an important mechanism of viral persistence and treatment resistance.
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Ben-Ari Z, Mor E, Papo O, Kfir B, Sulkes J, Tambur AR, Tur-Kaspa R, Klein T. Cytokine gene polymorphisms in patients infected with hepatitis B virus. Am J Gastroenterol 2003; 98:144-50. [PMID: 12526950 DOI: 10.1111/j.1572-0241.2003.07179.x] [Citation(s) in RCA: 188] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Cytokines play a key role in the regulation of the immune response. The maximal capacity of cytokine production varies among individuals and correlates with the polymorphism in the cytokine gene promoters. The aim of this study was to characterize gene polymorphism in patients with chronic hepatitis B virus (HBV) infection and to determine the different patterns in patient subgroups. METHODS The study population consisted of 77 patients with chronic HBV infection (23 low-level HBV replicative carriers, 23 compensated high-level HBV replicative carriers, 21 decompensated liver transplant candidates, and 10 patients with documented hepatocellular carcinoma). The genetic profile of five cytokines was analyzed by polymerase chain reaction-sequence-specific primer (SSP), and subjects were genotyped as high or low producers of tumor necrosis factor-alpha and interleukin (IL)-6, and as high, intermediate, or low producers of transforming growth factor-beta(1), interferon (IFN)-gamma, and IL-10 based on single nucleotide substitutions. The control group included 10 healthy individuals who recovered from HBV infection and 48 healthy controls. RESULTS A highly statistically significant difference in the distribution of the IFN-gamma gene polymorphism (at position +879) was observed between patients with chronic HBV infection and controls. The majority of the patients (65.2%) exhibited the potential to produce low levels of IFN-gamma (A/A genotype) compared with 37.5% of the control group (p = 0.003). Healthy individuals who recovered from HBV infection had a similar distribution of IFN-gamma gene polymorphism as the healthy controls. No statistically significant difference in IFN-gamma production was found between patients with low- and high-level HBV replication and between compensated and decompensated patients. There was also no statistically significant difference in the genetic ability to produce tumor necrosis factor-alpha (at position -308), IL-6 (at position -174), IL-10 (at position -1082, -819, and -592), and transforming growth factor-beta(1) (at position +10 and +25). CONCLUSION These findings suggest an association between the genetic ability to produce low levels of IFN-gamma and the susceptibility to develop chronic HBV infection.
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Affiliation(s)
- Ziv Ben-Ari
- The Liver Institute, Department of Medicine D, Rabin Medical Center, Beilinson Campus, Petah Tikva, Israel
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Means RE, Choi JK, Nakamura H, Chung YH, Ishido S, Jung JU. Immune evasion strategies of Kaposi's sarcoma-associated herpesvirus. Curr Top Microbiol Immunol 2002; 269:187-201. [PMID: 12224509 DOI: 10.1007/978-3-642-59421-2_12] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
To establish lifelong infection in the presence of an active host immune system, herpesviruses have acquired an impressive array of immune modulatory mechanisms that contribute to their success as long-term parasites. Kaposi's sarcoma-associated herpesvirus (KSHV) is the most recently discovered human tumor virus and is associated with the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. KSHV has acquired a battery of genes to assist in viral survival against the host immune response. These viral gene products target a variety of host immune surveillance mechanisms, including the cytokine-mediated immune response, apoptosis, natural killer (NK) cell killing and T cell-mediated responses. This review summarizes our understanding of the role of these viral proteins in the escape from host immune surveillance, which ultimately contributes to lifelong infection and pathogenesis of KSHV.
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Affiliation(s)
- R E Means
- Department of Microbiology and Molecular Genetics, Tumor Virology Division, New England Regional Primate Research Center, Harvard Medical School, 1 Pine Hill Drive, Southborough, MA 01772, USA
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Gotoh B, Komatsu T, Takeuchi K, Yokoo J. Paramyxovirus strategies for evading the interferon response. Rev Med Virol 2002; 12:337-57. [PMID: 12410527 DOI: 10.1002/rmv.357] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Two genera, the Respirovirus (Sendai virus (SeV) and human parainfluenza virus (hPIV3) and the Rubulavirus (simian virus (SV) 5, SV41, mumps virus and hPIV2), of the three in the subfamily Paramyxovirinae inhibit interferon (IFN) signalling to circumvent the IFN response. The viral protein responsible for the inhibition is the C protein for respirovirus SeV and the V protein for the rubulaviruses, both of which are multifunctional accessory proteins expressed from the P gene. SeV suppresses IFN-stimulated tyrosine phosphorylation of signal transducers and activators of transcription (STATs) at an early phase of infection and further inhibits the downstream signalling without degrading any of the signalling components in most cell lines. On the contrary, the Rubulavirus V protein targets Stat1 or Stat2 for degradation. Proteasome-mediated degradation appears to be involved in most cases. Studies on the molecular mechanisms by which paramyxoviruses evade the IFN response will offer important information for modulating the JAK-STAT pathway, designing novel antiviral drugs and recombinant live vaccines, and improving paramyxovirus expression vectors for gene therapy.
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Affiliation(s)
- Bin Gotoh
- Department of Microbiology, Fukui Medical University School of Medicine, Shimoaizuki 23-3, Matsuoka-cho, Yoshida-gun, Fukui 910-1193, Japan.
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He Y, Katze MG. To interfere and to anti-interfere: the interplay between hepatitis C virus and interferon. Viral Immunol 2002; 15:95-119. [PMID: 11952150 DOI: 10.1089/088282402317340260] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
As popular strategies used by numerous viruses, interception of interferon (IFN) signaling and inhibition of IFN-induced antiviral functions allow viruses to evade the host immune response and set up successful infections. Hepatitis C virus (HCV), the leading cause of chronic liver disease worldwide and a major public health hazard, causes persistent infection in the majority of infected individuals. IFN-based therapies, currently the only ones available for HCV infection, have been unable to eliminate viral infection in the majority of patients, and many studies suggest that HCV possesses mechanisms to antagonize the IFN-induced antiviral response. Multiple viral, host, and IFN-associated factors have been implicated in the interplay between HCV and IFN. Two viral proteins, NS5A and E2, became the focus of much attention and extensive study because of their abilities to inhibit IFN-induced, double-stranded RNA-activated protein kinase (PKR), a major mediator of the IFN-induced biologic response, and to perturb the IFN signaling pathway. In this review, we discuss the significance of the interferon sensitivity determining region (ISDR) within NS5A, which has been the subject of intense debates. In addition, we discuss the potential mechanisms by which NS5A interferes with IFN signaling and the current working models. Further understanding of the molecular mechanisms underlying the interaction between HCV and IFN will likely facilitate improvement of current IFN-based therapies and development of novel treatments for the HCV pandemic. Future HCV research will benefit from both the development of efficient, convenient model systems for viral propagation, and the utilization of high throughput, genomic-scale approaches.
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Affiliation(s)
- Yupeng He
- Department of Microbiology, School of Medicine, University of Washington, 98195, USA
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37
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García-Sastre A. Mechanisms of inhibition of the host interferon alpha/beta-mediated antiviral responses by viruses. Microbes Infect 2002; 4:647-55. [PMID: 12048034 DOI: 10.1016/s1286-4579(02)01583-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Complex multicellular organisms have evolved sophisticated mechanisms to prevent and control infection by pathogens. Among these mechanisms, the type I interferon or interferon alpha/beta system represents one of the first lines of defense against viral infections. Typically, viral infection induces the synthesis and secretion of interferon alpha/beta by the infected cell, which in turn activates signaling pathways leading to an antiviral state. As a counter measure, many viruses have developed intriguing mechanisms to evade the interferon alpha/beta system of the host. In this review, we will summarize recent research developments in this interesting field of virus-host cell interactions.
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Affiliation(s)
- Adolfo García-Sastre
- Department of Microbiology, Box 1124, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, USA.
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Miller DM, Cebulla CM, Sedmak DD. Human cytomegalovirus inhibition of major histocompatibility complex transcription and interferon signal transduction. Curr Top Microbiol Immunol 2002; 269:153-70. [PMID: 12224507 DOI: 10.1007/978-3-642-59421-2_10] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Pathogens have evolved diverse mechanisms for escaping host innate and adaptive immunity. Viruses that maintain a persistent infection are particularly effective at disabling key arms of the host immune response. For example, the herpesviruses establish a persistent infection in human and animal hosts, in part through critical immunoevasive strategies. Cytomegalovirus, a beta-herpesvirus, impairs major histocompatibility complex (MHC) class I and class II antigen presentation by decreasing MHC expression on the surface of the infected cell, thus enabling infected cells to escape CD8+ and CD4+ T lymphocyte immunosurveillance. Moreover, cytomegalovirus blocks the interferon signal transduction pathway, thereby limiting the direct and indirect antiviral effects of the interferons. In this review, we focus on an emerging paradigm in which the effectiveness of viruses, particularly human cytomegalovirus, to escape antiviral immune responses is significantly enhanced by their ability to inhibit MHC transcription and interferon (IFN)-stimulated (JAK/STAT) signal transduction.
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Affiliation(s)
- D M Miller
- Department of Pathology, Ohio State University College of Medicine, 1645 Neil Avenue, Room 129, Columbus, OH 43210, USA
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Tan SL, Katze MG. How hepatitis C virus counteracts the interferon response: the jury is still out on NS5A. Virology 2001; 284:1-12. [PMID: 11352662 DOI: 10.1006/viro.2001.0885] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Interferons (IFNs) induce an antiviral state in the cell through complex and indirect mechanisms, which culminate in a direct inhibition of viral replication and stimulation of the host adaptive responses. Viruses often counteract with elaborate strategies to interfere with the induction as well as action of IFN effector molecules. This evolutionary battle between viruses and IFN components is a subject of intense research aimed at understanding the immunopathogenesis of viruses and the molecular basis of IFN signaling and action. In the case with hepatitis C virus (HCV), this may have profound implications for the therapeutic use of recombinant IFN in treating chronic hepatitis C. Depending on the subtype of HCV, current IFN-based treatment regimens are effective for only a small subset of chronic hepatitis C patients. Thus, one of the Holy Grails in HCV research is to understand the mechanisms by which the virus may evade IFN antiviral surveillance and establish persistent infection, which may eventually provide insights into new avenues for better antiviral therapy. Despite the lack of an efficient tissue culture system and an appropriate animal model for HCV infection, several mechanisms have been proposed based on clinical studies and in vitro experiments. This minireview focuses on the HCV NS5A nonstructural protein, which is implicated in playing a role in HCV tolerance to IFN treatment, possibly in part through its ability to inhibit the cellular IFN-induced PKR protein kinase.
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Affiliation(s)
- S L Tan
- Infectious Diseases Research, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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40
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Protzer U, Schaller H. Immune escape by hepatitis B viruses. Virus Genes 2001; 21:27-37. [PMID: 11022787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Hepatitis B viruses are DNA viruses characterized by their very small genome size and their unique replication via reverse transcription. The circular genome has been efficiently exploited, thereby limiting genome variation, and leaves no space for genes in addition to those essentially needed during the viral live cycle. Hepatitis B viruses are prototype non-cytopathic viruses causing persistent infection. Human hepatitis B virus (HBV), as well as the closely related animal viruses, most frequently are transmitted vertically from mothers to their offspring. Because infection usually persists for many years, if not lifelong, hepatitis B viruses need efficient mechanisms to hide from the immune response of the host. To escape the immune response, they exploit different strategies. Firstly, they use their structural and non-structural proteins multiplely. One of the purposes is to alter the immune response. Secondly, they replicate by establishing a pool of stable extrachromosomal transcription templates, which allow the virus to react sensitively to changes in its microenvironment by up- or downregulating gene expression. Thirdly, hepatitis B viruses replicate in the liver which is an immunopriviledged site.
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Affiliation(s)
- U Protzer
- Zentrum für Molekulare Biologie (ZMBH), University of Heidelberg. Germany
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41
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Choi J, Means RE, Damania B, Jung JU. Molecular piracy of Kaposi's sarcoma associated herpesvirus. Cytokine Growth Factor Rev 2001; 12:245-57. [PMID: 11325605 DOI: 10.1016/s1359-6101(00)00029-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Kaposi's Sarcoma associated Herpesvirus (KSHV) is the most recently discovered human tumor virus and is associated with the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and Multicentric Casttleman's disease. KSHV contains numerous open reading frames with striking homology to cellular genes. These viral gene products play a variety of roles in KSHV-associated pathogenesis by disrupting cellular signal transduction pathways, which include interferon-mediated anti-viral responses, cytokine-regulated cell growth, apoptosis, and cell cycle control. In this review, we will attempt to cover our understanding of how viral proteins deregulate cellular signaling pathways, which ultimately contribute to the conversion of normal cells to cancerous cells.
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Affiliation(s)
- J Choi
- Department of Microbiology and Molecular Genetics, Tumor Virology Division, New England Regional Primate Research Center, Harvard Medical School, 1 Pine Hill Drive, Southborough, MA 01772, USA
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Cho EW, Park JH, Yoo OJ, Kim KL. Translocation and accumulation of exogeneous hepatitis B virus preS surface proteins in the cell nucleus. J Cell Sci 2001; 114:1115-23. [PMID: 11228155 DOI: 10.1242/jcs.114.6.1115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Recurrent reports about protease-sensitive sites in the junction of the preS and S region of the hepatitis B virus large surface protein have raised the question about a possible biological role of S protein-depleted, independent preS protein fragments in the virus life cycle. In the present study, this question was addressed by exogenous introduction of fluorescence-labeled recombinant preS proteins into permeabilized HepG2 cells. While maltose-binding proteins (MBP) were evenly distributed throughout the cytoplasm, MBP-preS fusion proteins selectively accumulated in the nucleus. Using truncated preS proteins, the effective domain for this nuclear accumulation was localized around the preS2 region. The mode of this action differs from conventional nuclear translocation mechanism in its energy- and mediator-independency and in that it is not saturated regardless of the increase of preS protein concentration. The biological meaning of this phenomenon has to be further studied. However, in regard to hepatitis B virus infection, this observation might provide a clue for unveiling the still poorly characterized events after initial internalization of the virus, which might make use of the nuclear translocation effect of the preS2 region to facilitate the infection.
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Affiliation(s)
- E W Cho
- Protein Research Laboratory, Korea Research Institute of Bioscience and Biotechnology, Yusong, P.O. Box 115, Taejon 305-600, South Korea
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43
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Gordien E, Rosmorduc O, Peltekian C, Garreau F, Bréchot C, Kremsdorf D. Inhibition of hepatitis B virus replication by the interferon-inducible MxA protein. J Virol 2001; 75:2684-91. [PMID: 11222692 PMCID: PMC115893 DOI: 10.1128/jvi.75.6.2684-2691.2001] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Human MxA is an alpha/beta interferon-inducible intracytoplasmic protein that mediates antiviral activity against several RNA viruses. We had previously shown that overexpression of the hepatitis B virus (HBV) capsid led to selective downregulation of MxA gene expression, suggesting a mechanism by which the virus escapes from the host defense system (O. Rosmorduc, H. Sirma, P. Soussan, E. Gordien, P. Lebon, M. Horisberger, C. Brechot and D. Kremsdorf, J. Gen. Virol. 80:1253-1262, 1999). In the present study, we investigated the antiviral activity of MxA protein against HBV. MxA-expressing HuH7 clones were established and transiently transfected with HBV, and viral replication was then studied. Viral protein secretion was profoundly reduced in MxA-expressing clones by 80% for HBV surface antigen (HBsAg) and 70% for HBV e antigen (HBeAg). The levels of intracytoplasmic HBsAg and HBeAg were reduced by about 80 and 50% in the two MxA-positive clones tested. A nearly complete disappearance of HBV DNA replicative intermediates was observed in MxA-expressing clones. Although the expression of total viral RNAs was not modified, two- to fourfold reductions in HBV cytoplasmic RNAs were found in MxA-expressing clones. This suggests the inhibition of HBV replication at a posttranscriptional level. Indeed, using the well-characterized posttranscriptional regulation element (PRE) reporter system, we were able to demonstrate a marked reduction (three- to eightfold) in the nucleocytoplasmic export of unspliced RNA in MxA-expressing clones. In addition, MxA protein did not interact with HBV nucleocapsid or interfere with HBV nucleocapsid formation. Our results show an antiviral effect of MxA protein on a DNA virus for the first time. MxA protein acts, at least in part, by inhibiting the nucleocytoplasmic export of viral mRNA via the PRE sequence.
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Affiliation(s)
- E Gordien
- INSERM U370, Institut Necker, Paris, France
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Miller DM, Cebulla CM, Rahill BM, Sedmak DD. Cytomegalovirus and transcriptional down-regulation of major histocompatibility complex class II expression. Semin Immunol 2001; 13:11-8. [PMID: 11289795 DOI: 10.1006/smim.2001.0291] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
CD4(+)T lymphocytes are a significant component of the afferent and efferent arms of adaptive immunity and are critical for controlling viral infections. CD4(+)T lymphocytes secrete cytokines that augment CD8(+)T lymphocyte and B lymphocyte responses and directly inhibit viral replication. The interface between the CD4(+)T lymphocyte and virus is the major histocompatibility complex (MHC) class II molecule. Cytomegalovirus, a beta-herpesvirus, has evolved mechanisms for inhibiting MHC class II expression and thus escaping CD4(+)T lymphocyte immunosurveillance. Herein, we review cytomegalovirus-mediated down-regulation of inducible and constitutive MHC class II expression, while focusing on lesions that occur at the level of MHC class II transcription.
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Affiliation(s)
- D M Miller
- Department of Pathology, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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Ichikawa T, Nakao K, Nakata K, Hamasaki K, Takeda Y, Kajiya Y, Higashi S, Ohkubo K, Kato Y, Ishii N, Eguchi K. Geranylgeranylacetone induces antiviral gene expression in human hepatoma cells. Biochem Biophys Res Commun 2001; 280:933-9. [PMID: 11162614 DOI: 10.1006/bbrc.2000.4228] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Geranylgeranylacetone (GGA), an isoprenoid compound, is used clinically as an anti-ulcer drug. Since some isoprenoids including retinoids have anti-tumor and anti-viral activities in a variety of cell types, we investigated whether GGA could induce anti-viral proteins in human hepatoma cells. The HuH-7 and HepG2 cells were treated with GGA, and expression of anti-viral proteins such as 2'5'-oligoadenylate synthetase (2'5'-OAS) and double-stranded RNA-dependent protein kinase (PKR) in these cells was analyzed. GGA stimulated 2'5'-OAS and PKR gene expression at the transcriptional level through the formation of interferon-stimulated gene factor 3 (ISGF3), which regulates both gene transcription. By Western blotting, GGA induced expression of signal transducers and activators of transcription 1, 2 (STAT1, STAT2) and p48 proteins, components of ISGF3, together with the phosphorylation of STAT1. These results suggest that GGA acts as a potent inducer of anti-viral gene expression by stimulating the ISGF3 formation in human hepatoma cells.
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Affiliation(s)
- T Ichikawa
- The First Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki, Japan
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Abstract
Hepatitis B viruses are DNA viruses characterized by their very small genome size and their unique replication via reverse transcription. The circular genome has been efficiently exploited, thereby limiting genome variation, and leaves no space for genes in addition to those essentially needed during the viral live cycle. Hepatitis B viruses are prototype non-cytopathic viruses causing persistent infection. Human hepatitis B virus (HBV), as well as the closely related animal viruses, most frequently are transmitted vertically from mothers to their offspring. Because infection usually persists for many years, if not lifelong, hepatitis B viruses need efficient mechanisms to hide from the immune response of the host. To escape the immune response, they exploit different strategies. Firstly, they use their structural and non-structural proteins multiplely. One of the purposes is to alter the immune response. Secondly, they replicate by establishing a pool of stable extrachromosomal transcription templates, which allow the virus to react sensitively to changes in its microenvironment by up- or downregulating gene expression. Thirdly, hepatitis B viruses replicate in the liver which is an immunopriviledged site.
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Heim MH, Moradpour D, Blum HE. Expression of hepatitis C virus proteins inhibits signal transduction through the Jak-STAT pathway. J Virol 1999; 73:8469-75. [PMID: 10482599 PMCID: PMC112866 DOI: 10.1128/jvi.73.10.8469-8475.1999] [Citation(s) in RCA: 214] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Hepatitis C virus (HCV) infection is a leading cause of liver disease worldwide. Alpha interferon (IFN-alpha) therapy of chronic hepatitis C leads to a sustained response in 10 to 20% of patients only. The mechanisms of viral persistence and the pathogenesis of hepatitis C are poorly understood. We established continuous human cell lines, allowing the tightly regulated expression of the entire HCV open reading frame under the control of a tetracycline-responsive promoter. Using this in vitro system, we analyzed the effect of HCV proteins on IFN-induced intracellular signaling. Expression of HCV proteins in these cells strongly inhibited IFN-alpha-induced signal transduction through the Jak-STAT pathway. Inhibition occurred downstream of STAT tyrosine phosphorylation. Inhibition of the Jak-STAT pathway was not restricted to IFN-alpha-induced signaling but was observed in leukemia inhibitory factor-induced signaling through Stat3 as well. By contrast, tumor necrosis factor alpha-induced activation of the transcription factor NF-kappaB was not affected. Interference of HCV with IFN-alpha-induced signaling through the Jak-STAT pathway could contribute to the resistance to IFN-alpha therapy observed in the majority of patients and may represent a general escape strategy of HCV contributing to viral persistence and pathogenesis of chronic liver disease.
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Affiliation(s)
- M H Heim
- Department of Research, University Hospital Basel, CH-4031 Basel, Switzerland
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Castelruiz Y, Larrea E, Boya P, Civeira MP, Prieto J. Interferon alfa subtypes and levels of type I interferons in the liver and peripheral mononuclear cells in patients with chronic hepatitis C and controls. Hepatology 1999; 29:1900-4. [PMID: 10347136 DOI: 10.1002/hep.510290625] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Viral infections stimulate the transcription of interferon type I, which includes IFN-alfa (IFN-alpha) (13 subtypes) and IFN-beta (a single substance). Hepatitis C virus (HCV) infection is remarkable by its ability to evade host antiviral defenses; however, there is little information as to whether endogenous IFN is activated or not in this disease. Additionally, despite the fact that the various IFN-alpha subtypes may differ in biological activity, there are no data concerning the IFN-alpha subtypes specifically expressed in normal and diseased liver tissue. Thus, we have analyzed the IFN-alpha subtypes and the mRNA levels of type I IFNs in samples of normal liver tissue and in liver from patients with chronic hepatitis C. Similar studies were performed in peripheral blood mononuclear cells (PBMC) from patients and controls. After amplification and cloning of IFN-alpha cDNA, we observed that 98 of the 100 clones from normal liver tissue corresponded to the IFN-alpha5 subtype. However, in livers with chronic hepatitis C and in PBMC from controls and patients, a variety of subtypes, in addition to IFN-alpha5, were detected, suggesting a participation of infiltrating leukocytes in the production of IFN-alpha in livers with chronic hepatitis C. As compared with controls, patients with chronic hepatitis C showed a significant increase in IFN-beta mRNA in both the liver and PBMC, while IFN-alpha mRNA was significantly increased in PBMC but markedly reduced in liver tissue. In conclusion, IFN-alpha5 is the sole IFN-alpha subtype expressed in normal liver tissue. The hepatic levels of IFN-alpha are reduced in chronic hepatitis C, an event that may favor viral persistence.
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Affiliation(s)
- Y Castelruiz
- Department of Medicine and Liver Unit, Clinica Universitaria, University of Navarra, Pamplona, Spain
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Affiliation(s)
- W Rosenberg
- University Department of Medicine, Level D, South Block (Mailpoint 811), Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK
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50
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Hung WC, Chuang LY. Sodium butyrate enhances STAT 1 expression in PLC/PRF/5 hepatoma cells and augments their responsiveness to interferon-alpha. Br J Cancer 1999; 80:705-10. [PMID: 10360647 PMCID: PMC2362280 DOI: 10.1038/sj.bjc.6690413] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although interferon-alpha (IFN-alpha) has shown great promise in the treatment of chronic viral hepatitis, the anti-tumour effect of this agent in the therapy of liver cancer is unclear. Recent studies have demonstrated that differentiation-inducing agents could modulate the responsiveness of cancer cells to IFN-alpha by regulating the expression of signal transducers and activators of transcription (STAT) proteins, a group of transcription factors which play important roles in the IFN signalling pathway. We have reported that sodium butyrate is a potent differentiation inducer for human hepatoma cells. In this study, we investigated whether this drug could regulate the expression of STAT proteins and enhance the anti-tumour effect of IFN-alpha in hepatoma cells. We found that sodium butyrate specifically activated STAT1 gene expression and enhanced IFN-alpha-induced phosphorylation and activation of STAT1 proteins. Co-treatment with these two drugs led to G1 growth arrest, accompanied by down-regulation of cyclin D1 and up-regulation of p21WAF-1, and accumulation of hypophosphorylated retinoblastoma protein in hepatoma cells. Additionally, internucleosomal DNA fragmentation, a biological hallmark of apoptosis, was detected in hepatoma cells after continuous incubation with a combination of these two drugs for 72 h. Our results show that sodium butyrate potently enhances the anti-tumour effect of IFN-alpha in vitro and suggest that a rational combination of these two drugs may be useful for the treatment of liver cancer.
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Affiliation(s)
- W C Hung
- School of Technology for Medical Sciences, Kaohsiung Medical College, Taiwan, Republic of China
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