Introduction to Human Immune Respose to Hepatitis C virus

Human immune response to Hepatitis C virus Geert Leroux-Roels Center for Vaccinology Ghent University and Hospital Overview of the presentation • The principal actors – Hepatitis C virus or HCV – The human immune system • Innate immune system • Adaptive immune response • Mechanisms of persistence • Consequences for vaccine development The HCV genome and expressed polyprotein Lauer et al. NEJM 345:41-52, 2001 Hepatitis C virus Envelope proteins E1 (gp31) E2 (gp70) Nucleoprotein - Core (p21) RNA genome The human immune response B cell CD8+ CTL Hepatocyte CD4+ Th cell NK APC NKT cells Study of the immune response • Patient studies • Animal models Patient Studies Acute infection 80% 20% Spontaneous clearance Chronic infection Treatment No response Sustained response Chronic hepatitis Patient studies Liver infiltrating lymphocytes - fresh - cultured PBMC - fresh - cultured Study of the immune response • Patient studies • Animal models – chimpanzee (ethics, = human) – mouse models • HLA-A2 transgenic mouse • HCV transgenic mice • huPBL-SCID mouse, Trimera mouse, huHepatocyte-uPA-SCID mouse, .. The adaptive immune response to HCV a-NS3 a-E2 a-E1 B cell Lysis CD8+ CTL TNF-a IFN-g Hepatocyte CD4+ Th cell IFN-g APC Kinetics of anti-HCV response in patients with transfusionassociated hepatitis C and resolution of infection Chen et al. Gastroenterology 1999;116:135-143 Kinetics of anti-HCV response in patients with transfusionassociated hepatitis C who develop chronic HCV Chen et al. Gastroenterology 1999;116:135-143 Target of neutralizing antibodies • Envelope proteins E1 and E2 • Protective role demonstrated by in vitro neutralization of chimpanzeeinfectious HCV with antibody • directed against HVR1 and other regions of E2 Neutralisation of binding NOB assay E1 HVR1 E2 CD81 MOLT 4 CD81 Are antibodies needed to clear HCV infection ? • Human HCV infection can resolve in agammaglobulinemic children – Bjoro et al. NEJM 1194; 331:1607-1611 – Adams et al. Ped Inf Dis J 1997;16:533-534 – Christie et al. Clin Exp Immunol 1997;110:4-8 • HCV clearance in chimp occurred in the absence of any antibody response to envelope proteins – Bassett et al. J Virol 1999;73:1118-1126 Proliferative CD4+ T-cell response in the acute phase of disease to recombinant HCV proteins in 38 patients with acute HCV infection Gerlach et al. Gastroenterology 1999;117:933-941 Immune response during acute and chronic HCV infections Acute/SelfType of limiting response PBMC Chronic HCV PBMC Liver B cell (Ab) CD4 CD8 Low titered, against few proteins Early, multispecific Early, multispecific High titered, against most proteins Low, pauci- Present, specific pauci-specific Low, paucispecific Present, pauci-specific Correlate of protection and disease progression ? Immune response to HCV infection : antibodies to most structural and non-structural viral proteins are made B cell - vigorous, multispecific response - CTL exert some control on viral load CD8+ CTL Hepatocyte CD4+ Th cell NK Role largely unknown NKT cells - early, vigorous, multispecific response - strong NS3-response in resolving acute HCV - TH1 in recovery - TH2 in chronic Potential Mechanisms of Viral Persistence • Inadequate HCV-specific IR – inadequate innate immune response – insufficient induction of adaptive IR – inability to maintain the adaptive IR • Viral evasion mechanisms Potential Mechanisms of Viral Persistence • Inadequate HCV-specific IR – inadequate innate immune response • NK Cell function • Dendritic cell function – insufficient induction of adaptive IR – inability to maintain the adaptive IR Effect of HCV on NK cell function HCV E1 E2 CD81 NK cell (in vitro) Binding of HCV E2 protein to CD81 on NK cell causes inhibition of - cytolytic activity - IFN-g production Crotta et al. JEM 2002;195:35-41 Tseng et al. JEM 2002;195:43-49 CD81 Effect of HCV on NK cell function Natural cytotoxicity and antibody-dependent cytotoxicity (ADCC) is not impaired in patients suffering from chronic hepatitis C Düesberg U, Schneiders A, Flieger D, Inchauspé G, Sauerbruch T, Spengler U. J Hepatol 2001;35:650-657 Potential Mechanisms of Viral Persistence • Inadequate HCV-specific IR – insufficient induction of adaptive IR • low level of viral antigen expression • virus infection of antigen-presenting cells and dendritic cell function • inappropriate cytokine profile of TH • lack or low frequency of neutralizing antibodies Liver and extra-hepatic infection sites Liver 2x1011 hepatocytes Spleen & Lymphoid tissue B lymphocyte Monocyte Dendritic cell BDEC ? Kidney Pancreas Dendritic cell maturation Dendritic cell precursor - Monocyte IL-4 + GM-CSF LPS/TNFa Janeway-Immunobiology Reduced capacity of mature DC from HCV patients to induce allogeneic T cell proliferation. Bain et al. Gastroenterology 120:51-524, 2001 IL-2 production and percentages of CD4+/CD25+ cells in response to HCV core or TT antigens in HCV patients Sarobe et al. J.Virol 76:5062-5070, 2002 Potential Mechanisms of Viral Persistence • Inadequate HCV-specific IR – inadequate innate immune response – insufficient induction of adaptive IR – inability to maintain the adaptive IR • Viral evasion mechanisms Potential Mechanisms of Viral Persistence • Viral evasion mechanisms – replication in immune privileged sites – viral interference with antigen processing – viral suppression of host immune response – viral sequence variation – viral insusceptibility to cytokine mediated inhibition of replication and gene expression Potential Mechanisms of Viral Persistence • Viral evasion mechanisms – replication in immune privileged sites – viral interference with antigen processing – viral suppression of host immune response – viral sequence variation – viral insusceptibility to cytokine mediated inhibition of replication and gene expression HCV core controversy The Journal of Immunology, 2001, 167: 5264-5272. Hepatitis C Virus Core Protein Inhibits Human T Lymphocyte Responses by a Complement-Dependent Regulatory Pathway 1 ,2 Zhi Qiang Yao, Duong Tony Nguyen, Apostolos I. Hiotellis and Young S. Hahn3 Journal of Virology, February 2002, p. 990-997, Vol. 76, No. 3 Hepatitis C Virus Genotype 1b Core Protein Does Not Exert Immunomodulatory Effects on Virus-Induced Cellular Immunity Zhang-Xu Liu,1 Hiroshi Nishida,1 Jian-Wen He,1,2 Michael M. C. Lai,1,2 Ni Feng,1 and Gunther Dennert1* Potential Mechanisms of Viral Persistence • Viral evasion mechanisms – replication in immune privileged sites – viral interference with antigen processing – viral suppression of host immune response – viral sequence variation • escape from humoral immune response • escape from cellular immune response – viral insusceptibility to cytokine ... Variability of HCV 5’UT C E1 E2 p7 NS2 NS3 NS4B NS5A NS5B 3’ Hypervariable region - HVR1 384 • 6 major genotypes • more than 50 subtypes • Quasispecies 410 cross-reactivity (%) R9 QTTVVGGSQSHTVRGLTSLFSPGASQN F78 QTHTTGGGAGHQAHSLTGLFSPGAKQN M122 QTTTTGGSAHAVSSLTGLFSPGSKQN G31 TTHTVGGSVARQVHSLTGLFSPGPQQK H1 QTHTTGGVVGHATSGLTSLFSPGPSQK D6 QTTTTGGQVSHATHGLTGLFSLGPQQK 60 70 44 77 42 66 Potential Mechanisms of Viral Persistence • Viral evasion mechanisms – replication in immune privileged sites – viral interference with antigen processing – viral suppression of host immune response – viral sequence variation – viral insusceptibility to cytokine mediated inhibition of replication and gene expression Antagonism of IFN by HCV proteins IFN Protein Kinase PKR dsRNA ssRNA inactive HCV E1 HCV NS5A Phosphorylated Initiation Factor Protein Kinase PKR active Initiation Factor eIF-2a Pi eIF-2a P Phosphatase (soluble) mRNA translation inhibition Development of HCV vaccines badly needs • Better understanding of mechanisms of immune protection and clearance • Development of tissue culture system and small animal model of HCV infection Dendritic cell maturation Jacques Banchereau et al. Immunobiology of Dendritic Cells Annu. Rev. Immunol. 2000. 18:767-811.