Human immune response to Hepatitis C

virus

Geert Leroux-RoelsCenter 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

B cell

Hepatocyte

CD8+

CTL CD4+Th cell

YY

Y

YY

APCNK

NKTcells

The human immune response

Study of the immune response

•Patient studies

•Animal models

Acute infectionSpontaneous

clearance

Chronic infection

20%

80%

Treatment

Chronic hepatitis

No response

Sustained response

Patient Studies

Patient studies

Liver infiltrating lymphocytes

PBMC

- fresh- cultured

Liver infiltrating lymphocytes

- 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

CD4+Th cell

CD8+

CTL

TNF-IFN-

Lysis

IFN-

Hepatocyte

APC

YY

B cellY-E1-E2

-NS3

Kinetics of anti-HCV response in patients with transfusion-associated hepatitis C and resolution of infection

Chen et al. Gastroenterology 1999;116:135-143

Kinetics of anti-HCV response in patients with transfusion-associated 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 chimpanzee- infectious HCV with antibody

• directed against HVR1 and other regions of E2

Neutralisation of binding -NOB assay

CD81 MOLT 4 CD81

HVR1

E2

E1

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

Gerlach et al. Gastroenterology 1999;117:933-941

Proliferative CD4+ T-cell response in the acute phase of disease to recombinant HCV proteins in 38 patients with acute HCV infection

Immune response during acute and chronic HCV infections

Type ofresponse

Acute/ Self-limiting

Chronic HCV

PBMC PBMC Liver

B cell(Ab)

Low titered,against fewproteins

High titered,against mostproteins

CD4 Early, multi-specific

Low, pauci-specific

Present,pauci-specific

CD8 Early, multi-specific

Low, pauci-specific

Present,pauci-specific

Correlate of protection and disease

progression ?

B cell

CD8+

CTL HepatocyteCD4+

Th cell

YY

Y

YY

NK

NKTcells

Immune response to HCV infection :

Role largely unknown

- early, vigorous, multi- specific response- strong NS3-response in resolving acute HCV- TH1 in recovery- TH2 in chronic

- vigorous, multi- specific response- CTL exert some control on viral load

antibodies to most structural and non-structural viral proteins are made

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

CD81

CD81

NK cell (in vitro)HCV

Binding of HCV E2 proteinto CD81 on NK cell causesinhibition of - cytolytic activity- IFN- production

Crotta et al. JEM 2002;195:35-41Tseng et al. JEM 2002;195:43-49

E2

E1

Effect of HCV on NK cell function

Natural cytotoxicity and antibody-dependentcytotoxicity (ADCC) is not impaired in patientssuffering 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

cellsand dendritic cell function

• inappropriate cytokine profile of TH

• lack or low frequency of neutralizing antibodies

Liver 2x1011 hepatocytes

Kidney Pancreas

Spleen &Lymphoid tissue

B lymphocyteMonocyte

Dendritic cell

Liver and extra-hepatic infection sites

BDEC

?

Janeway-Immunobiology

Dendritic cell precursor - Monocyte

IL-4 + GM-CSF

LPS/TNF

Dendritic cell maturation

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 andpercentages of CD4+/CD25+ cellsin response to HCVcore or TT antigensin 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 Pathway1 ,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

• 6 major genotypes• more than 50

subtypes• Quasispecies

5’UT C E1 E2 p7 NS2 NS4BNS3 NS5A NS5B 3’

Hypervariable region - HVR1

384 410 cross-reactivity (%)

R9 QTTVVGGSQSHTVRGLTSLFSPGASQN 60 F78 QTHTTGGGAGHQAHSLTGLFSPGAKQN 70M122 QTTTTGGSAHAVSSLTGLFSPGSKQN 44G31 TTHTVGGSVARQVHSLTGLFSPGPQQK 77H1 QTHTTGGVVGHATSGLTSLFSPGPSQK 42D6 QTTTTGGQVSHATHGLTGLFSLGPQQK 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 PKRinactive

Initiation FactoreIF-2

PhosphorylatedInitiation FactoreIF-2P

Phosphatase(soluble)

Pi

mRNA translation inhibition

Protein Kinase PKRactive

dsRNAssRNA

HCV E1 HCV NS5A

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.