Transcript Geen diatitel

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
CD4+
Th cell
Hepatocyte
NK
APC
NKT
cells
Study of the immune response
• Patient studies
• Animal models
Patient Studies
Acute infection
20%
Spontaneous
clearance
80%
Treatment
Chronic infection
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
Hepatocyte
CD4+
Th cell
TNF-a
IFN-g
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
HVR1
E1
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
B cell
(Ab)
CD4
CD8
Chronic HCV
PBMC
Liver
Low titered,
against few
proteins
Early, multispecific
High titered,
against most
proteins
Low, pauci- Present,
specific
pauci-specific
Early, multispecific
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
NK
Role largely
unknown
NKT
cells
CD4+
Th cell
- 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
NK cell (in vitro)
E1
CD81
E2
Binding of HCV E2 protein
to CD81 on NK cell causes
inhibition of
- cytolytic activity
- IFN-g production
CD81
Crotta et al. JEM 2002;195:35-41
Tseng et al. JEM 2002;195:43-49
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 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
5’UT
C
E1
E2
p7 NS2
Hypervariable region - HVR1
384
R9
F78
M122
G31
H1
D6
NS3
NS4B
NS5A NS5B
3’
• 6 major genotypes
• more than 50 subtypes
• Quasispecies
410
QTTVVGGSQSHTVRGLTSLFSPGASQN
QTHTTGGGAGHQAHSLTGLFSPGAKQN
QTTTTGGSAHAVSSLTGLFSPGSKQN
TTHTVGGSVARQVHSLTGLFSPGPQQK
QTHTTGGVVGHATSGLTSLFSPGPSQK
QTTTTGGQVSHATHGLTGLFSLGPQQK
cross-reactivity (%)
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
inactive
dsRNA
ssRNA
HCV E1
HCV NS5A
Protein Kinase PKR
active
Phosphorylated
Initiation Factor
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.