Analysis of CD8+ T-cell-mediated inhibition of hepatitis C virus replication using a novel immunological model.
OBJECTIVE
Virus-specific CD8+ T cells are required for the control of hepatitis C virus (HCV) infection. We investigated the extent to which different effector functions of CD8+ T cells contribute to the inhibition of viral replication.


METHODS
We developed a novel immunologic model by stably transducing the HLA-A2 gene into the replicon system, matching the epitope sequence of the replicon to the sequence targeted by an HCV-specific CD8+ T-cell clone. Luciferase activity was then measured to quantitate HCV RNA replication.


RESULTS
HCV-specific CD8+ T cells strongly inhibited viral replication, through cytolytic and noncytolytic mechanisms, in a dose-dependent manner. HCV replication was almost completely inhibited at an effector-to-target ratio of 1:1 with significant cytotoxicity; however, >95% viral inhibition occurred at ratios as low as 1:100. Importantly, no cytotoxicity was observed at low effector-to-target ratios, indicating a dominant effect of noncytolytic effector functions that was confirmed by Transwell experiments. Neutralization experiments revealed that interferon gamma mediates the noncytolytic inhibition.


CONCLUSIONS
Only a very few HCV-specific CD8+ T cells are required to inhibit HCV replication; inhibition occurs primarily by noncytolytic effector functions.
Jo
Juandy
J
Department of Medicine II, University Hospital Freiburg, and Faculty of Biology, Spemann Graduate School of Biology and Medicine, Albert Ludwigs University, Freiburg, Germany.
Aichele
Ulrike
U
Kersting
Nadine
N
Klein
Rahel
R
Aichele
Peter
P
Bisse
Emmanuel
E
Sewell
Andrew K
AK
Blum
Hubert E
HE
Bartenschlager
Ralf
R
Lohmann
Volker
V
Thimme
Robert
R
D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism / Q000502:physiology* / Q000821:virology*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D018984:Epitopes, T-Lymphocyte / Q000235:genetics; D015789:HLA-A2 Antigen / Q000235:genetics / Q000378:metabolism; D016174:Hepacivirus / Q000502:physiology*; D006526:Hepatitis C / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D018448:Models, Immunological; D012093:Replicon / Q000235:genetics; D014161:Transduction, Genetic; D017361:Viral Nonstructural Proteins / Q000235:genetics; D014779:Virus Replication / Q000502:physiology*; D012324:RNA-Dependent RNA Polymerase
D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D007371:Interferon-gamma; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase