BACKGROUND: Hepatitis C virus (HCV)-derived lipopeptides can induce epitope-specific immune responses in lymphocytes from HCV-naive individuals. We analyzed whether such T cells generated by in vitro immunization with HCV core-derived lipopeptides exert HCV-specific cytolytic activity. METHODS: Using a sensitive flow cytometric cytotoxicity assay we characterized HCV-specific cytotoxicity in T cells generated in vitro with HCV core-derived 25-mer lipopeptides. In addition, we studied expressions of Fas ligand and perforin and interferon-gamma (IFN-gamma) secretion in HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with lipopeptide amino acid 20-44 (LP20-44). RESULTS: CD8+ T cells induced in vitro with HCV core-derived lipopeptides only infrequently exerted HCV-specific cytotoxicity, irrespective of whether antigen-coated T2 cells or autologous B lymphoblasts were used as targets. Detailed analysis of HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with LP20-44 revealed that in vitro immunization resulted in T cells that secreted IFN-gamma after antigen-specific restimulation and that upregulated expression of Fas ligand but not of perforin. CONCLUSIONS: Our data confirm at the functional level that HCV lipopeptides induce antigen-specific T lymphocytes that produce IFN-gamma but exert significant cytotoxicity in only a minority of experiments, probably because expression of cytolytic effector molecules is not enhanced in their granules. Copyright 2005 Wiley-Liss, Inc.
BACKGROUND:Hepatitis C virus (HCV)-derived lipopeptides can induce epitope-specific immune responses in lymphocytes from HCV-naive individuals. We analyzed whether such T cells generated by in vitro immunization with HCV core-derived lipopeptides exert HCV-specific cytolytic activity. METHODS: Using a sensitive flow cytometric cytotoxicity assay we characterized HCV-specific cytotoxicity in T cells generated in vitro with HCV core-derived 25-mer lipopeptides. In addition, we studied expressions of Fas ligand and perforin and interferon-gamma (IFN-gamma) secretion in HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with lipopeptide amino acid 20-44 (LP20-44). RESULTS: CD8+ T cells induced in vitro with HCV core-derived lipopeptides only infrequently exerted HCV-specific cytotoxicity, irrespective of whether antigen-coated T2 cells or autologous B lymphoblasts were used as targets. Detailed analysis of HLA-A2-HCV(core_35-44) tetramer-positive T cells generated with LP20-44 revealed that in vitro immunization resulted in T cells that secreted IFN-gamma after antigen-specific restimulation and that upregulated expression of Fas ligand but not of perforin. CONCLUSIONS: Our data confirm at the functional level that HCV lipopeptides induce antigen-specific T lymphocytes that produce IFN-gamma but exert significant cytotoxicity in only a minority of experiments, probably because expression of cytolytic effector molecules is not enhanced in their granules. Copyright 2005 Wiley-Liss, Inc.