Molecular Mimicry of Human Cytochrome P450 by Hepatitis C Virus at the Level of Cytotoxic T Cell Recognition

Kammer, Andreas R.; van der Burg, Sjoerd H.; Grabscheid, Benno; Hunziker, Isabelle P.; Kwappenberg, Kitty M.C.; Reichen, Jürg; Melief, Cornelis J.M.; Cerny, Andreas

Induction of Primary CTLs. To determine the effect of the different HLA-A2 binding properties on T cell activation and antigen recognition by CTLs, we first analyzed the naive CTL repertoire in healthy blood donors. PBMCs from 12 healthy HCV-seronegative, HLA-A2-positive blood donors were stimulated with synthetic HCV core 178-187, CYP2A6 8-17, or CYP2A7 8-17 peptide in four replica cultures. After 5 wk, the cultures were tested for CTL activity against target cells presenting each of the three peptides. Long-term stimulation with the HCV core 178 peptide induced HCV core 178-specific CTLs in nine HCV-seronegative blood donors (Table II) . In five individuals, the HCV core 178-specific CTLs not only recognized the inducing HCV peptide but also CYP2A6 and/or CYP2A7 self-peptides. A higher specific lysis of targets presenting CYP2A7 was observed in most cases. Two donors recognized all three peptides, three individuals recognized HCV core 178 and CYP2A7 8-17, four recognized HCV core 178 only, and three did not show a CTL response after stimulation with HCV core 178. Representative results of three donors are shown in Fig. 2 a. These results as well as data obtained from CTL lines derived from positive cultures (data not shown) indicate the presence of three phenotypes of HCV core 178-specific CTLs: CTLs recognizing HCV core 178 only, CTLs cross-reactive with HCV core 178 and CYP2A7, and CTLs specific for HCV core 178, CYP2A7, and CYP2A6. We did not find CTLs recognizing CYP2A6 without recognition of CYP2A7, nor cells recognizing one of the CYP peptides without recognition of HCV core 178. Importantly, no CTL response could be induced with the self-peptides CYP2A6 8-17 (Fig. 2 b) and CYP2A7 8-17 (Fig. 2 c) in any of the 12 donors tested. This fits with our observation of different MHC-peptide interactions, because peptide-induced MHC stability and immunogenicity of the peptide are strongly correlated (28) .