Tetramer enrichment reveals the presence of phenotypically diverse hepatitis C virus-specific CD8+ T cells in chronic infection.
Bottom Line: CD8(+) T cells with an effector memory phenotype could not expand in vitro, suggesting exhaustion of these cells.Interestingly, some of the naive-like CD8(+) T cells proliferated vigorously upon in vitro priming, whereas others did not.Indeed, naive-like CD8(+) T cells from patients with the consensus sequence in the corresponding T-cell epitope did not expand in vitro.
Affiliation: Department of Medicine II, University Hospital Freiburg, Freiburg, Germany Faculty of Biology, University of Freiburg, Freiburg, Germany.Show MeSH
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Mentions: The antigen recognition and, thus, the phenotype of HCV-specific CD8+ T cells can be affected by the presence of sequence variations in viral epitopes, as previously described (4). Thus, we analyzed bulk viral sequences corresponding to the epitopes NS31073 and NS31406 from patients with enriched detectable HCV-specific CD8+ T-cell responses (Table 1). In our cohort, all patients showed the genotype 1a consensus sequence for the NS31073 epitope, whereas most patients showed viral sequence variations for the NS31406 epitope. This was independent of the naive-like or effector memory phenotype of HCV-specific CD8+ T cells. Since we were able to expand only two out of five HCV-specific CD8+ T-cell populations with a predominantly naive-like phenotype, we next investigated whether there is a correlation between sequence variations in the corresponding viral epitope and the proliferative capacity of naive-like HCV-specific CD8+ T cells, as observed in Fig. 4B. In HCV-specific CD8+ T-cell epitopes with the genotype 1a consensus sequence, we did not observe HCV-specific CD8+ T-cell proliferation. In contrast, in the two patients where we found in vitro expansion of naive-like HCV-specific CD8+ T cells, viral sequence variations in the corresponding CD8+ T-cell epitopes were detectable (Table 2). These results suggest that the sequence variations may not have developed during chronic infection (viral escape) but may have already been present in the infecting virus. To confirm this point, we analyzed the effect of the viral sequence variations on HCV-specific CD8+ T-cell priming. Patient 6 showed a high frequency of naive-like NS31406-specific CD8+ T cells and sequence variation in the NS31406 epitope. We pulsed MD-DCs from this patient with the consensus as well as the autologous variant sequence of NS31406 and used these sequences to stimulate the naive-like HCV-specific CD8+ T cells. Importantly, proliferation of naive-like NS31406-specific CD8+ T cells could only be observed using the consensus sequence and not the autologous variant sequence, indicating a lack of recognition of the variant sequence (Fig. 5). This finding suggests that functional, naive-like HCV-specific CD8+ T cells directed against the consensus epitope may persist only in patients infected with viral variants.
Affiliation: Department of Medicine II, University Hospital Freiburg, Freiburg, Germany Faculty of Biology, University of Freiburg, Freiburg, Germany.