Hepatitis C virus-specific T cell responses against conserved regions in recovered patients

For the design of peptide-based vaccines against the hepatitis C virus it is essential to acquire more information on frequently recognized epitopes in patients with successful immune control of HCV in the context of different HLA types. A matrix approach using 393 15mer peptides from conserved HCV regions overlapping by 13 amino acids was applied in 52 HCV-recovered individuals. Candidate peptides were further tested in two independent laboratories. 38 peptides induced IFN-gamma responses in ELISPOT assays including 15 previously unknown epitopes. There was no particular immune dominance as only five peptides were recognized by more than three individuals. Seven out of 14 peptides tested in more detail could be confirmed to be immunogenic using ELISPOT and cytotoxicity assays. While only 33% of HCV-recovered individuals recognized recombinant HCV proteins, 81% of individuals tested positive in the matrix approach (p<0.001). The strength, frequency and breadth of HCV-specific T cell responses were similar in spontaneously recovered patients than in interferon-recovered patients. In conclusion (i) we identified novel HCV epitopes in conserved regions, (ii) confirmed the inter-individual diversity of HCV-specific T cell responses and (iii) found no significant differences in HCV-specific T cell responses between spontaneously recovered and IFN-recovered patients.