Z Gastroenterol 2006; 44 - P191
DOI: 10.1055/s-2006-950788

Frequency and functional analysis of variants of the immunodominant epitope NS3–1073: Relevance for vaccine design

P Fytili 1, G Dalekos 2, M Cornberg 1, C Sarrazin 3, V Schlaphoff 1, W Zauner 4, T Berg 5, K Zachou 2, MP Manns 1, C Klade 4, H Wedemeyer 1
  • 1Medizinische Hochschule Hannover, Gastroenterologie, Hepatologie und Endokrinologie, Hannover, Germany
  • 2Medical School, University of Thessaly, Larissa, Greece
  • 3Universitatsklinikum des Saarlandes, Homburg/Saar, Germany
  • 4Intercell AG, Vienna, Austria
  • 5Charité Universitatsmedizin Berlin, Berlin, Germany

Introduction: The HCV-specific HLA-A2-restricted NS3–1073 epitope is one of the most frequently recognized in hepatitis C. Responses against NS3–1073 have been associated with clearance of acute HCV-infection. Therefore this epitope is an interesting candidate for a HCV-peptide vaccine. However, heterogeneity between genotypes and mutations in the epitope has to be considered as an obstacle. Even if cross-reactivity is common, small changes between peptide variants can have detrimental effects.

Methods: We investigated the sequence variability within NS-1073 across HCV-genotypes, and determined the cross-reactivity of NS3–1073 wild-type-specific CD8 T-cells with variants derived from HCV-genotypes 1–6 by interferon-gamma ELISPOT assays.

Results: 28 naturally occurring HCV-1073-variants as compared with the wild type genotype-1 variants (CVNGVCWTV/CINGVCWTV) were identified. The frequency of variants among genotype-1 patients (n=21) was 9.5% in Greek (n=21) and 9.2% in German (n=216) patients. Specific T-cell lines were established from HLA-A2-positive HCV-recovered patients, chronic HCV patients and HCV-negative individuals. Although the proliferation of NS3–1073-specific T-cells differed significantly between the 4 groups, there was no major difference in specificity-pattern of cross-reactive IFN-gamma production. While genotypes 2/3 variants tested negative except one genotype 2 peptide, genotype 4–6 peptides induced 30–100% of the IFN-gamma response as compared to CVNGVCWTV. Also 4 genotype-1 variants (N1075S, V1077A, V1077A/W1079M, N1075S/V1077A) were not recognized by HCV-1073-wild-type-expanded T-cell lines. This loss of reactivity was seen although the 1075 and 1077-mutants represented conservative aa-changes within an aa-group of similar physiochemical properties.

Conclusion: HCV-NS-1073-specific T-cells displayed cross-genotype-reactivity, in particular for genotypes 4–6. However, single aa changes within the TCR-binding domain may completely abolish recognition even by conservative exchanges within genotype-1 and thus limiting the potential efficacy of vaccines containing the NS-1073-wild-type peptide.