AIM

To investigate a HLA-A2-restricted CTL epitope variation at the N terminal of hepatitis C virus (HCV) helicase and the proliferative response of cytotoxic T lymphocytes (CTLs) to this epitope.

METHODS

Two patients infected with HCV were followed up for 7 years. Blood samples taken at the first year and the fifth year were used for viral RNA extraction. Using RT-PCR, the N terminal gene of helicase region was amplified from the extracted RNA. The amplified segments were subcloned and sequenced to assess the epitope variation. A HLA-A2-restricted CTL epitope peptide was synthesized according to the sequencing result. HLA types of the two patients were determined by serological method. The peripheral blood lymphocytes were separated from the two patients at 7th year after infection and cultured with the synthetic CTL epitope peptide to assess the CTL's proliferative response.

RESULTS

In the HLA-A2(+) individual, there was an amber mutation at the first amino acid of the epitope in the first year after infection, but the amber mutation disappeared after 5 years. However, in the HLA-A2(-) individual, the epitope had neither variation nor amber mutation in 5 years after infection. 7 years after HCV infection, T lymphocytes from both individuals had no proliferative response to the epitope peptide.

CONCLUSION

The amber mutation of the epitope at N terminal of helicase may be associated with viral immune escape. CTLs have no response to the epitope peptide in the N terminal of HCV helicase in the later stage of chronic HCV infection.