[A HLA-A2-restricted-CTL epitope variation at the N-terminal of HCV helicase and the immune response of CTLs].
OBJECTIVE
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.


CONCLUSIONS
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.
Guo
Hua-zhang
HZ
Department of Pathology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China. guohzh@fmmu.edu.cn
Wang
Wen-liang
WL
Wang
Tao
T
D000328:Adult; D000595:Amino Acid Sequence; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000276:immunology; D014644:Genetic Variation; D015789:HLA-A2 Antigen / Q000032:analysis; D016174:Hepacivirus / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D006526:Hepatitis C / Q000235:genetics / Q000276:immunology / Q000821:virology*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D020365:RNA Helicases / Q000235:genetics / Q000276:immunology; D012367:RNA, Viral / Q000032:analysis; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000276:immunology; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D020365:RNA Helicases; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases