Hepatitis B virus （HBV）-specific cytotoxic T lymphocytes （CTLs） are believed to play a major role in viral clearance and disease pathogenesis during HBV infection. To clarify the differences in host immune responses between self-limited and chronic HBV infections, we constructed three HLA-A＊0201/HBV tetramers with immunodominant epitopes of core18-27, polymerase 575-583 and envelope 335-343, and analyzed the HBV-specific CTLs in peripheral blood mononuclear cells （PBMCs） from patients infected with HBV. The frequencies and expansion ability of HBV-specific CD8＋T cells in most self-limited HBV infected individuals were higher than those in chronic HBV-infected patients. HBV-specific CD8＋T cells could be induced by in vitro peptide stimulation from chronic patients with a low level of serum HBV-DNA but not from those with a high level of serum HBV-DNA. In chronic infection, no significant correlation was found either between the frequencies of HBV-specific CD8^＋ T cells and the viral load, or between the frequencies and the levels of alanine transaminase. Our results suggested that the frequencies of HBV-specific CTLs are not the main determinant of immune-mediated protection in chronic HBV infection and immunotherapeutic approaches should be aimed at not only boosting a HBV-specific CD8^＋T response but also improving its function.
Human ISG20 gene was cloned and the effect of its anti-HBV was primarily studied. The ISG20 gene was amplified from HeLa cells by RT-PCR and recombinant vector expressing ISG20 was constructed by genetic engineering. The overexpression of ISG20 in HepG2 cells was detected by Western blot and the levels of secretion of HBs antigen and HBe antigen tested by ELISA. The results showed that： （1） Sequence of ISG20 cloned was consistent to that published in Genebank; （2） Recombinant vector expressing ISG20 could be expressed in HepG2 cells by transfection; （3） The overexpression of ISG20 protein could reduce the levels of the secretion of HBs antigen and HBe antigen in transfected HepG2 cells. It was suggested that the overexpression of recombinant ISG20 in culture cells could reduce the synthesis of HBV proteins.
