ABSTRACT
Objective To investigate the effects of HBcAg-specific CD8+T cells on inhibiting HBV replication in vitro,and to search the cytokine of noncytolytic mechanisms in viral clearance. Methods By the method of coculture of HepG2.2.15 cell (target cells) with HLA-A2 matched HBcAg-specific CD8+T cell clone (effector cells) at E:T ratios of 1:50,and monitoring HBV production (HBsAg,HBeAg,and HBV-DNA)in coculture supernatants at 24h,48h and 72h,the percentage of decrease in HBV replication level was observed. Furthermore,blocking experiment with neutralizing mAbs to IFN-? was performed to evaluate the effect of this cytokine. Results CD8+T clone produced high levels of IFN-?following coculture with 2.2.15 cells. HBsAg,HBeAg and HBV-DNA in coculture supernatants were significantly reduced,and the greatest effect was observed at 72h by 54.55%,50.36% and 74.55%,respectively. The reduction of HBV DNA was decreased followed by using neutralizing mAbs to IFN-?. The maximum activity of cytotoxicity of target cells was at 24h by 15.66%. Conclusion ①HBV-specific CD8+T cells inhibit HBV replication by cytolytic and noncytolytic mechanisms.②The effect of noncytolytic mechanisms is mainly mediated by IFN-?.
ABSTRACT
BACKGROUND/AIMS: Viral suppression of the hepatitis B virus (HBV) can be induced by lamivudine, but the relapse seen in many patients after cessation of lamivudine therapy is troublesome. We thought that the host immune response is important to prevent viral relapse. We compared the frequency of HBV-specific CD8+ T cells in the peripheral blood and their expansion capacity after exposure to viral antigen between the patients showing sustained HBeAg seroconversion after use of lamivudine and those patients without sustained response. METHODS: We analyzed HBV-specific CD8+ T cells that were isolated from the blood of 14 patients with HLA-A2 who showed lamivudine induced HBeAg seroconversion (HBV DNA < 0.5 pg/mL, and the cells were negative for HBeAg) at the end of lamivudine therapy. The purified T cells were directly stained ex vivo, after they had been stimulate with synthetic peptide, using the HBV core 18-27-specific HLA tetramer (Tc 18-27) and monoclonal antibody to CD8. The HBV viral load was quantified by the Amplicor HBV Monitor assay. RESULTS: In patients with a sustained HBeAg response (the sustained group) for a duration of 15.5 months of follow-up, the median number of Tc 18-27 cells out of the 5 X 10(4) CD8+ T cells was 49.5 (15-135). On the contrary, in patients who experienced relapse (the relapsed group) during a median of 7.5 months of follow-up, the median number of Tc 18-27 cells out of the 5 X 10(4) CD8+ T cells was 13.5 (0-95). Especially, among patients with a viral load of HBV DNA < 1 X 10(3) copies at the end of treatment, the median number of Tc 18-27 cells out of 5 X 10(4) CD8+ T cells was 87 (45-135) in sustained group compared to 12 (6-50) in the relapsed group. All patients in the sustained group demonstrated a vigorous expansion of the core 18-27-specific CD8+ T cells after stimulation with viral peptide, in contrast to only 3 out of 8 patients in the relapsed group. CONCLUSIONS: This study demonstrates that the frequency and functional responsiveness of the circulating HBV-specific CD8+ T cells may be important for obtaining a sustained HBeAg response to lamivudine.