ABSTRACT
Objective To study the relationship between programmed death-1 (PD-1)/programmed death-1 ligand (PD-L1) expressions and serum hepatitis B virus (HBV) DNA levels in chronic hepatitis B (CHB) patients. Methods A total of 137 CHB patients and 10 healthy controls were enrolled in the study. The peripheral blood mononuclear cells (PBMCs) were isolated from fresh blood samples. HBV-specific cytotoxic T lymphocyte (CTL) was expanded in vitro in 64 human leucocyte antigen (HLA)-A2 positive patients. Flow cytometry was used to detect HLA-A2 type,expressions of PD-1/PD-L1 on PBMCs and PD-1 on HBV specific CTL. Interferon gamma (IFN-γ)was measured by commercial enzyme-linked immunosorbent assay (ELISA) kits. PD-1/PD-L1expressions on PBMCs, HBV-specific CTL and IFN-γ level in PBMC culture medium were compared among patients with different baseline HBV DNA levels. Ten hepatitis B e antigen (HBeAg) positive patients were treated with telbivudine for 24 weeks. The above mentioned parameters were determined and compared before and after the antiviral treatment. Independent-samples t test were used to compare means between two groups and one-way A NOVA were used to compare means among multigroups. We used the pearson corretation test to assess corretation significance. Results The PD-1 and PD-L1 expressions on PBMCs in patients with baseline HBV DNA＜3 lg copy/mL, 3-6 lg copy/mL and ＞6 lg copy/mL were all significant higher than those in healthy control group, but no statistical differences were found. PD-1 expressions on HBV-specific CTL in the three CHB patient groups were (69.3±11.2)%, (76.5±9. 1)% and (78.0±11.7)%, respectively. However, PD-1 expression on HBV-specific CTL was higher, while the frequency of HBV-specific CTL cells was lower in HBV DNA ＞6 lg copy/mL group compared to HBV DNA＜3 lg copy/mL group. The above parameters, including expressions of PD-1 and PD-L1, the frequency of HBV-specific CTL and its PD-1 expression were not significantly different between HBeAg-positive group and HBeAg-negative group. Compared with baseline, PD-1 and PD-L1 expression decreased obviously accompanying with increase of HBV-specific CTL cells frequency and IFN-γ level after 12 weeks and 24 weeks of telbivudine treatment. Conclusions PD-1 expression on HBV-specific CTL correlates with serum HBV DNA level, but not HBeAg status in CHB patients. Suppression of HBV replication can reduce PD-1/PD-L1 expressions and partially restore HBV specific CTL function.