PD-1 expression on CTL may be related to more severe liver damage in CHB patients with HBV genotype C than in those with genotype B infection.

Compared with Chronic hepatitis B (CHB) patients infected with genotype B, those infected with genotype C have higher hepatic histopathological activity and higher level of alanine aminotransferase (ALT). Our previous studies suggest that this phenomenon is related to lower level of HBV specific cytotoxic T lymphocyte (CTL) of patients infected with genotype C than those infected with genotype B, but its mechanism was not clear. The aim of present study was to explain the possible mechanism of lower level of HBV specific CTL and more serious liver function damage of patients infected with genotype C than those infected with genotype B through study on relationship between expression of HBV specific CTL surface programmed death receptor-1 (PD-1) and viral genotypes of CHB patients. A total of 100 CHB patients were studied, human leukocyte antigen (HLA)-A2 positive, hepatitis B virus (HBV) DNA>10(3) copies/ml, of which 48 cases were genotype C (48%) positive, and 52 cases were genotype B positive (52%). Expression of Peripheral blood HBV specific CTL surface PD-1, levels of HBV specific CTL, HBV DNA, ALT and total bilirubin (TBil) of patients infected with genotype C and B were compared. Expression of HBV specific CTL surface PD-1 of CHB patients infected with genotype C was significantly higher than that of patients infected with genotype B, t = 17.57, P < 0.001, level of HBV specific CTL was significantly lower than that of patients infected with genotype B, t = 23.64, P < 0.001, level of HBV DNA was significantly higher than that of patients infected with genotype B, t = 9.43, P < 0.001, level of ALT was significantly higher than that of patients infected with genotype B, t = 13.42, P < 0.001. Expression of peripheral blood HBV specific CTL surface PD-1 of CHB patients infected with genotype C was significantly higher than that of patients infected with genotype B, resulting in lower level of HBV specific CTL and higher level of HBV DNA of patients infected with genotype C than those of patients infected with genotype B. So liver function damage of CHB patients infected with genotype C was more serious than those infected with genotype B.