AIM: To investigate peripheral T-lymphocyte sub-population profile and its correlation with hepatitis B virus (HBV) replication in patients with chronic hepatitis B (CHB).METHODS: Distribution of T-lymphocyte subpopulations in peripheral blood was measured by flow cytometry in 206 CHB patients. HBV markers were detected with ELISA. Serum HBV DNA load was assessed with quantitative real-time polymerase chain reaction (PCR). The relationship between HBV replication and variation in peripheral T-cell subsets was analyzed.RESULTS: CHB patients had significantly decreased CD3+ and CD4+ cells and CD4+/CD8+ ratio, and increased CD8+ cells compared with uninfected controls (55.44 ± 12.39 vs 71.07 ± 4.76, 30.92 ± 7.48 vs 38.94 ± 3.39, 1.01 ± 0.49 vs 1.67 ± 0.33, and 34.39 ± 9.22 vs 24.02 ± 4.35; P < 0.001, respectively). Univariate analysis showed a similar pattern of these parameters was significantly associated with high viral load, presence of serum hepatitis B e antigen (HBeAg) expression, liver disease severity, history of maternal HBV infection, and young age at HBV infection, all with P < 0.01. There was a significant linear relationship between viral load and these parameters of T-lymphocyte subpopulations (linear trend test P < 0.001). There was a negative correlation between the levels of CD3+ and CD4+ cells and CD4+/CD8+ ratio and serum level of viral load in CHB patients (r = -0.68, -0.65 and -0.75, all P < 0.0001), and a positive correlation between CD8+ cells and viral load (r = 0.70, P < 0.0001). There was a significant decreasing trend in CD3+ and CD4+ cells and CD4+/CD8+ ratio with increasing severity of hepatocyte damage and decreasing age at HBV infection (linear trend test P < 0.01). In multiple regression (after adjustment for age at HBV infection, maternal HBV infection status and hepatocyte damage severity) log copies of HBV DNA maintained a highly significant predictive coefficient on T-lymphocyte subpopulations, and was the strongest predictor of variation in CD3+, CD4+, CD8+ cells and CD4+/CD8+ ratio. However, the effect of HBeAg was not significant.CONCLUSION: T-lymphocyte failure was signifi-cantly associated with viral replication level. The substantial linear dose-response relationship and strong independent predictive effect of viral load on T-lymphocyte subpopulations suggests the possibility of a causal relationship between them, and indicates the importance of viral load in the pathogenesis of T cell hyporesponsiveness in these patients. AIM: To investigate peripheral T-lymphocyte sub-population profile and its correlation with hepatitis B virus (HBV) replication in patients with chronic hepatitis B (CHB). METHODS: Distribution of T-lymphocyte subpopulations in peripheral blood was measured by flow cytometry in 206 CHB patients. HBV markers were detected with ELISA. Serum HBV DNA load was assessed with quantitative real-time polymerase chain reaction (PCR). The relationship between HBV replication and variation in peripheral T-cell subsets was analyzed.RESULTS: CHB patients had significantly decreased CD3 + and CD4 + cells and CD4 + / CD8 + ratio, and increased CD8 + cells compared with uninfected controls (55.44 ± 12.39 vs 71.07 ± 4.76, 30.92 ± 7.48 vs 38.94 ± 3.39, 1.01 ± 0.49 vs 1.67 ± 0.33, and 34.39 ± 9.22 vs 24.02 ± 4.35; P <0.001, respectively). Univariate analysis showed a similar pattern of these parameters was significantly associated with high viral load, presence of serum hepatitis B e antigen (HBeAg) expr ession, liver disease severity, history of maternal HBV infection, and young age at HBV infection, all with P <0.01. There was a significant linear relationship between viral load and these parameters of T-lymphocyte subpopulations (linear trend test P <0.001) . There was a negative correlation between the levels of CD3 + and CD4 + cells and CD4 + / CD8 + ratio and serum level of viral load in CHB patients (r = -0.68, -0.65 and -0.75, all P <0.0001), and a positive correlation There was a significant decreasing trend in CD3 + and CD4 + cells and CD4 + / CD8 + ratio with increasing severity of hepatocyte damage and decreasing age at HBV infection (r = 0.70, P <0.0001) 0.01). In multiple regression (after adjustment for age at HBV infection, maternal HBV infection status and hepatocyte damage severity) log copies of HBV DNA with a highly significant predictive coefficient on T-lymphocyte subpopulations, and was the strongest predictable r of variation in CD3 +, CD4 +, CD8 + cells and CD4 + / CD8 + ratio. However, the effect of HBeAg was not significant. CONCLUSION: T-lymphocyte failure was signifi- cantly associated with viral replication level. The substantial linear dose-response relationship and strong independent predictive effect of viral load on T-lymphocyte subpopulations suggests the possibility of a causal relationship between them, and indicates the importance of viral load in the pathogenesis of T cell hyporesponsiveness in these patients.