CD8A and chronic hepatitis B virus infection: Our data suggest that T-bet might regulate the level of the HBV-specific CD8+ T cell response, and low T-bet levels might be an important factor leading to exhaustion of cytotoxic T cells in chronic hepatitis B. In the CHB group, the level of T-bet had a negative correlation with the level of HBV DNA, suggesting T-bet expression is vital for HBV clearance.