Serum analyses
HBsAg, HBsAb and HBeAg were analyzed with ELISA kits (Kehua, China). HBV DNA, alanine aminotransferase (ALT), total bilirubin and creatine kinase were analyzed using commercial quantitative assays (Adicon, China). Both serum and intracellular IL-21 levels were measured using ELISA (Boster, China).