Partial virological response to entecavir treatment in nucleos(t)ide-naïve patients with HBeAg-positive chronic hepatitis B is not caused by reduced sensitivity

Some patients with chronic hepatitis B (CHB) receiving entecavir (ETV) exhibit partial virological response (PVR) to ETV and the mechanism is not clear. In this study, we aim to investigate the in vitro susceptibility of residual clinical strains isolated from the sera of nucleos(t)ide-naïve hepatitis B virus e antigen (HBeAg)-positive patients with CHB and PVR to ETV, and to evaluate the clinical and virological responses to prolonged ETV monotherapy in these patients. We followed 69 nucleos(t)ide-naïve HBeAg-positive CHB patients receiving ETV treatment, with 13 partial responders to ETV. And we found that no genotypic resistance mutants were detected among the 13 PVR patients. Phenotypic analysis revealed that the residual HBV strains had normal replication capacity, and were as susceptible to ETV as wild-type HBV. All PVR patients continued to receive ETV monotherapy, and serum HBV DNA of the majority became undetectable after prolonged treatment. However, none of these patients achieved HBeAg loss. In contrast, 25.6% and 23.2% of the patients with virological response achieved HBeAg loss ( P  < 0.001) and HBeAg seroconversion ( P  < 0.001) at week 144, respectively. Thus, we conclude suboptimal response to ETV might not be due to reduced HBV susceptibility to ETV, and prolonging ETV monotherapy in patients with PVR is recommended.