Emergence of hepatitis B virus S gene mutants in patients experiencing hepatitis B surface antigen seroconversion after peginterferon therapy

Abstract

With anti-hepatitis B virus (anti-HBV) therapy using peginterferon, the seroconversion of hepatitis B surface antigen (HBsAg), which is considered a cure of the disease, can be achieved in a small percentage of patients. Eight of 245 consecutive patients (3.27%) with chronic hepatitis B who received peginterferon therapy at our center achieved HBsAg seroclearance. Surprisingly, two of the eight patients remained viremic according to standard HBV DNA assays. The coding regions of the HBV pre-S/S gene, which were derived from serial serum samples, were analyzed. Site-directed mutagenesis experimentation was performed to verify the phenotypic alterations in Huh-7 cells. In patient 1, an sT125A mutant developed during the HBsAg-negative stage and constituted 11.2% of the viral population. The HBV DNA level was 2.73 × 104 IU/mL at the time of detection. This mutant was not detectable in the HBsAg-positive stages. A phenotypic study of Huh-7 cells showed a significant reduction of antigenicity. In patient 2, an sW74* truncation mutation was found during the HBsAg-negative stage and constituted 83.1% of the viral population. The HBV DNA level was 4.12 × 104 IU/mL at the time of detection. A phenotypic study of Huh-7 cells showed a complete loss of antigenicity. Patient 2 subsequently experienced an episode of hepatitis relapse 7 months after the end of treatment and was negative for HBsAg throughout the hepatitis flare. Conclusion: During antiviral therapy with peginterferon, the achievement of HBsAg seroconversion does not necessarily indicate viral eradication. The emergence of S gene mutants is another possibility, and a relapse with HBsAg-negative hepatitis can occur. © 2011 American Association for the Study of Liver Diseases.