Molecular characteristics of hepatitis B virus in children of Huzhou area, China

Abstract

Objective: The HBV genotypes and surface gene mutation among children born after universal HBV vaccination program were not been clearly investigated in Huzhou, China. Thus, the present study was to investigate HBV genotypes and surface gene mutation in vaccinated children in this area. Methods: Serum samples were collected from 58 children who were chronic HBV infected in Huzhou. The surface gene of HBV were amplified and direct sequencing. Then, the mutations were analyzed. Results: Fifty-six sample were sequenced successfully. The genotype of HBV was genotype B in 45 children and genotype C in 11 children, respectively. Major serotype was adw (42), followed by adr (11) and ayw (3). Sequence analysis showed that 18 amino acid (AA) substitutions sites in major hydrophilic region (MHR) were identified in children (37.5%, 21/56). Most of the substitutions were associated with vaccine immune escape. The genotypes B had a high mutations frequency in the second loop than genotype C. Of note, eight children with low level anti-HBs were still infected with HBV. Conclusion: The predominant genotype and serotype were B and adw among children in Huzhou. Genotype B, MHR mutations, and low anti-HBs levels might be related to immunization failure, although the large-scare vaccination program remarkably decreased the infection of HBV in children, strengthen immunization is recommend in children with low level anti-HBs.