Adefovir resistance related mutations in reverse transcription region and their effect on the biological features of hepatitis B virus / 中华传染病杂志

ABSTRACT

Objective To investigate the effects of adefovir resistance related mutations in hepatitis B virus (HBV) reverse transcription (RT) region on the viral replication and hepatitis B surface antigen (HBsAg) secretion. Methods Twelve adefovir treated chronic hepatitis B (CHB) patients who experienced a viral breakthrough were enrolled in this study. The RT region was amplified by polymerase chain reaction (PCR) using HBV DNA extracted from sera as the template. PCR products were then sequenced and analyzed to find out mutation patterns. Full-length HBV genome was amplified from 4 representative serum samples followed by direct sequencing. The dominant strain was cloned into vector PHY106 to construct a recombinant plasmid containing the 1.1 unit of HBV genome Which was transfected into Huh7 cells. HBsAg and hepatitis B e antigen (HBeAg) expression were determined by enzyme-linked immunosorbent assay (ELISA), meanwhile intracellular HBV DNA level was determined by quantitative real-time PCR. Furthermore strain harboring rtA181T/sW172 · mutation and strain without rtA181 mutation were cotransfected into Huh7 cells. HBsAg and intracellular HBV DNA were also determined after transfection. Results Ten out the 12 patients enrolled in this study exhibited mutations conferring resistance to adefovir. The rtA181T mutation was detected in 5 cases, and the rtA181T/S+rtN236T mutation was observed in 4 cases. Different mutants showed variable HBsAg secretion competency in vitro. Despite the defect of HBsAg secretion of the rtA181T/sW172 · mutant, the replication efficiency was almost the same in different mutants. When the strains with and without rtA181 mutation were cotranfected into cells, the HBsAg level increased in accordance with the amount of stains without rtA181 mutation. However, the intracellular HBV DNA level was not changed significantly. Conclusions The rtA181 mutation is common in patients with adefovir resistance, of which the rtA181T mutation is the major pattern. In vitro analysis reveals that the rtA181T/sW172 · mutant is defective in HBsAg secretion which could be rescued by coexistence of wild-type strains. The replication efficiency in various mutants shows no obvious differences.