Molecular genetic characterization of hepatitis B virus in blood donors from South Vietnam

Abstract

The problem of transfusion safety preventing parenteral viral hepatitis transmission remains relevant. Viral hepatitis B (HB) is the most common viral infection transmitted through transfusion procedures. One of the natural phases of a chronic viral hepatitis B (CHB) course is occult hepatitis B infection (OBI) characterized by undetectable HBsAg level (regardless of other serological marker levels) along with detected hepatic HBV DNA as well as blood viral load ranging from extremely low to undetectable. In Vietnam, prevention of transfusion-based HBV transmission is focused on donor screening; it is still based solely on HBsAg serology. As such, OBI remains a potential threat to blood transfusion safety. Assessing hepatitis B virus (HBV) DNA is a reliable preventive measure against HBV transmission from HBsAg– donors, especially in highly endemic regions. The aim of our work was HBV identification and molecular genetic characterization in blood donors from South Vietnam. The study material was presented by 500 donor serum samples. Subjects were examined for HBV markers with qualitative detection of HBsAg, HBs IgG, and HBcore IgG. Amplification and subsequent HBV sequencing were performed using nested PCR with overlapping primer pairs jointly flanking the complete HBV genome (S, P, C, X genes). Full-size HBV genome nucleotide sequences were obtained for 58 samples. Among blood donors, taking into account HBsAg+ and HBsAg– samples, HBV DNA was detected in 11.6%, including 8.6% OBI. HBV phylogenetic analysis showed genotypes B and C. Vaccine escape mutations and mutations that contribute to disease progression were identified. Current screening in Vietnam is insufficient for eliminating the risk of transfusion-transmitted HBV infection. The major risk factor is OBI. PCR testing for HBV should be considered for blood donor screening.