Mutations in the S gene of hepatitis B virus in three generations of patients with chronic hepatitis B

Abstract

Failure to neutralize HBsAg and subsequent escape from the host immune system may be caused by HBsAg mutations, particularly in the "a" determinant, which alters the antigenicity of the protein. The purpose of this study was to examine the frequency of S gene mutations in three generations of HBV cases in northeastern Iran. In this study, 90 patients with chronic HBV were assigned to three groups according to the inclusion criteria. The plasma were utilized to extract viral DNA, and the PCR was applied. Direct sequencing and alignment were performed on the S gene, using reference sequence. The results indicated that all HBV genomes were categorized as the genotype D/ayw2. Among 79 point mutations detected, 36.8% were silent, and 56.2% were missense. In the S region, mutations were observed in 88.9% of CHB subjects studied. In the three-generation group, 21.5% of mutations were in the "a" determinant, and 2.6%, 19.5%, and 87.0% of these mutations were observed in antigenic epitopes of CTLs, CD₄⁺, and B cells, respectively. In addition, 56.7% of mutations occurred at Major Hydrophilic Region. S143L and G145R mutations which the most prevalent in the three-generation (36.7%, 20%), and two-generation (42.5%, 20%) groups, related to the failure of HBsAg detection, vaccine, and immunotherapy escape. The findings showed that most of the mutations were concentrated in the B cell epitope. Most CHB cases from the three-generation, especially grandmothers, had HBV S gene mutations and subsequent amino acid mutations, suggesting that these mutations may be critical for pathogenesis and vaccine evasion.

Keywords: Chronic hepatitis B; Hepatitis B virus; Mutation; S gene; Three generations.