Genotyping and Mutation Pattern in the Overlapping MHR Region of HBV Isolates in Southern Khorasan, Eastern Iran

BACKGROUND Hepatitis B virus, with 8 known distinct genotypes, is one of the most serious health problems which results to liver injuries. The surface gene of Hepatitis B virus completely overlaps with the polymerase gene. Mutations in the RT gene result in changes in the overlapping hepatitis B surface antigen. OBJECTIVES The present study aimed to evaluate the genotypes and prevalence of mutations in a segment of S and RT gene in HBV isolates in Southern Khorasan, Iran. METHODS This was a population-based study comprising 5,235 randomized samples for HBV screening. A nested-polymerase chain reaction (PCR) test was followed by direct sequencing, and the sequences blast with present sequences of NCBI database for genotyping. Alignment and phylogenic analysis was performed using MEGA-6 software, and mutation pattern of this segment was finally surveyed in Bioedit software. RESULTS The mean age was 39.07 ± 14.04 years, with 52.2% female and 47.8% male. All isolates belonged to HBV genotype D, sub-genotype D1. The most amino acid substitutions of surface protein were Q129H (34.42%) and A168V (8.2%), other escape mutants observed in this study were P127L/T, S117G, T125M, S143L, D144E and E164D. In the RT gene, Q149K was the most frequently identified amino acid substitution (9.83%), followed by L122F (8.19%), N118D/T (6.55%), L157M (4.91%), and H124Y (3.27%). CONCLUSIONS This finding represents an ongoing dominancy of HBV genotype D in Eastern Iran, corresponding to other parts of Iran. There were a lot of variations in the S gene leading to an escape mutation, some of which affected the corresponding area of the RT region.