Molecular diversity of Hepatitis B virus (HBV) x gene: A preliminary report from Kerala

      Background: The HBV- x gene expresses a 154 aminoacid multifunctional protein widely associated with hepatocellular carcinoma in chronic patients. Genetic variability of the x gene may impact the differential oncogenic potential of HBV genotypes. This study attempts to investigate genetic variability of the HBV x gene in patients with chronic hepatitis B (CHBV) infection at a tertiary care hospital in Kerala, South India.
      Methods & Materials: Blood samples from fifteen CHBV patients attending the gastroenterology unit of Pushpagiri Institute of Medical Science and Research Centre (PIMS & RC) were included. All samples were tested for HBsAg, HBeAg, HBc IgM, Anti HBs titre and biochemical tests {Aspartate transaminase (AST) & Alanine transaminase (ALT)}. All samples were screened by nested PCR, using primers targeting the core gene of HBV genome. HBV x gene was amplified using previously published primers and analysed by sequencing. All sequencing data were assembled, aligned and compared to the consensus HBV sequence to detect the mutations. Phylogenetic and mutation analyses were done using MEGA version 6.0.
      Results: Of the 15 samples that were positive for HBV core gene, the HBV x gene was detected in 11 (73%) samples while four were negative. Majority of patients were infected with genotypes A (6, 54%) followed by D (5, 45%). All genotypes A strains belonged to subgenotype A1. The A1762T/G1764A double mutation in the BCP region, significantly related to HCC in earlier reported studies was found in 4 patients. Patients with genotype A1 had 50% risk of harbouring the 1762/1764 double mutation. The mutation C1485T in the x gene region were found in 10 samples. The mutation G1467A were observed in all patients with genotype A1.
      Conclusion: A1 was the predominant subgenotype seen in this study. Mutations were significantly high in A1 strains. Association of these mutations with HCC/cirrhosis is unknown. Larger studies are essential for better understanding of the role of these mutations.