Analysis of hepatitis B virus X gene phylogeny, genetic variability and its impact on pathogenesis: implications in Eastern Indian HBV carriers.

HBx genetic variability was explored in the Eastern Indian population with low HCC incidence. DNase I sensitive HBV DNA was detected in 53% samples, which differed significantly between clinical groups (P<0.001). HBV genotypes A (Aa/A1), C (Cs/C1) and D (D1, D2, D3, D5) were detected in 37.5%, 18.7% and 43.7% samples respectively. Population specific signature HBx residues A(36), V(88), S(101) in Aa/A1 and residues P(41), Q(110) in D5 were detected. Mutations T(127), M(130) and I(131) were detected in 66.7%, 91% and 75% of genotype A, C and D5 samples respectively. Very low occurrence of HCC associated mutations (V(5)M/L, P(38)S, and H(94)Y) and absence of C-terminal deletions were observed. Our study shows that HBV genotype associated clinically important HBx variations may evolve and act distinctly in different geo-ethnic populations. Further studies on HBx functions from the perspective of genetic variability are essential for the better understanding of the clinical significance of HBV.