Characterization of the occult hepatitis B virus variants circulating among the blood donors from eastern India

Abstract

A previous study from West Bengal documented very high rate of occult HBV infection (OBI) among the HBsAg negative blood donors. This study was aimed to characterize the OBI strains circulating among the blood donors and to estimate the risk associated with the prevailing viral variants/mutants. Blood samples from 2195 voluntary blood donors were included in the study. HBsAg, HBeAg, anti-HBc, and anti-HBs statuses of the samples were done by ELISA based detection. PCR amplification and sequencing were done to determine HBV genotypes, basal core promoter (BCP), and precore (Pre-C) mutations. Among the study samples, 268 were anti-HBc positive/HBsAg negative, among which 65 (24.25%) were HBV DNA positive. Phylogenetic analysis revealed the presence of HBV/D (87.23%), HBV/A (8.51%), and HBV/C (4.26%) (P < 0.0001). HBV/D3 (65.85%) was the significantly prevalent subgenotype over HBV/D2 (26.83%) and HBV/D1 (7.31%) (P = 0.0003). Considerable prevalence of differential BCP (1752C, 1753C, 1762T/1764A, 1753C+1762T/1764A, 1773C, and 1814C) and reverse transcriptase (rt) gene (rtI91L, rtL93P, rtS106C, rtR110G, rtN118T, rtS119T, rtY126H, rtG127W/R, rtC136R, and rtY158H) mutations was identified. Association of specific HBV subgenotypes with OBI was interesting and needs further study. Clinically relevant mutations were prevalent among the OBI strains which are of serious concern.

Figure 1

Phylogenetic analysis of partial S gene region sequence (300 base pairs) of HBV isolates from Eastern Indian voluntary blood donors with OBI (denoted with “CB”). Different genotypes and subgenotypes are assigned with respect to reference sequences retrieved from the GenBank. The phylogenetic tree was constructed by neighbor joining (NJ) method. The bootstrap values obtained from 1,000 replicates are given at the internal nodes.

Figure 2

Distribution of HBV genotypes/subgenotypes among the blood donors is represented by pie diagram. The frequencies of different subgenotypes of HBV/D are also depicted. The P value (<0.05) indicates that the prevalence of HBV/D3 was significantly higher in comparison to HBV/D1 and HBV/D2.