Distribution of hepatitis B virus genotypes:Phylogenetic analysis and virological characteristics of Genotype C circulating among HBV carriers in Kolkata,Eastern India

摘要

AIM: To evaluate the genotype distribution of hepatitis B virus (HBV) in Eastern India and to clarify the phyloge- netic origin and virological characteristics of the recently identifi ed genotype C in this region. METHODS: Genotype determination, T1762/A1764 mutation in the basal core promoter (BCP) and A1896 mutation in the precore region of 230 subjects were de- termined by restriction fragment length polymorphism method (RFLP) and the result was confi rmed by direct sequencing. RESULTS: The predominant genotypes D (HBV/D) and A (HBV/A) were detected in 131/230 (57%) and 57/230 (25%) samples. In addition, genotype C (HBV/C) was detected in 42/230 (18%) isolates. Surface gene region was sequenced from 45 isolates (27 HBV/C, 9 HBV/A and 9 HBV/D). Phylogenetic analysis revealed that all of the HBV/C sequences clustered with South East Asian subgenotype (HBV/Cs). The sequence data showed re- markable similarity with a Thai strain (AF068756) (99.5% ± 0.4% nucleotide identities) in 90% of the genotype C strains analyzed. T1762/A1764 mutation in BCP re- gion, associated with high ALT was signifi cantly higher in HBeAg negative isolates than HBeAg positive isolates. Frequency of A1896 mutation leading to HBeAg negativ- ity was low.CONCLUSION: The present study reports the genotypic distribution and the characteristics of partial genome sequences of HBV/C isolates from Eastern India. Low genetic diversity and confi nement of HBV/C in Eastern India possibly indicate a recent, limited, spread in this region. Genotype C with T1762/A1764 mutation has been reported to increase the risk for hepatocellular car- cinoma; therefore genotype C carriers in Eastern India should be carefully monitored.