Identification of hepatitis B virus genotypes detected in Lahaul & Spiti district of Himachal Pradesh, India

Background & objectives: Infection by hepatitis B virus (HBV) results in acute or chronic hepatitis. Based on sequence differences of eight per cent or more, HBV is divided into 10 genotypes (A to J) and 35 sub-genotypes. Molecular characterization of the circulating HBV genome has helped in understanding the epidemiology and its clinical importance. Spiti valley in Himachal Pradesh, which shares its border with Tibet, is one of the most HBV prevalent areas in India. Since information about the circulating genotype/s of HBV in this area is limited, this study was conducted to identify the circulating HBV genotypes. Methods: The surface and partial reverse transcriptase gene regions were sequenced using 14 hepatitis B surface antigen-positive samples. Results: Out of the 14 hepatitis B surface antigen-positive samples 11 sample gave quality sequence for further analysis. All the 11 samples belonged to subtype ayw2. The phylogenetic and recombination analysis revealed that five out of 11 samples were of genotype CD1 and the rest six were of genotype D3. Interpretation & conclusions: The CD1 recombinant sub-genotype might have immigrated during past or present transcontinental migration between the adjacent countries. Further studies using full-genome sequencing and high sample size will be helpful to understand this epidemiology and to combat the high prevalence of HBV in the area.