A novel HBV recombinant (genotype I) similar to Vietnam/Laos in a primitive tribe in eastern India.

Genotyping of 20 strains of Hepatitis B virus (HBV) from the Idu Mishmi primitive tribe of northeast India identified multiple genotypes and the presence of a unique cluster grouping with strains from Vietnam and Laos identified as novel recombinants/genotype I. Sequence analysis (similarity and bootscan plots) of three complete HBV genomes from the tribe provided evidence of recombination. Phylogenetic analyses supported recombination between genotypes A, G and C. The Pre-S gene between nt 2943 and 397 was clearly of genotype A origin, whereas nt 397-1397 represented genotype G and nt 1397-2943 represented genotype C. Percentage divergence from genotypes B, D, E, F, G and H varied from 9.2 +/- 0.45% to 13.8 +/- 0.53%, whereas genotype A and C differed by 7.9 +/- 0.42% and 7.4 +/- 0.39% respectively. The identification of similar recombinant viruses in three countries, especially in a primitive tribe with no contact with the outside world suggests that these viruses do not represent recent recombination events, but circulation of closely related viruses highly divergent from known HBV genotypes and should be classified as members of genotype 'I'.