Homologous recombination between different genotypes of hepatitis B virus.

Phylogenetic analysis was used to examine the evolutionary relationships among 99 complete HBV sequences. Analysis revealed nine viral genomes clustered with different genotypes depending on genome region analyzed. This discordance indicated that recombination events occurred during HBV history. The putative breakpoints between genomes of different genotypes have been mapped. Six mosaic genomes representing B/C hybrids were isolated in East Asia and three A/D hybrids in Italy. At least some recombinant strains appear to be fully viable and possess high evolutionary potential. As a result, B/C recombinants overspread through the East Asia region. They were found among the isolates from Japan, China and Indonesia. Our results suggest that recombination is a significant and relatively frequent event in the evolution of HBV genome. A possible mechanism and the implications of recombination for the natural history of HBV, clinically important properties, and phylogenetic reconstruction are discussed.