Abstract
BackgroundNine subgenotypes from genotype B have been identified for hepatitis B virus (HBV). However, these subgenotypes were less conclusive as they were often designated based on a few representative strains. In addition, subgenotype B6 was designated twice for viruses of different origin.MethodsAll complete genome sequences of genotype B HBV were phylogenetically analyzed. Sequence divergences between different potential subgenotypes were also assessed.ResultsBoth phylogenetic and sequence divergence analyses supported the designation of subgenotypes B1, B2, B4, and B6 (from Arctic). However, sequence divergences between previously designated B3, B5, B7, B8, B9 and another B6 (from China) were mostly less than 4%. In addition, subgenotype B3 did not form a monophyly.ConclusionCurrent evidence failed to classify original B5, B7, B8, B9, and B6 (from China) as subgenotypes. Instead, they could be considered as a quasi-subgenotype B3 of Southeast Asian and Chinese origin. In addition, previously designated B6 (from Arctic) should be renamed as B5 for continuous numbering. This novel classification is well supported by both the phylogeny and sequence divergence of > 4%.
Highlights
Nine subgenotypes from genotype B have been identified for hepatitis B virus (HBV)
Cluster 1 was composed of 27 viruses belonging to subgenotype B6 [3], with a bootstrap value of 100%. 37 viruses of cluster 2 were isolated from Japan and were designated as subgenotype B1 [2,11]
The bootstrap value for subgenotype B2 was only 46% and the sequence divergence between subgenotypes B4 and B2 was less than 4%, since subgenotype B2 has been widely accepted, it should be maintained in order to avoid more confusion
Summary
Nine subgenotypes from genotype B have been identified for hepatitis B virus (HBV). These subgenotypes were less conclusive as they were often designated based on a few representative strains. Based on the rule that different subgenotypes should diverge by at least 4% over the genome [4], genotypes A [5], B [6], C [7], D [8], and F [9] have been reported to have evolved into various subgenotypes [10]. Viruses of subgenotype Bj are not recombinants, while those of subgenotype Ba are B/C distribution of HBV subgenotypes might relate to the ethnic origin of the infected patients [6]
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