The putative recombination of hepatitis B virus genotype B with pre-C/C region of genotype C.

Among hepatitis B virus (HBV) genotypes the B and C are most prevalent in China. To further study on the inside story of the intertypes, the genotype of 136 sequences from Chinese patients were analyzed either by restriction fragment length polymorphism on fragments or by phylogenetic analysis and bootscanning on full genome. The 22 complete sequences of genotype B clustered with different genotypes depending on gene fragments analyzed, which indicated that recombinant events occurred during HBV evolutionary history. To locate the recombinant regions, the sequences of HBV entire genome were analyzed by SimPlot program. The recombinant regions of B genotype with recombination were mapped in the pre-C/C region with relatively less varied size. Besides, three sequences of genotype C have recombination with genotype B or D in different regions. However, among all of the 136 sequences, none of authentic genotype B was identified. To investigate the possible mechanism responsible for intertype recombination, the selection pressure on the recombinant region was estimated by using CODEML program. All models allow for positively selected sites suggest existence of positive selection pressure. In conclusion, the genotype B with recombination was exclusive subgroup of genotype B in China. The mosaic genotype B might result from immune pressure on the pre-C/C gene.