A new intertype recombinant between genotypes C and D of hepatitis B virus identified in China.

Hepatitis B virus (HBV) genotypes have a characteristic geographical distribution. More than 90% of chronic HBV patients in China are infected with genotypes B or C. Here, eight HBV isolates that were initially classified as genotype D by PCR-restriction fragment length polymorphism analysis were analysed in detail. The complete HBV genome was sequenced and compared with 32 sequences retrieved from GenBank, representing HBV genotypes A-G. Phylogenetic analysis of the S gene (nt 10-800) classified all eight isolates as genotype D. However, phylogenetic analyses of nt 800-10 and the open reading frames (ORFs) of the precore/core and X genes classified all eight isolates as genotype C. This discordance between phylogenetic trees reconstructed on different ORFs suggested that intertype recombination has occurred in all eight isolates. By using the simplot program, the site of recombination with genotype D was located in the preS2/S region, spanning nt 10-799 in seven of eight isolates and nt 10-1499 in the other isolate. These results demonstrate that intertype recombination should be considered as a type of variation that increases the genetic diversity of HBV. Hybrids of different HBV genotypes might exhibit specific virological properties and their significance in the diagnosis and management of chronic hepatitis B deserves further investigation.