Molecular characterization of duck hepatitis B virus isolated from Hubei brown ducks.

The objective of this study was to characterize the genome structure of duck hepatitis B virus (DHBV) isolated from Hubei brown ducks. The natural carrier rate of DHBV in adult ducks from Hubei area was investigated and the DHBV DNA-positive serum screened out. The complete genome of a DHBV strain was amplified by polymerase chain reaction (PCR) and cloned into T vector and sequenced. The results showed that the carrier rate of DHBV in Hubei brown ducks was 10 %. This strain (GenBank accession number DQ276978) had a genome of 3024 nucleotides with three overlapping open reading frames encoding the surface, core and polymerase proteins respectively. Comparison of the strain with 17 DHBV strains registered in GenBank revealed a homology from 89.3 % to 93.5 % at the nucleotide level. The sequences of the structural and functional domains of these proteins were highly conserved. The strain was found to share more signature amino acids in the polymerase genes with the "Chinese" DHBV strains than those of the "Western" country strains. This finding was also corroborated by a phylogenetic tree analysis. Therefore, the DQ276978 might belong to a subtype of the Chinese DHBV strains.