Unique preS sequence in a gibbon-derived hepatitis B virus variant.

A unique hepatitis B virus (HBV) variant has been identified in a gibbon (Hylobates lar) which could be passed to a chimpanzee by experimental inoculation. This HBV variant had been shown to have no reactivity to a monoclonal anti-preS2 antibody (preS2 mAb 116-34) differentiating it from all human HBV specimens tested. This gibbon sera also was not recognized by an anti-preS1 mAb which binds the preS1 hepatocyte receptor region, amino acids 27-35. In this paper, we report the DNA sequence of the gibbon HBV PreS gene. The lack of preS2 mAb (116-34) binding can be explained by a unique nucleotide substitution of A for C in the second codon of the preS2 region leading to the replacement of glutamine with lysine. Two other unique changes were observed at the seventh and 24th amino acid positions in the preS2 gene leading to a substitution of a valine for threonine and alanine, respectively. Unlike all human derived HBV sequences in the preS1 region, the gibbon HBV had a glutamic acid instead of an aspartic acid at amino acid residue 27. Another unique substitution was a leucine for alanine at preS1 position 33. These amino acid changes in the gibbon HBV may explain its unique preS mAb reactivity.