Complete nucleotide sequence of a hepatitis B virus, subtype adw2, and identification of three types of C open reading frame.

We have sequenced the complete genome of a hepatitis B virus (A938) obtained from serum of a patient with a high-titred, HBeAg-positive infection. The DNA sequence (3221 bp) was 99.2%, 95.4%, 90.9% and 89% homologous to the sequences of subtypes adw2 (3), adw (1), adr (5) and ayw (9). The adw2 subtype of the A938 virus was verified by analysing the subtype specific amino acids of the major surface antigen. Table 1 shows the localization of the four open reading frames P, S, C and X within the complete genome. The alignment of the amino acid sequence of the C region of A938 with thirteen other HBV sequences revealed subtype specific variations, that can be divided into three distinct types. The C ORF of subtypes adw and adw2 encodes altogether 214 amino acids ('type 1',), that of subtypes adr and ayr ('type 2') and ayw ('type 3') 212 amino acids. Beside the additional two amino acids of type 1 between aa 181 and 182 there are nine subtype specific amino acid positions (Table 2). A peculiarity shows the adw strain sequenced by Sastrosoewignjo et al. (7), in that it contains the shorter type 2 C ORF.