A UNIQUE SEGMENT OF THE HEPATITIS-B VIRUS GROUP-A GENOTYPE IDENTIFIEDIN ISOLATES FROM SOUTH-AFRICA

The preS2/S genes of hepatitis B virus isolated from 29 acutely or chr onically infected individuals in the Gauteng province of South Africa were sequenced. Phylogenetic analysis of these sequences in comparison with global isolates from the GenBank database showed that 24 sequenc es clustered with genotypic group A, three with genotypic group D and one each with genotypic groups B and C. Group A isolates had greater i dentity with groups D (variation of 6.6%) and E (6.8%) than with the E astern groups B (7.4%) and C (8.1%) and were most different from group F (11.0%). Of the South African group A specimens, 59.1% clustered wi th two global sequences to form a discrete segment which we have calle d subgroup A. The amino acid differences that set these isolates apart from the rest of group A tended to cluster in the preS2 region (amino acids 7, 10, 32, 35, 47, 48, 53 and 54), with a few changes occurring in the major surface antigen (amino acid sites 207 and 209). Analysis of isolates showed that there was a 9-fold higher prevalence of the a y determinant in South Africa than previously reported.