Summary auto-generated
This study examined hepatitis B virus (HBV) genotypes in isolates from 29 acutely or chronically infected individuals in South Africa's Gauteng province by sequencing the preS2/S gene regions. Phylogenetic analysis revealed that 24 isolates clustered with genotypic group A, three with group D, and one each with groups B and C. The research identified a distinct subgroup within group A, designated subgroup A', comprising 59.1% of South African group A isolates and characterized by unique amino acid variations predominantly in the preS2 region (positions 7, 10, 32, 35, 47, 48, 53, 54) and major surface antigen (positions 207, 209). Group A showed greater nucleotide identity with groups D (6.6%) and E (6.8%) than with Eastern groups B (7.4%) and C (8.1%). Notably, the study found a 9-fold higher prevalence of the ay determinant in South Africa (20%) compared to previously reported figures (2.3%). The preS2 region proved highly informative for genotyping despite comprising only 5.1% of the genome. These findings expand understanding of HBV genetic diversity in southern Africa and demonstrate the importance of sequence-based genotyping over serological classification.
Key findings
- A new HBV subgroup designated A' was identified in 59.1% of South African group A isolates, characterized by unique amino acid variations concentrated in the preS2 region
- The ay serotype determinant was detected in 20% of southern African specimens, representing a 9-fold higher prevalence than previously reported (2.3%)
- Group A HBV showed greater genetic identity to African genotypes D and E than to Eastern genotypes B and C, suggesting distinct geographic clustering patterns
- The preS2 region, comprising only 5.1% of the HBV genome, contained sufficient genetic information for complete genotype classification and identification of group-specific determinants
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Abstract
The preS2/S genes of hepatitis B virus isolated from 29 acutely or chronically 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 sequences clustered with genotypic group A, three with genotypic group D and one each with genotypic groups B and C. Group A isolates had greater identity with groups D (variation of 6.6%) and E (6.8%) than with the Eastern 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 with two global sequences to form a discrete segment which we have called 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 ay determinant in South Africa than previously reported.