A novel hepatitis B virus recombinant genotype D4/E identified in a South African population

BACKGROUND: Genetic diversity is a characteristic trait of the hepatitis B virus (HBV) and has been associated with different clinical outcomes. In South Africa, HBV infection is a major public health concern. Most HBV infections are caused by genotype A strains. However rare cases of infection with HBV genotype D have been reported. The purpose of this study was to investigate the molecular characteristics of a rare HBV subgenotype D4 isolate. METHODS: The full-length genome of isolate ZADGM6964 was amplified in a one-step polymerase chain reaction. The amplified product was purified and cloned into a pGEM®-T Easy Vector System to investigate the genetic diversity of the viral quasi-populations. The primary isolate and clones were then directly sequenced and analysed using an array of bioinformatics software. RESULTS: Phylogenetic analysis showed that the primary isolate and cloned sequences formed a monophyletic cluster away from subgenotype D4 reference strains. Further recombination analysis revealed that isolate ZADGM6964 was in fact a D4/E recombinant strain with breakpoints identified within the X and overlapping pre-Core/Core open reading frames with a >70% bootstrap confidence level. The recombinant genotype D4/E was found to be unique from other D/E strains archived in the genetic database, GenBank. CONCLUSION: This study represents the first ever report on the isolation and molecular characterization of an HBV D4/E recombinant strain in South Africa. The findings provide evidence of further HBV genetic diversity in South Africa than has been previously reported.