Novel hepatitis B virus subgenotype A6 in African-Belgian patients

Genome diversity of hepatitis B virus (HBV) is prominent among DNA viruses; which, allowed the virus to be genetically classified into eight genotypes and several subgenotypes.

To introduce and to characterize a novel subgenotype HBV, classified as A6.

HBV full-length genomes were isolated and sequenced from three African-Belgian patients chronically infected with the virus. Using phylogenetic reconstruction and genetic distance calculation, the evolutionary relationships of the novel strains were investigated.

Phylogenetic analysis based on complete genome sequences of genotype A strains revealed distinct clusters supported by high bootstrap values. The three African-Belgian strains clustered separately from the other known A subgenotypes (A1-A5) with maximal bootstrap support (100%). The mean inter-subgenotypic nucleotide divergence over the complete genome sequence between the novel A6 strains and A1-A5 was higher than 4%.

Phylogenetic analysis of the complete genome sequences yielded maximal bootstrap value support for nodes that establish the new lineage as a novel subgenotype. In addition, nucleotide divergence more than 4% based on full-length genome of the virus, clearly demonstrated that the three African-Belgian strains belonged to a novel subgenotype of HBV, which was assigned as "A6". Noteworthy, the phylogeny of genotype A demonstrated that the A6 is a basal lineage that diverged earlier from the other African subgenotypes of genotype A.