Novel hepatitis B virus subgenotype A8 and quasi-subgenotype D12 in African-Belgian chronic carriers.

BACKGROUND

Hepatitis B virus (HBV) is a public health threatening virus and is classified into more than eight genotypes and more than forty subgenotypes.

OBJECTIVES

To characterize and propose novel strains assigned as A8 and D12.

METHODS

Four out of 133 HBV complete genome sequences, isolated from Belgian chronic carriers with African origin were phylogenetically analyzed.

RESULTS

Phylogenetic analyses of HBV genotypes A and D strains exhibited separate clusters supported by significant bootstrap values. The two genotype A strains isolated from Congolese patients, and two genotype D strains isolated from Ghanaian carriers clustered separately from the other known subgenotypes A (A1-A6 and quasi-subgenotypes) and subgenotypes D (D1-D11). The mean inter-subgenotypic nucleotide divergence over the full-length genome sequence between the novel strains (A8 and D12) and A1-A7 and D1-D11 subgenotypes was higher than 4%.

CONCLUSIONS

Phylogenetic analysis of the full-length HBV genome sequences revealed a novel subgenotype and quasi-subgenotype based on the nucleotide divergence and identification of novel amino acids motifs in different ORFs. We identified two strains of the novel subgenotype A8 and two strains of the novel quasi-subgenotype D12. Notably, the analysis demonstrated that the subgenotype A8 strains are a basal lineage that diverged before the other African subgenotypes A.