Hepatitis B Virus Genotype Study in West Africa Reveals an Expanding Clade of Subgenotype A4

Abstract

Hepatitis B virus (HBV) classification comprises up to 10 genotypes with specific geographical distribution worldwide, further subdivided into 40 subgenotypes, which have different impacts on liver disease outcome. Though extensively studied, the classification of subgenotype A sequences remains ambiguous. This study aimed to characterize HBV isolates from West African patients and propose a more advanced classification of subgenotype A. Fourteen HBV full-length genome sequences isolated from patients from The Gambia and Senegal were obtained and phylogenetically analyzed. Phylogenetic analysis of HBV genotype A sequences isolated from Senegalese and Gambian patients exhibited separate clusters from the other known and confirmed subgenotypes A (A1, A2, A6). Most of the sequences (10/14) clustered with an isolate from Cuba, reported as subgenotype A4 (supported by maximal bootstrap value). Four isolates from The Gambia and Senegal clustered separately from all other subgenotypes and samples sequenced in the study. Three of which from The Gambia, designated as an expanding clade of subgenotype A4, exhibited a mean inter-subgenotypic nucleotide divergence over the entire genome sequence higher than 4% in comparison with the other subgenotypes and the other isolates sequenced in the study, except with subgenotype A4 isolates (3.9%), and this was supported by a maximal bootstrap value. The last one from Senegal seemed to be an expanding subgenotype close to the new clade of A4. Amino acid analysis unveiled a novel motif specific to these isolates. This study revealed an expanding evolution of HBV subgenotype A and novel amino acid motifs. It also highlighted the need for a consensus regarding the analysis and classification of HBV sequences.

Contemporary and historical human migration patterns shape hepatitis B virus diversity

“…Excepting their most ancient origins, our results agree with the work of others, with HBV-A demonstrating an African origin ( Pourkarim et al. 2010a , 2010b , 2011 ; Toyé et al. 2021 ).…”

“…2021 ). Our results underscore the African continent as the evolutionary cradle of HBV-A diversification ( Andernach et al., 2009 ; Toyé et al. 2021 ), and we date the proliferation and worldwide dispersal of this genotype to coincide with the transatlantic slave trade (1520s–1850s).…”

Frequency distribution of hepatitis B virus (HBV) genotypes in Iraqi patients

“…Ten genotypes (A-J) and 46 sub-genotypes have been identified to date. [A (1-6), B(1-5), C(1-16), D(1-9), E, F(1-4), G, H, I(1-2), and J], [12,13]. Whole-genome sequencing followed by phylogenetic analysis is a gold standard for HBV genotyping, identifying predominant, novel, and recombinant genotypes [14].…”

Genotyping Study on Hepatitis B Virus Among Egyptian Patients

“…Five genotypes (A-E) of HBV have been found in Africa: Genotype A was discovered in Kenya [Okamoto et al, 2019], genotype D was discovered in Tunisia [Kheirabad et al, 2017], genotypes (A-D) have been found within South Africa [Toyé et al, 2021], and genotype E was discovered in Nigeria [Fasola et al, 2021].…”