Deletions and recombinations in the core region of hepatitis B virus genotype E strains from asymptomatic blood donors in Guinea, west Africa

Abstract

The prevalence of hepatitis B virus (HBV) surface antigen (HBsAg) chronic carriage in west Africa is the highest in the world, but its molecular epidemiology remains relatively poorly investigated. Plasma samples from random asymptomatic carriers of HBsAg in Conakry, Guinea, were studied and the complete genome sequences of 81 strains were obtained. Three additional samples from Kumasi, Ghana, were also included in the analysis. Phylogenetic analyses confirmed the dominance of genotype E (95.1%), including 8.6% of strains (viral load, 5x10(3)-2.6x10(8) IU ml(-1)) comprising dominant variants with large deletions in the core region and minority wild-type variants. The presence of two different patterns of deletions in two and four donors suggested targeted genome fragility between nt 1979 and 2314. The remaining sequences included one subgenotype A3 (1%) and six A/E recombinant forms (4-7%). A/E strains with identical points of recombination in three donors suggested strongly that these recombinant HBV strains are circulating and transmitted in the population. Recombination points were concentrated in the core gene. The detection of similar A/E recombinant strains in Ghana suggested a geographical extension of recombinant HBV to the region. The quasispecies of one additional Ghanaian strain sequenced in the pre-surface/surface region resolved into dominant clones of either the A or E genotype, but also three different patterns of A/E recombinant variants. The observation that both deletions of genotype E strains and A/E recombination points are mostly located in the core gene at specific positions indicates a region of the genome where genetic rearrangements preferentially take place.