Identification of hepatitis B virus subgenotype A3 in rural Gabon

An hepatitis B virus (HBV) molecular survey was conducted in five remote villages in the equatorial forest in Gabon, Central Africa. Two hundred seventy out of 311 inhabitants (86.8%) were HBV‐infected or had evidence of past HBV infection. Chronic hepatitis corresponding to hepatitis B surface antigen (HBsAg) positivity was suspected in 27 (8.6%) of the HBV‐infected subjects. High HBV viral loads were detected mainly in children aged 4–7 years. The pre‐S/S domains were sequenced in 13 cases and 12 strains belonged to HBV‐A genotype. In one case we found evidence for recombination between genotypes A and E. Phylogenetic analysis revealed that Gabonese HBV strains were distinct from HBV‐A subgenotypes (A1 and A2). These new HBV strains from Gabon clustered with previously reported HBV‐A3 subgenotype strains from Cameroon and Democratic Republic of Congo. The analysis of the pre‐S2 domain allowed us to determine two amino acid substitutions (N/152/S and N/174/T) specific to the Central African HBV‐A3 subgenotype strains and one amino acid substitution (P/155/Q) unique to these new Gabonese HBV‐A3 subgenotype isolates. Two full genome sequences of two new Gabonese HBV isolates are also presented and confirm the distinctive HBV‐Gab‐A3 cluster. J. Med. Virol. 78:1175–1184, 2006. © 2006 Wiley‐Liss, Inc.