Molecular characterization of hepatitis A virus isolates from Nigeria.

OBJECTIVE Despite the endemicity of hepatitis A virus (HAV) in Nigeria, genetic information on the HAV genotypes/subgenotypes circulating in the country remains unknown. The objective of this study was to investigate HAV strains using molecular epidemiological and genetic analyses among apparently healthy adult Nigerian subjects. METHODS Testing for HAV-RNA was performed on 114 serum samples by the reverse transcription-polymerase chain reaction and sequenced with primers encompassing the VP1/P2A junction. RESULTS Twelve serum samples tested were found to be HAV-RNA positive. Phylogenetic analysis revealed that all 12 HAV isolates were classified as subgenotype IA exhibiting 98.3% nucleotide identity. Interestingly, the Nigerian HAV/IA subgenotype consisted of two distinct genomic sublineages with a unique majority (n = 11) corresponding to strains endemic in Cameroon and the other (n = 1) shows a probable link with European sequences. Predicted conserved amino acid sequences and the few deduced substitution in the VP1/P2A junction might play a role in the development of a novel Nigerian-Cameroon sublineage within the HAV/IA subgenotype and might explain the stability of HAV/IA in this subregion. CONCLUSION This study reveals the development of a new HAV/IA sublineage in the Nigerian-Cameroon subregion. The presence of a single subgenotype indicates that this HAV strain has been predominantly circulating in Nigeria.