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.