Genotypes of hepatitis C virus in Nigeria.

A pilot survey of hepatitis C virus (HCV) infection in Nigeria was carried out on healthy adult blood donors and children of preschool age. Sixteen of 200 (8%) donors were positive for antibodies using a second generation enzyme-linked immunosorbent assay (ELISA) but all of the children were negative. Supplementary testing of the ELISA-positives using a recombinant immunoblot assay (RIBA-2) confirmed the presence of antibody in four and two others were indeterminate. Four of the anti-HCV-positive sera and one found positive by ELISA but which was negative by RIBA-2 were found to be positive for HCV RNA using reverse transcriptase-polymerase chain reaction (RT-PCR) and primers specific for the 5' untranslated region (5'UTR) of the HCV genome. The NS5 and core regions also were amplified and the PCR products from all three regions were sequenced. Sequences from the 5'UTR could be divided into two groups: one group comprised three isolates with greater than 95% sequence identity with published sequences of genotype 1 and the other comprised two isolates with greater than 93% sequence identity with genotype 4. Analysis of three sequences amplified from the NS5 region confirmed this assignment to genotypes 1 and 4. Pairwise comparisons of the NS5 region sequences with representatives of 1a, 1b, 1c (for the first group) and 4a-4h (for the second group) show the first group to include subtypes classifiable as 1a and a novel sequence and the second group to include a novel sequence within genotype 4. Sequence analysis of the core region was consistent with this interpretation. These data confirm the presence of at least two major HCV genotypes in Nigeria (genotypes 1 and 4) and we report two novel sequences which have been designated provisionally as genotypes 1d and 4i.