Identification of a novel hepatitis E virus in Nigeria

Sporadic cases of acute hepatitis E among ten native Nigerian adults were r eported in Port-Harcourt (Nigeria). Hepatitis E virus (HEV) was detected in serum and/or faecal samples of seven patients by RT-PCR of the open readin g frame (ORF)-1 polymerase region and the 3'-end of ORF2. Restriction analy sis widely used to distinguish genotypes I and III showed that all Nigerian strains have a pattern similar to the Mexican strain (Notl, nt 286; Smal, nt 397; no Kpnl restriction site) but displayed a Bsml restriction site at nt 213 as do most African HEV strains sequenced so far. Sequence analysis p erformed from internal ORF1 and ORF2 PCR products displayed strong homogene ity between the HEV isolates, determining a regional cluster. Phylogenetic analysis of nucleotide sequences revealed that these strains were more rela ted to the Mexican prototype genotype III (87% homology in ORF1, 80% homolo gy in QRF2) than to either the African strain genotype I (74% homology in O RF1, 77% homology in ORF2) or the USA strain genotype II (75% homology in O RF1, 77% homology in ORF2), Genetic divergence up to 15% in ORF2 with the M exican genotype clearly defined a new subgenotype within genotype III. At t he amino acid level, Nigerian strains showed more homology with genotype II I (96%) than with genotype I (92%). This study clearly determined the co-ex istence of genotypes I and III in Africa, These Nigerian HEV strains belong ing to genotype III, but sharing some properties with genotype I, could be one of the missing links between African and Latin American HEV and could h elp us to determine the phylogenetic evolution of HEV from the ancestral vi rus.