Use of sequence analysis of the NS5B region for routine genotyping of hepatitis C virus with reference to C/E1 and 5′ untranslated region sequences

Nucleotide sequence analysis of the NS5B region was performed to identify genotypes of 8,479 hepatitis C virus (HCV) RNA-positive patient samples collected in the Canadian province of Quebec. Genotypes could be determined for 97.3% of patients. Genotypes 1 to 6 were found in 59.4, 9.0, 25.7, 3.6, 0.6, and 1.8% of patients, respectively. Two isolates did not classify within the six genotypes. The subtype 1 distribution was 76.7% la, 22.6% 1b, and 0.7% others, while the subtype 2 distribution was 31.8% 2a, 47.6% 2b, 10.9% 2c, 4.1% 2i, and 5.6% others. Subtype 3a accounted for 99.1% of genotype 3 strains, while all genotype 5 samples were of subtype 5a. The subtype 4 distribution was 39.2% 4a, 15.4% 4k, 11.6% 4d, 10.2% 4r, and 23.6% others. The subtype 6 distribution was 40.4% 6e, 20.5% 6a, and 39.1% others. The 5' untranslated region (5'UTR) sequences of subtype 6e were indistinguishable from those of genotype 1. All samples that did not classify within the established subtypes were also sequenced in C/E1 and 5'UTR. C/E1 phylogenetic reconstructions were analogous to those of NS5B. The sequences identified in this study allowed the provisional assignments of subtypes 1j, 1k, 2m, 2r, 3i, 4q, 6q, 6r, and 6s. Sixty-four (0.8%) isolates classifying within genotypes 1 to 6 could not be assigned to one of the recognized subtypes. Our results show that genotyping of HCV by nucleotide sequence analysis of NS5B is efficient, allows the accurate discrimination of subtypes, and is an effective tool for studying the molecular epidemiology of HCV.