CLASSIFICATION OF HEPATITIS-C VIRUSES BASED ON PHYLOGENETIC ANALYSIS OF THE ENVELOPE-1 AND NONSTRUCTURAL 5B REGIONS AND IDENTIFICATION OF 5ADDITIONAL SUBTYPES

Genotyping of hepatitis C virus-positive sera by means of a line probe assay indicated that <3 % of European samples, but up to 30% of Gabon ese sera, could not be classified as either 1a, 1b, 2a, 2b, 3a, 3b, 4c , 5a, or 6a. Such samples were analyzed in the 5' untranslated region and in the nonstructural 5 (NS5) region. Classification based on phylo genetic analysis of the commonly used 222-bp-long NS5B region was poss ible for most but not all of the selected sera. Therefore, the core/en velope 1 region (579 bp) and a larger NS5B (340 bp) region were also a nalyzed. Only the phylogenetic analysis of the 340-bp NS5B region of t hese newly identified and published isolates provided unambiguous clas sification into types and subtypes. Furthermore, unequivocal evidence for four subtypes in type 2 and eight subtypes in type 4 was provided. A specific recognition sequence in the 5' untranslated region was obs erved for every newly identified subtype. Based on 1830 pair-wise comp arisons in NS5B, isolates belonging to the same subtype showed evoluti onary distances of <0.127 and isolates of the same type exhibited evol utionary distances of <0.328. These phylogenetic border distances can be conveniently used for classification of hepatitis C virus isolates into types and subtypes.