THE ENTIRE NUCLEOTIDE-SEQUENCES OF 3 HEPATITIS-C VIRUS ISOLATES IN GENETIC GROUPS 7-9 AND COMPARISON WITH THOSE IN THE OTHER 8 GENETIC GROUPS

We have proposed that hepatitis C virus should be classified into elev en genetic groups (types) which further divide into more than 80 genot ypes (subtypes). However, only eight genetic groups (1-6, 10 and 1 1) have been defined on the basis of the full-length sequence, Hence, the entire nucleotide sequences of three HCV isolates in genetic groups 7 -9 have now been determined. Phylogenetic analysis :over the full-leng th sequences of these three isolates, along with 30 more in the other eight genetic groups, indicated that genetic groups 6-9 and 11 have bi furcated from a common branch and groups 3 and 10 from another. In the former branch groups 7 and 11, and groups 8 and 9, are closely relate d. Consequently, HCV can be classified into either eleven (1-1 1) or s ix groups (1; 2; 3 and 10; 4; 5; 6-9 and 11), allowing a clear separat ion of group and genotype similarity within the NS5b region or a subre gion of 1093 nt, When painwise comparison of 1093 nt in the NSSb seque nce was performed on 106 HCV isolates of 36 genotypes in eleven geneti c groups, they were classified into either eleven (1-11) or six (1; 2; 3 and 10; 4; 5; 6-9 and Il)genetic groups, However, group and genotyp e similarities were not clearly separable in either classification, Th e overlapping range was smaller using the classification into eleven g enetic groups as compared to six genetic groups (2 .7 vs 4.7%). These results indicate that HCV might not have evolved in the two-tiered fas hion, at least in a strict sense.