HEPATITIS-C VIRUS VARIANTS FROM VIETNAM ARE CLASSIFIABLE INTO THE 7TH, 8TH, AND 9TH MAJOR GENETIC GROUPS

Thirty-four (41%) of 83 hepatitis C virus (HCV) isolates from commerci al blood donors in Vietnam were not classifiable into genotype I/1a, I I/1b, III/2a, IV/2b, or V/3a; for 15 of them, the sequence was determi ned for 1.6 kb in the 5'-terminal region and 1.1 kb in the 3'-terminal region. Comparison of the 15 Vietnamese isolates among themselves and with reported full or partial HCV genomic sequences indicated that th ey were classifiable into four major groups (groups 6-9) divided into six genotypes (6a, 7a, 7b, 8a, 8b, and 9a). Vietnamese HCV isolates of genotypes 7a, 7b, 8a, 8b, and 9a were significantly different from th ose classified into groups 4, 5, and 6 based on divergence within part ial sequences; those of genotype 6a were homologous to a Hong Kong iso late (HK2) of genotype 6a. Phylogenetic trees based on the envelope 1 (E1) gene (576 bp) of 55 isolates and a part of the nonstructural 5 (N S5) region (1093 bp) of 43 isolates revealed at least nine major group s, three of which (groups 7, 8, and 9) were identified only in Vietnam ese blood donors. With a prospect that many more HCV isolates with sig nificant sequence divergence will be reported from all over the world, the domain of the HCV genome to be compared and criteria for grouping /typing and genotyping/subtyping will have to be determined, so that t hey may be correlated with virological, epidemiological, and clinical characteristics.