Nine additional complete genome sequences of HCV genotype 6 from Vietnam including new subtypes 6xb and 6xc

- We characterized nine full-length genomes of HCV-6 in Ho Chi Minh City, Vietnam.
- They may represent six new subtype candidates beyond the assigned 24: 6a-6xa.
- Co-analysis of sequences in ORF length indicates the existence of 20 such lineages.
- Further analysis of the references in the NS5B region identified additional 22.
- Following the eXtended format, we assigned two new subtypes, 6xb and 6xc.

We completely sequenced nine HCV-6 variants from Vietnam. They are grouped into six lineages beyond the 24 assigned subtypes, 6a-6xa, and 14 unclassified lineages that have been recently described with full-length genomes. Co-analysis with reference sequences in the NS5B region identified additional 22 such lineages, which made the total taxonomic number of HCV-6 increased to 66 that might be recognized at the subtype level. Because two of these six lineages revealed in this study each had >3 epidemiologically unlinked isolates identified, we proposed to assign them new subtypes 6xb and 6xc in following the eXtended format recently recommended in the expanded HCV nomenclature.