Identification of a single genotype of hepatitis G virus by comparison of one complete genome from a healthy carrier with eight from patients with hepatitis.

Different isolates of a putative hepatitis virus called hepatitis GB virus C or hepatitis G virus (HGV) have been cloned recently from patients with hepatitis. This virus has also been found commonly in healthy carriers. We have cloned and sequenced a complete HGV genome, designated HGVCN, from a healthy Chinese blood donor. HGVCN shares 85.8-90.0% nucleotide sequence identity and 95.4-97.5% amino acid identity with the eight available full-length HGV genomes. Furthermore, the majority (82.8%) of the nucleotide substitutions found in HGVCN were synonymous and a fairly uniform distribution of changes was found across the entire genome without identification of any hypervariable region. When compared with the African isolates GBVC and GBVC-EA, the HGVCN-encoded polyprotein contained a 31 amino acid N-terminal extension which was predicted to be a defective core-like sequence. The sequences of the HGV E1 and E2 proteins displayed unique motifs and were highly conserved. Phylogenetic analysis revealed that all nine complete HGV isolates were closely related and that HGVCN grouped with the other Chinese HGV isolate (HGVC964). Taken together, our findings suggest that there is one single genotype of HGV and that the HGV genome cloned from the healthy carrier is not significantly different from those derived from patient sera.