A novel subtype of GB virus C/hepatitis G virus genotype 1 detected uniquely in patients with hemophilia in Japan.

GB virus C (GBV-C) or hepatitis G virus (HGV) has been transmitted to Japanese patients with hemophilia through the frequent use of unheated blood products. Sequence analysis showed that most of the viruses isolated from these patients belonged to GBV-C/HGV genotype 1, which is usually found in persons from Africa. This may point to the origin of this virus in Japanese patients with hemophilia. The phylogeny of 11 GBV-C/HGV isolates from Japanese patients with hemophilia was investigated by a detailed analysis with a fragment spanning from the 5' non-coding region to part of the E1 gene. Except for one that belonged to the genotype 3 cluster, all isolates were GBV-C/HGV type 1. Five main clades exist within the GBV-C/HGV genotype 1 sequences. These isolates are grouped in 2 defined clades. Three of the isolates are clustered in subtype 1c clade whereas the other 7 strains formed a new statistically well-supported monophyletic group (named subtype 1e). Our results suggest that GBV-C/HGV type 1 can at present be classified into at least 5 clades and in this group a majority of Japanese patients with hemophilia was infected with a GBV-C/HGV of a unique and newly described subtype within genotype 1.