Slow evolutionary rate of GB virus C hepatitis G virus

With the aim of elucidating evolutionary features of GB virus C/hepatitis G virus (GBV-C/HGV), molecular evolutionary analyses were conducted using th e entire coding region of this virus. In particular, the rate of nucleotide substitution for this virus was estimated to be less than 9.0 x 10(-6) per site per year, which was much slower than those for other RNA viruses. The phylogenetic tree reconstructed for GBV-C/HGV, by using GB virus A (GBV-A) as outgroup, indicated that there were three major clusters (the HG, GB, a nd Asian types) in GBV-C/HGV, and the divergence between the ancestor of GB - and Asian-type strains and that of HG-type strains first took place more than 7000-10,000 years ago, The slow evolutionary rate for GBV-C/HGV sugges ted that this virus cannot escape from the immune response of the host by m eans of producing escape mutants, implying that it may have evolved other s ystems for persistent infection.