GENETIC DIVERSITY BETWEEN HEPATITIS-G VIRUS ISOLATES - ANALYSIS OF NUCLEOTIDE VARIATION IN THE NS-3 AND PUTATIVE CORE PEPTIDE GENES

Significant variation was found, between 46 isolates of hepatitis G vi rus (HGV), following direct sequencing of subgenomic PCR fragments fro m either or both the NS-3 and putative 'core' peptide. Nucleotide sequ ences of most HGV NS-3 fragments varied by 10-30% and of most putative 'core' peptide fragments by 2-20%. HGV was therefore shown to be much less variable than hepatitis C virus (HCV) and pairwise comparisons o f HGV sequences demonstrated a single distinct distribution of evoluti onary distances. Construction of phylogenetic trees, boot-strap analys is and calculation of mean distances between possible subtypes also in dicated one level of variation between HGV NS-3 and putative 'core' pe ptide sequences, and the suggested degree of variation between isolate s was similar to that between HCV subtypes. No evidence for clustering of sequences into multiple subtypes or genotypes was found. Although very small subgenomic fragments of HCV are indicative of the viral gen otype it seems that the assignment of genetic groups is not possible f or HGV using such small subgenomic fragments. The relatively limited g enetic variation observed in HGV may reflect a relatively low level of host selection pressure stemming from the low level of host immunity stimulated by this virus.