Genome variations in herpes simplex virus type 2 strains isolated in Japan and Sweden

One-hundred and twenty-three epidemiologically unrelated strains of herpes simplex virus type 2 (HSV-2) isolated in Japan and Sweden (68 Japanese and 55 Swedish isolates) were compared by analysis of their genomes using five restriction endonucleases: BamHI, KpnI, EcoRI, HindIII and Bg/II. Seven of the 93 restriction sites examined showed statistically significant variation between isolates from the two countries. However, HSV-2 isolates were less variable than the HSV-1 isolates previously analysed from the same countries. Using 12 restriction sites as markers, the HSV-2 isolates were classified into 41 cleavage patterns; 17 were specific for Japanese isolates and 15 were specific for Swedish isolates. Correlation coefficients between some sets of 12 markers were significant, but significant correlations between Japanese and Swedish isolates were distinct for each country. Both Japanese and Swedish isolates were assigned to three major patterns with no significant difference in incidence. In contrast, in two other major patterns, differences in incidence between the isolates were statistically significant. These results suggest that HSV-2 populations in geographically separated countries have distinct cleavage site distributions.