[Molecular-epidemiological and phylogenic analysis of herpes simplex virus type 1 from seven areas in Japan]

Two-hundred and seventy-five epidemiologically unrelated herpes simplex virus type 1 (HVS-1) strains isolated from seven areas (Sapporo, Akita, Nagoya, Kyoto, Tottori, Kagawa and Kurume) in Japan were compared with the standard laboratory strain F, based on cleavage analysis of HSV-1 DNAs with three restriction endonucleases, BamHI, KpnI and SalI. The results obtained were as follows: 1) Using gains and losses of 19 cleavage sites selected from 114 sites, the total of 275 strains could be classified into 87 distinct cleavage patterns. Also, it was found that the isolates were clustered in four predominant patterns, the pattern 27, 6, and 76, containing 62, 24, 15 and 12 strains, respectively. 2) There were highly significant differences in the incidence of isolates classified into the pattern 27 that were obtained in Kagawa as compared with those in Sapporo, Akita, Nagoya and Kurume, and those in Tottori as compared with those in Sapporo, Akita, Nagoya and Kurume. There was also a significant difference in the incidence of isolates classified into the pattern 76 that were obtained in Kagawa as compared with those isolated in Kurume. 3) There were significant correlation coefficients (p less than 0.05) between some stets, e.g. loss of the site between A and A' and gain of a site in A cleaved with BamHI, in every pair of 18 cleavage sites. 4) The phylogenic tree of 87 patterns based on genomic similarities of the Japanese HSV-1 isolates was established, and it was considered that HSV-1 isolates from Japanese could be phylogenetically classified into two to six major groups. These results suggest that HSV-1 strains have mutated and evolved independently by the transmission of the viruses among geographically separated hosts over an extremely long period, and that the genetically characteristic variants have accumulated and persisted in the present Japanese population.