SUMMARYThe restriction endonuclease (RE) cleavage patterns of the DNA of herpes simplex virus (HSV) genital isolates from two geographically distinct groups and from one group of facial isolates were examined. Eleven of 21 genital isolates from females, 1 of 27 genital isolates from males and all 17 of the facial isolates were HSV type 1 (HSV-I). The groups of isolates of the same serotype could not be distinguished by significant differences in the frequency of variable restriction endonuclease sites or molecular weight of variable length fragments. Simultaneous consideration of two or more variable sites has disclosed some which are apparently correlated in the HSV-I isolates, and which could provide a useful marker for phylogenetic relationships. However, most pairs showed no correlation, while certain sites appeared more closely correlated in the genital than in the facial isolates. All 39 HSV-2 isolates could be distinguished from each other on the basis of a combination of variable RE sites and variable length fragments. BglII RE sites appeared less variable than other RE sites.

SUMMARYThe distribution of restriction endonuclease (RE) sites was compared for 84 herpes simplex virus type 1 (HSV-1) isolates obtained from the ganglia, facial lesions, genital lesions and from brain tissue from herpes encephalitis cases. The isolates came from Canada, the U.K., the U.S.A. and Japan. Out of a total of 224 sites identified, 87 were variable. Three of the 30 most variable sites were at significantly (P < 0-05) different frequencies in groups of isolates from distinct anatomical sites of isolation; one of these, and a further two sites, were at significantly different frequencies in groups from distinct geographical origins. There are at least two inter-related linkage groups. However, most of the site combinations appear to be random. The variability of RE sites in contiguous genome segments, which include both non-coding and coding sequences, show a marked heterogeneity, indicating that some viral gene sequences are more variable than others. The three RE sites at different frequencies in viral groups from distinct anatomical sites of isolation are in two genome segments : map units 27 to 35 and 50 to 57. We infer from the observed associations with anatomical site of viral isolation that part of at least one of these segments may modulate viral virulence in man following infection.

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