Genetic retrieval of viral genome sequences from herpes simplex virus transformed cells

Oncogenic transformation of cultured cells by inactivated herpes simplex virus (HSV) types 1 and 2 has been demonstrated1–12. Expression of HSV information in these transformed cells has been shown by immunofluorescence studies2,6,8,13–15, detection of HSV neutralizing antibody in sera from tumour-bearing animals1,4,7,11,12 and by hybridization of HSV-specific RNA16–18. Molecular hybridization studies of DNA from HSV-2 transformed hamster cells have detected up to 40% of the HSV genome present in several copies16,19,20. Complementation of three HSV-2 temperature-sensitive mutants when superinfecting the RE1 rat embryo cell line21 (transformed by the HSV-2 temperature-sensitive mutant ts122) suggests that resident viral genes can be expressed. Brown et al.23 used a similar approach to detect HSV information latent in human ganglia. We report here retrieval of intertypic HSV recombinants from HSV transformed cells after superinfection with ts mutants of the alternative serotype of HSV. Restriction enzyme analysis which clearly differentiates between HSV-1 and HSV-2 DNA24,25 has demonstrated the isolation of recombinants spanning the genome and of virus indistinguishable from the original transforming virus.