Repression and activation of the genome of herpes simplex viruses in human cells.

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Abstract
A cell culture system in which the herpes simplex virus (HSV) type 2 (HSV-2) genome is maintained in a repressed form after treatment of infected cells with 1-.beta.-D-arabinofuranosylcytosine and increase of incubation temperature from 37.degree. C to 39.5.degree. C was previously described. Infectious HSV-2 production was activated by altering incubation temperature or by superinfecting with human cytomegalovirus. The establishment of an analogous system utilizing HSV type 1 (HSV-1) is now reported. Human embryo lung cells were infected with HSV-1 and treated with 1-.beta.-D-arabinofuranosylcytosine (25 .mu.g/ml) for 7 days to minimize synthesis of virus DNA and infectious virus while allowing expression of early virus genes. HSV-1 was maintained in an undetectable form for at least 72 days when the incubation temperature was raised from 37.degree. C to 40.5.degree. C after removal of the inhibitor. HSV-1 gene expression was then predictably turned on by superinfection with human cytomegalovirus or by reducing the incubation temperature. Virus replicated after activation was compared with the respective parental virus with regard to inhibition by the HSV-1-specific antiviral (E)-5-(2-bromovinyl)-2''-deoxyuridine and EcoRI, HindIII and Xba I restriction endonuclease cleavage patterns. Activation of HSV gene expression in human cells by a human cytomegalovirus early gene function(s), followed by synthesis of parental-like HSV, was shown.