Herpes simplex virus latency in tissue culture cells

We have developed tissue culture systems which mimic certain aspects of herpes simplex virus (HSV) latency, in order to facilitate molecular studies of the phenomenon. The initial approach utilised incubation at 42 degrees C to suppress virus replication and establish stable latency after infection of human fibroblasts at low multiplicity with HSV-2. Latent virus was reactivated efficiently by superinfection of cultures with HSV-1 or human cytomegalovirus. Improvement of the system was achieved by use of the HSV-1 mutant in1814, which has a 12 base pair insertion in the coding sequences for the transactivating protein Vmw65 (VP16). Upon infection with in1814 at 42 degrees, or 37 degrees, it was possible to obtain cultures in which up to 21% of cells contained a viral genome. More recent modifications include the use of mutant in1820 (a derivative of in 1814) and pretreatment of cells with interferon alpha, which enable latency to be established in approximately 100% of cells. A system has therefore been developed that is suitable for the analysis of gene expression and genome structure during latency and reactivation.