Herpes simplex virus latency in SV40 hamster tumour cells

Incubation of SV40 tumor cell cultures with herpes simplex virus type 2 (HSV 2) at 40°C resulted in rapidly growing cells which survived the infection and lacked both virus cytopathology and synthesis of detectable infectious virus. Following transfer to 37°C, infectious HSV 2 reappeared and persistent infection of cells developed without complete destruction of the cell line. There was, however, a delay of at least 8 to 22 days following transfer to 37°C before infectious virus could be detected. HSV specific immunofluorescent antigens were present in every cell during latency. The reappearance of infectious HSV 2 went parallel with focal cytopathogenic changes. The period between the disappearance and reappearance of infectious virus is considered the latent period. Cultures in this period were less sensitive to superinfection with herpes simplex virus type 2 than control cultures. The reappearance of infectious HSV 2 after prolonged incubation of infected culture at 40°C and 37°C indicates that HSV 2 can remain associated with the cells in a non infectious form for long periods without being degraded.