Induced Latent Infection of Monkeys with Vacuolating SV-40 Papova Virus. Virus in Kidneys and Urine. ∗

Summary

A latent infection was induced by exposure of African primates by a variety of routes to the vacuolating SV-40 virus, the simian member of the papova virus group. Virus multiplied in the green monkey Cercopithecus aethiops more abundantly than in the baboon Papio doguera, without inducing an apparent illness in either species. Early in the infection SV-40 was found in the urine, with 18 isolations obtained among the 26 specimens collected from 10 green monkeys in the first 4 weeks after infection. The titer of the urine was as high as 10^6.5 TCD₅₀/ml. Virus was recovered from the urine of all 4 baboons inoculated parenterally, but not from 3 baboons infected by intranasal or oral administration of virus. Later in the course of the infection when viruria was waning, neutralizing antibodies appeared in the urine (as well as in the blood). Of 18 late urine specimens which were negative for virus, 16 were positive in neutralization tests. Three to 8 months after infection, when virus was no longer recoverable from the urine, kidney biopsies were obtained. Part of each biopsy was tested for virus by the conventional method of inoculating ground tissue fragments into susceptible green monkey cultures, but not a single positive was obtained. However a number of biopsies yielded virus when they were grown as explants in tissue culture. Positive biopsy cultures spontaneously developed vacuolating type of degeneration and virus was then readily detected by passage. Kidneys from 5 of 8 green monkeys tested yielded virus by this method 3 months after infection was initiated. This latent infection persisted and a second biopsy 6 to 8 months after infection was positive in 4 of the 5 previously positive monkeys. Only 1 of 6 baboon kidneys yielded virus, again by the biopsy explant procedure.