Persistent Infection of L Cells With Polyoma Virus: Periodic Destruction and Repopulation of the Cultures

Summary

Persistent infection with polyoma virus was established in monolayers of several lines of Earle's L cells. Such infection was unusual in that it led periodically to extensive cellular destruction and repopulation of the cultures with concomitant increases and decreases of infected cells as determined by immunofluorescence. Soon after primary infection and at the beginning of recovery periods nuclear fluorescence was prominent, whereas during stages of cultural degeneration cytoplasmic staining was preponderant. Cells containing viral antigen tended to occur in foci, which suggested that the infection is spread partly by contact. Addition of antipolyoma serum to carrier populations improved their appearance and rapidly reduced the incidence of staining cells, but final cures were achieved only after months of continuous treatment. The yields of virus per infected cell were similar to those observed in mouse embryo cultures. Monodispersed suspended L cells failed to support persistent infection. Carrier cultures showed slight degrees of resistance to superinfection with Newcastle disease and influenza A viruses, but none to the virus of vesicular stomatitis. No interferon was detectable. Attempts to overcome the partial resistance by manipulations, reported to reduce interference and interferon action, failed. Addition of interfering preparations of ultraviolet-inactivated Newcastle disease virus or of a potent interferon had some beneficial effect but did not establish a stable equilibrium, and fluctuations in the incidence of polyoma-infected cells continued. While an interaction of interference and interferon in this system has not been irrefutably excluded, other undetermined factors probably are involved in maintenance of the persistent infection.