Role of Interferon in Six Cell Lines Persistently Infected with Rubella Virus

Presistent infections with rubella virus were established in baby hamster kidney, BSC-1, HeLa, RK-13, rabbit embryo chondrocyte, and Vero cell lines. All of the cultures except Vero continually produced rubella virus and interferon to which the virus was sensitive. Concurrently, only the Vero cells did not display interference against superinfection with Newcastle disease and vesicular stomatitis viruses. The addition of 1,000 U of exogenous interferon to the cultures cured only the rabbit embryo and Vero cells of the persistent infection. That the interferon is not required for the initiation and maintenance of rubella viral persistence in vitro is implied by the following. (1) Vero cells were persistently infected in the absence of interferon; (2) actinomycin D or cortisone inhibited interferon synthesis but not the rubella viral infection; and (3) cells continuously cultured in the presence of cortisone maintained a viral persistence without interferon synthesis. On the other hand, interferon seems to be responsible for the viral interference; Vero cells infected with rubella virus and cultures inoculated with rubella virus in the presence of actinomycin D or cortisone did not display interference against Newcastle disease or vesicular stomatitis viruses.