Interferon has no protective effect during acute or persistent reovirus infection of mouse SC1 fibroblasts

Mouse SC1 fibroblasts can support reovirus multiplication although they exhibit a partial resistance to viral-induced cytopathology; a significant percentage of infected SC1 cells can remain viable while becoming persistently infected by the virus. In the present study, the possible role of interferon on the fate of reovirus-infected cells was investigated. Treatment of mouse L fibroblasts with β-interferon resulted in a reduced viral efficiency of plating while essentially no effect was observed on SC1 cells; the results were similar with the unrelated encephalomyocarditis virus. This suggests that the interferon-regulated pathways are somehow deficient in SC1 cells even though these cells do respond to interferon treatment, as evidenced by an increase in the level of active interferon-inducible protein kinase double-stranded RNA-dependent (PKR) enzyme. Persistently infected SC1 cells constitutively release interferon even though treatment with anti-interferon antiserum suggests that interferon presence is unrelated to maintenance of the persistent state. The possible significance of the correlation between the lack of interferon-induced antiviral effect and relative resistance of SC1 cells to vieal-induced cytopathology is briefly discussed.