Decrease of Sensitivity to Interferon in Cells Infected by Murine Leukemia-Sarcoma Viruses

Summary

Mouse cells chronically or acutely infected with different murine leukemia-sarcoma viruses (Rauscher, Moloney) had a decreased sensitivity to interferon (DSI), whether the interferon was exogenous or self produced after induction with Newcastle disease virus. The relationship of DSI to actual infection by Moloney murine sarcoma virus (MSV-M) was ascertained by specific virus neutralization and physical inactivation of the virus. DSI, which did not depend on the type of challenge virus testing interferon activity, began 3 hours after the end of MSV-M adsorption and was clearly established after 6 hours. It was observed both when MSV-M was inoculated before treatment of cells by interferon or after cells were submitted to the action of interferon for 8 hours. The phenomenon was not related to direct inhibitory action of the viral preparations, loss of the protective state due to accelerated cell growth, influence of viral replication on protein synthesis by cells, or stimulation of challenge virus multiplication. No substance counteracting the action of interferon was found in MSV-M-infected cells. The murine leukemia-sarcoma viruses may work against the postulated translation inhibitory protein, perhaps at the level of its mRNA.