Suppressive Effects of Interferon on Cell Fusion by Sendal Virus

Suppressive ffects of human IFN-ct, IFN-fl and mouse-IFN on syncytium formation in human and mouse transformed cells have been studied using u.v.-irradiated Sendai virus (UV-Sendai virus). After treatment of human RSa cells with 500 units/ml human IFN<z for 16 h, the syncytium formation induced by UV-Sendai virus was reduced to less than 10 % of controls. The suppressive effect was dependent on the amount of interferon added, and it was blocked by the addition of cycloheximide. Suppression of syncytium formation was also observed on human IF r cells, which are partially resistant to the anticellular effect of interferon but are sensitive to the antiviral effect of interferon. Human IFN-fl also had a suppressive effect on syncytium formation in human transformed cells, and human IFN-tL IFN-fl and mouse IFN showed species specificity in their effect on fusion. This anti-cell fusion activity was developed in IF r cells from about 5 h after addition of IFN-ct and when the cells were treated with IFN- ~ for 16 h, the resistant state of cells continued for over 20 h after removal of IFN<t