Biological Activities of Sonically Treated Sendai Virus

Abstract

SUMMARY Sendai virus induced fusion of Ehrlich ascites tumour cells but this capacity was decreased by sonic treatment and the product then interfered with virus-induced fusion. Sucrose density gradient fractionation of the sonic product showed that the capacity for fusion resided in intact particles and the interfering effect in fragments of the virus envelope. Such fractionation also showed that haemolytic activity was restricted to intact particles or to large envelope fragments, while haemagglutination is found with large or small fragments. However, envelope fragments, with haemolytic activity, induced fusion in cell monolayers with little or no inhibitory effect. Envelope fragments complexed with antibody lose their capacity to inhibit fusion and show no capacity for fusion of Ehrlich ascites tumour cells. These findings, and studies by electron microscopy on interactions of envelope fragments to cells, support the hypothesis that the fusion of suspended cells depends on the strength of contact between cells induced by virus components with haemolytic activity.