Replication of Sendai Virus

Abstract

Chick embryo fibroblast cultures infected with Sendai virus were incubated with 3 H-uridine in the presence of actinomycin D beginning at 18 hr after infection. The 35 and 18 S virus-specific ribonucleic acid (RNA) components were found in a ribonuclease-sensitive form in the cell and appeared to be associated with polyribosomes. Newly synthesized 57 S viral RNA was rapidly coated with protein to form intracellular viral nucleocapsid, and no 57 S RNA was found “free” (ribonucleasesensitive) in the 2,000 × g supernatant fraction of disrupted cells. The nucleocapsid from detergent-disrupted Sendai virus and that from disrupted cells were indistinguishable in ultrastructure and buoyant density, and neither was found to be infectious or have hemagglutinating activity. Kinetic studies of nucleocapsid and virus formation indicated a relative block in conversion of viral nucleocapsid to complete enveloped virus in these cells, resulting in accumulation of large amounts of nucleocapsid in the cell cytoplasm.