ASSEMBLY OF ENVELOPED RESPIRATORY SYNCYTIAL VIRUS-PARTICLES WITHIN THE CYTOPLASM OF INFECTED VERO CELLS

Electron microscopic examination of syncytia induced by a bovine respi ratory syncytial virus strain in Vero cell cultures revealed the prese nce in the cytoplasm of assembled enveloped virus particles within inc lusions of variable sizes. Moreover, budding virus particles were show n occasionally in the intracytoplasmic vesicles. These particles were filamentous in form, about 80-120 nm in diameter, variable in length, containing 12 nm diameter nucleocapsids, and looked like the extracell ular particles budding at the plasma membranes. This is the first repo rt on assembly of intracellular virus particles in cells infected by a member of the family Paramyxoviridae. Vero cell-dependent variations appear to be the factor leading to the defect in the late virus replic ation cycle.