morphogenesis and cytopathology of bovine parainfluenza type 3 virus

Department of Microbiology, School of Hygiene, University of Toronto, Toronto, Canada The structure of bovine parainfluenza type 3 virus (strain SF -4) was found to be indistinguishable from that of other paramyxoviruses. Negatively stained virus particles had an overall diameter ranging from 280 to 580 nm. and a nucleocapsid diameter of 17 to 19 nm. By light microscopy, SF -4-infected LLC-MK2 cells showed eosinophilic cytoplasmic inclusions, followed later by eosinophilic nuclear inclusions. By electron microscopy, aggregates of nucleocapsid-like filaments were seen in the cytoplasm and nucleus. Maturation of virus particles occurred at the plasma membrane, in a manner similar to that observed with other paramyxoviruses. Some cells containing inclusions exhibited an unusual type of particle formation in dilated portions of the endoplasmic reticulum. Bovine parainfluenza 3 virus appears to be unique among parainfluenza viruses in that its cytopathology and morphogenesis more closely resemble that of the unrelated measles subgroup of paramyxoviruses than that of the antigenically related parainfluenza viruses. * Submitted to the University of Toronto in partial fulfilment of the requirement for the Master of Science degree. Received 15 March 1971; accepted 23 April 1971.