Electron Microscopy of Rio Bravo Virus in African Green Monkey Kidney Cells
FORT DETRICK FREDERICK MD
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Rio Bravo virus, a Group B arbovirus, examined for the first time by electron microscopy and immunofluorescence, was found to be similar in appearance and size to other members of this group. It is a small virus, approximately 40 micrometers in diameter, and consists of a dense core surrounded by a membrane. Inoculation of cultures of African green monkey kidney cells produced marked morphologic changes in the nucleus and cytoplasm. There was a striking loss of granular material in the nucleus. Electron-dense particles, 25 to 40 micrometers in diameter, were seen in the nuclei of some cells, but the significance of these particles is unknown. The normal granular appearance of the cytoplasm disappeared, and there was a gradual and progressive increase in size of the mitochondria. Concurrently, the cell vaculoes increased in size, and large numbers of electron-dense particles were concentrated on the membranes of these structures as well as on the nuclear membranes. The particles are believed to be precursors of the mature virus because they were identical in size to the core of the mature virus and were frequently and consistently seen in cultures shown to be infected by immunofluorescence and viable assay.