Morphology and development of Rift Valley fever virus in Vero cell cultures.

Rift Valley fever virus (RVFV) grown in vero cell cultures has a completed replication cycle within 13 hours. The first signs are the appearance of intranuclear fibrillar rods, followed by aggregations of precursor viral material in host cell cytoplasm and viral nucleocapsids budding into vacuoles associated with the Golgi apparati. Mature particles, liberated by the disintegration of vero cells, contained ribosomelike structures within the nucleocapsid, which was surrounded by a typical unit membrane through which were inserted some 350-375 surface spikes whose inner ends were incorporated into the nucleocapsid structure. In the negatively stained material, the overall diameter of the virion was 90-110 nm; the spikes were 10-18 nm in length and 5 nm in diameter.