LA MATURAZIONE DEL VIRUS DELLA ROSOLIA IN COLTURE CELLULARI INFETTATE CON CEPPI VIRULENTI ED ATTENUATI. STUDIO ULTRASTRUTTURALE

The maturation and release phases of rubella virus and the type of cytopathic effect (CPE) produced in SIRC cells infected by virulent strains of rubella virus were studied by means of electron microscopy. The maturation process always takes place in the Golgi complex vesicles and virion release can have origin either from fusion of the limiting membrane of the vesicles (from the Golgi complex) with the cytoplasmic membrane or from cytoplasmic fragment detachment ('zeiosis'). The main ultrastructural features of rubella induced CPE in SIRC cells consist of cytolysome increase, presence of large ribosome groups without connections with endoplasmic reticulum membranes and appearance of intranuclear 'spheroid bodies', more frequently fibrous. The last finding is considered an expression of reserve material deposit employed by the cells in which virus is replicating. In rabbit kidney primary cultures infected by attenuated strains of rubella virus the presence of virions has never been observed. The interesting analogy between secretion granule production and excretion in secretory cells and rubella virus maturation and release processes is discussed.