Electron microscopic studies of respiratory syneytial temperature-sensitive mutants

Summary

The A2 strain of respiratory syncytial (RS) virus and several temperature sensitive mutants derived from it were grown at the permissive (32° C) and restrictive temperature (39° C) in HeLa cells and thin sections of these cells were examined by electron microscopy. The mutants selected for this study were representative of 3 different complementation groups. The parent strain underwent the same sequence of morphogenesis at the permissive and restrictive temperatures. Morphogenesis of each of the mutants at the permissive temperature was similar to that of the parent strain. At the restrictive temperature cells infected with mutants belonging to two of the complementation groups developed a significantly reduced amount of one or more of the recognizable viral structures. In one instance (ts-4, complementation group A) budding and release of virus did not occur, while in another (ts-7, complementation group C) no virus specific structures were seen. Cells infected with the ts-2 mutant of complementation group B exhibited normal viral morphogenesis at restrictive temperature.