PARAINFLUENZA VIRUS TYPE-I VARIANTS - ANALYSIS OF HEMAGGLUTINATING, NEURAMINIDASE AND FUSION ACTIVITIES

The existence and the character of two variants or subpopulations in a Sendai standard virus sample were studied, and virus variants were se lected by a technique based on the receptor-binding activity. The sial idase biological activity of the Sendai variant samples of parainfluen za type 1, their pH-dependence, calcium-dependence and association wit h hemagglutinating and hemolytic capabilities were studied. Both the s tandard-like sample and one obtained by an adsorption process exhibite d the highest hemagglutinating or sialidase activities at pH values be tween 5.0 and 7.0, However, the standard-like sample did not exhibit h emagglutinating activity to human O group erythrocytes at all pH value s used, but it did show significative sialidase activity. The sialidas e activity was calcium-dependent and was shown related with Be hemolyt ic activity. The low hemolytic activity could be explained by efficien t enzymatic activity developed for HN structures on cell receptors tha t could be essential for the fusion process. The samples exhibited div erse hemagglutinating and neuraminidase characters that suggested sele ction of different viral variants or subpopulations.