Interaction of Sendai virus with human erythrocytes. III. Further investigation on the effects of pyridine on the virus envelope.

The ultrastructure of the pyridine-treated Sendai virus has further been investigated by electron microscopy of chemically fixed and negatively stained virions. Marked changes in the ultrastructural appearance of the viral envelope have been detected. The extent of these changes depends on pyridine dose and ranges from minor extraction of the outer track components to multiple breaks and disintegration of the whole envelope. At 16% pyridine a fragmentation of viral nucleocapsid has also been noted. Both the nature of these changes and the fact that even fully burst viral particles can eventually retain regularly-arranged spikes, strongly suggest that pyridine primarily affects the organization of the double-track viral membrane, probably by sequential extraction of lipids and protein components. The results are discussed in the light of the selective property of pyridine in discriminating among the biological activities of the Sendai virus and give additional support to the idea that phospholipids and a glycoprotein spike play cooperative roles in the hemolytic activity of the virus.