An 'on grid' electron microscopic method for studying the interaction and fusion of influenza A virus with human erythrocyte membranes.

An 'on grid' negative staining method was developed to study the interaction of influenza virus with erythrocyte membranes. The virus was reacted in situ with cells which had been immobilised on an electron microscope grid. Fusion between influenza virus and the membrane of erythrocyte ghosts was clearly seen using this method.

The action of Vibrio cholerae and Corynebacterium diphtheriae neuraminidases on the Sendai virus receptor of human erythrocytes.

Studies of the Sendai virus haemagglutinin receptor on the human erythrocyte surface have confirmed that it involves 2 leads to 3 linked sialic acid. Because the primary specificity of Vibrio cholerae neuraminidase is for this linkage, it is able to compete with the virus for the receptor, to which it adsorbs strongly at low temperatures. Corynebacterium diphtheriae neuraminidase, whose principal specificity is for a sialic acid linkage other than 2 leads to 3, does not easily remove Sendai virus receptors, nor does it adsorb to the erythrocyte surface. A new definition of the term "receptor-destroying enzyme" is given which takes both enzyme and virus specificity into account, and a modified assay method is suggested in order to overcome the problems due to enzyme adsorption.