Effect of blood group determinants on binding of human salivary mucous glycoproteins to influenza virus.

We have demonstrated that the inhibitor of influenza B virus hemagglutination in human saliva is inactivated by neuraminidase and is associated with the mucous glycoprotein fraction (blood group substance) of this secretion. Inhibitory activity of saliva was found to be roughly proportional to its sialic acid content (r = 0.456). However, the minimal quantity of salivary sialic acid, neutral sugar, or blood group antigen required to inhibit virus hemagglutination was greater for secretors of A and B than for secretors of H and Lea blood group substances. Removal of terminal galactose from blood group B substance with alpha-galactosidase markedly decreased blood group B activity but increased blood group H and virus hemagglutination inhibitory activities of this glycoprotein. These data suggest that terminal alpha-linked galactose and, probably, N-acetyl-galactosamine interfere with access of influenza virus to binding sites on oligosaccharide chains of the mucous glycoprotein.