Interaction of Influenza Virions with Receptors on Host Cells and on Erythrocytes

Abstract

It is well established that the hemagglutinin spikes on the surface of the influenza virus particles are responsible for the attachment of the virions to erythrocytes as well as to cells which support virus replication. It is also well established that the hemagglutinin receptors on erythrocytes from different species contain sialylated glycoproteins and that removal of the sialic acid residues from these molecules destroys their receptor activity. Although the virion receptors on the cells which are susceptible to infection (host cells) have not been characterized, it is assumed that sialylated molecules constitute the influenza virus receptors on these cells as well as on erythrocytes. However, receptors on host cells can be expected to differ significantly from those on erythrocytes. The major human erythrocyte glycoprotein has an unusually high sialic acid content (some 28% of its dry weight is sialic acid) (Winzler, 1969) and constitutes a larger fraction of the total membrane protein than does any single glycoprotein in other plasma membranes (see Hughes, 1973). In addition, whereas neuraminidase removes virtually all sialic acid residues from the erythrocyte membrane, some of these residues on the membranes of other cells are inaccessible to this enzyme (Eylar et al., 1962; Glick et al., 1970). Thus, a variety of glycoproteins as well as glycolipids could contribute to the hemagglutinin receptor activity of cells which can support influenza virus replication.