Binding sites for rubella virus on erythrocyte membrane.

To identify molecule(s) with the properties of rubella virus (RV) receptor, goose erythrocyte membranes were isolated and tested for their ability to complete with whole cells for viral binding and fusion. Solubilized membranes showed a dose-dependent inhibiting activity on either rubella virus attachment or its fusion with erythrocytes at acidic pH. The inhibitory activity was enhanced by trypsin and neuraminidase, and inactivated by phospholipase A2 digestion, pointing towards the involvement of lipid structures as receptor sites for RV. After isolation of the different membrane components, only the lipid moiety, specifically phospholipids and glycolipids, was found to inhibit viral biological activities. When the major membrane lipids were examined separately, phosphatidylserine and cerebroside sulfate showed a strong inhibiting activity on viral hemagglutination and subsequent hemolysis. The capacity of several pure phospholipids (phosphatidylinositol, phosphatidylcholine and sphingomyelin) to inhibit the hemolysis but not the binding of the virus to the erythrocytes indicated that different membrane lipid components are involved in the attachment and the fusion step. Enzymatic and chemical modifications of whole erythrocytes confirmed the role of membrane lipid molecules in the cell surface receptor for RV.