Attachment of bovine parvovirus to sialic acids on bovine cell membranes

Although it has previously been shown that bovine parvovirus (BPV) attaches to the sialated glycoprotein glycophorin A on erythrocytes, the nature of virus-binding moieties on mammalian nucleated cells is less clear. Buffalo lung fibroblasts (Bu), primary bovine embryonic kidney cells, Madin-Darby bovine kidney cells and bovine embryonic trachea (EBTr) cells were assessed for molecules capable of binding BPV. Competition studies were carried out on both erythrocyte and nucleated cell targets using a variety of sialated compounds and sialic acid-negative compounds. Glycophorin A was found to inhibit BPV binding, while mucin exhibited low-level inhibition. These two sialated compounds also blocked attachment of BPV-modified microsphere carriers to the Bu cell membrane. Influenza A virus was used as a sialic acid competitor and interfered with BPV attachment to erythrocytes and replication in Bu cells. Significantly, the enzyme sialidase removed BPV-binding sites from Bu and EBTr cells. The binding sites could be reconstituted on sialidase-treated cells by the enzymes alpha-2,3-O-sialyltransferase and alpha-2,3-N-sialyltransferase. These results indicated that BPV can attach to sialic acid on cell membranes and that the sialylglycoproteins available for virus attachment appear to contain both N- and O-linked carbohydrate moieties, but that not all members of the sialic acid family can bind BPV. Moreover, there may be other moieties that can bind BPV, which may act as either primary or secondary receptors.