Sialic acid acts as a receptor for equine rhinitis A virus binding and infection

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Abstract
Equine rhinitis A virus (ERAV) is a member of the genus Aphthovirus, family Picornaviridae, and causes respiratory disease in horses worldwide. To characterize the putative receptor molecule(s) of the ERAV isolate 393/76 (ERAV.393/76) on the surface of Vero and other cells, an assay was developed to measure the binding of purified biotinylated ERAV.393/76 virions to cells by flow cytometry. Using this assay, the level of binding to different cell types correlated with the relative infectivity of ERAV in each cell type. In particular, equine fetal kidney cells, mouse fibroblast cells, rabbit kidney-13 and Crandell feline kidney cells bound virus at high levels and produced high virus yields (⩾107 TCID50 ml−1). Madin–Darby bovine kidney and baby hamster kidney cells showed little or no binding of virus, producing yields of ⩽101·8 TCID50 ml−1. Treatment of Vero and other cells with sodium periodate and the metabolic inhibitors tunicamycin, benzyl N-acetyl-α-d-galactosamide, d,l-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol and proteases indicated that part of the receptor-binding and entry complex for ERAV.393/76 is on N-linked carbohydrates and that the carbohydrate is likely to be present on a protein rather than a lipid backbone. The effect of carbohydrate-specific lectins and neuraminidases on ERAV.393/76 binding and infection of Vero and other cell types implicated α2,3-linked sialic acid residues on the carbohydrate complex in the binding and infection of ERAV.