Neuraminidase treatment of avian infectious bronchitis coronavirus reveals a hemagglutinating activity that is dependent on sialic acid-containing receptors on erythrocytes

The interaction of infectious bronchitis virus (IBV) with erythrocytes was analyzed. The binding activity of IBV was not sufficient to agglutinate chicken erythrocytes. However, it acquired hemagglutinating activity after treatment with neuraminidase to remove α2,3-linked N-acetylneuraminic acid from the surface of the virion. Pretreatment of erythrocytes with neuraminidase rendered the cells resistant to agglutination by IBV. Susceptibility to agglutination was restored by resialylation of asialo-erythrocytes to contain α2,3-linked sialic acid. These results indicate that IBV attaches to receptors on erythrocytes, the crucial determinant of which is sialic acid α2,3-linked to galactose. In contrast to other enveloped viruses with such a binding specificity (influenza viruses and paramyxoviruses) IBV lacks a receptor-destroying enzyme.