Glycosylation of the viral attachment protein of avian coronavirus is essential for host cell and receptor binding Lisa Parsons1, Kim M. Bouwman2, Hugo Azurmendi1, Robert P. de Vries3, John F. Cipollo1*, and Monique H. Verheije2 1 Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States. 2 Division of Pathology, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands. 3 Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands Running title: Avian coronavirus glycosylation * To whom correspondence should be addressed: E-mail: