Allergenicity of hen's egg-white proteins: IgE binding of native and deglycosylated ovomucoid

Ovomucoid (OM) is a major allergen of hen's egg-white. Carbohydrate moieties from the glycoprotein were removed by chemical deglycosylation. Deglycosylated ovomucoid (d-OM) consists of five isoforms with molecular weights (MW) between 20.7 and 21.5 kDa whereas native OM has a MW of 28 kDa as determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry. The IgE-binding properties of both proteins were investigated All patients' sera tested, showed strong IgE binding to both native OM and d-OM in SDS-PAGE/immunoblot. In enzyme-allergosorbent test experiments, 50% inhibition of IgE binding was observed at almost the same inhibitor concentrations of 67 and 57 ng ml(-1) for native OM and d-OM respectively. Results indicate that only epitopes on the protein backbone are responsible for IgE binding while carbohydrate residues do not participate in allergenic structures of OM.