Identification of IgE-binding epitopes on gliadins for patients with food allergy to wheat

Background: Food allergy to wheat induces different symptoms as atopic eczema/dermatitis syndrome (AEDS), urticaria and more severe reactions as wheat-dependent exercise-induced anaphylaxis (WDEIA). Different gliadin classes are involved in this allergy but IgE-binding epitopes are known only on omega(5)-gliadins and for WDEIA cases. Objectives: The aim of the study was to identify IgE-binding epitopes on several gliadin classes and for several patients with different symptoms and ages. Methods: Eleven sera were analysed by pepscan with overlapping synthetic peptides. Results: Sera from five patients with anaphylaxis, urticaria or WDEIA, displayed strong IgE-binding to sequential epitopes of the repetitive domains of alpha beta, gamma, omega(2) or omega(5)-gliadins with two immunodominant epitopes on omega(5)-gliadin and a consensus motif of the type QQX(1)PX(2)QQ (X-1 being L, F, S or I and X-2 Q, E or G). One patient allergic to deamidated wheat proteins also had IgE to a repetitive peptide of gamma and omega(2)-gliadins of the type QPQQPFP. Sera from four patients with AEDS detected no linear epitopes on gliadins, despite the fact that they contained specific IgE to alpha, beta, gamma or omega-gliadins. One child with AEDS recognized cysteine-containing sequences in the nonrepetitive domains of alpha beta and gamma-gliadins. Conclusion: B epitopes in wheat allergy were different from B epitopes of coeliac disease. Differences exist in IgE-binding epitopes between patients with food allergy to wheat. IgE from those suffering from WDEIA, anaphylaxis and urticaria detected sequential epitopes in the repetitive domain of gliadins whereas IgE from AEDS patients probably recognized conformational epitopes.