Identification of the IgE-binding Epitope in ω-5 Gliadin, a Major Allergen in Wheat-dependent Exercise-induced Anaphylaxis

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a severe IgE-mediated allergic reaction provoked by the combination of wheat-ingestion with intensive physical exercise over the next few hours. Among wheat proteins, ω-5 gliadin, which is one of the components of fast ω-gliadin, has been reported as a major allergen in the anaphylaxis. In this study, we detected IgE-binding epitopes within the primary sequence of ω-5 gliadin using arrays of overlapping peptides synthesized on derivatized cellulose membranes. Sera from four patients with WDEIA having specific IgE to the fast ω-gliadin were used to probe the membrane. Seven epitopes, QQIPQQQ, QQLPQQQ, QQFPQQQ, QQSPEQQ, QQSPQQQ, QQYPQQQ, and PYPP, were detected within the primary sequence of ω-5 gliadin. By using sera of 15 patients, 4 of them, QQIPQQQ, QQFPQQQ, QQSPEQQ, and QQSPQQQ, were found to be dominant epitopes. Mutational analysis of the QQIPQQQ and QQFPQQQ indicated that amino acids at positions Gln¹, Pro⁴, Gln⁵, Gln⁶, and Gln⁷ were critical for IgE binding. These results will provide a useful tool for developing safer wheat products in addition to diagnostic and immunotherapy techniques for WDEIA.