Wheat products cause IgE-mediated allergies. The present study aimed to decipher the molecular basis of α- and γ-gliadin allergenicity. Gliadins and their domains, the repetitive N-terminal and the nonrepetitive C-terminal domains, were cloned and expressed in Escherichia coli. Their secondary structures and their IgE binding capacity were compared with those of natural proteins before and after reduction/alkylation. Allergenicity was evaluated with sera from patients who had a wheat food allergy or baker's asthma. The secondary structures of natural and recombinant proteins were slightly different. Compared with natural gliadins, recombinant proteins retained IgE binding but with reduced reactivity. Reduction/alkylation decreased IgE binding for both natural and recombinant gliadins. Although more continuous epitopes were identified in the N-terminal domains of α- and γ-gliadins, both the N-terminal and C-terminal domains contributed to IgE binding. As for other members of the prolamin superfamily, disulfide bonds appear to be of high importance for IgE binding.
Keywords: IgE epitopes; recombinant wheat allergens; synchrotron radiation circular dichroism; wheat allergy; wheat gliadins.