Molecular and Immunological Characterization of Gamma Gliadins As Major Allergens in Wheat Food Allergy

Wheat gluten proteins provoke IgE-associated allergy (i.e., food allergy and wheat-dependent exercise-induced anaphylaxis) as well as T cell-mediated hypersensitivity (i.e., celiac disease). Here, we aimed to characterize wheat gamma gliadins regarding their molecular, structural and immunological properties in detail. Five recombinant wheat gamma gliadins were expressed in Escherichia coli cells, purified to homogeneity, characterized by means of SDS-PAGE, mass spectrometry, gel filtration, circular dichroism, and their allergenic activity was studied by RAST-based IgE dot blotting as well as rat basophil β-hexosaminidase release assay. IgE epitope mapping was performed with synthetic overlapping peptides spanning the gamma gliadin sequence. Wheat gamma gliadins react with IgE antibodies from 62% of wheat food allergic patients and exhibit strong allergenic activity by basophil activation. Gamma gliadins represent proteins with high degree of sequence identity and form strong protein aggregates under reducing and non-reducing conditions. According to circular dichroism analysis, recombinant gamma gliadins represent unfolded proteins. Immunodominant IgE epitopes were identified on the N-terminus indicating that IgE recognition does not require fold and is directed against linear epitopes. Thus, gamma gliadins can be considered as typical class I food allergens which sensitize generally via the gut such as several allergens originating from other food sources. Recombinant gamma gliadins representing major wheat food allergens may be used for diagnosis and immunotherapy of wheat food allergy.