Identification of the major water/salt insoluble wheat proteins involved in cereal hypersensitivity

Background: Several studies have investigated water/salt soluble proteins which comprise 50% of the proteins in wheat. The remaining 50% of wheat proteins, are water/salt insoluble proteins of which there is limited information on their role in cereal hypersensitivity. Objectives: To investigate the allergenicity of the water/salt insoluble gliadin and glutenin proteins (prolamins). Methods: RAST, electrophoresis and Western blotting were used to identify water/salt insoluble wheat allergens. Competitive RAST inhibition was conducted to investigate cross-reactivity between prolamins and water/salt soluble wheat proteins. Results: Specific IgE to α-gliadin and to total glutenins were detected in all sera. IgE to β-, c-, fast ω-, and slow ω-gliadin were present in lower numbers of sera. Prolamin allergens of 90-11 kDa were identified by immunoblotting. Water/salt soluble proteins crossreacted with α-gliadin and total glutenins. Conclusions: Individuals who are hypersensitive to water/salt soluble wheat proteins produce specific IgE to water/salt insoluble wheat proteins. Western blotting has shown that gliadins, glutenins and proteins with similar molecular weights as the endogenous water/salt soluble wheat enzyme inhibitors are important allergens. Alpha and fast ω- are the most allergenic gliadins. The water/salt insoluble proteins share cross-reacting epitopes with water/salt soluble proteins. These data show that the numbers of proteins involved in the development of cereal hypersensitivity is greater than previously believed and that the development of specific IgE to α- gliadin may in part depend on the presence of cross-reacting antibodies to water/salt soluble flour allergens.