Null Alleles in Gliadin Coding Loci and Wheat Allergenic Properties

Wheat gliadin proteins-an important, nutritional component of many food products may also act as allergenic proteins causing various, clinical symptoms of IgE-mediated food allergies. Gliadins are coded by six complex loci on the chromosomes 1A, 1B, 1D,6A, 6B and 6D of wheat genome. Each of the loci coding from a few to a dozen of polypeptides may spontaneously mutate to inactive gene variants called null alleles that do not code any proteins at all. The aim of the present work was to find out whether null alleles in some gliadin coding loci may decrease wheat allergenic properties. Six winter wheat genotypes: gliadin deletion lines (GDL) containing null alleles on 1D, 1B and 6B chromosomes and control lines (CL) containing active gene variants in all gliadin coding loci, were developed using plant breeding methods. Allergenic properties of the six analyzed hybrids were estimated by ELISA using polled sera of five patients allergic to gluten. Estimated immunoreactivity of GDLs was from 6% to 18% lower as compared with CLs. The obtained results evidenced that gliadin null alleles decrease wheat allergenic properties and may be used as parental forms for breeding of hypoallergenic wheat genotypes.

Purified Wheat Gliadin Proteins as Immunoglobulin E Binding Factors in Wheat Mediated Allergies

Some wheat gliadin proteins are strong allergens that may cause various symptoms of food allergies and baker’s asthma. The most immunoreactive ω-5 gliadin fractions are the main allergens in wheat dependent exercise induced anaphylaxis (WDEIA). While the allergenicity of ω-5 is quite well understood, knowledge about α, β, γ and ω-1.2 gliadins is much more scanty. This study examines allergenic properties of other fractions as compared to ω-5. Gliadins were extracted from flour of winter wheat (Triticum aestivum L.) cultivar Ostka strzelecka. Purified samples representing proteins belonging to α, β, γ, ω-1.2 and ω-5 classes were isolated using preparative gel electrophoresis. Immuno-reactivity and allergenic properties of these proteins were analyzed by ELISA using sera from allergic patients with elevated sIgE (> 2KU/L), and by skin prick test (SPT). ELISA showed that ω-5 and ω-1.2 differed considerabely from α-, β- and γ-gliadins in respect of immunoreactivity. Responses of both ω-gliadins were almost twice as high as for other fractions. Significant differences were also observed among individual ω-gliadin fractions as evidenced by ANOVA. SPT showed that patient with symptoms of baker’s asthma and WDEIA had a positive results to all gliadins tested. Another patient with baker’s asthma (but not WDEIA) reacted positively only to ω-5 gliadins. In two patients with skin allergy SPT were negative with all analyzed proteins. Results show ω-1.2 gliadins to be almost as immunorective as ω-5. The α-, β- and γ-gliadins also recognize specific IgE antibodies, but their binding capacity is only about half that of ω-fractions. This kind of immunoreactivity could still be important since a cumulative effect of individual fractions may intensify disease symptoms in allergic patients.