Food allergy to wheat: identification of immunogloglin E and immunoglobulin G‐binding proteins with sequential extracts and purified proteins from wheat flour

TLDR

Cereal allergy is a serious problem because cereals are essential in daily diets. The study aimed to determine which wheat protein fractions bind IgE and IgG antibodies in wheat allergy. Wheat proteins were sequentially extracted and purified, then IgE and IgG binding were assessed by RAST, ELISA, and immunoblotting. IgE antibodies mainly recognize alpha, beta, gamma, and omega gliadins and low‑molecular‑weight glutenins, with albumin/globulin fractions also reactive, whereas high‑molecular‑weight glutenins are minor allergens; IgG binding patterns are similar and likely reflect sequence homology among gliadins and glutenins.

Abstract

Cereal-associated allergy is particularly considered a serious problem, because cereals are essential in our daily diet. Wheat proteins are classified into albumins, globulins and prolamins (insoluble gliadins and glutenins).Our objectives were to study the involvement in food allergy to wheat of these different protein types by using purified fractions and to identify those binding IgE and IgG antibodies.Sera were obtained from 28 patients with food allergy to wheat. Albumins/globulins, gliadins and glutenins were obtained by sequential extraction based on differential solubility; alpha-, beta-, gamma- and omega-gliadins and low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits were purified by chromatography. IgE binding to these extracts and fractions were analysed by radioallergosorbent test (RAST), and immunoblotting; IgG binding was detected by enzyme-linked immunosorbent assay (ELISA).In RAST, 60% of sera were shown to have specific IgE antibodies against alpha-, beta-gliadins and LMW glutenin subunits, 55% to gamma-gliadins, 48% to omega-gliadins and 26% to HMW glutenins. Immunoblotting analysis confirmed results obtained in RAST concerning LMW and HMW glutenin subunits and showed that 67% of patients have IgE antibodies to the albumin/globulin fraction.Results obtained in the different tests showed common features and in agreement with other studies indicated the presence of numerous allergens in food allergy to wheat; alpha-, beta-, gamma- and omega-gliadins, LMW glutenin subunits and some water/salt-soluble proteins appeared as major IgE binding allergens, whereas HMW glutenins were only minor allergens. The same type of antigenic profile against gliadins and glutenins was observed with IgG antibodies. Important sequence or structural homologies between the various gliadins and LMW glutenin subunits could certainly explain similarity of IgE binding to these proteins.