Identification of the major water/salt insoluble wheat proteins involved in cereal hypersensitivity (1)
Bakers’ asthma is an occupational hypersensitivity disease primarily caused by the inhalation of flour proteins, mainly derived from wheat but also from rye, barley or soya. Wheat and other cereals are composed of four classes of proteins; the water/salt soluble albumins and globulins and the water/salt insoluble gliadins and glutenins which together are known as prolamins.
Total prolamins consist of a heterogeneous mixture of proteins of a molecular weight 30- 90kDa. The albumin/globulin fraction contains proteins of lower molecular weight than those of the prolamin fraction by < 15 kDa. The total gliadins have molecular weights between 30 and 65kDa, with the a- b- and g-gliadin having molecular weights of 30 -45 kDa and w-gliadins 45- 65 kDa. Total gluteins comprise high molecular weight subunits 75- 90kDa and lower molecular weight subunits of gluten 30 -45 kDa.
All sera had specific IgE antibodies binding to a-gladin: 24/24(100%), fast w-gliadin: 21/24 (88%), b-gliadin:18/24(75%), slow w-gliadin:15/24 (63%), g-gliadin:12/24(50%).
A moderate correlation was observed between the levels of specific IgE to water/salt soluble proteins with a-gliadin r=0.642, and fast w-gliadin r=0.636. The total IgE and specific IgE to b-, g,- and slow w-gliadin were obtained ad 0.641, 0.769 and 0.68, respectively.
A large number of allergens were detected by the different sera with molecular weights between 11- 90kDa. Strong IgE binding was specifically seen with the total glutenins, a-, b- and g-gliadins.
The subunits share common epitopes either with members of the gtiadin families and/or with water/salt soluble proteins. Water/salt insoluble proteins (10-21kDa), which have molecular weights similar to chloroform/methanol soluble inhibitors of wheat a-amylase were detected by immunoblotting.