Immunoreactivity and detection of wheat proteins by commercial ELISA kits

Wheat proteins are responsible for sensitivities, including baker's asthma, immunoglobulin E (IgE)-mediated allergic reaction, wheat-dependent, exercise-induced anaphylaxis, and celiac disease. The detection of gluten/wheat traces in foods is important to safeguard the health of wheat-sensitive individuals and comply with food labeling. Many immunoanalytical-based commercial kits are available for the quantification of gliadin/gluten/wheat proteins. We compared the immunoreactivity of wheat fractions with wheat-allergic human serum IgE and antibody conjugates used in six commercial immunoassay kits. Moreover, the performance of the kits was tested using corn flour spiked with gluten (5, 10, 25, and 50 ppm) and wheat flour (50, 100, 250, and 500 ppm). The albumin, globulin, gliadin, and glutenin fractions reacted with IgE from nine, eight, two, and eight patients' sera, respectively, out of nine wheat allergic patients tested. Among the antibodies from commercial kits, those from R-Biopharm, Morinaga, and Romer Labs reacted strongly with the gliadin fraction, whereas those from BioKits, ALLER-TEK, and ELISA Systems reacted strongly with the glutenin fraction. All kits showed minimal or no reactivity with albumin and globulin fractions. All kits detected the gluten and wheat flour in a corn flour matrix at the lowest spiked levels of 5 and 50 ppm, respectively. However, there was wide variation among the kits when comparing the recovery of gluten and wheat flour. The recovery was also dependent on the source material (gluten or wheat flour) used for spiking the corn flour matrix.