Development of a competitive ELISA for the detection of soybean α subunit of β-conglycinin

The alpha subunit of β-conglycinin is one of the main allergens found in soybeans. For the preparation of a specific monoclonal antibody (mAb) against the α subunit, potential epitopes were predicted using Protean and evaluated by Wu's Antigenic Index. The specific epitope ⁸⁵EQDERQFPFPR⁹⁵ was synthesized, and then conjugated to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA) for use as an immunogen and the plate-coating antigen, respectively. The resulting mAb, termed mAb-60K, was characterized as belonging to the IgG1 isotype and containing the κ light chain; it exhibited high specificity for the α subunit and did not cross react with the α′ and β subunits of β-conglycinin or other proteins found within soybeans. A competitive enzyme-linked immunosorbent assay (cELISA) with high accuracy and reproducibility was developed based on mAb-60K and the plate-bound peptide. Co-incubation with the full-length α subunit showed a 50% mAb binding inhibition concentration (IC₅₀) value of 4.42 ng/mL, with a linear inhibition curve observed α subunit concentrations between 0.65 and 29.84 ng/mL. The newly developed mAb-60K and the companion cELISA could provide a valuable tool for determining sensitivity towards the α subunit of soybean β-conglycinin and for future studies on food allergies resulting from this protein.