Identification of a second major antigenic epitope in the α-subunit of soy β-conglycinin

Soybean meal in the post-weaning diet of pigs results in a growth lag correlated with Immunoglobulin G (IgG) production against soybean proteins, including the seed storage protein beta-conglycinin. We screened sera from 30 pigs for IgG directed against beta-conglycinin. Analysis of the same sera on protein blots identified sera that had IgG against the alpha-subunit of beta-conglycinin. A tiled peptide array (16 amino acids with an 11 amino acid overlap) of the alpha-subunit of beta-conglycinin was screened to identify the epitopes of the alpha-subunit that bind IgG. One major IgG binding epitope previously identified was confirmed. A second major IgG binding epitope was identified that bound IgG from half of the animals tested. Minor epitopes that bound IgG from one or two other sera were also identified. Binding of IgG to beta-conglycinin in an enzyme-linked immunosorbent assay (ELISA) was inhibited by a synthetic peptide representing one of the minor epitopes.