Identification of the critical amino acid residues of immunoglobulin E and immunoglobulin G epitopes on αs1-casein by alanine scanning analysis

alpha(s1)-Casein represents one of the major allergens causing cow milk allergy. Few studies have clearly evaluated immunological relationships between IgE- and IgG-binding epitopes of alpha(s1)-casein. This study aimed to map IgE- and IgG-binding epitopes of alpha(s1)-casein by the serology method, and identify the critical amino acids of alpha(s1)-casein by alanine scanning analysis. Our initial data revealed IgE-binding epitopes located in the sequences of AA 126 to 140, AA 6 to 20, AA 171 to 185, and AA 11 to 25. The sequences at AA 21 to 35, AA 56 to 70, and AA 161 to 175 were recognized by IgG antibodies. The alanine scanning analysis showed that IgE- and IgG-binding epitopes share the same critical AA: arginine at position 22 and phenylalanine at position 23. Results obtained from this study will provide necessary information to alter the cDNA to encode a protein with reduced IgE- or IgG-binding capacity.