Abstract: α-Lactalbumin is one of the major allergens in cow milk. Characterizing the critical amino acids in the epitopes of α-lactalbumin is of great significance for the understanding of the role of immunoglobulin G (IgG) in milk allergy and the development of hypoallergenic dairy products. In this study, the alanine scanning of immunodominant epitopes was used to identify the critical amino acids. First, a series of peptides based on the sequence of α-lactalbumin were identified with IgG in individual sera from cow milk-allergic patients by enzyme-linked immunosorbent assay (ELISA). Then, new peptides were synthesized by sequential replacement of the amino acids acting on the epitopes with alanine, and the critical amino acids were identified with serum pool from cow milk-allergic patients by ELISA. The results showed that IgG-binding epitopes were located in the sequences of aa 6–20, aa 21–35, aa 36–50 and aa 86–100. Our data revealed Phe9, Leu15, Pro24, Trp26 and His32 were the critical aa in the IgG-binding epitopes.

Key words: cow milk allergy, α-lactalbumin, immunoglobulin G binding epitope, critical amino acids