Identification and characterization of linear B-cell epitopes of β-globulin, a major allergen of sesame seeds

Background

The increased consumption of foods containing sesame seeds is paralleled by an increase in reported sesame-induced allergic reactions.

Objective

This study aimed at identifying and characterizing the linear B-cell epitopes of the 14-kd β-globulin, the major allergen of sesame seed.

Methods

A peptide containing 71 amino acids (peptide B) was previously identified by us as the IgE-binding region on β-globulin. To determine the amino acid sequence of the IgE-binding sites on peptide B, we synthesized overlapping peptides 20 and 10 amino acid residues long that span the entire length of peptide B, which were offset from each other by 10 and 2 amino acid residues, respectively. Sera from 20 subjects given diagnoses of allergy to sesame β-globulin served to identify the epitopes by using the dot-blot test.

Results

At least 9 different IgE-recognition sites were identified on peptide B. Three of them, numbers 2, 3, and 13 (corresponding to amino acids 46-55, 48-57, and 76-86, respectively, in the β-globulin sequence), appeared to be immunodominant IgE-binding epitopes. Also, these peptides were best recognized in terms of intensity of response. There was no obvious sequence motif shared by the 9 different IgE-binding epitopes of β-globulin. However, approximately 60% of the amino acids represented in the epitopes are hydrophobic residues.

Conclusion

Identification of the IgE-binding epitopes might provide a better understanding of the functional role the allergens play in the disease and might have implications for immunodiagnosis and probably immunotherapy.

Key words: Allergenicity, sesame seeds, major allergen, IgE, amino acid sequence, peptide synthesis, epitopes