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Identification of amino acids critical for IgE‐binding to sequential epitopes of bovine κ‐casein and the similarity of these epitopes to the corresponding human κ‐casein sequence
Author(s) -
Han N.,
Järvinen K. M.,
Cocco R. R.,
Busse P. J.,
Sampson H. A.,
Beyer K.
Publication year - 2008
Publication title -
allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.363
H-Index - 173
eISSN - 1398-9995
pISSN - 0105-4538
DOI - 10.1111/j.1398-9995.2007.01539.x
Subject(s) - epitope , immunoglobulin e , milk allergy , amino acid , peptide , casein , allergen , peptide sequence , biochemistry , chemistry , immunology , allergy , antibody , biology , gene
Background: The delineation of allergenic (i.e. IgE‐binding) epitopes in cow’s milk proteins and the amino acids (AAs) critical for IgE‐binding is necessary to understand better the structural properties of an allergen and to develop more efficacious immunotherapeutic reagents. Furthermore, this information may enable us to understand better cross‐sensitivity between different allergens. Methods: Eleven peptides, 10–14 AAs in length, representing the IgE‐binding epitopes of κ‐casein were synthesized on a derivatized cellulose membrane with single AA substitutions at each position. Membranes were incubated with pooled sera from 15 milk‐allergic patients and individual sera from 10 of the patients included in the pool. Results: For 10/11 allergenic peptides, one to five different single AA substitutions resulted in elimination of IgE‐binding of pooled patient sera. Overall at least one mutated peptide could be found for these 10 IgE‐binding sites that resulted in a reduction of IgE‐binding in at least 80% of the patients who recognized the native protein. Furthermore, the IgE‐binding region at AA104–112 on bovine κ‐casein showed a high degree of similarity with the human κ‐casein, respectively, including the AAs critical for IgE‐binding. Conclusion: This finding suggests that critical AAs should be assessed with both pooled and individual patient sera to account for the B‐cell epitope heterogeneity between patients, with cow’s milk allergy. In addition, we identified two potentially cross‐reactive peptides between bovine and human caseins of unknown clinical relevance.