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

• Published in: Allergy (Copenhagen) Vol. 63; no. 2; pp. 198 - 204
• Main Authors: Han, N, Järvinen, K.M, Cocco, R.R, Busse, P.J, Sampson, H.A, Beyer, K
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.02.2008; Blackwell Publishing Ltd; Blackwell
• Subjects: Adolescent; Amino Acid Sequence; Animals; Biological and medical sciences; Caseins - chemistry; Caseins - genetics; Caseins - metabolism; Child; Child, Preschool; cow's milk allergy; Dermatology; DNA Mutational Analysis; Epitopes - chemistry; Epitopes - genetics; Epitopes - metabolism; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Humans; IgE-binding epitope; Immunoglobulin E - blood; Immunoglobulin E - metabolism; Medical sciences; Milk Hypersensitivity - etiology; Milk Hypersensitivity - immunology; Molecular Sequence Data; mutational analysis; Peptides - chemical synthesis; Peptides - chemistry; Peptides - metabolism; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; sequential; κ-casein; Human; Food allergy; Immunopathology; cow's milk allergy; Bovine; Antigenic determinant; Dermatology; IgE; Identification; Vertebrata; Mammalia; Immunology; Casein; Sequential; IgE-binding epitope; Aminoacid; mutational analysis; Digestive diseases; Genetics; Cow milk; K-casein; Artiodactyla; Mutation; Ungulata
• ISSN: 0105-4538; 1398-9995
• DOI: 10.1111/j.1398-9995.2007.01539.x

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. 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. 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. 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.