Identification of IgE and IgG binding epitopes on beta- and kappa-casein in cow's milk allergic patients

Background Cow's milk allergy (CMA) affects 2.5% of children aged less than 2 years of age. Although beta- and kappa -casein are considered among the major allergens responsible for CMA, no: data are available on their allerg enic epitopes in humans. Objective The aim of the study was to identify IgE- and IgG-binding epitope s on beta- and kappa -casein and to determine whether the pattern of epitop e recognition is associated with the natural history of CMA. Methods Overlapping decapeptides representing the entire length of beta- an d kappa -casein, respectively, were synthesized on a cellulose-derivatized membrane. Sera from 15 milk-allergic children, 4-18 years of age, with high levels of specific IgE antibodies to cow's milk were used to identify IgE- and IgG-binding epitopes. In addition, IgE epitopes were screened with poo led or individual sera from younger patients aged less than 3 years and who had low levels of specific serum IgE, who are likely to outgrow CMA. Results Six major and three minor IgE-binding epitopes, as well as eight ma jor and one minor IgG binding regions, were identified on beta -casein. Eig ht major IgE-binding epitopes, as well as two major and two minor IgG-bindi ng epitopes, were detected on kappa -casein. Three of the IgE binding regio ns on beta -casein and six on kappa -casein were recognized by the majority of patients in the older age group, but not by the younger patients. Conclusion Information regarding the immunodominant epitopes in beta- and k appa -casein may be important for understanding the pathophysiology and nat ural history of CMA. Differences in epitope recognition may be useful in id entifying children who will have persistent milk hypersensitivity.