Identification of IgE- and IgG-binding epitopes on alpha(s1)-casein: Differences in patients with persistent and transient cow's milk allergy

Background: Cow's milk allergy (CMA) affects 2.5% of children less than 2 y ears of age, but about 80% become clinically tolerant within the first 3 ye ars of life. Casein is one of the major allergens responsible for CMA and s eems to play an important role in persistent allergy. Previous studies on e gg allergy suggested that linear epitopes are associated with longlasting f ood allergy. Objective: The aim of the study was to identify IgE- and IgG-binding epitop es on alpha (s1)-casein and to determine whether the patterns of epitope re cognition are associated with the natural history of CMA. Methods: According to the known amino acid (AA) sequence, 96 overlapping de capeptides representing the entire length of alpha (s1)-casein were synthes ized on a cellulose-derived membrane. Sera from 24 children with milk aller gy were used to identify IgE- and IgG-binding epitopes. Results: Six major and 3 minor IgE-binding, as well as 5 major and 1 minor IgG-binding, regions on alpha (s1)-casein were identified. Two IgE-binding regions (AA 69-78 and AA 173-194) were recognized by the majority of patien ts over a years of age with persistent allergy (67% and 100%, respectively) but by none of the children less than 3 years of age who are likely to out grow CMA. No differences in IgG binding between the groups were observed. Conclusion: There appears to be a difference in epitope recognition between patients with different natural histories of CMA. Screening for IgE antibo dies to these epitopes may be useful in identifying children who will have persistent milk hypersensitivity.