Quantification of major peanut allergens Ara h 1 and Ara h 2 in the peanut varieties Runner, Spanish, Virginia, and Valencia, bred in different parts of the world

Background: The serology of peanut allergy seems to be different in various parts of the world. We analyzed the composition of 13 samples of three varieties of peanut in order to compare their allergenic nature. Methods: Peanut cultivars that are commonly processed in the West were analyzed for protein content, protein composition, and Ara h 1 and Ara h 2 content by biochemical methods. IgE-binding properties were analyzed by ELISA using serum from patients with documented peanut allergy. Results: Total protein contents were comparable for all tested samples (24-29%), and proteins were extractable to the same extent. SDS-PAGE patterns differed slightly, but all major bands were visible in all samples (molecular masses of approximately 14-100 kDa under reducing conditions). Ara h 1 and Ara h 2 were quantified by SDS-PAGE densitometry and were expressed as percentage of the total protein content. Ara h 1 was in the range 12-16%, whereas Ara h 2 was 5.9-9.3%. In view of the analytic uncertainty of this determination, the content of both Ara h 1 and Ara h 2 was not significantly different between the tested samples. In an IgE-binding inhibition ELISA, the affinities of the peanut proteins for peanut-specific IgE were measured. Minor differences were observed between the tested samples, with the most potent IgE-binding sample having a two times higher ability to bind IgE than the weakest IgE-binding sample. Conclusions: The results suggest that peanuts of different varieties and from different parts of the world contain similar proteins, including Ara h 1 and Ara h 2. Consequently, the IgE-binding properties are similar to a great extent. This indicates that differences in the serology of peanut allergy may not originate from differences in the allergen composition of the peanut.