Background: Lupine is used increasingly in food products. The development of lupine allergy in peanut-allergic patients is believed to occur  as a result of cross-reactivity between lupine and peanut proteins.

Objective: To investigate the degree of immunoglobulin (Ig) E cross-reactivity between allergens in lupine and peanut.

Methods: We investigated IgE cross-reactivity between lupine α-, ß-, γ-, and δ-conglutins and the major peanut allergens Ara h 1, Ara h 2 and Ara h 3 using enzyme-linked immunosorbent assay with sera from patients with coexisting peanut and lupine allergy.

Results: Peanut proteins inhibited IgE binding towards α- conglutins, δ-conglutins, and, to a lesser degree, ß-conglutins, while no IgE cross-reaction with δ-conglutin was observed. Ara h 2 most potently inhibited IgE binding to lupine and δ-conglutins, while Ara h 1 most potently cross-reacted with ß-conglutin. Ara h 3 was apparently not involved in these mechanisms.

Conclusions: The present study reveals IgE cross-reactivity between the 2S albumins Ara h 2 and δ-conglutin, and the 7S vicilin-like Ara h 1 and ß-conglutin, which are possibly based on homologies between phylogenetically related proteins. Ara h 2 was the most potent inhibitor of IgE binding to lupine conglutins.

Key words: IgE. Conglutin. Cross-reactivity. Lupine. Peanut.