Characterization of IgE binding to lupin, peanut and almond with sera from lupin-allergic patients.

Background: The increasing number of applications of sweet lupins in food is paralleled by an increase in immunoglobulin E (IgE)-mediated allergic reactions to lupin proteins. In particular, lupin allergy seems to appear in patients with an existing peanut allergy. In the present study, IgE-binding studies towards fractionated lupin seed proteins, and peanut and almond proteins were performed using sera from patients with confirmed lupin allergy.

Methods: Immunoblotting and indirect ELISA were performed to investigate IgE binding to protein extracts. ELISA inhibition experiments were performed to investigate the presence of cross-reactive allergens in the protein extracts.

Results: Immunoblotting and ELISA experiments demonstrated IgE binding to all lupin conglutins (alpha, beta, gamma and delta) as well as to peanut and almond proteins, with a unique IgE-binding profile for each patient. High IgE binding to alpha-conglutin was observed and IgE from the majority of patients similarly recognized two proteins within the alpha-conglutin-containing fraction, 40 and 43 kDa in size. Inhibition ELISA experiments showed that preincubation of sera with lupin conglutins, peanut and almond resulted in decreased IgE binding to lupin flour.

Conclusions: Overall, these results indicate that alpha-, beta-, gamma- and delta-conglutins are candidate allergens in lupin and suggest a particularly strong allergenicity of alpha-conglutins. Furthermore, the results indicate the presence of cross-reactive allergens in lupin, peanut and almond.