Peanut allergic patients cross-react with lupin proteins : 34 clinic cases

PEANUT ALLERGIC PATIENTS CROSS-REACT WITH LUPIN PROTEINS: 34 CLINICAL CASES Sirtori1 E., Resta2 D., Wichers3 HJ., Savelkoul3 HFJ., Arnoldi1 A. 1Department of Endocrinology, Pathophysiology and Applied Biology, University of Milan, 20133 Milan, Italy. 2HPF-Nutraceutics, 20133 Milan, Italy 3Allergy Consortium, Wageningen University and Research Center, 6709 PG Wageningen, The Netherlands. E-mail: elena.sirtori@unimi.it Background: Peanut allergy is a significant health problem because of its high and rising prevalence and the life threatening nature of reaction. In developed countries it affects about 0.4–0.6% of children and 0.3–0.7% of adults. It has been estimated that 30% to 68% of peanut-allergic individuals also react to lupin flour. Lupin seeds are a useful source of human food products because of their composition, being high in protein and dietary fiber but low in fat and starch, and for its role in cardiovascular disease prevention. The most common specie of lupin consumed by humans is Lupinus albus L.; however the use of Lupinus angustifolius L. is increasing. Some individuals experience allergic reactions upon ingestion or inhalation of lupin products with symptoms ranging from mild local reactions to anaphylaxis. In 2007 lupin was declared as a new food allergen and was officially added to the EU list of known allergens (Commission Directive 2006/142/EC). Despite several study in literature, there is no consensus about the presence of one or more major allergen/s in lupin flour. In this context, the aim of the present investigation was to compare the two lupin species, and the proteins contained therein, with respect to the allergenic properties, based on their IgE-reactivity using sera from 34 peanut-allergic patients. In order to get of more general overview, different cultivars of each specie were taken in consideration. Methods: A comparative protein profile study was carried out in order to determine if the allergenicity of the two species differs: the main seed storage proteins (α-, β-, and γ-conglutin) were selectively purified and tested separately for IgE binding. ELISA assays (indirect and inhibition), western blotting using individual and pooled serum, and mass spectrometry analysis were performed in order to identify the IgE-binding proteins. Sera from 34 peanut-allergic patients were provided by several hospitals in Netherlands (Utrecht, Amsterdam, Arnhem, Ede, Velp). Results: The screening revealed significant differences in the chromatographic behaviour of all the globulins between the two species. Peanut sera reacted both with L. albus and L. angustifolius proteins with differences in magnitude of response: a stronger reactivity for α- and β-conglutin and no or less binding with γ-conglutin. The ELISA assays and the western blotting analysis highlighted several reactive spots, indicating the presence of different important allergenic proteins, rather than one major allergen. The different cultivars tested for each species had similar responses, indicating the presence of a related protein pattern with comparable IgE binding affinity. Conclusions: The IgE response of purified lupin protein fractions has varied among the peanut allergic patients, with differences of intensity. The results indicate that there is a direct relationship between the peanut-specific IgE level and the cross-reactivity to lupin proteins: the lupin allergenic response of each patient is unique and individual and strongly depends on the IgE level towards peanut proteins. In conclusion, in order to promote the use of lupin proteins in lupin-based novel food, it is essential that more should be understood about their allergenicity. More studies are needed to establish the prevalence of allergic reactions to lupin in peanut allergic individuals as well as in the population of allergic individuals.