Allergenic rections to lupin proteins : study of the cross reactivity

ALLERGENIC REACTIONS TO LUPIN PROTEINS: STUDY OF THE CROSS-REACTIVITY Elena Sirtori1, Harry J. Wichers2, Huub F. J. Savelkoul2, Anna Arnoldi1 1Laboratory of Food Chemistry and Mass Spectrometry, Department of Endocrinology, Pathophysiology and Applied Biology, University of Milan, Italy. 2Allergy Consortium, Wageningen University and Research Center, Wageningen, The Netherlands. elena.sirtori@unimi.it Some literature information indicates that lupin ingredients, used in pasta and bread products, may provoke severe allergic reactions. According to the European Food Safety Authority (EFSA), since lupin flour contains IgE-binding proteins that show in vitro cross-reactivity with peanut, lupin flour could pose a risk to consumers with existing food allergies. Therefore, lupin was added to the EU list of known allergens (Commission Directive 2006/142/EC). Despite the presence of several studies in literature, there is no general consensus about one or more major allergen/s in lupine flour. Certainly, in order to promote the use of lupin proteins as food ingredients, it is essential to understand more about this issue. The present study was designed to investigate the allergenic characteristic of Lupinus albus and Lupinus angustifolius, two of the four lupin species with wide industrial applications. The aim was to compare various cultivars, and the purified proteins contained therein, in relation to their allergenic properties, based on the IgE-reactivity using sera from peanut-allergic patients. A protein profile study was carried out, in order to characterize the main proteins (2S, 7S, 11S) in a total protein extract. The proteins were analysed via anion-exchange chromatography, size exclusion and 2D electrophoresis, coupled with HPLC-Chip MS/MS. This screening revealed noteworthy differences in the chromatographic behaviour of all the globulins between the two species. A preliminary screening, using individual and pooled serum from peanut allergic patients, was performed in order to determine if the allergenicity of the two species differs. Direct and inhibition ELISA assays were used to investigate any differences in the allergenic responses of both TPE and purified protein fractions. The sera tested showed clear IgE cross-reactivity to lupin protein extracts of both species; cross-reactivity for lupin 7S and 11S also was found. The results indicate that there is a direct relationship between the peanut-specific IgE level and cross-reactivity to lupin proteins.