Identification of potentially cross-reactive peanut-lupine proteins by computer-assisted search for amino acid sequence homology.

Background: Allergic cross-reactions are an issue of major concern because of implications for public health. The molecular basis of cross-allergy is the similarity of epitopes belonging to proteins of different organisms. Lupine is an emerging cause of food allergy, which has become a 'hot topic' because of recent large-scale introduction into processed foods and frequent cross-reactions with other members of the legume family. However, no lupine allergen has been characterized thus far. Prompted by a recently reported case of peanut-lupine cross-allergy, we wished to identify the possible cross-reactive allergen(s) between the two vegetal species.

Methods: We used computer-aided amino acid sequence comparison, a well-established technique for the study of protein homology, and followed the FAO/WHO guidelines for the identification of potential allergens. We also performed a three-dimensional modeling of the suspected cross-reactive proteins to compare their molecular surfaces.

Results: We found a highly significant sequence homology and molecular similarity between allergen Ara h 8 of peanut and pathogenesis-related protein PR-10 of white lupine. Another protein of lupine, the beta-conglutin precursor, was found to be significantly homologous to the Ara h 1 allergen of peanut. The molecular surfaces of Ara h 8 and PR-10 were remarkably similar.

Conclusions: Our in silico data allow to predict the allergenicity of PR-10 and beta-conglutin precursor of white lupine according to FAO/WHO guidelines. Amino acid sequence homology also suggests that these proteins could be responsible, at least in part, for some of the allergic cross-reactions between peanut and lupine reported in the literature.