Characterization of asparagus allergens:: A relevant role of lipid transfer proteins

Background: No asparagus allergen has been characterized to date. Lipid transfer proteins (LTPs) have an ubiquitous distribution in plant foods and have been identified as relevant allergens in some fruits, seeds, and pollens. Objective: We sought to identify asparagus allergens and to evaluate the potential involvement of the panallergen UP family in asparagus allergy. Methods: Eighteen patients with asthma, anaphylaxis, and/or contact urticaria after asparagus ingestion or exposure and positive skin prick test (SPT) responses and serum-specific IgE levels to asparagus were selected. Two LTPs were isolated from crude asparagus extract by using chromatographic methods and characterized by means of N-terminal amino acid sequencing. Both isolated proteins were tested by means of immunodetection, CAP inhibition assays, and SPTs. Additional asparagus allergens were located by using immunodetection with a pool of sera from patients allergic to asparagus and with rabbit polyclonal antibodies to sunflower pollen profilin and anti-complex asparagine-linked glycans antibodies. Results: The purified LTPs showed an N-terminal amino acid sequence similar to that of Pro p 3 and a strong reaction to anti-Pru p 3 antibodies. Each isolated protein reached inhibition values of up to 60% in CAP inhibition assays against asparagus extracts and elicited positive SPT responses in 9 of 18 patients with asparagus allergy. Immunodetection assays allowed us to identify profilin and cross-reacting carbohydrate determinants as asparagus IgE-binding components. Conclusion: Asparagus LTPs are relevant allergens. In addition, profilin and glycoproteins harboring complex asparagine-linked glycans can also be involved in asparagus allergy.