Evidence for a lipid transfer protein as the major allergen of apricot

Background: Apricots are widely grown in Europe, and allergic reactions are becoming more common, especially oral allergy syndrome. Apricot belongs to the botanical subfamily of Prunoideae, which includes peach, the major all ergen of which was identified as a 9-kd protein, a lipid transfer protein ( LTP). Objective: The aim of the study was to evaluate the IgE reactivity pattern to an apricot extract in subjects with allergic reactions to apricot, as de monstrated by a positive oral challenge response. Methods: Thirty patients were investigated. All the patients displayed oral allergy syndrome (2 with systemic reactions) to apricot, with positive ope n food challenge responses, skin prick test responses, and serum-specific I gE antibodies to apricot. The IgE reactivity pattern to apricot extract was identified by using SDS-PAGE and immunoblotting. The major allergen, a 9-k d protein, was then purified by HPLC and characterized by periodic acid-Sch iff stain, isoelectric point determination, and N-terminal amino acid seque ncing. Results: The sera from all patients allergic to apricot recognized the 9-kd protein, whereas none of the other allergens, with molecular weights from 15 to 80 kd, acted as a major allergen. The 9-kd allergen has an isoelectri c point of 8.7 and is not glycosylated. Determination of the N-terminal 34 amino acid sequence showed that it belongs to the LTP family, with a 94% ho mology with the LTP from peach. IgE blotting of the apricot extract was com pletely inhibited by the 9-kd purified LTP from peach. Conclusions: The major allergen of apricot is an LTP, which is highly cross -reactive with the LTP from peach.