The major allergen of peach (Prunus persica) is a lipid transfer protein

Background: Allergy to fresh fruits and vegetables is mostly observed in su bjects with pollinosis, especially from birch, because of cross-reacting al lergens in vegetable foods and pollens. However, allergic reactions to frui ts, specifically Rosaceae fruits, have been reported in subjects without po llinosis. Objective: This study evaluated the pattern of IgE reactivity, identifying the allergen responsible in 2 groups of patients with oral allergy syndrome to peach with or without birch pollinosis. Methods: The allergenic components of peach were detected by SDS-PAGE and i mmunoblotting. The major peach allergen was purified by HPLC with a cation- exchange column followed by gel filtration chromatography. Its IgE-binding capacity and its homology with the protein of the crude extract were demons trated by immunoblotting inhibition techniques, To better characterize this allergen, periodic acid-Schiff stain and isoelectrofocusing were used. The amino acid sequencing was done with a gas-phase sequencer. Results: SDS-PAGE and immunoblotting of the 15 patients allergic to peach, 8 without and 7 with birch pollinosis, showed that they all recognized a pr otein with a molecular weight of 9 kd. This was the only allergen recognize d by patients not sensitized to pollen, whereas the birch pollen-sensitive patients had IgE binding to other allergenic proteins at higher molecular w eights. The purified 9-kd protein retained its IgE-binding capacity, was ne gative to periodic acid-Schiff stain, and had an isoelectric point value of greater than 9. A search in the Swiss Prot Bank showed this was a lipid tr ansfer protein, belonging to It group of molecules involved in the defensiv e system of plants. Conclusions: The major allergen of peach is a 9-kd protein belonging to the group of Lipid transfer proteins. This is the only allergen recognized by patients allergic to peach but not sensitized to birch pollen.