Lipid transfer protein (Ara h 9) as a new peanut allergen relevant for a Mediterranean allergic population

Background: Nonspecific lipid transfer proteins (LTPs) represent potent pollen and food allergens. However, the allergenic properties of peanut LTP have not been studied. Objective: To identify LTP in peanut extract using sera from subjects with peanut allergy and Pru p 3-sensitized subjects from Southern Europe, clone and express this protein, and obtain information on the importance as allergen for these selected patients. Methods: Peanut LTP (Ara h 9) was cloned and sequenced by using a combination of bioinformatic and molecular biology tools (PCR, immunoblotting, Basic Local Alignment Search Tool [BLAST] searches). The immunologic properties of Ara h 9, Ara h 1, Ara h 2, and Ara h 3 were studied by using sera from subjects with peanut and peach allergy from Italy by immunoblotting and allergen microarray technology. Results: Two Ara h 9 isoforms-Ara h 9.01 and Ara h 9.02-were cloned and expressed. Ara h 9 represented a minor allergen for subjects with peanut allergy. However, including Ara h 9 as single component for serologic detection of sensitization to peanut by component-resolved diagnosis seems crucial, because the frequency of sensitization to the classic major peanut allergens Ara h 1, Ara h 2, and Ara h 3 was low in these patients from Southern Europe. Conclusion: Ara h 9 is a new member of the LTP allergen family that seems to play an important role in peanut allergy for patients from the Mediterranean area.