Background: Peach allergy is a prevalent cause of food allergy. Despite the repertoire of allergens available for molecular diagnosis, IgE to individual peach allergens may still be undetectable in some patients who present symptoms after ingestion. The objective of this study was to investigate the allergen profile of patients with symptoms induced by peach.
Materials and Methods: We performed an exploratory retrospective study of 42 patients presenting symptoms after ingestion of peach. The allergen profile of individual patients was investigated using immunoblot. A serum pool was prepared with sera that recognized a 70-kDa band. The pool was used to detect this protein in peach peel and pulp and to identify the 70-kDa protein in 2D immunoblot. Spots recognized in the 2D immunoblot were sequenced using LC-MS/MS. Inhibition studies were performed with peach peel and almond.
Results: The immunoblot revealed that 22 patients (52.4%) recognized the 70-kDa protein in peach peel and pulp. Two spots were observed in 2D-PAGE, and both were identified as (R)-mandelonitrile lyases (RMLs) showing high amino acid similarity with Pru du 10. The RMLs were partially inhibited with an almond extract. No association was found between symptoms and sensitization to RML. RMLsensitized patients were older and reported pollen-associated respiratory symptoms more frequently than patients whose results were negative for this protein.
Conclusions: We identified a new peach allergen, an RML, which was a homolog of Pru du 10 and was recognized by 52% of the population.

Key words: Peach allergy, Peach allergen, Mandelonitrile lyase, Food allergy, Homolog of Pru du 10