Influence of hazelnut varieties on Cor a 15 IgE-binding in hazelnut allergic pediatric patients

Background The lipophilic allergens, such as oleosins, are often poorly investigated and generally underrepresented in diagnostic tests. In addition to Cor a 12 and Cor a 13, the immunogenic power of the oleosin Cor a 15 was recently demonstrated for the hazelnut allergic pediatric patients. The aim of this work was: (i) to evaluate whether there are hazelnut varieties with reduced or increased Cor a 15 expression, (ii) to investigate whether the immunorecognition of Cor a 15 by hazelnut allergic subjects shows to be different according to hazelnut cultivars. Method Seventeen hazelnut cultivars, mainly from Italy, Turkey and Spain, were collected from an experimental hazel grove in Italy. A protocol optimized for the extraction of oil bodies associated proteins and the LDS-PAGE protein separation under reducing condition were performed. The pattern of specific IgE binding of the oil body protein extracts was determined by immunoblotting, using a pool of sera from 20 pediatric subjects with a convincing history of hazelnut allergy. The tryptic digested proteins were identified by means of LC-MS/MS. Results The electrophoresis profile, confirmed by the LC-MS/MS protein identification, showed the presence of all the three allergenic oleosins Cor a 12, Cor a 13 and Cor a 15 in all the assessed hazelnut varieties. Cor a 15 resulted to be more expressed in Mortarella, Nocchione and Maraviglia varieties, conversely a reduced expression was observed in Tonda Gentile delle Langhe, Tonda di Giffoni and Bardina. The immunoblotting experiments showed the immunorecognition of Cor a 15 from all the tested varieties regardless of the oleosin abundance. Conclusion These results demonstrate that oleosins, especially Cor a 15, are highly conserved allergen between cultivars, highly recognized by Italian pediatric allergic subjects. Although, no significant differences in the immunoreactivity were found among hazelnut varieties, this analytical approach has a potential for the identification of varieties with reduced or variable allergen content.