Usefulness of open mixed nut challenges to exclude tree nut allergy in children

BACKGROUND: To minimize the risk of accidental reactions, atopic children with multiple sensitizations to tree nuts are advised to avoid all nuts. Multiple food challenges would be needed to confirm the clinical relevance, but are too burdensome to be practical. The usefulness of open mixed nut challenges in terms of safety, reactions during challenge, tolerance of the challenge material, effect on the elimination diet and satisfaction of the parents was evaluated. FINDINGS: Open mixed nut challenges were performed in 19 children with a previous negative hazelnut challenge and long term elimination diet for tree nuts. Challenges were negative in 13 (68 %) children, in four (21 %) children (non-severe) allergic symptoms were observed. The challenges were well accepted, safe and efficient. We were able to avoid multiple nut challenges in 15 (79 %) children. CONCLUSIONS: Open mixed nut challenge can efficiently exclude multiple tree nut allergies in children with a lifelong nut free diet and low suspicion of clinical allergy

Further studies on the biological activity of hazelnut allergens

BACKGROUND Sensitization to hazelnut allergens vary depending on the geographic origin and age of the patients. The objective of this study was to further investigate the allergenic activity of hazelnut allergens using sera from patients recruited in various European regions and presenting different sensitization patterns to hazelnut proteins. METHODS Natural Cor a 11 and Cor a 9 were purified from hazelnut whereas Cor a 1 and Cor a 8 were produced as recombinant proteins (rCor a 1.04 and rCor a 8). Sera from hazelnut allergic patients were collected in France (n = 5), Switzerland (n = 2), Greece (n = 11) and Spain (n = 3), within the Europrevall project. Total and allergen-specific IgE were quantified by enzyme allergosorbent test and IgE immunoblot were performed using pooled sera from birch-pollen endemic region or from Greece. Histamine Release (HR) assays were performed with stripped basophils passively sensitized with individual sera and challenged by a hazelnut extract or the different hazelnut allergens. RESULTS As previously described, hazelnut allergic patients from Mediterranean countries are mainly sensitized to the nsLTP Cor a 8 whereas patients from France and Switzerland are sensitized to pollen-related allergens. Interestingly, an intermediate profile was evidenced in patients from Madrid. Hazelnut 7S globulin (Cor a 11) and 11S globulin (Cor a 9) were found to be minor allergens, recognized only by patients from Mediterranean countries. The biologic activity of the 4 tested allergens, analysed by HR assay, further confirmed the sensitization patterns, but also demonstrated the very high elicitation potency of Cor a 8. CONCLUSIONS This work, extending previously published researches, represents a step towards the better understanding of the complexity of hazelnut allergy and provides new data on the biological activity of hazelnut allergens and extracts