Tree nut allergic individuals are often sensitised towards multiple nuts and seeds. The underlying cause behind a multi-sensitisation for cashew nut, hazelnut, peanut and birch pollen is not always clear. We investigated whether IgE cross-reactivity between cashew nut-, hazelnut- and peanut proteins exists in children that are multi-allergic to these foods using a novel IMMULITE^®-based inhibition methodology, and investigated which allergens might be responsible. In addition, we explored if an allergy to birch pollen might play a role in this cosensitisation for cashew nut, hazelnut and peanut.

Serum of five children with a confirmed cashew nut allergy and suffering from allergic symptoms after eating peanut and hazelnut were subjected to inhibition immunoassays using the IMMULITE^® 2000 Xpi. Serum specific IgE to seed storage allergens and pathogenesis related protein 10 (PR10) allergens were determined and used for molecular multicomponent allergen correlation analyses with observed clinical symptoms and obtained inhibition data.

IgE cross-reactivity was observed in all patients. Hazelnut extract was a strong inhibitor of cashew nut sIgE (46.8%) while cashew nut extract was less able to inhibit hazelnut extract (22.8%). Peanut extract showed the least inhibition potency. Moreover, there are strong indications that a birch pollen sensitisation to Bet v 1 might play a role in the observed symptoms provoked upon ingestion of cashew nut and hazelnut.

Molecular diagnostic testing by measuring specific sIgE againstindividual allergen molecules or components using purified orrecombinant allergens (CRD) provides detailed information onsensitization patterns to allergologists and enables a more accurateinterpretation of allergic symptoms by distinguishing clinically relevantfood protein sensitisation from non-relevant sensitisation that does notcause systemic reactions. Moreover, such a CRD analysis can broadenour understanding of which IgE cross-reactivity reactions betweenfoods are to be expected in a patient group, which may guide dietaryadvice. We have demonstrated that the IMMULITE® technique canindeed be applied to evaluate IgE cross-reactivity between proteinextracts and between specific allergens. This allowed us to evaluatewhether clinical symptoms in children co-sensitised against cashewnut, hazelnut and peanut were possibly allergen type related andresulted from a primary reaction or from cross-reactivity tohomologous allergens in each of the tested foods.

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Allison Grey 
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Journal of Clinical chemistry and Laboratory Medicne
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