Component-resolved Diagnosis Using the EuroPrevall Food Allergy Library

EuroPrevall is an EU-funded multidisciplinary integrated project including 62 partners from 22 countries. EuroPrevall aims at investigating the prevalence and distribution of food allergies throughout Europe in infants, children, adolescents, and adults. Threshold doses for different allergenic foods, the role of the environment in determining the different patterns of food allergy, the socioeconomic impact of food allergy, and the development of new diagnostic tools are studied. To facilitate improved in vitro diagnosis of food allergy a library of 31 purified recombinant or natural allergens from ten foods listed in the new labelling directive of the European Commission was established for developing novel diagnostics. As a follow up, preparation of eleven allergens from nuts, seeds and grains (also included in the EC Labelling directive) was performed accordingly. Additional allergens from allergenic fruits such as apple, peach and kiwi fruit were also included. A standard panel of serological and physico-chemical methods was applied for ensuring homogeneous quality of the allergen preparations. Component resolved diagnostics (CRD) in allergy designates approaches involving panels of pure allergen molecules or arrays of peptides derived from allergen sequences aimed at improving sensitivity of the detection of specific IgE, and, importantly, improving the correlation between a positive IgE test result and the clinical situation. In various studies marker allergens or epitopes have been suggested for severity or persistence of food allergic reactions or as markers for cross-reactivity patterns. In cross-sectional outpatient studies performed in twelve centres across Europe more than 1700 patients with a suggestive case history of food allergy have been included and sera samples have been provided to the EuroPrevall Serum Bank which is coordinated by the Paul- Ehrlich-Institut. The clinical relevance and threshold levels of allergenic foods are currently confirmed by DBPCFC in sub-samples of this patient panel. Serum samples of these patients will be used for comprehensive CRD studies in the last phase of the project. To evaluate the potential of the CRD method initial validation studies utilised sera from preciously studied patient panels with confirmed food allergy to (i) celeriac, (ii) shrimp and (iii) kiwi fruit. The allergen panels used include Api g 1, Api g 4 and Api g 5 from celeriac, the tropomyosins Pen a 1 and Cra c 1, arginine kinase, myosin light chain, troponin C, troponin I, sarcoplasmic calcium-binding protein, and triosephosphate isomerase from various crustacean species, and Act c 1, Act c 2 and Act c 3, profilin, cystatin, kiwellin and a new 40kDa allergen from kiwi. Clearly, the CRD approach revealed higher analytical sensitivity compared with that of extracts when results obtained with different individual allergens were combined. Moreover, the results provided evidence that specific IgE to some molecules may serve as biomarker for the severity of allergic reactions, such a tropomyosin in crustacean allergy and Act c 1 (actinidin) in kiwi allergy. However, critical interpretation of CRD results is required, as the problem of IgE cross-reactivity not accompanied by clinical symptoms is even enhanced with pure allergen molecules.