Improvement of in vitro food allergy diagnostics by identifying unique antibody traits

Abstract

Food allergy is a major health concern, which affects around 3% of the Western population. The backbone of food allergy management is still comprised of emergency treatment prescription and food restrictions. To avoid unnecessary food restrictions of patients with a suspected food allergy, accurate diagnostics are key. So far, the double-blind placebo-controlled food challenge is the gold standard in food allergy diagnostics, although this method is burdensome for the patient, expensive and requires dedicated hospital facilities. In contrast, the measurement of sIgE antibodies against certain allergens is a minimally invasive diagnostic tool. However, sIgE measurements can yield “false-negative” - undetectable sensitization despite allergy - and “false-positive” test outcomes - detectable sensitization despite tolerance. With a view to prevent false-negative and false-positive sIgE test outcomes, we studied traits of patients’ (IgE) antibodies. False-negative test outcomes can be reduced by identifying responsible allergens that are not yet available for sIgE measurements in clinical practice. In macadamia nut allergy, a newly identified macadamia nut allergen, which belongs to the 7S vicilin family, was particularly recognized by sIgE from patients with moderate to severe symptoms. This will support discrimination between mild and severe macadamia nut allergy. False-positive test outcomes can be reduced by identifying specific epitopes that are only recognized by sIgE of allergic patients. In this regard, sIgE binding to epitopes of the hen’s egg allergen Gal d 1 was able to discriminate between hen’s egg allergic and tolerant adults, while sIgE binding to the full-length allergen was not. Besides binding characteristics, antibody differences were studied on DNA level by generating allergen-specific human monoclonal antibodies (mAbs) from peripheral blood of peanut-allergic and peanut-tolerant patients sensitized to the major peanut allergens Ara h 2 and 6. Allergen-specific mAbs from peanut-allergic patients (89%) were more often comprised of V genes belonging to the VH3 gene family compared with specific mAbs from peanut-tolerant patients (54%) and non-atopic donors (63%). These differences on DNA level showed the potential to discriminate between peanut allergy and tolerance despite sIgE sensitization. These unique antibody traits provide the fundament for the development of improved, minimally invasive food allergy diagnostics, which will decrease patients’ burden by reducing the need for cumbersome food challenges in the future.