D1.315 - IgE antibody function and mast cell activation to egg in children undergoing baked and loosely cooked egg challenges

Egg allergy is one of the most common food allergies in childhood and frequently resolves over time. Accurate diagnosis of allergy and tolerance remains challenging, as conventional tests such as skin prick test (SPT) and specific IgE (sIgE) have insufficient predictive value. Functional assays assessing effector cell activation, such as the mast cell activation test (MAT), may improve diagnosis and provide insight into antibody-mediated mechanisms of effector cell response to allergen stimulation.

Participants in the BAT2 egg study had SPT and blood collection for sIgE, BAT and MAT, and underwent double-blind placebo-controlled food challenge (DBPCFC) to baked egg and, if tolerated, to loosely cooked egg. LAD2 mast cells sensitised with patients’ plasma were stimulated with egg extract and CD63 expression was measured by flow cytometry. Diagnostic performance of MAT, BAT, SPT and sIgE was compared with the outcome of DBPCFC. Specific IgE characteristics such as levels, specific activity, avidity and diversity were assessed, and egg-specific IgG4/IgE ratios were calculated and related to effector cell activation.

Participants with completed outcomes (n=133) were classified as baked egg allergic (BEA, n=58), baked egg tolerant (BET, n=16) or egg tolerant (ET, n=59).

MAT responses to egg extract were significantly higher in BEA children compared with BET and ET groups (p<0.001). MAT distinguished allergic from tolerant children with an area under the ROC curve (95% CI) of 0.749 (0.663–0.835) for BE allergy and 0.704 (0.616-0.793) for LCE allergy. Sensitivity/specificity of MAT’s optimal cut-off were 52%/89% for BE allergy and 70%/66% for LCE allergy. Diagnostic accuracy of MAT was 67% for both forms of egg allergy. MAT and BAT were moderately correlated (Rs=0.431, p<0.001). Higher egg-specific IgE levels (Rs=480, p<0.001), specific activity (Rs=0.355, p<0.001) and avidity (Rs=0.305, p=0.009) were directly correlated whereas higher egg-specific IgG4/IgE ratios (Rs=-0.289, p<0.001) were inversely correlated with MAT to egg.

MAT identifies clinical phenotypes of egg allergy with high specificity, but lower sensitivity compared to BAT. MAT constitutes a valuable in vitro tool to assess IgE functional capacity and the inhibitory role of IgG4, particularly when fresh blood samples for BAT are not available.