Ara h 2 Peptide Mix Improves the Diagnosis of Peanut Allergy and Is Relevant for Ara h 2-Induced Mast Cell Activation.

BACKGROUND:A precise diagnosis of peanut allergy is extremely important. We identified 4 Ara h 2 peptides that improved Ara h 2-specific IgE (sIgE) diagnostic accuracy. OBJECTIVE:To assess the diagnostic utility of sIgE to the mixture of these peptides and their role in mast cell response to peanut allergens. METHODS:sIgE to the peptide mix was determined using ImmunoCAP. Its diagnostic utility was compared with Ara h 2-sIgE and sIgE to the individual peptides. The functional relevance of the peptides was tested on the mast cell activation test using laboratory of allergic diseases 2 cell line and flow cytometry. RESULTS:A total of 52 peanut-allergic (PA), 36 peanut-sensitized but tolerant, and 9 nonsensitized nonallergic children were studied. Peptide mix-sIgE improved the diagnostic performance of Ara h 2-sIgE compared with Ara h 2-sIgE alone (area under the receiver operating characteristic curve .92 vs .89, respectively; P = .056). The sensitivity and specificity of Ara h 2-sIgE combined with the peptide mix were 85% and 96%, respectively. sIgE to individual peptides had the highest specificity (91%-96%) but the lowest sensitivity (10%-52%) compared with Ara h 2-sIgE (69% specificity and 87% sensitivity) or with peptide mix-sIgE (82% specificity and 63% sensitivity). Peptide 3 directly induced mast cell activation, and the peptide mix inhibited Ara h 2-induced activation of mast cells sensitized with plasma from Ara h 2-positive PA patients. CONCLUSIONS:sIgE to the peptide mix improved the diagnostic performance of Ara h 2-sIgE similarly to sIgE to individual peptides. The peptides interfered with Ara h 2-induced mast cell activation, confirming its relevance in peanut allergy.