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.