Ara h 7 isoforms share many linear epitopes: Are 3D epitopes crucial to elucidate divergent abilities?

Abstract

Background The peanut allergens Ara h 2, h 6, and h 7 are potent allergens and can trigger severe reactions. Ara h 7 consists of three isoforms differing in their ability to induce basophil degranulation, whereas the ability of Ara h 7.0201 is comparable to Ara h 2 and 6 as shown in previous literature. Objective To identify linear epitopes of Ara h 7.0101, Ara h 7.0201 and Ara h 7.0301 recognized by IgE and IgG4 from patients sensitized to Ara h 7 and to investigate their potential to elucidate divergent abilities of the Ara h 7 isoforms in inducing basophil activation. Methods Linear epitopes recognized by IgE and IgG4 were mapped by peptide microarray analysis containing 15‐mer peptides of Ara h 2.0201, 6, 7.0101, 7.0201 and 7.0301 and 39 peanut allergic patients sensitized to Ara h 7 (discovery). For validation, 20‐mer peptides containing the minimal epitope and surrounding amino acids were incubated with 25 sensitized patients and 10 controls (validation). Results Three out of 14 linear epitopes were unique for each isoform (Ara h 7.0101: aa 97‐109; Ara h 7.0201: aa 122‐133; Ara h 7.0301: aa 65‐74) but scarcely recognized by IgE. The main linear IgE epitope (aa 51‐57) located in the long flexible loop of all Ara h 7 isoforms was bound by antibodies from 31% of the patients (discovery and validation cohort). Regarding IgG4, 55% of the patients recognized an epitope present on all isoforms (aa 55‐65), whereas epitope aa 129‐137, only present on Ara h 7.0101/0.0301, was recognized by 38% of the patients. Recognition was highly individual, although 20% of the patients recognized any linear epitope neither by IgE nor by IgG4 despite a low mean z‐score of ≥ 1.7. Remarkably, only 50% of the patients recognized one or more epitopes by IgE. Conclusion & Clinical Relevance Ara h 7 isoforms share many linear epitopes being easily accessible for antibody binding. Unique epitopes, essential to elucidate divergent potencies, were scarcely recognized, suggesting a crucial involvement of conformational epitopes.

Improving Diagnostic Accuracy in Food Allergy

“…51,52 The evidence of clinical utility of such tests has been recently systematically reviewed. 53,54 The most recent studies have focused on peanut [55][56][57][58] and cow's milk 59,60 allergies as well as allergies to shellfish [61][62][63] and legumes. [64][65][66] Using a peptide microarray, Caubet et al 60 identified a greater intensity and broader diversity of IgE binding in children with persistent CMA, which decreased as children became tolerant.…”

Detection of specific IgE against linear epitopes from Gal d 1 has additional value in diagnosing hen’s egg allergy in adults

“…The microarray incubation was performed as previously described 14 . Briefly, patient sera were diluted 1:4 in WSUB and incubated overnight.…”

Developments allergy in 2019 through the eyes of clinical and experimental allergy, part I mechanisms

“…Ehlers and colleagues found that they have similar linear epitopes and so they must therefore differ in terms of their conformational epitopes. 73…”

“…Three have been identified with differing potential to degranulate basophils in an ex vivo system. Ehlers and colleagues found that they have similar linear epitopes and so they must therefore differ in terms of their conformational epitopes 73 …”