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Clin Exp Allergy. 2016 Aug;46(8):1120-1128. doi: 10.1111/cea.12764. Epub 2016 Jun 27.

Conformational IgE epitopes of peanut allergens Ara h 2 and Ara h 6.

Author information

1
Division of Allergy and Clinical Immunology, Departments of Medicine and Immunology, University of Colorado Denver, Aurora, CO.
2
Sealy Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology, The University of Texas Medical Branch, Galveston, TX 77555.
3
Molecular Cellular Developmental Biology, University of Colorado, Boulder, CO.
#
Contributed equally

Abstract

BACKGROUND:

Cross-linking of IgE antibody by specific epitopes on the surface of mast cells is a prerequisite for triggering symptoms of peanut allergy. IgE epitopes are frequently categorized as linear or conformational epitopes. Although linear IgE-binding epitopes of peanut allergens have been defined, little is known about conformational IgE-binding epitopes.

OBJECTIVE:

To identify clinically relevant conformational IgE epitopes of the two most important peanut allergens, Ara h 2 and Ara h 6, using phage peptide library.

METHODS:

A phage 12mer peptide library was screened with allergen-specific IgE from 4 peanut-allergic patients. Binding of the mimotopes to IgE from a total of 29 peanut-allergic subjects was measured by ELISA. The mimotope sequences were mapped on the surface areas of Ara h 2 and Ara h 6 using EpiSearch.

RESULTS:

Forty-one individual mimotopes were identified that specifically bind anti- Ara h 2/Ara h 6 IgE as well as rabbit anti-Ara h 2 and anti-Ara h 6 IgG. Sequence alignment showed that none of the mimotope sequences match a linear segment of the Ara h 2 or Ara h 6 sequences. EpiSearch analysis showed that all the mimotopes mapped to surface patches of Ara h 2 and Ara h 6. Eight of the mimotopes were recognized by more than 90% of the patients, suggesting immunodominance. Each patient had distinct IgE recognition patterns but the recognition frequency was not correlated to the concentration of peanut specific IgE or to clinical history.

CONCLUSIONS:

The mimotopes identified in this study represent conformational epitopes. Identification of similar surface patches on Ara h 2 and Ara h 6 further underscores the similarities between these two potent allergens.

KEYWORDS:

Ara h 2; Ara h 6; EpiSearch; IgE; allergens; epitopes; mimotopes; peanut; phage display

PMID:
27238146
PMCID:
PMC4963300
DOI:
10.1111/cea.12764
[Indexed for MEDLINE]
Free PMC Article

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