High-resolution epitope mapping by AllerScan reveals relationships between IgE and IgG repertoires during peanut oral immunotherapy

Genghao Chen,Ellen L Shrock,Mamie Z Li,Jonathan M Spergel,Kari C Nadeau,Jacqueline A Pongracic,Dale T Umetsu,Rima Rachid,Andrew J Macginnitie,Wanda Phipatanakul,Lynda Schneider,Hans C Oettgen,Stephen J Elledge

doi:10.1016/j.xcrm.2021.100410

Abstract

SummaryPeanut allergy can result in life-threatening reactions and is a major public health concern. Oral immunotherapy (OIT) induces desensitization to food allergens through administration of increasing amounts of allergen. To dissect peanut-specific immunoglobulin E (IgE) and IgG responses in subjects undergoing OIT, we have developed AllerScan, a method that leverages phage-display and next-generation sequencing to identify the epitope targets of peanut-specific antibodies. We observe a striking diversification and boosting of the peanut-specific IgG repertoire after OIT and a reduction in pre-existing IgE levels against individual epitopes. High-resolution epitope mapping reveals shared recognition of public epitopes in Ara h 1, 2, 3, and 7. In individual subjects, OIT-induced IgG specificities overlap extensively with IgE and exhibit strikingly similar antibody footprints, suggesting related clonal lineages or convergent evolution of peanut-specific IgE and IgG B cells. Individual differences in epitope recognition identified via AllerScan could inform safer and more effective personalized immunotherapy.

Highlights

Peanut allergy is emerging as a growing health challenge in children, currently affecting 2.2% of the pediatric and 1.8% of the adult populations in the United States.[1,2] Individuals with peanut allergy harbor immunoglobulin E (IgE) antibodies directed against peanut component proteins
Development of the peanut AllerScan library To map epitopes targeted by the antibody response to peanut in allergic subjects, we constructed a phage-display library of 397 20-mer peptides tiling every 10 amino acids across the sequences of all 12 peanut allergens listed in the World Health Organization and International Union of Immunological Societies (WHO/IUIS) Allergen Nomenclature Sub-committee database at the time of library design (Table S1)
To perform an AllerScan reaction, we mixed this peanut saturation mutagenesis phage-display library with serum, immunoprecipitated IgE or IgG antibodies, and sequenced bound phage to identify the peptides recognized by antibodies

Summary

Introduction

Peanut allergy is emerging as a growing health challenge in children, currently affecting 2.2% of the pediatric and 1.8% of the adult populations in the United States.[1,2] Individuals with peanut allergy harbor immunoglobulin E (IgE) antibodies directed against peanut component proteins. Bound to the high-affinity IgE receptor FcεRI on the cell surface, IgE antibodies trigger the activation of tissue-resident mast cells and circulating basophils upon allergen encounter. This leads to the release of vasoactive mediators, including histamine, that cause allergic reactions. The fact that not all subjects who are sensitized (i.e., who produce IgE antibodies) to food allergens exhibit allergic reactions suggests that there are factors that counteract IgE-mediated responses. Antibodies of the IgG class, which increase during the natural resolution of food allergies, may play an important role in this regard[3,4,5] and have been shown to suppress IgE-induced allergic reactions by (1) competing with IgE for binding allergen epitopes,[6] (2) accelerating allergen clearance by forming immune complexes, and (3) preventing mast cell activation by binding to the inhibitory IgG receptor, FcgRIIb.[6,7,8,9]

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Results

Discussion

Conclusion