Identification and characterization of the IgEome and its role and relevance in food allergy

• Applicant: Dr. Jörg Scheffel
• Subject Area: Clinical Immunology and Allergology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 409525714

Food allergy, a typical type 1 hypersensitivity reaction, is characterized by IgE/FcRI-mediated activation of mast cells (MCs) and basophils. Crosslinking of IgE-FcεRI-complexes via allergens, including food, results in MC activation and immediate mediator release like histamine and other proinflammatory factors being responsible for typical symptoms like itching, burning and swelling around the mouth, swelling of the face or eyes, urticaria, diarrhea and abdominal pain and in severe cases anaphylaxis. However, although IgE is essential for MC and basophil activation, it is still unknown why some people, sensitized to food allergens, do not exhibit clinical symptoms. Glycosylation is one major post-translational modification known to affect many physicochemical properties of a protein including size, folding or charge thereby affecting its effector functions. Glycans are covalently linked to proteins mainly to the oxygen atom of a serine or threonine residue (O-linked) or to a nitrogen atom of an asparagine residue (N-linked) and can significantly vary in their sequence and length. IgE, the most heavily glycosylated immunoglobulin, has seven consensus sequences for N-linked glycans, while only six of these sites are occupied. Even though conflicting studies made it hard to determine functional relevance of IgE glycosylation, recent studies have confirmed an absolute requirement of N394 glycosylation for efficient binding of IgE to FcεRI and subsequently for MC activation. In addition, sialylation of IgE may be a strong predictor and biomarker of peanut allergy. Unlike the genome and proteome, the glycome is synthesized in a non-template procedure and depends on the availability of involved enzymes and sugar precursors. We hypothesize that 1) IgE glycosylation as a predictor of food allergy, 2) IgE glycosylation patterns may change upon modified food intake and 3) correlate with clinical markers like positive SPT, tryptase levels and threshold during oral food challenge (OFC) as well as the changes in adaptive and innate immune cells. To test our hypothesis, we will first investigate the IgE glycome in food sensitized patients that are either tolerant or allergic and further will assess IgE glycosylation patterns in selected patients before and after modified food elimination therapy to track changes due to alternated diet. To prove the functional relevance of different glycosylation patterns we will assess MC activation using patient derived IgE. Additionally, we will determine effects of different glycosylated IgE on antigen and receptor binding using Bio-Layer Interferometrie (BLI). Our results, identification of allergy specific glycome patterns and their relevance in antigen and IgE mediated MC activation, might help to better understand the underlying mechanisms of food allergy and the role played by specific IgE. Furthermore, the IgE glycome might be a good biomarker candidate or a useful treatment target.

• DFG Programme: Clinical Research Units
• Subproject of: KFO 339: Food Allergy and Tolerance (Food@)