ALLERGEN NOMENCLATURE
WHO/IUIS Allergen Nomenclature Sub-Committee

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Carbohydrate Epitopes Currently Recognized as Targets for IgE Antibodies

A paper on carbohydrate epitopes recognized by IgE antibodies was published in 2021 in Allergy as the result of a Working Group originated within the WHO/IUIS Allergen Nomenclature meeting during the EAACI Congress in Lisbon in 2019:

Platts-Mills TA, Hilger C, Jappe U, van Hage M, Gadermaier G, Spillner E, Lidholm J, Keshavarz B, Aalberse RC, van Ree R, Goodman RE, Pomés A. Carbohydrate epitopes currently recognized as targets for IgE antibodies. Allergy 2021; 76: 2383-94; doi: 10.1111/all.14802.
Free full text at PubMed Central

Abstract

Until recently, glycan epitopes have not been documented by the WHO/IUIS Allergen Nomenclature Sub-Committee. This was in part due to scarce or incomplete information on these oligosaccharides, but also due to the widely held opinion that IgE to these epitopes had little or no relevance to allergic symptoms. Most IgE-binding glycans recognized up to 2008 were considered to be ""classical" cross-reactive carbohydrate determinants (CCD) that occur in insects, some helminths and throughout the plant kingdom. Since 2008, the prevailing opinion on lack of clinical relevance of IgE-binding glycans has been subject to a reevaluation. This was because IgE specific for the mammalian disaccharide galactose-alpha-1,3-galactose (alpha-gal) was identified as a cause of delayed anaphylaxis to mammalian meat in the United States, an observation that has been confirmed by allergists in many parts of the world. Several experimental studies have shown that oligosaccharides with one or more terminal alpha-gal epitopes can be attached as a hapten to many different mammalian proteins or lipids. The classical CCDs also behave like haptens since they can be expressed on proteins from multiple species. This is the explanation for extensive in vitro cross-reactivity related to CCDs. Because of these developments, the Allergen Nomenclature Sub-Committee recently decided to include glycans as potentially allergenic epitopes in an adjunct section of its website (www.allergen.org). In this article, the features of the main glycan groups known to be involved in IgE recognition are revisited, and their characteristic structural, functional, and clinical features are discussed.

Table 1. Groups of oligosaccharides that are recognized as targets of IgE.

Group Name Examples
Clinical significance has been reported for some of these glycans.
A N-Glycans ("Classical" cross-reactive carbohydrate determinants or CCDs)
  • Glycans on horseradish peroxidase
  • Glycans on pineapple bromelain
  • Glycans on insect venoms (Phospholipase A2, hyaluronidases)
B Mammalian non-human oligosaccharides
  • Disaccharide galactose-alpha-1,3-galactose (eg, in bovine thyroglobulin, cetuximab, red meat, tick bites)
  • Monosaccharide N-glycolyl neuraminic acid
Clinical significance of these glycans needs further investigation.
C O-Glycans
  • Gum arabic from acacia (used as an emulsifier and a thickening agent)
  • Glycans in some yeasts and molds
  • Single hydroxyproline-linked β-arabinoses in Art v 1/Amb a 4
D Glycans from nematode parasites
  • Glycans on schistosomes and schistosome soluble egg antigens (SEA)
E Galacto-oligosaccharides
  • Commercially produced prebiotics consisting of mixtures of oligomers containing glucose and polymerized galactose, produced from milk through enzymatic conversion of lactose by bacterial beta-galactosidase