The Glycosylation Pattern of Common Allergens: The Recognition and Uptake of Der p 1 by Epithelial and Dendritic Cells Is Carbohydrate Dependent

Abstract

Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1–2, 1–3 and 1–6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production.

Glycoproteomic Analysis of Seven Major Allergenic Proteins Reveals Novel Post-translational Modifications

“…We have adopted a proteocentric approach for mass spectrometric characterization, which we have applied on key grass, tree pollen, and HDM allergens. The data presented provide an in depth analysis of the carbohydrate structure of Der p 1, Der p 2, Der f 1, Der f 2, Bet v 1, Phl p 1, and Phl p 5 exceeding previous investigations in the obtained level of detail (21,24,41). We identified novel PTMs of HDM allergens as well as more complex glycan structures than previously reported on the major grass pollen group 1 and 5 allergens.…”

“…N-linked heterogeneous glycosylation of the major allergens of Dermatophagoides pteronyssinus HDM 1 and 2 (Der p 1 and Der p 2) has been demonstrated to influence structure, processing, function, and immunogenicity of these allergens (44 -46), although the precise glycan structures remain unre-solved (41,47). With bottom up mass spectrometry, we demonstrated that the natural Der p 1 is N-glycosylated with one or two HexNAc residues at Asn 150 (supplemental Fig.…”

Allergens of <b><i>Blomia tropicalis</i></b>: An Overview of Recombinant Molecules

“…Glycan modifications in allergens might be directly involved in antigen uptake and presentation. Moreover, cross-reactive carbohydrate determinants have been reported to induce carbohydrate-specific IgE antibodies [81,82,83]. Some studies have experimentally identified glycosylation sites in natural allergens as well as in recombinant allergens, highlighting their importance for IgE binding and for their recognition by innate immune cells [82,84,85,86].…”

“…Moreover, cross-reactive carbohydrate determinants have been reported to induce carbohydrate-specific IgE antibodies [81,82,83]. Some studies have experimentally identified glycosylation sites in natural allergens as well as in recombinant allergens, highlighting their importance for IgE binding and for their recognition by innate immune cells [82,84,85,86]. For Blomia allergens, on the other hand, data on glycosylation have been mostly restricted to bioinformatics predictions [29,30,62,67,70,74].…”

Exacerbating Factors Induce Different Gene Expression Profiles in Peripheral Blood Mononuclear Cells from Asthmatics, Patients with Chronic Obstructive Pulmonary Disease and Healthy Subjects

“…Kashyap et al [59] also noted that murine lung epithelial cells and dendritic cells produce TSLP in response to HDM extract. The ability of Der p 1 to induce TSLP secretion by BEAS-2B, a human bronchial epithelial cell line, was further confirmed by Al-Ghouleh et al [60]. …”