Nitration of the Pollen Allergen Bet v 1.0101 Enhances the Presentation of Bet v 1-Derived Peptides by HLA-DR on Human Dendritic Cells

Anette C Karle,Gottfried F Fischer,Albert Duschl,Gertie J Oostingh,Fatima Ferreira,Sonja Mutschlechner,Barbara Bohle,Anne B Vogt,Peter Lackner,Geetha P Bansal

doi:10.1371/journal.pone.0031483

Abstract

Nitration of pollen derived allergens can occur by NO2 and ozone in polluted air and it has already been shown that nitrated major birch (Betula verrucosa) pollen allergen Bet v 1.0101 (Bet v 1) exhibits an increased potency to trigger an immune response. However, the mechanisms by which nitration might contribute to the induction of allergy are still unknown. In this study, we assessed the effect of chemically induced nitration of Bet v 1 on the generation of HLA-DR associated peptides. Human dendritic cells were loaded with unmodified Bet v 1 or nitrated Bet v 1, and the naturally processed HLA-DR associated peptides were subsequently identified by liquid chromatography-mass spectrometry. Nitration of Bet v 1 resulted in enhanced presentation of allergen-derived HLA-DR-associated peptides. Both the copy number of Bet v 1 derived peptides as well as the number of nested clusters was increased. Our study shows that nitration of Bet v 1 alters antigen processing and presentation via HLA-DR, by enhancing both the quality and the quantity of the Bet v 1-specific peptide repertoire. These findings indicate that air pollution can contribute to allergic diseases and might also shed light on the analogous events concerning the nitration of self-proteins.

Highlights

In recent decades, studies have been addressing a possible contribution of traffic related air pollution to allergic diseases [1,2,3,4,5,6]
Since changes in the pattern of presented HLA-DR associated peptides on dendritic cells (DCs) can change the recognition by T lymphocytes, and since the conversion of tyrosine to nitrotyrosine has already been shown to affect the reactivity of T cells for other proteins [18,19], we addressed the question whether peripheral blood mononuclear cells (PBMCs) loaded with Bet v 1 nitro can activate T lymphocytes more efficiently than PBMCs loaded with unmodified Bet v 1
From this total number of different identified peptides, an average of 0–0.8% of the peptides were derived from Bet v 1 in samples generated from DCs loaded with unmodified Bet v 1 and 0.3–7.2% of the total peptides were derived from Bet v 1 nitro in samples generated from DCs loaded with Bet v 1 nitro

Summary

Introduction

Studies have been addressing a possible contribution of traffic related air pollution to allergic diseases [1,2,3,4,5,6]. In sera of birch pollen-allergic patients, the levels of IgE recognizing nitrated major birch pollen allergen Bet v 1.0101 (referred to as Bet v 1 nitro) were significantly higher compared to IgE specific for unmodified Bet v 1.0101 (Bet v 1) [6] and in mouse models, nitrated Bet v 1 and nitrated Ovalbumin are more potent allergens when compared to their unmodified forms [6] These findings suggest that post-translational modifications (PTMs), such as nitration, can increase the potential of pollen allergens to trigger immune responses and might play a role in the emergence of allergies. These findings suggest that PTMs might alter processing and presentation of proteins by professional antigen presenting cells, leading to the generation of new antigenic epitopes and potential induction of a T cell response [19,22]

Methods

Results

Conclusion