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.

Nitration of pollen derived allergens can occur by NO(2) 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.

Naturally processed T cell-activating peptides of the major birch pollen allergen.

BACKGROUND: Although antigen processing and presentation of allergens to CD4(+)T lymphocytes are key events in the pathophysiology of allergic disorders, they still remain poorly understood. OBJECTIVE: To investigate allergen processing and presentation by dendritic cells using the major birch pollen allergen Bet v 1 as a model. METHODS: Endolysosomal extracts of dendritic cells derived from patients with birch pollen allergy were used to digest Bet v 1. Dendritic cells were pulsed with Bet v 1, and peptides were eluted from MHC class II molecules. Peptides obtained by either approach were sequenced by tandem mass spectrometry. Bet v 1-specific T-cell cultures were stimulated with HLA-DR-eluted Bet v 1-derived peptides. Bet v 1-specific T-cell lines were generated from each patient and analyzed for epitope recognition. RESULTS: A high proportion of Bet v 1 remained intact for a long period of endolysosomal degradation. The peptides that appeared early in the degradation process contained frequently recognized T-cell epitopes. Bet v 1-derived peptides eluted from MHC class II molecules corresponded to those generated by endolysosomal degradation, matched known T-cell epitopes, and showed T cell-activating capacity. The Bet v 1-specific T-cell line of each individual harbored T cells reactive with peptides located within the MHC class II-eluted Bet v 1-derived sequences demonstrating their occurrence in vivo. CONCLUSION: We report for the first time how epitopes of allergens are generated and selected for presentation to T lymphocytes. The limited susceptibility of Bet v 1 to endolysosomal processing might contribute to its high allergenic potential.