期刊
JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY
卷 132, 期 3, 页码 696-+出版社
MOSBY-ELSEVIER
DOI: 10.1016/j.jaci.2013.03.021
关键词
Grass pollen allergy; recombinant allergen; Phl p 4; Sec c 4; cross-reactive carbohydrate determinant; basophil release assay; dehydrogenase; bicovalently attached flavin adenine dinucleotide
资金
- Austrian National Science Fund (FWF) through the SFB projects [F1805, F4604]
- Austrian Science Foundation (FDF)
Background: Phl p 4 is a major pollen allergen but exhibits lower allergenicity than other major allergens. The natural protein is glycosylated and shows cross-reactivity with related and structurally unrelated allergens. Objective: We sought to determine the high-resolution crystal structure of Phl p 4 and to evaluate the immunologic properties of the recombinant allergen in comparison with natural Phl p 4. Methods: Different isoallergens of Phl p 4 were expressed, and the nonglycosylated mutant was crystallized. The specific role of protein and carbohydrate epitopes for allergenicity was studied by using IgE inhibition and basophil release assays. Results: The 3-dimensional structure was determined by using x-ray crystallography at a resolution of 1.9 angstrom. The allergen is a glucose dehydrogenase with a bicovalently attached flavin adenine dinucleotide. Glycosylated and nonglycosylated recombinant Phl p 4 showed identical inhibition of IgE binding, but compared with natural Phl p 4, all recombinant isoforms displayed a reduced IgE-binding inhibition. However, the recombinant protein exhibited an approximately 10-fold higher potency in basophil release assays than the natural protein. Conclusion: The crystal structure reveals the compact globular nature of the protein, and the observed binding pocket implies the size of the natural substrate. Plant-derived cross-reactive carbohydrate determinants (CCDs) appear to reduce the allergenicity of the natural allergen, whereas the Pichia pastoris-derived glycosylation does not. Our results imply yet undescribed mechanism of how CCDs dampen the immune response, leading to a novel understanding of the role of CCDs.
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