Abstract
We previously identified an expressed sequence tag clone, Der f 22, showing 41% amino acid identity to published Der f 2, and show that both genes are possible paralogues. The objective of this study was to characterize the genomic, proteomic and immunological functions Der f 22 and Der f 2. The full-length sequence of Der f 2 and Der f 22 coded for mature proteins of 129 and 135 amino acids respectively, both containing 6 cysteine residues. Phylogenetic analysis of known group 2 allergens and their homologues from our expressed sequence tag library showed that Der f 22 is a paralogue of Der f 2. Both Der f 2 and Der f 22 were single gene products with one intron. Both allergens showed specific IgE-binding to over 40% of the atopic patients, with limited of cross-reactivity. Both allergens were detected at the gut region of D. farinae by immunostaining. Der f 22 is an important allergen with significant IgE reactivity among the atopic population, and should be considered in the diagnostic panel and evaluated as future hypoallergen vaccine therapeutic target.
Highlights
Dermatophagoides farinae and D. pteronyssinus are the most important allergy-causing mites worldwide[1]
We identified an expressed sequence tag (EST) clone from our D. farinae library[5] with a low (41%) but significant homology to Der f 2 as observed by its three-dimensional structural homology and Pfam domain classification
This clone was named Der f 22, in accordance to the allergen nomenclature guidelines (WHO/Immunological Societies (IUIS), 1994), and its sequence deposited in Genbank (DQ643992.1) in June 2007
Summary
Dermatophagoides farinae and D. pteronyssinus are the most important allergy-causing mites worldwide[1]. More than thirty groups of dust-mite allergens have been identified, with the group 1 and 2 being major allergens, causing IgE-responses in about 80% of dust-mite sensitized individuals[2,3,4]. The identification of new allergens, especially those that show limited cross-reactivity to group 1 and 2 allergens will probably be useful in the diagnosis of allergy in this group of individuals. We report the characterization of an IgE-binding protein that showed low homology to previously identified allergens. This allergen was named Der f 22, which was accepted by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Sub-committee of Allergen Nomenclature. We characterize Der f 22 in terms of its gene organization, IgE-binding properties and potential biochemical function, in comparison to Der f 2
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