Der f 34, a Novel Major House Dust Mite Allergen Belonging to a Highly Conserved Rid/YjgF/YER057c/UK114 Family of Imine Deaminases

Abstract

The high prevalence of house dust mite (HDM) allergy is a growing health problem worldwide, and the characterization of clinically important HDM allergens is a prerequisite for the development of diagnostic and therapeutic strategies. Here, we report a novel HDM allergen that belongs structurally to the highly conserved Rid/YjgF/YER057c/UK114 family (Rid family) with imine deaminase activity. Isolated HDM cDNA, named der f 34, encodes 128 amino acids homologous to Rid-like proteins. This new protein belongs to the Rid family and has seven conserved residues involved in enamine/imine deaminase activity. Indeed, we demonstrated that purified Der f 34 had imine deaminase activity that preferentially acted on leucine and methionine. Native Der f 34 showed a high IgE binding frequency as revealed by two-dimensional immunoblotting (62.5%) or ELISA (68%), which was comparable with those of a major HDM allergen Der f 2 (77.5 and 79%, respectively). We also found that Der f 34 showed cross-reactivity with another prominent indoor allergen source, Aspergillus fumigatus. This is the first report showing that the Rid family imine deaminase represents an additional important pan-allergen that is conserved across organisms.Asthma is a serious global health problem that significantly reduces quality of life. In a cross-sectional World Health Organization survey of 178,215 individuals from 70 countries conducted in 2002-2003, it was estimated that 4.3% of adults (range, 0.2-21.0%) had been diagnosed with asthma by a medical doctor (1). Inhaled airborne allergens cause allergic inflammation via the cross-linking of allergen-specific IgEs bound on high affinity IgE receptor (FceRI) located on the surface of airway or lung mast cells, causing the secretion of inflammatory chemical mediators (e.g. histamine and leukotrienes) from activated mast cells. House dust mites (HDMs) 5 and fungi are major sources of airborne allergens and trigger asthmatic attacks in allergic patients concomitant with air pollutants (2).Allergen-specific immunotherapy (AIT) is the only curative treatment for allergic asthma that changes the natural course of an allergy (3). AIT induces allergen-specific tolerance by administering increasing doses of causative allergens subcutaneously or sublingually (4). The precise mechanisms underlying AIT remain to be fully elucidated, but the involvement of regulatory T cells and B cells or the induction of T cell anergy is suggested to be a key mechanism for an efficient AIT. AIT induces antigen-specific immunomodulatory cells or the anergic response of T cells specific to major allergens included in an allergen extract as an AIT vaccine. Therefore, the standardization of AIT vaccines using important major allergens and the characterization of major component allergens in an allergen source are important issues for the development of an effective AIT (5, 6).

Imine Deaminase Activity and Conformational Stability of UK114, the Mammalian Member of the Rid Protein Family Active in Amino Acid Metabolism

“…Interest on UK114 has also been recently stimulated by the identification of Der f 34, which is a major allergen of house dust mite ( Dermatophagoides farinae ). This homolog of UK114 is endowed with RidA activity [ 37 ]. Der f 34 and a component of the spores of the fungus Aspergillus fumigatus cross-react with IgE from patients allergic to indoor allergens, suggesting that members of the RidA protein family may represent important pan-allergens that are conserved across different organisms [ 37 ].…”

Members of the Rid protein family have broad imine deaminase activity and can accelerate the Pseudomonas aeruginosa D-arginine dehydrogenase (DauA) reaction in vitro

“…Members of the RidA subfamily from bacteria, plants, archaea, house dust mite, and humans had activity that was indistinguishable from the S . enterica protein when tested in vivo and in vitro [ 7 , 9 , 22 , 24 ]. Significantly, high resolution structures of more than twenty RidA homologs had been determined prior to any biochemical information on their function [ 1 , 15 , 25 – 30 ], many of which exist as Protein Data Bank entries yet to be published.…”

Der f 35: An MD‐2‐like house dust mite allergen that cross‐reacts with Der f 2 and Pso o 2

“…We found that 113 spots possessed IgE‐binding capacity in 40 HDM‐allergic patients and that the IgE‐binding frequency of the spots ranged from 2.5% (1/40) to 85.0% (34/40) (Ref. and unpublished data). Two spots were identified as a major HDM allergen, Der f 2, with 77.5% (31/40) and 65.0% (26/40) IgE‐binding frequency (Figure A,B).…”

“…Two‐dimensional immunoblotting analysis in the allergenome study was carried out using plasma samples from 40 patients allergic to HDM (Ref. and unpublished data). Proteins from D. farinae extract were loaded onto 2D sodium lauryl sulfate (SDS)‐polyacrylamide gel, followed by immunoblotting with HDM‐allergic patients' plasma as described previously .…”