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).
BackgroundEnvironmental control to reduce the amount of allergens in a living place is thought to be important to avoid sensitization to airborne allergens. However, efficacy of environmental control on inactivation of airborne allergens is not fully investigated. We have previously reported that positively- and negatively-charged plasma cluster ions (PC-ions) reduce the IgE-binding capacity of crude allergens from Japanese cedar pollen as important seasonal airborne allergens. Cat (Felis domesticus) and fungus (Aspergillus fumigatus) are also important sources of common airborne allergens in living spaces throughout the year, and early sensitization with those allergens is considered to be a risk factor for future development of allergic rhinitis, pollinosis and asthma. The aim of this study is to examine whether the PC-ions reduce the IgE-binding capacity of a cat major allergen (Fel d 1) and fungal allergens in an experimental condition.MethodsFel d 1, crude fungal extract, or a fungal major allergen Asp f 1, was treated with PC-ions for 6 h in an experimental cylindrical apparatus. Sham-treated allergens were prepared in the same experimental apparatus without generation of PC-ions. The degradation of the PC-ions-treated Fel d 1 was analyzed by SDS-PAGE, and the IgE-binding capacity of the PC-ions-treated allergens was analyzed by ELISA inhibition assay.ResultsExposure of Fel d 1, crude fungal extract and Asp f 1 to PC-ions significantly decreased protein content of Fel d 1 or Asp f 1, respectively. SDS-PAGE analysis suggested that the decreased Fel d 1 content upon exposure with PC-ions was attributable to protein degradation. ELISA inhibition indicated that the PC-ions treatment significantly impaired IgE-binding capacities of Fel d 1, crude fungal allergens, and Asp f 1 compared to sham treatment.DiscussionOur data suggest that treatment with PC-ions not only reduce indoor cat and fungal allergens, but also impair their allergenicity.ConclusionThese results suggest that environmental control with PC-ions is useful for inactivation of indoor cat and fungal allergens.
We previously characterized a 177-kDa allergen, M-177, from Dermatophagoides farinae. Thereafter, a counterpart to M-177 for Euroglyphus maynei was cloned as Eur m 14, and its sequence revealed that two environmental allergens, Mag 1 and Mag 3, are digested fragments of M-177. The aims of this study were to clone the cDNA of Der f 14 corresponding to M-177 and to elucidate the allergenic capacities of the N-terminal fragment of Der f 14 (Der f 14-N). Recombinant allergens were produced as trigger-factor-fused proteins in Escherichia coli. Der f 14-N showed the highest IgE-binding frequency among Der f 14-derived fragments in patients allergic to house dust mite by enzyme-linked immunosorbent assay. Der f 14-N showed the highest capacity to induce cell proliferation in murine lymphocyte and human peripheral mononuclear cells among Der f 14-derived fragments. Der f 14-N induced IL-13, IFN-γ and IL-17 production more than Der f 1 and Der f 2 in mouse, and induced IL-5 and IFN-γ production at levels comparable to those of Der f 1 and Der f 2 in some patients. The high prevalence of IgE binding to the Der f 14-N indicates that it could be an important mite allergen.
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