Formation of disulfide bonds and homodimers of the major cat allergen Fel d 1 equivalent to the natural allergen by expression in Escherichia coli

Dander from the domestic cat (Felis domesticus) is one of the most common causes of IgE-mediated allergy. Attempts to produce tetrameric folded major allergen Fel d 1 by recombinant methods with structural features similar to the natural allergen have been only partially successful. In this study, a recombinant folded Fel d 1 with molecular and biological properties similar to the natural counterpart was produced. A synthetic gene coding for direct fusion of the Fel d 1 chain 2 N-terminally to chain 1 was constructed by overlapping oligonucleotides in PCR. Escherichia coli expression resulted in a non-covalently associated homodimer with an apparent molecular mass of 30 kDa defined by size exclusion chromatography. Furthermore, each 19,177-Da subunit displayed a disulfide pattern identical to that found in the natural Fel d 1, i.e. Cys3(1) Cys73(2), Cys44(1)-Cys48(2), Cys70(1)-Cys7(2), as determined by electrospray mass spectrometry after tryptic digestion. Circular dichroism analysis showed identical folds of natural and recombinant Fel d 1. Furthermore, recombinant Fel d l reacted specifically with serum IgE, inducing expression of CD203c on basophils and lymphoproliferative responses in cat-allergic patients. The results show that the overall fold and immunological properties of the recombinant Fel d 1 are very similar to those of natural Fel d 1. Moreover, the recombinant Fel d 1 construct provides a tool for defining the three-dimensional structure of Fel d 1 and represents a reagent for diagnosis and allergen-specific immunotherapy of cat allergy.     

The crystal structure of the major cat allergen Fel d 1, a member of the secretoglobin family

The domestic cat (Felis domesticus) is one of the most important causes of allergic asthma worldwide. The dominating cat allergen, Fel d 1, is composed of two heterodimers. Recently, it has been shown that recombinant Fel d 1, consisting of chain 2 and chain 1 fused together without additional linker, has immunological properties indistinguishable from the natural heterodimeric protein. Herein, we report the crystal structure of recombinant monomeric Fel d 1 at 1.85-A resolution, determined by multi-wavelength anomalous diffraction using selenomethionine substituted protein. Fel d 1 is an all-helical protein and consists of eight helices. The two halves of the recombinant Fel d 1 molecule, corresponding to the wild-type Fel d 1 chains, are very similar in three-dimensional structure, despite the lack of significant sequence identity. The structure of the Fel d 1 presents a striking similarity to that of uteroglobin, a steroid-inducible cytokine-like molecule with anti-inflammatory and immunomodulatory properties. An internal, asymmetric cavity is formed in the Fel d 1 that could bind an endogenous ligand. The distribution of residues lining this cavity suggests that such a ligand must be amphipathic. The structure of Fel d 1 displays the localization of three previously defined Fel d 1 IgE epitopes on the surface of the protein. The three-dimensional structure provides a framework for rational design of hypoallergenic mutants aimed for treatment of cat allergy.     

Cat (Fel d 1) and dog (Can f 1) allergen levels in cars,dwellings and schools

Pets are an important source of indoor allergens. The aim of the study was to compare cat and dog allergen levels in cars, schools and homes. The study was carried out in 17 cars, 14 classrooms and 19 dwellings located in the highly industrialized and urbanized region of Poland. Dust and air samples were analyzed for Fel d 1 and Can f 1 using a double monoclonal ELISA assay. The highest amounts of cat and dog allergens (Fel d 1: 1169 μg/g; Can f 1: 277 μg/g) were found in dwellings with pets. Allergen concentrations were correlated with the number of animals kept at home. Although concentrations on automobile seats were lower, Fel d 1 levels exceeded 8 μg/g in 23.5 % of cars and high levels of Can f 1 (>10 μg/g) were found in 17.6 % of cars. The study revealed that cars of pet owners may be reservoirs of cat and dog allergens even when animals are not transported in them. In schools, concentrations of pet allergens did not reach high levels, but the moderate levels of Fel d 1 (≥1–8 μg/g) and Can f 1 (≥2–10 μg/g) were detected in 42.9 and 7.1 % of the investigated classrooms. Concentrations of cat and dog allergen in schools were higher than in homes without pets. While airborne Fel d 1 and Can f 1 levels were found low, residential allergen concentrations in settled dust and air were correlated. The study results suggest that classrooms and cars of pet owners may be important sites of exposure to cat and dog allergens, though the highest concentrations of Fel d 1 and Can f 1 are found in homes of pet owners.     

Recognition of the major cat allergen Fel d 1 through the cysteine-rich domain of the mannose receptor determines its allergenicity

Dendritic cells are professional antigen-presenting cells that are specialized in antigen uptake and presentation. Allergy to cat has increased substantially in recent years and has been shown to be positively associated with asthma. We have recently shown that the mannose receptor (MR), a C-type lectin expressed by dendritic cells, recognizes various glycoallergens from diverse sources and is involved in promoting allergic responses to a major house dust mite allergen in vitro. Here we investigated the potential role of MR in allergic responses to Fel d 1, a major cat allergen. Fel d 1 binding to MR was confirmed by ELISA. Using blocking, gene silencing (siRNA) experiments, and MR knock-out (MR(-/-)) cells, we have demonstrated that MR plays a major role in internalization of Fel d 1 by human and mouse antigen-presenting cells. Intriguingly, unlike other glycoallergens, recognition of Fel d 1 by MR is mediated by the cysteine-rich domain, which correlates with the presence of sulfated carbohydrates in natural Fel d 1. WT and MR(-/-) mice were used to study the role of MR in allergic sensitization to Fel d 1 in vivo. MR(-/-) mice sensitized with cat dander extract and Fel d 1 produced significantly lower levels of total IgE, Fel d 1-specific-IgE and IgG1, the hallmarks of allergic response, compared with WT mice. Our data show for the first time that Fel d 1 is a novel ligand of the cysteine-rich domain of MR and that MR is likely to play a pivotal role in allergic sensitization to airborne allergens in vivo.     

Direct on air sampling filter quantification of cat allergen

A direct on sampling filter in solution (DOSIS) method for quantification of airborne cat allergens has been developed. In this method, the allergens firmly adsorbed to a porous polytetrafluoroethylene filter are reacted with specific antibodies conjugated to alkaline phosphatase, generating a matrix-bound allergen-antibody-phosphatase complex. The treated filter is subsequently floated on a commercially available chemiluminescent phosphatase substrate solution. Aliquots of this solution are removed and analyzed luminometrically. The light intensity of the product is linearly related to the amount of allergen over a large mass range, 0-100 SQ units (1 SQ unit is about 146 pg of the allergenic protein Fel d 1). DOSIS demonstrated intra- and interassay precisions of 9% and 8% and 14% and 21% for the levels 4 and 20 SQ units per filter, respectively. The limit of quantification was estimated to 0.4 SQ units (58 pg Fel d 1) of cat allergen per filter. Application of DOSIS to analysis of cat allergen concentrations of indoor air in homes with and without cats revealed, on average, a six times higher concentration in the former (142 SQ units/m(3)) as compared to the latter (24 SQ units/m(3)). The recorded concentrations for airborne cat allergen in homes with cats are in accordance with previously reported figures. Allergen-specifically stained sampling filters revealed the particulate nature of airborne cat allergen which seemed predominantly to be carried by numerous large dust particles.     

Molecular characterization and allergenic activity of Lyc e 2 (beta-fructofuranosidase), a glycosylated allergen of tomato.

Until now, only a small amount of information is available about tomato allergens. In the present study, a glycosylated allergen of tomato (Lycopersicon esculentum), Lyc e 2, was purified from tomato extract by a two-step FPLC method. The cDNA of two different isoforms of the protein, Lyc e 2.01 and Lyc e 2.02, was cloned into the bacterial expression vector pET100D. The recombinant proteins were purified by electroelution and refolded. The IgE reactivity of both the recombinant and the natural proteins was investigated with sera of patients with adverse reactions to tomato. IgE-binding to natural Lyc e 2 was completely inhibited by the pineapple stem bromelain glycopeptide MUXF (Man alpha 1-6(Xyl beta 1-2)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-3)GlcNAc). Accordingly, the nonglycosylated recombinant protein isoforms did not bind IgE of tomato allergic patients. Hence, we concluded that the IgE reactivity of the natural protein mainly depends on the glycan structure. The amino acid sequences of both isoforms of the allergen contain four possible N-glycosylation sites. By application of MALDI-TOF mass spectrometry the predominant glycan structure of the natural allergen was identified as MMXF (Man alpha 1-6(Man alpha 1-3)(Xyl beta 1-2)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-3) GlcNAc). Natural Lyc e 2, but not the recombinant protein was able to trigger histamine release from passively sensitized basophils of patients with IgE to carbohydrate determinants, demonstrating that glycan structures can be important for the biological activity of allergens.     

Structural characterization of the tetrameric form of the major cat allergen Fel d 1

Felis domesticus allergen 1(Fel d 1) is a 35 kDa tetrameric glycoprotein formed by two heterodimers which elicits IgE responses in 95% of patients with allergy to cat. We have previously established in vitro conditions for the appropriate folding of recombinant Fel d 1 using a direct linkage of chain 1 to chain 2 (construct Fel d 1 (1+2)) and chain 2 to chain 1 (construct Fel d 1 (2+1)). Although the crystal structure of Fel d 1 (2+1) revealed a striking structural similarity to that of uteroglobin, a steroid-inducible cytokine-like molecule with anti-inflammatory and immunomodulatory properties, no functional tetrameric form of Fel d 1 could be identified. Here we present the crystal structure of the Fel d 1 (1+2) tetramer at 1.6 A resolution. Interestingly, the crystal structure of tetrameric Fel d 1 reveals two different calcium-binding sites. Symmetrically positioned on each side of the Fel d 1 tetramer, the external Ca(2+)-binding sites correspond to a putative Ca(2+)-binding site previously suggested for uteroglobin. The second Ca(2+)-binding site lies within the dimerization interface, stabilizing the formation of the Fel d 1 tetramer, and inducing important local conformational changes that directly govern the shape of two water-filled cavities. The crystal structure suggests a potential portal for an unknown ligand. Alternatively, the two cavities could be used by the allergen as a conditional inner space allowing for the spatial rearrangement of centrally localized side-chains, such as Asp130, without altering the overall fold of the molecule. The striking structural similarity of the major cat allergen to uteroglobin, coupled to the identification in the present study of a common Ca(2+)-binding site, let us speculate that Fel d 1 could provoke an allergic response through the modulation of phospholipase A2, by sequestering Ca ions in a similar manner as previously suggested for uteroglobin.     

A chimeric human-cat fusion protein blocks cat-induced allergy

Animal allergens are an important cause of asthma and allergic rhinitis. We designed and tested a chimeric human-cat fusion protein composed of a truncated human IgG Fcgamma1 and the major cat allergen Fel d1, as a proof of concept for a new approach to allergy immunotherapy. This Fcgamma-Fel d1 protein induced dose-dependent inhibition of Fel d1-driven IgE-mediated histamine release from cat-allergic donors' basophils and sensitized human cord blood-derived mast cells. Such inhibition was associated with altered Syk and ERK signaling. The Fcgamma-Fel d1 protein also blocked in vivo reactivity in FcepsilonRIalpha transgenic mice passively sensitized with human IgE antibody to cat and in Balb/c mice actively sensitized against Fel d1. The Fcgamma-Fel d1 protein alone did not induce mediator release. Chimeric human Fcgamma-allergen fusion proteins may provide a new therapeutic platform for the immune-based therapy of allergic disease.     

Heat Shock Protein-derived peptides as a potential immuno-regulatory vaccine in allergy. "In silico" analysis

Background: Allergic and autoimmune diseases are forms of altered immune responses directed respectively against exogenous and endogenous antigens. A growing body of experimental evidence exists to support a com-mon pathogenetic link between allergy and autoimmunity. Identification of shared antigens might thus be usefully exploited in the therapy of both conditions. The allergy to cat allergens is very common and fre-quently associated with asthma. Sequences of the main cat allergen Fel d1, containing overlapping T cell epitopes that bind to HLA molecules, have been used as an effective allergen-specific peptide vaccine. It has been observed that human proteins identified as cross-reactive auto-antigens with structural homology with environmental allergens often belong to evolutionarily conserved proteins.Heat shock proteins (HSPs) are among the most conserved proteins and some of them have been recog-nized as antigens in autoimmune diseases and also as the main proteins of environmental allergens. We performed an extensive “in silico” analysis to test the hypothesis that the human HSPs Grp94, Grp78, HSP90, HSP71 and HSP60 could show similarity with both Fel d1 and other common allergens, thus serv-ing as a source of peptides in a broad-spectrum allergen-specific immuno-therapy.Results: An extensive structural similarity was observed between Fel d1 and sequences of HSP71, Grp78, HSP90 and Grp94. These HSP sequences contained T-cell epitopes with binding capacity to HLA alleles better than that displayed by corresponding similar Fel d1-derived peptides employed so far as therapeutic vac-cines. A significant similarity was also found between these HSP sequences and other aeroallergens, not shared by Fel d1-derived peptides. HLA alleles involved in binding HSP sequences were mostly those as-sociated with an increased predisposition to both allergy and autoimmune diseases.Conclusion: Results support the possibility that HSP-derived immuno-dominant epitopes are exploitable as therapeutic peptides in allergies other than cat allergy.     

Monoclonal antibodies to the major feline allergen Fel d I. II. Single step affinity purification of Fel d I, N-terminal sequence analysis, and development of a sensitive two-site immunoassay to assess Fel d I exposure

Two mAb were used to develop new techniques for the purification and quantitation of the major feline salivary allergen, Felis domesticus allergen I (Fel d I). The allergen was purified from aqueous house dust extract with a high Fel d I content by affinity chromatography over a monoclonal immunosorbent and elution with 4 mM HCl, pH 2.5. This single step procedure gave 40 to 50% recovery of 90% pure allergen which, following final purification by size exclusion HPLC, showed a single line on immunodiffusion and crossed immunoelectrophoresis against monospecific anti-Fel d I and polyclonal anti-cat dander antibodies. The m.w. of native Fel d I was 39,000 on size exclusion HPLC, and 17,000 under nonreducing conditions on gel electrophoresis. The N-terminal amino acid sequence (33 residues) showed no homology with other known protein sequences. The combination of the SDS-PAGE and N-terminal sequence data suggests that Fel d I is a non-covalently linked homodimer. A two-site RIA was developed using mAb directed against different epitopes on Fel d I. This assay was species-specific, highly sensitive (0.0004 U/ml), and showed an excellent correlation with a polyclonal inhibition RIA (n = 27, r = 0.93, p less than 0.001). Cat allergen extracts used for immediate skin tests showed marked differences in Fel d I content (from 0.1 to 30 U/ml). Consistently high Fel d I levels were found at monthly intervals in six dust samples from four houses with cats (10 to 100 U/g of dust). Comparisons of Fel d I and mite and pollen allergen levels showed that house dust can contain greater than 100 micrograms/g of either of these allergens and is a potent source of foreign environmental antigens. Monoclonal affinity chromatography provides a major breakthrough in the purification of Fel d I, from a source material that would otherwise have been considered impossible (house dust). The mAb assay for Fel d I is both more sensitive and more easily standardized than existing techniques. These techniques will allow full structural and antigenic analysis of Fel d I and more detailed studies on the relationship between cat antigen exposure and the development of asthma.     

Mouse Model of Cat Allergic Rhinitis and Intranasal Liposome-Adjuvanted Refined Fel d 1 Vaccine

Cats (Felis domesticus) are rich source of airborne allergens that prevailed in the environment and sensitized a number of people to allergy. In this study, a mouse model of allergic rhinitis caused by the cat allergens was developed for the first time and the model was used for testing therapeutic efficacy of a novel intranasal liposome-entrapped vaccines made of native Fel d 1 (major cat allergen) in comparison with the vaccine made of crude cat hair extract (cCE). BALB/c mice were sensitized with cCE mixed with alum intraperitoneally and intranasally. The allergic mice were treated with eight doses of either liposome (L)-entrapped native Fel d 1 (L-nFD1), L-cCE), or placebo on every alternate day. Vaccine efficacy evaluation was performed one day after provoking the treated mice with aerosolic cCE. All allergenized mice developed histological features of allergic rhinitis with rises of serum specific-IgE and Th2 cytokine gene expression. Serum IgE and intranasal mucus production of allergic mice reduced significantly after vaccination in comparison with the placebo mice. The vaccines also caused a shift of the Th2 response (reduction of Th2 cytokine expressions) towards the non-pathogenic responses: Th1 (down-regulation of the Th1 suppressive cytokine gene, IL-35) and Treg (up-regulation of IL-10 and TGF-β). In conclusions, a mouse model of allergic rhinitis to cat allergens was successfully developed. The intranasal, liposome-adjuvanted vaccines, especially the refined single allergen formulation, assuaged the allergic manifestations in the modeled mice. The prototype vaccine is worthwhile testing further for clinical use in the pet allergic patients.     

The glycosylation pattern of common allergens: the recognition and uptake of Der p 1 by epithelial and dendritic cells is carbohydrate dependent

Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1-2, 1-3 and 1-6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production.     

Crystal Structure of the Dog Lipocalin Allergen Can f 2: Implications for Cross-reactivity to the Cat Allergen Fel d 4

The dog lipocalin allergen Can f 2 is an important cause of allergic sensitization in humans worldwide. Here, the first crystal structure of recombinant rCan f 2 at 1.45 Å resolution displays a classical lipocalin fold with a conserved Gly-Xaa-Trp motif, in which Trp19 stabilizes the overall topology of the monomeric rCan f 2. Phe38 and Tyr84 localized on the L1 and L5 loops, respectively, control access to the highly hydrophobic calyx. Although the rCan f 2 calyx is nearly identical with the aero-allergens MUP1, Equ c 1 and A2U from mouse, horse and rat, respectively, no IgE cross-reactivity was found using sera from five mono-sensitized subjects. However, clear IgE cross-reactivity was demonstrated between Can f 2 and the cat allergen Fel d 4, although they share less than 22% sequence identity. This suggests a role for these allergens in co-sensitization between cat- and dog-allergic patients.     

Rapid production of the major birch pollen allergen Bet v 1 in Nicotiana benthamiana plants and its immunological in vitro and in vivo characterization.

Type I allergies are immunological disorders that afflict a quarter of the world's population. Improved diagnosis of allergic diseases and the formulation of new therapeutic approaches are based on the use of recombinant allergens. We describe here for the first time the application of a rapid plant-based expression system for a plant-derived allergen and its immunological characterization. We expressed our model allergen Bet v 1, the major birch pollen allergen, in the tobacco-related species Nicotiana benthamiana using a tobacco mosaic virus vector. Two weeks postinoculation, plants infected with recombinant viral RNA containing the Bet v 1 coding sequence accumulated the allergen to levels of 200 microg/g leaf material. Total nonpurified protein extracts from plants were used for immunological characterizations. IgE immunoblots and ELISA (enzyme-linked immunoassay) inhibition assays showed comparable IgE binding properties for tobacco recombinant (r) Bet v 1 and natural (n) Bet v 1, suggesting that the B cell epitopes were preserved when the allergen was expressed in N. benthamiana plants. Using a murine model of type I allergy, mice immunized with crude leaf extracts containing Bet v 1 with purified rBet v 1 produced in E. coli or with birch pollen extract generated comparable allergen-specific IgE and IgG1 antibody responses and positive type I skin test reactions. These results demonstrate that nonpurified Bet v 1 overexpressed in N. benthamina has the same immunogenicity as purified Bet v 1 produced in E. coli or nBet v 1. We therefore conclude that this plant expression system offers a viable alternative to fermentation-based production of allergens in bacteria or yeasts. In addition, there may be a broad utility of this system for the development of new and low-cost vaccination strategies against allergy.     

Sampling dust from human dwellings to estimate the prevalence ofDermatophagoides mite and cat allergens

Summary Quantification of specific allergens in household dust samples may provide important information for selecting appropriate allergen control methods, and monitoring efficacy and compliance. The purpose of this study was to investigate the source of variation in mite and cat allergen measurements associated with dust sample collection. Discrete and composite dust samples were collected on a filter using a special vacuum sampling device. Aqueous extracts of the dust samples were prepared thenDer p I,Der f I, andFel d I were quantitated by enzyme immunoassays (EIA). Mite and cat allergens were frequently detected in dust samples from human dwellings, and the amounts of these allergens varied significantly (p<0.01) among dwellings. The differences of allergen measurements among duplicate samples taken immediately and up to three weeks later appear to be much smaller than differences among houses and between rooms. Variation among dust samples taken from living rooms and bedrooms of the same dwelling suggest differences in allergen reservoirs. Composite samples formed by sampling specific objects within a room may provide a reliable estimate of allergen exposure in that room. Dust samples from discrete objects are useful to find and monitor specific reservoirs of mite and cat allergens.     

Sub-proteome analysis of novel IgE-binding proteins from Bermuda grass pollen

Bermuda grass (Cynodon dactylon) pollen (BGP) is one of the most common causes of airway allergic disease, and has been shown to contain over 12 allergenic proteins on 1-D immunoglobulin E (IgE) immunoblots. However, only a few allergens have been identified and characterized. Cyn d 1 is a major allergen and the most abundant protein in BGP, representing 15% of the whole-pollen extract. To investigate variability in the IgE-reactive patterns of BGP-sensitized patients and to identify other prevalent allergens, a BGP extract was passed through an affinity column to remove Cyn d 1, and the non-bound material was collected and analyzed by 2-DE. IgE-reactive proteins were subsequently characterized by immunoblotting using serum samples from ten BGP-allergic patients. The prevalent IgE-reactive proteins were identified by MALDI-TOF MS, N-terminal sequence similarity, and LC-MS/MS. Here, we present a sub-proteome approach for allergen investigation and its use for determining BGP 2-DE profiles and identifying six novel allergens.     

Antigen-specific T cell tolerance down-regulates mast cell responses in vivo

Fel d I is the major cat allergen that induces asthma and allergic rhinitis in humans. To investigate the mechanism of allergic responses to this allergen, a mouse model was developed. Mice sensitized to chain 1 of Fel d I exhibited T cell responses, B cell responses, and mast cell responses when challenged with the protein. Subcutaneous injections of peptides containing the dominant T cell epitopes of the allergen induced T cell tolerance in presensitized mice. When challenged with the allergen intratracheally, these tolerized mice produced a decreased amount of histamine in vivo. The decrease in histamine release was not solely dependent on the reduction of allergen-specific IgE. These data show that mast cell activity in mice with an ongoing sensitivity to allergen can be regulated through peptide-induced T cell tolerance.     

The mouse salivary androgen-binding protein (ABP) alpha subunit closely resembles chain 1 of the cat allergen Fel dI

Androgen-binding protein (ABP) is found in the salivas of a wide variety of rodents and it has been proposed that ABP functions in sex and/or subspecies recognition (Karn and Dlouhy,J. Hered. 82, 453, 1991). This is a report of significant identity between the alpha subunit of mouse salivary ABP and Chain 1 of cat allergen Fel dI (50% identity), as well as with two other proteins that share identity with Chain 1 of Fel dI, rabbit uteroglobin (27% identity with ABP alpha) and human lung Clara 10 (27% identity with ABP alpha). The secondary structure predicted for the mouse ABP alpha subunit is a very good fit with the secondary structure determined by X-ray crystallography for rabbit uteroglobin, a protein that shares with mouse ABP the capability of binding steroid. Fel dI is found in cat saliva, sebaceous glands, and pelt. Its function is not known but it has been proposed to be involved in protecting dry epithelia, a parallel to uteroglobin protecting wet epithelia. Since mice, like cats, lick themselves and each other extensively, coating their pelts with ABP may be part of this or another biological function.     

SU-8 based microprobes with integrated planar electrodes for enhanced neural depth recording

A gold nanoparticle, localised plasmon array biosensor using light scattering has been employed in the detection of allergen-specific antibodies in whole blood and sera. The array sensor was functionalized with four different allergens, cat dander (Fel d1), dust mite (Der p1), peanut allergen (Ara h1) and dog dander (Can f1) and immuno-kinetic assay was performed to detect their respective anti-allergen IgG antibodies. Specific positive responses to antibodies at a concentration of 25 nM were observed for Fel d1, Der p1, and Ara h1 allergens, while the Can f1 channel served as a reference control. The sensitivity was further enhanced using a secondary anti-IgG detection antibodies to give a limit of detection of 2 nM. The results indicate the potential for nanoparticle scattering multiplexed arrays to screen unprepared blood samples at point-of-care for assays of complex samples such as the whole blood.     

Microarrayed allergens for IgE profiling

Diagnosis of type I allergy is based on anamnesis, provocation testing, and serological determination of total and specific IgE. Currently, in vivo and in vitro diagnostic tests employ allergen extracts prepared from various allergen sources (e.g., pollen, mites, animal dander, moulds, foods, venoms, etc.). The application of recombinant DNA technology to the field of allergen characterization has allowed to reveal the molecular nature of the most common allergens. To date a continuously increasing number of allergen sequences has become available and panels of recombinant allergens-assembling the epitope complexity of natural allergens sources-can be produced. The use of recombinant allergens instead of crude, natural extracts for allergy diagnosis allows us to determine the individual IgE reactivity profile of each patient. To enable a comprehensive analysis of the patient's IgE binding pattern to a large number of individual allergens, a new type of serological test is required. In this paper, we applied microarray technology to create a multi-allergen test system, based on microarrayed recombinant allergens.