Clinical characterization and IgE profiling of birch (Betula verrucosa)--allergic individuals suffering from allergic reactions to raw fruits and vegetables.

BACKGROUND: Hypersensitivity to raw fruits and vegetables is often associated with respiratory allergy to birch (Betula verrucosa) pollen and is considered to be the most prevalent form of food allergy in adults sensitized to birch pollen. OBJECTIVE: The aim of the study was to investigate the association of clinical allergy and IgE profiles in individuals with birch pollen allergy and hypersensitivity to raw fruits and vegetables. METHODS: A total of 59 adults with clinical and skin prick test confirmed birch pollen allergy were included in the study. All the subjects were interviewed by using a structured questionnaire and were examined in vivo by the open test, with the appropriate fruits and vegetables. ImmunoCAP and ImmunoCAP ISAC were used as in vitro diagnostics to assess sensitization profiles for each individual, and principal components analysis was used to analyze the IgE data sets. RESULTS: Of 59 individuals, 54 (92%) had positive prick-prick test with raw potato, carrot, apple, and/or hazelnut, and the skin prick test was always positive when the corresponding skin challenge was defined as positive. Specific IgE in the ImmunoCAP and inhibition assays with rMal d 1 and rBet v 1 demonstrated that Bet v 1 is driving the sensitization against pathogenesis related-10 proteins. However, positive IgE in vitro results could not be used to predict clinical reactivity to raw fruits and vegetables. CONCLUSIONS: The present study showed that component-based IgE profiling does not enhance the diagnostic potential in case of pollen-food syndrome, which may be associated with other as yet unidentified components.

In situ imaging of honeybee (Apis mellifera) venom components from aqueous and aluminum hydroxide-adsorbed venom immunotherapy preparations.

BACKGROUND: Treatment with aqueous and aluminum hydroxide (Al[OH](3))-adsorbed purified honeybee (Apis mellifera) venom (HBV) preparations can reduce the incidence of side effects associated with venom immunotherapy. OBJECTIVE: The aim of the present study was to assess these purified HBV immunotherapy preparations in situ. METHODS: Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to visualize the distribution of HBV components. The preparations were administered on the back legs of naive Wistar rats. The rats were killed, and cryosectioned tissue sections were subjected to hematoxylin and eosin staining and MALDI-MSI analyses. RESULTS: Low-density maps of tissue distribution of HBV peptides, such as secapin, mast cell degranulating peptide, and melittin (Api m 4) were detected in the tissue after administration of HBV immunotherapy preparations. In addition, release of biogenic amines, cytokines, and leukotrienes was observed, and the distribution of HBV allergens, such as Api m 1 and Api m 2, was shown. At the 24-hour time point, the major HBV allergen Api m 1 was still detected at the site of Al(OH)(3)-adsorbed HVB injection, whereas in the case of aqueous HBV preparation, all the allergens, as well as most of the biogenic amines, were cleared at the 24-hour time point. CONCLUSION: The present study shows that the majority of low-molecular-weight HBV components are rapidly removed from the site of venom immunotherapy administration. Furthermore, Al(OH)(3)-adsorbed HBV preparation demonstrated a depot effect, prolonging the availability of bee venom allergens at the site of administration.

Absolute quantification of allergens from complex mixtures: a new sensitive tool for standardization of allergen extracts for specific immunotherapy.

Products for specific diagnosis and immunotherapy of IgE-mediated allergies are currently based on natural extracts. Quantification of major allergen content is an important aspect of standardization as important allergens particularly impact vaccine potency. The aim of the study was to develop a mass spectrometry (MS) based assay for absolute quantification of Timothy (Phleum pratense) pollen allergens Phl p 1 and Phl p 5 in P. pratense extract. High-resolution and accurate mass (HRAM) MS was selected for its ability to detect peptides with high selectivity and mass accuracy (<3 ppm). Isotope labeled heavy peptides were used for absolute quantification of specific isoallergens of Phl p 1 and Phl p 5 at low femtomole level in P. pratense extract. Robustness and linearity of the method was demonstrated with intra day precision ≤ 5% (n = 3). Phl p 1b was shown to be 5 times less abundant than its variant Phl p 1a and Phl p 5b was shown to be 9 times more abundant than the Phl p 5a. The present study shows that allergen, and/or isoallergen specific, surrogate signature peptides analyzed with HRAM MS is a sensitive and accurate tool for identification and quantification of allergens from complex allergen sources.

Structural and immunological characterization of the N-glycans from the major yellow jacket allergen Ves v 2: the N-glycan structures are needed for the human antibody recognition.

Yellow jacket (Vespula vulgaris) hyaluronidase (Ves v 2) is a glycoprotein and a mixture of two isoallergens, Ves v 2.01 and Ves v 2.02. Wasp and bee sensitized individuals frequently show IgE antibodies that in vitro recognize common carbohydrate structures across the hymenoptera species. The aim of the study was to characterize the glycosylation patterns in Ves v 2 isoallergens and to assess their immunological properties regarding antibody binding and T cell activation. The glycosylation sites and the carbohydrate structures were verified by use of tandem mass spectrometry (MS/MS). The immunological characterization of the N-glycan structures was assessed by antibody binding, T cell proliferation and T cell epitope assays comparing native (n) and non-glycosylated recombinant (r) Ves v 2. Analyses of the Ves v 2 glycopeptides revealed that glycan attachments were found for residues 79, 99 and 127 of Ves v 2.01, and residues 66 and 81 of Ves v 2.02. Structural analysis of the glycopeptides showed that the majority of the N-glycans contained at least one alpha1,3-fucose and/or alpha1,6-fucose residues in a structure. Interestingly, serum IgE antibodies from vespid allergic patients recognized nVes v 2 but not rVes v 2. Non-glycosylated rVes v 2, however, induced T cell and cytokine responses comparable to glycosylated nVes v 2. The present study shows that N-glycan structures are needed for the antibody recognition but not for the T cell reactivity of Ves v 2 in vitro. The occurrences of carbohydrate-specific antibodies against nVes v 2, however, suggest that non-mammalian glycan structures as in nVes v 2 may provide a link between T cells and other effector cells in allergic responses.

Structure of recombinant Ves v 2 at 2.0 Angstrom resolution: structural analysis of an allergenic hyaluronidase from wasp venom.

Wasp venom from Vespula vulgaris contains three major allergens: Ves v 1, Ves v 2 and Ves v 5. Here, the cloning, expression, biochemical characterization and crystal structure determination of the hyaluronidase Ves v 2 from family 56 of the glycoside hydrolases are reported. The allergen was expressed in Escherichia coli as an insoluble protein and refolded and purified to obtain full enzymatic activity. Three N-glycosylation sites at Asn79, Asn99 and Asn127 were identified in Ves v 2 from a natural source by enzymatic digestions combined with MALDI-TOF mass spectrometry. The crystal structure of recombinant Ves v 2 was determined at 2.0 A resolution and reveals a central (beta/alpha)(7) core that is further stabilized by two disulfide bonds (Cys19-Cys308 and Cys185-Cys197). Based on sequence alignments and structural comparison with the honeybee allergen Api m 2, it is proposed that a conserved cavity near the active site is involved in binding of the substrate. Surface epitopes and putative glycosylation sites have been compared with those of two other major group 2 allergens from Apis mellifera (honeybee) and Dolichovespula maculata (white-faced hornet). The analysis suggests that the harboured allergic IgE-mediated cross-reactivity between Ves v 2 and the allergen from D. maculata is much higher than that between Ves v 2 and the allergen from A. mellifera.

Molecular characterization of major cat allergen Fel d 1: expression of heterodimer by use of a baculovirus expression system.

Fel d 1 is a major cat allergen inducing allergic rhinitis and asthma in sensitized individuals. It has a more complex structure when compared with other allergens and therefore expression of recombinant Fel d 1 has been considered a challenge. The present study shows for the first time that a Baculovirus expression system is able to produce an intact rFel d 1 molecule that is glycosylated and structurally equivalent to the natural cat allergen, nFel d 1. Enzymatic digestion of rFel d 1 and further analysis by use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) resulted in a complete coverage of the amino acid sequence of rFel d 1. In addition, the three disulfide bridges at the positions alpha70-beta7, alpha44-beta48, and alpha3-beta73 were verified. The N-glycan structure of rFel d 1 was investigated by a combination of MALDI-TOF MS and monosaccharide analysis by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAC). The N-glycosylation analyses of rFel d 1 refer to a pattern of glycoforms including core alpha1.3-fucosylation that is different from nFel d 1. Further characterization by use of human serum IgE, histamine release, and lymphocyte proliferation assays demonstrated that the immunological characteristics of rFel d 1 are similar to those of nFel d 1. Detailed characterization of both natural and recombinant allergens provides tools to explore immunological mechanisms associated with allergen sensitization and desensitization.

Activation of human neonatal monocyte-derived dendritic cells by lipopolysaccharide down-regulates birch allergen-induced Th2 differentiation.

Epidemiological studies describe an inverse association between the level of environmental endotoxin exposure during infancy and the prevalence of allergic disease in children. To study the effect of lipopolysaccharide (LPS) and lipopeptide Pam3Cys signaling via Toll-like receptor (TLR)4 and TLR2 on dendritic cells (DC), respectively, on birch allergen-induced T cell differentiation, cord blood monocyte-derived DC were exposed to birch allergen extract alone or in combination with LPS or Pam3Cys and thereafter co-cultured with naive autologous T cells. We demonstrate that birch allergen alone induced high levels of IL-13 from neonatal T cells, whereas the production of IL-5 and IFN-gamma was modest. Stimulation of DC with birch allergen together with LPS but not Pam3Cys resulted in a decreased IL-13 production by T cells compared to birch allergen alone. Furthermore, birch allergen together with LPS induced increased up-regulation of activation markers expressed on the surface and production of cytokines from DC relative to stimulation with birch allergen alone. Finally, birch allergen partially suppressed both LPS- and Pam3Cys-induced DC maturation. Our results indicate that concomitant TLR4 stimulation during the initial phase of immune activation to birch allergen in infants may inhibit the development of a T helper 2-type response.

Allergen-specific immunosuppression by mucosal treatment with recombinant Ves v 5, a major allergen of Vespula vulgaris venom, in a murine model of wasp venom allergy.

Up to 5% of the population suffer from systemic, 19% from local allergic hypersensitivity reactions to stinging insects. Even though specific immunotherapy is very effective in treating allergy to insect venom, new concepts of treatment strategies with only the disease eliciting allergen in recombinant form, along with antigen application via a less invasive route might be suggested for enhanced treatment efficacy and compliance. In the present study we aimed (i) to establish a mouse model of wasp venom allergy, mimicking the natural mode of sensitization, and (ii) to develop a prophylactic treatment strategy based on mucosal tolerance induction, using one major wasp venom allergen in recombinant form, i.e. recombinant (r)Ves v 5. Immunization with wasp venom--with or without the use of the adjuvant aluminium hydroxide--led to comparable T helper 2-like immune responses in vivo and in vitro. Intranasal administration of rVes v 5 prior to sensitization with wasp venom resulted in a significant reduction of wasp venom-specific antibody levels (immunoglobulin E (IgE)/IgG2a), type I hypersensitivity reactions in vivo and cytokine production in vitro. Pretreatment with the whole venom was less effective and caused toxic side reactions in higher concentrations, suggesting a favourable use of the recombinant venom allergen for mucosal application. Increased mRNA levels of transforming growth factor-beta and interleukin-10, along with adoptive cell transfer experiments indicated that the immunosuppression after intranasal rVes v 5-application has been mediated by regulatory mechanisms. This is further supported by the fact that the immunosuppression to rVes v 5 was associated with a bystander suppression to the unrelated aero-allergen Bet v 1. In conclusion, we demonstrated that the intranasal application of recombinant Ves v 5 prevented subsequent allergic sensitization to all components of the whole wasp venom. As allergy to insect venom develops in dependence of the frequency of insect stings, a prophylactic treatment based on mucosal tolerance induction with recombinant allergens might be of interest for people at high risk to frequent exposure to the stinging insects.