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R Valenta

Publications and source records attributed to R Valenta.

195 records · Page 11Linked to original sources
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Mucosal tolerance induction with hypoallergenic molecules in a murine model of allergic asthma.

Type I allergy, frequently elicited by airborne allergens, has constantly increased within recent years. Birch pollen and its major allergen Bet v 1 represent a major source of type I allergens. By genetic engineering hypoallergenic Bet v 1 fragments were produced, which lost the IgE binding capacity but retained the T cell epitopes. We have established a murine model of aerosol sensitization to birch pollen and its major allergen Bet v 1, leading to type I allergic immune responses and airway hyperresponsiveness. In the present study we demonstrate that mucosal administration of recombinant Bet v 1 prior to sensitization led to allergen-specific suppression of B and T cell responses in vivo and in vitro, reduction of eosinophilic infiltration in the lungs and inhibition of airway hyperresponsiveness. Intranasal pretreatment with the nonanaphylactic fragments of Bet v 1 prevented allergic immune responses and airway inflammation to the same degree as the pretreatment with the complete molecule. We conclude from our studies that mucosal tolerance induction with hypoallergenic molecules could provide a safe and convenient treatment strategy against type I allergies.

Allergens↗
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The influence of CpG motifs on a protein or DNA-based Th2-type immune response against major pollen allergens Bet v 1a, Phl p 2 and Escherichia coli-derived beta-galactosidase.

BACKGROUND: DNA immunization and protein immunization with CpG motifs as adjuvants represent promising approaches in allergen-specific immunotherapy. OBJECTIVE: We investigated the effect of coinjection or prepriming with CpG-ODN on Th2-type responses induced by gene gun and protein immunization. METHODS: BALB/c mice were immunized with the gene gun using plasmid DNA containing the cDNAs coding for the genes of Bet v 1a, Phl p 2 and beta-galactosidase or with the purified Al(OH)(3)-adsorbed proteins. In addition, CpG-ODN were applied by coinjection or by prepriming treatment. Antibody and cytokine responses were measured by ELISA, proliferative and cytotoxic responses were determined by standard labeling procedures. Furthermore, the allergenic activity of sera was measured by passive cutaneous anaphylaxis. RESULTS: Gene gun immunization and protein immunization induced a clear Th2-type response for all antigens. The Th1-promoting effect of CpG-ODN coinjection together with gene gun immunization was restricted to beta-galactosidase as indicated by the increase of IgG2a and a marked expression of IFN-gamma. CpG motifs also increased the specific cytotoxic response against beta-galactosidase. Prepriming with CpG-ODN and gene gun or protein immunization with Bet v 1a exhibited no significant difference to the non-CpG control group. However, sera from mice preprimed with CpG-ODN induced no anaphylaxis with gene gun immunization, but with protein immunization. CONCLUSIONS: The effect of CpG motifs in vivo depends on a variety of parameters like the nature of the antigen and the immunization modality. Furthermore, our studies indicate that a combination of CpG + DNA immunization may be more effective in antagonizing Th2 responses than the combination of CpG + protein immunization.

Adjuvants, Immunologic↗
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Humoral immune responses to recombinant tree pollen allergens (Bet v I and Bet v II) in mice: construction of a live oral allergy vaccine.

Recombinant tree pollen allergens (recombinant Bet v I and recombinant birch profilin, Bet v II) were purified and used to immunize BALB/c and B6D2F1 mice with Al(OH)3 to elicit a specific IgE response. Serum from immunized mice was then used to detect immunoblotted natural tree pollen allergens. The onset of the humoral immune response was monitored using antimouse IgE, IgG1, IgG2a/b, IgG3 and IgA. In both strains, a specific and long-lasting IgE response could be elicited with both recombinant allergens. Mice immunized continuously with recombinant Bet v I + Al(OH)3 showed a significant decrease of specific IgE antibodies indicating that continuous application of allergens can reduce specific IgE responses. The possibility of inducing a different type of immune responses is indicated by the fact that mice fed with Bet v I expressed in apathogenic Salmonella strains showed a Th1 immune response to Bet v I accompanied by specific IgG2a/b without detectable IgG1 or IgE. Recombinant allergens can hence be used to decrease or even modulate specific IgE responses in vivo.

Adjuvants, Immunologic↗
PubMedDate not supplied

X-ray crystal structures of birch pollen profilin and Phl p 2.

BACKGROUND: Type 1 allergy affects 20% of industrialized populations and thus represents a major health care issue. The symptoms of type 1 allergy, which include rhinitis, conjunctivitis, dermatitis and asthma, are elicited by the cross-linking of IgE receptors through polyvalent allergens. A detailed understanding of the cell surface phenomena and the rational development of new therapies require high-resolution structural information. METHODS: The structures of two widespread allergens, birch pollen profilin (BPP) and Phl p 2 have been solved by multiple isomorphous replacement. Refinements are underway to 2.4 and 2.0 A, respectively. In addition, the IgE-reactive epitopes of BPP where identified by screening an epitope expression library with the serum IgE of an allergic individual. RESULTS: BPP exhibits an alpha/beta-fold which is similar to the mammalian and amoeba profilins. The structure of Phl p 2 is a compact eight-stranded beta-barrel. Screening an epitope library of BPP identified three major epitopic regions involved in IgE binding, including the amino and carboxy-terminal alpha-helices. These regions also interact with the physiologically relevant ligands of profilin, actin and proline-rich peptides. CONCLUSIONS: The distribution of IgE-binding sites on BPP allows for the productive interaction with IgE antibodies of different epitope specificities required for efficient signal transduction. These epitopes correspond to the most highly conserved regions of the profilin molecule and thus provide the molecular basis for allergen cross-sensitivity. Due to steric considerations, the involvement of these epitopic regions in the binding of physiologically relevant profilin ligands indicates that the native profilin is the species responsible for eliciting the allergic response. A comparison of the BPP and Phl p 2 structures shows that there is no preference for secondary structural elements in the allergic response. The detailed chemical and physical description of the major reactive epitopes provides a data base for the design of tight-binding monovalent ligands which can prevent receptor aggregation and thereby reduce the allergic response.

Allergens↗
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Division of the major birch pollen allergen, Bet v 1, into two non-anaphylactic fragments.

We have expressed in Escherichia coli two halves of the major birch pollen allergen, Bet v 1. Both fragments representing the complete 17-kD allergen were purified to homogeneity. In contrast to the complete recombinant, Bet v 1, the fragments had almost completely lost their IgE-binding capacity and exhibited a random coil structure as analyzed by circular dichroism. The ability of the recombinant fragments to trigger histamine release from allergic patients' basophils as well as their capacity to elicit skin reactions were also largely abolished. Both non-anaphylactic Bet v 1 fragments carried the majority of T cell epitopes and may therefore be considered as safe tools for immunotherapy of tree pollen and associated food allergy.

Allergens↗
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Different profiles in specific IgE to rBet v 1 and rBet v 2 in patients allergic to birch pollen from six countries.

There are differences in IgE reactivity to rBet v 1 and rBet v 2 among allergic patients from the six countries studied. The complexity of the reactivity profile tends to be greater in individuals from the central/southern parts of Europe compared to Sweden and Finland. There is a good agreement between in vitro diagnosis with Pharmacia CAP System and Skin prick testing when using the same reagents, rBet v 1 and rBet v 2.

Allergens↗
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Genetically engineered and synthetic allergen derivatives: candidates for vaccination against type I allergy.

Type I allergy, a hypersensitivity disease affecting almost 20% of the population worldwide, is based on the IgE recognition of otherwise harmless antigens (i.e., allergens). Allergen-induced crosslink of effector cell-bound IgE antibodies leads to the release of biological mediators and thus to immediate disease symptoms (allergic rhinitis, conjunctivitis and asthma). Specific immunotherapy, the only causative treatment of Type I allergy, is based on the administration of increasing doses of allergens to allergic patients in order to yield allergen-specific non-responsiveness. Major disadvantages are 1. that current forms of allergen immunotherapy are performed with allergens difficult to standardize which cannot be matched to the patients reactivity profile and 2. that the administration of active allergen preparations can cause anaphylactic side effects. Through the application of molecular biological techniques many relevant environmental allergens have been produced as active recombinant proteins which allow component-resolved allergy diagnosis and thus represent the basis for patient-tailored forms of immunotherapy. Here we review molecular strategies which have been recently applied to generate genetically engineered and synthetic hypoallergenic allergen derivatives for patient-tailored and safe vaccination against Type I allergy.

Allergens↗