Similar localization of conformational IgE epitopes on the house dust mite allergens Der p 5 and Der p 21 despite limited IgE cross-reactivity

BACKGROUND

Due to high IgE recognition frequency and high allergenic activity, Der p 5 and Der p 21 are clinically important house dust mite (HDM) allergens. The objective of this study was to characterize the immunodominant IgE epitopes of Der p 5 and Der p 21 responsible for their high allergenic activity.

METHODS

A panel of 12 overlapping peptides spanning the Der p 5 and Der p 21 sequence were synthesized to search for sequential IgE epitopes by direct testing for allergic patients' IgE reactivity. Peptide-specific antibodies raised in rabbits were used in inhibition studies for localizing conformational IgE epitopes which were visualized on the surfaces of the allergen structures by molecular modelling. IgE cross-reactivity between the allergens was investigated by IgE inhibition studies.

RESULTS

Immunodominant IgE epitopes defined by allergic patients' IgE on Der p 5 and Der p 21 were primarily of the conformational, discontinuous type including N- and C-terminal portions of the protein. They could be located on each allergen on one area with similar localization, but despite similar structure of the allergens, no relevant IgE cross-reactivity could be detected.

CONCLUSION

Our study shows that Der p 5 and Der p 21 contain a major conformational IgE epitope-containing area located on similar portions of their structure, but they lack relevant IgE cross-reactivity. These data are important for the development of modern allergy vaccines based on defined molecules for allergen-specific immunotherapy of HDM allergy.

Isolation of a high-affinity Bet v 1-specific IgG-derived ScFv from a subject vaccinated with hypoallergenic Bet v 1 fragments

Background

Recombinant hypoallergenic allergen derivatives have been used in clinical immunotherapy studies, and clinical efficacy seems to be related to the induction of blocking IgG antibodies recognizing the wild‐type allergens. However, so far no treatment‐induced IgG antibodies have been characterized.

Objective

To clone, express, and characterize IgG antibodies induced by vaccination with two hypoallergenic recombinant fragments of the major birch pollen allergen, Bet v 1 in a nonallergic subject.

Methods

A phage‐displayed combinatorial single‐chain fragment (ScFv) library was constructed from blood of the immunized subject and screened for Bet v 1‐reactive antibody fragments. ScFvs were tested for specificity and cross‐reactivity to native Bet v 1 and related pollen and food allergens, and epitope mapping was performed. Germline ancestor genes of the antibody were analyzed with the ImMunoGeneTics (IMGT) database. The affinity to Bet v 1 and cross‐reactive allergens was determined by surface plasmon resonance measurements. The ability to inhibit patients’ IgE binding to ELISA plate‐bound allergens and allergen‐induced basophil activation was assessed.

Results

A combinatorial ScFv library was obtained from the vaccinated donor after three injections with the Bet v 1 fragments. Despite being almost in germline configuration, ScFv (clone H3‐1) reacted with high affinity to native Bet v 1 and homologous allergens, inhibited allergic patients’ polyclonal IgE binding to Bet v 1, and partially suppressed allergen‐induced basophil activation.

Conclusion

Immunization with unfolded hypoallergenic allergen derivatives induces high‐affinity antibodies even in nonallergic subjects which recognize the folded wild‐type allergens and inhibit polyclonal IgE binding of allergic patients.

Molecular allergen profiling in horses by microarray reveals Fag e 2 from buckwheat as a frequent sensitizer

Background

Companion animals are also affected by IgE‐mediated allergies, but the eliciting molecules are largely unknown. We aimed at refining an allergen microarray to explore sensitization in horses and compare it to the human IgE reactivity profiles.

Methods

Custom‐designed allergen microarray was produced on the basis of the ImmunoCAP ISAC technology containing 131 allergens. Sera from 51 horses derived from Europe or Japan were tested for specific IgE reactivity. The included horse patients were diagnosed for eczema due to insect bite hypersensitivity, chronic coughing, recurrent airway obstruction and urticaria or were clinically asymptomatic.

Results

Horses showed individual IgE‐binding patterns irrespective of their health status, indicating sensitization. In contrast to European and Japanese human sensitization patterns, frequently recognized allergens were Aln g 1 from alder and Cyn d 1 from Bermuda grass, likely due to specific respiratory exposure around paddocks and near the ground. The most prevalent allergen for 72.5% of the tested horses (37/51) was the 2S‐albumin Fag e 2 from buckwheat, which recently gained importance not only in human but also in horse diet.

Conclusion

In line with the One Health concept, covering human health, animal health and environmental health, allergen microarrays provide novel information on the allergen sensitization patterns of the companion animals around us, which may form a basis for allergen‐specific preventive and therapeutic concepts.

House dust mites as potential carriers for IgE sensitization to bacterial antigens

Background

IgE reactivity to antigens from Gram‐positive and Gram‐negative bacteria is common in patients suffering from respiratory and skin manifestations of allergy, but the routes and mechanisms of sensitization are not fully understood. The analysis of the genome, transcriptome and microbiome of house dust mites (HDM) has shown that Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) species are abundant bacteria within the HDM microbiome. Therefore, our aim was to investigate whether HDM are carriers of bacterial antigens leading to IgE sensitization in patients suffering from atopic dermatitis.

Methods

Plasma samples from patients with AD (n = 179) were analysed for IgE reactivity to a comprehensive panel of microarrayed HDM allergen molecules and to S. aureus and E. coli by IgE immunoblotting. Antibodies specific for S. aureus and E. coli antigens were tested for reactivity to nitrocellulose‐blotted extract from purified HDM bodies, and the IgE‐reactive antigens were detected by IgE immunoblot inhibition experiments. IgE antibodies directed to bacterial antigens in HDM were quantified by IgE ImmunoCAP™ inhibition experiments.

Results

IgE reactivity to bacterial antigens was significantly more frequent in patients with AD sensitized to HDM than in AD patients without HDM sensitization. S. aureus and E. coli antigens were detected in immune‐blotted HDM extract, and the presence of IgE‐reactive antigens in HDM was demonstrated by qualitative and quantitative IgE inhibition experiments.

Conclusion

House dust mites (HDM) may serve as carriers of bacteria responsible for the induction of IgE sensitization to microbial antigens.

The quantity and quality of α-gal-specific antibodies differ in individuals with and without delayed red meat allergy

Background

IgG to galactose‐α‐1,3‐galactose (α‐gal) are highly abundant natural antibodies (Ab) in humans. α‐Gal‐specific IgE Ab cause a special form of meat allergy characterized by severe systemic reactions 3–7 h after consumption of red meat. We investigated 20 patients who experienced such reactions and characterized their α‐gal‐specific IgE and IgG responses in more detail.

Methods

α‐Gal‐specific IgE was determined by ImmunoCAP. IgE reactivity to meat extract and bovine gamma globulin (BGG) was assessed by immunoblotting and ELISA, respectively. In some experiments, sera were pre‐incubated with α‐gal or protein G to deplete IgG Ab. α‐Gal‐specific IgG_1–4 Ab in individuals with and without meat allergy were assessed by ELISA.

Results

In immunoblots, BGG was the most frequently recognized meat protein. Binding of IgE and IgG to BGG was confirmed by ELISA and completely abolished after pre‐incubation with α‐gal. Neither the depletion of autologous α‐gal‐specific IgG Ab nor the addition of α‐gal‐specific IgG Ab from nonallergic individuals changed the IgE recognition of BGG of meat‐allergic patients. Meat‐allergic patients showed significantly higher α‐gal‐specific IgG1 and IgG3 Ab than nonallergic individuals, whereas the latter showed significantly higher levels of α‐gal‐specific IgG4 Ab.

Conclusion

Patients with delayed meat allergy display IgE and IgG Ab that selectively recognize the α‐gal epitope on BGG. Their enhanced α‐gal‐specific IgE levels are accompanied by high levels of α‐gal‐specific IgG1 devoid of IgE‐blocking activity. This subclass distribution is atypical for food allergies and distinct from natural α‐gal IgG responses in nonallergic individuals.

The high molecular weight glutenin subunit Bx7 allergen from wheat contains repetitive IgE epitopes

BACKGROUND

Wheat is one of the most common food allergen sources for children and adults. The aim of this study was to characterize new wheat allergens using an IgE discovery approach and to investigate their IgE epitopes.

METHODS

A cDNA expression library representing the wheat transcriptome was constructed in phage lambda gt11 and screened with IgE antibodies from wheat food allergic patients. IgE-reactive cDNA clones coding for portions of high molecular weight (HMW) glutenin subunits were identified by sequence analysis of positive clones. IgE epitopes were characterized using recombinant fragments from the HMW Bx7 and synthetic peptides thereof for testing of allergic patients' sera and in basophil degranulation assays.

RESULTS

We found that the major IgE-reactive areas of HMW glutenins are located in the repetitive regions of the protein and could show that two independent IgE-reactive fragments from HMW Bx7 contained repetitive IgE epitopes.

CONCLUSIONS

Our results demonstrate that IgE antibodies from wheat food allergic patients can recognize repetitive epitopes in one of the important wheat food allergens. Recombinant HMW Bx7 may be included into the panel of allergens for component-resolved diagnosis of wheat food allergy.

Prophylactic and therapeutic vaccination with carrier-bound Bet v 1 peptides lacking allergen-specific T cell epitopes reduces Bet v 1-specific T cell responses via blocking antibodies in a murine model for birch pollen allergy

Background

Vaccines consisting of allergen-derived peptides lacking IgE reactivity and allergen-specific T cell epitopes bound to allergen-unrelated carrier molecules have been suggested as candidates for allergen-specific immunotherapy.

Objective

To study whether prophylactic and therapeutic vaccination with carrier-bound peptides from the major birch pollen allergen Bet v 1 lacking allergen-specific T cell epitopes has influence on Bet v 1-specific T cell responses.

Methods

Three Bet v 1-derived peptides, devoid of Bet v 1-specific T cell epitopes, were coupled to KLH and adsorbed to aluminium hydroxide to obtain a Bet v 1-specific allergy vaccine. Groups of BALB/c mice were immunized with the peptide vaccine before or after sensitization to Bet v 1. Bet v 1- and peptide-specific antibody responses were analysed by ELISA. T cell and cytokine responses to Bet v 1, KLH, and the peptides were studied in proliferation assays. The effects of peptide-specific and allergen-specific antibodies on T cell responses and allergic lung inflammation were studied using specific antibodies.

Results

Prophylactic and therapeutic vaccination with carrier-bound Bet v 1 peptides induced a Bet v 1-specific IgG antibody response without priming/boosting of Bet v 1-specific T cells. Prophylactic and therapeutic vaccination of mice with the peptide vaccine induced Bet v 1-specific antibodies which suppressed Bet v 1-specific T cell responses and allergic lung inflammation.

Conclusion and Clinical Relevance

Vaccination with carrier-bound allergen-derived peptides lacking allergen-specific T cell epitopes induces allergen-specific IgG antibodies which suppress allergen-specific T cell responses and allergic lung inflammation.

An assay that may predict the development of IgG enhancing allergen-specific IgE binding during birch immunotherapy

BACKGROUND

It has been shown that birch pollen immunotherapy can induce IgG antibodies which enhance IgE binding to Bet v 1. We aimed to develop a serological assay to predict the development of antibodies which enhance IgE binding to Bet v 1 during immunotherapy.

METHODS

In 18 patients treated by Bet v 1-fragment-specific immunotherapy, the effects of IgG antibodies specific for the fragments on the binding of IgE antibodies to Bet v 1 were measured by ELISA. Blocking and possible enhancing effects on IgE binding were compared with skin sensitivity to Bet v 1 after treatment.

RESULTS

We found that fragment-specific IgG enhanced IgE binding to Bet v 1 in two patients who also showed an increase of skin sensitivity to Bet v 1.

CONCLUSION

Our results indicate that it may be possible to develop serological tests which predict the induction of unfavourable IgG antibodies enhancing the binding of IgE to Bet v 1 during immunotherapy.

Molecular characterization of wheat allergens specifically recognized by patients suffering from wheat-induced respiratory allergy

BACKGROUND

Wheat (Triticum aestivum) is an important allergen source responsible for various clinical manifestations of allergy (i.e. food allergy, pollen allergy, respiratory allergy to flour-Baker's asthma).

OBJECTIVE

The objective of this study was the molecular and immunological characterization of new recombinant wheat allergens and to evaluate their usefulness for the diagnosis of allergy to wheat.

METHODS

A T. aestivum cDNA library was constructed and screened with serum IgE from patients suffering from wheat allergy to identify cDNAs coding for new wheat allergens. The allergen-encoding cDNAs were expressed in Escherichia coli and purified to homogeneity. IgE reactivity of recombinant proteins was analysed in RAST-based, non-denaturing dot blot experiments and by ELISA with sera from wheat allergic patients and their allergenic activity was assessed in basophil degranulation experiments.

RESULTS

We report the molecular characterization, recombinant expression and purification of five wheat allergens, a thioredoxin h isoform, glutathione transferase, 1-Cys-peroxiredoxin, profilin and dehydrin. Homologous proteins were identified by sequence comparisons in various plants. 1-Cys-peroxiredoxin appeared to be the most relevant of the newly identified wheat allergens according to prevalence of IgE recognition and results from basophil degranulation experiments. It showed IgE cross-reactivity with seed proteins from barley, rye, rice, maize, soy, oat and spelt. 1-Cys-peroxiredoxin, glutathione transferase and dehydrin were mainly recognized by patients with baker's asthma but not wheat-induced food allergy.

CONCLUSION AND CLINICAL RELEVANCE

The characterized recombinant wheat allergens may be useful for the development of serological tests which allow the discrimination of different clinical manifestations of wheat allergy.

Carrier-bound nonallergenic Der p 2 peptides induce IgG antibodies blocking allergen-induced basophil activation in allergic patients

BACKGROUND

More than 90% of house dust mite-allergic patients are sensitized to the major Dermatophagoides pteronyssinus allergen, Der p 2. The aim of this study was to develop and characterize an allergy vaccine based on carrier-bound Der p 2 peptides, which should allow reducing IgE- and T-cell-mediated side-effects during specific immunotherapy (SIT).

METHODS

Five Der p 2 peptides (P1-P5) were synthesized and analyzed regarding IgE reactivity and allergenic activity. Lymphoproliferative and cytokine responses induced with Der p 2 and Der p 2 peptides were determined in peripheral blood mononuclear cells from mite-allergic patients. Der p 2-specific IgG antibodies induced with carrier-bound Der p 2 peptides in mice and rabbits were tested for their capacity to inhibit IgE binding and basophil activation in allergic patients.

RESULTS

Of five overlapping peptides (P1-P5) covering the Der p 2 sequence, two peptides (P2 and P4) were identified, which showed no relevant IgE reactivity, allergenic activity, and induced lower Der p 2-specific T-cell activation than Der p 2. However, when coupled to a carrier, P2 and P4 induced Der p 2-specific IgG antibodies in animals, which inhibited allergic patients' IgE binding to the allergen and allergen-induced basophil activation similar as antibodies induced with Der p 2.

CONCLUSIONS

Carrier-bound Der p 2 peptides should allow avoiding IgE-mediated side-effects, and because of their low potential to activate allergen-specific T cells, they may reduce late-phase side-effects during SIT. Further, these peptides may be also useful for prophylactic vaccination.

Molecular characterization of Der p 10: a diagnostic marker for broad sensitization in house dust mite allergy

BACKGROUND

Tropomyosins represent clinically relevant seafood allergens but the role of mite tropomyosin, Der p 10, in house dust mite (HDM) allergy has not been studied in detail.

OBJECTIVE

To express and purify a recombinant Der p 10 with equivalent IgE reactivity as natural Der p 10 and to evaluate its IgE reactivity and allergenic activity in HDM-allergic patients.

METHODS

rDer p 10 was expressed in Escherichia coli, purified and characterized by mass spectrometry and circular dichroism. It was tested for IgE reactivity in 1322 HDM-allergic patients. Detailed IgE-reactivity profiles to six HDM allergens (Der p 1, 2, 5, 7, 10, 21) were established for subgroups of Der p 10-positive and -negative patients. The allergenic activity of rDer p 10 was evaluated in basophil degranulation experiments.

RESULTS

rDer p 10 is an α-helical protein sharing IgE epitopes with nDer p 10. It is recognized by 15.2% of HDM-allergic patients. Der p 10-negative patients were primarily sensitized to Der p 1 and/or Der p 2, whereas Der p 10-positive patients reacted to several other HDM allergens besides the major allergens (Der p 1, Der p 2) or showed a rather selective Der p 10 reactivity. The allergenic activity of Der p 10 was generally low but patients could be identified who suffered from clinically relevant HDM allergy due to Der p 10 sensitization.

CONCLUSION AND CLINICAL RELEVANCE

Der p 10 may be a diagnostic marker for HDM-allergic patients with additional sensitization to allergens other than Der p 1 and Der p 2. Such patients may require attention when allergen-specific immunotherapy is considered.

Cigarette smoke facilitates allergen penetration across respiratory epithelium

BACKGROUND

The association between cigarette smoke exposure and allergic airway disease is a matter for debate. We sought to investigate in an in vitro system whether active smoking reduces the integrity and barrier function of the respiratory epithelium and thus facilitates allergen penetration.

METHODS

We cultured the human bronchial epithelial cell line 16HBE14o- in a transwell culture system as a surrogate for the intact respiratory epithelium. The cell monolayer was exposed to standardized cigarette smoke extract (CSE). The extent and effects of trans-epithelial allergen penetration were measured using 125I-labelled purified major respiratory allergens (rBet v 1, rPhl p 5 and rDer p 2) and histamine release experiments.

RESULTS

Exposure of cells to concentrations of CSE similar to those found in smokers induced the development of para-cellular gaps and a decrease in trans-epithelial resistance. CSE exposure induced a more than threefold increase in allergen penetration. Increased subepithelial allergen concentrations provoked a substantial augmentation of histamine release from sensitized basophils.

CONCLUSIONS

Our results indicate that cigarette smoke is a potent factor capable of reducing the barrier function of the respiratory epithelium for allergens and may contribute to increased allergic inflammation, exacerbation of allergic disease and boosting of IgE memory.

Variability of IgE reactivity profiles among European mite allergic patients

BACKGROUND

House dust mites (HDM) Dermatophagoides pteronyssinus are a frequent indoor allergen source. Our aim was to determine the frequencies of IgE reactivity to purified HDM allergen molecules in mite allergic patients from different parts of Europe in order to establish an allergen panel for diagnosis of HDM allergy.

MATERIALS AND METHODS

Populations of D. pteronyssinus-allergic patients from Austria (n = 56), France (n = 55), Italy (n = 67) and Sweden (n = 65) and storage mite allergic patients from Sweden (n = 31) were analysed for IgE reactivity to eight purified natural (n) and recombinant (r) D. pteronyssinus allergens (nDer p 1, rDer p 2, nDer p 4, rDer p 5, rDer p 7, rDer p 8, rDer p 10 and rDer p 14) in RAST-based dot blot assays.

RESULTS

Using a combination of Der p 1 and Der p 2, at least 97% of the D. pteronyssinus-allergic patients could be diagnosed in each of the HDM allergic populations. However, more than 50% of the patients also reacted with other allergens and significant variabilities regarding the frequencies of IgE reactivity to individual allergen molecules were found. Patients with a predominant storage mite allergy showed none or only very weak IgE reactivity to purified D. pteronyssinus allergens.

CONCLUSIONS

Purified Der p 1 and Der p 2 are sufficient for the diagnosis of > or = 97% of D. pteronyssinus allergic patients in Europe, but other allergens may also play an important role for the diagnosis and treatment of HDM allergy.

Characterization of Der p 21, a new important allergen derived from the gut of house dust mites

BACKGROUND

The house dust mite (HDM) Dermatophagoides pteronyssinus is a major allergen source eliciting allergic asthma. The aim of the study was to identify new important HDM allergens associated with allergic asthma.

METHODS

A cDNA coding for a new mite allergen, designated Der p 21, was isolated using immunoglobulin E (IgE) antibodies from patients with allergic asthma out of a D. pteronyssinus expression cDNA library and expressed in Escherichia coli.

RESULTS

Circular dichroism analysis of the purified allergen showed that rDer p 21 (14 726 Da) is one of the few mite allergens with an alpha-helical secondary structure. The protein exhibited high thermal stability and refolding capacity, and, as determined by small angle X-ray scattering, formed a dimer consisting of two flat triangles. rDer p 21 bound high levels of patients' IgE antibodies and showed high allergenic activity in basophil activation experiments. Rabbit anti-Der p 21 IgG antibodies inhibited mite-allergic patients' IgE binding and allowed the ultrastructural localization of the allergen in the midgut (epithelium, lumen and faeces) of D. pteronyssinus by immunogold electron microscopy. Der p 21 revealed sequence homology with group 5 mite allergens, but IgE and IgG reactivity data and cross-inhibition studies identified it as a new mite allergen.

CONCLUSIONS

Der p 21 is a new important mite allergen which is liberated into the environment via faecal particles and hence may be associated with allergic asthma.

From allergen genes to new forms of allergy diagnosis and treatment

Type I allergy represents an important health problem that affects more than 25% of the population in industrialized countries. Specific immunotherapy is one of the few causative treatment approaches for type I allergy and is currently performed with crude allergen extracts, which consist of a mixture of allergenic and nonallergenic components, are difficult to standardize and cannot be applied according to the patient's reactivity profile. With the introduction of molecular biological techniques into allergy research, a large panel of individual recombinant allergens has become available. Recombinant allergens can be used for improved diagnosis of allergy to determine the patient's sensitization profile, which is a prerequisite to select the allergens for patient-tailored immunotherapy. They allow the elucidation of the properties of allergens and of the mechanisms of allergy as well as of the mechanisms of immunotherapy. Moreover, recombinant allergens allow the development of hypoallergenic allergen derivatives with reduced allergenic activity and retained immunogenicity. First immunotherapy trials with hypoallergenic allergen derivatives have shown that this treatment might improve immunotherapy in the near future. This review summarizes the results, which were obtained with recombinant allergens and hypoallergenic allergen derivatives. The experiences from the in vitro and in vivo evaluation of the hypoallergenic derivatives and from clinical studies as well as the contribution of hypoallergenic derivatives to develop new treatment strategies and possibly prophylactic vaccination strategies are discussed.

Recombinant Allergens Promote Expression of Aminopeptidase-N (CD13) on Basophils in Allergic Patients

IgE-dependent activation of basophils is associated with upregulation of several surface molecules. We recently identified the surface enzyme aminopeptidase N (CD13) as a novel activation antigen on human basophils. In the present study, we asked whether CD13 can be employed as a novel marker of allergen-induced activation of basophils in allergic individuals. Patients allergic to major allergens from grass pollen (Phl p 1, Phl p 5), birch pollen (Bet v 1), or house dust mites (Der p 2), were examined. Blood basophils were exposed to various concentrations of recombinant allergens for 15 minutes, and examined for expression of CD13 by multicolor flow cytometry. The allergen-induced upregulation of CD13 was compared with allergen-dependent increases in expression of CD63 and CD203c. Exposure to recombinant allergens resulted in an increase in expression of CD13 on basophils in all sensitized individuals, whereas no increase in CD13 was seen in healthy controls. The effects of the recombinant allergens on CD13-expression were dose- and time-dependent, were not observed in the absence of extracellular calcium, and were counteracted by preincubation of basophils with the PI3-kinase-targeting drugs staurosporin and LY294002. There was a good correlation between allergen-induced upregulation of CD13, CD63, and CD203c on basophils. In aggregate, our data show that recombinant allergens promote expression of CD13 on basophils in sensitized individuals. The functional significance and diagnostic implications of this observation remain to be determined.

Clinical improvement and immunological changes in atopic dermatitis patients undergoing subcutaneous immunotherapy with a house dust mite allergoid: a pilot study

BACKGROUND

House dust mites (HDMs) represent significant indoor allergen sources for patients with atopic dermatitis (AD). Subcutaneous allergen-specific immunotherapy (SCIT) has been shown to be successful in patients with allergic rhinitis and mild asthma and might represent an attractive therapeutic option for the long-term treatment of HDM sensitizations in AD patients. However, only a few studies have been conducted on the effectiveness of HDM SCIT in AD, resulting in controversial clinical results. Data on immunological changes induced by SCIT in AD patients are rare.

OBJECTIVES

We performed an open pilot study to assess clinical changes and objective laboratory parameters and evaluate the benefit of HDM SCIT in 25 AD patients with IgE-mediated sensitization against HDM.

METHODS

The severity of AD was evaluated by the severity scoring of atopic dermatitis system (SCORAD). Specific IgE and IgG4 against HDM and serum levels of TARC/CCL17, MDC/CCL22, IL-16, IL-4, IFN-gamma, IL-10 and TGF-beta1 were measured during SCIT.

RESULTS

Subjective and objective SCORAD improved significantly within only 4 weeks of treatment. The level of the tolerogenic cytokine IL-10 increased, whereas CCL17 and IL-16 decreased in the sera of the patients during SCIT. Allergen specific IgE decreased, while IgG4 increased during SCIT.

CONCLUSION

In this open-label pilot study, SCIT with an HDM extract in patients with AD led to a significant improvement of AD mirrored by a reduction of SCORAD as well as serological and immunological changes, which might serve as valuable parameters to estimate the therapeutic effect of SCIT.

Allergen-induced interleukin-9 production in vitro: correlation with atopy in human adults and comparison with interleukin-5 and interleukin-13

BACKGROUND

The contribution of IL-9 to human atopy is supported by genetic studies. However, IL-9 production in response to allergen in vitro has been reported only in children.

OBJECTIVE

Study IL-9 induction by allergen in adults, compare it with IL-5 and IL-13 and evaluate its association with atopy.

METHODS

Peripheral blood mononuclear cell (PBMC) from control adults and from atopic patients were cultured with various allergens or phytohaemagglutinin (PHA) and secreted IL-5, IL-9 and IL-13 were measured by ELISA.

RESULTS

IL-9 was produced in response to Dermatophagoides pteronyssinus (Der p) by PBMC from Der p-hypersensitive adults at levels equivalent to those induced by PHA but with slower kinetics. The induction of IL-9 was allergen specific, reflecting donor RAST profile. In Der p-triggered reactions of non-atopic and atopic subjects, IL-9 showed the highest selectivity for atopics, IL-5 and IL-13 being produced more frequently in non-atopic donors. Significant correlations with specific IgE titres were found for IL-9 with all allergens tested (Der p and two peptides of Bet v 1 birch allergen). For IL-5 and IL-13, they were in the same range for Der p but more variable for birch allergens. Patterns of cytokine production by individual patients in response to allergen reflected these differences: for Der p, IL-5, IL-9 and IL-13 productions were strongly correlated but for birch IL-5 differed from the latter two. The in vitro production of IL-9 reflected clinical hypersensitivity profiles and was higher in individuals with asthma than in those with disease limited to rhinitis and/or conjunctivitis.

CONCLUSIONS

Allergen-triggered IL-9 production in vitro is an excellent marker for atopy in adults given its virtual absence in allergen-stimulated PBMC from non-atopic individuals and its correlation with allergen-specific IgE and asthma.

Absence of systemic immunologic changes during dose build-up phase and early maintenance period in effective specific sublingual immunotherapy in children

BACKGROUND

Sublingual immunotherapy (SLIT) has been reported to be a safe treatment for inhalant allergies in children. Yet the immunologic mechanisms resulting in clinical improvement are poorly understood.

OBJECTIVE

To identify early systemic immunologic changes during the first 8 weeks of clinically effective SLIT to grass pollen, tree pollen or house dust mite in paediatric patients with allergic rhinoconjunctivitis and/or asthma.

METHODS

Peripheral blood mononuclear cells and plasma samples of 13 children with reduced symptoms after 1 year of SLIT were obtained before therapy and at 2 and 8 weeks after the initiation of SLIT. Allergen-specific lymphocyte proliferation assays were performed, and allergen-induced cytokine production (IL-2, IL-4, IL-10, IFN-gamma, and TGF-beta(1)) was measured by ELISA and flow cytometry. Allergen-specific IgE, IgG1, IgG4, and IgA levels in plasma samples were determined in ELISA.

RESULTS

During the first 8 weeks of successful SLIT, allergen-specific lymphoproliferation (n=13) as well as levels of allergen-specific intracellular (n=8) and secreted cytokines (n=9) did not change significantly. In addition, no alterations in levels of allergen-specific Igs (n=7) were observed.

CONCLUSION

We could not find any early systemic immunologic changes during the first 8 weeks of clinically effective SLIT to inhalant allergens in paediatric patients with allergic rhinoconjunctivitis and/or asthma.

The role of Foxp3+ T cells in long-term efficacy of prophylactic and therapeutic mucosal tolerance induction in mice

BACKGROUND

Mucosal tolerance induction is suggested as treatment strategy for allergic diseases. Using a murine model of birch pollen (BP) allergy we investigated the long-term efficacy and the underlying mechanisms of mucosal tolerance induction with two structurally different molecules in a prophylactic and in a therapeutic set-up.

METHODS

The three-dimensional major BP allergen Bet v 1 or a nonconformational hypoallergenic fragment thereof was intranasally applied before (prophylaxis) or after sensitization (therapy).

RESULTS

In the prophylactic application both the Bet v 1 allergen and the fragment prevented allergic sensitization, and this effect lasted for 1 year. In the therapeutic approach established allergic immune responses were also suppressed after treatment with either of the molecules. However, a long-lasting curative effect (6 months) was only achieved with the Bet v 1 allergen but not with the Bet v 1 fragment. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis of splenocytes revealed that tolerance induction with the Bet v 1 allergen was associated with enhanced expression of transforming growth factor (TGF)-beta, interleukin (IL)-10, and Foxp3 mRNA in CD4+ T cells, whereas treatment with the fragment led to the induction of either Foxp3 (prophylaxis) or IL-10 (therapy) alone.

CONCLUSION

From these data we concluded (i) that the mechanisms underlying peripheral tolerance are linked to the conformation of the antigen, (ii) that mucosal tolerance is mediated by separate regulatory cell subsets, and (iii) that the long-term efficacy of immunosuppression is associated with the presence of Foxp3+ T cells.

Comparison of purified Dermatophagoides pteronyssinus allergens and extract by two-dimensional immunoblotting and quantitative immunoglobulin E inhibitions

BACKGROUND

The allergens of the house dust mite (Dermatophagoides pteronyssinus, Der p), one of the most important indoor allergen sources, occur as isoallergens that differ in their amino acid sequence. These variations may influence allergenic activity and thus may have impact on diagnostic tests and specific immunotherapy.

OBJECTIVE

We investigated whether single purified recombinant mite allergens contain the IgE epitopes of the natural Der p isoallergens.

METHODS

A panel of purified recombinant (rDer p 2, 5, 7, 8, 10 and 14) and two natural (nDer p 1 and 4) mite allergens were used to establish IgE reactivity profiles of Der p allergic patients and to inhibit IgE reactivity to two-dimensionally separated Der p isoallergens. In addition, we determined the percentage of Der p extract-specific IgE which could be preadsorbed with a mixture of purified mite allergens (nDer p 1, rDer p 2, 5, 7, 8 and 10) from sera of mite-allergic patients (n=18) in a non-denaturing RAST-based inhibition.

RESULTS

We demonstrate that single recombinant mite allergens inhibit IgE reactivity to the corresponding natural isoallergens. A mixture of purified mite allergens (nDer p 1, rDer p 2, 5, 7, 8 and 10) bound on an average 76% of Der p-specific IgE antibodies.

CONCLUSION

The studied recombinant and natural mite allergens contain a large portion of Der p-specific IgE and may be used for diagnostic tests and therapy of Der p allergy.

Development of an in vitro system for the study of allergens and allergen-specific immunoglobulin E and immunoglobulin G: Fce receptor I supercross-linking is a possible new mechanism of immunoglobulin G-dependent enhancement of type I allergic reactions

BACKGROUND

IgE-dependent activation of mast cells (MCs) is a key pathomechanism of type I allergies. In contrast, allergen-specific IgG Abs are thought to attenuate immediate allergic reactions by blocking IgE binding and by cross-linking the inhibitory Fcgamma receptor IIB on MCs.

OBJECTIVES

To establish a defined in vitro system using human MCs to study the biological activity of allergens and to investigate the role of allergen-specific IgE and IgG.

METHODS

Purified human intestinal MCs sensitized with different forms of specific IgE Abs were triggered by monomeric and oligomeric forms of recombinant Bet v 1, the major birch pollen allergen, in the presence or absence of allergen-specific IgG Abs. Results MCs sensitized with an anti-Bet v 1 IgE mAb or sera obtained from birch pollen allergic patients released histamine and sulphidoleukotrienes after exposure to oligomeric Bet v 1. Monomeric Bet v 1 provoked mediator release only in MCs sensitized with patients sera but not in MCs sensitized with anti-Bet v 1 IgE mAb. Interestingly, MC activation could be induced by supercross-linking of monomeric Bet v 1 bound to monovalent IgE on MCs with a secondary allergen-specific IgG pAb. By using IgG F(ab')2 fragments we provide evidence that this effect is not a result of IgG binding to Fcgamma receptors.

CONCLUSION

This assay represents a new tool for the in vitro study of MC activation in response to natural and genetically modified allergens. Fcepsilon receptor I supercross-linking by allergen-specific IgG Abs provides a possible new mechanism of IgG-dependent enhancement of type I allergic reactions.

Vaccination with genetically engineered allergens prevents progression of allergic disease

IgE-mediated allergy affects >25% of the population in industrialized countries. Repeated contact with the disease-eliciting allergens induces rises of allergen-specific IgE Abs and progression of the disease to more severe manifestations. Our study uses a type of vaccine that is based on genetically modified allergen derivatives to treat allergic patients. We developed hypoallergenic derivatives of the major birch pollen allergen, Bet v 1, by genetic engineering and vaccinated birch pollen-allergic patients (n = 124) in a double-blind, placebo-controlled study. Active treatment induced protective IgG Abs that inhibited allergen-induced release of inflammatory mediators. We also observed a reduction of cutaneous sensitivity as well as an improvement of symptoms in actively treated patients. Most important, rises of allergen-specific IgE induced by seasonal birch pollen exposure were significantly reduced in vaccinated patients. Vaccination with genetically engineered allergen derivatives is a therapy for allergy that not only ameliorates allergic reactions but also reduces the IgE production underlying the disease.

Component-resolved diagnosis of house-dust mite allergy with purified natural and recombinant mite allergens

BACKGROUND

Mites belong to the most frequent and potent allergen sources. Immunotherapy with mite allergen extracts is frequently performed if allergen avoidance is not possible or successful. However, highly controversial results have been reported for mite-specific immunotherapy.

OBJECTIVE

The aim of this study was to develop diagnostic concepts that may contribute to an improved selection of patients for immunotherapy with Der p allergen extracts and that may be used for immunological monitoring of patients undergoing this treatment.

METHODS

The IgE reactivity profiles to Der p extract were determined in a Middle European mite-allergic population by IgE immunoblotting and by using a panel of seven purified natural or recombinant Der p allergens (nDer p 1, nDer p 4, rDer p 2, rDer p 5, rDer p 7, rDer p 8, rDer p 10). Furthermore, we investigated the sensitization and cross-reactivity to house-dust- and storage-mite allergen extracts by CAP FEIA measurements and by IgE competition studies.

RESULTS

More than 95% of the patients could be diagnosed with a combination of nDer p 1 and rDer p 2. With the methods used, we could discriminate mite-allergic patients who were mainly sensitized to the major Der p allergens (Der p 1, Der p 2) from patients with a broad sensitization profile, including highly cross-reactive allergens (e.g. Der p 10: tropomyosin) as well as reactivity to storage mites.

CONCLUSIONS

Diagnostic tests containing the major mite allergens (i.e. Der p 1, Der p 2) and highly cross-reactive mite allergens (e.g. Der p 10) may improve the diagnostic selection of patients for immunotherapy with Der p extracts. These tests may also be used for the immunological monitoring of patients undergoing immunotherapy.

Vaccines for birch pollen allergy based on genetically engineered hypoallergenic derivatives of the major birch pollen allergen, Bet v 1

BACKGROUND

We have recently engineered recombinant derivatives of the major birch pollen allergen Bet v 1 (rBet v 1 fragments and trimer) with strongly reduced allergenic activity.

OBJECTIVE

The aim of this study was the in vivo characterization of potential allergy vaccines based on Al(OH)3-adsorbed genetically modified rBet v 1 derivatives in mice.

METHODS

BALB/c mice were immunized either with courses of nine injections of increasing doses of Al(OH)3-adsorbed rBet v 1 wild-type, rBet v 1 fragments, rBet v 1 trimer or Al(OH)3 alone in weekly intervals or with three high-dose injections applied in intervals of 3 weeks. Humoral immune responses to rBet v 1 wild-type and homologous plant allergens were measured by ELISA and Western blotting, and the ability of mouse antibodies to inhibit the binding of allergic patients IgE to Bet v 1 was studied by ELISA competition experiments.

RESULTS

In both schemes, hypoallergenic rBet v 1 derivatives induced low IgE but high IgG1 responses against rBet v 1 wild-type. The IgG1 antibodies induced by genetically modified rBet v 1 derivatives cross-reacted with natural Bet v 1 and its homologues from alder (Aln g 1) as well as hazel (Cor a 1) and strongly inhibited the binding of birch pollen allergic patients' IgE to Bet v 1 wild-type.

CONCLUSION

Genetically modified hypoallergenic rBet v 1 derivatives induce blocking antibodies in vivo. Their safety and efficacy for the treatment of birch pollen and associated plant allergies can now be evaluated in clinical immunotherapy studies.

Analysis of the sensitization profile towards allergens in central Africa

BACKGROUND

Almost no information is available regarding the prevalence of IgE-mediated allergies and the disease-eliciting allergens in tropical Africa.

OBJECTIVE

To study IgE-mediated allergies and the allergen profile in allergic patients from Zimbabwe.

METHODS

The frequency of sensitization to common environmental allergen sources was determined by skin prick testing in 650 allergic patients from Zimbabwe. Fifty representative sera were analysed for IgE reactivity to 20 respiratory and 20 food allergen extracts by multiallergen extract testing. The IgE reactivity profiles to recombinant pollen and mite allergens were compared between grass pollen- and mite-sensitized patients from Zimbabwe and central Europe. Sera from grass pollen-allergic patients were also analysed for IgE reactivity to nitrocellulose-blotted natural timothy grass and Bermuda grass pollen allergens.

RESULTS

IgE-mediated allergies were found to be common in Zimbabwe. Similar to the situation in central Europe, mites and grass pollens represented the most prevalent allergen sources. However, the IgE reactivity profiles determined with single recombinant pollen and mite allergens revealed interesting differences between the European and African patients, which most likely reflect the local allergen exposure.

CONCLUSIONS

The striking differences regarding sensitization to grass pollen and mite allergens between African and European patients revealed by recombinant allergen-based testing emphasize the need for component-resolved allergy testing to optimize allergy prevention and therapy in different populations.

Nasal challenges with recombinant derivatives of the major birch pollen allergen Bet v 1 induce fewer symptoms and lower mediator release than rBet v 1 wild-type in patients with allergic rhinitis

BACKGROUND

Genetic engineering of the major birch pollen allergen (Bet v 1) has led to the generation of recombinant Bet v 1 derivatives with markedly reduced IgE-binding capacity, but with retained T cell activating ability.

OBJECTIVE

To compare the mucosal reactivity to rBet v 1 derivatives with rBet v 1 wild-type as basis for new therapeutic strategies for birch pollen allergy based on mucosal tolerance induction.

METHODS

Outside the pollen season, 10 patients with birch pollen allergic rhinitis and mild asthma underwent four nasal challenge-sessions in a randomized, double-blind, and cross-over design, employing increasing doses of rBet v 1 fragment mix, rBet v 1 trimer, rBet v 1 wild-type and diluent (albumin). Nasal lavage fluids (NAL) were collected before the challenge-series as well as 10 min, 4 and 24 h thereafter. Nasal lavage fluid levels of tryptase as well as EPO and ECP were measured as indices of mast cell and eosinophil activity, respectively.

RESULTS

All 10 patients tolerated the highest accumulated dose, 8.124 microg, when challenged with rBet v 1 trimer, eight with rBet v 1 fragments compared to one when challenged with rBet v 1 wild-type. No late phase reactions were observed. The change in tryptase levels (pre-challenge vs. 10 min) was significantly lower after challenges with rBet v 1 trimer and rBet v 1 fragments than with rBet v 1 wild-type. The change in EPO/ECP concentration pre-challenge versus 4 h post-challenge was lower for rBet v 1 trimer and the change was significantly lower when pre-challenge versus 24 h post-challenge to rBet v 1 fragments and rBet v 1 wild-type was examined.

CONCLUSION

The derivatives induced significantly fewer symptoms and lower mast cell and eosinophil activation than rBet v 1 wild-type upon application to the nasal mucosa. They could in the future be candidates for immunotherapy based on mucosal tolerance induction.

Skin testing with wild-type recombinant birch pollen allergens and hypoallergenic modified molecules

Our aim was to compare the allergenic activity of wild type rBet v 1 with recombinant Bet v 1 derivatives (rBet v 1 fragments, dimer and trimer) with potentially reduced anaphylactic activity by skin testing in a French population.

METHODS

Among the 36 birch pollen allergic patients included in the study, 29 were tested by skin prick testing and 30 by intradermal injections with purified monosubstances: rBet v 1 fragments (F1: aa1-74 and F2: aa75-160), Bet v 1 dimer and trimer. Intradermal tests were performed by the endpoint intradermal titration method. Tests were performed over a period of 6 months (before, during and after birch pollen season).

RESULTS

All patients showed lower reactivity with the modified rBet v 1 allergens, both in skin prick- and intradermal tests. In 25 and 23 out of 29 patients the lowest concentration of fragment 1 and 2 respectively, resulting in a positive prick test was 100 fold higher than the lowest concentration of monomer resulting in a positive prick test. For dimer it was 100 fold or more in 25 out of 29 patients, and for trimer it was 100 fold or superior in 26 out of 29 patients. By intradermal testing, the end point concentration was 160 fold higher for trimer than for monomer in 24 patients and 40 fold higher in 5 patients. For the 2 fragments the end point concentration was 160 fold higher in 20 out of 22 patients.

CONCLUSION

rBet v 1 fragments and trimer may represent candidate molecules for immunotherapy of birch pollen allergy with reduced risk of anaphylactic side effects.

Intranasal treatment with a recombinant hypoallergenic derivative of the major birch pollen allergen Bet v 1 prevents allergic sensitization and airway inflammation in mice

BACKGROUND

The major birch pollen allergen Bet v 1 represents one of the most prevalent environmental allergens responsible for allergic airway inflammation.

OBJECTIVE

In the present study we sought to compare the complete recombinant Bet v 1 allergen molecule with genetically produced hypoallergenic fragments of Bet v 1 regarding mucosal tolerance induction in a mouse model of allergic asthma.

METHODS

BALB/c mice were intranasally treated with recombinant Bet v 1 or with two recombinant Bet v 1 fragments (F I: aa 1-74; F II: aa 75-160) prior to aerosol sensitization with birch pollen and Bet v 1.

RESULTS

Intranasal application of F II, containing the major T cell epitope, led to significant reduction of IgE/IgG1 antibody responses, in vitro cytokine production (IL-5, IFN-gamma, IL-10) and negative immediate cutaneous hypersensitivity reactions comparable to the pretreatment with the complete rBet v 1 allergen. Moreover, airway inflammation (eosinophilia, IL-5) was inhibited by the pretreatment with either the complete Bet v 1 or F II. However, for prevention of airway hyperresponsiveness the complete molecule was required. The mechanisms leading to immunosuppression seemed to differ in their dependence on the conformation of the molecules, since tolerance induced with the complete Bet v 1, but not with F II, was transferable with spleen cells and associated with increased TGF-beta mRNA levels.

CONCLUSION

We conclude that mucosal tolerance induction with recombinant allergens and genetically engineered hypoallergenic derivatives thereof could provide a convenient and safe intervention strategy against type I allergy.

Genetic engineering of a hypoallergenic trimer of the major birch pollen allergen Bet v 1

An estimated 100 million individuals suffer from birch pollen allergy. Specific immunotherapy, the only curative allergy treatment, can cause life-threatening anaphylactic side effects. Here, we report the genetic engineering of a recombinant trimer consisting of three covalently linked copies of the major birch pollen allergen, Bet v 1. The trimer exhibited profoundly reduced allergenic activity but contained similar secondary structures such as Bet v 1 wild type, Bet v 1-specific B cell and T-cell epitopes, and induced Th1 cytokine release. As immunogen, rBet v 1 trimer induced IgG antibodies, which blocked patients' IgE binding to Bet v 1 and related allergens. Thus, rBet v 1 trimer represents a novel hypoallergenic vaccine prototype for treatment of one of the most frequent allergy forms.

Release of allergen-bearing cytoplasm from hydrated pollen: a mechanism common to a variety of grass (Poaceae) species revealed by electron microscopy

BACKGROUND

The release of submicronic particles from grass pollen after rainfall was suggested to be responsible for outbreaks of grass pollen asthma. Recently, we provided evidence for the release of respirable allergen-bearing particles from hydrated ryegrass (Lolium perenne ) pollen as a possible explanation for this phenomenon.

OBJECTIVE

We investigated whether water-induced release of respirable allergen-bearing particles could be a mechanism common to several members of the sweet grass family Poaceae (Gramineae).

METHODS

Pollens from 6 different Poaceae species were hydrated in water and examined by means of scanning electron microscopy for release of cytoplasmic materials. Rabbit antisera raised against purified recombinant group 1 and 5 allergens were used for immunogold labeling of expelled materials by means of field emission scanning electron microscopy. In addition, group 1 and 5 allergens were immunogold-localized on ultrathin sections.

RESULTS

Fresh Poaceae pollens expelled cytoplasmic materials containing group 1 and 5 allergens on hydration in water. Expulsion of submicronic particles strongly decreased after 1 month of storage.

CONCLUSIONS

Our results suggest expulsion of cytoplasm after hydration as a mechanism common to pollens of important allergenic grasses. The water-induced release of respirable allergen-bearing particles from grass pollens might explain asthma attacks observed after rainfall during the grass pollen season.

A Highly Allergenic Fragment of the Major Timothy Grass Pollen Allergen, Phl p 5, Defined by a Human Monoclonal IgE Antibody

We report the characterization of a domain of the major timothy grass pollen allergen, Phl p 5A, which contains the binding site for a human monoclonal IgE antibody. The human monoclonal IgE antibody fragment (Fab) was obtained from an IgE combinatorial library constructed from lymphocytes of a grass pollen-allergic patient. An 11.2-kD N-terminal fragment representing approximately one third of the complete Phl p 5A allergen could be identified to contain the binding site for the IgE Fab. The rPhl p 5A fragment revealed an extremely high allergenic activity in skin test experiments which in some cases equaled that of the complete Phl p 5A allergen. The rPhl p 5A domain thus represents an allergen fragment containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation.

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.

T cell epitope-containing hypoallergenic recombinant fragments of the major birch pollen allergen, Bet v 1, induce blocking antibodies

Allergen-specific immunotherapy represents one of the few curative approaches toward type I allergy. Up to 25% of allergic patients are sensitized against the major birch pollen allergen, Bet v 1. By genetic engineering we produced two recombinant (r) Bet v 1 fragments comprising aa 1-74 and aa 75-160 of Bet v 1, which, due to a loss of their native-like fold, failed to bind IgE Abs and had reduced allergenic activity. Here we show that both fragments covering the full Bet v 1 sequence induced human lymphoproliferative responses similar to rBet v 1 wild type. The C-terminal rBet v 1 fragment induced higher lymphoproliferative responses than the N-terminal fragment and represented a Th1-stimulating segment with high IFN-gamma production, whereas the N-terminal fragment induced higher IL-4, IL-5, and IL-13 secretion. Immunization of mice and rabbits with rBet v 1 fragments induced IgG Abs, which cross-reacted with complete Bet v 1 and Bet v 1-related plant allergens and strongly inhibited the IgE binding of allergic patients to these allergens. Thus, our results demonstrate that hypoallergenic T cell epitope-containing rBet v 1 fragments, despite lacking IgE epitopes, can induce Abs in vivo that prevent the IgE binding of allergic patients to the wild-type allergen. The overall demonstration of the immunogenic features of the hypoallergenic rBet v 1 fragments will now enable clinical studies for safer and more efficient specific immunotherapy.

A human monoclonal IgE antibody defines a highly allergenic fragment of the major timothy grass pollen allergen, Phl p 5: molecular, immunological, and structural characterization of the epitope-containing domain

Almost 90% of grass pollen-allergic patients are sensitized against group 5 grass pollen allergens. We isolated a monoclonal human IgE Fab out of a combinatorial library prepared from lymphocytes of a grass pollen-allergic patient and studied its interaction with group 5 allergens. The IgE Fab cross-reacted with group 5A isoallergens from several grass and corn species. By allergen gene fragmentation we mapped the binding site of the IgE Fab to a 11.2-kDa N-terminal fragment of the major timothy grass pollen allergen Phl p 5A. The IgE Fab-defined Phl p 5A fragment was expressed in Escherichia coli and purified to homogeneity. Circular dichroism analysis revealed that the rPhl p 5A domain, as well as complete rPhl p 5A, assumed a folded conformation consisting predominantly of an alpha helical secondary structure, and exhibited a remarkable refolding capacity. It reacted with serum IgE from 76% of grass pollen-allergic patients and revealed an extremely high allergenic activity in basophil histamine release as well as skin test experiments. Thus, the rPhl p 5A domain represents an important allergen domain containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation and, perhaps later, for the development of generally applicable allergen-specific therapy strategies.

Comparison of genetically engineered hypoallergenic rBet v 1 derivatives with rBet v 1 wild-type by skin prick and intradermal testing: results obtained in a French population

BACKGROUND

Bet v 1, the major allergen in birch pollen, is recognized by more than 90% of patients allergic to birch in northern and central Europe. Immunotherapy is commonly performed with birch pollen extracts. Recently, hypoallergenic derivatives of Bet v 1 (rBet v 1 fragments, rBet v 1 dimer and trimer) were constructed and purified.

OBJECTIVE

Our aim was to compare the allergenic activity of wild-type rBet v 1 with recombinant Bet v 1 derivatives (rBet v 1 fragments, dimer and trimer) with potentially reduced anaphylactic activity by skin testing in a French population.

METHODS

Among the 36 birch pollen allergic patients included in the study, 29 were tested by skin prick testing and 30 by intradermal injections with purified monosubstances: rBet v 1 fragments (F1: aa1-74 and F2: aa75-160), Bet v 1 dimer and trimer. Intradermal tests were performed by the end-point intradermal titration method. Eight of the intradermally-tested patients were previously hyposensitized. Tests were performed over a period of 6 months (before, during and after birch pollen season); Bet v 1-specific IgE and IgG4 subclass responses were measured by immunoblotting and ELISA.

RESULTS

All patients showed lower reactivity with the modified rBet v 1 allergens, both in skin prick and intradermal tests. In 25 and 23 out of 29 patients the lowest concentration of fragment 1 and 2, respectively, resulting in a positive prick test was 100-fold higher than the lowest concentration of monomer resulting in a positive prick test. For dimer it was 100-fold or more in 25 out of 29 patients, and for trimer it was 100-fold or superior in 26 out of 29 patients. By intradermal testing, the end-point concentration was 160-fold higher for trimer than for monomer in 24 patients and 40-fold higher in five patients. For the two fragments the end-point concentration was 160-fold higher in 20 out of 22 patients.

CONCLUSION

Genetically modified hypoallergenic derivatives of the major birch pollen allergen, Bet v 1 showed reduced capacity to induce immediate type skin reactions. They may represent candidate molecules for immunotherapy of birch pollen allergy with reduced risk of anaphylactic side-effects.

Comparison of inflammatory responses to genetically engineered hypoallergenic derivatives of the major birch pollen allergen bet v 1 and to recombinant bet v 1 wild type in skin chamber fluids collected from birch pollen-allergic patients

BACKGROUND

Nearly 60% of birch pollen-allergic patients react exclusively to Bet v 1. With use of the skin blister model, previously only established for installation of crude allergens, we have for the first time characterized the inflammatory response in vivo to recombinant birch pollen allergen, rBet v 1, molecules (rBet v 1 wild type, fragments and trimer).

OBJECTIVE

Our purpose was to examine whether challenge with rBet v 1 derivatives (fragments and trimer) compared with rBet v 1 wild type differs with respect to influx of activated eosinophils and detectable levels of cytokines/chemokines related to allergic inflammation in skin chambers applied to birch pollen-allergic patients.

METHODS

The skin blister chambers were filled for 2 hours with rBet v 1, the derivatives or PBS and heparin (negative control). The fluids were analyzed after 2 and 8 hours. The number of eosinophils was determined and EG2 and CD69 expression measured by flow cytometry. Cytokines and mediators were analyzed by ELISA and RIA techniques.

RESULTS

Comparable numbers of eosinophils were recruited to the chambers challenged with rBet v 1 molecules, but the eosinophils from the rBet v 1 wild-type challenged chambers showed a significantly higher expression of CD69. The levels of eotaxin were similar in all 4 chambers, whereas rBet v 1 wild type induced significantly higher levels of histamine, eosinophil cationic protein, and GM-CSF than the derivatives did. Recombinant Bet v 1 trimer elicited significantly lower levels of IL-4 compared with rBet v1 wild type.

CONCLUSION

Genetically engineered hypoallergenic rBet v 1 derivatives recruited eosinophils analogously with rBet v 1 wild type. However, the derivatives exhibited a lower capacity to activate eosinophils and to release proinflammatory mediators and T helper type 2-derived cytokines. The derivatives may therefore be candidate molecules for specific immunotherapy of birch pollen allergy with reduced risk of inducing allergenic or inflammatory side effects.

Expulsion of allergen-containing materials from hydrated rye grass (Lolium perenne) pollen revealed by using immunogold field emission scanning and transmission electron microscopy

BACKGROUND

Several studies demonstrated episodes of grass pollen-induced allergic asthma after heavy rainfalls. It has been hypothesized that these asthma attacks might be due to the release of respirable allergen-bearing particles from pollen cytoplasm.

OBJECTIVE

In this study we investigated the release mechanism of the most potent and frequently recognized grass pollen allergens, group 1 and group 5, from freshly harvested and subsequently hydrated rye grass pollen at the ultrastructural level.

METHODS

Rabbit antisera against purified recombinant group 1 and group 5 allergens were used to investigate, by using field emission scanning and transmission immunogold electron microscopy, the allergen release from rye grass pollen grains into isotonic aqueous solutions or water.

RESULTS

Pollen grains exposed to isotonic aqueous solutions remained intact and released allergens by means of diffusion. However, pollen grains hydrated in distilled water or rainwater expelled starch grains and cytoplasmic debris of respirable size. Group 1 and group 5 allergens were observed on and within these materials.

CONCLUSIONS

Exposure of rye grass pollen to water leads to an expulsion of subcellular allergen-containing pollen components of respirable size. Our ultrastructural data thus support the idea that this release of allergen-containing respirable pollen materials may be a cause of asthma attacks after heavy rainfalls.

Dissociation of allergen-specific IgE and IgA responses in sera and tears of pollen-allergic patients: a study performed with purified recombinant pollen allergens

BACKGROUND

Trees and grass pollen allergens represent potent elicitors of allergic rhinoconjunctivitis and asthma. Little is known regarding the presence of allergen-specific IgA antibodies in sera and tears and their association with IgE responses in patients with allergic conjunctivitis.

OBJECTIVE

The purpose of this study was to compare the specificities of IgE and IgA antibodies in sera and tears of pollen-allergic patients with conjunctivitis by using purified recombinant pollen allergens.

METHODS

Sera and tears collected from 23 pollen-allergic and from 23 nonatopic individuals were analyzed for IgE and IgA reactivity to nitrocellulose-blotted birch and timothy grass pollen extracts. In addition, we determined the specificities of IgE, IgG(1-4), and IgA antibodies with use of a panel of purified recombinant pollen allergens (timothy grass: rPhl p 1, rPhl p 2, rPhl p 5; birch: rBet v 1, rBet v 2) in serum and tear samples by immunoblotting and ELISA. Statistical analyses of data were performed by t test and Mann Whitney U test.

RESULTS

Serum and tears of many of the pollen-allergic individuals with conjunctivitis exhibited specificity for the very same pollen allergens. No allergen-specific IgE antibodies were detected in tears of nonatopic individuals. IgA antibodies in sera and tears of patients with allergic conjunctivitis were mainly directed against nonallergenic moieties and showed specificities that were significantly different from those of IgE antibodies.

CONCLUSION

The dissociation of IgE and IgA responses and the lack of allergen-specific IgA antibodies in mucosal secretions (eg, tears) may contribute to allergic manifestations in target organs of atopy. Induction of allergen-specific IgA antibodies may hence be considered as a promising strategy for the treatment of mucosal forms of atopy.

Molecular characterization of human IgG monoclonal antibodies specific for the major birch pollen allergen Bet v 1. Anti-allergen IgG can enhance the anaphylactic reaction

We report the molecular characterization of five human monoclonal antibodies, BAB1-5 (BAB1: IgG(1); BAB4: IgG(2); BAB2, 3, 5: IgG(4)), with specificity for the major birch pollen allergen, Bet v 1. BAB1-5 were obtained after immunotherapy and contained a high degree of somatic mutations indicative of an antigen-driven affinity maturation process. While BAB1 inhibited the binding of patients IgE to Bet v 1, BAB2 increased IgE recognition of Bet v 1, and, even as Escherichia coli-expressed Fab, augmented Bet v 1-induced immediate type skin reactions. The demonstration that IgG antibodies can enhance allergen-induced allergic reactions is likely to explain the unpredictability of specific immunotherapy.

Molecular, immunological, and structural characterization of Phl p 6, a major allergen and P-particle-associated protein from Timothy grass (Phleum pratense) pollen

Due to the wide distribution and heavy pollen production of grasses, approximately 50% of allergic patients are sensitized against grass pollen allergens. cDNAs coding for two isoforms and four fragments of a major timothy grass (Phleum pratense) pollen allergen, Phl p 6, were isolated by IgE immunoscreening from a pollen expression cDNA library. Recombinant Phl p 6 (rPhl p 6), an acidic protein of 11.8 kDa, was purified to homogeneity as assessed by mass spectrometry and exhibited almost exclusive alpha-helical secondary structure as determined by circular dichroism spectroscopy. Phl p 6 reacted with serum IgE from 75% of grass pollen-allergic patients (n = 171). IgE binding experiments with rPhl p 6 fragments indicated that the N terminus of the allergen is required for IgE recognition. Purified rPhl p 6 elicited dose-dependent basophil histamine release and immediate type skin reactions in patients allergic to grass pollen. A rabbit antiserum raised against purified rPhl p 6 identified it as a pollen-specific protein that, by immunogold electron microscopy, was localized on the polysaccharide-containing wall-precursor bodies (P-particles). The association of Phl p 6 with P-particles may facilitate its intrusion into the deeper airways and thus be responsible for the high prevalence of IgE recognition of Phl p 6. Recombinant native-like Phl p 6 can be used for in vitro as well as in vivo diagnoses of grass pollen allergy, whereas N-terminal deletion mutants with reduced IgE binding capacity may represent candidates for immunotherapy of grass pollen allergy with a low risk of anaphylactic side effects.

Skin test evaluation of genetically engineered hypoallergenic derivatives of the major birch pollen allergen, Bet v 1: results obtained with a mix of two recombinant Bet v 1 fragments and recombinant Bet v 1 trimer in a Swedish population before the birch pollen season

BACKGROUND

More than 95% of birch pollen-allergic subjects react with the major birch pollen allergen, Bet v 1, and almost 60% of them are sensitized exclusively to this allergen.

OBJECTIVE

The aim of this study was to compare the in vivo biologic activity of genetically engineered hypoallergenic derivatives of Bet v 1 (an equimolar mixture of 2 recombinant [r] Bet v 1 fragments and of rBet v 1 trimer) with that of rBet v 1 wild-type by skin prick and intradermal testing.

METHODS

Birch pollen-allergic patients who had not received immunotherapy (n = 23), a group of allergic patients without birch pollen allergy (n = 12), and nonatopic persons (n = 8) from northern Europe (Sweden) underwent skin prick and intradermal testing with different concentrations of the recombinant allergens and commercial birch pollen extract before the birch pollen season. Immediate and late-phase reactions were recorded and allergen-specific IgE and IgG subclass responses were determined by CAP radioallergosorbent test and ELISA, respectively.

RESULTS

Atopic persons without birch pollen allergy and nonatopic individuals did not have skin reactions to rBet v 1 wild-type and genetically engineered hypoallergenic derivatives. By intradermal testing, 8 of 23 and 13 of 23 birch pollen-allergic patients did not react with the highest concentration (1 microg/mL) of the rBet v 1 fragment mix and rBet v 1 trimer, respectively, compared with 1 with rBet v 1 wild type. Likewise, the highest concentration (100 microg/mL) of fragment mix or trimer failed to elicit a positive skin prick test in 18 of 23 and 15 of 23 patients in comparison with 0/23 with the monomer. No late reactions were observed.

CONCLUSION

The recombinant hypoallergenic birch pollen allergens can probably be used for patient-tailored immunotherapy with a reduced risk to induce anaphylactic reactions.

pET-prof, a plasmid for high-level expression of recombinant peptides fused to a birch profilin-derived hexadecapeptide tag: a system for the detection and presentation of recombinant antigens

We have previously identified a birch pollen profilin hexadecapeptide (Bp36/51), which was recognized by a monoclonal antibody (moAb 4A6) with high affinity. Here, we report the construction of a T7 RNA polymerase-driven high-level plasmid expression system, pET-prof, capable of producing proteins and peptides containing the Bp36/51 birch profilin-derived peptide fused to their N-terminus. As examples, the cDNAs coding for two major timothy grass (Phleum pratense) pollen allergens, Phl p 2 and Phl p 6, as well as for an alder (Alnus glutinosa) pollen allergen, Aln g 4, were overexpressed in Escherichia coli as BP36/51-tagged proteins. All three recombinant allergens were readily detected in nitrocellulose-blotted E. coli extracts by the Bp36/51-specific moAb 4A6. We demonstrate comparable IgE recognition of Bp36/51-tagged and untagged recombinant allergens by immunoblotting. A sandwich ELISA was developed using plate-bound moAb 4A6 to immobilize and present Bp36/51-tagged recombinant allergens to IgE antibodies of allergic patients. Using immunoelectronmicroscopy, we demonstrate that even under harsh fixation conditions, tagged allergens can be localized simultaneously in situ by moAb 4A6 and allergen-specific antisera. We suggest the use of the pET-prof system for the high-level expression of Bp36/51-tagged polypeptides that can be rapidly detected in total protein extracts, immunolocalized in situ, immobilized and presented to other antigen-specific antibodies (e.g. IgE), even when they occur in minute concentrations.

An immunoglobulin-like fold in a major plant allergen: the solution structure of Phl p 2 from timothy grass pollen

BACKGROUND

Grass pollen allergens are the most important and widespread elicitors of pollen allergy. One of the major plant allergens which millions of people worldwide are sensitized to is Phl p 2, a small protein from timothy grass pollen. Phl p 2 is representative of the large family of cross-reacting plant allergens classified as group 2/3. Recombinant Phl p 2 has been demonstrated by immunological cross-reactivity studies to be immunologically equivalent to the natural protein.

RESULTS

We have solved the solution structure of recombinant Phl p 2 by means of nuclear magnetic resonance techniques. The three-dimensional structure of Phl p 2 consists of an all-beta fold with nine antiparallel beta strands that form a beta sandwich. The topology is that of an immunoglobulin-like fold with the addition of a C-terminal strand, as found in the C2 domain superfamily. Lack of functional and sequence similarity with these two families, however, suggests an independent evolution of Phl p 2 and other homologous plant allergens.

CONCLUSIONS

Because of the high homology with other plant allergens of groups 1 and 2/3, the structure of Phl p 2 can be used to rationalize some of the immunological properties of the whole family. On the basis of the structure, we suggest possible sites of interaction with IgE antibodies. Knowledge of the Phl p 2 structure may assist the rational structure-based design of synthetic vaccines against grass pollen allergy.