Evaluation of laboratory data by conventional statistics and by three types of neural networks

Sixty-three patients with lung (34 small-cell, 18 squamous, 11 adeno-) carcinomas and 43 patients with benign lung diseases were characterized with seven tumor markers: neuron-specific enolase (NSE); cancer antigens CA 19-9, CA 125, CA 15-3, and CA 50; carcinoembryonic antigen (CEA); and tissue polypeptide antigen. Diagnosis had been established by histological examination after surgery and used for classification. After vector transformation, the tumor marker data were fed into neural networks (NNs) based on three different types of learning algorithms: backpropagation (BP), competitive learning (CL), and Hopfield (H). For comparison, the data were evaluated with multivariate stepwise discriminant analysis (MVSDA). BP-NNs are equal to (NSE, CA 19-9, CEA) or better than (100% correct classification when using all seven markers) MVSDA in assigning the correct diagnosis to the patients. Cross-validation data yielded shrinkage effects ranging from 0% to 12.5%. Quality-control (QC) data were evaluated by traditional QC algorithms and compared with the results obtained by a BP-NN. The results show that the BP-NNs could only partly fulfill the tasks of three QC algorithms regarding the violation of static borders but gave good results with respect to dynamic changes.

Infant milk formulas differ regarding their allergenic activity and induction of T-cell and cytokine responses

Background

Several hydrolyzed cow's milk (CM) formulas are available for avoidance of allergic reactions in CM‐allergic children and for prevention of allergy development in high‐risk infants. Our aim was to compare CM formulas regarding the presence of immunoreactive CM components, IgE reactivity, allergenic activity, ability to induce T‐cell proliferation, and cytokine secretion.

Methods

A blinded analysis of eight CM formulas, one nonhydrolyzed, two partially hydrolyzed (PH), four extensively hydrolyzed (EH), and one amino acid formula, using biochemical techniques and specific antibody probes was conducted. IgE reactivity and allergenic activity of the formulas were tested with sera from CM‐allergic patients (n = 26) in RAST‐based assays and with rat basophils transfected with the human FcεRI, respectively. The induction of T‐cell proliferation and the secretion of cytokines in Peripheral blood mononuclear cell (PBMC) culture from CM allergic patients and nonallergic individuals were assessed.

Results

Immune‐reactive α‐lactalbumin and β‐lactoglobulin were found in the two PH formulas and casein components in one of the EH formulas. One PH formula and the EH formula containing casein components showed remaining IgE reactivity, whereas the other hydrolyzed formulas lacked IgE reactivity. Only two EH formulas and the amino acid formula did not induce T‐cell proliferation and proinflammatory cytokine release. The remaining formulas varied regarding the induction of Th2, Th1, and proinflammatory cytokines.

Conclusion

Our results show that certain CM formulas without allergenic and low proinflammatory properties can be identified and they may also explain different outcomes obtained in clinical studies using CM formulas.

Effects of nasal corticosteroids on boosts of systemic allergen-specific IgE production induced by nasal allergen exposure

Background

Allergen exposure via the respiratory tract and in particular via the nasal mucosa boosts systemic allergen-specific IgE production. Intranasal corticosteroids (INCS) represent a first line treatment of allergic rhinitis but their effects on this boost of allergen-specific IgE production are unclear.

Aim

Here we aimed to determine in a double-blind, placebo-controlled study whether therapeutic doses of an INCS preparation, i.e., nasal fluticasone propionate, have effects on boosts of allergen-specific IgE following nasal allergen exposure.

Methods

Subjects (n = 48) suffering from grass and birch pollen allergy were treated with daily fluticasone propionate or placebo nasal spray for four weeks. After two weeks of treatment, subjects underwent nasal provocation with either birch pollen allergen Bet v 1 or grass pollen allergen Phl p 5. Bet v 1 and Phl p 5-specific IgE, IgG_1–4, IgM and IgA levels were measured in serum samples obtained at the time of provocation and one, two, four, six and eight weeks thereafter.

Results

Nasal allergen provocation induced a median increase to 141.1% of serum IgE levels to allergens used for provocation but not to control allergens 4 weeks after provocation. There were no significant differences regarding the boosts of allergen-specific IgE between INCS- and placebo-treated subjects.

Conclusion

In conclusion, the application of fluticasone propionate had no significant effects on the boosts of systemic allergen-specific IgE production following nasal allergen exposure.

Trial Registration

http://clinicaltrials.gov/ NCT00755066

Hypoallergenic derivatives of Fel d 1 obtained by rational reassembly for allergy vaccination and tolerance induction

BACKGROUND AND OBJECTIVE

The major cat allergen Fel d 1 represents one of the most important respiratory allergens. Aim of this study was to engineer recombinant Fel d 1 derivatives with reduced IgE reactivity and preserved T cell epitopes for vaccination and tolerance induction.

METHODS

Seven recombinant mosaic proteins were generated by reassembly of non-IgE-reactive peptides of Fel d 1 which contained the sequence elements for induction of allergen-specific blocking IgG antibodies and T cell epitopes. Mosaic proteins were expressed in Escherichia coli using codon-optimized synthetic genes and compared with Fel d 1 regarding structural fold by circular dichroism, IgE-binding capacity, activation of allergic patients' basophils and ability to induce allergen-specific blocking IgG antibodies upon immunization.

RESULTS

Although each of the mosaic proteins had lost the alpha-helical fold typical for Fel d 1, a strong reduction in IgE reactivity as well as allergenic activity in basophil activation assays was only obtained for three constructs, two reassembled fragments (Fel d 1 MB, Fel d 1 MC) and a fusion of the latter two (Fel d 1 MF) in which the cysteines of Fel d 1 MC were replaced by serines. Immunization of rabbits with Fel d 1 MB, MC and MF induced high levels of IgG antibodies that inhibited IgE reactivity of cat-allergic patients to Fel d 1 in a comparable manner as IgG induced with the wild-type allergen.

CONCLUSIONS

We report the development of hypoallergenic reassembled Fel d 1 proteins suitable for vaccination and tolerance induction in cat-allergic patients.

Cow's milk allergy: from allergens to new forms of diagnosis, therapy and prevention

The first adverse reactions to cow's milk were already described 2,000 years ago. However, it was only 50 years ago that several groups started with the analysis of cow's milk allergens. Meanwhile the spectrum of allergy eliciting proteins within cow's milk is identified and several cow's milk allergens have been characterized regarding their biochemical properties, fold and IgE binding epitopes. The diagnosis of cow's milk allergy is diverse ranging from fast and cheap in vitro assays to elaborate in vivo assays. Considerable effort was spent to improve the diagnosis from an extract-based into a component resolved concept. There is still no suitable therapy available against cow's milk allergy except avoidance. Therefore research needs to focus on the development of suitable and safe immunotherapies that do not elicit severe side effect.

Characterization of mutants of a highly cross-reactive calcium-binding protein from Brassica pollen for allergen-specific immunotherapy

The major turnip (Brassica rapa) pollen allergen, belongs to a family of calcium-binding proteins (i.e., two EF-hand proteins), which occur as highly cross-reactive allergens in pollen of weeds, grasses and trees. In this study, the IgE binding capacity and allergenic activity of three recombinant allergen variants containing mutations in their calcium-binding sites were analyzed in sensitized patients with the aim to identify the most suitable hypoallergenic molecule for specific immunotherapy. Analysis of the wildtype allergen and the mutants regarding IgE reactivity and activation of basophils in allergic patients indicated that the allergen derivative mutated in both calcium-binding domains had the lowest allergenic activity. Gel filtration and circular dichroism experiments showed that both, the wildtype and the double mutant, occurred as dimers in solution and assumed alpha-helical fold, respectively. However, both fold and thermal stability were considerably reduced in the double mutant. The use of bioinformatic tools for evaluation of the solvent accessibility and charge distribution suggested that the reduced IgE reactivity and different structural properties of the double mutant may be due to a loss of negatively charged amino acids on the surface. Interestingly, immunization of rabbits showed that only the double mutant but not the wildtype allergen induced IgG antibodies which recognized the allergen and blocked binding of allergic patients IgE. Due to the extensive structural similarity and cross-reactivity between calcium-binding pollen allergens the hypoallergenic double mutant may be useful not only for immunotherapy of turnip pollen allergy, but also for the treatment of allergies to other two EF-hand pollen allergens.

Carrier-bound Alt a 1 peptides without allergenic activity for vaccination against Alternaria alternata allergy

BACKGROUND

The mould Alternaria alternata is a major elicitor of allergic asthma. Diagnosis and specific immunotherapy (SIT) of Alternaria allergy are often limited by the insufficient quality of natural mould extracts.

OBJECTIVE

To investigate whether recombinant Alt a 1 can be used for reliable diagnosis of Alternaria alternata allergy and to develop a safe, non-allergenic vaccine for SIT of Alternaria allergy.

METHODS

The qualitative sensitization profile of 80 Alternaria-allergic patients from Austria and Italy was investigated using an allergen micro-array and the amount of Alternaria-specific IgE directed to rAlt a 1 was quantified by ImmunoCAP measurements. Peptides spanning regions of predicted high surface accessibility of Alt a 1 were synthesized and tested for IgE reactivity and allergenic activity, using sera and basophils from allergic patients. Carrier-bound peptides were studied for their ability to induce IgG antibodies in rabbits which recognize Alt a 1 and inhibit allergic patients' IgE reactivity to Alt a 1.

RESULTS

rAlt a 1 allowed diagnosis of Alternaria allergy in all tested patients, bound the vast majority (i.e. >95%) of Alternaria-specific IgE and elicited basophil activation already at a concentration of 0.1 ng/mL. Four non-allergenic peptides were synthesized which, after coupling to the carrier protein keyhole limpet hemocyanin, induced Alt a 1-specific IgG and inhibited allergic patients' IgE binding to Alt a 1.

CONCLUSIONS AND CLINICAL RELEVANCE

rAlt a 1 is a highly allergenic molecule allowing sensitive diagnosis of Alternaria allergy. Carrier-bound non-allergenic Alt a 1 peptides are candidates for safe SIT of Alternaria allergy.

Patients suffering from non-IgE-mediated cow's milk protein intolerance cannot be diagnosed based on IgG subclass or IgA responses to milk allergens

BACKGROUND

Cow's milk is one of the most common causes of food allergy. In two-thirds of patients, adverse symptoms following milk ingestion are caused by IgE-mediated allergic reactions, whereas for one-third, the mechanisms are unknown. Aim of this study was to investigate whether patients suffering from non-IgE-mediated cow's milk protein intolerance can be distinguished from persons without cow's milk protein intolerance based on serological measurement of IgG and IgA specific for purified cow's milk antigens.

METHODS

We determined IgG(1-4) subclass and IgA antibody levels to purified recombinant αS1-casein, αS2-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin in four patient groups by ELISA: Patients with IgE-mediated cow's milk allergy (CMA, n=25), patients with non-IgE-mediated cow's milk protein intolerance (CMPI, n=19), patients with gastrointestinal symptoms not associated with cow's milk ingestion (GI, n=15) and control persons without gastrointestinal problems (C, n=26). Cow's milk-specific IgE levels were determined by ImmunoCAP.

RESULTS

Only CMA patients had IgE antibodies to cow's milk. Cow's milk allergic patients mounted the highest IgG(1) and IgG(4) antibody levels to αS1-casein, αS2-casein, β-casein, κ-casein, and α-lactalbumin. No elevated levels of IgG(4) , IgA, and complement-binding IgG subclasses (IgG(1) , IgG(2) , IgG(3) ) to purified cow's milk allergens were found within the CMPI patients compared to persons without cow's milk protein intolerance (GI and C groups).

CONCLUSION

Cow's milk protein intolerant patients cannot be distinguished from persons without cow's milk protein intolerance on the basis of IgG subclass or IgA reactivity to cow's milk allergens.

Carrier-bound, nonallergenic Ole e 1 peptides for vaccination against olive pollen allergy

BACKGROUND

Trees of the family Oleaceae (olive and ash) are important allergen sources in Mediterranean countries, Northern and Central Europe, and North America. The major olive pollen allergen Ole e 1 represents the majority of allergenic epitopes in olive pollen and cross-reacts with Fra e 1, the major ash pollen allergen.

OBJECTIVE

We sought to develop a safe vaccine for the treatment of Oleaceae pollen allergy.

METHODS

We synthesized 5 peptides ranging from 32 to 36 amino acids, which covered the whole sequence of Ole e 1. The IgE and T-cell reactivity of the peptides was compared with that of Ole e 1 by means of dot blot experiments, as well as ELISA, and in proliferation assays. Rabbits were immunized with non-IgE-reactive, keyhole limpet hemocyanin-coupled peptides or Ole e 1. The reactivity of the IgG antibodies with Ole e 1 and their ability to inhibit IgE binding to nOle e 1 was evaluated by means of ELISA.

RESULTS

Only the C-terminal Ole e 1 peptide showed IgE binding, whereas the other peptides were nonallergenic. Immunization of rabbits with Ole e 1-derived peptides bound to the carrier molecule keyhole limpet hemocyanin induced in rabbits the production of Ole e 1-specific IgG antibodies, which cross-reacted with Fra e 1, and inhibited olive and ash pollen-sensitized patients' IgE binding to Ole e 1.

CONCLUSION

Two non-IgE-binding peptides with low T-cell reactivity from the N-terminus of Ole e 1 were identified that might represent safe vaccine candidates for immunotherapy of Oleaceae pollen allergy.

Altered IgE epitope presentation: A model for hypoallergenic activity revealed for Bet v 1 trimer

In order to reduce side effects in the course of allergen specific immunotherapy hypoallergenic allergen derivatives with reduced IgE reactivity have been made by genetic engineering. In contrast to other recombinant hypoallergenic allergen derivatives which showed reduced IgE reactivity, a recombinant trimer of the major birch pollen allergen Bet v 1 showed reduced allergenic activity despite preserved IgE reactivity. We studied rBet v 1 trimer by SDS-PAGE, mass spectrometry, circular dichroism and gel filtration. Furthermore we investigated IgE and IgG reactivity of the rBet v 1 trimer in solid and liquid phase assays and compared its allergenic activity with that of rBet v 1 wildtype using basophil activation assays. In solid phase immunoassays rBet v 1 trimer exhibited even stronger IgE reactivity than the rBet v 1 wildtype, whereas both proteins were equally well recognized by Bet v 1-specific IgG antibody probes. In fluid phase IgE experiments rBet v 1 trimer inhibited IgE reactivity to rBet v 1 wildtype but showed a more than 10-fold reduced allergenic activity compared to the rBet v 1 monomer. By analytical gel filtration it was demonstrated that, despite its monomeric appearance in SDS-PAGE the trimer occurred in fluid phase in the form of defined high molecular weight (>600 kDa) aggregates whereas rBet v 1 wildtype strictly appeared as monomeric protein. The results indicate that the hypoallergenic nature of the rBet v 1 trimer is due to formation of defined high molecular weight aggregates which may be responsible for an altered presentation of IgE epitopes in a form with reduced capacity to crosslink effector-cell bound IgE. We thus provide evidence for a novel mechanism for hypoallergenic activity.

Microarray and allergenic activity assessment of milk allergens

BACKGROUND

Cow's milk is one of the most common causes of food allergy affecting approximately 2.5% of infants in the first years of their life. However, only limited information regarding the allergenic activity of individual cow's milk allergens is available.

OBJECTIVE

To analyse the frequency of IgE reactivity and to determine the allergenic activity of individual cow's milk allergens.

METHODS

A nitrocellulose-based microarray, based on purified natural and recombinant cow's milk allergens was used to determine IgE reactivity profiles using sera from 78 cow's milk-sensitized individuals of varying ages. The allergenic activity of the individual allergens was tested using patients' sera for loading rat basophil leukaemia cells (RBL) expressing the α-chain of the human receptor FcεRI.

RESULTS

Using the microarray and the RBL assay, cow's milk allergens were assessed for frequency of IgE recognition and allergenic activity. Moreover, the RBL assay allowed distinguishing individuals without or with mild clinical reactions from those with severe systemic or gastrointestinal symptoms as well as persons who grew out cow's milk allergy from those who did not.

CONCLUSIONS

Component-resolved testing using milk allergen microarrays and RBL assays seems to provide useful additional diagnostic information and may represent a basis for future forms of prophylactic and therapeutic strategies for cow's milk allergy.

Hypoallergenic derivatives of the major birch pollen allergen Bet v 1 obtained by rational sequence reassembly

BACKGROUND

At least 100 million patients suffer from birch pollen allergy.

OBJECTIVE

Rational design of recombinant derivatives of the major birch pollen allergen, Bet v 1, characterized by reduced IgE reactivity, preservation of sequences relevant for the induction of allergen-specific blocking IgG, and maintenance of T-cell epitopes for immunotherapy of birch pollen allergy.

METHODS

Three recombinant mosaic proteins derived from Bet v 1 were generated by reassembly of codon-optimized genes coding for Bet v 1 fragments containing the elements for the induction of allergen-specific blocking IgG antibodies and the major T-cell epitopes. The proteins were expressed in Escherichia coli as recombinant mosaic molecules and compared with the Bet v 1 wild-type protein by chemical and structural methods, regarding IgE-binding and IgG-binding capacity, in basophil activation assays and tested for the in vivo induction of IgG responses.

RESULTS

Three recombinant Bet v 1 (rBet v 1) mosaic proteins with strongly reduced IgE reactivity and allergenic activity were expressed and purified. Immunization with the recombinant hypoallergens induced IgG antibodies that inhibited IgE reactivity of patients with allergy to Bet v 1 comparable to those induced with the rBet v 1 wild-type allergen.

CONCLUSION

We report the generation and preclinical characterization of 3 hypoallergenic rBet v 1 derivatives with suitable properties for immunotherapy of birch pollen allergy.

Association of allergic patients' phenotypes with IgE reactivity to recombinant pollen marker allergens

BACKGROUND

During the last decade allergen molecules from several allergen sources have been produced by recombinant DNA technology. The aim of this study was to investigate whether IgE reactivity to recombinant pollen allergens with broad and narrow cross-reactivity is associated with clinical phenotypes of allergic sensitization.

METHODS

Serum IgE reactivity to a panel of six recombinant birch and grass pollen allergens was measured by ELISA in pollen sensitized patients from Central Europe to define groups of patients with exclusive IgE reactivity to rBet v 1, with exclusive reactivity to major grass pollen allergens (rPhl p 1, rPhl p 2, rPhl p 5) and with IgE reactivity to cross-reactive pollen allergens (rBet v 2, rPhl p 7). Patients' clinical phenotypes were recorded. IgE responses to tree, grass and weed pollen as well as plant food extracts were evaluated in vitro by CAP-FEIA and clinical sensitivities were confirmed in vivo by skin prick testing.

RESULTS

IgE reactivity to the recombinant major birch pollen allergen, rBet v 1, was associated with sensitization to pollen from birch, taxonomically related trees and to certain plant-derived food. Reactivity to the recombinant timothy grass pollen allergens, rPhl p 1, rPhl p 2, rPhl p 5, indicated sensitization to pollen from grasses. Patients reacting with the highly cross-reactive allergen rPhl p 7 were polysensitized to pollen from unrelated trees, grasses and weeds and rBet v 2-positive patients were polysensitized to pollen and plant-derived food from unrelated plants.

CONCLUSIONS

IgE reactivity to recombinant marker allergens is associated with clinical phenotypes of allergic sensitization and may be useful for the selection of treatment strategies.

Cloning, expression, and mapping of allergenic determinants of alphaS1-casein, a major cow's milk allergen

Milk is one of the first components introduced into human diet. It also represents one of the first allergen sources, which induces IgE-mediated allergies in childhood ranging from gastrointestinal, skin, and respiratory manifestations to severe life-threatening manifestations, such as anaphylaxis. Here we isolated a cDNA coding for a major cow's milk allergen, alphaS1-casein, from a bovine mammary gland cDNA library with allergic patients' IgE Abs. Recombinant alphaS1-casein was expressed in Escherichia coli, purified, and characterized by circular dichroism as a folded protein. IgE epitopes of alphaS1-casein were determined with recombinant fragments and synthetic peptides spanning the alphaS1-casein sequence using microarrayed components and sera from 66 cow's milk-sensitized patients. The allergenic activity of ralphaS1-casein and the alphaS1-casein-derived peptides was determined using rat basophil leukemia cells transfected with human FcepsilonRI, which had been loaded with the patients' serum IgE. Our results demonstrate that ralphaS1-casein as well as alphaS1-casein-derived peptides exhibit IgE reactivity, but mainly the intact ralphaS1-casein induced strong basophil degranulation. These results suggest that primarily intact alphaS1-casein or larger IgE-reactive portions thereof are responsible for IgE-mediated symptoms of food allergy. Recombinant alphaS1-casein as well as alphaS1-casein-derived peptides may be used in clinical studies to further explore pathomechanisms of food allergy as well as for the development of new diagnostic and therapeutic strategies for milk allergy.

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.

Molecular mimicry in pauci-immune focal necrotizing glomerulonephritis

Pauci-immune focal necrotizing glomerulonephritis (FNGN) is a severe inflammatory disease associated with autoantibodies to neutrophil cytoplasmic antigens (ANCA). Here we characterize autoantibodies to lysosomal membrane protein-2 (LAMP-2) and show that they are a new ANCA subtype present in almost all individuals with FNGN. Consequently, its prevalence is nearly twice that of the classical ANCAs that recognize myeloperoxidase or proteinase-3. Furthermore, antibodies to LAMP-2 cause pauci-immune FNGN when injected into rats, and a monoclonal antibody to human LAMP-2 (H4B4) induces apoptosis of human microvascular endothelium in vitro. The autoantibodies in individuals with pauci-immune FNGN commonly recognize a human LAMP-2 epitope (designated P(41-49)) with 100% homology to the bacterial adhesin FimH, with which they cross-react. Rats immunized with FimH develop pauci-immune FNGN and also develop antibodies to rat and human LAMP-2. Finally, we show that infections with fimbriated pathogens are common before the onset of FNGN. Thus, FimH-triggered autoimmunity to LAMP-2 provides a previously undescribed clinically relevant molecular mechanism for the development of pauci-immune FNGN.

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.

A high-affinity monoclonal anti-IgE antibody for depletion of IgE and IgE-bearing cells

BACKGROUND

We have identified a monoclonal anti-human immunoglobulin E (IgE) antibody, which recognizes FcepsilonRI-bound IgE and prevents binding of IgE to FcepsilonRI. In this study, we assessed the binding kinetics and affinity of monoclonal antibody 12 (mAb12) for IgE and investigated whether mAb12 can be used for depletion of IgE and isolation of IgE-bearing cells from peripheral blood.

METHODS

Binding kinetics and affinity for IgE were studied using Biacore surface plasmon resonance technique experiments. IgE antibodies were depleted from serum using sepharose-coupled mAb12 and IgE-bearing cells were enriched from heparinized blood samples with mAb12. The extent and biological relevance of IgE depletion were studied by quantitative IgE measurements and basophil histamine release experiments. Specific binding of mAb12 to IgE-bearing cells (basophils, mast cells, IgE-secreting plasma cells) was demonstrated by FACS.

RESULTS

Monoclonal antibody 12 shows rapid association (k(a) = 5.46e5/Ms) with IgE, almost no dissociation (k(d) = 8.8e-5/s) and an affinity for IgE (K(D) = 1.61e-10 M), which is as high as that of FcepsilonRI. Immobilized mAb12 could be used to deplete IgE antibodies and isolate IgE-bearing cells from peripheral blood in a single-step procedure.

CONCLUSIONS

Monoclonal antibody 12 is a high affinity anti-human IgE antibody, which efficiently removes IgE and IgE-bearing cells from peripheral blood and may thus be used for extracorporeal depletion of IgE and IgE-bearing cells.

Higher immunoglobulin E antibody levels to recombinant Fel d 1 in cat-allergic children with asthma compared with rhinoconjunctivitis

BACKGROUND

Current diagnosis of allergy and asthma to cat is confirmed using cat dander extract (CDE). We have previously engineered a recombinant major cat allergen, rFel d 1, with properties identical to the natural molecule.

OBJECTIVE

The aim of the study was to evaluate IgE and IgG4 antibodies to rFel d 1 among sera from cat-allergic children and adults suffering from asthma and/or rhinoconjunctivitis (RC) in populations from Sweden and Austria.

METHODS

Cat-allergic children and adults from Sweden (n=27 and 31, respectively) and Austria (n=41 and 41) with RC and/or asthma were selected. Sera were tested for IgE and IgG4 antibodies to CDE and rFel d 1 by CAP, and IgE to rFel d 1 by ELISA. Healthy subjects and non-cat-allergic patients (n=75) were included as controls.

RESULTS

There was a high correlation between IgE responses to rFel d 1 and CDE among the 140 patients (r(s)=0.85, P<0.001); however, measured levels to rFel d 1 were on average 30% higher (P<0.0001). Ninety-eight percent of patients and none of the controls showed IgE to rFel d 1 and there was a threefold increased risk of asthma for half of the children with the highest IgE levels [odds ratio 3.23; 95% confidence interval (CI), 1.19-8.79] by ELISA. IgE responses to rFel d 1 among children with asthma were higher (median 19.4 kU/L) compared with children with RC (median 6.6 kU/L, P<0.05) and adults with asthma (median 3.0 kU/L, P<0.01). Furthermore, children with asthma displayed higher IgG4 levels than the asthmatic adults.

CONCLUSION

A single recombinant molecule, rFel d 1, is at least as sensitive for in vitro diagnostics of cat allergy as the current extract-based test. Elevated IgE antibody levels to Fel d 1 are suggested to be a risk factor for asthma in cat-allergic children.

Different allergenic activity of grass pollen allergens revealed by skin testing

BACKGROUND

Grass pollen is one of the most important allergen sources. The aim of this study was to compare the in vivo allergenic activity of two recently characterized major grass pollen allergens, Phl p 4 and Phl p 13, with three established major grass pollen allergens, Phl p 1, Phl p 2 and Phl p 5 as a basis for the formulation of a grass pollen allergy vaccine based on purified allergens.

MATERIAL AND METHODS

Eighty-two grass pollen allergic patients were skin prick tested with serial dilutions of approximately equimolar concentrations of the purified allergens in a double-blind study.

RESULTS

Phl p 4 and Phl p 13 were identified as major grass pollen allergens according to IgE binding frequency (Phl p 4: 85%; Phl p 13: 56%), but exhibited a five to nine-fold lower allergenic skin reactivity compared to Phl p 1, Phl p 2 or Phl p 5.

CONCLUSION

Our results indicate that Phl p 4 and Phl p 13 are not essential components for a therapeutic grass pollen vaccine and underpin the importance of evaluating the in vivo allergenic activity of individual allergens for the formulation of therapeutic vaccines based on purified allergens.

The IgE-reactive autoantigen Hom s 2 induces damage of respiratory epithelial cells and keratinocytes via induction of IFN-gamma

Hom s 2, the alpha-chain of the nascent polypeptide-associated complex, is an intracellular autoantigen that has been identified with IgE autoantibodies from atopic dermatitis patients. We investigated the humoral and cellular immune response to purified recombinant Hom s 2 (rHom s 2). rHom s 2 exhibited IgE reactivity comparable to exogenous allergens, but did not induce relevant basophil cell degranulation. The latter may be attributed to the fact that patients recognized single epitopes on Hom s 2 as revealed by IgE epitope mapping with rHom s 2 fragments. In contrast to exogenous allergens, rHom s 2 had the intrinsic ability to induce the release of IFN-gamma in cultured peripheral blood mononuclear cells from atopic as well as non-atopic individuals. IFN-gamma-containing culture supernatants from Hom s 2-stimulated peripheral blood mononuclear cells caused disintegration of respiratory epithelial cell layers and apoptosis of skin keratinocytes, which could be inhibited with a neutralizing anti-IFN-gamma antibody. Our data demonstrate that the Hom s 2 autoantigen can cause IFN-gamma-mediated cell damage.

Sensitization to human milk

BACKGROUND

Allergy to milk is one of the earliest manifestations of IgE-mediated allergies and affects about 2.5% of newborn children. Several reports indicate that milk-allergic patients may be sensitized also to human milk proteins.

OBJECTIVE

To analyse the specificity and possible biological relevance of IgE reactivity to human milk antigens in milk-allergic patients.

METHODS

The specificity of IgE reactivity to cow's milk and human milk antigens was analysed with sera from milk-allergic children and adults by IgE immunoblotting. IgE cross-reactivity between milk antigens was studied by immunoblot inhibition experiments. That IgE reactivity to human milk antigens is not due to alloreactivity or due to the transmission of foreign antigens into mother's milk was demonstrated through the analysis of milk samples from genetically unrelated mothers before and after intake of dietary milk products. The biological relevance of IgE reactivity to human milk was confirmed by skin testing. Results IgE antibodies to human milk were found in more than 80% of the tested milk-allergic patients. Cross-reactive IgE-reactive human antigens such as alpha-lactalbumin and non-cross-reactive human milk antigens were identified. Immediate-type skin reactions could be elicited with human milk samples in patients with IgE reactivity to human milk.

CONCLUSION

IgE reactivity to human milk in milk-allergic patients can be due to cross- sensitization and genuine sensitization to human milk and may cause allergic symptoms. IgE-mediated sensitization to human milk is common in milk-allergic patients and may require diagnostic testing and monitoring.

Mast cell-derived proteases control allergic inflammation through cleavage of IgE

BACKGROUND

Cross-linking of mast cell-bound IgE releases proinflammatory mediators, cytokines, and proteolytic enzymes and is a key event in allergic inflammation.

OBJECTIVE

We sought to study the effect of proteases released on effector cell activation on receptor-bound IgE and their possible role in the regulation of allergic inflammation.

METHODS

Using molar ratios of purified recombinant tryptase and human IgE, we studied whether tryptase can cleave IgE. Similar experiments were performed with mast cell lysates in the presence or absence of protease inhibitors. IgE cleavage products were detected in supernatants of allergen cross-linked, cultivated mast cells and in tissue fluids collected from patients' skin after IgE-mediated degranulation. The effects of protamine, an inhibitor of heparin-dependent proteases on IgE-mediated allergic in vivo skin inflammation in human subjects were studied.

RESULTS

We show that beta-tryptase, a major protease released during mast cell activation, cleaves IgE. IgE degradation products were detected in tryptase-containing tissue fluids collected from sites of allergic inflammation. The biologic significance of this mechanism is demonstrated by in vivo experiments showing that protease inhibition enhances allergic skin inflammation.

CONCLUSION

We suggest that IgE cleavage by effector cell proteases is a natural mechanism for controlling allergic inflammation.

Detection of an allergen in dog dander that cross-reacts with the major cat allergen, Fel d 1

BACKGROUND

A considerable proportion of animal-allergic patients are sensitized to both cat and dog allergens but knowledge about cross-reactive allergens in cat and dog dander is limited.

OBJECTIVE

To investigate whether dog dander contains an allergen that cross-reacts with the major cat allergen, Fel d 1.

METHODS

Recombinant Fel d 1 with the same immunological properties as natural Fel d 1 was used for quantitative (CAP) IgE competition experiments performed with sera obtained from cat-allergic patients (n=36). A Fel d 1 cross-reactive dog allergen was characterized by one- and two-dimensional immunoblotting using rFel d 1 for IgE inhibition experiments and with monospecific, polyclonal rabbit anti-recombinant Fel d 1 antibodies.

RESULTS

In 25% of Fel d 1-reactive cat-allergic patients, more than 50% inhibition of IgE reactivity to dog allergens was achieved with recombinant Fel d 1. An Fel d 1 cross-reactive 20 kDa allergen with a pI of approximately 3.4 was detected in dander extracts of several different dog breeds.

CONCLUSION

This is the first report demonstrating the presence of an Fel d 1-like allergen in dog dander extracts, which may be responsible for double positivity to cat and dog in serology. However, the clinical relevance of this cross-sensitization needs to be confirmed. These results are important for the diagnostic and therapeutic use of dog dander allergen extracts.

A recombinant hypoallergenic parvalbumin mutant for immunotherapy of IgE-mediated fish allergy

IgE-mediated allergy to fish is a frequent cause of severe anaphylactic reactions. Parvalbumin, a small calcium-binding protein, is the major fish allergen. We have recently isolated a cDNA coding for carp parvalbumin, Cyp c 1, and expressed in Escherichia coli a recombinant Cyp c 1 molecule, which contained most IgE epitopes of saltwater and freshwater fish. In this study, we introduced mutations into the calcium-binding domains of carp parvalbumin by site-directed mutagenesis and produced in E. coli three parvalbumin mutants containing amino acid exchanges either in one (single mutants; Mut-CD and Mut-EF) or in both of the calcium-binding sites (double mutant; Mut-CD/EF). Circular dichroism analyses of the purified derivatives and the wild-type allergen showed that Mut-CD/EF exhibited the greatest reduction of overall protein fold. Dot blot assays and immunoblot inhibition experiments performed with sera from 21 fish-allergic patients showed that Mut-CD/EF had a 95% reduced IgE reactivity and represented the derivative with the least allergenic activity. The latter was confirmed by in vitro basophil histamine release assays and in vivo skin prick testing. The potential applicability for immunotherapy of Mut-CD/EF was demonstrated by the fact that mouse IgG Abs could be raised by immunization with the mutated molecule, which cross-reacted with parvalbumins from various fish species and inhibited the binding of fish-allergic patients' IgE to the wild-type allergen. Using the hypoallergenic carp parvalbumin mutant Mut-CD/EF, it may be possible to treat fish allergy by immunotherapy.

Exposure to a farming environment has allergen-specific protective effects on TH2-dependent isotype switching in response to common inhalants

BACKGROUND

IgE synthesis by human B cells results from allergen-dependent, T(H)2-mediated isotype switching. Exposure to a farming environment protects against IgE responses.

OBJECTIVE

We reconstructed allergen-dependent switching patterns in vivo to identify the level or levels at which farm exposure acts to protect against atopy.

METHODS

Serum IgG1 to IgG4 and IgE to grass (rPhl p 1 and rPhl p 5), cat (rFel d 1), and mite (rDer p 2) were assessed by means of ELISA in the Allergy and Endotoxin study population (812 children). Farm exposure was defined as currently living on a farm, exposure to stables/farm milk in the first year of life, or both.

RESULTS

Farm exposure did not affect allergen-specific IgG2 and IgG3 levels but had complex allergen-specific effects on IgG1, IgG4, and IgE levels. Exposure protected against grass-specific responses at every step along the IgG1/IgG4/IgE switching pathway but had no significant effect on mite responses. Protection from cat responses was concentrated at the IgG1 level. For all allergens, failure to express IgG1 was associated with low prevalence of IgG4 or IgE responses. Notably, coexpression of IgG1, IgG4, and IgE to grass was associated with increased risk of allergic disease and higher IgE levels compared with production of IgG1 and IgE without IgG4, suggesting IgG4 coexpression marks stronger activation of T(H)2-dependent events.

CONCLUSION

The protective effects of farm exposure were confined to T(H)2-dependent IgG1, IgG4, and IgE expression and were allergen and switch stage specific, suggesting that distinct mechanisms regulate individual steps within allergen-induced class switching in vivo.

CLINICAL IMPLICATIONS

Environmental interventions to prevent IgE expression might need to be tailored to specific allergens.

Antigens drive memory IgE responses in human allergy via the nasal mucosa

BACKGROUND

Natural allergen contact induces an increase of IgE levels and sensitivity but the mechanisms underlying the allergen-specific memory responses are poorly understood. Furthermore, it has not been studied whether allergen exposure affects the molecular reactivity profiles in patients. The aim of this study was to analyze the influence of nasal allergen encounter on the molecular profile and magnitude of memory IgE responses and on systemic sensitivity.

METHODS

We investigated allergen-specific IgE, IgG subclass and IgM responses to defined allergen molecules (grass pollen: Phl p 1, Phl p 2 and Phl p 5; birch pollen: Bet v 1 and Bet v 2) in allergic patients in response to natural as well as to controlled nasal and dermal allergen exposure. Changes in systemic sensitivity were monitored by skin prick testing and by basophil histamine release experiments.

RESULTS

Respiratory antigen exposure boosted IgE levels to a pre-established profile of allergen molecules without inducing significant IgM responses or new IgE specificities in allergic individuals. The importance of the route of allergen contact is demonstrated by an increase of systemic IgE levels and sensitivity after nasal exposure. In vitro sensitisation of basophils with pre- and post-seasonal serum samples suggests an allergen-induced elevation of specific IgE as a cause for the increased allergen-specific sensitivity.

CONCLUSION

The characteristics of the allergen-driven antibody responses indicate a direct activation of an established pool of IgE memory cells with defined specificities as an underlying mechanism. Our finding that nasal allergen contact is a major factor for the boosting of memory IgE and systemic sensitivity may open new therapeutic possibilities.

The major allergen of olive pollen Ole e 1 is a diagnostic marker for sensitization to Oleaceae

BACKGROUND

Trees of the family Oleaceae are important allergen sources, with a strongly varying geographic distribution. For example, olive pollen is an important allergen source in Mediterranean countries, whereas ash pollen dominates in Northern and Central Europe and North America. The aim of this study was to compare the profiles of olive and ash pollen allergens and to study the degree of cross-reactivity using populations of allergic patients selectively exposed to olive or ash pollen.

METHODS

Olive and ash pollen extracts were analyzed by IgE immunoblotting using sera from Spanish patients highly exposed to olive pollen and Austrian patients without olive but ash pollen exposure. IgE cross-reactivity was studied by qualitative immunoblot inhibition assays and semiquantitative ELISA inhibitions using olive, ash, birch, mugwort, timothy grass pollen extracts and the major olive pollen allergen, Ole e 1.

RESULTS

Spanish and Austrian patients exhibited an almost identical IgE-binding profile to olive and ash pollen allergens, with major reactivity directed against Ole e 1, and its homologous ash counterpart, Fra e 1. IgE inhibition experiments demonstrated extensive cross-reactivity between olive and ash pollen allergens. However, whereas cross-reactions between profilins and calcium-binding allergens also occurred between unrelated plant species, cross-reactivity to Ole e 1 was confined to plants belonging to the Oleaceae.

CONCLUSIONS

Ole e 1 is a marker allergen for the diagnosis of olive and ash pollen allergy.

Allergy testing: the role of recombinant allergens

Currently, diagnosis of type I allergy is performed using crude allergen extracts, which allow the identification of the allergen-containing source responsible for type I allergic symptoms (e.g., allergic rhino-conjunctivitis, asthma) but not the disease-eliciting molecules. With the introduction of recombinant allergens produced by molecular biology techniques, a large panel of allergenic molecules has become available. The application of these recombinant allergens for in vitro tests has led to new forms of component-resolved diagnosis (CRD) and allows the establishment of a patient's individual reactivity profile. The increasing number of recombinant allergens characterized during the last decade has allowed the development of chip-based allergy tests for simultaneous detection of up to 5000 different allergens and epitopes. The introduction of these recombinant allergen-based tests into clinical practice improves the selection of patients for traditional specific immunotherapy and allows monitoring of the immunological efficacy of specific immunotherapy by measuring allergen-specific IgG antibodies. Besides their diagnostic application, recombinant allergens and hypoallergenic derivatives thereof have also been used as vaccines in clinical trials, and recent results have shown their usefulness for the treatment of type I allergy.

Allergen cleavage by effector cell-derived proteases regulates allergic inflammation

The key event of allergic inflammation, allergen-induced crosslinking of mast cell-bound IgE antibodies, is accompanied by release of inflammatory mediators, cytokines, and proteases, in particular beta-tryptase. We provide evidence that protease-mediated cleavage of allergens represents a mechanism that regulates allergen-induced mast cell activation. When used in molar ratios as they occur in vivo, purified beta-tryptase cleaved major grass and birch pollen allergens, resulting in defined peptide fragments as mapped by mass spectrometry. Tryptase-cleaved allergens showed reduced IgE reactivity and allergenic activity. The biological relevance is demonstrated by the fact that lysates from activated human mast cells containing tryptase levels as they occur in vivo cleaved allergens. Additionally, protamine, an inhibitor of heparin-dependent effector cell proteases, augmented allergen-induced release of mediators from effector cells. Protease-mediated allergen cleavage may represent an important mechanism for terminating allergen-induced effector cell activation.

Influence of clinical factors on the haemolysis marker haptoglobin

BACKGROUND

Plasma haptoglobin determination is clinically used as parameter for haemolysis. To date, however, the influence of the mode of haemolysis (extravascular vs. intravascular) and of nonhaemolytic conditions on haptoglobin concentration and its reliability as a haemolysis marker remain poorly defined.

MATERIALS AND METHODS

In a total of 479 individuals, the influence of haemolytic and nonhaemolytic conditions on plasma haptoglobin levels was investigated.

RESULTS

All studied types of haemolytic disease (n = 16) were associated with markedly decreased plasma haptoglobin levels, without significant differences between intravascular vs. predominantly extravascular haemolysis. Diminished haptoglobin values were also observed in patients with liver cirrhosis, which normalized after liver transplantation. In contrast, markedly increased haptoglobin levels were found in patients with inflammation. In patients with haemolysis and a concomitant acute-phase response, however, haemolysis-dependent haptoglobin depletion was not attenuated. Interestingly, patients with a strongly positive direct antiglobulin test or high cold agglutinin titre but no further evidence for haemolysis had normal haptoglobin values. Likewise, anaemia owing to bone marrow failure, acute gastrointestinal or chronic diffuse blood loss, and end-stage kidney disease were associated with normal haptoglobin levels.

CONCLUSIONS

Plasma haptoglobin depletion is a reliable marker for the instant diagnosis of accelerated red cell destruction irrespective of the site of haemolysis or the presence of inflammation. The capacity of this parameter to predict haemolysis appears to be limited in patients with liver cirrhosis and decreased haptoglobin production only.

Mimotopes identify conformational epitopes on parvalbumin, the major fish allergen

Parvalbumin, the major fish allergen, is recognized by allergen-specific IgE of more than 90% of all fish-allergic patients. A detailed knowledge of allergenic structures is crucial for developing a vaccine inducing blocking antibodies specifically directed towards the IgE binding epitopes. In the present study we aimed to use the phage display technique to generate mimotopes, which mimic epitopes on parvalbumin. Parvalbumin-specific IgE was purified from sera of fish-allergic patients and used for screening of a constrained decamer phage library. After four rounds of biopanning using parvalbumin-specific IgE, five phage clones were selected which were specifically recognized by parvalbumin-specific IgE as well as IgG. DNA sequencing and peptide alignment revealed a high degree of sequence similarities between the mimotopes. Interestingly, on the surface of natural parvalbumin three regions could be defined by computational mimotope matching. In accordance, previously defined allergenic peptides of cod parvalbumin highlighted areas in close proximity or overlapping with the mimotope matching sites. From the presented data we conclude that our approach identified conformational epitopes of parvalbumin relevant for IgE and IgG binding. We suggest that these mimotopes are suitable candidates for an epitope-specific immunotherapy of fish-allergic patients.

Hom s 4, an IgE-Reactive Autoantigen Belonging to a New Subfamily of Calcium-Binding Proteins, Can Induce Th Cell Type 1-Mediated Autoreactivity

Skin inflammation in atopic dermatitis starts with Th2 and IgE-mediated responses against exogenous allergens and, for unknown reasons, resembles features of a Th1-driven reaction in the chronic stages. We report the characterization of a human protein, Hom s 4, recognized by IgE autoantibodies from atopic dermatitis patients. The complete Hom s 4 cDNA codes for a 54-kDa basic protein containing two typical calcium-binding domains separated by an unusually long alpha-helical domain. Therefore, Hom s 4 and homologous proteins found by sequence comparison in mice, fruit flies, and nematodes constitute a novel subfamily of calcium-binding proteins. Using Hom s 4-specific Abs, it is demonstrated that the protein is strongly expressed within epidermal keratinocytes and dermal endothelial cells. Purified Hom s 4 showed IgE cross-reactivity with exogenous calcium-binding allergens from plants and fish but, in contrast to the exogenous allergens, induced only weak histamine release from patient basophils. However, the analysis of Hom s 4-specific cytokine and humoral immune responses indicated that Hom s 4 strongly induces Th1 responses which are accompanied by the release of IFN-gamma, a cytokine implicated in epithelial cell damage. Hom s 4-induced IFN-gamma production was found in normal individuals, in patients with chronic inflammatory skin diseases and in Th2-prone atopic persons, suggesting that Hom s 4 represents a protein with an intrinsic property to induce Th1-mediated autoreactivity. It may thus contribute to chronic skin inflammation in atopic as well as in nonatopic persons.

Affinity determinations of purified IgE and IgG antibodies against the major pollen allergens Phl p 5a and Bet v 1a: discrepancy between IgE and IgG binding strength

Allergen-specific IgE and IgG antibodies coexist in allergic individuals, but only IgE has anaphylactogenic capacity. This study aimed to determine the association, dissociation and equilibrium constants for the interaction of allergen-specific IgE and IgG with the major grass and birch pollen allergens Phl p 5a and Bet v 1a. We isolated specific IgE and IgG antibodies from pollen allergic patients' sera by a two-step affinity chromatography protocol and controlled the high purity in a recombinant allergen chip microarray. Surface plasmon resonance measurements of polyclonal IgE and IgG species revealed that their affinities diverge widely, being in the range of 10(-10) and 10(-11) M for IgE, but only 10(-6)-10(-7) M for IgG. Moreover, murine monoclonal IgG1 antibodies against the allergens showed affinities of 10(-7)-10(-8) M. Thus, we conclude from our data that even stringently affinity matured IgG cannot score the superior affinity of IgE antibodies to allergens.

Mapping of conformational IgE epitopes on Phl p 5a by using mimotopes from a phage display library

BACKGROUND

Phl p 5 represents a major allergen of timothy grass pollen (Phleum pratense). Detailed knowledge about the structures responsible for IgE binding would allow the design of a novel generation of allergy vaccines.

OBJECTIVE

We aimed to characterize the IgE epitopes of Phl p 5a using phage display combined with a molecular modeling approach.

METHODS

Phl p 5a-specific IgE from sera of patients with grass pollen allergy was used for screening of a random peptide phage library displaying constrained decamers.

RESULTS

Fifteen phage clones that shared sequence motifs and could be grouped into families were selected by using Phl p 5a-specific IgE. Peptide alignment with the solvent-accessible amino acids of Phl p 5a revealed 3 sequence sections with frequent hits of identical or similar amino acids. On the surface of Phl p 5a, these sections assembled in compact patches, most likely representing conformational IgE epitopes, whereas no matching clusters were found on the back sides of the 2 Phl p 5a halves. In surface plasmon resonance experiments, the high-affinity interaction between IgE and Phl p 5 could be competed by phage-displayed peptides up to 24%, indicating that they represent true epitope mimics (ie, mimotopes). Allergen-specific immunogenicity of the mimotopes was proved in Biozzi mice.

CONCLUSION

The selected mimotopes facilitated the localization of conformational IgE epitopes of Phl p 5. We suggest them to be suitable candidates for the development of an epitope-specific immunotherapy.

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.

Molecular Characterization of Polygalacturonases as Grass Pollen-Specific Marker Allergens: Expulsion from Pollen via Submicronic Respirable Particles

Grass pollen belong to the most important allergen sources involved in the elicitation of allergic asthma. We have isolated cDNAs coding for Bermuda grass (Cynodon dactylon) and timothy grass (Phleum pratense) pollen allergens, belonging to a family of pectin-degrading enzymes (i.e., polygalacturonases). The corresponding allergens, termed Cyn d 13 and Phl p 13, represent glycoproteins of approximately 42 kDa and isoelectric points of 7.5. rPhl p 13 was expressed in Escherichia coli and purified to homogeneity. Immunogold electron microscopy using rabbit anti-rPhl p 13 Abs demonstrated that in dry pollen group 13, allergens represent primarily intracellular proteins, whereas exposure of pollen to rainwater caused a massive release of cytoplasmic material containing submicronic particles of respirable size, which were coated with group 13 allergens. The latter may explain respiratory sensitization to group 13 allergens and represents a possible pathomechanism in the induction of asthma attacks after heavy rainfalls. rPhl p 13 was recognized by 36% of grass pollen allergic patients, showed IgE binding capacity comparable to natural Phl p 13, and induced specific and dose-dependent basophil histamine release. Epitope mapping studies localized major IgE epitopes to the C terminus of the molecule outside the highly conserved functional polygalacturonase domains. The latter result explains why rPhl p 13 contains grass pollen-specific IgE epitopes and may be used to diagnose genuine sensitization to grass pollen. Our finding that rabbit anti-rPhl p 13 Abs blocked patients' IgE binding to the allergen suggests that rPhl p 13 may be used for immunotherapy of sensitized patients.

Microarrayed allergens for IgE profiling

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

Characterization of recombinant cat albumin

BACKGROUND

Indoor allergens derived from animals and mites often contribute to exacerbation of skin manifestations in atopic dermatitis (AD) patients.

OBJECTIVE

To produce and characterize recombinant cat albumin, a cross-reactive animal allergen.

METHODS

A complete cDNA coding for cat albumin was obtained by RT-PCR amplification from cat liver RNA. Recombinant cat albumin was expressed in Escherichia coli as hexahistidine-tagged protein, purified by nickel affinity chromatography and studied for IgE reactivity with sera from cat-allergic patients by ELISA and immunoblotting. Furthermore, CD203c expression of basophils from cat-allergic patients upon exposure to recombinant cat albumin was analysed.

RESULTS

Recombinant cat albumin, a cross-reactive animal allergen sharing most IgE epitopes with its natural counterpart, was produced in E. coli. It was recognized preferentially by IgE from AD patients and elicited IgE-dependent basophil activation in sensitized patients.

CONCLUSIONS

Recombinant cat albumin may be used as a paradigmatic tool to analyse mechanisms of allergen-triggered exacerbation of AD, for diagnostic and, perhaps for therapeutic purposes.

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

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

Antacid medication inhibits digestion of dietary proteins and causes food allergy A fish allergy model in balb/c mice

BACKGROUND

Digestible proteins were supposed to be irrelevant for oral sensitization and induction of food allergy. Approximately 10% of the adult population uses antacids for the treatment of dyspeptic disorders, drugs that hinder peptic digestion. In these patients, proteins that are normally degradable might act as food allergens.

OBJECTIVE

We aimed to study the influence of antacid intake on the allergenicity of dietary proteins, taking sturgeon caviar and parvalbumin, the major fish allergen, as examples.

METHODS

Caviar proteins and recombinant parvalbumin from carp, rCyp c 1, were applied for intragastric feedings with or without the antacids sucralfate, ranitidine or omeprazole, using a Balb/c mouse model.

RESULTS

Both caviar proteins and parvalbumin were rapidly degraded in an in vitro digestion assay at pH 2.0, but not at pH 5.0, imitating the effect of antacids. The groups fed with caviar in combination with ranitidine hydrochloride intramuscularly or sucralfate orally had significant levels of caviar-specific IgE antibodies (P <.01), T-cell reactivity, and elevated counts of gastrointestinal eosinophils and mast cells. Food allergy in these groups was further evidenced by oral provocation tests and positive immediate-type skin reactivity. In contrast, feedings with caviar alone led to antigen-specific T-cell tolerance. None of the groups showed immune reactivity against the daily mouse diet. As a proof of the principle, feeding mice with parvalbumin in combination with ranitidine or omeprazole intramuscularly induced allergen-specific IgE antibodies (P <.05).

CONCLUSIONS

When antacid medication impairs the gastric digestion, IgE synthesis toward novel dietary proteins is promoted, leading to food allergy.

Identification of cross-reactive and genuine Parietaria judaica pollen allergens

BACKGROUND

The weed Parietaria judaica is one of the most important pollen allergen sources in the Mediterranean area.

OBJECTIVE

We sought to identify P judaica pollen allergen, which might be used to serologically distinguish genuine Parietaria sensitization and cross-reactivity to allergens from other weed species (eg, mugwort and ragweed).

METHODS

The allergen profile of P judaica IgE-reactive sera from weed pollen-sensitized allergic individuals from the Mediterranean region (n = 36) with high Parietaria pollen exposure and from weed pollen-allergic patients with little or no Parietaria exposure (Austria, n = 42; Scandinavia, n = 8; United States, n = 19) was established by CAP FEIA measurements and by IgE immunoblot inhibition experiments with recombinant allergens.

RESULTS

The majority (83%) of the Mediterranean weed pollen-allergic patients mounted high IgE antibody levels (mean specific IgE, 20.89 kUA/L) against recombinant (r) Par j 2, whereas only 7% of the non-Mediterranean weed-allergic patients showed low IgE reactivity to rPar j 2 (mean specific IgE, 1.03 kUA/L). The cytoskeletal protein profilin and a 2-EF-hand calcium-binding allergen were identified as cross-reactive Parietaria allergens, which were recognized preferentially by Parietaria -positive, non-Mediterranean weed pollen-allergic patients.

CONCLUSION

rPar j 2 might be used as a diagnostic marker allergen to identify weed pollen-allergic patients who are genuinely sensitized against Parietaria pollen and thus would be particularly suited for specific immunotherapy with Parietaria pollen extract.