Induction of IgE antibodies with predefined specificity in rhesus monkeys with recombinant birch pollen allergens, Bet v 1 and Bet v 2

Animals in Respiratory Research

The respiratory barrier, a thin epithelial barrier that separates the interior of the human body from the environment, is easily damaged by toxicants, and chronic respiratory diseases are common. It also allows the permeation of drugs for topical treatment. Animal experimentation is used to train medical technicians, evaluate toxicants, and develop inhaled formulations. Species differences in the architecture of the respiratory tract explain why some species are better at predicting human toxicity than others. Some species are useful as disease models. This review describes the anatomical differences between the human and mammalian lungs and lists the characteristics of currently used mammalian models for the most relevant chronic respiratory diseases (asthma, chronic obstructive pulmonary disease, cystic fibrosis, pulmonary hypertension, pulmonary fibrosis, and tuberculosis). The generation of animal models is not easy because they do not develop these diseases spontaneously. Mouse models are common, but other species are more appropriate for some diseases. Zebrafish and fruit flies can help study immunological aspects. It is expected that combinations of in silico, in vitro, and in vivo (mammalian and invertebrate) models will be used in the future for drug development.

Asthma: The Use of Animal Models and Their Translational Utility

Asthma is characterized by chronic lower airway inflammation that results in airway remodeling, which can lead to a permanent decrease in lung function. The pathophysiology driving the development of asthma is complex and heterogenous. Animal models have been and continue to be essential for the discovery of molecular pathways driving the pathophysiology of asthma and novel therapeutic approaches. Animal models of asthma may be induced or naturally occurring. Species used to study asthma include mouse, rat, guinea pig, cat, dog, sheep, horse, and nonhuman primate. Some of the aspects to consider when evaluating any of these asthma models are cost, labor, reagent availability, regulatory burden, relevance to natural disease in humans, type of lower airway inflammation, biological samples available for testing, and ultimately whether the model can answer the research question(s). This review aims to discuss the animal models most available for asthma investigation, with an emphasis on describing the inciting antigen/allergen, inflammatory response induced, and its translation to human asthma.

Use of nonhuman primates in obstructive lung disease research - is it required?

In times of increasing costs for health insurances, obstructive lung diseases are a burden for both the patients and the economy. Pulmonary symptoms of asthma and chronic obstructive pulmonary disease (COPD) are similar; nevertheless, the diseases differ in pathophysiology and therapeutic approaches. Novel therapeutics are continuously developed, and nonhuman primates (NHPs) provide valuable models for investigating novel biologicals regarding efficacy and safety.

This review discusses the role of nonhuman primate models for drug development in asthma and COPD and investigates whether alternative methods are able to prevent animal experiments.

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

Comparative reactivity of human IgE to cynomolgus monkey and human effector cells and effects on IgE effector cell potency

BACKGROUND

Due to genetic similarities with humans, primates of the macaque genus such as the cynomolgus monkey are often chosen as models for toxicology studies of antibody therapies. IgE therapeutics in development depend upon engagement with the FcεRI and FcεRII receptors on immune effector cells for their function. Only limited knowledge of the primate IgE immune system is available to inform the choice of models for mechanistic and safety evaluations.

METHODS

The recognition of human IgE by peripheral blood lymphocytes from cynomolgus monkey and man was compared. We used effector cells from each species in ex vivo affinity, dose-response, antibody-receptor dissociation and potency assays.

RESULTS

We report cross-reactivity of human IgE Fc with cynomolgus monkey cells, and comparable binding kinetics to peripheral blood lymphocytes from both species. In competition and dissociation assays, however, human IgE dissociated faster from cynomolgus monkey compared with human effector cells. Differences in association and dissociation kinetics were reflected in effector cell potency assays of IgE-mediated target cell killing, with higher concentrations of human IgE needed to elicit effector response in the cynomolgus monkey system. Additionally, human IgE binding on immune effector cells yielded significantly different cytokine release profiles in each species.

CONCLUSION

These data suggest that human IgE binds with different characteristics to human and cynomolgus monkey IgE effector cells. This is likely to affect the potency of IgE effector functions in these two species, and so has relevance for the selection of biologically-relevant model systems when designing pre-clinical toxicology and functional studies.

Anaphylaxis after accidental ingestion of kiwi fruit

Numerous cases of anaphylaxis after ingestion of kiwi fruit, after the skin tests and during oral immunotherapy were described. The article describes the case of severe anaphylactic reaction that occurred in a 55-year-old patient after accidental ingestion of kiwi. Allergy to kiwi fruit was confirmed by a native test with fresh kiwi fruit. After the test, the patient experienced generalized organ response in the form of headache, general weakness and rashes on the neck and breast, and dyspnea. The patient had significantly elevated levels of total IgE and IgE specific to kiwi fruit.

Recombinant marker allergens in diagnosis of patients with allergic rhinoconjunctivitis to tree and grass pollens

BACKGROUND

The aim of this study was to investigate recombinant marker allergens in patients with allergic rhinoconjunctivitis to tree and grass pollens.

METHODS

Sera of 260 tree pollen- and 282 grass pollen-allergic patients were analyzed. Bet v 1 and Phl p 1/p 5 were used as marker allergens for allergies to pollen from birch and grasses. Profilin (Bet v 2 and Phl p 12) and calcium-binding protein (Bet v 4 and Phl p 7) were used as markers for polysensitization.

RESULTS

Two hundred thirty-nine (92%) patients tested positive for IgE anti-Bet v 1. All of them were positive for IgE antibodies against natural birch extract (t3), hazel (t4), and alder (t2). Bet v 1 in combination with t3 identified allergies from related trees with a sensitivity of 99.2%. Two hundred fifty-six patients (91%) tested positive for IgE anti-Phl p 1 and/or anti-Phl p 5. All of them were positive for IgE antibodies against natural timothy (g6) and rye (g12) extract. Phl p 1/p 5 and natural timothy extract identified allergies from grasses and rye with a sensitivity of 99.3%. All Patients reacting to the cross-reactive allergens Bet v 2, Phl p 12, Bet v 4, and Phl p 7 were polysensitized.

CONCLUSION

Bet v 1 in combination with natural birch pollen extract identifies allergies from related trees with a sensitivity of 99.2%. Phl p 1, Phl p 5, and natural timothy extract identifies allergies from grasses and rye in 99.3%. Reactivity to the allergens Bet v 2, Phl p 12, Bet v 4, and Phl p 7 identifies polysensitization and cross-reactivity.

Recombinant allergens for allergen-specific immunotherapy: 10 years anniversary of immunotherapy with recombinant allergens

The broad applicability of allergen-specific immunotherapy for the treatment and eventually prevention of IgE-mediated allergy is limited by the poor quality and allergenic activity of natural allergen extracts that are used for the production of current allergy vaccines. Today, the genetic code of the most important allergens has been deciphered; recombinant allergens equalling their natural counterparts have been produced for diagnosis and immunotherapy, and a large panel of genetically modified allergens with reduced allergenic activity has been characterized to improve safety of immunotherapy and explore allergen-specific prevention strategies. Successful immunotherapy studies have been performed with recombinant allergens and hypoallergenic allergen derivatives and will lead to the registration of the first recombinant allergen-based vaccines in the near future. There is no doubt that recombinant allergen-based vaccination strategies will be generally applicable to most allergen sources, including respiratory, food and venom allergens and allow to produce safe allergy vaccines for the treatment of the most common forms of IgE-mediated allergies.

From allergen genes to allergy vaccines

IgE-mediated allergy is a hypersensitivity disease affecting more than 25% of the population. The structures of the most common allergens have been revealed through molecular cloning technology in the past two decades. On the basis of this knowledge of the sequences and three-dimensional structures of culprit allergens, investigators can now analyze the immune recognition of allergens and the mechanisms of allergic inflammation in allergic patients. Allergy vaccines have been constructed that are able to selectively target the aberrant immune responses in allergic patients via different pathways of the immune system. Here we review various types of allergy vaccines that have been developed based on allergen structures, results from their clinical application in allergic patients, and future strategies for allergen-specific immunotherapy and allergy prophylaxis.

Eosinophilic airway inflammation in a cynomolgus monkey

The present article describes an occurrence of eosinophilic airway inflammation of a 4-year-old female cynomolgus monkey in a vehicle control group of a routine toxicology study. Histologically, the airway lesion was characterized by prominent eosinophilic infiltrates, accompanied by mast cells, lymphocytes, and plasmacytes. The eosinophilic infiltrates were distributed throughout the airway: from trachea through respiratory bronchioles in the lung. The morphological feature of the lesion was indicative of an allergic airway disorder that can occur in humans with asthma. The present case is remarkable in that there is a paucity of reports on naturally occurring allergic airway disorders in nonhuman primates.

A sensitive assay for the detection of IgE bound to the major birch pollen allergen, Bet v 1, in the form of immune complexes

Allergen-IgE immune complexes, in which the IgE paratopes are occupied by allergen, remain undetected in standard IgE-detection assays which are based on capturing specific IgE by allergens.We describe an assay for the detection of immune complexes consisting of IgE bound to one of the most frequent environmental allergens, the major birch pollen allergen, Bet v 1. This assay is based on a Bet v 1-specific monoclonal antibody, Bip 1, which binds to an epitope on Bet v 1 that is distinct from the epitopes recognized by allergic patients' IgE. IgE-immune complexes formed with sera from birch pollen-allergic patients (n = 46) were undetectable with solid phase-bound allergen but could be captured by Bip 1 immobilized to nitrocellulose membranes or ELISA plates and traced with radioactively or enzymatically labelled anti-human IgE antibodies. The levels of IgE complexed with Bet v 1 measured in our assays were highly correlated with the amounts of non-complexed allergen-specific IgE as determined by the ImmunoCAP assay which is based on solid phase-bound IgE (r = 0.95; p < 0.01). Bet v 1-specific IgE could even be detected at serum dilutions below the cut off of the ImmunoCAP system (i.e., 0.35 kUA/L). We have thus developed a robust and sensitive assay for the detection and quantification of Bet v 1-IgE immune complexes which should be useful to measure allergen-bound IgE in human body fluids and in in vitro experiments.

Animal models of airway inflammation and airway smooth muscle remodelling in asthma

Asthma is a complex disease that involves chronic inflammation and subsequent decline in airway function. The widespread use of animal models has greatly contributed to our understanding of the cellular and molecular pathways underlying human allergic asthma. Animal models of allergic asthma include smaller animal models which offer 'ease of use' and availability of reagents, and larger animal models that may be used to address aspects of allergic airways disease not possible in humans or smaller animal models. This review examines the application and suitability of various animal models for studying mechanisms of airway inflammation and tissue remodelling in allergic asthma, with a specific focus on airway smooth muscle.

Allergen dose dependency of the early- and late-phase cutaneous response in the cynomolgus monkey

BACKGROUND

Cutaneous administration of allergen provides a means to confirm an allergic status, investigate the pathogenesis of allergic diseases, and/or provide a mechanism to evaluate the benefit of new potential therapeutics.

OBJECTIVE

Studies were performed to characterize the allergen-induced cutaneous early- and late-phase response (EPR and LPR) in the cynomolgus monkey.

METHODS

Following intradermal injections of Ascaris suum allergen, the cutaneous weal and flare EPR was measured 15 min post-injection, and skin biopsies were collected at 8-24 h to determine the optimal time of LPR occurrence. Biopsies were analysed for epidermal and dermal inflammatory changes.

RESULTS

The EPR was dose related with a reproducible, measurable response at 1 : 10 000 and maximal at a 1 : 100 allergen dilution. In contrast, the threshold dose required for a reproducible LPR was much greater requiring a dilution of 6 : 100, suggesting independent mechanisms for the EPR and LPR. The LPR 20 h post-allergen injection induced an inflammatory response in the upper and deep dermis. The response was characterized by a moderate perivascular to diffuse inflammation consisting of mononuclear cells, neutrophils and eosinophils. Dexamethasone, while having no effect on the EPR, reduced dermal inflammation (upper dermis, P=0.004; deep dermis, P=0.03). Similarly, dermal eosinophilia was also reduced (upper dermis, P<0.001; deep dermis, P=0.02).

CONCLUSION

Collectively, the results indicate the dose dependency of the EPR and LPR. Furthermore, our observations indicate the value of the LPR response in the cynomolgus monkey to evaluate new therapeutics for the treatment of allergic diseases such as atopic dermatitis.

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.

Nonhuman primate models of asthma

Asthma is a complex human disease that does not have an accurate counterpart in any common model organism. Most of our understanding of the immune mechanisms underlying asthma comes from studies in man and mouse. However, there are fundamental differences between the spontaneous disease in man and the experimentally induced counterparts in mice. We advocate more extensive use of nonhuman primate asthma models to reconcile these differences between man and mouse.

Kiwi fruit allergy: a review

Allergy to kiwi fruit was first described in 1981, and there have since been reports of the allergy presenting with a wide range of symptoms from localized oral allergy syndrome (OAS) to life-threatening anaphylaxis. The article reviews the available information concerning the clinical features of kiwi fruit allergy and the role of clinical investigations for diagnosis. Work identifying the major allergens in kiwi fruit has resulted in conflicting results, the possible reasons for which are discussed. The clinical associations of kiwi fruit allergy with allergies to pollens or latex are reviewed.

From allergen structure to new forms of allergen-specific immunotherapy

During the past decade, genetic information for most of the common allergens has been obtained. Using these genetic blueprints it has become possible to reconstruct, by recombinant DNA technology, almost complete repertoires of the relevant allergens and their epitopes. Recombinant allergens with the allergenic features of naturally occurring allergens have promoted allergy research and form the basis of new multiallergen tests for refined allergy diagnosis. Allergen derivatives with reduced allergenic activity have also been produced by recombinant DNA technology to increase safety and specificity of allergen-specific immunotherapy. These derivatives can be engineered to contain relevant T cell epitopes and to maintain those sequence motifs which are required for inducing protective antibody responses and therefore hold great promise for improving allergen-specific immunotherapy.

Quantitative IgE inhibition experiments with purified recombinant allergens indicate pollen-derived allergens as the sensitizing agents responsible for many forms of plant food allergy

BACKGROUND

Type I allergic symptoms in the oropharyngeal mucosa upon contact with plant-derived food in patients with pollen allergies have been termed oral allergy syndrome (OAS). IgE cross-reactivity between pollen and food allergens represents the molecular basis for this phenomenon. The sensitizing allergen source (pollen or plant food) in OAS is a controversial issue.

OBJECTIVE

We sought to determine the primary sensitizing molecules in patients with OAS.

METHODS

We used recombinant birch pollen (rBet v 1 and rBet v 2) and plant food allergens (apple, rMal d 1; celery, rApi g 1; and carrot, rDau c 1), as well as natural pollen (birch and timothy grass) and plant food (apple, peach, kiwi, hazelnut, celery, and carrot) allergens, to identify cross-reactive allergens by using qualitative immunoblot inhibitions. In addition, we determined the percentage of plant food-specific IgE that can be preadsorbed with recombinant and natural pollen allergens by quantitative RAST inhibitions by using sera from 71 patients with OAS.

RESULTS

Preincubation of sera with recombinant and natural pollen allergens led to an almost complete inhibition of IgE binding to plant food allergens in Western blots, as well as in RAST inhibition experiments. In contrast, recombinant plant food allergens poorly inhibited IgE binding to Bet v 1.

CONCLUSION

Most IgE epitopes in plant food recognized by patients with OAS are resembled by pollen allergens. Thus pollen allergens may be responsible for the elicitation and maintenance of OAS.

Immunization with Purified Natural and Recombinant Allergens Induces Mouse IgG1 Antibodies That Recognize Similar Epitopes as Human IgE and Inhibit the Human IgE-Allergen Interaction and Allergen-Induced Basophil Degranulation

Molecular characterization of allergens by recombinant DNA technology has made rapid progress in the recent few years. In the present study we immunized mice with aluminum hydroxide-adsorbed purified recombinant major timothy grass pollen allergens (rPhl p 1, rPhl p 2, rPhl p 5), dog albumin, a major animal dander allergen, and proteins with low (β-lactoglobulin) or no (ribulose diphosphate carboxylase) allergenic potential in humans. Allergens that bind high levels of IgE in humans (Phl p 1, Phl p 5, dog albumin) induced high IgE and IgG1 levels in mice, whereas proteins with little or no allergenic activity in humans failed to induce significant IgE and IgG1 levels in mice. Continuous immunization for a period of 27 wk resulted in the production of mouse IgG1 Abs that recognized recombinant allergen fragments/epitopes defined by IgE Abs of allergic patients. As a consequence, allergen-specific mouse Abs strongly inhibited human IgE binding to the allergens and suppressed the allergen-induced histamine release from human basophils. In summary, our data indicate that 1) the allergenic potency of a protein may be related to its overall immunogenicity and 2) prolonged immunization with single purified recombinant allergens induces protective IgG Abs. The presented experimental in vivo/in vitro system allows the evaluation of Ag preparations (e.g., recombinant allergens) to be used for immunotherapy in humans.

Recombinant allergens

A great variety of recombinant plant, mite, mold, mammal, and insect allergens have been expressed in heterologous hosts (e.g., Escherichia coli), their cDNA being used as a template. The number of biologically active recombinant allergens available for experimental, diagnostic, and therapeutic purposes is increasing tremendously. Recombinant allergens have proven to be valuable tools to investigate T-cell and B-cell recognition of allergens as well as to study mechanisms of specific IgE regulation. The immunologic equivalence of many relevant recombinant allergens with their natural counterparts has been demonstrated, and the three-dimensional structures of several recombinant allergens have been described recently. As a result of extensive cross-reactivities among the relevant allergens, it appears that the number of epitopes needed for diagnosis and specific immunotherapy is less diverse than originally anticipated and might be soon covered by recombinant molecules. Recombinant allergens have been used for successful in vitro, as well as in vivo, allergy diagnosis, and work is in progress to produce recombinant allergen derivatives with reduced anaphylactic potential to improve current forms of immunotherapy.

Induction of IgE antibodies in mice and rhesus monkeys with recombinant birch pollen allergens: different allergenicity of Bet v 1 and Bet v 2

BACKGROUND

Serologic measurements with recombinant birch pollen allergens, rBet v 1 and rBet v 2 (birch profilin), have shown that more than 95% of patients allergic to tree pollen mount high levels of IgE against rBet v 1, whereas only approximately 10% of the patients display rather low levels of IgE against rBet v 2.

OBJECTIVE

In this study an attempt was made to determine whether the different allergenicity of the major birch pollen allergen, rBet v 1, and a minor birch pollen allergen, rBet v 2, might be related to a different immunogenicity of the proteins as evaluated in experimental animal systems (mice and rhesus monkeys).

METHODS

Purified recombinant allergens were injected into mice and rhesus monkeys with aluminum hydroxide as adjuvant for elicitation of specific IgE responses. Antibody responses to the allergens were detected by immunoblotting, and time courses of immune responses were measured by ELISA.

RESULTS

In both animal models more than the 10-fold dose of rBet v 2 was required to induce IgE antibodies, and even then, the amount of specific IgE antibodies elicited with rBet v 1 was substantially higher than that induced by rBet v 2. It was noted that rBet v 2 formed stable polymers through disulfide bonds.

CONCLUSION

In two different animal models (mice and rhesus monkeys) the major birch pollen allergen, rBet v 1, induced substantially higher levels of IgE than rBet v 2. A reduced allergenicity of Bet v 2 caused by polymer formation would be in agreement with previous studies indicating reduced allergenicity of proteins on chemical polymerization.

Immunological and structural similarities among allergens: prerequisite for a specific and component-based therapy of allergy

It is known that allergic patients are frequently co-sensitized against different allergen sources. Progress made in the field of allergen characterization by molecular biological techniques has now revealed that sensitization against different allergen sources can be explained as cross-reactivity of IgE antibodies with structurally and immunologically related components present in these allergen sources. This review defines groups of cross-reactive plant allergens with significant sequence homology. The similarities among allergens may facilitate allergy diagnosis by using a few representative cross-reactive allergens to determine the patient's IgE reactivity profile (allergogram). According to that typing, a few cross-reactive allergens, carrying most of the relevant IgE epitopes, may then be selected for patient-tailored specific therapy.