Influence of the route of sensitization on local and systemic immune responses in a murine model of type I allergy

Animal Models of IgE Anaphylaxis

Allergies and atopy have emerged as significant public health concerns, with a progressively increasing incidence over the last two decades. Anaphylaxis is the most severe form of allergic reactions, characterized by a rapid onset and potentially fatal outcome, even in healthy individuals. Due to the unpredictable nature and potential lethality of anaphylaxis and the wide range of allergens involved, clinical studies in human patients have proven to be challenging. Diagnosis is further complicated by the lack of reliable laboratory biomarkers to confirm clinical suspicion. Thus, animal models have been developed to replicate human anaphylaxis and explore its pathophysiology. Whereas results obtained from animal models may not always be directly translatable to humans, they serve as a foundation for understanding the underlying mechanisms. Animal models are an essential tool for investigating new biomarkers that could be incorporated into the allergy workup for patients, as well as for the development of novel treatments. Two primary pathways have been described in animals and humans: classic, predominantly involving IgE and histamine, and alternative, reliant on IgG and the platelet-activating factor. This review will focus essentially on the former and aims to describe the most utilized IgE-mediated anaphylaxis animal models, including their respective advantages and limitations.

Mechanistic insights into silica nanoparticle-allergen interactions on antigen presenting cell function in the context of allergic reactions

The incorporation of nanomaterials into consumer products has substantially increased in recent years, raising concerns about their safety. The inherent physicochemical properties of nanoparticles allow them to cross epithelial barriers and gain access to immunocompetent cells. Nanoparticles in cosmetic products can potentially interact with environmental allergens, forming a protein corona, and together penetrate through damaged skin. Allergen-nanoparticle interactions may influence the immune response, eventually resulting in an adverse or beneficial outcome in terms of allergic reactivity. This study determines the impact of silica nanoparticle-allergen interactions on allergic sensitization by studying the major molecular mechanisms affecting allergic responses. The major birch pollen allergen Bet v 1 was chosen as a model allergen and the birch pollen extract as a comparator. Key events in immunotoxicity including allergen uptake, processing, presentation, expression of costimulatory molecules and cytokine release were studied in human monocyte-derived dendritic cells. Using an in vivo sensitization model, murine Bet v 1-specific IgG and IgE levels were monitored. Upon the interaction of allergens with silica nanoparticles, we observed an enhanced uptake of the allergen by macropinocytosis, improved proteolytic processing, and presentation concomitant with a propensity to increase allergen-specific IgG2a and decrease IgE antibody levels. Together, these events suggest that upon nanoparticle interactions the immune response is biased towards a type 1 inflammatory profile, characterized by the upregulation of T helper 1 (Th1) cells. In conclusion, the interaction of the birch pollen allergen with silica nanoparticles will not worsen allergic sensitization, a state of type 2-inflammation, but rather seems to decrease it by skewing towards a Th1-dominated immune response.

Cationic liposomes bearing Bet v 1 by coiled coil-formation are hypo-allergenic and induce strong immunogenicity in mice

Although aluminum hydroxide (alum) is widely accepted and used as safe vaccine adjuvant, there is some concern about possible toxicity upon long-lasting repeated exposure during subcutaneous allergen immunotherapy (SCIT). Our objective was to evaluate allergen-bearing liposomes as possible alternative for alum-adsorption in SCIT. A self-assembling, coiled-coil forming peptide pair was used to anchor the major birch pollen allergen Bet v 1 to the surface of cationic liposomes. The resulting nanoparticulate liposomes were characterized with respect to their physicochemical, allergenic and immunological properties. Allergenicity was studied by ImmunoCAP inhibition and rat basophil leukemia (RBL) cell assays. Immunogenicity (immunoglobulin responses) and immune skewing (cytokine responses) were evaluated upon immunization of naïve mice, and compared to alum-adsorbed Bet v 1. Bet v 1-bearing cationic liposomes with a diameter of ∼200 nm showed a positive zeta potential. The coiled-coil conjugation of Bet v 1 to the surface of liposomes resulted in about a 15-fold lower allergenicity than soluble Bet v 1 as judged by RBL assays. Moreover, the nanoparticles induced Bet v 1-specific IgG1/IgG2a responses in mice that were several orders of magnitude higher than those induced by alum-adsorbed Bet v 1. This strong humoral response was accompanied by a relatively strong IL-10 induction upon PBMC stimulation with Bet v 1. In conclusion, their hypo-allergenic properties, combined with their capacity to induce a strong humoral immune response and a relatively strong IL-10 production, makes these allergen-covered cationic liposomes a promising alternative for aluminum salt-adsorption of allergen currently used in SCIT.

Aerofloral studies and allergenicity of dominant pollen types in Taraba and Bauchi States of Northeastern Nigeria

Pollen and spores have been identified as major airborne bio-particles inducing respiratory disorders including allergic rhinitis and atopic dermatitis among hypersensitive individuals. The present study was conducted with a view to investigating monthly depositional rate of atmospheric palynomorphs to determine the influence of the immediate vegetation on airborne pollen distribution; allergenic activities of dominant atmospheric pollen types at selected study locations in Taraba and Bauchi States, Northeastern Nigeria. Bioaerosols were collected using Tauber-like pollen traps and subjected to standard palynological treatment procedures, microscopy and photomicrography. Plant enumeration within the surrounding vegetation revealed that some airborne pollen types were produced by local plants at the study locations. Spores of Nephrolepis sp., Pteris sp. and a trilete fern, as well as diatoms were also recovered. Crude protein contents of some dominant pollen types; Borreria verticillata (L.) G.F.W. Meyer and Panicum maximum Jacq. for Taraba State; Leucaena leucocephala (Lam.) de Wit. and Terminalia catappa L. for Bauchi State, were quantified and extracted to sensitize Mus musculus mice for serology (ELISA) and haematology (differential and total white blood cell counts). Statistical significance was tested and recorded in the correlation between levels of serological and haematological parameters elicited by each test group; differences between levels of these parameters elicited by each test group and those of the control, as well as at varying sensitization periods. In the Leucaena leucocephala test group, swollen body and histopathological morbid features showing more extensive areas of inflammatory cells and alveoli filled with fluid in the lungs, were recorded in two dead M. musculus, respectively. The study revealed that all the tested pollen types are possible allergens at the study locations, establishing a complexity of interaction among allergy mediators at varied periods of mice sensitization and forming a paradigm of human immune response to the different pollen allergens.

Artemisia sieversiana pollen allergy and immunotherapy in mice

This study developed a murine model of asthma using Artemisia sieversiana pollen extract (ASE) and subcutaneous immunotherapy (SCIT) without an adjuvant. BALB/c mice were sensitized subcutaneously with 25 μg of ASE and challenged with 0.1% ASE aerosol. To investigate the efficacy of SCIT, mice were subcutaneously injected with 0.3 mg ASE without adjuvant once a week for 8 weeks, followed by challenge for 3 additional days. Airway hyperresponsiveness (AHR) to methacholine, pulmonary inflammatory cell infiltration, cytokine levels of bronchoalveolar lavage fluid, histopathology of the lung, and serum allergen-specific serum IgE and IgG2a levels were assessed following the final challenge. Mice sensitized with ASE developed AHR and had significantly higher interleukin (IL)-4, IL-5, and IL-13 levels as well as lower IL-12 level than those of control mice. Moreover, mice sensitized with ASE showed increased plasma levels of allergen-specific IgE, and histologic analyses showed peribranchial infiltration of inflammatory cells and mucosal hyperplasia. After SCIT, allergic symptoms and immunological parameters were effectively improved, and the plasma level of allergen-specific IgG2a was significantly increased cmpared to that in the vehicle group. These findings described successful development of an A. sieversiana pollen-induced asthma model in BALB/c mice, with in vivo findings revealing that SCIT without adjuvant significantly improved the symptoms and pathophysiology of asthmatic mice.

Establishment and characterization of murine models of asthma and subcutaneous immunotherapy for Humulus pollen allergy

Introduction

Humulus pollen is an important cause of allergic asthma in East Asia. There have been some murine models for Humulus pollen allergy established by intraperitoneal (IP) sensitization and nasal drip stimulation, but they were not comprehensive enough. Here, we used atomized inhalation for challenge and compared the subcutaneous (SC) and IP sensitization routes to determine the optimal method to establish a model of asthma induced by Humulus pollen. Subsequently, we tried to develop a rapid subcutaneous immunotherapy (SCIT) model for Humulus allergy.

Methods

BALB/c Mice were sensitized through the SC or IP route, with respective reference to previously established sensitization methods and allergen dosing, and challenged with nebulized Humulus pollen extract to induce asthma. To compare the two sensitization methods, airway hyperresponsiveness (AHR), inflammatory cell infiltration, allergen‐specific serum immunoglobulin (Ig)E (sIgE) levels, cytokine levels, and lung histopathology were assessed. The effects of SCIT (once every other day for 16 days) on airway inflammation, AHR, sIgE, and allergen‐specific serum IgG2a (sIgG2a) levels were evaluated by using the model established in this study.

Results

Although mice sensitized by the SC or IP routes both showed AHR and airway inflammation, the SC route elicited significantly higher levels of sIgE, eosinophil inflammation, and T helper type 2 cytokines, compared with the IP route. SCIT in the treatment group significantly reduced the titers of sIgE, enhanced the titers of sIgG2a, and effectively alleviated pulmonary inflammation and AHR, compared with the vehicle group.

Conclusions

The SC route can be used to establish a murine model of Humulus pollen allergy that recapitulates the characteristics of clinical allergic asthma. Short‐term SCIT can significantly improve symptoms and pathophysiology in asthmatic mice.

A Fusion Protein of Derp2 Allergen and Flagellin Suppresses Experimental Allergic Asthma

PURPOSE

The house dust mite (HDM) is one of the most important sources of indoor allergens and a significant cause of allergic rhinitis and allergic asthma. Our previous studies demonstrated that Vibrio vulnificus flagellin B (FlaB) plus allergen as a co-treatment mixture improved lung function and inhibited eosinophilic airway inflammation through the Toll-like receptor 5 signaling pathway in an ovalbumin (OVA)- or HDM-induced mouse asthma model. In the present study, we fused the major mite allergen Derp2 to FlaB and compared the therapeutic effects of the Derp2-FlaB fusion protein with those of a mixture of Derp2 and FlaB in a Derp2-induced mouse asthma model.

METHODS

BALB/c mice sensitized with Derp2 + HDM were treated with Derp2, a Derp2 plus FlaB (Derp2 + FlaB) mixture, or the Derp2-FlaB fusion protein 3 times at 1-week intervals. Seven days after the final treatment, the mice were challenged intranasally with Derp2, and airway responses and Derp2-specific immune responses were evaluated.

RESULTS

The Derp2-FlaB fusion protein was significantly more efficacious in reducing airway hyperresponsiveness, lung eosinophil infiltration, and Derp2-specific IgE than the Derp2 + FlaB mixture.

CONCLUSIONS

The Derp2-FlaB fusion protein showed a strong anti-asthma immunomodulatory capacity, leading to the prevention of airway inflammatory responses in a murine disease model through the inhibition of Th2 responses. These findings suggest that the Derp2-FlaB fusion protein would be a promising vaccine candidate for HDM-mediated allergic asthma therapy.

Blockade of the cholinergic system during sensitization enhances lung responsiveness to allergen in rats

Although acute prophylactic administration of atropine modulates airway responsiveness, the role of the parasympathetic nervous system in the pathogenesis of sensitization and in antigen-induced bronchoconstriction remains unclear. The aim of the present study is to determine whether blocking muscarinic receptors during chronic allergen exposure modulates lung responsiveness to the specific allergen. Forty rats were randomly assigned to one of the following five treatment groups: sensitization with saline vehicle, intraperitoneal injection of ovalbumin (1 mg) with or without atropine treatment (10 mg/kg per day) and repeated ovalbumin aerosol (1.25 mg/mL for 20 minutes) either alone or combined with atropine. Lung responsiveness to methacholine (4-16 μg/kg per minute) and intravenous ovalbumin (2 mg) was established before and 21 days after treatment with forced oscillations following bilateral vagotomy. Lung cellularity was determined by analysis of bronchoalveolar lavage fluid (BALF). A lung inflammatory response in all sensitized animals was defined as an increase in the number of inflammatory cells in the BALF. Baseline respiratory mechanics and methacholine responsiveness on Days 0 and 21 were comparable in all groups. However, increases in airway resistance following intravenous allergen challenge were significantly exacerbated in rats that received atropine. Inhibition of the cholinergic nervous system during allergic sensitization potentiates bronchoconstriction following exposure to the specific allergen. These findings highlight the role of the cholinergic neuronal pathway in airway sensitization to a specific allergen.

Oocyst-Derived Extract of Toxoplasma Gondii Serves as Potent Immunomodulator in a Mouse Model of Birch Pollen Allergy

Introduction

Previously, we have shown that oral infection with Toxoplasma gondii oocysts prevented type I allergy in mice. Here we investigated whether the application of a T. gondii oocyst lysate antigen (OLA) could also reduce allergy development. BALB/c mice were immunised twice with OLA followed by sensitisation with the major birch pollen (BP) allergen Bet v 1 and an aerosol challenge with BP extract.

Methods

First, we tested OLA in vitro. Stimulation of splenocytes and bone marrow-derived dendritic cells (BMDC) with OLA led to the production of pro-inflammatory and regulatory cytokines such as IL-6, IFN-γ and IL-10. Moreover, BMDC exposed to OLA upregulated the maturation markers CD40, CD80, CD86, and MHCII. Furthermore, OLA was recognised by TLR2-transfected human embryonic kidney cells.

Results

Immunisation of mice with OLA induced high levels of Toxoplasma-specific IgG antibodies in sera along with increased production of IFN-γ and IL-10 in Toxoplasma-antigen restimulated splenocytes. OLA reduced allergic airway inflammation as manifested by significant reduction of eosinophils in bronchoalveolar fluids, decreased cellular infiltrates and mucus production in the lungs. Accordingly, Bet v 1-specific IgE was decreased in OLA-pretreated mice. The reduced allergic immune responses were accompanied by increased numbers of CD4⁺CD25^highFoxp3⁺ regulatory T cells in spleens as well as by increased numbers of granulocytic myeloid-derived suppressor cells in lungs when compared to sensitised controls suggesting that these two cell populations might be involved in the suppression of the allergic immune responses.

Conclusion

Our data demonstrate that pretreatment with the oocyst extract can exert anti-allergic effects comparable to T. gondii infection. Thus, the immunomodulatory properties of the parasite extract indicate that this extract and in the future defined molecules thereof might serve as immunomodulatory adjuvants in allergy treatment and prophylaxis.

Routes of allergic sensitization and myeloid cell IKKβ differentially regulate antibody responses and allergic airway inflammation in male and female mice

Gender influences the incidence and/or the severity of several diseases and evidence suggests a higher rate of allergy and asthma among women. Most experimental models of allergy use mice sensitized via the parenteral route despite the fact that the mucosal tissues of the gastrointestinal and respiratory tracts are major sites of allergic sensitization and/or allergic responses. We analyzed allergen-specific Ab responses in mice sensitized either by gavage or intraperitoneal injection of ovalbumin together with cholera toxin as adjuvant, as well as allergic inflammation and lung functions following subsequent nasal challenge with the allergen. Female mice sensitized intraperitoneally exhibited higher levels of serum IgE than their male counterparts. After nasal allergen challenge, these female mice expressed higher Th2 responses and associated inflammation in the lung than males. On the other hand, male and female mice sensitized orally developed the same levels of allergen-specific Ab responses and similar levels of lung inflammation after allergen challenge. Interestingly, the difference in allergen-specific Ab responses between male and female mice sensitized by the intraperitoneal route was abolished in IKKβ^ΔMye mice, which lack IKKβ in myeloid cells. In summary, the oral or systemic route of allergic sensitization and IKKβ signaling in myeloid cells regulate how the gender influences allergen-specific responses and lung allergic inflammation.

Oral administration of allergen extracts from mugwort pollen desensitizes specific allergen-induced allergy in mice

Clinically, sublingual immunotherapy (SLIT) using allergen extracts effectively alleviates the symptoms of allergic rhinitis and asthma. We hypothesized that oral administration of a high-dose of allergen extracts imitates SLIT, which may prevent IgE-related responses in allergic diseases. In the present study, we investigated the effects of oral administration of allergen extracts from mugwort pollen (MP) on allergen-induced inflammation and airway hyperresponsiveness (AHR) in an allergic mouse model. After administration of MPdrop containing Art v 1 and Art v 4 extracts derived from MP specifically in MP-sensitized mice, the effects of MPdrop on AHR, inflammatory cell accumulation, cytokine production in the bronchoalveolar lavage fluid and lung tissue, and serum IgE and IgG levels were investigated. The results indicated that MPdrop not only prevented the AHR in response to methacholine in a dose-dependent manner but also significantly reduced the total serum and allergen-specific IgE levels. All of the maximal effects were achieved at a dose of 100μg/(kgd) and were comparable to the effects of dexamethasone at a dose of 0.5mg/(kgd). Furthermore, oral administration of MPdrop dose-dependently elevated allergen-specific serum IgG2a levels, reduced total and allergen-specific IgE levels and normalized the imbalance between the Th1 cytokine IL-12 and Th2 cytokines IL-4 and IL-5. Finally, oral administration of MPdrop significantly reduced goblet cell hyperplasia and eosinophilia in the MP-sensitized allergic mouse model. These data suggest that MPdrop effectively improves specific allergen-induced inflammation and AHR in MP-sensitized and -challenged mice and provides the rationale for clinical use of MPdrop in the specific allergen-induced asthma.

Harnessing opportunities in non-animal asthma research for a 21st-century science

The incidence of asthma is on the increase and calls for research are growing, yet asthma is a disease that scientists are still trying to come to grips with. Asthma research has relied heavily on animal use; however, in light of increasingly robust in vitro and computational models and the need to more fully incorporate the 'Three Rs' principles of Replacement, Reduction and Refinement, is it time to reassess the asthma research paradigm? Progress in non-animal research techniques is reaching a level where commitment and integration are necessary. Many scientists believe that progress in this field rests on linking disciplines to make research directly translatable from the bench to the clinic; a '21st-century' scientific approach to address age-old questions.

Factors influencing the incidence and prevalence of food allergy

Food allergy is an increasing problem in Europe and elsewhere and severe reactions to food are also becoming more common. As food allergy is usually associated with other forms of allergic sensitisation it is likely that many risk factors are common to all forms of allergy. However the potential severity of the disease and the specific public heath measures required for food allergy make it important to identify the specific risk factors for this condition. Food allergy is unusual in that it often manifests itself very early in life and commonly remits with the development of tolerance. Hypotheses that explain the distribution of food allergy include specific genetic polymorphisms, the nature of the allergens involved and the unique exposure to large quantities of allergen through the gut. Progress has been made in developing more specific and testable hypotheses but the evidence for any of these is still only preliminary. Further collaborative research is required to develop an appropriate public health response to this growing problem.

Fine ambient particles from various sites in europe exerted a greater IgE adjuvant effect than coarse ambient particles in a mouse model

In the European Union (EU)-funded project Respiratory Allergy and Inflammation due to Ambient Particles (RAIAP), coarse and fine ambient particulate matter (PM) was collected at traffic dominated locations in Oslo, Rome, Lodz, and Amsterdam, in the spring, summer, and winter 2001/2002. PM was also collected in de Zilk, a rural seaside background location in the Netherlands. The aim of this study was to screen the ambient PM fractions for allergy adjuvant activity measured as the production of allergen- (ovalbumin-) specific immunoglobulin (Ig) E following subcutaneous (sc) injection into the footpad of mice. A second aim was to determine whether the 6-d popliteal lymph node (PLN) assay can be used to detect an allergy adjuvant activity. Allergy screening for IgE adjuvant activity showed that in the presence of ovalbumin (Ova) 12 out of 13 of the fine ambient PM fractions exerted a significant IgE adjuvant activity. In contrast, only 3 out of 13 of the coarse PM fractions had significant adjuvant activity. Overall, fine ambient PM exerted significantly greater IgE adjuvant activity per unit mass than coarse PM. No significant differences were observed between locations or seasons. Substantial higher levels of specific components of PM such as vanadium (V), nickel (Ni), zinc (Zn), ammonium (NH(4)), and sulfate (SO(4)) were present in the fine compared to coarse PM fractions. However, differences in the content of these components among fine PM fractions did not reflect the variation in the levels of IgE anti-Ova. Still, when comparing all seasons overall, positive correlations were observed between V, Ni, and SO(4) and the allergen specific IgE levels. The PLN responses (weight and cell number) to Ova and ambient PM in combination were significantly higher than to Ova or PM alone. Still, the PLN assay appears not to be useful as a quantitative assay for screening of allergy adjuvant activity since no correlation was observed between PLN responses and allergen specific IgE levels. In conclusion, fine ambient PM fractions consistently were found to increase the allergen-specific IgE responses more than the coarse ones. Our finding is in agreement with the notion that traffic-related air pollution contributes to the disease burden in asthma and allergy, and points to fine and ultrafine ambient PM as the most important fractions in relation to allergic diseases.

Pediococcus pentosaceus NB-17 for probiotic use

The plant-derived Pediococcus pentosaceus NB-17 was isolated from Japanese traditional vegetable pickles. The production of cytokines from mouse spleen cells co-cultivated with heat-killed bacteria was investigated in vitro. The bacteria significantly induced secretion levels of interferon (IFN)-gamma and interleukin (IL)-12 p70, and suppressed IL-4 productions in ovalbumin (OVA) sensitized mouse spleen cells. Therefore, the bacteria could effectively stimulate immune activities and showed allergic inhibitory effects. Further study on acid tolerance was performed under simulated gastric conditions and NB-17 showed resistance to simulated gastric acidity at pH 3.0 and pH 2.5. Moreover, after oral administration of the intact cells to rats, bacterial colonies derived from feces were analyzed by random amplification polymorphic DNA (RAPD). It was confirmed that the administered strain NB-17 remained alive in feces. These results suggest the possibility to use the P. pentosaceus NB-17 as functional foods.

Allergy as an organ and a systemic disease

Allergic disorders are viewed generally as organ diseases and thus referred to organ specialists, such as the ear, nose and throat specialist for rhinitis, the pulmonologist for asthma, the dermatologist for dermatitis, and so on. Indeed, the systemic nature of allergy is made evident by the fact that the same individual may develop during the life different manifestations to a given allergen. This is true for example in sensitisation to house dust mites, which may start in childhood as atopic dermatitis and later express as asthma or rhinitis. The major player in driving the immune response is the T lymphocyte, and the T helper subpopulations--Th1 and Th2--as well as the T regulatory cells, are involved in orienting tolerance or reactivity to allergens. Interesting observations on the systemic or organ-specific actions of T cells were obtained by transplantations from allergic donors to non-allergic recipients. Bone marrow is able to transfer all allergic manifestations, while lung transplantation transfers only asthma. A number of factors are involved in the expression of allergy as a systemic or organ disease and deserve deeper investigations. They include the antigen presenting cells, the homing of T cells, the cytokine and chemokine pattern, and the adhesion molecules.

Carbohydrate-based particles reduce allergic inflammation in a mouse model for cat allergy

BACKGROUND

Allergen-specific immunotherapy (ASIT) is the only treatment of allergic disease that gives long-lasting relief of symptoms. However, concerns for safety and efficiency have highlighted the need for improvement of the therapy. We have previously suggested carbohydrate-based particles (CBPs) as a novel adjuvant and allergen carrier for ASIT. Our aim of this study was to evaluate the therapeutic potential of CBPs in ASIT, employing a mouse model for cat allergy.

METHODS

BALB/c mice were subcutaneously immunized with the recombinant (r) cat allergen Fel d 1 followed by intranasal challenge with cat dander extract (CDE). The sensitized mice were therapeutically treated with rFel d 1 covalently coupled to CBPs (CBP-rFel d 1). Airway hyper-reactivity (AHR), infiltration of leucocytes in bronchoalveolar lavage (BAL) fluid, allergen-specific serum immunoglobulin levels and in vitro splenocyte responses were evaluated.

RESULTS

Mice treated with CBP-rFel d 1 showed reduced features of allergic inflammation. They responded with (i) significantly decreased AHR and infiltration of eosinophils in BAL fluid after CDE challenge, (ii) the serum level of rFel d 1-specific IgE was reduced and the level of IgG(2)a was more pronounced after CBP-rFel d 1 treatment, and (iii) there was also a tendency of decreased allergen-specific cellular response.

CONCLUSIONS

Carbohydrate-based particles are effective tools as adjuvant and allergen carriers for use in ASIT and constitutes a promising strategy to improve allergy treatment.

Tissue localization and frequency of antigen-specific effector CD4 T cells determines the development of allergic airway inflammation

Previous activation of effector Th2 cells is central to the development of allergic inflammatory responses. We have observed that priming of allergen-specific Th2 cells in C57BL/6 or B10.A mice with allergen delivered via the i.p. or s.c. routes results in very different outcomes following subsequent airway exposure to the same allergen. Systemic allergen immunization (via the i.p. route) resulted in the formation of a lung-resident population of allergen-specific T cells, and mice developed severe allergic airway inflammation in response to inhaled allergen. The localization of cells to the lung did not require the presence of antigen at this site, but reflected a large pool of circulating activated allergen-specific T cells. In contrast, localized immunization (via the s.c. route) resulted in a small T-cell response restricted to the draining lymph node, and mice were not responsive to inhaled allergen. These data indicate that prior sensitization to an allergen alone was not sufficient for the induction of allergic inflammation; rather, responsiveness was largely determined by precursor frequency and tissue localization of the allergen-specific effector Th2 cells.

Pollen-induced airway inflammation, hyper-responsiveness and apoptosis in a murine model of allergy

BACKGROUND

Previous studies indicate that murine models are useful tools for studying the allergic diseases, including certain aspects of bronchial asthma such as cellular tissue inflammation and pulmonary function.

OBJECTIVE

To develop an experimental model of allergic lung inflammation based on a relevant human allergen, olive pollen, and to establish the immunological, cellular and functional airway features of the allergic response in this model.

METHODS

Induction of systemic allergic response was achieved by the subcutaneous administration of Olea europaea extract in BALB/c mice. Olea-specific Igs (IgG1, IgG2a and IgE) and cytokines from splenocyte cultures IL-4, IL-5 IL-10, IL-13 and IFN-gamma were measured. Allergic airway response was generated by transnasal instillation of the allergens. Airway responsiveness was monitored by non-invasive methacholine inhalation challenge. Lungs were paraffin embedded and histologically analysed. Apoptosis was studied by the TUNEL technique in the lung tissue and through cell cycle analysis by flow cytometry in splenocytes.

RESULTS

Our results demonstrate that Olea-sensitized mice develop a specific allergic antibody (IgG1 and IgE) and cytokine (IL-4, IL-5, IL-10 and IL-13) response. After transnasal Olea instillation, they show inflammatory infiltration of lung tissue, mucus secretion and non-specific hyper-responsiveness in the airway. Concomitantly, differences in the rate of apoptosis are observed in the lung cells as well as a significant reduction of spontaneous apoptosis in the splenocytes of allergic mice.

CONCLUSION

We present a novel animal model of olive pollen-allergic disease. This model presents traits associated with human allergic asthma and could be an interesting tool in the study of underlying molecular mechanisms and in exploring the therapeutic approaches to this disease.

Gantrez® AN nanoparticles as an adjuvant for oral immunotherapy with allergens

The aim of this study was to investigate the adjuvant properties of oral-administered Gantrez AN nanoparticles with ovalbumin (as allergen model) and, in some cases, lipopolysaccharide of Brucella ovis as immunomodulator. For this purpose, BALB/c mice were administered by oral gavage with OVA nanoparticles and both Th1 and Th2 markers (IgG2a and IgG1, respectively) were enhanced. On the other hand, these carriers administered by oral route were able to protect a model of sensitized mice to ovalbumin from anaphylactic shock. These results are highly suggestive for the valuable use of Gantrez nanoparticles in oral immunotherapy with allergens.

Murine airway histology and intracellular uptake of inhaled amorphous itraconazole

Aerosolization of amorphous itraconazole may be a safe and effective method of pulmonary delivery. Our objective was to evaluate the histologic effects, immunogenic potential, and cellular uptake of aerosolized amorphous itraconazole. Mice received amorphous itraconazole (30mg/kg), excipient placebo, or saline control by nebulization every 12h for up to 12 days. Broncho-alveolar lavage (BAL) and formalin fixation of both lungs were conducted. BAL supernatant was assayed for IL-12 by ELISA, and cellular components were analyzed by high performance liquid chromatography-mass spectroscopy. Coronal sections of the entire lung were stained, viewed by light microscopy, and the Cimolai histopathologic inflammatory score was obtained for each lobe. No evidence of bronchiolar, peribronchiolar or perivascular inflammation was found in any treatment group, nor were epithelial ulceration or repair observed. The Cimolai histopathologic scores for amorphous itraconazole, excipient, and saline control on days 3 and 8 did not differ between groups. ELISA analysis showed no cytokine induction of IL-12. Itraconazole was detected within cells collected from BAL fluid on days 1, 3, 8 and 12. Aerosolized administration of amorphous itraconazole or excipients does not cause inflammation or changes in pulmonary histology and are not associated with pro-inflammatory cytokine production.

A recombinant allergen chimer as novel mucosal vaccine candidate for prevention of multi-sensitivities

BACKGROUND

As conventional immunotherapy is less efficacious in patients with allergic multi-sensitivities compared with mono-sensitized subjects, new intervention strategies are needed. Therefore, an allergen chimer was genetically engineered for treatment of multi-sensitization with birch and grass pollen on the basis of mucosal tolerance induction.

METHODS

The major birch pollen allergen Bet v 1 served as a scaffold for N- and C-terminal linkage of the immunodominant peptides of the grass pollen allergens Phl p 1 and Phl p 5 and this new construct was cloned and expressed in Escherichia coli. After purification, physicochemical and immunological characterization the chimer was used for intranasal tolerance induction prior to poly-sensitization with Bet v 1, Phl p 1 and Phl p 5.

RESULTS

The immunological characterization revealed that the conformation of Bet v 1 within the chimer was comparable to that of natural as well as recombinant Bet v 1. The chimer was immunogenic in mice for T and B cell responses to the three allergens. Intranasal application of the chimer prior to poly-sensitization significantly suppressed humoral and cellular allergen-specific Th2 responses and prevented development of airway inflammation upon allergen challenge. Moreover, local allergen-specific IgA antibodies were induced by the chimer. The mechanisms of poly-tolerance induction seemed to be mediated by regulatory cytokines, since TGF-beta and IL-10 mRNA in splenocytes were upregulated and tolerance was transferable with these cells.

CONCLUSION

The data indicate that such allergen chimers harboring several unrelated allergens or allergen peptides could serve as mucosal polyvalent vaccines for prevention of multi-sensitivities.

Epitope characterization of ovalbumin in BALB/c mice using different entry routes

Ovalbumin (OVA) is known as a major allergen in egg white. A number of studies have reported the partial T and B cell epitope mapping of OVA using murine models and allergic patients' sera. Recently, we have reported the IgE-binding regions of the entire OVA molecule using egg allergic patients' sera. However, the entire epitope mapping of OVA in a murine model has not been completed yet. In the present study, BALB/c mice were administered a solution of OVA using three different entry routes (oral, intraperitoneal and subcutaneous) with their respective adjuvant (cholera toxin, aluminum hydroxide and Freund's adjuvant). Two nitrocellulose membranes containing 188 overlapping synthetic peptides (with a length of 12 amino acids and an offset of two amino acids) covering the primary sequence of OVA, were probed with the three different BALB/c mice antisera. Antisera obtained from orally challenged mice identified eight IgE epitope regions, i.e. I53D60; V77R84; S103E108; G127T136; E275V280; G301F306; I323A332 and A375S384, while sera raised by intraperitoneal and subcutaneous injections exhibited two (K55D60 and K277L282) and five (K55R58; G127T136; K279L282; T303S308 and I323A332) IgE binding sequences, respectively. The residues critical for the epitope-paratope interactions were finely characterized using the oral immunization serum. Analysis of IgE binding epitopes in mice provides us with potential strategies for design of specific immunotherapy.

Gastro-Intestinal Exposure to Latex Antigens Induce Allergic Responses in Mice

BACKGROUND

Natural rubber latex (NRL) has emerged as a major cause of respiratory allergy among specific exposed groups of individuals. Since latex allergens are dispersed in the environment it is conceivable that latex proteins are both inhaled and ingested. The mechanism of latex allergy and the immune responses following reexposure of latex allergens by the intranasal route was studied in a murine model of latex allergy developed by intragastric sensitization with NRL.

METHODS

BALB/c mice were sensitized intragastrically ('ig'), intranasally ('in') or 'ig' followed by 'in' challenge with NRL allergens. The cellular and humoral immune responses, lung function and histological changes were determined.

RESULTS

Peripheral blood eosinophilia was observed in the 'ig' and 'ig/in'-NRL-sensitized animals in comparison to normal controls (p < 0.05). The 'ig' group showed a marked increase over control mice in serum total IgE, NRL-specific IgG and IgG subclasses (p < 0.05). Increased levels of IL-4, IL-5, IL-10, and IL-13 were detected in 'ig'-NRL-sensitized mice. Intranasal exposure with NRL after 'ig' sensitization further enhanced the cytokine levels. A tendency towards enhanced stimulation was determined in 'ig'-sensitized mice; a significant difference was shown in the 'ig/in'-group (p < 0.05). Increased airway hyperreactivity was found in 'ig'-NRL-sensitized-mice (15.1 +/- 2.5 vs. 8.9 +/- 1.7 cm H2O x ml(-1) x s, p < 0.05). Mucus secretion from jejunal epithelium and eosinophilic infiltration into the jejunal lamina propria were observed in the 'ig'-NRL-sensitized-mice.

CONCLUSIONS

The results demonstrate that intragastric NRL sensitization did not induce specific tolerance, and additional intranasal exposure with latex allergens resulted in systemic allergic manifestations in the murine model.

Modulation of allergic immune responses by mucosal application of recombinant lactic acid bacteria producing the major birch pollen allergen Bet v 1

BACKGROUND

Probiotic lactic acid bacteria (LAB) are able to modulate the host immune system and clinical trials have demonstrated that specific strains have the capacity to reduce allergic symptoms. Therefore, we aimed to evaluate the potential of recombinant LAB producing the major birch pollen allergen Bet v 1 for mucosal vaccination against birch pollen allergy.

METHODS

Recombinant Bet v 1-producing Lactobacillus plantarum and Lactococcus lactis strains were constructed. Their immunogenicity was compared with purified Bet v 1 by subcutaneous immunization of mice. Intranasal application of the live recombinant strains was performed to test their immunomodulatory potency in a mouse model of birch pollen allergy.

RESULTS

Bet v 1 produced by the LAB was recognized by monoclonal anti-Bet v 1 and IgE antibodies from birch pollen-allergic patients. Systemic immunization with the recombinant strains induced significantly lower IgG1/IgG2a ratios compared with purified Bet v 1. Intranasal pretreatment led to reduced allergen-specific IgE vs enhanced IgG2a levels and reduced interleukin (IL)-5 production of splenocytes in vitro, indicating a shift towards non-allergic T-helper-1 (Th1) responses. Airway inflammation, i.e. eosinophils and IL-5 in lung lavages, was reduced using either Bet v 1-producing or control strains. Allergen-specific secretory IgA responses were enhanced in lungs and intestines after pretreatment with only the Bet v 1-producing strains.

CONCLUSIONS

Mucosal vaccination with live recombinant LAB, leading to a shift towards non-allergic immune responses along with enhanced allergen-specific mucosal IgA levels offers a promising approach to prevent systemic and local allergic immune responses.