Allergic airway sensitization induces T cell activation but not airway hyperresponsiveness in B cell-deficient mice

Natural antibodies drive type 2 immunity in response to damage-associated molecular patterns

Allergic airway disease (AAD) is an example of type 2 inflammation that leads to chronic airway eosinophilia controlled by CD4 Th2 cells. Inflammation is reinforced by mast cells and basophils armed with allergen-specific IgE made by allergen-specific B2 B cells of the adaptive immune system. Little is known about how AAD is affected by innate B1 cells, which produce natural antibodies (NAbs) that facilitate apoptotic cell clearance and detect damage- and pathogen-associated molecular patterns (DAMPS and PAMPS). We used transgenic mice lacking either B cells or NAbs in distinct mouse models of AAD that require either DAMPS or PAMPS as the initial trigger for type 2 immunity. In a DAMP-induced allergic model, driven by alum and uric acid, mouse strains lacking B cells (CD19DTA), NAbs (IgHEL MD4), or all secreted antibodies (sIgm-/-Aid-/-) displayed a significant reduction in both eosinophilia and Th2 priming compared with WT or Aid-/- mice lacking only germinal center-dependent high-affinity class-switched antibodies. Replenishing B cell-deficient mice with either unimmunized B1 B cells or NAbs during sensitization restored eosinophilia, suggesting that NAbs are required for licensing antigen-presenting cells to prime type 2 immunity. Conversely, PAMP-dependent type 2 priming to house dust mite or Aspergillus was not dependent on NAbs. This study reveals an underappreciated role of B1 B cell-generated NAbs in selectively driving DAMP-induced type 2 immunity.

Regulatory B cells in respiratory health and diseases

B cells are critical mediators of humoral immune responses in the airways through antibody production, antigen presentation, and cytokine secretion. In addition, a subset of B cells, known as regulatory B cells (Bregs), exhibit immunosuppressive functions via diverse regulatory mechanisms. Bregs modulate immune responses via the secretion of IL‐10, IL‐35, and tumor growth factor‐β (TGF‐β), and by direct cell contact. The balance between effector and regulatory B cell functions is critical in the maintenance of immune homeostasis. The importance of Bregs in airway immune responses is emphasized by the different respiratory disorders associated with abnormalities in Breg numbers and function. In this review, we summarize the role of immunosuppressive Bregs in airway inflammatory diseases and highlight the importance of this subset in the maintenance of respiratory health. We propose that improved understanding of signals in the lung microenvironment that drive Breg differentiation can provide novel therapeutic avenues for improved management of respiratory diseases.

Developments in the field of allergy in 2017 through the eyes of Clinical and Experimental Allergy

In this article, we described the development in the field of allergy as described by Clinical and Experimental Allergy in 2017. Experimental models of allergic disease, basic mechanisms, clinical mechanisms, allergens, asthma and rhinitis and clinical allergy are all covered.

Isolated Schistosoma mansoni eggs prevent allergic airway inflammation

Chronic helminth infection with Schistosoma (S.) mansoni protects against allergic airway inflammation (AAI) in mice and is associated with reduced Th2 responses to inhaled allergens in humans, despite the presence of schistosome‐specific Th2 immunity. Schistosome eggs strongly induce type 2 immunity and allow to study the dynamics of Th2 versus regulatory responses in the absence of worms. Treatment with isolated S. mansoni eggs by i.p. injection prior to induction of AAI to ovalbumin (OVA)/alum led to significantly reduced AAI as assessed by less BAL and lung eosinophilia, less cellular influx into lung tissue, less OVA‐specific Th2 cytokines in lungs and lung‐draining mediastinal lymph nodes and less circulating allergen‐specific IgG1 and IgE antibodies. While OVA‐specific Th2 responses were inhibited, treatment induced a strong systemic Th2 response to the eggs. The protective effect of S. mansoni eggs was unaltered in μMT mice lacking mature (B2) B cells and unaffected by Treg cell depletion using anti‐CD25 blocking antibodies during egg treatment and allergic sensitization. Notably, prophylactic egg treatment resulted in a reduced influx of pro‐inflammatory, monocyte‐derived dendritic cells into lung tissue of allergic mice following challenge. Altogether, S. mansoni eggs can protect against the development of AAI, despite strong egg‐specific Th2 responses.

House Dust Mite-Induced Allergic Airway Disease Is Independent of IgE and FcεRIα

IgE contributes to disease exacerbations but not to baseline airway hyperresponsiveness (AHR) in human asthma. In rodent allergic airway disease (AAD), mast cell and IgE dependence for the induction of AHR has only been observed when mice are immunized with a relatively weak allergen without adjuvant. To evaluate the role of IgE in murine AAD that is induced by a potent allergen, we inoculated BALB/c and FVB/N background wild-type and IgE- or FcεRIα-deficient mice intratracheally with large or limiting doses of house dust mite extract (HDM) and evaluated AHR, pulmonary eosinophilia, goblet cell metaplasia, serum IgE, and lung mastocytosis. We found that neither IgE nor FcεRIα contributed to AAD, even in mice inoculated with the lowest dose of HDM, which readily induced detectable disease, but did not increase serum IgE or pulmonary mast cell levels. In contrast, high doses of HDM strikingly increased serum IgE and pulmonary mast cells, although both AHR and airway mast cell degranulation were equally elevated in wild-type and IgE-deficient mice. Surprisingly, allergen challenge of mice with severe AAD and pulmonary mastocytosis failed to acutely increase airway resistance, lung Newtonian resistance, or hysteresis. Overall, this study shows that, although mice may not reliably model acute asthma exacerbations, mechanisms that are IgE and FcεRIα independent are responsible for AHR and airway inflammation when low doses of a potent allergen are inhaled repetitively.

B cell subsets are modulated during allergic airway inflammation but are not required for the development of respiratory tolerance in a murine model

Allergic asthma is a widespread chronic inflammatory disease of the airways. The role of different B cell subsets in developing asthma and respiratory tolerance is not well known. Especially regulatory B (Breg) cells are proposed to be important in asthma regulation. Using wild-type (WT) and B cell-deficient (μMT) mice we investigated how B cells are affected by induction of allergic airway inflammation and respiratory tolerance and whether they are necessary to develop these conditions. WT mice with an asthma-like phenotype, characterized by increased airway hyper reactivity, eosinophilic airway inflammation, mucus hypersecretion and elevated Th2 cytokines, exhibited increased MHCII and CD23 expression on follicular mature B cells in lung, bronchial lymph nodes (bLN) and spleen, which contributed to allergen-specific T cell proliferation in vitro. Germinal center B cell numbers were elevated and associated with increased production of allergen-specific immunoglobulins especially in bLN. In contrast, respiratory tolerance clearly attenuated these B cell alterations and directly enhanced marginal zone precursor B cells, which induced regulatory T cells in vitro. However, μMT mice developed asthma-like and tolerized phenotypes like WT mice. Our data indicate that although B cell subsets are affected by asthma-like and respiratory tolerant phenotypes, B cells are not required for tolerance induction.

Development of eosinophilic inflammation is independent of B-T cell interaction in a chronic house dust mite-driven asthma model

BACKGROUND

Chronic exposure to environmental triggers, such as house dust mite (HDM), drives T helper 2 (Th2) cell-mediated asthma. Recent evidence has shown that B-T cell interaction, and in particular germinal centre reactions and follicular T helper (Tfh) cells are required for the development of eosinophilic airway inflammation in HDM-driven models containing a sensitization and challenge phase. Whether B-T cell interactions are essential for pulmonary eosinophilic inflammation following chronic allergen provocation remains unknown.

AIMS

In this study, we investigated the importance of B-T cell interaction in the development of eosinophilic airway inflammation and pulmonary remodelling in a chronic HDM-driven asthma model.

METHODS

We exposed C57BL/6, Cd40l^-/- , and Mb1^-/- mice to HDM three times a week for five consecutive weeks.

RESULTS

Chronic HDM exposure induced a pronounced eosinophilic allergic airway inflammation in broncho-alveolar lavage fluid (BALf) and lung tissue, associated with the formation of immunologically active inducible bronchus-associated lymphoid tissue (iBALT) in the lungs. The absence of B cells or lack of CD40L signalling did not hamper eosinophilic inflammation in the airways, although the number of Tfh and Th2 cells was substantially reduced in the lungs. Importantly, type 2 innate lymphoid cell (ILC2) numbers in BALf and lung were not affected by the absence of B cells or B-T cell interaction. Furthermore, eosinophilic airway inflammation is not sufficient to induce pulmonary remodelling and airway hyperresponsiveness.

CONCLUSION AND CLINICAL RELEVANCE

From these findings, we conclude that B-T cell interaction is required for robust Tfh and Th2 cell induction, but not essential for eosinophilic airway inflammation during a chronic HDM-driven asthma model.

House dust mite-driven asthma and allergen-specific T cells depend on B cells when the amount of inhaled allergen is limiting

BACKGROUND

Allergic asthma is a CD4 T_H2-lymphocyte driven disease characterized by airway hyperresponsiveness and eosinophilia. B cells can present antigens to CD4 T cells and produce IgE immunoglobulins that arm effector cells; however, mouse models are inconclusive on whether B cells are necessary for asthma development.

OBJECTIVES

We sought to address the role of B cells in a house dust mite (HDM)-driven T_H2-high asthma mouse model.

METHODS

Wild-type and B cell-deficient muMT mice were sensitized and challenged through the airways with HDM extracts. The antigen-presenting capacities of B cells were studied by using new T-cell receptor transgenic 1-DER mice specific for the Der p 1 allergen.

RESULTS

In vitro-activated B cells from HDM-exposed mice presented antigen to 1-DER T cells and induced a T_H2 phenotype. In vivo B cells were dispensable for activation of naive 1-DER T cells but necessary for full expansion of primed 1-DER T cells. At high HDM challenge doses, B cells were not required for development of pulmonary asthmatic features yet contributed to T_H2 expansion in the mediastinal lymph nodes but not in the lungs. When the amount of challenge allergen was decreased, muMT mice had reduced asthma features. Under these limiting conditions, B cells contributed also to expansion of T_H2 effector cells in the lungs and central memory T cells in the mediastinal lymph nodes.

CONCLUSION

B cells are a major part of the adaptive immune response to inhaled HDM allergen, particularly when the amount of inhaled allergen is low, by expanding allergen-specific T cells.

CD4⁺ and CD8⁺ T cells play a central role in a HDM driven model of allergic asthma

Background

The incidence of asthma is increasing at an alarming rate and while the current available therapies are effective in the majority of patients they fail to adequately control symptoms at the more severe end of the disease spectrum. In the search to understand disease pathogenesis and find effective therapies animal models are often employed. As exposure to house dust mite (HDM) has a causative link, it is thought of as the allergen of choice for modelling asthma.

The objective was to develop a HDM driven model of asthmatic sensitisation and characterise the role of key allergic effector cells/mediators.

Methods

Mice were sensitised with low doses of HDM and then subsequently challenged. Cellular inflammation, IgE and airway responsiveness (AHR) was assessed in wild type mice or CD4⁺/CD8⁺ T cells, B cells or IgE knock out mice.

Results

Only those mice sensitised with HDM responded to subsequent low dose topical challenge. Similar to the classical ovalbumin model, there was no requirement for systemic alum sensitisation. Characterisation of the role of effector cells demonstrated that the allergic cellular inflammation and AHR was dependent on CD4⁺ and CD8⁺ T cells but not B cells or IgE. Finally, we show that this model, unlike the classic OVA model, appears to be resistant to developing tolerance.

Conclusions

This CD4⁺/CD8⁺ T cell dependent, HDM driven model of allergic asthma exhibits key features of asthma. Furthermore, we suggest that the ability to repeat challenge with HDM means this model is amenable to studies exploring the effect of therapeutic dosing in chronic, established disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0359-y) contains supplementary material, which is available to authorized users.

Amelioration of some immunological disorders caused by the faeces of the dominant true house dust mites in El-Minia Governorate, Egypt

BACKGROUND

House dust mites (HDMs) faeces are the main factor involved in respiratory disorder. The true HDMs, Dermatophagoides pteronyssinus and D. farinae, detected in the samples collected from the house dust are the most important causes of allergic disorders such as asthma.

OBJECTIVE

The aim of this investigation was to study the curcuma and karkade amelioration of the allergenic immunological disorder, especially some cytokines, IgE and ROS, caused by the faeces of the dominant true HDM, D. pteronyssinus and D. farinae in valley and desert houses in EL-Minia Governorate, respectively.

METHODS

HDM cultures, faeces isolation, plant extraction and ELISA techniques were used. Male albino rats were classified into control, inhaled, and treated groups.

RESULTS

The present immunological study on the dominant allergenic true HDMs, D. pteronyssinus and D. farinae, revealed that significantly higher serum levels of TNF-α, IL-1β, IL-4, IL-13 and IgE were found in rats treated with both D. pteronyssinus and D. farinae faeces than the other groups. In addition, statistical analysis of ROS data showed significant difference between the curcuma- and karkade-treated groups and either the control or the faeces-treated groups (P<0.05).

CONCLUSIONS

Some immunological disturbances caused by repeated exposure to the faeces of two dominant allergenic true HDM species (D. pteronyssinus and D. farinae) in the valley and desert houses could be ameliorated by curcuma and karkade.

B cells play key roles in th2-type airway immune responses in mice exposed to natural airborne allergens

Humans are frequently exposed to various airborne allergens. In addition to producing antibodies, B cells participate in immune responses via various mechanisms. The roles of B cells in allergic airway inflammation and asthma have been controversial. We examined the functional importance of B cells in a mouse model of asthma, in which mice were exposed repeatedly to common airborne allergens. Naïve wild-type BALB/c mice or B cell-deficient JH^−/− mice were exposed intranasally to a cocktail of allergen extracts, including Alternaria, Aspergillus, and house dust mite, every other day for two weeks. Ovalbumin was included in the cocktail to monitor the T cell immune response. Airway inflammation, lung pathology, and airway reactivity were analyzed. The airway exposure of naïve wild type mice to airborne allergens induced robust eosinophilic airway inflammation, increased the levels of Th2 cytokines and chemokines in the lung, and increased the reactivity to inhaled methacholine. These pathological changes and immune responses were attenuated in B cell-deficient JH^−/− mice. The allergen-induced expansion of CD4⁺ T cells was impaired in the lungs and draining lymph nodes of JH^−/− mice. Furthermore, lymphocytes from JH^−/− mice failed to produce Th2 cytokines in response to ovalbumin re-stimulation in vitro. Our results suggest that B cells are required for the optimal development of Th2-type immune responses and airway inflammation when exposed to common airborne allergens. The therapeutic targeting of B cells may be beneficial to treat asthma in certain patients.

Hyaluronan stimulates ex vivo B lymphocyte chemotaxis and cytokine production in a murine model of fungal allergic asthma

Allergic asthma is a chronic inflammatory disease of the airways characterized by excessive eosinophilic and lymphocytic inflammation with associated changes in the extracellular matrix (ECM) resulting in airway wall remodeling. Hyaluronan (HA) is a nonsulfated glycosaminoglycan ECM component that functions as a structural cushion in its high molecular mass (HMM) but has been implicated in metastasis and other disease processes when it is degraded to smaller fragments. However, relatively little is known about the role HA in mediating inflammatory responses in allergy and asthma. In the present study, we used a murine Aspergillus fumigatus inhalational model to mimic human disease. After observing in vivo that a robust B cell recruitment followed a massive eosinophilic egress to the lumen of the allergic lung and corresponded with the detection of low molecular mass HA (LMM HA), we examined the effect of HA on B cell chemotaxis and cytokine production in the ex vivo studies. We found that LMM HA functioned through a CD44-mediated mechanism to elicit chemotaxis of B lymphocytes, while high molecular mass HA (HMM HA) had little effect. LMM HA, but not HMM HA, also elicited the production of IL-10 and TGF-β1 in these cells. Taken together, these findings demonstrate a critical role for ECM components in mediating leukocyte migration and function which are critical to the maintenance of allergic inflammatory responses.

B lymphocytes regulate airway granulocytic inflammation and cytokine production in a murine model of fungal allergic asthma

Sensitization to fungi often leads to a severe form of asthma that is particularly difficult to manage clinically, resulting in increased morbidity and hospitalizations in these patients. Although B lymphocytes might exacerbate asthma symptoms through the production of IgE, these cells might also be important in the protective response against inhaled fungi. Through cytokine release and T-cell interactions, these lymphocytes might also influence the development and maintenance of airway wall fibrosis. J(H)(-/-) mice lack the JH gene for the heavy chain component of antibodies, which is critical for B-cell function and survival. These animals have facilitated the elucidation of the role of B lymphocytes in a number of immune responses; however, J(H)(-/-) mice have not been used to study fungal allergy. In this study, we examined the role of B lymphocytes using an Aspergillus fumigatus murine fungal aeroallergen model that mimics human airway disease that is triggered by environmental fungal exposure. We compared disease progression in sensitized wild-type BALB/c and J(H)(-/-) mice that were exposed to repeated fungal exposure and found no differences in airway hyperresponsiveness, overall pulmonary inflammation or collagen deposition around the large airways. However, the levels of the Th2-type cytokines IL-4 and IL-13 were significantly attenuated in the airways of J(H)(-/-) mice relative to the BALB/c controls. By contrast, levels of the inflammatory cytokines IL-17A and IL-6 were significantly elevated in the J(H)(-/-) animals, and there was significantly more robust airway eosinophilia and neutrophilia than in control animals. Taken together, these findings demonstrate that B lymphocytes help to regulate granulocytic responses to fungal exposure in the pulmonary compartment.

Nucleotide oligomerization domain 1 ligation suppressed murine allergen-specific T-cell proliferation and airway hyperresponsiveness

The cytosolic nucleotide oligomerization domain (NOD)-like receptors NOD1 and NOD2 are important contributors to the intracellular recognition of pathogens including Chlamydophila pneumoniae, but little is known about their influence on allergen-induced airway inflammation. In BALB/c mice, we observed that infection with C. pneumoniae before systemic sensitization with ovalbumin (OVA) and local OVA airway exposure diminished airway hyperresponsiveness (AHR). Thus, the impact of the NOD1 agonist FK156 and the NOD2 agonist muramyl dipeptide given 6 hours before each sensitization or airway challenge was evaluated regarding AHR, OVA-specific plasma immunoglobulins, bronchoalveolar lavage fluid differentials, and cytokines. Spleen dendritic cells of FK156-treated mice were isolated and cocultured with OVA-specific T cells isolated from DO11.10 mice, and T-cell proliferation was quantified after OVA restimulation. T-cell proliferation was investigated in vivo in lungs and lymph nodes of FK156-treated and OVA-exposed DO11.10 mice. FK156, but not muramyl dipeptide, reduced AHR and pulmonary eosinophilic infiltration if given before OVA sensitization or challenge, whereas T-helper (Th)2 cytokines were not diminished. Dendritic cells from FK156-treated mice evoked less OVA-specific T-cell proliferation as compared with solvent-treated controls. Similarly, antigen-specific T-cell activation in lung tissue was diminished after FK156 treatment. We conclude that NOD1 activation reduced AHR in allergen-induced lung inflammation, which was accompanied by a reduction of allergen-specific T-cell proliferation.

Lymphocyte-based model systems for allergy research: a historic overview

During the last decades, a multitude of studies applying distinct in vitro and in vivo model systems have contributed greatly to our better understanding of the initiation and regulation of inflammatory processes leading to allergic diseases. Over the years, it has become evident that among lymphocytes, not only IgE-producing B cells and allergy-orchestrating CD4(+) helper cells but also cytotoxic CD8(+) T cells, γδ-T cells and innate lymphoid cells, as well as regulatory lymphocytes, might critically shape the immune response towards usually innocuous allergens. In this review, we provide a historic overview of pioneering work leading to the establishment of important lymphocyte-based model systems for allergy research. Moreover, we contrast the original findings with our currently more refined knowledge to appreciate the actual validity of the respective models and to reassess the conclusions obtained from them. Conflicting studies and interpretations are identified and discussed. The tables are intended to provide an easy overview of the field not only for scientists newly entering the field but also for the broader readership interested in updating their knowledge. Along those lines, herein we discuss in vitro and in vivo approaches to the investigation of lymphocyte effector cell activation, polarization and regulation, and describe depletion and adoptive transfer models along with gene knockout and transgenic (tg) methodologies. In addition, novel attempts to establish humanized T cell antigen receptor tg mouse models for allergy research are described and discussed.

Immunologic effector mechanisms in animal models of occupational asthma

Occupational asthma is a form of immunotoxicity resulting from an exaggerated immune response to substances encountered in the workplace. Symptoms include reversible airway obstruction, airway hyperresponsiveness, airway remodeling, mucus production and cellular infiltration into the lung, particularly eosinophilia. The asthmatic response is divided into the induction phase, occurring after initial exposure to allergen, followed by the effector phase where a subsequent exposure to the allergen results in the respiratory symptoms. Animal models have been used to investigate the asthmatic response and this review will focus on mechanistic studies of the effector phase. Variables that may impact the effector phase include strain and species of animal, dose of allergen, route of exposure, and developmental stage of the animal. Both trimellitic anhydride (TMA) and ovalbumin are known causes of occupational asthma. Ovalbumin is also a reference protein allergen in immunology, and TMA is used as a prototype of a low molecular weight respiratory allergen. Differences in effector mechanisms for TMA and ovalbumin have been noted in different animal models. Studies in the guinea pig provide the most direct comparisons of effector mechanisms of TMA and ovalbumin, with differences in the role of the complement system and arachidonate metabolites being noted. Besides the guinea pig, the Brown Norway rat, and various mouse strains provide useful asthma models for TMA and ovalbumin. However, studies of effector mechanisms are somewhat lacking in either of these species using TMA as the allergen. Continued studies are indicated to determine if unique effector mechanisms can be identified for the many different causes of occupational asthma.

μ-chain-deficient mice possess B-1 cells and produce IgG and IgE, but not IgA, following systemic sensitization and inhalational challenge in a fungal asthma model

Allergic bronchopulmonary aspergillosis is often difficult to treat and results in morbidity associated with chronic airway changes. This study assessed the requirement for B cells and their products in the allergic pulmonary phenotype in a murine model of fungal allergic asthma that mimics allergic bronchopulmonary aspergillosis. C57BL/6 and μMT mice (assumed to lack peripheral B cells) were sensitized with Aspergillus fumigatus extract and challenged with two inhalation exposures of live conidia to induce airway disease. Airway hyperresponsiveness after methacholine challenge, peribronchovascular inflammation, goblet cell metaplasia, and fibrotic remodeling of the airways was similar between μMT mice and their wild-type counterparts (C57BL/6). Surprisingly, even in the absence of the μ-chain, these μMT mice produced IgE and IgG Abs, although the Abs induced did not have specificity for A. fumigatus Ags. In contrast, IgA was not detected in either the lavage fluid or serum of μMT mice that had been exposed to A. fumigatus. Our findings also reveal the existence of CD19(+)CD9(+)IgD(+) B-1 cells in the lungs of the μMT animals. These data show the μMT mice to have a developmental pathway independent of the canonical μ-chain route that allows for their survival upon antigenic challenge with A. fumigatus conidia, although this pathway does not seem to allow for the normal development of Ag-specific repertoires. Additionally, this study shows that IgA is not required for either clearance or containment of A. fumigatus in the murine lung, as fungal outgrowth was not observed in the μMT animals after multiple inhalation exposures to live conidia.

RNA interference in vitro and in vivo using DsiRNA targeting the nucleocapsid N mRNA of human metapneumovirus

Human metapneumovirus causes respiratory diseases with outcomes that can be severe in children, the immunocompromised, and the elderly. Synthetic small interfering RNAs (siRNAs) that silence targeted genes can be used as therapeutic agents. Currently, there is no specific therapy for hMPV. In this study, we designed Dicer-substrate siRNAs (DsiRNAs) that target metapneumovirus sequences on the mRNAs of the N, P, and L genes. In vitro, six DsiRNAs were shown to inhibit virus replication using cell proliferation tests. Of those, the DsiRNA that targets the most conserved mRNA sequence was then resynthesized in Evader™ format with heavy 2'-O-methyl modification of the guide strand. In a murine model, the prophylactic administration of this Evader™ DsiRNA was effective at partially inhibiting viral replication of hMPV (13×10(3) vs. 29×10(3)PFU/g of lung; p<0.01), which was not the case for the control, a mismatched DsiRNA. Inhibition was achieved without inducing cytokines or off-target effects. Moreover, the specificity of the siRNA mechanism of action was demonstrated in vitro and in vivo using 5'-RACE methodology. This in vivo approach of using a DsiRNA against hMPV is an important step in the development of synthetic siRNA as a therapeutic agent for this virus.

Effects of systemic versus local administration of corticosteroids on mucosal tolerance

Respiratory exposure to allergen induces T cell tolerance and protection against the development of airway hyperactivity in animal models of asthma. Whereas systemic administration of dexamethasone during the delivery of respiratory Ag has been suggested to prevent the development of mucosal tolerance, the effects of local administration of corticosteroids, first-line treatment for patients with bronchial asthma, on mucosal tolerance remain unknown. To analyze the effects of systemic versus local administration of different types of corticosteroids on the development of mucosal tolerance, mice were exposed to respiratory allergen to induce mucosal tolerance with or without systemic or intranasal application of different doses of dexamethasone or prednisolone. After the induction of mucosal tolerance, proliferation of T cells was inhibited in tolerized mice, whereas systemic applications of corticosteroids restored T cell proliferation and secretion of Th2 cytokines. In contrast, inhaled corticosteroids showed no effect on both T cell proliferation and cytokine secretion. In addition, mice systemically treated with corticosteroids showed an increased airway hyperactivity with a significant lung inflammation, but also an increased T effector cells/regulatory T cells ratio in the second lymphoid organs when compared with mice that receive corticosteroids by inhalation. These results demonstrate that local administration of corticosteroids has no effect on the development of immune tolerance in contrast to systemically applied corticosteroids. Furthermore, although different concentrations of corticosteroids are administered to patients, our results demonstrated that the route of administration rather than the doses affects the effect of corticosteroids on respiratory tolerance induction. Considering the broad application of corticosteroids in patients with allergic disease and asthma, the route of administration of steroid substances seems crucial in terms of treatment and potential side effects. These findings may help elucidate the apparently contradicting results of corticosteroid treatment in allergic diseases.

B lymphocytes in inflammatory airway diseases

B lymphocytes are key players in all facets of adaptive immune responses and are responsible for the production of IgE antibodies, initiators of allergic hypersensitivity reactions. Recent evidence indicates that B cells may be a crucial player in allergic and inflammatory airway pathology, directly populating upper and lower airway tissues. This review examines human and animal studies that directly demonstrated the presence of B lymphocytes in airway tissues and elaborates on their function as antibody-secreting cells, antigen-presenting cells and producers of inflammatory and regulatory cytokines. B lymphocytes appear to contribute to multiple facets of immune homeostasis in inflammatory diseases of the upper and lower airways.

Treatment of cocaine abuse during pregnancy: translating research to clinical practice

In the late-1980s and early-1990s, much attention in America was focused on cocaine abuse. In particular, the effects of prenatal cocaine use on mothers and infants were in the news spotlight. Risks of adverse effects prompted funding for novel treatment programs. More recently, media attention has shifted elsewhere, and specialized treatment resources have grown scarce. This redirection of funding is unfortunate, as social stigma and fear of legal consequences continue to encourage cocaine-abusing pregnant women to hide drug use and avoid prenatal care. The purpose of this article is to summarize the most prominent adverse maternal and fetal/infant effects associated with prenatal cocaine use; review treatment options, focusing on comprehensive care programs of the 1990s as well as recent research on evidence-based practices and their applicability to pregnant women; and highlight the population of prenatal cocaine-abusing women uninterested in treatment, with a focus on promising strategies to promote drug abstinence and other positive health behaviors.

Preclinical animal models of asthma and chronic obstructive pulmonary disease

Animal models of disease serve a vital function in the search for novel therapeutic approaches. While these systems cannot replicate human disease, they can be used to mimic and investigate mechanisms believed to be central to disease pathogenesis. In this review, we discuss the most relevant and commonly used animal models for asthma and chronic obstructive pulmonary disease (COPD); specifically, models developed for the mouse, rat and guinea pig. Allergens, such as ovalbumin, can be used to induce an IgE-dependent response characterized by early- and late-phase bronchoconstriction, inflammation and airway hyper-responsiveness similar to what occurs in asthmatics. Similarly, elastase and cigarette smoke can be used to replicate steroid-insensitive and progressive inflammation, which leads to lung pathologies that are observed in COPD patients. We also discuss how these models are developing in new ways to more closely reflect the clinical disease. Unfortunately, these models have limitations due to differences in genetics, anatomy and physiology among the species, many of which we have highlighted; however, understanding these differences, careful characterization of these models and parallel in vitro or ex vivo studies using human and relevant animal tissues will overcome some of these issues. In spite of these limitations, as long as studies are designed and interpreted appropriately, in vivo models will continue to be vital for furthering our understanding of disease pathogenesis and for developing new therapies.

Protease inhibitors in respiratory disease: focus on asthma and chronic obstructive pulmonary disease

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are a major health burden on society and current treatment modalities for these diseases have not significantly changed over the past 40 years. The only major pharmacological advancement for the treatment of these diseases has been to increase the duration of action of bronchodilators (asthma: salmeterol; COPD: tiotropium bromide) and glucocorticosteroids (asthma: fluticasone propionate) and, increasingly, to formulate these agents in the same delivery device. Despite our increasing understanding of the cell and molecular biology of these diseases, the development of novel treatments remains beyond the reach of the scientific community. Proteases are a family of proteins with diverse biological activity, which are found in abundance within the airways of asthma and COPD, and have been implicated in the pathogenesis of these diseases. The targeting of proteases, including mast cell tryptase, neutrophil elastase and matrix metalloprotease with low-molecular-weight inhibitors, has highlighted the potential role of these enzymes in mediating certain aspects of the disease process in preclinical studies. Several challenges remain regarding the development of protease inhibitors, including the synthesis of highly potent and specific inhibitors, and target validation in man.

Glutathione peroxidase-2 protects from allergen-induced airway inflammation in mice

The aim of the present study was to identify and validate the biological significance of new genes/proteins involved in the development of allergic airway disease in a murine asthma model. Gene microarrays were used to identify genes with at least a two-fold increase in gene expression in lungs of two separate mouse strains with high and low allergic susceptibility. Validation of mRNA data was obtained by western blotting and immunohistochemistry, followed by functional analysis of one of the identified genes in mice with targeted disruption of specific gene expression. Expression of two antioxidant enzymes, glutathione peroxidase-2 (GPX2) and glutathione S-transferase omega (GSTO) 1-1 was increased in both mouse strains after induction of allergic airway disease and localised in lung epithelial cells. Mice with targeted disruption of the Gpx-2 gene showed significantly enhanced airway inflammation compared to sensitised and challenged wild-type mice. Our data indicate that genes encoding the antioxidants GPX2 and GSTO 1-1 are common inflammatory genes expressed upon induction of allergic airway inflammation, and independently of allergic susceptibility. Furthermore, we provide evidence to illustrate the importance of a single antioxidant enzyme, GPX2, in protection from allergen-induced disease.

Similar response in male and female B10.RIII mice in a murine model of allergic airway inflammation

BACKGROUND

Several reports have been published on the gender differences associated with allergies in mice.

GOAL

In the present study we investigate the influence of gender on allergy response using a strain of mice, B10.RIII, which is commonly used in the collagen-induced arthritis murine model.

METHODS

Both male and female B10.RIII young mice were immunized with OVA and challenged four times with OVA intranasally. Samples were taken 24 h after the last challenge, and eosinophils in bronchoalveolar lavage (BAL) and parenchyma, Th-2 cytokines in BAL, total and antigen-specific IgE in sera, and antigen-specific T-cell proliferation were measured.

RESULTS

Immunization in both male and female B10.RIII mice with OVA elicited a classical Th2-type response. Results showed no significant differences among male and female mice. Also a high eosinophilia in BAL fluid and parenchyma was produced in both genders without any significant differences. However, the deviation of both parameters was higher in young males compared to young females.

CONCLUSIONS

Gender differences, classically associated with some strains of mice, are not reproducible in B10.RIII mice. Gender differences in murine models of allergic airway inflammation are probably strain-dependent.

Breastmilk from allergic mothers can protect offspring from allergic airway inflammation

OBJECTIVE

Breastfeeding is associated with a reduced risk of developing asthma in children. Using a murine model we previously demonstrated that mothers with Th1-type immunity to ovalbumin (OVA) transfer antigen-specific protection from OVA-induced allergic airway disease (AAD) to their offspring. The aim of this study was to evaluate the contribution of breastmilk and maternal B cell immunity from allergic mothers in the vertical transmission of protection from AAD.

METHODS

This was investigated using an adoptive nursing strategy. Naive offspring were nursed by allergic wild-type or B cell-deficient foster mothers with histories of Th2-type immunity to OVA. Following weaning, offspring were immunized with OVA-Al(OH)(3) and challenged with aerosolized OVA to induce AAD.

RESULTS

Offspring nursed by wild-type OVA-immune foster mothers demonstrated lower levels of OVA-specific immunoglobulin E, interleukin-5, and airway eosinophilia than progeny nursed by naive control mothers. In contrast, offspring nursed by B cell-deficient OVA-immune foster mothers had similar parameters of OVA-induced AAD as progeny nursed by naive control mothers.

CONCLUSIONS

These data demonstrate the ability of breastmilk from allergic mothers to protect offspring from AAD was dependent on intact maternal B cell immunity. Nursing alone, when done by wild-type mothers with AAD, was sufficient for offspring to acquire the antigen-specific protective factor(s) from breastmilk.

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.

Airway hyperresponsiveness through synergy of gammadelta} T cells and NKT cells

Mice sensitized and challenged with OVA were used to investigate the role of innate T cells in the development of allergic airway hyperresponsiveness (AHR). AHR, but not eosinophilic airway inflammation, was induced in T cell-deficient mice by small numbers of cotransferred gammadelta T cells and invariant NKT cells, whereas either cell type alone was not effective. Only Vgamma1+Vdelta5+ gammadelta T cells enhanced AHR. Surprisingly, OVA-specific alphabeta T cells were not required, revealing a pathway of AHR development mediated entirely by innate T cells. The data suggest that lymphocytic synergism, which is key to the Ag-specific adaptive immune response, is also intrinsic to T cell-dependent innate responses.

Mast cell-derived TNF contributes to airway hyperreactivity, inflammation, and TH2 cytokine production in an asthma model in mice

BACKGROUND

Mast cells, IgE, and TNF, which have been implicated in human atopic asthma, contribute significantly to the allergic airway inflammation induced by ovalbumin (OVA) challenge in mice sensitized with OVA without alum. However, it is not clear to what extent mast cells represent a significant source of TNF in this mouse model.

OBJECTIVE

We investigated the importance of mast cell-derived TNF in a mast cell-dependent model of OVA-induced airway hyperreactivity (AHR) and allergic airway inflammation.

METHODS

Features of this model of airway inflammation were analyzed in C57BL/6J-wild-type mice, mast cell-deficient C57BL/6J-Kit(W-sh)(/W-sh) mice, and C57BL/6J Kit(W-sh/W-sh) mice that had been systemically engrafted with bone marrow-derived cultured mast cells from C57BL/6J-wild-type or C57BL/6J-TNF(-/-) mice.

RESULTS

Ovalbumin-induced AHR and airway inflammation were significantly reduced in mast cell-deficient Kit(W-sh/W-sh) mice versus wild-type mice. By contrast, Kit(W-sh/W-sh) mice that had been engrafted with wild-type but not with TNF(-/-) bone marrow-derived cultured mast cells exhibited responses very similar to those observed in wild-type mice. Mast cells and mast cell-derived TNF were not required for induction of OVA-specific memory T cells in the sensitization phase, but significantly enhanced lymphocyte recruitment and T(H)2 cytokine production in the challenge phase.

CONCLUSION

Mast cell-derived TNF contributes significantly to the pathogenesis of mast cell-dependent and IgE-dependent, OVA-induced allergic inflammation and AHR in mice, perhaps in part by enhancing lymphocyte recruitment and T(H)2 cytokine production.

CLINICAL IMPLICATIONS

Our findings in mice support the hypothesis that mast cell-derived TNF can promote allergic inflammation and AHR in asthma.

Interleukin-16 Inhibits Immunoglobulin E Production by B Lymphocytes

BACKGROUND

The increased production of IgE is a hallmark of atopic disorders. CD4+ T cells regulate the production of Immunoglobulin (Ig) E by B cells. Interleukin (IL) 16, a CD4+ specific cytokine, is highly expressed at sites of allergic inflammation. Our aim was to determine the effect of IL-16 on IgE production in atopic subjects.

METHODS

Freshly isolated peripheral blood mononuclear cells (PBMC) from atopic subjects were stimulated with recombinant IL (rIL) 4 and anti-CD40 antibody to promote IgE production in the presence or absence of rIL-16 added at different time intervals prior to stimulation. The levels of IgE in cell culture supernatants collected at day 14 were measured by ELISA. The effect of IL-16 on the expression of the Cepsilon transcript was evaluated by reverse-transcription polymerase chain reaction. To evaluate whether the modulatory effect of IL-16 on IgE production was mediated by interferon-gamma (IFN-gamma), anti-CD40/IL-4-stimulated PBMC were cultured in the presence of rIL-16 and neutralizing concentrations of anti-IFN-gamma antibody.

RESULTS

PBMC stimulated with rIL-4 (400 U/ml) and anti-CD40 monoclonal antibody (0.5 microg/ml) produced significant amounts of IgE (range: 1.3-46.0 ng/ml). The addition of rIL-16 twenty-four hours before stimulation significantly reduced the levels of IgE released by anti-CD40/IL-4-stimulated PBMC (0.5-29.6 ng/ml, p < 0.05). IL-16 reduced the expression of the Cepsilon transcript in stimulated PBMC. IL-16 induced the expression of IFN-gamma mRNA. However, the use of anti-IFN-gamma antibody did not alter the effect of IL-16 on IgE production. Rescue doses of IL-13 did not restore the production of IgE by PBMC treated with IL-16. IL-16 did not alter IgE production in CD14-depleted cell preparations suggesting that the IL-16-mediated effects on IgE production may be related to CD14+ cells.

CONCLUSION

These data show that IL-16 inhibits IgE production and therefore may play an important regulatory role in atopic disorders.

4-1 BB stimulation inhibits allergen-specific immunoglobulin E production and airway hyper-reactivity but partially suppresses bronchial eosinophilic inflammation in a mouse asthma model

BACKGROUND

4-1 BB, a member of the tumour necrosis factor receptor superfamily, functions as a co-stimulatory molecule. Recently, stimulation of the 4-1 BB pathway was shown to suppress antigen-specific CD4(+) T cell and subsequent T cell-dependent humoral immune responses.

OBJECTIVE

We examined the effect of agonistic anti-4-1 BB monoclonal antibody (mAb) treatment on allergic asthma, in which allergen-specific type 2 helper T cells (Th2) have been shown to play an important role.

METHODS

BALB/c mice were systemically sensitized with intraperitoneal injections of ovalbumin (OVA) and alum on days 0 and 14, and then challenged with inhaled OVA on days 28, 29 and 30. In test groups, the agonistic anti-4-1 BB mAb was administered at the time of initial systemic sensitization with OVA. On day 31, mice were challenged with inhaled methacholine, and enhanced pause was measured as an index of airway hyper-responsiveness (AHR). Levels of OVA-specific IgE in serum, and levels of various cytokines in bronchoalveolar lavage (BAL) fluids were measured. The severity of airway inflammation was determined by differential cell counts in BAL fluids and histopathologic lung analysis. To evaluate local immunity, we cultured lymphocytes from draining perihilar lymph nodes and evaluated the proliferative response to OVA and the levels of IL-5 in the culture supernatant. In addition, the functional mechanism of 4-1 BB stimulation was evaluated in splenocytes obtained at day 7 after systemic OVA sensitization.

RESULTS

We found that treatment with the anti-4-1 BB mAb significantly decreased AHR and the production of allergen-specific IgE. Bronchial inflammation, however, had only partially improved and the levels of IL-4 and IL-5 in BAL fluids showed only a small degree of reduction compared with the control Ig-treated mice. Thoracic lymphocytes from anti-4-1 BB-treated mice showed significant suppression of OVA-induced proliferation and IL-5 production. In anti-4-1 BB-treated mice, splenocytes exhibited poor proliferation and marked apoptosis 7 days after systemic OVA challenge.

CONCLUSION

These results suggest that stimulation of the 4-1 BB pathway effectively suppresses some features of allergic asthma, including allergen-specific IgE production and AHR, through deletion of allergen-specific Th2 cells. However, we found that bronchial allergic inflammation was not strictly mediated by suppression of the Th2 immune response in this murine model of asthma. Despite these somewhat contradictory effects, intervention in the 4-1 BB pathway might provide a potential novel immunotherapeutic approach for treatment of allergic asthma.

Targeting cytosolic phospholipase A2 by arachidonyl trifluoromethyl ketone prevents chronic inflammation in mice

Cytosolic phospholipase A(2) (cPLA(2)) plays a pivotal role in inflammation by catalyzing the release of arachidonic acid, a substrate for lipoxygenase and cyclooxygenase enzymes, from membrane phospholipids. In the present study we examined the role of cPLA(2) in inflammatory responses through the use of a specific inhibitor of the enzyme, cPLA(2), arachidonyl trifluoromethyl ketone (AACOCF3). Interestingly, we observed that AACOCF3 is an inhibitor of chronic but not acute inflammatory responses. Specifically, AACOCF3 inhibited phorbol 12-myristate 13-acetate (PMA)-induced chronic ear edema in mice. Additionally, oral treatment of ovalbumin-sensitized/ovalbumin-challenged BALB/c mice with 20 mg/kg AACOCF3 prevented the development of airway hyper-responsiveness in a model of asthma. Furthermore, AACOCF3 decreased cellular recruitment in the airway lumen and airway inflammation after the ovalbumin challenge. Taken together, these results suggest that a potent and specific chemical inhibitor of cPLA(2) may be useful for the treatment of chronic inflammatory diseases including rheumatoid arthritis, inflammatory bowel disease, psoriasis, and asthma.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.

Oral administration of desloratadine prior to sensitization prevents allergen-induced airway inflammation and hyper-reactivity in mice

BACKGROUND

Histamine-1-receptor (H1R)-antagonists were shown to influence various immunological functions on different cell types and may thus be employed for immune-modulating strategies for the prevention of primary immune responses.

OBJECTIVE

The aim of this study was to investigate the effects of an H1R-antagonist on allergen-induced sensitization, airway inflammation (AI) and airway hyper-reactivity (AHR) in a murine model.

METHODS

BALB/c mice were systemically sensitized with ovalbumin (OVA) (six times, days 1-14) and challenged with aerosolized allergen (days 28-30). One day prior to the first and 2 h prior to every following sensitization, mice received either 1 or 0.01 microg of desloratadine (DL) or placebo per os.

RESULTS

Sensitization with OVA significantly increased specific and total IgE and IgG1 serum levels, as well as in vitro IL-5 and IL-4 production by spleen and peribronchial lymph node (PBLN) cells. Sensitized and challenged mice showed a marked eosinophilic infiltration in broncho-alveolar lavage fluids and lung tissues, and developed in vivo AHR to inhaled methacholine. Oral treatment with DL prior to OVA sensitization significantly decreased production of OVA-specific IgG1, as well as in vitro Th2-cytokine production by spleen and PBLN cells, compared with OVA-sensitized mice. Moreover, eosinophilic inflammation and development of in vivo AHR were significantly reduced in DL-treated mice, compared with sensitized controls.

CONCLUSION

Treatment with H1R-anatagonist prior to and during sensitization suppressed allergen-induced Th2 responses, as well as development of eosinophilic AI and AHR. This underscores an important immune modulating function of histamine, and implies a potential role of H1R-anatagonists in preventive strategies against allergic diseases.

Increased airway responsiveness, allergy-type-I skin responses and systemic anaphylaxis in a humanized-severe combined immuno-deficiency mouse model

BACKGROUND

In patients with allergic bronchial asthma, a strong relationship between elevated serum IgE antibody titres and the development of increased airway responsiveness (AR) has been demonstrated. To further elucidate the relationship between human (hu) IgE and development of increased AR, we developed an in vivo model utilizing immuno-compromised severe combined immuno-deficiency (SCID) mice.

METHODS

SCID mice were either reconstituted with peripheral blood mononuclear cells (PBMC) from non-atopic, healthy or atopic individuals sensitized against house dust mite allergen (Der p), or passively sensitized with plasma from non-atopic, healthy or atopic individuals.

RESULTS

In both systems, atopic hu-SCID mice developed increased AR. The following results suggest that these responses were mediated via IgE antibodies: increased AR did not occur after transfer of either PBMC or IgE-negative plasma from non-atopic individuals; increased AR occurred simultaneous with increased serotonin release detected 15 min after allergen-aerosol challenge in bronchoalveolar lavage fluid; and increased AR required at least two allergen-aerosol challenges. SCID mice reconstituted with serum containing anti-Der p IgE antibodies developed positive immediate-type skin test responses to intradermal injection of Der p as well as anti-hu-IgE antibody. In addition, IgE binding to skin mast cells was demonstrated by immunohistochemistry. Furthermore, intravenous challenge of hu anti-Der p positive SCID mice with Der p resulted in systemic anaphylaxis.

CONCLUSION

These data provide evidence that passive immunization of SCID mice with hu IgE alters AR and that T cells and eosinophils were not a requirement for the development of increased AR in this model.

Mast Cells, FcεRI, and IL-13 Are Required for Development of Airway Hyperresponsiveness after Aerosolized Allergen Exposure in the Absence of Adjuvant

In certain models of allergic airway disease, mast cells facilitate the development of inflammation and airway hyper-responsiveness (AHR). To define the role of the high affinity IgE receptor (FcepsilonRI) in the development of AHR, mice with a disruption of the alpha subunit of the high affinity IgE receptor (FcepsilonRI(-/-)) were exposed on 10 consecutive days to nebulized OVA. Forty-eight hours after the last nebulization, airway responsiveness was monitored by the contractile response of tracheal smooth muscle to electrical field stimulation (EFS). After the 10-day OVA challenge protocol, wild-type mice demonstrated increased responsiveness to EFS, whereas similarly challenged FcepsilonRI(-/-) mice showed a low response to EFS, similar to nonexposed animals. Further, allergen-challenged FcepsilonRI(-/-) mice showed less airway inflammation, goblet cell hyperplasia, and lower levels of IL-13 in lung homogenates compared with the controls. IL-13-deficient mice failed to develop an increased response to EFS or goblet cell hyperplasia after the 10-day OVA challenge. We transferred bone marrow-derived mast cells from wild-type mice to FcepsilonRI(-/-) mice 1 day before initiating the challenge protocol. After the 10-day OVA challenge, recipient FcepsilonRI(-/-) mice demonstrated EFS-induced responses similar to those of challenged wild-type mice. Transferred mast cells could be detected in tracheal preparations. These results show that FcepsilonRI is important for the development of AHR after an aerosolized allergen sensitization protocol and that this effect is mediated through FcepsilonRI on mast cells and production of IL-13 in the lung.

Gender comparison in a murine model of allergen-driven airway inflammation and the response to budesonide treatment

Background

Evidence suggests that gender differences exist in the severity of many immunological diseases and their response to glucocorticosteroid treatment. In this report, we have used a murine model of ovalbumin-induced lung inflammation to address whether gender could affect the systemic response, airway inflammation and hyperreactivity and their responses to budesonide.

Results

Following an acute ovalbumin challenge, actively sensitised BALB/c mice developed a time-dependent increase in interleukin-4 and interleukin-5 production and inflammatory cell influx into bronchoalveolar lavage fluid. Apart from an increased number of lymphocytes in female mice at day 3 post-challenge, none of the above parameters were affected by gender. Blood leukocyte numbers were also unaffected, whereas a two-fold increase in total serum immunoglobulin E was observed in female mice. Budesonide, given intranasally, did not affect the blood parameters, but dose-dependently inhibited the pulmonary inflammation and airway hyperreactivity in both male and female mice. Female mice were slightly less sensitive to budesonide's inhibitory action on interleukin-5 production and the development of airway hyperreactivity.

Conclusions

Our results suggest that, apart from a 2-fold increase in serum immunoglobulin E levels observed in female mice, gender is not a major factor in the present murine model of ovalbumin-induced lung inflammation. In contrast, gender might slightly influence the potency of test compounds such as steroids.

Chronic inhaled ovalbumin exposure induces antigen-dependent but not antigen-specific inhalational tolerance in a murine model of allergic airway disease

Sensitized mice acutely challenged with inhaled ovalbumin (OVA) develop allergic airway inflammation, characterized by OVA-specific IgE production, airway eosinophilia, increased pulmonary B and T lymphocytes, and airway hyperreactivity. In this study, a chronic exposure model was developed and two distinct patterns of response were observed. Discontinuous inhalational exposure to OVA (6 weeks) produced airway inflammation and hyperreactivity that were similar to acute (10 days) responses. Continuous inhalational exposure to OVA (6 or 11 weeks) resulted in attenuation of airway eosinophilia and hyperresponsiveness without reduction of OVA-specific IgE and IgG(1) levels. The inhibition of airway inflammation was dependent on continuous exposure to antigen, because continuously exposed mice with attenuated inflammatory responses redeveloped allergic airway disease if the OVA aerosols were interrupted and then restarted (11-week-discontinuous). Inhalational tolerance induced by continuous OVA exposure demonstrated bystander suppression of cockroach allergen-mediated airway eosinophilia. These findings may be attributed to changes in production of the anti-inflammatory cytokine interleukin-10 during continuous OVA aerosol exposure. The symptomatic and asymptomatic allergic responses in human asthmatics could be explained by similar variable or discontinuous exposures to aeroantigens.

Short-term smoke exposure attenuates ovalbumin-induced airway inflammation in allergic mice

Little is known about effects of smoking on airway inflammation in asthma. We tested the hypothesis that smoking enhances established airway inflammation in a mouse model of allergic asthma. C57Bl/6j mice were sensitized to ovalbumin (OVA) and challenged with OVA (OVA-mice) or sham-sensitized to phosphate-buffered saline (PBS) and challenged with PBS aerosols (PBS-mice) for 7 wk. At 4 wk, mice were additionally exposed to air (nonsmoking controls) or mainstream smoke for 3 wk. Using whole body plethysmography, we found OVA-induced bronchoconstriction to be significantly inhibited in smoking OVA-mice as compared with nonsmoking OVA-mice (1 +/- 2% increase versus 22 +/- 6% increase in enhanced pause, respectively). Smoking did not change airway hyperresponsiveness (AHR) to methacholine in PBS-mice, yet significantly attenuated AHR in OVA-mice 24 h after OVA challenge as compared with nonsmoking mice. This was accompanied by reduced eosinophil numbers in lung lavage fluid and tissue of smoking OVA-mice compared with nonsmoking OVA-mice. In contrast to our hypothesis, short-term smoking reduced responsiveness to OVA and methacholine in OVA-mice and decreased airway inflammation when compared with nonsmoking mice. This effect of smoking may be different for long-term smoking, in which remodeling effects of smoking can be expected to interrelate with remodeling changes caused by asthmatic disease.

Do mouse models of allergic asthma mimic clinical disease?

Experimental mouse models of allergic asthma established almost 10 years ago offered new opportunities to study disease pathogenesis and to develop new therapeutics. These models focused on the factors governing the allergic immune response, on modeling clinical behavior of allergic asthma, and led to insights into pulmonary pathophysiology. Although mouse models rarely completely reproduce all the features of human disease, after sensitization and respiratory tract challenges with antigen, wild-type mice develop a clinical syndrome that closely resembles allergic asthma, characterized by eosinophilic lung inflammation, airway hyperresponsiveness (AHR), increased IgE, mucus hypersecretion, and eventually, airway remodeling. There are, however, differences between mouse and human physiology that threaten to limit the value of mouse models. Three examples of such differences relate to both clinical manifestations of disease and underlying pathogenesis. First, in contrast to patients who have increased methacholine-induced AHR even when they are symptom-free, mice exhibit only transient methacholine-induced AHR following allergen exposure. Second, chronic allergen exposure in patients leads to chronic allergic asthma, whereas repeated exposures in sensitized mice causes suppression of disease. Third, IgE and mast cells, in humans, mediate early- and late-phase allergic responses, though both are unnecessary for the generation of allergic asthma in mice. Taken together, these observations suggest that mouse models of allergic asthma are not exact replicas of human disease and thus, question the validity of these models. However, observations from mouse models of allergic asthma support many existing paradigms, although some novel discoveries in mice have yet to be verified in patients. This review presents an overview of the clinical aspects of disease in mouse models of allergic asthma emphasizing (1). the factors influencing the pathophysiological responses during the initiation and perpetuation of disease, (2). the utility of mouse models for studying clinical manifestations of disease, and (3). the applicability of mouse models for testing new treatments for allergic asthma.

Repeated aerosol allergen exposure suppresses inflammation in B-cell-deficient mice with established allergic asthma

BACKGROUND

Repeated allergen administration is a well-established therapeutic strategy for desensitizing patients with allergic disease. Similarly, repeated inhalation of antigen by mice with established allergen-induced asthma suppresses allergic inflammation. The mechanisms underlying antigen-dependent suppression of allergic immune responses remain unknown. In previous studies, we found that repeated aerosol antigen challenges in sensitized mice reduced eosinophils while increasing plasma cells and antibody in the lungs. We sought to test whether plasma cells and antibody played a role in suppression of allergic disease.

METHODS

We primed wild-type and B-cell-deficient (microMT) mice with 25 microg ovalbumin (OVA) precipitated in alum on days 0 and 5, nebulized weekly with 1% OVA, 1 h, twice daily, for up to 6 weeks, and assessed lung inflammation, mucus hypersecretion, and IgE/IgG1.

RESULTS

Kinetic studies revealed that initial aerosol exposure induced high numbers of eosinophils, lymphocytes, and macrophages within lung infiltrates and increased mucus production in wild-type mice. After 3-4 weeks of antigen exposure, eosinophils diminished while lymphocytes, plasma cells, and macrophages and mucus hypersecretion increased. However, by 6 weeks, lung inflammation and mucus hypersecretion were dramatically reduced. In contrast, repeated aerosol challenges maintained OVA-specific IgG1 and IgE production. Repeated aerosol antigen challenges in microMT mice resulted in reduced lung inflammation and mucus hypersecretion and the development of smooth muscle hypertrophy of the pulmonary microvasculature.

CONCLUSIONS

B cells and antibody do not appear to play a role in antigen-dependent suppression of allergic responses in mice.

Regulation of eosinophilopoiesis in a murine model of asthma

Eosinophilic inflammation plays a key role in tissue damage that characterizes asthma. Eosinophils are produced in bone marrow and recent observations in both mice and humans suggest that allergen exposure results in increased output of eosinophils from hemopoietic tissue in individuals with asthma. However, specific mechanisms that alter eosinophilopoiesis in this disease are poorly understood. The current study used a well-characterized murine animal model of asthma to evaluate alterations of eosinophil and eosinophil progenitor cells (CFU-eo) in mice during initial sensitization to allergen and to determine whether observed changes in either cell population were regulated by T lymphocytes. Following the first intranasal installation of OVA, we observed sequential temporal elevation of eosinophils in bone marrow, blood, and lung. In immunocompetent BALB/c mice, elevation of bone marrow eosinophils was accompanied by transient depletion of CFU-eo in that tissue. CFU-eo rebounded to elevated numbers before returning to normal baseline values following intranasal OVA exposure. In T cell-deficient BALB/c nude (BALB/c(nu/nu)) mice, CFU-eo were markedly elevated following allergen sensitization, in the absence of bone marrow or peripheral blood eosinophilia. These data suggest that eosinophilia of asthma results from alterations in two distinct hemopoietic regulatory mechanisms. Elevation of eosinophil progenitor cells in the bone marrow is T cell independent and likely results from altered bone marrow stromal cell function. Differentiation of eosinophil progenitor cells and phenotypic eosinophilia is T cell dependent and does not occur in athymic nude mice exposed to intranasal allergen.

Transient neutrophil infiltration after allergen challenge is dependent on specific antibodies and Fc gamma III receptors

Following allergen challenge of sensitized mice, neutrophils are the first inflammatory cells found in bronchoalveolar lavage (BAL) fluid. To determine the underlying mechanism for their accumulation, mice were sensitized to OVA on days 0 and 14, and received, on day 28, a single intranasal challenge (s.i.n.) with either OVA or ragweed. Eight hours after the s.i.n., BAL fluid was obtained. BALB/c mice sensitized and challenged with OVA showed significantly higher total cell counts and numbers of neutrophils in BAL fluid compared to the OVA-sensitized and ragweed-challenged or nonsensitized mice. Levels of neutrophil chemokines in BAL fluid supernatants were markedly elevated in the sensitized and OVA-challenged mice; Fc epsilon RI-deficient mice showed comparable numbers of neutrophils and neutrophil chemokines in BAL fluid after s.i.n. But in sensitized mice lacking the Fc common gamma-chain and B cell-deficient mice, the number of neutrophils and levels of neutrophil chemokines in BAL fluid were significantly lower. Further, mice lacking the FcgammaRIII did not develop this early neutrophil influx. Neutrophil infiltration could be induced in naive mice following intranasal instillation of allergen combined with allergen-specific IgG1. In addition, macrophages from sensitized mice were stimulated with allergen and activated to produce neutrophil chemokines. These results demonstrate that neutrophil influx after allergen challenge requires prior sensitization, is allergen-specific, is mediated through FcgammaRIII, and is dependent on the presence of Ab.

Upregulation of B7 molecules (CD80 and CD86) and exacerbated eosinophilic pulmonary inflammatory response in mice lacking the IFN-beta gene

BACKGROUND

IFN-beta has been shown to be effective as therapy for multiple sclerosis. Some reports attributed its beneficial effects to the capacity to induce a T(H)2 response. However, other studies have suggested that endogenous type I IFN might downregulate the allergic response in mice.

OBJECTIVE

We sought to define the differential role of endogenous IFN-beta in controlling the development of allergic inflammation.

METHODS

We assessed whether deletion of the gene encoding IFN-beta (IFNB) with knockout mice participated in the development of allergic response in ovalbumin (OVA)-sensitized and OVA-challenged mice.

RESULTS

OVA-sensitized and OVA-challenged mice with lack of the IFNB gene had more severe pulmonary inflammation with increased lung local response, including IL-4, IL-5, IL-13, IgE, eosinophilia, and goblet cells, than their litter mates (IFN-beta+/-), whereas no differences were observed in regard to local levels of IFN-gamma. Moreover, systemic response with IgE production is also enhanced. Lack of IFN-beta also results in significantly higher antigen-specific T cells, with higher levels of IL-4, IL-5, and IL-13, whereas no significant differences in IFN-gamma response could be observed. We have also detected a higher ratio of CD4+/CD8+ T cells and increased expression of B7.1/B7.2 on B cells and antigen-presenting cells in IFNB knockout mice.

CONCLUSIONS

These results demonstrate that IFN-beta plays an important role in immunoregulation of allergic response in mice. The stronger pulmonary inflammation could be a consequence of significantly expanded antigen-specific CD4+ T(H)2 cells as a result of efficient antigen presentation by antigen-presenting cells and hence increased production of IgE by B cells.

Kinetics of airway hyperresponsiveness and airway eosinophilia in BALB/c mice and their modulation by different dexamethasone treatment regimens

The mechanisms of airway hyperresponsiveness (AHR) are still poorly understood. In this study we have established a model of persistent AHR and eosinophilia and evaluated the prophylactic vs. therapeutic effects of dexamethasone on these parameters. Mice were immunised with ovalbumin (OVA) on day 0 and challenged intranasally on days 10, 11, 12 and 13 with OVA or phosphate buffer saline (PBS). Airway responsiveness to methacholine, measured 24-h post multiple intranasal OVA challenges, was significantly increased compared to time matched PBS-controls (P<0.05). AHR could be detected for up to 14 days after the last OVA challenge although the magnitude of the AHR had diminished by day 14 compared to day 1. OVA challenge of mice induced a significant airway eosinophilia at 24h (P<0.05); this persisted for 2 weeks after the challenge. Prophylactic treatment with dexamethasone (1mg x kg (-1)) reduced the OVA induced AHR, eosinophilia and mucus cell hyperplasia/metaplasia measured 24h post challenge. Therapeutic treatment, with dexamethasone (2 mg x kg(-1)), significantly inhibited established airway eosinophilia, measured at 72 h post OVA challenge, only when treatment was initiated at 24h but not 48 h after challenge. In contrast, AHR measured at 72 h post OVA challenge was significantly reduced when treatment was started at either 24 or 48 h post challenge. Our data shows that the immunization and challenge procedures employed resulted in a persistent type of AHR. Prophylactic intervention with steroids almost completely inhibited its development; however therapeutic intervention only partially resolved AHR.

Absence of immunoglobulin E synthesis and airway eosinophilia by vaccination with plasmid DNA encoding ProDer p 1

BACKGROUND

Various studies have shown that immunization with naked DNA encoding allergens induces T helper 1(Th1)-biased non-allergic responses.

OBJECTIVE

To evaluate the polarization of the immune responses induced by vaccinations with plasmid DNA encoding the major mite allergen precursor ProDer p 1.

METHODS

A DNA vaccine was constructed on the basis of a synthetic cDNA encoding ProDer p 1 with optimized codon usage. The immunogenicity of ProDer p 1 DNA in CBA/J mice was compared with that of purified natural Der p 1 or recombinant ProDer p 1 adjuvanted with alum. Vaccinated mice were subsequently exposed to aerosolized house dust mite extracts to provoke airway inflammation. The presence of inflammatory cells was examined in bronchoalveolar lavage (BAL) fluids and allergen-specific T cell reactivity was measured.

RESULTS

Naive mice immunized with ProDer p 1 DNA developed Th1 immune responses characterized by high titres of specific IgG2a antibodies, low titres of specific IgG1 and, remarkably, the absence of anti-ProDer p 1 IgE. No specific responses were observed in animals vaccinated with the blank DNA vector. By contrast, natural Der p 1 or recombinant ProDer p 1 adsorbed to alum induced pronounced Th2 allergic responses with strong specific IgG1 and IgE titres. Spleen cells from DNA ProDer p 1-vaccinated mice secreted high levels of IFN-gamma and low production of IL-5. Conversely, both adjuvanted allergens stimulated typical Th2-type cytokine profile characterized by high and low levels of IL-5 and IFN-gamma, respectively. Whereas BAL eosinophilia was clearly observed in Der p 1-immunized animals, ProDer p 1 DNA as well as ProDer p 1 vaccinations prevented airway eosinophil infiltrations.

CONCLUSIONS

These results suggest that vaccination with DNA encoding ProDer p 1 effectively fails to induce the allergen-induced IgE synthesis and airway cell infiltration. Plasmid DNA encoding ProDer p 1 may provide a novel approach for the treatment of house dust mite allergy.

gammadelta T cells contribute to the systemic immunoglobulin E response and local B-cell reactivity in allergic eosinophilic airway inflammation

Allergic airway inflammation induced in mice is T-cell dependent and recruitment of eosinophils to airspaces requires both alphabeta and gammadelta T cells. From previous studies it is evident that alphabeta T cells are essential for the allergic T helper type 2 (Th2)-like response, while the mechanistic contribution of gammadelta T cells is still unclear. In this study, we have investigated the role of gammadelta T cells in allergic airway eosinophilia induced by ovalbumin hypersensitivity. By comparing the responsiveness to sensitizing allergen of wild-type mice with that of T-cell receptor gammadelta knockout mice (TCRgammadelta KO) we demonstrated that mice lacking gammadelta T cells are defective in the systemic ovalbumin-specific immunoglobulin E (IgE) response. Furthermore, after aerosol challenge with allergen, gammadelta T-cell deficient mice exhibited a significantly decreased migration of B cells and natural killer cells to airways and reduced levels of allergen-specific IgG and IgA in bronchoalveolar lavage fluid. The role for B cells in the airway inflammation was indicated by the impaired ability of mice lacking functional B cells to evoke an eosinophilic response. The diminished eosinophilia in TCRgammadelta KO mice could not be explained by a defective Th2 activation since these mice displayed a normal IgG response in serum and an unaffected IG2b/IgG1 ratio in airways. Analysis of immunoregulatory cytokines in isolated lung tissue, thoracic lymph nodes and spleen further supported the notion that these mice are able to evoke a sufficient activation of T helper cells and that gammadelta T cells are not required for maintaining the Th2 profile. These results indicate that gammadelta T cells contribute to allergic airway inflammation by pathways separate from classical Th2 immune activation.

Animal models of allergic bronchopulmonary aspergillosis

Among the allergic fungi, Aspergillus fumigatus, a saprophytic mold, distributed widely in the environment is a frequently recognized etiologic agent in a number of allergic conditions. Among the different allergic diseases caused by this fungus, allergic bronchopulmonary aspergillosis (ABPA) is by far the most significant one. The immunopathogenesis of this disease is not fully understood. Although several immunomodulatory treatments are available for allergic disease, none of them are applicable or relevant or useful in fungal induced allergy. It is essential to understand the pathogenesis of the disease including the antigen induced immunoregulation and the resulting factors, such as cytokine, chemokines, pathways activating factors, inflammatory and airway remodeling factors need to be understood for intervening with appropriate treatment. Animal models are essential in understanding these features of the disease. Several models of allergic aspergillosis have been developed in recent years in various animals. However, murine models have been studied more carefully and extensively. The exposure to antigen in mice leads to allergy very similar to ABPA with high IgE, elevated peripheral blood and lung eosinophils, pulmonary inflammation, and airway hyperreactivity. The role of various cytokines and chemokines and their receptors were also studied. In addition, immunotherapy and vaccination have been attempted in recent years using the murine model of ABPA. This review covers the murine model of Aspergillus induced allergy and asthma and presented critically our current understanding of the subject and the potential application of such a model in future for developing treatment modalities.

Eosinophilic inflammation and airway hyper-responsiveness are profoundly inhibited by a helminth (Ascaris suum) extract in a murine model of asthma

BACKGROUND

The increase of atopic disorders in developed countries has been associated with the decline of infectious diseases, including helminthic infections. We have already demonstrated that adult worm extracts from Ascaris suum (ASC) suppress the IgE antibody production against unrelated antigens.

OBJECTIVE

Here we investigated the influence of ASC on the development of pulmonary eosinophilic inflammation in a murine model of asthma.

METHODS

Heat-coagulated egg white alone (EWI) or mixed with ASC (EWI + ASC) was implanted subcutaneously in B10.A or C57BL/6 mice, and 14 days later they were challenged intratracheally with OVA or exposed to aerosolized OVA for 4 days.

RESULTS

The suppressive effect of ASC was demonstrated on the accumulation of cells into airways, with reduction of eosinophil numbers and of eosinophil peroxidase activity in EWI + ASC-immunized mice. This effect correlated with a marked reduction of IL-5 and IL-4 levels in the BAL from C57BL/6 and B10. A mice, respectively, and of eotaxin in BAL and lung tissue from both strains. OVA-specific IgG1 and IgE levels were also impaired in serum and BAL from these mice. Airway hyper-reactivity to methacholine was obtained in B10. A mice sensitized with EWI, but the respiratory mechanical parameters returned to normal levels in EWI + ASC-immunized mice.

CONCLUSION

These results indicate that ASC has a profound inhibitory effect on lung inflammation and hyper-responsiveness and that suppression of IL-5 or IL-4 and of eotaxin contributes to this effect.