Development of eosinophilic airway inflammation and airway hyperresponsiveness requires interleukin-5 but not immunoglobulin E or B lymphocytes

Activation of the alternative complement pathway modulates inflammation in thoracic aortic aneurysm/dissection

Thoracic aortic aneurysm/dissection (TAAD) is a lethal vascular disease, and several pathological factors participate in aortic medial degeneration. We previously discovered that the complement C3a-C3aR axis in smooth muscle cells promotes the development of thoracic aortic dissection (TAD) through regulation of matrix metalloproteinase 2. However, discerning the specific complement pathway that is activated and elucidating how inflammation of the aortic wall is initiated remain unknown. We ascertained that the plasma levels of C3a and C5a were significantly elevated in patients with TAD and that the levels of C3a, C4a, and C5a were higher in acute TAD than in chronic TAD. We also confirmed the activation of the complement in a TAD mouse model. Subsequently, knocking out Cfb (Cfb) or C4 in mice with TAD revealed that the alternative pathway and Cfb played a significant role in the TAD process. Activation of the alternative pathway led to generation of the anaphylatoxins C3a and C5a, and knocking out their receptors reduced the recruitment of inflammatory cells to the aortic wall. Moreover, we used serum from wild-type mice or recombinant mice Cfb as an exogenous source of Cfb to treat Cfb KO mice and observed that it exacerbated the onset and rupture of TAD. Finally, we knocked out Cfb in the FBN1C1041G/+ Marfan-syndrome mice and showed that the occurrence of TAA was reduced. In summary, the alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.NEW & NOTEWORTHY The alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.

Nasal eosinophilia as a preliminary discriminative biomarker of non-allergic rhinitis in every day clinical pediatric practice

BACKGROUND

Non-allergic rhinitis (NAR) in children, named local allergic rhinitis (LAR) and non-allergic rhinitis with eosinophilia syndrome (NARES), are recently termed entities in childhood characterized by symptoms suggestive of allergic rhinitis in the absence of systemic atopy. Nasal eosinophils (nEo) are the principal cells involved in the allergy inflammation and nasal allergen provocation test is the gold standard method for the diagnosis, albeit with several limitations. The aim of this study was to validate the presence of nEo in combination with the therapeutic response to nasal steroids, as a preliminary discriminator of NAR in real life data.

METHODS

In a prospective cohort study, 128 children (63.3% male, aged 72 ± 42 m) with history of NAR were enrolled and followed up for 52 ± 32 m. Nasal cytology was performed and nasal steroids trial was recommended initially in all and repeatedly in relapsing cases. Response to therapy was clinically evaluated using 10-VAS.

RESULTS

Significant nEo was found in 59.3% of the cases and was related to reported dyspnea episodes. 23.4% had no response to therapy, whereas 51.5% were constantly good responders. Response to therapy was related to nEo and a cutoff point of 20% was defined as the most reliable biological marker with 94% sensitivity and 77% specificity.

CONCLUSIONS

In children with symptoms of NAR, the presence of nEo > 20% constantly responding to nasal steroid therapy, is a clear indicator of atopy. In an everyday clinical setting, it emerged as an easy, preliminary, cell biomarker suggestive of further investigation such as NAPT, to discriminate LAR from NARES.

Deletion of IL-4Rα signaling on B cells limits hyperresponsiveness depending on antigen load

BACKGROUND

B cells play an important role in allergies through secretion of IgE. IL-4 receptor α (IL-4Rα) is key in allergic asthma and regulates type 2 cytokine production, IgE secretion, and airway hyperresponsiveness. IL-4 activation of B cells is essential for class switching and contributes to the induction of B effector 2 (Be2) cells. The role of Be2 cells and signaling via IL-4Rα in B cells is not clearly defined.

OBJECTIVE

We sought to find out whether IL-4Rα-responsive B cells or Be2 function was essential in experimental allergic asthma.

METHODS

Mice lacking IL-4Rα on B cells (mb1^creIL-4Rα^-/lox) or littermate controls (IL-4Rα^-/lox) and mice lacking IL-4 or IL-4/IL-13 on B cells were sensitized and challenged with high-dose house dust mite (>10 μg) or with low-dose house dust mite (<3 μg). We also adoptively transferred naive IL-4Rα^-/lox or IL-4Rα^-/- B cells into μMT^-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness.

RESULTS

We found that IL-4Rα signaling on B cells was important for optimal T_H2 allergic immune responses mainly when the load of antigen is limited. IL-4Rα signaling on B cells was essential for germinal centers and in the effector phase of allergic responses. Be2 cells were essential in airway hyperresponsiveness, but not in other parameters.

CONCLUSIONS

IL-4Rα signaling on B cells is deleterious in allergic asthma because it is required for optimal T_H2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.

Single and Synergistic Effects of Type 2 Cytokines on Eosinophils and Asthma Hallmarks

The type 2 cytokines IL-5, IL-13, and IL-4 play an important role in the induction and progression of asthma. According to the Global Initiative for Asthma guidelines, blood eosinophil numbers are one marker that helps to guide treatment decisions in patients suffering from severe forms of asthma. Effects of type 2 cytokines were analyzed, alone or in combination, on eosinophils in blood and other compartments and on the development of asthma symptoms. C57BL/6 mice received a single intranasal application of equimolar amounts of IL-5, IL-13, and IL-4, alone or in combination. Numbers, activation state, and migratory behavior of eosinophils in bone marrow (BM), blood, lung, and bronchoalveolar lavage as well as airway hyperresponsiveness and goblet cell metaplasia were evaluated. Only IL-13 was associated with airway eosinophilia, development of airway hyperresponsiveness, and goblet cell metaplasia, without any synergistic effects. IL-5 increased the number of eosinophils in BM and lung tissue but failed to affect structural changes. IL-4 had similar, but weaker, effects to IL-13. Cytokine combinations synergistically affected eosinophils but failed to enhance IL-13-driven effects on lung function or goblet cell metaplasia. IL-5 and IL-13 markedly increased eosinophil numbers locally in lung and airways and distally in blood and BM, whereas IL-5 and IL-4 only increased eosinophils in lung and BM. IL-13 together with IL-4 failed to demonstrate any synergistic effect. These insights into single and combined effects of type 2 cytokines on disease-driving mechanisms could improve understanding of the impact and effectiveness of new therapies in asthma.

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.

Modelling the asthma phenotype: impact of cigarette smoke exposure

Background

Asthmatics that are exposed to inhaled pollutants such as cigarette smoke (CS) have increased symptom severity. Approximately 25% of adult asthmatics are thought to be active smokers and many sufferers, especially in the third world, are exposed to high levels of inhaled pollutants. The mechanism by which CS or other airborne pollutants alter the disease phenotype and the effectiveness of treatment in asthma is not known. The aim of this study was to determine the impact of CS exposure on the phenotype and treatment sensitivity of rodent models of allergic asthma.

Methods

Models of allergic asthma were configured that mimicked aspects of the asthma phenotype and the effect of CS exposure investigated. In some experiments, treatment with gold standard asthma therapies was investigated and end-points such as airway cellular burden, late asthmatic response (LAR) and airway hyper-Reactivity (AHR) assessed.

Results

CS co-exposure caused an increase in the LAR but interestingly attenuated the AHR. The effectiveness of LABA, LAMA and glucocorticoid treatment on LAR appeared to be retained in the CS-exposed model system. The eosinophilia or lymphocyte burden was not altered by CS co-exposure, nor did CS appear to alter the effectiveness of glucocorticoid treatment. Steroids, however failed to reduce the neutrophilic inflammation in sensitized mice exposed to CS.

Conclusions

These model data have certain parallels with clinical findings in asthmatics, where CS exposure did not impact the anti-inflammatory efficacy of steroids but attenuated AHR and enhanced symptoms such as the bronchospasm associated with the LAR. These model systems may be utilised to investigate how CS and other airborne pollutants impact the asthma phenotype; providing the opportunity to identify novel targets.

T-Helper Type 2 Cells Direct Antigen-Induced Eosinophilic Skin Inflammation in Mice

Eosinophilic inflammation in combination with immunoglobulin E (IgE) production is a characteristic feature of atopic dermatitis. Although activated T-helper type (Th) 2 cells play critical roles in the local accumulation and activation of eosinophils, whether they induce eosinophilic skin inflammation, independent of the IgE-mediated pathway has been unclear. To address the functional role of T cells in allergic skin diseases, we herein transferred Th1/Th2-differentiated or naive DO11.10 T cells into unprimed BALB/c mice. Ovalbumin-specific Th2 cells, as well as eosinophils, accumulated in the skin upon antigen challenge, despite the absence of antigen-specific IgE. Neither antigen-specific Th1 nor naive T cells induced eosinophil accumulation, although Th1 cells by themselves migrated into the skin. Interleukin (IL)-4, IL-5, and eotaxin were specifically produced in the skin of antigen-challenged, Th2 cell-transferred mice, whereas interferon (IFN)-γ and regulated on activation, normal T cell expressed and secreted (RANTES) were preferentially produced in Th1 cells-transferred mice. Production of monocyte chemoattractant protein (MCP)-1 and MCP-3 was enhanced by both Th1 and Th2 cells. The accumulation of eosinophils and Th2 cells in the skin was suppressed by both dexamethasone and FK506, indicating an essential role of Th2 cells in eosinophil recruitment. We conclude that Th2 cells can induce eosinophilic infiltration into the skin in the absence of antigen-specific IgE.

Association of ORMDL3 with rhinovirus-induced endoplasmic reticulum stress and type I Interferon responses in human leucocytes

BACKGROUND

Children with risk alleles at the 17q21 genetic locus who wheeze during rhinovirus illnesses have a greatly increased likelihood of developing childhood asthma. In mice, overexpression of the 17q21 gene ORMDL3 leads to airway remodelling and hyperresponsiveness. However, the mechanisms by which ORMDL3 predisposes to asthma are unclear. Previous studies have suggested that ORMDL3 induces endoplasmic reticulum (ER) stress and production of the type I interferon (IFN)-regulated chemokine CXCL10.

OBJECTIVE

The purpose of this study was to determine the relationship between ORMDL3 and rhinovirus-induced ER stress and type I IFN in human leucocytes.

METHODS

ER stress was monitored by measuring HSPA5, CHOP and spliced XBP1 gene expression, and type I IFN by measuring IFNB1 (IFN-β) and CXCL10 expression in human cell lines and primary leucocytes following treatment with rhinovirus. Requirements for cell contact and specific cell type in ORMDL3 induction were examined by transwell assay and depletion experiments, respectively. Finally, the effects of 17q21 genotype on the expression of ORMDL3, IFNB1 and ER stress genes were assessed.

RESULTS

THP-1 monocytes overexpressing ORMDL3 responded to rhinovirus with increased IFNB1 and HSPA5. Rhinovirus-induced ORMDL3 expression in primary leucocytes required cell-cell contact, and induction was suppressed by plasmacytoid dendritic cell depletion. The degree of rhinovirus-induced ORMDL3, HSPA5 and IFNB1 expression varied by leucocyte type and 17q21 genotype, with the highest expression of these genes in the asthma-associated genotype.

CONCLUSIONS AND CLINICAL RELEVANCE

Multiple lines of evidence support an association between higher ORMDL3 and increased rhinovirus-induced HSPA5 and type I IFN gene expression. These associations with ORMDL3 are cell type specific, with the most significant 17q21 genotype effects on ORMDL3 expression and HSPA5 induction evident in B cells. Together, these findings have implications for how the interaction of increased ORMDL3 and rhinovirus may predispose to asthma.

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.

Animal models of asthma: utility and limitations

Clinical studies in asthma are not able to clear up all aspects of disease pathophysiology. Animal models have been developed to better understand these mechanisms and to evaluate both safety and efficacy of therapies before starting clinical trials. Several species of animals have been used in experimental models of asthma, such as Drosophila, rats, guinea pigs, cats, dogs, pigs, primates and equines. However, the most common species studied in the last two decades is mice, particularly BALB/c. Animal models of asthma try to mimic the pathophysiology of human disease. They classically include two phases: sensitization and challenge. Sensitization is traditionally performed by intraperitoneal and subcutaneous routes, but intranasal instillation of allergens has been increasingly used because human asthma is induced by inhalation of allergens. Challenges with allergens are performed through aerosol, intranasal or intratracheal instillation. However, few studies have compared different routes of sensitization and challenge. The causative allergen is another important issue in developing a good animal model. Despite being more traditional and leading to intense inflammation, ovalbumin has been replaced by aeroallergens, such as house dust mites, to use the allergens that cause human disease. Finally, researchers should define outcomes to be evaluated, such as serum-specific antibodies, airway hyperresponsiveness, inflammation and remodeling. The present review analyzes the animal models of asthma, assessing differences between species, allergens and routes of allergen administration.

Role of B cells in TH cell responses in a mouse model of asthma

BACKGROUND

The importance of B lymphocytes to present antigens for antibody production is well documented. In contrast, very little is known about their capacity to influence CD4⁺ T-cell activation during a primary or secondary response to allergens.

OBJECTIVE

Using mouse models of asthma, we investigated the role of B cells as antigen-presenting cells in priming and maintenance of T_H cell responses.

METHODS

Mice were immunized through the intranasal route with house dust mite (HDM) extract derived from Dermatophagoides pteronyssinus. B cells were depleted in HDM-sensitized animals to investigate the importance of B cells in maintenance of the allergic response. B cells were depleted before HDM sensitization to investigate the role of B cells in T-cell priming; furthermore, HDM sensitization was performed in mice with MHC class II expression restricted to the B-cell lineage.

RESULTS

We found that B cells serve as potent antigen-presenting cells ex vivo and restimulate in vivo-primed HDM-specific T_H cells. HDM antigens were taken up by B cells independently of B-cell receptor specificity, indicating that HDM uptake and antigen presentation to CD4⁺ T cells is not restricted to rare B cells carrying HDM-specific B cell receptors. B-cell depletion before HDM challenge in HDM-sensitized mice resulted in a dramatic reduction of allergic response, indicating the role of B cells in amplification of T_H2 responses. In contrast, HDM sensitization of mice in which MHC class II expression was restricted to B cells revealed the inability of these cells to prime T_H2 responses but highlighted their unexpected role in priming T_H1 and T_H17 responses.

CONCLUSION

Collectively, these data reveal new mechanisms leading to initiation and exacerbation of the allergic response that might have implications for designing new therapeutic strategies to combat HDM allergy.

Lung Pathologies in a Chronic Inflammation Mouse Model Are Independent of Eosinophil Degranulation

RATIONALE

The release of eosinophil granule proteins in the lungs of patients with asthma has been dogmatically linked with lung remodeling and airway hyperresponsiveness. However, the demonstrated inability of established mouse models to display the eosinophil degranulation occurring in human subjects has prevented a definitive in vivo test of this hypothesis.

OBJECTIVES

To demonstrate in vivo causative links between induced pulmonary histopathologies/lung dysfunction and eosinophil degranulation.

METHODS

A transgenic mouse model of chronic T-helper cell type 2-driven inflammation overexpressing IL-5 from T cells and human eotaxin 2 in the lung (I5/hE2) was used to test the hypothesis that chronic histopathologies and the development of airway hyperresponsiveness occur as a consequence of extensive eosinophil degranulation in the lung parenchyma.

MEASUREMENT AND MAIN RESULTS

Studies targeting specific inflammatory pathways in I5/hE2 mice surprisingly showed that eosinophil-dependent immunoregulative events and not the release of individual secondary granule proteins are the central contributors to T-helper cell type 2-induced pulmonary remodeling and lung dysfunction. Specifically, our studies highlighted a significant role for eosinophil-dependent IL-13 expression. In contrast, extensive degranulation leading to the release of major basic protein-1 or eosinophil peroxidase was not causatively linked to many of the induced pulmonary histopathologies. However, these studies did define a previously unappreciated link between the release of eosinophil peroxidase (but not major basic protein-1) and observed levels of induced airway mucin.

CONCLUSIONS

These data suggest that improvements observed in patients with asthma responding to therapeutic strategies ablating eosinophils may occur as a consequence of targeting immunoregulatory mechanisms and not by simply eliminating the destructive activities of these purportedly end-stage effector cells.

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.

Cbl-b Deficiency in Mice Results in Exacerbation of Acute and Chronic Stages of Allergic Asthma

Mice sensitized to ovalbumin (OVA) develop allergic airway disease (AAD) with short-term daily OVA aerosol challenge; inflammation resolves with long-term OVA aerosol exposure, resulting in local inhalational tolerance (LIT). Cbl-b is an E3 ubiquitin ligase involved with CD28 signaling; Cbl-b^−/− effector T cells are resistant to regulatory T cell-mediated suppression in vitro and in vivo. The present study utilized Cbl-b^−/− mice to investigate the role of Cbl-b in the development of AAD and LIT. Cbl-b^−/− mice exhibited increased airway inflammation during AAD, which failed to resolve with long-term OVA aerosol exposure. Exacerbation of inflammation in Cbl-b^−/− mice correlated with increased proinflammatory cytokine levels and expansion of effector T cells in the BAL during AAD, but did not result in either a modulation of lymphocyte subsets in systemic tissues or in OVA-specific IgE in serum. These results implicate a role for Cbl-b in the resolution of allergic airway inflammation.

Therapeutic effects of naringin in a guinea pig model of ovalbumin-induced cough-variant asthma

Naringin, a well known component isolated from Exocarpium Citri Grandis, has significant antitussive effects. Recently, Naringin exhibited novel anti-inflammatory effect in chronic inflammatory diseases. In this work, we firstly evaluated the effects of naringin on enhanced cough, airway hyper-responsiveness (AHR), and airway inflammation in an ovalbumin-induced experimental cough-variant asthma (CVA) model in guinea pigs. We investigated the effect of naringin (18.4 mg/kg, per os, single dose or consecutively) on cough to inhaled capsaicin after challenge with an aerosolized antigen in actively sensitized guinea pigs. The effect of naringin on AHR to inhaled methacholine was evaluated 24 h after cough determination. Airway inflammation was assessed via bronchoalveolar lavage fluid (BALF) cytology and lung histopathology. Naringin, given consecutively, significantly reduced ovalbumin-induced enhanced cough and AHR, inhibited the increases in the leukocytes, interleukin-4 (IL-4), IL-5, and IL-13 in BALF compared with the model group. Moreover, the pathologic changes in lung tissues were clearly ameliorated by naringin treatment. These results suggest that naringin may be a beneficial agent for CVA treatment.

Serotonin 5-HT₂ receptor activation prevents allergic asthma in a mouse model

Asthma is an inflammatory disease of the lung characterized by airways hyper-responsiveness (AHR), inflammation, and mucus hyperproduction. Current mainstream therapies include bronchodilators that relieve bronchoconstriction and inhaled glucocorticoids to reduce inflammation. The small molecule hormone and neurotransmitter serotonin has long been known to be involved in inflammatory processes; however, its precise role in asthma is unknown. We have previously established that activation of serotonin 5-hydroxytryptamine (5-HT)(2A) receptors has potent anti-inflammatory activity in primary cultures of vascular tissues and in the whole animal in vasculature and gut tissues. The 5-HT(2A) receptor agonist, (R)-2,5-dimethoxy-4-iodoamphetamine [(R)-DOI] is especially potent. In this work, we have examined the effect of (R)-DOI in an established mouse model of allergic asthma. In the ovalbumin mouse model of allergic inflammation, we demonstrate that inhalation of (R)-DOI prevents the development of many key features of allergic asthma, including AHR, mucus hyperproduction, airways inflammation, and pulmonary eosinophil recruitment. Our results highlight a likely role of the 5-HT2 receptors in allergic airways disease and suggest that 5-HT2 receptor agonists may represent an effective and novel small molecule-based therapy for asthma.

IL-37 requires IL-18Rα and SIGIRR/IL-1R8 to diminish allergic airway inflammation in mice

BACKGROUND

Interleukin (IL) 37 has been described as a negative regulator of innate immunity, as it reduces the activation and cytokine production of different innate immune cells. Recently, results from the CLARA childhood asthma cohort suggested an implication of IL-37 for human asthma pathogenesis. This study aimed to investigate the effects of IL-37 on allergic airway inflammation in a mouse model of experimental asthma.

METHODS

Peripheral blood mononuclear cells (PBMCs) of children were cultured for 48 h (anti-CD3/anti-CD28 stimulation or unstimulated), and IL-37 concentrations in supernatants were determined. Wild-type, IL-18Rα-deficient ((-/-) ), and SIGIRR(-/-) C57BL/6 mice were sensitized to ovalbumin (OVA) and challenged with OVA aerosol to induce acute experimental asthma, and IL-37 was applied intranasally prior to each OVA challenge. Airway hyper-responsiveness (AHR), airway inflammation, cytokine levels in broncho-alveolar lavage fluid, and mucus production were determined.

RESULTS

IL-37 production of human PBMCs was significantly lower in allergic asthmatics vs healthy children. In wild-type mice, intranasal administration of IL-37 ablated allergic airway inflammation as well as cytokine production and subsequently diminished the hallmarks of experimental asthma including mucus hyperproduction and AHR. In contrast, local application of IL-37 produced none of these effects in mice lacking either IL18Rα or SIGIRR/IL-1R8.

CONCLUSIONS

This study demonstrates that IL-37 is able to ablate a TH2 cell-directed allergic inflammatory response and the hallmarks of experimental asthma in mice, suggesting that IL-37 may be critical for asthma pathogenesis. Furthermore, these data suggest a mode of action of IL-37 that involves IL18Rα as well as the orphan receptor SIGIRR/IL-1R8.

Translational value of animal models of asthma: Challenges and promises

Asthma is a heterogeneous disease in which various environmental stimuli as well as different genes, cell types, cytokines and mediators are implicated. This chronic inflammatory disorder of the airways is estimated to affect as many as 300 million people worldwide. Animal models of asthma, despite their limitations, have contributed greatly to our understanding of disease pathology and the identification of key processes, cells and mediators in asthma. However, it is less likely to develop an animal model of asthma that takes into account all aspects of human disease. The focus in current asthma research is increasingly on severe asthma because this group of patients is not well treated today. Recent advances in studies of asthma exacerbation are thus considered. We therefore need to develop translational model systems for pharmacological evaluation and molecular target discovery of severe asthma and asthma exacerbations. In this review we attempted to discuss the different animal models of asthma, with special emphasis on ovalbumin and house dust mite models, their merits and their limitations.

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.

Bronchial hyperreactivity in children with antibody deficiencies

BACKGROUND

Antibody deficiency comprises a heterogeneous group of disorders characterised by the body's inability to mount an effective antibody response to pathogens. Although it has been reported that asthma and allergic disease are frequent in antibody deficiencies, there are no data that evaluate and compare bronchial hyperreactivity (BHR) in all groups of antibody deficiencies. In this study, we aimed to evaluate and compare the frequency of BHR in patients with different antibody deficiencies.

METHODS

The study was carried out on 113 patients between ages 5 and 18 diagnosed with antibody deficiencies. The patients and their families were questioned on their history of asthma and allergic diseases. Allergic skin prick tests and non-specific bronchial provocation test with methacholine was done for all patients. Complete blood count and serum total IgE levels were measured.

RESULTS

The mean age of the patients was 10.8 ± 3.8 years and 66.4% were male. Within the study group 41.6% of the patients had selective IgA deficiency, 24.8% had IgG subclass deficiency, 14.2% had partial IgA deficiency, 10.6% had common variable immunodeficiency, 6.2% had transient hypogammaglobulinaemia and 2.7% X-linked agammaglobulinaemia. In total group, 42.5% had bronchial hyperreactivity with methacholine challenge test. BHR was more significant in both patients with selective IgA deficiency and partial IgA deficiency compared to those with IgG subclass deficiency (P=0.041 and P=0.038, respectively).

CONCLUSION

BHR was high in antibody deficiencies, especially selective IgA deficiency compared to IgG subclass deficiency.

Murine asthma models

Immunotoxicity can take the form of an enhanced immune response or hypersensitivity. Asthma is one possible consequence of hypersensitivity in the lung, with characteristics that include reversible airway obstruction, eosinophil infiltration into the lung, and airway hyperresponsiveness to agonists such as methacholine. In toxicology, two primary areas of investigation prompt the measurement of the asthmatic response in an animal: (1) identification of chemicals or proteins that cause asthma, i.e., respiratory allergens, and (2) identification of exposures that will exacerbate existing asthma. An ovalbumin-induced asthma model can be used to identify exposures that exacerbate existing asthma. A protocol for the sensitization and challenge of mice with ovalbumin is described; it leads to the asthma symptoms of airway hyperresponsiveness and eosinophil infiltration. Assessment of airway hyperresponsiveness to methacholine uses whole body plethysmography in conscious unrestrained mice. Bronchoalveolar lavage of the mouse determines the extent of cellular infiltration into the airspace. Removal of lung lobes and assay of eosinophil peroxidase and myeloperoxidase provides a measure of the numbers of eosinophils and neutrophils, respectively, in the lung. Depending on the experimental goals, bronchoalveolar lavage fluid and lung tissue can also be used for isolation of RNA, and measurement of cytokines, chemokines, antibodies, and inflammatory mediators.

Local and systemic immunological parameters associated with remission of asthma symptoms in children

The immunological and clinical parameters that are associated with asthma remission are poorly understood. The cytokine and local mediator changes associated with the resolution of asthma symptoms were examined in three groups of subjects 12-18 years of age (n = 15 in each group): (a) continuing asthma group (CA) who had persistent symptoms since early childhood, (b) an age, sex and atopic status-matched group who had persistent symptoms in early childhood but in whom these had resolved (RA), and (c) a non-atopic, non-asthmatic control group. Clinical parameters, sputum cell counts, peripheral blood mononuclear cell (PBMC) cytokine production and activation marker expression were determined. All of the CA had methacholine airway hyperresponsiveness compared with only half of the RA subjects. The CA showed elevated numbers of eosinophils and increased ECP and IL-5 in sputum, which were not observed in the RA. PBMC cytokine studies revealed increased production of the type 1 cytokines IL-12, IFN-γ and TNF-α in the CA group compared with the RA group, under a range of activation conditions, however, the production of IL-4 and IL-5 were unchanged. These findings suggest that decreased type 1 cytokine expression as well as decreased eosinophilic inflammation is associated with the resolution of asthma symptoms.

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.

Biphasic late airway hyperresponsiveness in a murine model of asthma

BACKGROUND

Nonspecific airway hyperresponsiveness (AHR) is one of the cardinal features of bronchial asthma. Early AHR is caused by chemical mediators released from pulmonary mast cells activated in an IgE-dependent way. However, the mechanism of late AHR remains unclear.

METHODS

Features of airway allergic inflammation were analyzed, including antigen-induced AHR, using a murine model of asthma. The model was suitable for examining the sequential early molecular events occurring after the initial airway exposure to antigen.

RESULTS

AHR increased at 10-12 h after airway challenge, followed by the second-phase response, which was larger and broader in resistance at 18-30 h. Pretreatment of sensitized animals with anti-tumor necrosis factor (TNF) before airway challenge or induction of allergic asthma in TNF(-/-) mice resulted in abrogation of the first-phase late AHR. Intratracheal instillation of TNF induced a single peak of AHR at 10 h. IgE and IgG immune complexes induced the development of the first-phase late AHR by TNF production. Pretreatment with cytosolic phospholipase inhibitor and 5-lipoxygenase inhibitors abolished the first-phase late AHR as well as the leukotriene B(4) levels in the airway. CpG-oligodeoxynucleotide (ODN) pretreatment reduced airway levels of Th2 cytokines, eosinophil infiltration and second-phase late AHR. However, CpG-ODN did not reduce TNF levels or the magnitude of first-phase late AHR.

CONCLUSION

Biphasic late AHR occurs in a murine model of asthma. First- and second-phase late AHR is caused by TNF and Th2 response, respectively.

Eosinophil crystalloid granules: structure, function, and beyond

Eosinophils are granulocytes associated with host defense against parasitic helminths with allergic conditions and more recently, with immunoregulatory responses. Eosinophils are distinguished from leukocytes by their dominant population of cytoplasmic crystalloid (also termed secretory, specific, or secondary) granules that contain robust stores of diverse, preformed cationic proteins. Here, we provide an update on our knowledge about the unique and complex structure of human eosinophil crystalloid granules. We discuss their significance as rich sites of a variety of receptors and review our own recent research findings and those of others that highlight discoveries concerning the function of intracellular receptors and their potential implications in cell signaling. Special focus is provided on how eosinophils might use these intracellular receptors as mechanisms to secrete, selectively and rapidly, cytokines or chemokines and enable cell-free extracellular eosinophil granules to function as independent secretory structures. Potential roles of cell-free eosinophil granules as immune players in the absence of intact eosinophils will also be discussed.

CCL11 elicits secretion of RNases from mouse eosinophils and their cell-free granules

Rapid secretion of eosinophil-associated RNases (EARs), such as the human eosinophilic cationic protein (ECP), from intracellular granules is central to the role of eosinophils in allergic diseases and host immunity. Our knowledge regarding allergic inflammation has advanced based on mouse experimental models. However, unlike human eosinophils, capacities of mouse eosinophils to secrete granule proteins have been controversial. To study mechanisms of mouse eosinophil secretion and EAR release, we combined an RNase assay of mouse EARs with ultrastructural studies. In vitro, mouse eosinophils stimulated with the chemokine eotaxin-1 (CCL11) secreted enzymatically active EARs (EC(50) 5 nM) by piecemeal degranulation. In vivo, in a mouse model of allergic airway inflammation, increased airway eosinophil infiltration (24-fold) correlated with secretion of active RNases (3-fold). Moreover, we found that eosinophilic inflammation in mice can involve eosinophil cytolysis and release of cell-free granules. Cell-free mouse eosinophil granules expressed functional CCR3 receptors and secreted their granule proteins, including EAR and eosinophil peroxidase in response to CCL11. Collectively, these data demonstrate chemokine-dependent secretion of EARs from both intact mouse eosinophils and their cell-free granules, findings pertinent to understanding the pathogenesis of eosinophil-associated diseases, in which EARs are key factors.

Characterization of CD19(+)CD23(+)B2 lymphocytes in the allergic airways of BALB/c mice in response to the inhalation of Aspergillus fumigatus conidia

Fungal sensitization in patients with asthma often indicates an unusual disease course in which traditional asthma treatments have little effect and in which morbidity is particularly severe. Airway hyperresponsiveness (AHR), inflammatory infiltrates, smooth muscle hyperplasia, and irreversible fibrotic remodeling of the bronchial architecture are features of allergic fungal asthma. The systemic production of IgE has long been associated with the immunopathogenesis of allergic asthma; however, the role of B lymphocytes and their products in the response to fungal allergens remains unclear. In the present study, we hypothesize that B lymphocytes are recruited to the allergic lung to impact the allergic response. Using a murine fungal aeroallergen model to mimic the human syndrome, we characterized the B cell population in the lung after fungal challenge and found that CD19(+)CD23(+) B2 lymphocyte numbers are increased in the allergic lung in a dynamic process. IgA, IgG(2a), and IgE were prominent in the serum and bronchoalveolar lavage fluid of allergic animals. It was evident that a tissue-centric production of these antibodies was possible. IgA-, IgG-, and IgE-producing cells from the allergic lung were identified by flow cytometry and immunohistochemistry. This study shows for the first time that CD19(+)CD23(+) B2 lymphocyte numbers change in the lung in a dynamic process after inhalation of fungal conidia and their increase has a significant impact on the Ab production in the pulmonary compartment in the context of fungal allergy.

Alcohol reduces airway hyperresponsiveness (AHR) and allergic airway inflammation in mice

There is very limited knowledge about the effects of alcohol on airway hyperresponsiveness and inflammation in asthma. Historical accounts of alcohol administration to patients with breathing problems suggest that alcohol may have bronchodilating properties. We hypothesized that alcohol exposure will alter airway hyperresponsiveness (AHR) and pulmonary inflammation in a mouse model of allergic asthma. To test this hypothesis, BALB/c mice were fed either 18% alcohol or water and then sensitized and challenged with ovalbumin (OVA). AHR was assessed by means of ventilation or barometric plethysmography and reported as either total lung resistance or enhanced pause, respectively. Airway inflammation was assessed by total and differential cell counts in bronchoalveolar lavage fluid (BALF), cytokine levels in BALF, lung histology, and serum immunoglobulin E (IgE) levels. Alcohol feeding significantly blocked methacholine-induced increases in AHR compared with water-fed controls. Alcohol feeding significantly reduced total cell numbers (64%) as well as the number of eosinophils (84%) recruited to the lungs of these mice. Modest changes in lung pathology were also observed. Alcohol exposure led to a reduction of IgE in the serum of the EtOH OVA mice. These data demonstrate that alcohol exposure blunts AHR and dampens allergic airway inflammation indices in allergic mice and suggest that there may be an important role for alcohol in the modulation of asthma. These data provide an in vivo basis for previous clinical observations in humans substantiating the bronchodilator properties of alcohol and for the first time demonstrates an alcohol-induced reduction of allergic inflammatory cells in a mouse model of allergic asthma.

A single DH gene segment is sufficient for the establishment of an asthma phenotype in a murine model of allergic airway inflammation

BACKGROUND

We have previously shown that the allergic sensitization to ovalbumin does not represent a superantigen-like immune response. In gene-targeted mice (ΔD-iD) with a single modified Diversity gene segment (D(H)) of the immunoglobulin heavy chain, enriched for charged amino acids, the asthma phenotype in a murine model was markedly alleviated compared to wild-type animals.

OBJECTIVE

We now sought to determine whether the confinement to a single D(H) gene segment alone leads to a reduced allergic phenotype.

METHODS

We examined another gene-targeted mouse strain (ΔD-DFL) with a single D(H) gene segment which encodes for neutral amino acids, thus reflecting the preferential repertoire in wild-type mice. Mice were sensitized intraperitoneally to ovalbumin.

RESULTS

Despite the constraint to a single D(H) gene segment, ΔD-DFL mice mounted high total and allergen-specific IgG(1) and IgE serum levels after sensitization to ovalbumin. The affinity constants of allergen-specific IgG(1) antibodies did not differ between ΔD-DFL and wild type. Following challenge with aerosolized allergen, a marked local T(H)2 cytokine response and an eosinophilic airway inflammation developed. Quantitative histology revealed increased mucus production and intense goblet cell metaplasia which were identical to those in wild type. Moreover, ΔD-DFL mice developed an airway hyperreactivity to methacholine and to the specific allergen, which both did not differ from those in wild-type animals.

CONCLUSION

A single D(H) gene segment is sufficient for the establishment of the asthma phenotype in a murine model of allergic airway inflammation. Thus, the allergic phenotype depends on the amino acid composition and not on the diversity of the classical antigen-binding site.

Mast cells in allergic asthma and beyond

Mast cells have been regarded for a long time as effector cells in IgE mediated type I reactions and in host defence against parasites. However, they are resident in all environmental exposed tissues and express a wide variety of receptors, suggesting that these cells can also function as sentinels in innate immune responses. Indeed, studies have demonstrated an important role of mast cells during the induction of life-saving antibacterial responses. Furthermore, recent findings have shown that mast cells promote and modulate the development of adaptive immune responses, making them an important hinge of innate and acquired immunity. In addition, mast cells and several mast cell-produced mediators have been shown to be important during the development of allergic airway diseases. In the present review, we will summarize findings on the role of mast cells during the development of adaptive immune responses and highlight their function, especially during the development of allergic asthma.

Suppression of Th2-driven airway inflammation by allergen immunotherapy is independent of B cell and Ig responses in mice

Allergen-specific immunotherapy (IT) uniquely renders long-term relief from allergic symptoms and is associated with elevated serum levels of allergen-specific IgG and IgA. The allergen-specific IgG response induced by IT treatment was shown to be critical for suppression of the immediate phase of the allergic response in mice, and this suppression was partially dependent on signaling through FcγRIIB. To investigate the relevance of the allergen-specific IgG responses for suppression of the Th2-driven late-phase allergic response, we performed IT in a mouse model of allergic asthma in the absence of FcγRIIB or FcγRI/FcγRIII signaling. We found that suppression of Th2 cell activity, allergic inflammation, and allergen-specific IgE responses is independent of FcγRIIB and FcγRI/FcγRIII signaling. Moreover, we show that the IT-induced allergen-specific systemic IgG or IgA responses and B cell function are dispensable for suppression of the late-phase allergic response by IT treatment. Finally, we found that the secretory mucosal IgA response also is not required for suppression of the Th2-driven allergic inflammation by IT. These data are in contrast to the suppression of the immediate phase of the allergic response, which is critically dependent on the induced allergen-specific serum IgG response. Hence, IT-induced suppression of the immediate and late phases of the allergic response is governed by divergent and independent mechanisms. Our data show that the IT-induced suppression of the Th2 cell-dependent late-phase allergic response is independent of the allergen-specific IgG and IgA responses that are associated with IT treatment.

Fcgamma receptor-mediated antigen uptake by lung DC contributes to allergic airway hyper-responsiveness and inflammation

During asthma, lung DC capture and process antigens to initiate and maintain allergic Th2 cell responses to inhaled allergens. The aim of the study was to investigate whether allergen-specific IgG, generated during sensitization, can potentiate the acute airway inflammation through Fcgamma receptor (FcgammaR)-mediated antigen uptake and enhance antigen presentation resulting in augmented T-cell proliferation. We examined the impact of antigen presentation and T-cell stimulation on allergic airway hyperresponsiveness and inflammation using transgenic and gene-deficient mice. Both airway inflammation and eosinophilia in bronchoalveolar lavage fluid were markedly reduced in sensitized and challenged FcgammaR-deficient mice. Lung DC of WT, but not FcgammaR-deficient mice, induced increased antigen-specific CD4+ T-cell proliferation when pulsed with anti-OVA IgG immune complexes. Intranasal application of anti-OVA IgG immune complexes resulted in enhanced airway inflammation, eosinophilia and Th2 cytokine release, mediated through enhanced antigen-specific T-cell proliferation in vivo. Finally, antigen-specific IgG in the serum of sensitized mice led to a significant increase of antigen-specific CD4+ T-cell proliferation induced by WT, but not FcgammaR-deficient, lung DC. We conclude that FcgammaR-mediated enhanced antigen presentation and T-cell stimulation by lung DC has a significant impact on inflammatory responses following allergen challenge in asthma.

IL-18 does not increase allergic airway disease in mice when produced by BCG

Whilst BCG inhibits allergic airway responses in murine models, IL-18 has adversary effects depending on its environment. We therefore constructed a BCG strain producing murine IL-18 (BCG-IL-18) and evaluated its efficiency to prevent an asthma-like reaction in mice. BALB/cByJ mice were sensitized (day (D) 1 and D10) by intraperitoneal injection of ovalbumin (OVA)-alum and primary (D20–22) and secondary (D62, 63) challenged with OVA aerosols. BCG or BCG-IL-18 were intraperitonealy administered 1 hour before each immunization (D1 and D10). BCG-IL-18 and BCG were shown to similarly inhibit the development of AHR, mucus production, eosinophil influx, and local Th2 cytokine production in BAL, both after the primary and secondary challenge. These data show that IL-18 did not increase allergic airway responses in the context of the mycobacterial infection, and suggest that BCG-IL-18 and BCG are able to prevent the development of local Th2 responses and therefore inhibit allergen-induced airway responses even after restimulation.

TH17 cells in asthma and COPD

Asthma and chronic obstructive pulmonary disease (COPD) represent two classes of chronic obstructive lung disorders that may share some similar immunologic mechanisms of disease. Asthma is a complex human disease characterized by airway hyperresponsiveness (AHR) and inflammation, whereas COPD is marked by progressive emphysematic changes in the lung. Recently it has been shown that advanced COPD is characterized by lymphoid follicles, drawing attention to immunological mechanisms in COPD. Despite numerous studies in mice to elucidate the immunologic mechanisms of asthma, sufficient current treatment options are limited. Clinically, many asthma patients fail to satisfactorily respond to standard steroid therapy, and this type of steroid-resistant, severe asthma has been linked to the presence of neutrophilic inflammation in the lung. The role of neutrophils, macrophages, and their secreted proteases in COPD needs to be better defined. Recently, the T lymphocyte subset T(H)17 was shown to play a role in regulating neutrophilic and macrophage inflammation in the lung, suggesting a potential role for T(H)17 cells in severe, steroid-insensitive asthma and COPD.

Respiratory allergy to Blomia tropicalis: immune response in four syngeneic mouse strains and assessment of a low allergen-dose, short-term experimental model

Background

The dust mite Blomia tropicalis is an important source of aeroallergens in tropical areas. Although a mouse model for B. tropicalis extract (BtE)-induced asthma has been described, no study comparing different mouse strains in this asthma model has been reported. The relevance and reproducibility of experimental animal models of allergy depends on the genetic background of the animal, the molecular composition of the allergen and the experimental protocol.

Objectives

This work had two objectives. The first was to study the anti-B. tropicalis allergic responses in different mouse strains using a short-term model of respiratory allergy to BtE. This study included the comparison of the allergic responses elicited by BtE with those elicited by ovalbumin in mice of the strain that responded better to BtE sensitization. The second objective was to investigate whether the best responder mouse strain could be used in an experimental model of allergy employing relatively low BtE doses.

Methods

Groups of mice of four different syngeneic strains were sensitized subcutaneously with 100 μg of BtE on days 0 and 7 and challenged four times intranasally, at days 8, 10, 12, and 14, with 10 μg of BtE. A/J mice, that were the best responders to BtE sensitization, were used to compare the B. tropicalis-specific asthma experimental model with the conventional experimental model of ovalbumin (OVA)-specific asthma. A/J mice were also sensitized with a lower dose of BtE.

Results

Mice of all strains had lung inflammatory-cell infiltration and increased levels of anti-BtE IgE antibodies, but these responses were significantly more intense in A/J mice than in CBA/J, BALB/c or C57BL/6J mice. Immunization of A/J mice with BtE induced a more intense airway eosinophil influx, higher levels of total IgE, similar airway hyperreactivity to methacholine but less intense mucous production, and lower levels of specific IgE, IgG1 and IgG2 antibodies than sensitization with OVA. Finally, immunization with a relatively low BtE dose (10 μg per subcutaneous injection per mouse) was able to sensitize A/J mice, which were the best responders to high-dose BtE immunization, for the development of allergy-associated immune and lung inflammatory responses.

Conclusions

The described short-term model of BtE-induced allergic lung disease is reproducible in different syngeneic mouse strains, and mice of the A/J strain was the most responsive to it. In addition, it was shown that OVA and BtE induce quantitatively different immune responses in A/J mice and that the experimental model can be set up with low amounts of BtE.

Allergic asthma in patients with common variable immunodeficiency

BACKGROUND

Many patients with common variable immunodeficiency (CVID) have a clinical history suggestive of allergic respiratory disease. However, in such individuals, the prevalence of asthma and the role of atopy have not been well established. The objective of this study was to evaluate pulmonary function and identify asthma in patients with CVID. We also investigated the role of IgE as a trigger of asthma in these patients.

METHODS

Sixty-two patients diagnosed with CVID underwent spirometry, as well as skin prick testing and in vitro determination of serum-specific IgE levels for aeroallergens, together with bronchial provocation with histamine and allergen.

RESULTS

The most common alteration identified through spirometry was obstructive lung disease, which was observed in 29 (47.5%) of the 62 patients evaluated. Eighteen (29.0%) of the 62 patients had a clinical history suggestive of allergic asthma. By the end of the study, asthma had been diagnosed in nine (14.5%) patients and atopy had been identified in six (9.7%). In addition, allergic asthma had been diagnosed in four patients (6.5% of the sample as a whole; 22.2% of the 18 patients with a clinical history suggestive of the diagnosis).

CONCLUSION

In this study, CVID patients testing negative for specific IgE antibodies and suspected of having allergic asthma presented a positive response to bronchial provocation tests with allergens. To our knowledge, this is the first such study. When CVID patients with a history suggestive of allergic asthma test negative on traditional tests, additional tests designed to identify allergic asthma might be conducted.

Altered lymphocyte trafficking and diminished airway reactivity in transgenic mice expressing human MMP-9 in a mouse model of asthma

Matrix metalloproteinase-9 (MMP-9) is hypothesized to facilitate leukocyte extravasation and extracellular remodeling in asthmatic airways. Careful descriptive studies have shown that MMP-9 levels are higher in the sputum of asthmatics; however, the consequence of increased MMP-9 activity has not been determined in this disease. We induced asthma in transgenic mice that express human MMP-9 in the murine lung tissue macrophage to determine the direct effect of human MMP-9 expression on airway inflammation. Transgenic (TG) and wild-type (WT) mice were immunized and challenged with ovalbumin. Forty-eight hours after the ovalbumin challenge, airway hyperresponsiveness (AHR) was measured, and inflammatory cell infiltration was evaluated in bronchoalveolar lavage fluid (BALF) and lung tissue. Baseline levels of inflammation were similar in the TG and WT groups of mice, and pulmonary eosinophilia was established in both groups by sensitization and challenge with ovalbumin. There was a significant reduction in AHR in sensitized and challenged trangenics compared with WT controls. Although total BALF cell counts were similar in both groups, the lymphocyte number in the lavage of the TG group was significantly diminished compared with the WT group (0.25 +/- 0.08 vs. 0.89 +/- 0.53; P = 0.0032). In addition, the draining lymphocytes were found to be larger in the TG animals compared with the WT mice. Equal numbers of macrophages, eosinophils, and neutrophils were seen in both groups. IL-13 levels were found to be lower in the sensitized TG compared with the WT mice. These results demonstrate an inverse relationship between human MMP-9 and AHR and suggest that MMP-9 expression alters leukocyte extravasation by reducing lymphocyte accumulation in the walls of asthmatic airways.

Investigating lung remodeling in Modul8-treated BALB/c asthmatic animals

Animal models of bronchial hyperresponsiveness have been successfully used to investigate the pathophysiology of asthma. When mice are sensitized and challenged with an allergen, such as OVA, they experience symptoms and processes similar to that of humans, and are therefore widely used as asthmatic animal models. In the current study the BALB/c murine asthmatic animal model was used to investigate the histological and ultrastructural changes that occur in the lungs of asthmatic animals that received no treatment, compared to two groups of asthmatic animals that were treated with a homeopathic immunodulator Modul8 and hydrocortisone as positive control, respectively. Eosinophil counts in the bronchial lavage of the animals were also analyzed, since it is known that eosinophil counts are increased in the bronchial lavage in asthma. Results indicated that eosinophil counts were elevated in asthmatic animals compared to the controls, but were found to be significantly decreased in the treatment groups. Also, in the asthmatic, untreated animals, histological and ultrastructural changes, typically associated with the inflammatory process were found. Both treatment groups compared well to that of the control animals, indicating that the homeopathic product might be successfully used in the treatment of asthma.

Modulation of lung inflammation by vessel dilator in a mouse model of allergic asthma

BACKGROUND

Atrial natriuretic peptide (ANP) and its receptor, NPRA, have been extensively studied in terms of cardiovascular effects. We have found that the ANP-NPRA signaling pathway is also involved in airway allergic inflammation and asthma. ANP, a C-terminal peptide (amino acid 99-126) of pro-atrial natriuretic factor (proANF) and a recombinant peptide, NP73-102 (amino acid 73-102 of proANF) have been reported to induce bronchoprotective effects in a mouse model of allergic asthma. In this report, we evaluated the effects of vessel dilator (VD), another N-terminal natriuretic peptide covering amino acids 31-67 of proANF, on acute lung inflammation in a mouse model of allergic asthma.

METHODS

A549 cells were transfected with pVD or the pVAX1 control plasmid and cells were collected 24 hrs after transfection to analyze the effect of VD on inactivation of the extracellular-signal regulated receptor kinase (ERK1/2) through western blot. Luciferase assay, western blot and RT-PCR were also performed to analyze the effect of VD on NPRA expression. For determination of VD's attenuation of lung inflammation, BALB/c mice were sensitized and challenged with ovalbumin and then treated intranasally with chitosan nanoparticles containing pVD. Parameters of airway inflammation, such as airway hyperreactivity, proinflammatory cytokine levels, eosinophil recruitment and lung histopathology were compared with control mice receiving nanoparticles containing pVAX1 control plasmid.

RESULTS

pVD nanoparticles inactivated ERK1/2 and downregulated NPRA expression in vitro, and intranasal treatment with pVD nanoparticles protected mice from airway inflammation.

CONCLUSION

VD's modulation of airway inflammation may result from its inactivation of ERK1/2 and downregulation of NPRA expression. Chitosan nanoparticles containing pVD may be therapeutically effective in preventing allergic airway inflammation.

A hypoallergenic variant of Der p 1 as a candidate for mite allergy vaccines

BACKGROUND

Recombinant hypoallergens that display reduced allergenicity but retain T-cell reactivity represent promising candidates to improve the safety and efficacy of allergen-specific vaccines or immunotherapy.

OBJECTIVE

The current study reports the immunologic characterization of a hypoallergenic variant of the major mite allergen Der p 1.

METHODS

The recombinant proform of Der p 1 (ProDer p 1) was expressed in Escherichia coli (ProDer p 1 coli), purified and characterized at the level of its secondary structure, and IgE and T-cell reactivities. Moreover, the prophylactic potential of ProDer p 1 coli vaccinations was evaluated in a murine Der p 1 sensitization model.

RESULTS

After purification and refolding, ProDer p 1 coli remained aggregated with a higher beta-sheet content and altered Der p 1 conformational epitopes compared with the correctly folded monomeric ProDer p 1 produced in Chinese hamster ovary cells. Both ProDer p 1 forms were able to retain the Der p 1-specific T-cell reactivity but direct ELISA, competitive inhibition, and rat basophil leukemia assays clearly showed that ProDer p 1 coli displays a very weak IgE reactivity. Mice vaccinations with aggregated ProDer p 1 adjuvanted with alum induced a T(H)1-biased immune response that prevented the subsequent allergic response after Der p 1 sensitization and airway challenge with aerosolized mite extracts. Furthermore, ProDer p 1 coli treatment inhibited the development of airway eosinophilia and airway hyperresponsiveness to inhaled methacholine.

CONCLUSION

Aggregated forms of Der p 1 could represent hypoallergens suitable for the prevention of mite allergy.

Differential effects of dendritic cell transfer on airway hyperresponsiveness and inflammation

Dendritic cells (DCs) are considered to be the most efficient antigen-presenting cells. Intratracheal administration of allergen-pulsed bone marrow-derived dendritic cells (BMDCs) before allergen challenge induces airway hyperresponsiveness (AHR) and inflammation. Ovalbumin (OVA)-pulsed BMDCs from wild-type (WT) mice were transferred into naive WT, CD4(-/-), CD8(-/-), or IL-13(-/-) mice. Two days (short protocol) or 10 days (long protocol) after BMDC transfer, mice were challenged with 1% OVA for 3 days and assayed 2 days later. Transfer of OVA-primed BMDCs into BALB/c or C57BL/6 mice elicited AHR in both protocols. Airway eosinophilia, Th2 cytokines, or goblet cell metaplasia were increased in the long but not short protocol. Lung T cells from both protocols produced Th2 cytokines in response to OVA in vitro. Carboxyfluorescein diacetate succinimidylester-labeled BMDCs were observed in bronchoalveolar lavage (BAL) fluid and lung parenchyma at early time points, and were detected in draining lymph nodes 48 hours after transfer. CD8(-/-) mice developed AHR comparable to WT mice in the short protocol, but decreased levels of AHR, airway eosinophilia, Th2 cytokines in BAL fluid, and goblet cell metaplasia compared with WT mice in the long protocol. CD4(-/-) or IL-13(-/-) mice did not develop AHR or airway inflammation in either protocol. These data suggest that allergen-pulsed BMDCs initiate development of AHR that is dependent initially on CD4(+) T cells, and at later time periods on CD8+ T cells and IL-13. Thus, the timing of allergen challenge after transfer of allergen-pulsed BMDC affects the development of AHR and airway inflammation.

Leukotriene B4 release from mast cells in IgE-mediated airway hyperresponsiveness and inflammation

Previous studies have shown that leukotriene B4 (LTB4), a proinflammatory lipid mediator, is linked to the development of airway hyperresponsiveness through the accumulation of IL-13-producing CD8+ T cells, which express a high affinity receptor for LTB4, BLT1 (Miyahara et al., Am J Respir Crit Care Med 2005;172:161-167; J Immunol 2005;174:4979-4984). By using leukotriene A4 hydrolase-deficient (LTA4H-/-) mice, which fail to synthesize LTB4, we determined the role of this lipid mediator in allergen-induced airway responses. Two approaches were used. In the first, LTA4H-/- mice and wild-type (LTA4H+/+) mice were systemically sensitized and challenged via the airways to ovalbumin. In the second, mice were passively sensitized with anti-ovalbumin IgE and exposed to ovalbumin via the airways. Mast cells were generated from bone marrow of LTA4H+/+ mice or LTA4H-/- mice. After active sensitization and challenge, LTA4H-/- mice showed significantly lower airway hyperresponsiveness compared with LTA4H+/+ mice, and eosinophil numbers and IL-13 levels in the bronchoalveoloar lavage of LTA4H-/- mice were also significantly lower. LTA4H-/- mice also showed decreased airway reactivity after passive sensitization and challenge. After LTA4H+/+ mast cell transfer, LTA4H-/- mice showed increased airway reactivity after passive sensitization and challenge, but not after systemic sensitization and challenge. These data confirm the important role for LTB4 in the development of altered airway responses and suggest that LTB4 secretion from mast cells is critical to eliciting increased airway reactivity after passive sensitization with allergen-specific IgE.

B cell antigen presentation promotes Th2 responses and immunopathology during chronic allergic lung disease

Background

The role of B cells in allergic asthma remains undefined. One mechanism by which B cells clearly contribute to allergic disease is via the production of specific immunoglobulin, and especially IgE. Cognate interactions with specific T cells result in T cell help for B cells, resulting in differentiation and immunoglobulin secretion. Proximal to (and required for) T cell-dependent immunoglobulin production, however, is antigen presentation by B cells. While interaction with T cells clearly has implications for B cell function and differentiation, this study investigated the role that B cells have in shaping the T cell response during chronic allergic lung disease.

Methodology/Principal Findings

In these studies, we used a clinically relevant mouse model of chronic allergic lung disease to study the role of B cells and B cell antigen presentation in this disease. In these studies we present several novel findings: 1) Lung B cells from chronically allergen challenged mice up-regulated MHC II and costimulatory molecules CD40, CD80 and CD86. 2) Using in vitro studies, B cells from the lungs of allergen challenged mice could present antigen to T cells, as assessed by T cell proliferation and the preferential production of Th2 cytokines. 3) Following chronic allergen challenge, the levels of Th2 cytokines IL-4 and IL-5 in the lungs and airways were significantly attenuated in B cell −/− mice, relative to controls. 4) B cell driven Th2 responses and mucus hyper secretion in the lungs were dependent upon MHC II expression by B cells.

Conclusions/Significance

Collectively, these results provide evidence for antigen presentation as a novel mechanism by which B cells contribute to chronic allergic disease. These findings give new insight into the mechanisms by which B cells promote asthma and other chronic diseases.

Postnatal life events affect the severity of asthmatic airway inflammation in the adult rat

Genetic and hygienic factors influence susceptibility to asthma. In autoimmune and inflammatory diseases, additional effects of the psychosocial environment have been demonstrated that might also play a role in asthma. In this study, the impact of different early postnatal stressors on an OVA-induced model of asthma was tested in adulthood. Fischer 344 rats were subjected to either repeated handling stimulation (HA), maternal separation (MS), or were left undisturbed in their first 4 wk of life. Behavioral differences were characterized at the age of 4 mo. At 5 mo of age, immunological cellular and serologic changes were investigated and experimental asthma was induced. Results show significantly increased exploratory behavior and reduced anxiety in HA rats compared with MS and controls. Without further behavioral or immunological challenges, HA animals exhibited an increased ex vivo NK cell cytotoxicity but no other obvious immunological differences. After induction of asthma, in contrast, MS animals exhibited proinflammatory effects in leukocyte subset composition including increased eosinophil numbers, whereas levels of IgE and the allergy-specific cytokine IL-13 were reduced compared with HA. There was a most remarkable increase of adrenocorticotropin in HA animals, comparing pre- to postchallenge plasma levels. These data demonstrate for the first time that early postnatal stimulative or adverse experiences exert long-lasting changes of the "neuroendocrinoimmune" interface in adulthood, resulting in either protective or aggravating mechanisms in allergic airway disease. Thus, in addition to genetic and hygienic factors, nongenetically acquired individual differences contribute to the pathobiology of asthma.

Influence of age on the development of immunological lung response in intrauterine undernourishment

OBJECTIVE

We investigated the effect of intrauterine undernourishment on some features of asthma using a model of allergic lung inflammation in rats. The effects of age at which the rats were challenged (5 and 9 wk) were also evaluated.

METHODS

Intrauterine undernourished offspring were obtained from dams that were fed 50% of the nourished diet of counterparts and were immunized at 5 and 9 wk of age. They were tested for immunoglobulin E anti-ova titers (by passive cutaneous anaphylaxis), cell count in the bronchoalveolar fluid, leukotriene concentration, airway reactivity, mucus production, and blood corticosterone and leptin concentrations 21 d after immunologic challenge.

RESULTS

Intrauterine undernourishment significantly reduced the antigen-specific immunoglobulin E production, inflammatory cell infiltration into airways, mucus secretion, and production of leukotrienes B(4)/C(4) in the lungs in both age groups compared with respective nourished rats. The increased reactivity to methacholine that follows antigen challenge was not affected by intrauterine undernourishment. Corticosterone levels increased with age in the undernourished rats' offspring, but not in the nourished rats' offspring. Undernourished offspring already presented high levels of corticosterone before inflammatory stimulus and were not modified by antigen challenge. Leptin levels increased with challenge in the nourished rats but not in the undernourished rats and could not be related to corticosterone levels in the undernourished rats.

CONCLUSION

Intrauterine undernourishment has a striking and age-dependent effect on the offspring, reducing lung allergic inflammation.

The role of anti-IgE therapy in combination with allergen specific immunotherapy for seasonal allergic rhinitis

Novel therapies that interfere specifically with immunologic mechanisms underlying allergen-induced pathology are currently in clinical evaluation. Among these is anti-IgE, which directly targets IgE serum antibodies, thus inhibiting the central mechanism of immediate-type hypersensitivity reactions. Application of anti-IgE antibodies effectively reduces IgE serum levels regardless of allergen specificity. Anti-IgE therapy has been successfully tested in patients with allergic rhinitis, asthma, and food allergy, showing significant efficacy in reducing symptom scores and the use of rescue medications. However, such therapy is limited by high costs and the requirements for permanent or every-season treatment. The advantage of specific immunotherapy (SIT) is the potential to alter the course of the disease, which has been demonstrated in patients with allergic rhinitis, insect venom allergy and, to a lesser degree, asthma. The broader application of SIT is restricted by sometimes life-threatening adverse effects. The combination of anti-IgE with SIT was suggested to be superior to each single treatment protocol in children and adolescents with allergic rhinitis. In a randomized, double-blind trial to assess the efficacy and safety of anti-IgE (omalizumab) or placebo in combination with SIT (birch pollen or grass pollen), the combination therapy reduced symptom load, the sum of daily symptom severity score plus rescue medication use, over the birch and grass pollen seasons by nearly 50% over SIT alone. These data show that the combination of anti-IgE plus SIT may be beneficial for the treatment of allergic diseases, offering improved efficacy, limited adverse effects, and potential immune-modifying effects.