Transgenic expression of survivin compensates for OX40‐deficiency in driving Th2 development and allergic inflammation

Survivin, an inhibitor of apoptosis family molecule, has been proposed as a crucial intermediate in the signaling pathways leading to T‐cell development, proliferation, and expansion. However, the importance of survivin to T‐cell‐driven inflammatory responses has not been demonstrated. Here, we show that survivin transgenic mice exhibit an increased antigen‐driven Th2 lung inflammation and that constitutive expression of survivin reversed the defective lung inflammation even in the absence of OX40 costimulation. We found that OX40‐deficient mice were compromised in generating Th2 cells, airway eosinophilia, and IgE responses. In contrast, OX40‐deficient/survivin transgenic mice generated normal Th2 responses and exhibited strong lung inflammation. These results suggest that OX40 costimulation crucially engages survivin during antigen‐mediated Th2 responses. These findings also promote the notion that OX40 costimulation regulates allergic responses or lung inflammation by targeting survivin thereby enhancing T‐cell proliferation and resulting in more differentiated Th2 cells in the allergic inflammatory response.     

T cells are necessary for ILC2 activation in house dust mite‐induced allergic airway inflammation in mice

Allergic asthma is a chronic inflammation of the airways mediated by an adaptive type 2 immune response. Upon allergen exposure, group 2 innate lymphoid cells (ILC2s) can be rapidly activated and represent an early innate source of IL‐5 and IL‐13. Here, we used a house dust mite (HDM)‐driven asthma mouse model to study the induction of ILC2s in allergic airway inflammation. In BALF, lungs, and lymph nodes, ILC2 activation is critically dependent on prior sensitization with HDM. Importantly, T cells are required for ILC2 induction, whereby T‐cell activation precedes ILC2 induction. During HDM‐driven allergic airway inflammation the accumulation of ILC2s in BALF is IL‐33 independent, although infiltrating ILC2s produce less cytokines in Il33^?/? mice. Transfer of in vitro polarized OVA‐specific OT‐II Th2 cells alone or in combination with Th17 cells followed by OVA and HDM challenge is not sufficient to induce ILC2, despite significant eosinophilic inflammation and T‐cell activation. In this asthma model, ILC2s are therefore not an early source of Th2 cytokines, but rather contribute to type 2 inflammation in which Th2 cells play a key role. Taken together, ILC2 induction in HDM‐mediated allergic airway inflammation in mice critically depends on activation of T cells.     

Thymic stromal lymphopoietin, OX40-ligand, and interleukin-25 in allergic responses

Allergic diseases are often triggered by environmental allergens that induce dominant type 2 immune responses, characterized by the infiltrated T‐helper type 2 (TH2) lymphocytes, eosinophils, and elevated TH2 cytokines. In addition to TH2 type immune responses, epithelial stress and injury linked to tissue remodelling are often observed, suggesting that epithelial cells may play important role in regulating allergic responses. Dendritic cells (DCs), the professional antigen‐presenting cells with the capabilities of sampling allergens, are considered as the key player on instructing TH2 immune responses. Whether inflamed epithelium can regulate innate immunity, such as macrophages and DCs, which in turn instructs adaptive immunity has long been hypothesized. Studies of thymic stromal lymphopoietin (TSLP), an epithelial cells‐derived cytokine, that can strongly activate DCs, provide important evidences that the epithelial barrier can trigger allergic diseases by regulating immune responses. The finding that OX40/OX40Ligand (OX40L) interactions are the molecular trigger responsible for the induction and maintenance of TH2 responses by TSLP‐activated DCs provides a plausible molecular explanation for TSLP‐mediated allergy. Recent progresses in characterizing the pro‐inflammatory IL‐17 cytokine family have added an additional layer of complexity on the regulation of allergic inflammation. TSLP–DCs can induce a robust expansion of TH2 memory cells and strengthen functional attributes by up‐regulating their surface expression of IL‐17RB (IL‐25R), the receptor for cytokine IL‐17E (IL‐25), a distinct member of IL‐17 cytokine family. IL‐17E (also known as IL‐25) produced by epithelial cells, and other innate cells, such as eosinphils, basophils, and mast cells, are shown to regulate adaptive immunity by enhancing TH2 cytokine productions. These exciting findings expand our knowledge of the complex immunological cascades that result in allergic inflammation and may provide novel therapeutic approaches for the treatment of allergic diseases.     

T cells and ILC2s are major effector cells in influenza‐induced exacerbation of allergic airway inflammation in mice

Influenza virus infection is an important cause of severe asthma exacerbations, but it remains unclear how a Th1‐mediated antiviral response triggers a prototypical Th2 disease. We investigated CD4⁺ T cells and group 2 innate lymphoid cells (ILC2s) in influenza virus‐infected mice. We found that ILC2s accumulated in the lung rapidly after influenza virus infection, but the induction of IL‐5 and IL‐13 secretion was delayed and concomitant with T cell activation. In an influenza‐induced exacerbation of allergic airway inflammation model we noticed an initial reduction of ILC2 numbers and cytokine production in broncho‐alveolar lavage compared to chronic house dust mite (HDM)‐mediated airway inflammation alone. ILC2s phenotype was characterized by low T1/ST2, ICOS, KLRG1, and CD25 expression, resembling naïve ILC2s. The contribution of ILC2s to type 2 cytokine production in the early stage of the influenza‐induced exacerbation was limited. In contrast, T cells showed increased IL‐4 and IL‐5 production when exposed to both HDM and influenza virus. Upon virus clearance, ILC2s regained an activated T1/ST2^highICOS^highKLRG1^highCD25^high phenotype paired with cytokine production and were major contributors to the type 2 cytokine milieu. Collectively, our data indicate that both T cells and ILC2s contribute to influenza‐induced exacerbation of allergic airway inflammation, but with different kinetics.     

Prenatal environmental tobacco smoke exposure increases allergic asthma risk with methylation changes in mice

Allergic asthma remains an inadequately understood disease. In utero exposure to environmental tobacco smoke (ETS) has been identified as an environmental exposure that can increase an individual's asthma risk. To improve our understanding of asthma onset and development, we examined the effect of in utero ETS exposure on allergic disease susceptibility in an asthmatic phenotype using a house dust mite (HDM) allergen‐induced murine model. Pregnant C57BL/6 mice were exposed to either filtered air or ETS during gestation, and their offspring were further exposed to HDM at 6–7 weeks old to induce allergic inflammation. Methylation in the promoter regions of allergic inflammation‐related genes and genomic DNA was quantified. Exposure to HDM resulted in the onset of allergic lung inflammation, with an increased presence of inflammatory cells, Th2 cytokines (IL‐4, IL‐5, and IL‐13), and airway remodeling. These asthmatic phenotypes were significantly enhanced when the mice had been exposed to in utero ETS. Furthermore, prenatal ETS exposure and subsequent HDM (ETS/HDM)‐induced asthmatic phenotypes agree with methylation changes in the selected asthma‐related genes, including IL‐4, IL‐5, IL‐13, INF‐γ, and FOXP3. Global DNA methylation was significantly lower in ETS/HDM‐exposed mice than that of controls, which coincides with the results observed in lung, spleen, and blood DNAs. Prenatal ETS exposure resulted in a severe increase in allergic inflammatory responses after an HDM challenge, with corresponding methylation changes. Prenatal ETS exposure may influence developmental plasticity and result in altered epigenetic programming, leading to an increased susceptibility to asthma. Environ. Mol. Mutagen. 58:423–433, 2017. © 2017 Wiley Periodicals, Inc.     

Interleukin 25 in allergic airway inflammation

T helper 2 (Th2) cells induce allergic inflammation through the production of cytokines such as interleukin (IL)-4, IL-5 and IL-13. Recently, it has been demonstrated that a novel IL-17 family cytokine IL-25 (IL-17E) is a product of activated Th2 cells and mast cells. Interestingly, when systemically administered to mice, IL-25 induces IL-4, IL-5 and IL-13 production from undefined non-T/non-B cells and then induces Th2-type immune responses such as blood eosinophilia and increased serum immunoglobulin E levels. In addition, we have recently shown that IL-25 mRNA is expressed in the lung after an inhaled antigen challenge in sensitized mice and that neutralization of the produced IL-25 by soluble IL-25 receptor decreases antigen-induced eosinophil and CD4+ T cell recruitment into the airways. Moreover, we have shown that the enforced expression of IL-25 in the lung significantly enhances antigen-induced Th2 cytokine production and eosinophil recruitment into the airways, and that the IL-25-mediated enhancement of antigen-induced eosinophil recruitment is inhibited by the depletion of CD4+ T cells. Thus, it is suggested that IL-25 plays an important role in enhancing allergic airway inflammation by a CD4+ T-cell-dependent mechanism.     

Treatment with anti‐OX40L or anti‐TSLP does not alter the frequency of T regulatory cells in allergic asthmatics

OX40‐OX40L interactions and thymic stromal lymphopoietin (TSLP) are important in the induction and maintenance of Th2 responses in allergic disease, whereas T regulatory cells (Treg) have been shown to suppress pro‐inflammatory Th2 responses. Both OX40L and TSLP have been implicated in the negative regulation of Treg. The effect of anti‐asthma therapies on Treg is not well known. Our aim was to assess the effects of two monoclonal antibody therapies (anti‐OX40L and anti‐TSLP) on Treg frequency using a human model of allergic asthma. We hypothesized that the anti‐inflammatory effects of these therapies would result in an increase in circulating Treg (CD4⁺CD25⁺CD127^lowFoxp3⁺ cells) frequency. We measured Treg using flow cytometry, and our results showed that neither allergen challenge nor monoclonal antibody therapy altered circulating Treg frequency. These data highlight the need for assessment of airway Treg and for a more complete understanding of Treg biology so as to develop pharmacologics/biologics that modulate Treg for asthma therapy.     

Costimulatory molecule OX40L is critical for both Th1 and Th2 responses in allergic inflammation

T cell activation and cytokine secretion are important mediators of inflammation in allergic asthma. The costimulatory pathway CD28/CD80/CD86 has been shown to play an important role in T cell activation in allergic asthma, but less is known about the effect of other costimulatory molecules in allergy. The costimulatory molecule OX40 ligand (OX40L), a member of the tumor necrosis factor superfamily, has been shown to be important in T cell priming and cytokine production. We investigated the role of OX40L in a murine model of allergic inflammation using OX40L(-/-) mice. In this model, following OVA sensitization and challenge, mice develop features of allergic inflammation including elevated levels of total serum IgE, pulmonary eosinophils, cytokines, and pulmonary inflammation. In the absence of OX40L, total serum IgE, pulmonary eosinophils, cytokines, and pulmonary inflammation were all significantly reduced compared to wild-type controls. Levels of eotaxin mRNA, an eosinophil-specific chemoattractant, were also markedly reduced, paralleling the significant reduction in pulmonary eosinophils. Levels of allergen-induced Th1 as well as Th2 cytokines were also significantly reduced. Together, the data support a critical role for OX40L signals in allergic responses.     

OX40 and IL‐7 play synergistic roles in the homeostatic proliferation of effector memory CD4+ T cells

T‐cell homeostasis preserves the numbers, the diversity and functional competence of different T‐cell subsets that are required for adaptive immunity. Naïve CD4⁺ T (T_N) cells are maintained in the periphery via the common γ‐chain family cytokine IL‐7 and weak antigenic signals. However, it is not clear how memory CD4⁺ T‐cell subsets are maintained in the periphery and which factors are responsible for the maintenance. To examine the homeostatic mechanisms, CFSE‐labeled CD4⁺CD44^highCD62L^low effector memory T (T_EM) cells were transferred into sublethally‐irradiated syngeneic C57BL/6 mice, and the systemic cell proliferative responses, which can be divided distinctively into fast and slow proliferations, were assessed by CFSE dye dilution. We found that the fast homeostatic proliferation of T_EM cells was strictly regulated by both antigen and OX40 costimulatory signals and that the slow proliferation was dependent on IL‐7. The simultaneous blockade of both OX40 and IL‐7 signaling completely inhibited the both fast and slow proliferation. The antigen‐ and OX40‐dependent fast proliferation preferentially expanded IL‐17‐producing helper T cells (Th17 cells). Thus, OX40 and IL‐7 play synergistic, but distinct roles in the homeostatic proliferation of CD4⁺ T_EM cells.     

Blockade of CCR4 in a humanized model of asthma reveals a critical role for DC-derived CCL17 and CCL22 in attracting Th2 cells and inducing airway inflammation

Background:  As Th2 type lymphocytes orchestrate the cardinal features of allergic asthma, inhibiting their recruitment to the lungs could be of therapeutic benefit. Although human Th2 cells express the CCR4 chemokine receptor and increased production of CCR4 ligands has been found in asthmatic airways, studies in animals have reached contradictory conclusions on whether blocking this pathway would be beneficial.
Objective:  As a lack of efficacy might be due to differences between mouse and man, we readdressed this question using a humanized severe combined immunodeficiency model of asthma.
Methods:  Mice received peripheral blood mononuclear cells from house dust mite (HDM) allergic asthmatic patients and then underwent bronchial challenge with HDM.
Results:  This resulted in marked allergic inflammation and bronchial hyper-reactivity. Administration of CCR4 blocking antibody abolished the airway eosinophilia, goblet cell hyperplasia, IgE synthesis and bronchial hyperreactivity. In this chimeric system, human CD11c+ dendritic cells (DCs) were the predominant source of CCR4 ligands, suggesting that DC-derived chemokines attract Th2 cells. In separate experiments using human DCs, in vitro exposure to HDM of DCs from HDM allergic patients but not healthy controls caused CCL17 and CCL22 release that resulted in chemoattraction of polarized human Th2 cells in a CCR4-dependent way.
Conclusions:  Taken together, our data provide proof of concept that CCR4 blockade inhibits the salient features of asthma and justify further clinical development of CCR4 antagonists for this disease.     

Induction of the specific allergic immune response is independent of proteases from the fungus Alternaria alternata

We have analyzed the importance of proteases for the induction of allergic responses against the mold Alternaria alternata. Responses induced in vivo with untreated or heat treated (protease inactivated) extracts were compared in BALB/c, C57BL/6, TLR4 KO, and MyD88 KO mice. In BALB/c mice, both extracts induced similar lung inflammation, upregulation of inflammatory mediators, Th2 cytokines, and Alternaria‐specific antibodies. However heat inactivation abrogated polyclonal IgE production. Similar results were obtained in C57BL/6 albeit lung expression of some Th2 mediators was decreased in mice stimulated with the heat‐treated extract. Treatment of the extract with protease inhibitors did not affect the induction of the allergic response either, except again for the polyclonal IgE response. Th2 responses and lung inflammation were readily induced in TLR4 knockout mice. In contrast, lung inflammation, Th2 responses, cytokine productions, and antibody synthesis were strongly suppressed in MyD88‐deficient mice. Early lung IL‐33 and IL‐1‐α expression were also suppressed. In conclusion, albeit some heat labile proteases are required for the stimulation of the polyclonal IgE secretion, fungal proteases, and TLR4 signaling are not required while MyD88 is essential for triggering the systemic immune response and for the development of lung allergic inflammation in response to Alternaria extracts.     

General,but not myeloid or type II lung epithelial cell,myeloid differentiation factor 88 deficiency abrogates house dust mite induced allergic lung inflammation

Asthma is a highly prevalent chronic allergic inflammatory disease of the airways affecting people worldwide. House dust mite (HDM) is the most common allergen implicated in human allergic asthma. HDM‐induced allergic responses are thought to depend upon activation of pathways involving Toll‐like receptors and their adaptor protein myeloid differentiation factor 88 (MyD88). We sought here to determine the role of MyD88 in myeloid and type II lung epithelial cells in the development of asthma‐like allergic disease using a mouse model. Repeated exposure to HDM caused allergic responses in control mice characterized by influx of eosinophils into the bronchoalveolar space and lung tissue, lung pathology and mucus production and protein leak into bronchoalveolar lavage fluid. All these responses were abrogated in mice with a general deficiency of MyD88 but unaltered in mice with MyD88 deficiency, specifically in myeloid or type II lung epithelial cells. We conclude that cells other than myeloid or type II lung epithelial cells are responsible for MyD88‐dependent HDM‐induced allergic airway inflammation.     

Subcutaneous immunotherapy with purified Der p1 and 2 suppresses type 2 immunity in a murine asthma model

Background

Allergen‐specific immunotherapy can induce long‐term suppression of allergic symptoms, reduce medication use, and prevent exacerbations of allergic rhinitis and asthma. Current treatment is based on crude allergen extracts, which contain immunostimulatory components such as β‐glucans, chitins, and endotoxin. Use of purified or recombinant allergens might therefore increase efficacy of treatment.

Aims

Here, we test application of purified natural group 1 and 2 allergens from Dermatophagoides pteronyssinus (Der p) for subcutaneous immunotherapy (SCIT) treatment in a house dust mite (HDM)‐driven mouse model of allergic asthma.

Materials and methods

HDM‐sensitized mice received SCIT with crude HDM extract, a mixture of purified Der p1 and 2 (DerP1/2), or placebo. Upon challenges, we measured specific immunoglobulin responses, allergen‐induced ear swelling response (ESR), airway hyperresponsiveness (AHR), and inflammation in bronchoalveolar lavage fluid (BAL) and lung tissue.

Results

ESR measurement shows suppression of early allergic response in HDM‐SCIT– and DerP1/2‐SCIT–treated mice. Both HDM‐SCIT and DerP1/2‐SCIT are able to suppress AHR and eosinophilic inflammation. In contrast, only DerP1/2‐SCIT is able to significantly suppress type 2 cytokines in lung tissue and BAL fluid. Moreover, DerP1/2‐SCIT treatment is uniquely able suppress CCL20 and showed a trend toward suppression of IL‐33, CCL17 and eotaxin levels in lung tissue.

Discussion

Taken together, these data show that purified DerP1/2‐SCIT is able to not only suppress AHR and inflammation, but also has superior activity toward suppression of Th2 cells and HDM‐induced activation of lung structural cells including airway epithelium.

Conclusions

We postulate that treatment with purified natural major allergens derived from HDM will likely increase clinical efficacy of SCIT.     

Respiratory syncytial virus protects against the subsequent development of ovalbumin‐induced allergic responses by inhibiting Th2‐type γδ T cells

Respiratory syncytial virus (RSV) infection has been hypothesized to be a risk factor for the development of allergy and asthma, but epidemiologic studies in humans still remain inconclusive. The association between RSV infection and allergic diseases may be dependent on an atopic background and previous history of RSV infection. It has been reported that RSV infection before sensitization to an allergen decreased the production of Th2‐like cytokines in the lung and the levels of allergen‐specific Th2‐type antibodies in the serum. However, the underlying mechanisms are largely unknown. In the present study, the role of pulmonary γδ T cells in RSV‐affected, allergen‐induced airway inflammation was investigated. BALB/c mice were sensitized to or challenged with ovalbumin (OVA) and infected with RSV either before or after the sensitization period. It became clear that sensitization and challenge of mice with OVA induced a large influx of γδ T cells to the lungs. However, prior RSV infection inhibited the infiltration of γδ T cells as well as activated γδ T cells, characterized by expression of CD40L or CD69 molecular in the cell surface. Moreover, prior RSV infection elevated the type 1 cytokine gene expression but suppressed type 2 cytokine expression in the lung γδ T cells. Adoptive transfer of γδ T cells from OVA‐sensitized and challenged mice increased airway inflammation, suggesting that γδ T cells may play a proinflammatory role in allergic responses. These results described here support the idea of an unknown γδ T cell‐dependent mechanism in the regulation of RSV‐affected, allergen‐induced allergic airway responses. J. Med. Virol. 85:149–156, 2012. © 2012 Wiley Periodicals, Inc.     

Critical role for OX40 ligand in the development of pathogenic Th2 cells in a murine model of asthma

Bronchial asthma is characterized by massive infiltration of eosinophils and airway hyperreactivity (AHR), which are caused by overproduction of Th2 cytokines (IL-4, IL-5, and IL-13) by allergen-specific T cells. We recently demonstrated a critical contribution of OX40 ligand (OX40L) to the development of Th2-mediated experimental leishmaniasis. In this study, we have examined the role of OX40L in the development of Th2-mediated pulmonary inflammation by utilizing OX40L-deficient mice and a neutralizing anti-OX40L mAb in a murine model of asthma. Sensitization and airway challenge with ovalbumin in wild-type BALB/c mice induced a typical allergic asthma characterized by AHR, accumulation of eosinophils, increased mucus production, and high levels of Th2 cytokines in the lung.All these asthmatic responses were not induced in OX40L-deficient BALB/c mice. Administration of neutralizing anti-OX40L mAb in wild-type BALB/c mice during the sensitization period also abolished the induction of asthmatic responses. In contrast, administration of anti-OX40L mAb during the challenge period did not inhibit the asthmatic responses. These results indicate a critical role for OX40L in the induction phase, which leads to the development of pathogenic Th2 cells, but not in the effector phase, which includes migration and activation of pathogenic Th2 cells in the lung.