Lung Tissue Multi-Layer Network Analysis Uncovers the Molecular Heterogeneity of COPD

BACKGROUND

Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous condition. We hypothesized that the unbiased integration of different COPD lung omics using a novel multi-layer approach may unravel mechanisms associated with clinical characteristics.

METHODS

We profiled mRNA, miRNA and methylome in lung tissue samples from 135 former smokers with COPD. For each omic (layer) we built a patient network based on molecular similarity. The three networks were used to build a multi-layer network, and optimization of multiplex-modularity was employed to identify patient communities across the three distinct layers. Uncovered communities were related to clinical features.

RESULTS

We identified five patient communities in the multi-layer network which were molecularly distinct and related to clinical characteristics, such as FEV1 and blood eosinophils. Two communities (C#3 and C#4) had both similarly low FEV1 values and emphysema, but were molecularly different: C#3, but not C#4, presented B and T cell signatures and a downregulation of secretory (SCGB1A1/SCGB3A1) and ciliated cells. A machine learning model was set up to discriminate C#3 and C#4 in our cohort, and to validate them in an independent cohort. Finally, using spatial transcriptomics we characterized the small airway differences between C#3 and C#4, identifying an upregulation of T/B cell homing chemokines, and bacterial response genes in C#3.

CONCLUSIONS

A novel multi-layer network analysis is able to identify clinically relevant COPD patient communities. Patients with similarly low FEV1 and emphysema can have molecularly distinct small airways and immune response patterns, indicating that different endotypes can lead to similar clinical presentation.

Development of a novel angiotensin converting enzyme 2 stimulator with broad implications in SARS-CoV2 and type 1 diabetes

Angiotensin-converting enzyme 2 (ACE2) is protective in cardiovascular disease, lung injury and diabetes yet paradoxically underlies our susceptibility to SARs-CoV2 infection and the fatal heart and lung disease it can induce. Furthermore, diabetic patients have chronic, systemic inflammation and altered ACE2 expression resulting in increased risk of severe COVID-19 and the associated mortality. A drug that could increase ACE2 activity and inhibit cellular uptake of severe acute respiratory syndrome coronavirus 2 (SARs-CoV2), thus decrease infection, would be of high relevance to cardiovascular disease, diabetes and SARs-CoV2 infection. While the need for such a drug lead was highlighted over a decade ago receiving over 600 citations,1 to date, no such drugs are available.2 Here, we report the development of a novel ACE2 stimulator, designated '2A'(international PCT filed), which is a 10 amino acid peptide derived from a snake venom, and demonstrate its in vitro and in vivo efficacy against SARs-CoV2 infection and associated lung inflammation. Peptide 2A also provides remarkable protection against glycaemic dysregulation, weight loss and disease severity in a mouse model of type 1 diabetes. No untoward effects of 2A were observed in these pre-clinical models suggesting its strong clinical translation potential.

Airway and parenchyma transcriptomics in a house dust mite model of experimental asthma

Lung transcriptomics studies in asthma have provided valuable information in the whole lung context, however, deciphering the individual contributions of the airway and parenchyma in disease pathogenesis may expedite the development of novel targeted treatment strategies. In this study, we performed transcriptomics on the airway and parenchyma using a house dust mite (HDM)-induced model of experimental asthma that replicates key features of the human disease. HDM exposure increased the expression of 3,255 genes, of which 212 were uniquely increased in the airways, 856 uniquely increased in the parenchyma, and 2187 commonly increased in both compartments. Further interrogation of these genes using a combination of network and transcription factor enrichment analyses identified several transcription factors that regulate airway and/or parenchymal gene expression, including transcription factor EC (TFEC), transcription factor PU.1 (SPI1), H2.0-like homeobox (HLX), metal response element binding transcription factor-1 (MTF1) and E74-like factor 4 (ets domain transcription factor, ELF4) involved in controlling innate immune responses. We next assessed the effects of inhibiting lung SPI1 responses using commercially available DB1976 and DB2313 on key disease outcomes. We found that both compounds had no protective effects on airway inflammation, however DB2313 (8 mg/kg) decreased mucus secreting cell number, and both DB2313 (1 mg/kg) and DB1976 (2.5 mg/kg and 1 mg/kg) reduced small airway collagen deposition. Significantly, both compounds decreased airway hyperresponsiveness. This study demonstrates that SPI1 is important in HDM-induced experimental asthma and that its pharmacological inhibition reduces HDM-induced airway collagen deposition and hyperresponsiveness.

Mitochondria-targeted Sulfide Delivery Molecules – New and Novel Players that can Suppress and Reverse Cigarette Smoke-induced Inflammasome Activity

RATIONALE

Cigarette smoke (CS) is the major risk factor in development of chronic obstructive pulmonary disease (COPD). Interventions that can prevent and/or reverse disease are urgently needed. Hydrogen sulfide (H2S) is generated in mitochondria (mt) and crucial in maintaining mt respiration, suppressing oxidative stress/inflammation. Lung H2S levels are reduced after CS exposure. Lung inflammation, mitochondrial damage and oxidative injury are exacerbated as a result of inhibition/silencing of H2S enzymes, suggesting impairment of H2S synthesis/loss of bioavailability is detrimental in COPD and negatively impacts mitochondrial health.

METHODS

We have produced novel mt-targeted H2S donors (mtH2SD) AP39 and RT01 to investigate whether these molecules could suppress and/or reverse CS-induced inflammation and lung injury. To investigate suppression, mice were exposed to CS (or air) for 8 wks (with 1.0 mg/kg). To investigate reversal, mice were exposed to CS for 8 wks followed by either 4 wks rest or continued CS exposure, each with mtH2SD (1.0 mg/kg). Airway inflammation (BALF differential cell counts, IL-1β by ELISA) and lung function were assessed.

RESULTS

Lung H2S levels were reduced and inflammasome activity increased in response to CS exposure. mtH2SD significantly suppressed CS-induced alveolar destruction, fibrosis and improved lung function. mtH2SD treatment reversed CS-induced lung neutrophil, eosinophil and macrophage infiltration, loss of lung function, and partially reversed airway resistance in both models.

CONCLUSIONS

Targeting H2S to mitochondria may be a novel therapeutic approach to prevent and/or reverse mitochondria-driven inflammation and lung injury in COPD and related diseases.

Computerized screening of G-protein coupled receptors to identify and characterize olfactory receptors

Olfactory receptors (ORs) are a group of G protein coupled receptors (GPCRs) that initiate chemical odorant signals. Although ORs are predominantly located in nasal epithelia to detect smell, these receptors are also present in peripherally in non-nasal organs/tissues. Since the quality of life and cognitive and sensorial features of sense of smell are worsened in multiple chemical sensitivity due to the interaction of ORs with offending compounds, it is important to not only differentiate these receptors from other GPCRs but also characterize these organelles to understand the underlying mechanisms of smelling disorders. The aim of this study was develop computerized programs to differentiate ORs from GPCRs. The computer program was developed on the basis of widely accepted basic algorithms. It is noteworthy that an accuracy of 95.5% was attained, a level not achieved using other established techniques for screening of ORs from GPCRs. The high accuracy rate indicates that this method of differential identification appears reliable. Our findings indicate that this novel method may be considered as a tool for identification and characterization of receptors which might aid in therapeutic approaches to human chemical-mediated sensitization.

Assessing the potential of liposomes loaded with curcumin as a therapeutic intervention in asthma

Curcumin a component of turmeric, which is derived from Curcuma longa is used as a colouring agent and as a dietary spice for centuries. Extensive studies have been done on the anti-inflammatory activity of curcumin along with its molecular mechanism involving different signalling pathways. However, the physicochemical and biological properties such as poor solubility and rapid metabolism of curcumin have led to low bioavailability and hence limits its application. Current therapies for asthma such as bronchodilators and inhaled corticosteroids (ICS) are aimed at controlling disease symptoms and prevent asthma exacerbation. However, this approach requires lifetime therapy and is associated with a constellation of side effects. This creates a clear unmet medical need and there is an urgent demand for new and more-effective treatments. The present study is aimed to formulate liposomes containing curcumin and evaluate for its anti-inflammatory effects on lipopolysaccharide (LPS)-induced inflammation on BCi-NS1.1 cell line. Curcumin and salbutamol liposomes were formulated using lipid hydration method. The prepared liposomes were characterized in terms of particle size, zeta potential, encapsulation efficiency and in-vitro release profile. The liposomes were tested on BCI-NS1.1 cell line to evaluate its anti-inflammatory properties. The various pro-inflammatory markers studied were Interleukin-6 (IL-6), Interleukin-8 (IL-8), Interleukin-1β (IL-1β) and Tumour Necrosis Factor-a (TNF-a). Additionally, molecular mechanics simulations were used to elucidate the positioning, energy minimization, and aqueous dispersion of the liposomal architecture involving lecithin and curcumin. The prepared curcumin formulation showed an average size and zeta potential of 271.3 ± 3.06 nm and -61.0 mV, respectively. The drug encapsulation efficiency of liposomal curcumin is 81.1%. Both curcumin-loaded liposomes formulation (1 μg/mL, 5 μg/mL) resulted in significant (p < 0.05) reduction in the level of pro-inflammatory marker expression such as IL-6, IL-8, IL-1β and TNF-a compared to positive control group. Liposomal curcumin with the dose of 1 μg/mL reduced the inflammatory markers more effectively compared to that of 5 μg/mL. Liposomal curcumin could be a promising intervention for asthma therapy showing their efficacy in suppressing the important pro-inflammatory markers involved in the pathogenesis of asthma.

Role of NK cells in IFN-epsilon-mediated protection against female reproductive tract infection (MUC2P.925)

Chlamydia trachomatis is the most common bacterial STI and frequently results in reproductive tract (RT) sequelae such as pelvic inflammatory disease and infertility. However, the immune processes involved in the clearance and immunopathology of Chlamydia infection are not well understood. In previous studies we showed that IFN-ε, a novel type I IFN that is exclusively and constitutively expressed in the female RT, plays an important role in protecting against Chlamydia infections. Here, we examined the effects of IFN-ɛ on cellular responses in the female RT in order to elucidate the mechanisms by which IFN-ɛ protects against Chlamydia infections. Female WT and IFN-ε-/- C57BL/6 mice were pre-treated with progesterone and infected intra-vaginally with Chlamydia muridarum or sham-infected. Uterine horns were harvested and the effects of IFN-ε deficiency on Chlamydia infection, immune factor expression and cellular infiltration were assessed using real-time qPCR and flow cytometry. We show that IFN-ε-/- mice have increased Chlamydia 16S expression in the upper RT which correlated with fewer NK cells and tissue-resident uterine NK cells at 3 days post infection. IFN-γ+ CD45+ cells were also decreased in the infected IFN-ε-/- mice, of which over 60% were NK cells. These changes were associated with reduced iNOS and STAT1 expression. These findings suggest that IFN-ε may protect against Chlamydia RT infections by potentiating the recruitment of protective IFN-γ-producing NK cells.

Tumour necrosis factor-related apoptosis inducing ligand promotes the development of experimental chronic obstructive pulmonary disease (MUC1P.905)

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and causes significant healthcare and economic burden. Cigarette smoking is a major risk factor. There is a lack of effective treatments for COPD due to the poor understanding of the underlining mechanisms. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is implicated in respiratory diseases such as asthma and pulmonary fibrosis. However, the role of TRAIL in the pathogenesis of COPD is unknown. In this study, TRAIL mRNA expression and/or protein levels in the lung (airway and parenchyma) and serum were increased in a mouse model of cigarette smoke-induced experimental COPD. Genetic deletion of TRAIL significantly reduced cigarette smoke-induced pulmonary inflammation, expression of key pro-inflammatory mediators, emphysema-like alveolar enlargement and improved lung function in experimental COPD. Interestingly, genetic deletion of TRAIL led to spontaneous small airway remodelling characterized by increased airway epithelial cell thickness and collagen deposition. Importantly, antibody-mediated neutralization of TRAIL reduced cigarette smoke-induced pulmonary inflammation, emphysema-like alveolar enlargement and small airway remodelling. Our study is the first to show that TRAIL plays an important role in the pathogenesis of COPD and provides further evidence for TRAIL being a pivotal inflammatory cytokine in respiratory diseases.

The role of miR-328 in respiratory diseases (INM3P.410)

Introduction: MicroRNAs (miRNAs) are small non-coding RNA that can bind to multiple target mRNA to repress protein production. Deregulation of miRNAs have been linked with pathogenesis of multiple human diseases. In immune cells, miRNAs regulate cell development, differentiation and production of inflammatory mediators. Aim: To investigate the roles of miRNAs in regulating immune cell function and its role in respiratory diseases. Methods: Lung miRNAs that were differentially expressed following non-typeable Haemophilus Influenzae (NTHi) challenge were identified by microarray. miRNA inhibitors (antagomirs) were used to investigate the role of miRNA in regulating bacterial clearance in in mouse models of immunosuppresion and emphysema. Results: Upon NTHi infection, 15 miRNAs were up-regulated while 49 were down-regulated by &gt; 2.5 fold in lungs. In vitro, miR-328 knockdown reduced bacterial load and increased phagocytosis by macrophages and neutrophils. Transferred of macrophages or neutrophils (deficient in miR-328) to naïve recipient mice enhanced clearance of the bacteria in vivo. Similarly, inhibition of miR-328 by antagomirs promote NTHi clearance in mouse models of immunosuppresion and emphysema. Conclusion: : Our study identify a novel role for miR-328 in the regulation of phagocytosis and provide proof of principle that miRNA pathways can be targeted in the lung and offer a potential new anti-microbial approach for the treatment of respiratory infection.

MicroRNA-21 drives severe, steroid-insensitive experimental asthma by amplifying PI3K-mediated suppression of HDAC2 (HYP7P.262)

BACKGROUND: Severe, steroid-insensitive (SSI) asthma is a substantial clinical problem. Effective treatments are urgently required, however, their development is hampered by a lack of understanding of the mechanisms that promote disease. SSI asthma is associated with respiratory infections and non-eosinophilic endotypes of disease, including neutrophilic asthma. OBJECTIVES: To develop and use mouse models of SSI neutrophilic asthma to investigate pathogenic mechanisms involving microRNA (miR)-21, phosphoinositide-3-kinase (PI3K) and histone deacetylase (HDAC)2 in order to identify new therapeutic approaches. METHODS: Novel mouse models of respiratory infection and ovalbumin-induced, SSI neutrophilic allergic airway disease (SSIAAD) in BALB/c mice were developed. The roles of infection-induced miR-21 expression and PI3K-dependent signalling in the lung were examined using a specific miR-21 inhibitor (antagomir-21) and the pan-PI3K inhibitor LY294002. RESULTS: Infection induced a miR-21-dependent, PI3K-mediated signalling pathway that decreased nuclear HDAC2 levels and promoted steroid-insensitive neutrophilic inflammation and airway hyper-responsiveness (AHR) in AAD. Inhibition of miR-21 or PI3K suppressed nuclear pAkt levels and restored HDAC2 levels and steroid sensitivity. CONCLUSIONS: We have identified a novel role for a miR-21/PI3K/HDAC2 signalling axis in SSIAAD. Our data highlights miR-21 as a novel target for treating this form of asthma.

Macrolide therapy suppresses key features of experimental steroid-sensitive and steroid-insensitive asthma (HYP2P.342)

Background Steroid-insensitive endotypes of asthma are an important clinical problem requiring effective treatments. They are associated with non-eosinophilic inflammatory responses and bacterial infections. Macrolide therapy is effective in steroid-insensitive endotypes, such as non-eosinophilic asthma, however the mechanisms of how they work is unknown. Objectives To determine the efficacy of macrolide and non-macrolide antibiotic treatments in infection-induced, severe, steroid-insensitive allergic airways disease (SSIAAD). Methods Mouse models of Chlamydia and Haemophilus lung infection-induced SSIAAD were used to investigate the effects of clarithromycin and amoxicillin treatment on immune responses and AHR in steroid-sensitive AAD and SSIAAD compared to dexamethasone treatment. Results Amoxicillin and clarithromycin had similar anti-microbial effects on infection. Amoxicillin did not suppress either form of AAD, but restored steroid sensitivity in SSIAAD by reducing infection. In contrast, clarithromycin alone widely suppressed inflammation and AHR in both steroid-sensitive and SSIAAD. This occurred through reductions in both Th2 responses that drive steroid-sensitive, eosinophilic AAD, and TNF-α and IL-17 responses that induce neutrophilic SSIAAD. Conclusions Macrolides have broad anti-inflammatory effects that are independent of their anti-microbial effects. The specific responses suppressed are dependent upon the responses that dominate during disease

Nontypeable Haemophilus influenzae induces sustained lung oxidative stress and protease expression

Nontypeable Haemophilus influenzae (NTHi) is a prevalent bacterium found in a variety of chronic respiratory diseases. The role of this bacterium in the pathogenesis of lung inflammation is not well defined. In this study we examined the effect of NTHi on two important lung inflammatory processes 1), oxidative stress and 2), protease expression. Bronchoalveolar macrophages were obtained from 121 human subjects, blood neutrophils from 15 subjects, and human-lung fibroblast and epithelial cell lines from 16 subjects. Cells were stimulated with NTHi to measure the effect on reactive oxygen species (ROS) production and extracellular trap formation. We also measured the production of the oxidant, 3-nitrotyrosine (3-NT) in the lungs of mice infected with this bacterium. NTHi induced widespread production of 3-NT in mouse lungs. This bacterium induced significantly increased ROS production in human fibroblasts, epithelial cells, macrophages and neutrophils; with the highest levels in the phagocytic cells. In human macrophages NTHi caused a sustained, extracellular production of ROS that increased over time. The production of ROS was associated with the formation of macrophage extracellular trap-like structures which co-expressed the protease metalloproteinase-12. The formation of the macrophage extracellular trap-like structures was markedly inhibited by the addition of DNase. In this study we have demonstrated that NTHi induces lung oxidative stress with macrophage extracellular trap formation and associated protease expression. DNase inhibited the formation of extracellular traps.

Macrolides suppress key features of experimental steroid-sensitive and steroid-resistant asthma (P6229)

Steroid-resistant asthma is an important clinical problem and effective therapies are urgently required. Macrolides have been shown to be efficacious in treating steroid-resistant forms of asthma. However, how these immunomodulatory antibiotics induce their effects is not known. Using mouse models of Chlamydia and Haemophilus lung infection and ovalbumin-induced allergic airway disease (AAD) we have previously shown that both infections induce airways hyperresponsiveness (AHR) and neutrophilic inflammation in AAD that is resistant to steroid treatment. In the current study the effects of clarithromycin versus amoxicillin on immune responses in Th2-associated, steroid-sensitive eosinophilic and infection-induced, Th1/Th17-associated, steroid-resistant neutrophilic AAD was assessed. We show that clarithromycin, but not amoxicillin, treatment reduces AHR and inflammation in both steroid-sensitive and steroid-resistant AAD. Suppression of these features of disease was associated with a reduction in a number of Th1, Th2 and Th17-associated immune factors. Significantly, clarithromycin treatment reduced Th2-associated factors in steroid-sensitive AAD and Th1/Th17-associated factors in infection-induced, steroid-resistant AAD. These findings suggest that macrolide treatment can have broad anti-inflammatory effects on immune responses in the asthmatic lung and that the specific immune responses that are suppressed may be dependent on the responses that predominate during disease.

A short-term model of COPD identifies a role for mast cell tryptase (P3242)

Cigarette smoke-induced chronic obstructive pulmonary disease (COPD) is a life-threatening inflammatory disorder of the lung. The development of effective therapies for COPD has been hampered by the lack of an animal model that mimics the human disease in a short time-frame.We have created a mouse model of cigarette smoke-induced COPD that develops the hallmark features of the human condition in a short amount of time. Tightly controlled amounts of cigarette smoke were delivered to the airways of mice, and the development of the pathological features of COPD were assessed. The roles of macrophages and mast cell (MC) tryptase in pathogenesis were evaluated using depletion and in vitro studies and MC protease-6 deficient mice. After 8 weeks of smoke exposure, wild-type mice developed chronic inflammation, mucus hypersecretion, airway remodeling, emphysema, and reduced lung function. These characteristic features of COPD were glucocorticoid-resistant and did not spontaneously resolve. Systemic effects on skeletal muscle and the heart, and increased susceptibility to respiratory infections also were observed. We demonstrate here that macrophages and tryptase-expressing MCs were required for the development of COPD. Recombinant MC tryptase induced pro-inflammatory responses from cultured macrophages. This model can be used to better understand multiple aspects of COPD pathogenesis.

The role of miRNA in regulating bacterial clearance (P1273)

RATIONALE MicroRNAs (miRNAs) are small non-coding RNA that can bind to multiple target mRNA to repress protein production. While the expressions of specific miRNAs are known to be dysregulated in multiple human diseases, the role of miRNAs in regulating bacterial infection is unclear. Our aim is to investigate the roles of miRNA in regulating these processes. METHODS BALB/c mice were challenged with low doses of NTHi. Lung miRNAs that were differentially expressed were identified by microarray. miRNA inhibitors (antagomirs) were used to knockdown miRNA expression to investigate the roles of miRNA in bacterial clearance in vitro and in vivo. RESULTS Upon NTHi infection, 20 miRNAs were up-regulated while 52 were down-regulated by &gt; 2.5 fold. Interestingly, knockdown of a specific miRNA in vitro decreased bacterial load and increased phagocytosis by macrophages and neutrophils. Similarly, transfer of macrophages or neutrophils deficient in miRNA into naïve recipient mice leads to enhance clearance of the bacteria in vivo. This enhance clearance is independent of cellular infiltration. Inhibiting miRNA may play a protective role by enhancing the function of innate immune cells during bacterial infection. CONCLUSION Our study suggests that miRNA may play important roles in regulating the innate immune response to bacterial infection.

Constitutive IL-13 promotes respiratory chlamydial infection and infection-induced chronic airway hyper-responsiveness (175.18)

We have previously shown that chlamydial lung infections in early-life drive the development of chronic airway hyper-responsiveness (AHR). To elucidate the mechanisms involved, we used a murine model of chlamydial lung infection, to investigate the influence of IL-13 on infection and infection-induced AHR. Infected IL-13-/- mice had less severe infection, reduced inflammation (neutrophils, dendritic cells, macrophages and T cells), less mucus secreting cells (MSCs) in the airways and attenuated AHR. More severe infection in wild-type (WT) mice was associated with the development of alternatively activated macrophages (increased Arg-1, FIZZ-1 and Ym-1), which were suppressed in IL-13-/- mice. Surprisingly, infection of WT mice did not induce any detectable increase in IL-13 expression. However, infection decreased the level of the IL-13 decoy receptor (IL-13Rα2), which may allow constitutive IL-13 to signal. Interestingly, reconstitution of IL-13 in IL-13-/- mice restored infection-induced inflammation and MSC formation, but not AHR. Furthermore, infection-induced inflammation and mucus were Stat-6-independent, whilst infection-induced AHR was dependent upon Stat-6. Thus, early-life respiratory chlamydial infection results in decreased decoy receptor expression, which allows constitutive IL-13 to signal and promote more severe infection, which drives the development of chronic AHR that persists into adulthood.

Pneumococcal vaccination may induce anti-oxidized low-density lipoprotein antibodies that have potentially protective effects against cardiovascular disease

Many animal and human studies have found an inverse association between anti-oxidized low-density lipoprotein (oxLDL) antibodies (anti-oxLDL) and atherosclerotic burden. Furthermore, anti-oxLDL antibodies have been shown to cause regression of atherosclerotic plaque in mice. Animal studies indicate that the 23-valent pneumococcal vaccine may induce the production of these potentially protective anti-oxLDL antibodies, and human epidemiological studies support their potentially beneficial effect in reducing cardiovascular events. Here we describe the association between self-reported pneumococcal vaccination, vaccination verified by linkage to health records, and anti-pneumococcal antibody titers, and anti-ox-LDL titers in a group of 116 older people. We found a bimodal distribution of anti-oxLDL antibodies, and a significant association between pneumococcal IgG and anti-oxLDL antibody titers that remained after multivariate adjustment for potential confounders (p=0.04). There was no significant association between self-reported vaccination or vaccination verified by health record linkage and ox-LDL titers, which may be due to reporting error or variability in response to the vaccine. These results support a mechanistic link between pneumococcal vaccination and a potential protective effect on cardiovascular disease, and indicate that self-reported or verified vaccine status may not be sufficient to detect this association.

Induction of regulatory T cells by a novel immunoregulatory therapy suppresses the development of allergic airways disease (97.10)

Evidence suggests that exposure to Streptococcus pneumoniae may be protective against asthma. We have identified key S. pneumoniae components that form an immunoregulatory therapy (IRT) and suppress the development of allergic airways disease (AAD) using mouse models. AAD was induced in adult BALB/c mice by intraperitoneal sensitization and intranasal challenge with ovalbumin. At the time of sensitization, the IRT was administered intratracheally. IRT treatment suppressed hallmark features of AAD including eosinophil influx, local and systemic Th2 cytokines, airways hyperresponsiveness and mucus hypersecretion. A time course analysis showed that the IRT induced CD4+CD25+Foxp3+ Tregs in the lymph nodes 4 days post treatment. This was associated with increased IL-2, TGF-β and Foxp3 expression in the lungs. IRT treatment also increased the proportion of CD4+CD25+/- cells expressing Foxp3 in the lungs and expression of markers associated with Treg function, during the induction of AAD. Anti-CD25 administration 3 days before IRT treatment abolished the suppressive effects on AAD. However, anti-CD25 administration 9 days after IRT treatment had no effect. This indicated a requirement for IL-2 signalling via CD25 (IL-2R) during the induction of Tregs by the IRT treatment. In conclusion, a S. pneumoniae-based IRT induces CD25-dependent Tregs, suppresses the development of AAD and may be useful as a novel therapy for asthma.