Airway-delivered short-chain fatty acid acetate boosts antiviral immunity during rhinovirus infection.

BACKGROUND: Microbiota are recognized to play a major role in regulation of immunity through release of immunomodulatory metabolites such as short-chain fatty acids (SCFAs). Rhinoviruses (RVs) induce upper respiratory tract illnesses and precipitate exacerbations of asthma and chronic obstructive pulmonary disease through poorly understood mechanisms. Local interactions between SCFAs and antiviral immune responses in the respiratory tract have not been previously investigated. OBJECTIVE: We sought to investigate whether pulmonary metabolite manipulation through lung-delivered administration of SCFAs can modulate antiviral immunity to RV infection. METHODS: We studied the effects of intranasal administration of the SCFAs acetate, butyrate, and propionate on basal expression of antiviral signatures, and of acetate in a mouse model of RV infection and in RV-infected lung epithelial cell lines. We additionally assessed the effects of acetate, butyrate, and propionate on RV infection in differentiated human primary bronchial epithelial cells. RESULTS: Intranasal acetate administration induced basal upregulation of IFN-ß, an effect not observed with other SCFAs. Butyrate induced RIG-I expression. Intranasal acetate treatment of mice increased interferon-stimulated gene and IFN-λ expression during RV infection and reduced lung virus loads at 8 hours postinfection. Acetate ameliorated virus-induced proinflammatory responses with attenuated pulmonary mucin and IL-6 expression observed at day 4 and 6 postinfection. This interferon-enhancing effect of acetate was confirmed in human bronchial and alveolar epithelial cell lines. In differentiated primary bronchial epithelial cells, butyrate treatment better modulated IFN-ß and IFN-λ gene expression during RV infection. CONCLUSIONS: SCFAs augment antiviral immunity and reduce virus load and proinflammatory responses during RV infection.

Airway mucins promote immunopathology in virus-exacerbated chronic obstructive pulmonary disease.

The respiratory tract surface is protected from inhaled pathogens by a secreted layer of mucus rich in mucin glycoproteins. Abnormal mucus accumulation is a cardinal feature of chronic respiratory diseases, but the relationship between mucus and pathogens during exacerbations is poorly understood. We identified elevations in airway mucin 5AC (MUC5AC) and MUC5B concentrations during spontaneous and experimentally induced chronic obstructive pulmonary disease (COPD) exacerbations. MUC5AC was more sensitive to changes in expression during exacerbation and was therefore more predictably associated with viral load, inflammation, symptom severity, decrements in lung function, and secondary bacterial infections. MUC5AC was functionally related to inflammation, as Muc5ac-deficient (Muc5ac-/-) mice had attenuated RV-induced (RV-induced) airway inflammation, and exogenous MUC5AC glycoprotein administration augmented inflammatory responses and increased the release of extracellular adenosine triphosphate (ATP) in mice and human airway epithelial cell cultures. Hydrolysis of ATP suppressed MUC5AC augmentation of RV-induced inflammation in mice. Therapeutic suppression of mucin production using an EGFR antagonist ameliorated immunopathology in a mouse COPD exacerbation model. The coordinated virus induction of MUC5AC and MUC5B expression suggests that non-Th2 mechanisms trigger mucin hypersecretion during exacerbations. Our data identified a proinflammatory role for MUC5AC during viral infection and suggest that MUC5AC inhibition may ameliorate COPD exacerbations.

Effect of CRTH2 antagonism on the response to experimental rhinovirus infection in asthma: a pilot randomised controlled trial.

BACKGROUND AND AIMS: The chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) antagonist timapiprant improved lung function and asthma control in a phase 2 study, with evidence suggesting reduced exacerbations. We aimed to assess whether timapiprant attenuated or prevented asthma exacerbations induced by experimental rhinovirus (RV) infection. We furthermore hypothesised that timapiprant would dampen RV-induced type 2 inflammation and consequently improve antiviral immune responses. METHODS: Atopic patients with partially controlled asthma on maintenance inhaled corticosteroids were randomised to timapiprant (n=22) or placebo (n=22) and challenged with RV-A16 3 weeks later. The primary endpoint was the cumulative lower respiratory symptom score over the 14 days post infection. Upper respiratory symptoms, spirometry, airway hyperresponsiveness, exhaled nitric oxide, RV-A16 virus load and soluble mediators in upper and lower airways samples, and CRTH2 staining in bronchial biopsies were additionally assessed before and during RV-A16 infection. RESULTS: Six subjects discontinued the study and eight were not infected; outcomes were assessed in 16 timapiprant-treated and 14 placebo-treated, successfully infected subjects. There were no differences between treatment groups in clinical exacerbation severity including cumulative lower respiratory symptom score day 0-14 (difference 3.0 (95% CI -29.0 to 17.0), p=0.78), virus load, antiviral immune responses, or RV-A16-induced airway inflammation other than in the bronchial biopsies, where CRTH2 staining was increased during RV-A16 infection in the placebo-treated but not the timapiprant-treated group. Timapiprant had a favourable safety profile, with no deaths, serious adverse events or drug-related withdrawals. CONCLUSION: Timapiprant treatment had little impact on the clinicopathological changes induced by RV-A16 infection in partially controlled asthma.

Pulmonary Innate Lymphoid Cell Responses during Rhinovirus-induced Asthma Exacerbations In Vivo: A Clinical Trial.

Rationale: Type 2 innate lymphoid cells (ILC2s) are significant sources of type 2 cytokines, which are implicated in the pathogenesis of asthma and asthma exacerbations. The role of ILC2s in virus-induced asthma exacerbations is not well characterized. Objectives: To characterize pulmonary ILC responses following experimental rhinovirus challenge in patients with moderate asthma and healthy subjects. Methods: Patients with moderate asthma and healthy subjects were inoculated with rhinovirus-16 and underwent bronchoscopy at baseline and at Day 3, and Day 8 after inoculation. Pulmonary ILC1s and ILC2s were quantified in bronchoalveolar lavage using flow cytometry. The ratio of bronchoalveolar lavage ILC2:ILC1 was assessed to determine their relative contributions to the clinical and immune response to rhinovirus challenge. Measurements and Main Results: At baseline, ILC2s were significantly higher in patients with asthma than in healthy subjects. At Day 8, ILC2s significantly increased from baseline in both groups, which was significantly higher in patients with asthma than in healthy subjects (all comparisons P < 0.05). In healthy subjects, ILC1s increased from baseline at Day 3 (P = 0.001), while in patients with asthma, ILC1s increased from baseline at Day 8 (P = 0.042). Patients with asthma had significantly higher ILC2:ILC1 ratios at baseline (P = 0.024) and Day 8 (P = 0.005). Increased ILC2:ILC1 ratio in patients with asthma correlated with clinical exacerbation severity and type 2 cytokines in nasal mucosal lining fluid. Conclusions: An ILC2-predominant inflammatory profile in patients with asthma was associated with increased severity and duration of rhinovirus infection compared with healthy subjects, supporting the potential role of ILC2s in the pathogenesis of virus-induced asthma exacerbations.

Inhaled corticosteroids downregulate the SARS-CoV-2 receptor ACE2 in COPD through suppression of type I interferon.

BACKGROUND: The mechanisms underlying altered susceptibility and propensity to severe Coronavirus disease 2019 (COVID-19) disease in at-risk groups such as patients with chronic obstructive pulmonary disease (COPD) are poorly understood. Inhaled corticosteroids (ICSs) are widely used in COPD, but the extent to which these therapies protect or expose patients to risk of severe COVID-19 is unknown. OBJECTIVE: The aim of this study was to evaluate the effect of ICSs following pulmonary expression of the SARS-CoV-2 viral entry receptor angiotensin-converting enzyme-2 (ACE2). METHODS: We evaluated the effect of ICS administration on pulmonary ACE2 expression in vitro in human airway epithelial cell cultures and in vivo in mouse models of ICS administration. Mice deficient in the type I IFN-α/ß receptor (Ifnar1-/-) and administration of exogenous IFN-ß were used to study the functional role of type-I interferon signaling in ACE2 expression. We compared sputum ACE2 expression in patients with COPD stratified according to use or nonuse of ICS. RESULTS: ICS administration attenuated ACE2 expression in mice, an effect that was reversed by exogenous IFN-ß administration, and Ifnar1-/- mice had reduced ACE2 expression, indicating that type I interferon contributes mechanistically to this effect. ICS administration attenuated expression of ACE2 in airway epithelial cell cultures from patients with COPD and in mice with elastase-induced COPD-like changes. Compared with ICS nonusers, patients with COPD who were taking ICSs also had reduced sputum expression of ACE2. CONCLUSION: ICS therapies in COPD reduce expression of the SARS-CoV-2 entry receptor ACE2. This effect may thus contribute to altered susceptibility to COVID-19 in patients with COPD.

Bronchial mucosal inflammation and illness severity in response to experimental rhinovirus infection in COPD.

BACKGROUND: Respiratory viral infection causes chronic obstructive pulmonary disease (COPD) exacerbations. We previously reported increased bronchial mucosa eosinophil and neutrophil inflammation in patients with COPD experiencing naturally occurring exacerbations. But it is unclear whether virus per se induces bronchial mucosal inflammation, nor whether this relates to exacerbation severity. OBJECTIVES: We sought to determine the extent and nature of bronchial mucosal inflammation following experimental rhinovirus (RV)-16-induced COPD exacerbations and its relationship to disease severity. METHODS: Bronchial mucosal inflammatory cell phenotypes were determined at preinfection baseline and following experimental RV infection in 17 Global Initiative for Chronic Obstructive Lung Disease stage II subjects with COPD and as controls 20 smokers and 11 nonsmokers with normal lung function. No subject had a history of asthma/allergic rhinitis: all had negative results for aeroallergen skin prick tests. RESULTS: RV infection increased the numbers of bronchial mucosal eosinophils and neutrophils only in COPD and CD8+ T lymphocytes in patients with COPD and nonsmokers. Monocytes/macrophages, CD4+ T lymphocytes, and CD20+ B lymphocytes were increased in all subjects. At baseline, compared with nonsmokers, subjects with COPD and smokers had increased numbers of bronchial mucosal monocytes/macrophages and CD8+ T lymphocytes but fewer numbers of CD4+ T lymphocytes and CD20+ B lymphocytes. The virus-induced inflammatory cells in patients with COPD were positively associated with virus load, illness severity, and reductions in lung function. CONCLUSIONS: Experimental RV infection induces bronchial mucosal eosinophilia and neutrophilia only in patients with COPD and monocytes/macrophages and lymphocytes in both patients with COPD and control subjects. The virus-induced inflammatory cell phenotypes observed in COPD positively related to virus load and illness severity. Antiviral/anti-inflammatory therapies could attenuate bronchial inflammation and ameliorate virus-induced COPD exacerbations.

Inflammation and infections in unreported chronic obstructive pulmonary disease exacerbations.

Purpose: COPD patients often do not report acute exacerbations to healthcare providers - unreported exacerbations. It is not known whether variances in symptoms, airway obstruction, aetiology and inflammatory responses account for differences in reporting of COPD exacerbations. The aims of the study were to compare symptoms, lung function changes, aetiology and inflammatory markers between exacerbations that were reported to healthcare providers or treated, with those that were unreported and untreated. Patients and methods: We recruited a cohort of COPD patients and collected clinical data and blood and airway samples when stable and during acute exacerbations. Virological and bacterial analyses were carried out and inflammatory markers measured. Results: We found no differences in symptoms, lung function, incidence of infection and inflammatory markers between reported and unreported exacerbations. Subjects who reported all exacerbations had higher BODE scores, lower FEV1 and more exacerbations compared with those who did not. Conclusion: The failure to report exacerbations is not related to the severity, aetiology or inflammatory profile of the exacerbation. Patients with less severe COPD and less frequent exacerbations are less likely to report exacerbations. The decision to report an exacerbation is not an objective marker of exacerbation severity and therefore studies that do not count unreported exacerbations will underestimate the frequency of clinically significant exacerbations. A better understanding of the factors that determine non-reporting of exacerbations is required to improve exacerbation reporting. Trial registration: ClinicalTrials.gov Identifier: NCT01376830. Registered June 17, 2011.

Corticosteroid suppression of antiviral immunity increases bacterial loads and mucus production in COPD exacerbations.

Inhaled corticosteroids (ICS) have limited efficacy in reducing chronic obstructive pulmonary disease (COPD) exacerbations and increase pneumonia risk, through unknown mechanisms. Rhinoviruses precipitate most exacerbations and increase susceptibility to secondary bacterial infections. Here, we show that the ICS fluticasone propionate (FP) impairs innate and acquired antiviral immune responses leading to delayed virus clearance and previously unrecognised adverse effects of enhanced mucus, impaired antimicrobial peptide secretion and increased pulmonary bacterial load during virus-induced exacerbations. Exogenous interferon-ß reverses these effects. FP suppression of interferon may occur through inhibition of TLR3- and RIG-I virus-sensing pathways. Mice deficient in the type I interferon-α/ß receptor (IFNAR1-/-) have suppressed antimicrobial peptide and enhanced mucin responses to rhinovirus infection. This study identifies type I interferon as a central regulator of antibacterial immunity and mucus production. Suppression of interferon by ICS during virus-induced COPD exacerbations likely mediates pneumonia risk and raises suggestion that inhaled interferon-ß therapy may protect.

Role of airway glucose in bacterial infections in patients with chronic obstructive pulmonary disease.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) have increased susceptibility to respiratory tract infection, which contributes to disease progression and mortality, but mechanisms of increased susceptibility to infection remain unclear. OBJECTIVES: The aim of this study was to determine whether glucose concentrations were increased in airway samples (nasal lavage fluid, sputum, and bronchoalveolar lavage fluid) from patients with stable COPD and to determine the effects of viral infection on sputum glucose concentrations and how airway glucose concentrations relate to bacterial infection. METHODS: We measured glucose concentrations in airway samples collected from patients with stable COPD and smokers and nonsmokers with normal lung function. Glucose concentrations were measured in patients with experimentally induced COPD exacerbations, and these results were validated in patients with naturally acquired COPD exacerbations. Relationships between sputum glucose concentrations, inflammatory markers, and bacterial load were examined. RESULTS: Sputum glucose concentrations were significantly higher in patients with stable COPD compared with those in control subjects without COPD. In both experimental virus-induced and naturally acquired COPD exacerbations, sputum and nasal lavage fluid glucose concentrations were increased over baseline values. There were significant correlations between sputum glucose concentrations and sputum inflammatory markers, viral load, and bacterial load. Airway samples with higher glucose concentrations supported more Pseudomonas aeruginosa growth in vitro. CONCLUSIONS: Airway glucose concentrations are increased in patients with stable COPD and further increased during COPD exacerbations. Increased airway glucose concentrations might contribute to bacterial infections in both patients with stable and those with exacerbated COPD. This has important implications for the development of nonantibiotic therapeutic strategies for the prevention or treatment of bacterial infection in patients with COPD.

Corrigendum: Host DNA released by NETosis promotes rhinovirus-induced type-2 allergic asthma exacerbation.

This corrects the article DOI: 10.1038/nm.4332.

Host DNA released by NETosis promotes rhinovirus-induced type-2 allergic asthma exacerbation.

Respiratory viral infections represent the most common cause of allergic asthma exacerbations. Amplification of the type-2 immune response is strongly implicated in asthma exacerbation, but how virus infection boosts type-2 responses is poorly understood. We report a significant correlation between the release of host double-stranded DNA (dsDNA) following rhinovirus infection and the exacerbation of type-2 allergic inflammation in humans. In a mouse model of allergic airway hypersensitivity, we show that rhinovirus infection triggers dsDNA release associated with the formation of neutrophil extracellular traps (NETs), known as NETosis. We further demonstrate that inhibiting NETosis by blocking neutrophil elastase or by degrading NETs with DNase protects mice from type-2 immunopathology. Furthermore, the injection of mouse genomic DNA alone is sufficient to recapitulate many features of rhinovirus-induced type-2 immune responses and asthma pathology. Thus, NETosis and its associated extracellular dsDNA contribute to the pathogenesis and may represent potential therapeutic targets of rhinovirus-induced asthma exacerbations.

A Comprehensive Evaluation of Nasal and Bronchial Cytokines and Chemokines Following Experimental Rhinovirus Infection in Allergic Asthma: Increased Interferons (IFN-γ and IFN-λ) and Type 2 Inflammation (IL-5 and IL-13).

BACKGROUND: Rhinovirus infection is a major cause of asthma exacerbations. OBJECTIVES: We studied nasal and bronchial mucosal inflammatory responses during experimental rhinovirus-induced asthma exacerbations. METHODS: We used nasosorption on days 0, 2-5 and 7 and bronchosorption at baseline and day 4 to sample mucosal lining fluid to investigate airway mucosal responses to rhinovirus infection in patients with allergic asthma (n=28) and healthy non-atopic controls (n=11), by using a synthetic absorptive matrix and measuring levels of 34 cytokines and chemokines using a sensitive multiplex assay. RESULTS: Following rhinovirus infection asthmatics developed more upper and lower respiratory symptoms and lower peak expiratory flows compared to controls (all P<0.05). Asthmatics also developed higher nasal lining fluid levels of an anti-viral pathway (including IFN-γ, IFN-λ/IL-29, CXCL11/ITAC, CXCL10/IP10 and IL-15) and a type 2 inflammatory pathway (IL-4, IL-5, IL-13, CCL17/TARC, CCL11/eotaxin, CCL26/eotaxin-3) (area under curve day 0-7, all P<0.05). Nasal IL-5 and IL-13 were higher in asthmatics at day 0 (P<0.01) and levels increased by days 3 and 4 (P<0.01). A hierarchical correlation matrix of 24 nasal lining fluid cytokine and chemokine levels over 7days demonstrated expression of distinct interferon-related and type 2 pathways in asthmatics. In asthmatics IFN-γ, CXCL10/IP10, CXCL11/ITAC, IL-15 and IL-5 increased in bronchial lining fluid following viral infection (all P<0.05). CONCLUSIONS: Precision sampling of mucosal lining fluid identifies robust interferon and type 2 responses in the upper and lower airways of asthmatics during an asthma exacerbation. Nasosorption and bronchosorption have potential to define asthma endotypes in stable disease and at exacerbation.

Efficacy of novel antibody-based drugs against rhinovirus infection: In vitro and in vivo results.

Rhinoviruses (RVs) cause the common cold and are associated with exacerbations of chronic inflammatory respiratory diseases, especially asthma and chronic obstructive pulmonary disease (COPD). We have assessed the antiviral drugs Anaferon for Children (AC) and Ergoferon (containing AC as one of the active pharmaceutical ingredients) in in vitro and in vivo experimental models, in order to evaluate their anti-rhinoviral and immunomodulatory potential. HeLa cells were pretreated with AC, and levels of the interferon-stimulated gene (ISG), 2'-5'-oligoadenylate synthetase 1 (OAS1-A) and viral replication were analyzed. In a mouse model of RV-induced exacerbation of allergic airway inflammation we administered Ergoferon and analyzed its effect on type I (IFN-ß), type II (IFN-γ) and type III (IFN-λ) IFNs induction, cell counts in bronchoalveolar lavage (BAL), cytokine (interleukin (IL)-4; IL-6) and chemokine (CXCL10/IP-10; CXCL1/KC) levels. It was shown that AC increased OAS1-А production and significantly decreased viral replication in vitro. Increased IFNs expression together with reduced neutrophils/lymphocytes recruitment and correlated IL-4/IL-6 declination was demonstrated for Ergoferon in vivo. However, there was no effect on examined chemokines. We conclude that AC and Ergoferon possess effects against RV infection and may have potential as novel therapies against RV-induced exacerbations of asthma.

Tbet Deficiency Causes T Helper Cell Dependent Airways Eosinophilia and Mucus Hypersecretion in Response to Rhinovirus Infection.

Current understanding of adaptive immune, particularly T cell, responses to human rhinoviruses (RV) is limited. Memory T cells are thought to be of a primarily T helper 1 type, but both T helper 1 and T helper 2 memory cells have been described, and heightened T helper 2/ lessened T helper 1 responses have been associated with increased RV-induced asthma exacerbation severity. We examined the contribution of T helper 1 cells to RV-induced airways inflammation using mice deficient in the transcription factor T-Box Expressed In T Cells (Tbet), a critical controller of T helper 1 cell differentiation. Using flow cytometry we showed that Tbet deficient mice lacked the T helper 1 response of wild type mice and instead developed mixed T helper 2/T helper 17 responses to RV infection, evidenced by increased numbers of GATA binding protein 3 (GATA-3) and RAR-related orphan receptor gamma t (RORγt), and interleukin-13 and interleukin-17A expressing CD4+ T cells in the lung. Forkhead box P3 (FOXP3) and interleukin-10 expressing T cell numbers were unaffected. Tbet deficient mice also displayed deficiencies in lung Natural Killer, Natural Killer T cell and γδT cell responses, and serum neutralising antibody responses. Tbet deficient mice exhibited pronounced airways eosinophilia and mucus production in response to RV infection that, by utilising a CD4+ cell depleting antibody, were found to be T helper cell dependent. RV induction of T helper 2 and T helper 17 responses may therefore have an important role in directly driving features of allergic airways disease such as eosinophilia and mucus hypersecretion during asthma exacerbations.

Oxidative and Nitrosative Stress and Histone Deacetylase-2 Activity in Exacerbations of COPD.

BACKGROUND: Respiratory virus infections are commonly associated with COPD exacerbations, but little is known about the mechanisms linking virus infection to exacerbations. Pathogenic mechanisms in stable COPD include oxidative and nitrosative stress and reduced activity of histone deacetylase-2 (HDAC2), but their roles in COPD exacerbations is unknown. We investigated oxidative and nitrosative stress (O&NS) and HDAC2 in COPD exacerbations using experimental rhinovirus infection. METHODS: Nine subjects with COPD (Global Initiative for Chronic Obstructive Lung Disease stage II), 10 smokers, and 11 nonsmokers were successfully infected with rhinovirus. Markers of O&NS-associated cellular damage, and inflammatory mediators and proteases were measured in sputum, and HDAC2 activity was measured in sputum and bronchoalveolar macrophages. In an in vitro model, monocyte-derived THP-1 cells were infected with rhinovirus and nitrosylation and activity of HDAC2 was measured. RESULTS: Rhinovirus infection induced significant increases in airways inflammation and markers of O&NS in subjects with COPD. O&NS markers correlated with virus load and inflammatory markers. Macrophage HDAC2 activity was reduced during exacerbation and correlated inversely with virus load, inflammatory markers, and nitrosative stress. Sputum macrophage HDAC2 activity pre-infection was inversely associated with sputum virus load and inflammatory markers during exacerbation. Rhinovirus infection of monocytes induced nitrosylation of HDAC2 and reduced HDAC2 activity; inhibition of O&NS inhibited rhinovirus-induced inflammatory cytokines. CONCLUSIONS: O&NS, airways inflammation, and impaired HDAC2 may be important mechanisms of virus-induced COPD exacerbations. Therapies targeting these mechanisms offer potential new treatments for COPD exacerbations.

A short-term mouse model that reproduces the immunopathological features of rhinovirus-induced exacerbation of COPD.

Viral exacerbations of chronic obstructive pulmonary disease (COPD), commonly caused by rhinovirus (RV) infections, are poorly controlled by current therapies. This is due to a lack of understanding of the underlying immunopathological mechanisms. Human studies have identified a number of key immune responses that are associated with RV-induced exacerbations including neutrophilic inflammation, expression of inflammatory cytokines and deficiencies in innate anti-viral interferon. Animal models of COPD exacerbation are required to determine the contribution of these responses to disease pathogenesis. We aimed to develop a short-term mouse model that reproduced the hallmark features of RV-induced exacerbation of COPD. Evaluation of complex protocols involving multiple dose elastase and lipopolysaccharide (LPS) administration combined with RV1B infection showed suppression rather than enhancement of inflammatory parameters compared with control mice infected with RV1B alone. Therefore, these approaches did not accurately model the enhanced inflammation associated with RV infection in patients with COPD compared with healthy subjects. In contrast, a single elastase treatment followed by RV infection led to heightened airway neutrophilic and lymphocytic inflammation, increased expression of tumour necrosis factor (TNF)-α, C-X-C motif chemokine 10 (CXCL10)/IP-10 (interferon γ-induced protein 10) and CCL5 [chemokine (C-C motif) ligand 5]/RANTES (regulated on activation, normal T-cell expressed and secreted), mucus hypersecretion and preliminary evidence for increased airway hyper-responsiveness compared with mice treated with elastase or RV infection alone. In summary, we have developed a new mouse model of RV-induced COPD exacerbation that mimics many of the inflammatory features of human disease. This model, in conjunction with human models of disease, will provide an essential tool for studying disease mechanisms and allow testing of novel therapies with potential to be translated into clinical practice.

IL-33-dependent type 2 inflammation during rhinovirus-induced asthma exacerbations in vivo.

RATIONALE: Rhinoviruses are the major cause of asthma exacerbations; however, its underlying mechanisms are poorly understood. We hypothesized that the epithelial cell-derived cytokine IL-33 plays a central role in exacerbation pathogenesis through augmentation of type 2 inflammation. OBJECTIVES: To assess whether rhinovirus induces a type 2 inflammatory response in asthma in vivo and to define a role for IL-33 in this pathway. METHODS: We used a human experimental model of rhinovirus infection and novel airway sampling techniques to measure IL-4, IL-5, IL-13, and IL-33 levels in the asthmatic and healthy airways during a rhinovirus infection. Additionally, we cultured human T cells and type 2 innate lymphoid cells (ILC2s) with the supernatants of rhinovirus-infected bronchial epithelial cells (BECs) to assess type 2 cytokine production in the presence or absence of IL-33 receptor blockade. MEASUREMENTS AND MAIN RESULTS: IL-4, IL-5, IL-13, and IL-33 are all induced by rhinovirus in the asthmatic airway in vivo and relate to exacerbation severity. Further, induction of IL-33 correlates with viral load and IL-5 and IL-13 levels. Rhinovirus infection of human primary BECs induced IL-33, and culture of human T cells and ILC2s with supernatants of rhinovirus-infected BECs strongly induced type 2 cytokines. This induction was entirely dependent on IL-33. CONCLUSIONS: IL-33 and type 2 cytokines are induced during a rhinovirus-induced asthma exacerbation in vivo. Virus-induced IL-33 and IL-33-responsive T cells and ILC2s are key mechanistic links between viral infection and exacerbation of asthma. IL-33 inhibition is a novel therapeutic approach for asthma exacerbations.

Defining critical roles for NF-κB p65 and type I interferon in innate immunity to rhinovirus.

The importance of NF-κB activation and deficient anti-viral interferon induction in the pathogenesis of rhinovirus-induced asthma exacerbations is poorly understood. We provide the first in vivo evidence in man and mouse that rhinovirus infection enhanced bronchial epithelial cell NF-κB p65 nuclear expression, NF-κB p65 DNA binding in lung tissue and NF-κB-regulated airway inflammation. In vitro inhibition of NF-κB reduced rhinovirus-induced pro-inflammatory cytokines but did not affect type I/III interferon induction. Rhinovirus-infected p65-deficient mice exhibited reduced neutrophilic inflammation, yet interferon induction, antiviral responses and virus loads were unaffected, indicating that NF-κB p65 is required for pro-inflammatory responses, but redundant in interferon induction by rhinoviruses in vivo. Conversely, IFNAR1(-/-) mice exhibited enhanced neutrophilic inflammation with impaired antiviral immunity and increased rhinovirus replication, demonstrating that interferon signalling was critical to antiviral immunity. We thus provide new mechanistic insights into rhinovirus infection and demonstrate the therapeutic potential of targeting NF-κB p65 (to suppress inflammation but preserve anti-viral immunity) and type I IFN signalling (to enhance deficient anti-viral immunity) to treat rhinovirus-induced exacerbations of airway diseases.