The Role of IL-15 Deficiency in the Pathogenesis of Virus-Induced Asthma Exacerbations

Rhinovirus infections are the major cause of asthma exacerbations. We hypothesised that IL-15, a cytokine implicated in innate and acquired antiviral immunity, may be deficient in asthma and important in the pathogenesis of asthma exacerbations. We investigated regulation of IL-15 induction by rhinovirus in human macrophages in vitro, IL-15 levels in bronchoalveolar lavage (BAL) fluid and IL-15 induction by rhinovirus in BAL macrophages from asthmatic and control subjects, and related these to outcomes of infection in vivo. Rhinovirus induced IL-15 in macrophages was replication-, NF-κB- and α/β interferon-dependent. BAL macrophage IL-15 induction by rhinovirus was impaired in asthmatics and inversely related to lower respiratory symptom severity during experimental rhinovirus infection. IL-15 levels in BAL fluid were also decreased in asthmatics and inversely related with airway hyperresponsiveness and with virus load during in vivo rhinovirus infection. Deficient IL-15 production in asthma may be important in the pathogenesis of asthma exacerbations

Cilomilast Modulates Rhinovirus-Induced Airway Epithelial ICAM-1 Expression and IL-6, CXCL8 and CCL5 Production

Background: Cilomilast, a phosphodiesterase-4 (PDE4) selective inhibitor, has anti-inflammatory effects in vitro and in vivo and reduces COPD exacerbations. We tested the hypothesis that cilomilast inhibits virus-induced airway epithelial intercellular adhesion molecule-1 (ICAM-1) expression and inflammatory cytokine/chemoattractants, IL-6, CXCL8, and CCL5 production in vitro. Methods: BEAS-2B bronchial epithelial cells were incubated with 0.5–2 MOI (multiplicity of infection–infectious units/cell) of rhinovirus 16 (RV16). Then, 0.1–10 μM cilomilast or 10 nM dexamethasone, as inhibition control, were added pre- or post-1 h RV16 infection. Supernatant and cells were sampled at 8, 24, 48, and 72 h after infection. Cell surface ICAM-1 expression was detected by immunogold labelling and visualised by high-resolution scanning electron microscopy (HR-SEM), while IL-6, CXCL8, and CCL5 protein release and mRNA expression were measured using an ELISA and RT-PCR. Results: Cilomilast significantly decreased RV16-induced ICAM-1 expression to approximately 45% (p < 0.01). CXCL8 protein/mRNA production was reduced by about 41% (p < 0.05), whereas IL-6 protein/mRNA production was increased to between 41–81% (p < 0.001). There was a trend to reduction by cilomilast of RV16-induced CCL5. Conclusions: Cilomilast has differential effects on RV16-induced ICAM-1 and interleukins, inhibiting virus-induced ICAM-1 expression and CXCL8 while increasing IL-6 production. These in vitro effects may help to explain the beneficial actions of this PDE4 inhibitor in vivo

Bronchial mucosal IFN-α/β and pattern recognition receptor expression in patients with experimental rhinovirus-induced asthma exacerbations

Background: The innate immune system senses viral infection through pattern recognition receptors (PRRs), leading to type I interferon production. The role of type I interferon and PPRs in rhinovirus-induced asthma exacerbations in vivo are uncertain. Objectives: We sought to compare bronchial mucosal type I interferon and PRR expression at baseline and after rhinovirus infection in atopic asthmatic patients and control subjects. Methods: Immunohistochemistry was used to detect expression of IFN-α, IFN-β, and the PRRs: Toll-like receptor 3, melanoma differentiation–associated gene 5, and retinoic acid–inducible protein I in bronchial biopsy specimens from 10 atopic asthmatic patients and 15 nonasthmatic nonatopic control subjects at baseline and on day 4 and 6 weeks after rhinovirus infection. Results: We observed IFN-α/β deficiency in the bronchial epithelium at 3 time points in asthmatic patients in vivo. Lower epithelial IFN-α/β expression was related to greater viral load, worse airway symptoms, airway hyperresponsiveness, and reductions in lung function during rhinovirus infection. We found lower frequencies of bronchial subepithelial monocytes/macrophages expressing IFN-α/β in asthmatic patients during infection. Interferon deficiency at baseline was not accompanied by deficient PRR expression in asthmatic patients. Both epithelial and subepithelial PRR expression were induced during rhinovirus infection. Rhinovirus infection–increased numbers of subepithelial interferon/PRR-expressing inflammatory cells were related to greater viral load, airway hyperresponsiveness, and reductions in lung function. Conclusions: Bronchial epithelial IFN-α/β expression and numbers of subepithelial IFN-α/β–expressing monocytes/macrophages during infection were both deficient in asthmatic patients. Lower epithelial IFN-α/β expression was associated with adverse clinical outcomes after rhinovirus infection in vivo. Increases in numbers of subepithelial cells expressing interferon/PRRs during infection were also related to greater viral load/illness severity

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

Lymphocyte subsets in experimental rhinovirus infection in chronic obstructive pulmonary disease

SummaryBackgroundCOPD is associated with increased numbers of T cells in the lungs, particularly CD8+ T cells. The mechanisms of increased T cells are unknown but may be related to repeated virus infections in COPD patients. We analysed lymphocyte subsets in blood and bronchoalveolar lavage in smokers and COPD subjects during experimental rhinovirus infections.MethodsLymphocytes were isolated from blood and bronchoalveolar lavage from COPD subjects and non-obstructed smokers prior to, and following experimental rhinovirus infection. Lymphocyte surface markers and intracellular cytokines were analysed using flow cytometry.ResultsFollowing rhinovirus infection CD4+ and CD8+ T cell numbers in the COPD subjects were significantly reduced in blood and CD3+ and CD8+ T cells increased in bronchoalveolar lavage compared to baseline. T cells did not increase in BAL in the control subjects. CD3+ T cells correlated with virus load.ConclusionsFollowing rhinovirus infection T cells move from the circulation to the lung. Repeated virus infections may contribute to T cell accumulation in COPD patients