Rhinoviruses are the major cause of asthma exacerbations, and asthmatics have increased susceptibility to rhinovirus and risk of invasive bacterial infections. Here we show deficient induction of interferon-lambdas by rhinovirus in asthmatic primary bronchial epithelial cells and alveolar macrophages, which was highly correlated with severity of rhinovirus-induced asthma exacerbation and virus load in experimentally infected human volunteers. Induction by lipopolysaccharide in asthmatic macrophages was also deficient and correlated with exacerbation severity. These results identify previously unknown mechanisms of susceptibility to infection in asthma and suggest new approaches to prevention and/or treatment of asthma exacerbations.

Acute exacerbations are the major cause of asthma morbidity, mortality, and health-care costs and are difficult to treat and prevent. The majority of asthma exacerbations are associated with rhinovirus (RV) infection, but evidence supporting a causal relationship is weak and mechanisms are poorly understood. We hypothesized that in asthmatic, but not normal, subjects RV infection would induce clinical, physiologic, and pathologic lower airway responses typical of an asthma exacerbation and that these changes would be related to virus replication and impaired T helper 1 (Th1)/IL-10 or augmented Th2 immune responses. We investigated physiologic, virologic, and immunopathologic responses to experimental RV infection in blood, induced sputum, and bronchial lavage in 10 asthmatic and 15 normal volunteers. RV infection induced significantly greater lower respiratory symptoms and lung function impairment and increases in bronchial hyperreactivity and eosinophilic lower airway inflammation in asthmatic compared with normal subjects. In asthmatic, but not normal, subjects virus load was significantly related to lower respiratory symptoms, bronchial hyperreactivity, and reductions in blood total and CD8 ؉ lymphocytes; lung function impairment was significantly related to neutrophilic and eosinophilic lower airway inflammation. The same virologic and clinical outcomes were strongly related to deficient IFN-␥ and IL-10 responses and to augmented IL-4, IL-5, and IL-13 responses. This study demonstrates increased RV-induced clinical illness severity in asthmatic compared with normal subjects, provides evidence of strong relationships between virus load, lower airway virus-induced inflammation and asthma exacerbation severity, and indicates augmented Th2 or impaired Th1 or IL-10 immunity are likely important mechanisms.exacerbation ͉ respiratory viruses ͉ immunology ͉ human experimental virus infection A cute exacerbations are the major cause of asthma morbidity, mortality (1), and health-care costs (2). Inhaled steroids are associated with reduced risk of exacerbation (3); however, optimal therapy in adults reduces exacerbation frequency by only Ϸ40-50% (4, 5). In school-age children inhaled steroids were ineffective at reducing exacerbation frequency, duration, or severity (6), and in preschool children oral steroids are also reported ineffective (7). Current therapy is therefore of limited efficacy and new more effective therapies are urgently required. To identify targets for development of new treatments, better understanding of mechanisms of virus-induced asthma exacerbations is required.Virus infections are associated with 80-85% of pediatric (8, 9) and Ϸ75% of adult (10, 11) asthma exacerbations, and rhinoviruses (RVs) account for two-thirds of virus detections. Asthmatic individuals are more susceptible to naturally occurring RV infection than normal individuals in that lower respiratory tract symptoms and changes in peak expiratory flow (PEF) are more severe and of longer duration (12). We recently found increased RV...

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 rhinovirusinfected bronchial epithelial cells (BECs) to assess type 2 cytokine production in the presence or absence of IL-33 receptor blockade.

Rationale: Respiratory virus infections are associated with chronic obstructive pulmonary disease (COPD) exacerbations, but a causative relationship has not been proven. Studies of naturally occurring exacerbations are difficult and the mechanisms linking virus infection to exacerbations are poorly understood. We hypothesized that experimental rhinovirus infection in subjects with COPD would reproduce the features of naturally occurring COPD exacerbations and is a valid model of COPD exacerbations. Objectives: To evaluate experimental rhinovirus infection as a model of COPD exacerbation and to investigate the mechanisms of virusinduced exacerbations. Methods: We used experimental rhinovirus infection in 13 subjects with COPD and 13 nonobstructed control subjects to investigate clinical, physiologic, pathologic, and antiviral responses and relationships between virus load and these outcomes. Measurements and Main Results: Clinical data; inflammatory mediators in blood, sputum, and bronchoalveolar lavage; and viral load in nasal lavage, sputum, and bronchoalveolar lavage were measured at baseline and after infection with rhinovirus 16. After rhinovirus infection subjects with COPD developed lower respiratory symptoms, airflow obstruction, and systemic and airway inflammation that were greater and more prolonged compared with the control group. Neutrophil markers in sputum related to clinical outcomes and virus load correlated with inflammatory markers. Virus load was higher and IFN production by bronchoalveolar lavage cells was impaired in the subjects with COPD. Conclusions: We have developed a new model of COPD exacerbation that strongly supports a causal relationship between rhinovirus infection and COPD exacerbations. Impaired IFN production and neutrophilic inflammation may be important mechanisms in virusinduced COPD exacerbations.

Rhinovirus infections are frequently followed by secondary bacterial infections in COPD and cleavage of the antimicrobial peptides SLPI and elafin by virus-induced neutrophil elastase may precipitate these secondary bacterial infections. Therapy targeting neutrophil elastase or enhancing innate immunity may be useful novel therapies for prevention of secondary bacterial infections in virus-induced COPD exacerbations.

Vitamin D, in addition to its classical functions in bone homeostasis, has a modulatory and regulatory role in multiple processes, including host defense, inflammation, immunity, and epithelial repair. Patients with respiratory disease are frequently deficient in vitamin D, implying that supplementation might provide significant benefit to these patients. Respiratory viral infections are common and are the main trigger of acute exacerbations and hospitalization in children and adults with asthma and other airways diseases. Respiratory monocytes/macrophages and epithelial cells constitutively express the vitamin D receptor. Vitamin D, acting through this receptor, may be important in protection against respiratory infections. Whether the in vitro findings can be translated into a substantial in vivo benefit still remains uncertain. Here we review the in vitro data on the role of vitamin D in antiviral innate immunity, the data concerning the deficient levels of vitamin D in lung diseases, and the in vivo role of supplementation as protection against respiratory viral infections in healthy individuals and in patients with chronic respiratory diseases. Finally, we suggest ways of improving the effectiveness of vitamin D as an adjuvant in the prevention and treatment of acute respiratory infections.

Respiratory virus infections are major triggers of acute exacerbations of asthma in both adults and children, implicated in around 80% of paediatric (1) and 75% of adult (2) asthma attacks. They are therefore major causes of asthma morbidity and mortality (3). Of viruses detected in asthma exacerbations, two thirds are rhinoviruses (1). Influenza viruses are also implicated in asthma exacerbations during annual influenza epidemics (2,4,5).Current therapy of asthma exacerbations is of limited efficacy (6-8), new approaches are therefore required.Background: Respiratory viruses, predominantly rhinoviruses are the major cause of asthma exacerbations. Impaired production of interferon-b in rhinovirus infected bronchial epithelial cells (BECs) and of the newly discovered interferon-ks in both BECs and bronchoalveolar lavage cells, is implicated in asthma exacerbation pathogenesis. Thus replacement of deficient interferon is a candidate new therapy for asthma exacerbations. Rhinoviruses and other respiratory viruses infect both BECs and macrophages, but their relative capacities for a-, b-and k-interferon production are unknown. Methods: To provide guidance regarding which interferon type is the best candidate for development for treatment/prevention of asthma exacerbations we investigated respiratory virus induction of a-, b-and k-interferons in BECs and peripheral blood mononuclear cells (PBMCs) by reverse transferase-polymerase chain reaction and enzyme-linked immunosorbent assay. Results: Rhinovirus infection of BEAS-2B BECs induced interferon-a mRNA expression transiently at 8 h and interferon-b later at 24 h while induction of interferon-k was strongly induced at both time points. At 24 h, interferon-a protein was not detected, interferon-b was weakly induced while interferon-k was strongly induced. Similar patterns of mRNA induction were observed in primary BECs, in response to both rhinovirus and influenza A virus infection, though protein levels were below assay detection limits. In PBMCs interferon-a, interferon-b and interferon-k mRNAs were all strongly induced by rhinovirus at both 8 and 24 h and proteins were induced: interferon-a>-b>-k. Thus respiratory viruses induced expression of a-, b-and k-interferons in BECs and PBMCs. In PBMCs interferon-a>-b>-k while in BECs, interferon-k>-b>-a. Conclusions: We conclude that interferon-ks are likely the principal interferons produced during innate responses to respiratory viruses in BECs and interferonas in PBMCs, while interferon-b is produced by both cell types.

Increased Th2 cytokine production in asthma is widely accepted, but excess production by asthmatic human airway CD4(+) T cells has not been demonstrated, nor has a relationship with disease severity. The importance of airway CD8(+) T cell type 1 and type 2 cytokine production in asthma is unknown. We investigated frequencies of IFN-gamma, interleukin (IL)-4 and IL-5 producing CD4(+) and CD8(+) blood and sputum T cells from normal subjects and subjects with asthma and compared between cell subsets, subject groups, and body compartments with and without in vitro stimulation and investigated relationships between cytokine production and asthma severity. Production of IL-4, IL-5, and IFN-gamma by unstimulated sputum CD4(+) and CD8(+) T cells was increased in subjects with asthma and related to disease severity, more for CD8(+) than for CD4(+) T cells. Frequencies of sputum CD8(+) T cells producing type 1 and type 2 cytokines were similar to those of CD4(+) T cells. In vitro stimulation polarized peripheral blood cytokine production toward IFN-gamma production, significantly more in subjects with asthma than in normal subjects. These data demonstrate increased type 1 and 2 cytokine production in CD4(+) and CD8(+) T cells in sputum and relate production to disease severity. Findings in blood did not reflect those in airways.