Reduced Antiviral Interferon Production in Poorly Controlled Asthma Is Associated With Neutrophilic Inflammation and High-Dose Inhaled Corticosteroids

BACKGROUND: Asthma is a heterogeneous chronic inflammatory disease in which host defense against respiratory viruses such as human rhinovirus (HRV) may be abnormal. This is a matter of some controversy, with some investigators reporting reduced type I interferon (IFN) synthesis and others suggesting that type I IFN synthesis is relatively normal in asthma. OBJECTIVE: The objective of this study was to examine the responsiveness of circulating mononuclear cells to HRV in a large cohort of participants with poorly controlled asthma and determine whether IFN-alpha and IFN-beta synthesis varies across different inflammatory phenotypes. METHODS: Eligible adults with asthma (n = 86) underwent clinical assessment, sputum induction, and blood sampling. Asthma inflammatory subtypes were defined by sputum cell count, and supernatant assessed for IL-1 beta. Peripheral blood mononuclear cells (PBMCs) were exposed to HRV serotype 1b, and IFN-alpha and IFN-beta release was measured by enzyme-linked immunosorbent assay. RESULTS: Participants (mean age, 59 years; atopy, 76%) had suboptimal asthma control (mean asthma control questionnaire 6, 1.7). In those with neutrophilic asthma (n = 12), HRV1b-stimulated PBMCs produced significantly less IFN-alpha than PBMCs from participants with eosinophilic (n = 35) and paucigranulocytic asthma (n = 35). Sputum neutrophil proportion and the dose of inhaled corticosteroids were independent predictors of reduced IFN-alpha production after HRV1b exposure. CONCLUSIONS: Antiviral type I IFN production is impaired in those with neutrophilic airway inflammation and in those prescribed high doses of inhaled corticosteroids. Our study is an important step toward identifying those with poorly controlled asthma who might respond best to inhaled IFN therapy during exacerbations.