IL-17 Plays a Role in Respiratory Syncytial Virus-induced Lung Inflammation and Emphysema in Elastase and LPS-injured Mice.

Respiratory syncytial virus (RSV) is associated with enhanced progression of chronic obstructive pulmonary disease (COPD) and COPD exacerbations. However, little is known about the role of IL-17 in RSV-induced lung injury. We first investigated the role of RSV infection in enhancing mucous cell hyperplasia (MCH) and airspace enlargement in the lungs of mice injured with elastase and LPS (E/LPS). Mice injured with E/LPS had an enhanced and prolonged neutrophilic response to RSV that was associated with decreased levels of type I IFN and increased levels of IL-17, IL-23, CXCL-1, granulocyte colony stimulating factor (GCSF), CXCL-5, and matrix metalloproteinase (MMP)-9. In addition, extent of MCH and mean weighted alveolar space were increased significantly in the lungs of E/LPS-injured mice infected with RSV compared with E/LPS-only or RSV-only controls. Interestingly, immunodepletion of IL-17 before viral infection diminished the RSV-driven MCH and airspace enlargement in the E/LPS-injured animals, suggesting that IL-17 may be a therapeutic target for MCH and airspace enlargement when enhanced by RSV infection.