Virus-induced exacerbations of asthma are a major cause of emergency room visits and hospitalizations, and contribute disproportionately to the economic burden of the disease. Rhinovirus (RV) is a dominant instigator of exacerbations, and other respiratory viruses, including Respiratory Syncytial Virus (RSV), for which no vaccine is available, also contribute significantly to the incidence of exacerbations. In this Project we will focus upon inhibitors of RV and RSV infection of nasal and bronchial epithelial cells cultured from adult control and asthmatic subjects. Two endogenous molecules of the pulmonary surfactant system, surfactant protein A (SP-A) and palmitoyl-oleoyl-phosphatidylglycerol (POPG), act as potent antagonists of RV and RSV infection. In this proposal we will examine the protective activity of these surfactant constituents in preventing viral infections of differentiated nasal and bronchial epithelial cells, derived from control and asthmatic subjects. Preliminary data demonstrate that SP-A binds to RV with high affinity and inhibits infection of epithelial cells. We will elucidate the mechanism of SP-A inhibition of RV infection. The SP-A binding to RV is isoform dependent and we will investigate whether the genetic makeup of the asthmatics in our cohorts is skewed towards SP-A variants that exhibit weak binding to RV. POPG inhibits RV and also RSV infection of epithelial cells, and we will determine the mechanism of anti-viral action of this lipid. The proposed experiments will also reveal if epithelial cells from asthmatic are either sensitive or inherently resistant to the protective actions of the surfactant constituents. Our studies with SP-A and POPG will be integrated with other projects in the overall proposal. All of the subject derived epithelial cells will be provided by the Clinical Core. In collaborative studies with Project 1, we will determine the action of SP-A isoforms as inhibitors of IL-13 signaling. We will also investigate the effectiveness of SP-A isoforms and POPG as antagonists of RV infections and inflammatory sequelae in the presence of high levels of IL-13 that mimic the asthmatic environment in vivo. In collaborative studies with Project 2 we will determine if SP-A and POPG can suppress the elevated inflammatory phenotype of Tollip deficient epithelial cells. The final goal of this project is to critically test the in vivo activity of SP-A and POPG using a mouse model of asthma exacerbation that combines priming with house dust mite allergen followed by challenge with RV, or RSV. The in vivo experiments will provide important new information about the potential application of SP-A and POPG for the prevention and treatment of virus -elicited exacerbations of asthma in humans.
