A NOVEL HUMAN LUNG INFECTION PLATFORM TO DEFINE STAPHYLOCOCCUS AUREUS VIRULENCE DETERMINANTS

Project SummaryStaphylococcus aureus is a Gram-positive, opportunistic pathogen that causes severe nosocomial andcommunity-acquired pneumonia. In the lung, S. aureus encounters epithelial cells and macrophages, and recentreports suggest these cells serve as a replication niche. However, conflicting information exists regarding theability of S. aureus to survive and replicate in host cells, specifically when comparing host species and bacterialclonal lineages of differing degrees of virulence. Numerous studies have used animal models of infection andhuman cell lines to study bacterial proliferation and the pro-inflammatory response to S. aureus; however, thesemodels do not entirely mimic the human condition due, in part, to critical virulence factors with species specificity.The current proposal will establish a novel infection system that accurately mimics the interactionbetween S. aureus and human lungs. Human lung tissue and isolated pulmonary cells will be exposed toclinically relevant S. aureus isolates to investigate the pathogen's cellular replication niche and the host responseto infection. Aim 1 will characterize the target niche of S. aureus in the human lung and assess bacterialreplication in distinct cell types. Aim 2 will define the role of two S. aureus cytotoxins in triggering a pro-inflammatory innate immune response and disrupting tissue integrity and cell survival. This Aim will use ?-toxinand Panton-Valentine Leukocidin as model virulence factors to establish our ex vivo infection system as adisease-relevant method for defining virulence factor activity. Collectively, the proposed studies willestablish a human disease relevant infection platform to study pulmonary S. aureus infection andvirulence factor activity.