Defining the Role of the Plasminogen Activator Protease in the Early Events that Establish Primary Pneumonic Plague

Project Summary Pneumonic plague is the deadliest form of disease caused by Yersinia pestis. Early after infection, Y. pestis subverts host innate immune mechanisms in the lung and replicates to high numbers before the onset of lethal host inflammatory responses. As a result, pneumonic plague is difficult to treat once symptoms are recognized. This proposal introduces the Yersinia Plasminogen activator protease (Pla) as an important mediator of early host/pathogen interactions in the lung. Pla is well-established virulence factor known to be essential to the pathogenesis of pneumonic plague via an unknown function. The work proposed here examines the dual role of Pla, as both an adhesin and a protease, during pulmonary infection. The objective of this work is to define the function of the critical Yersinia virulence factor Pla in the early events of pneumonic plague to understand how Y. pestis resists clearance by host inflammatory responses to establish an initial replicative phase in the lungs. The strategy for this proposal is outlined below: Specific Aim 1. Define the role of Pla-mediated T3S during pneumonic plague. The adhesin function of Pla facilitates targeting of alveolar macrophages for type 3 secretion (T3S) early during pneumonic plague. Aim 1 will generate and test mutants of Pla to understand how Pla mediates adherence, and characterize the importance of Pla-mediated adherence and T3S in vivo. Further, the impact of Pla-mediated T3S on host cell innate immune responses to T3S will be evaluated during infection to understand how Y. pestis limits host responsiveness early during infection. Specific Aim 2. Characterize novel proteolytic functions of Pla during pneumonic plague. Preliminary data has identified two novel functions of Pla that may contribute to pathogenesis. A proteomics approach will be used to identify and characterize Pla proteolytic activity early during primary pneumonic plague. Specific Aim 3. Identify key host cell types and dynamics responsible for establishing an early pre- inflammatory disease phase during pneumonic plague. Preliminary data indicates that deletion of Pla disrupts the ability of Y. pestis to limit early innate immune responses in the lung. In Aim 3 we will evaluate host cell dynamics and innate immune responses in the lung in the presence and absence of Pla to understand how Y. pestis is able to subvert initial inflammatory responses and establish infection in the lung.