Pseudomonas aeruginosa–induced hemorrhagic pneumonia: deciphering novel virulence strategies – HemoPseudo

P. aeruginosa is a key nosocomial pathogen that is naturally resistant to a wide range of antibiotics. The fact that it requires the Type III secretion system for establishment of virulence led the scientific community to study this macromolecular machinery in detail. However, it is now evident that P. aeruginosa has developed a NOVEL VIRULENCE STRATEGY that circumvents the T3SS and cause aggressive, rapid cell death. The work performed by our group, in collaboration with medical physicians at the Intensive Care Unit at the Grenoble University Hospital, reveals that a novel secreted protein, Exolysin, plays a key role in the molecular mechanisms involved in this process, and is a crucial virulence factor for the pathogenesis of clinically relevant P. aeruginosa isolates of the PA7/CLJ lineage, capable of provoking hemorrhagic pneumonia. In this project, we will undertake the study of these P. aeruginosa clinical isolates from microbiological, biochemical, cellular and structural viewpoints, with the objective of delineating details of this new strategy in bacterial pathogenesis. Notably, the delineation of the toxin secretion process, its action on immune/epithelial/endothelial cells, the mechanisms of Exolysin regulation, and global host response to this type of pathogenesis process will be essential for the development of novel anti-virulence strategies. The results that will be generated through this project will thus have great impact at two levels. First, basic information about a new virulence mechanism will be generated for the vast scientific community. Moreover, this data will impact the work of physicians and hospital staff in charge of controlling bacterial infection,
notably in Intensive Care Units, recognizing a variant of P. aruginosa different in virulence properties from those commonly encountered in nosocomial settings. Because of the dramatic impact of Exolysin on P. aeruginosa pathogenicity, targeting this protein in future antibacterial development effort could be of high clinical interest. Thus, our research project is based on integrated, multidisciplinary approaches and aims to:
• Decipher the structure-functional relationship of Exolysin and its regulation
• Identify cellular targets of the toxin and characterize host responses using adapted cellularmodels
• Study global patho-adaptation of the CLJ strains using functional genomics
The project is divided into four complementary Tasks that involve a tight collaboration between the two partners who have been already engaged in several successful collaborations. The partnership, already established, with Steve Lory’s laboratory at Harvard Medical School, Boston, MA, USA will be continued for all aspects of functional genomics.