Studying the surface-tethered AaaA as a virulence factor and anti-P. aeruginosa drug target

P. aeruginosa is a leading cause of bacterial wound infections, and is associated with a disproportionally high level of mortality in burn patients especially. Because of its wide arsenal of virulence factors and biofilm formation ability, infections with P. aeruginosa are often chronic and extremely difficult to treat. This study uses an ex-vivo skin model to study the role of the virulence factor AaaA (PA0328) in chronic wound infections. AaaA, or the Arginine-specific aminopeptidase of Pseudomonas aeruginosa A, is a surface-tethered autotransporter which cleaves N-terminal arginine from peptides. In the oxygen and nutrient-limited environments of chronic wounds, this free arginine could serve as a nutrient source for P. aeruginosa via alternative metabolic pathways. Changes in local arginine concentrations may also alter host iNOS and Arginase immune responses which influence inflammation and wound healing, in order to favour a chronic infection. Being surface-tethered and immunogenic, AaaA is also of interest as a potential antimicrobial drug or vaccine target. This study aims to probe the role of AaaA on both pathogen survival and host response in the wound context, using a combination of in situ transcriptional reporters, immunofluorescence and laser-scanning microscopy, and RT-qPCR to localise and quantify P. aeruginosa survival and aaaA expression, as well as resident immune cell invasion, and expression of immune factor genes, in wounds over time. Here, we present preliminary data examining AaaA expression and function in P. aeruginosa biofilm cultures and ex-vivo skin wound infections, as well as the results of preliminary inhibitor screens.