Cystic Fibrosis (CF) is a genetic disease that affects multiple organs, although lung disease, associated with host and bacterial-mediated lung tissue damage, accounts for the majority of morbidity and mortality. In people with CF, airway mucus becomes thick and dehydrated, facilitating chronic infection by Pseudomonas aeruginosa. During infection, P. aeruginosa produces small signalling molecules to coordinate formation of antimicrobial resistant biofilms and production of host-damaging virulence factors, in a process termed quorum sensing. Therefore, inhibition of bacterial quorum sensing should reduce P. aeruginosa biofilm formation and pathogenicity ultimately assisting in clearance of infection. Thus, the P. aeruginosa quorum sensing system is a potential therapeutic target.
Paraoxonase-2 (PON2) is a human enzyme able to inactivate the P. aeruginosa signalling molecule, however, PON2 is expressed intracellularly and thus has little opportunity to inactivate the extracellular bacterial signalling molecules. To overcome this problem, our laboratory has produced a recombinant form of human PON2 (rhPON2) that can be administered extracellularly. We have demonstrated that rhPON2 treatment of P. aeruginosa inactivates the signal molecule and reduces bacterial motility, biofilm formation and virulence factor production. Furthermore, P. aeruginosa proteome analysis revealed that expression of proteins necessary for quorum sensing, phenazine biosynthesis and cAMP resistance are reduced in response to rhPON2 treatment, compared to untreated controls. In addition, airway epithelial cells treated with rhPON2 during P. aeruginosa infection had a significant reduction in host inflammatory cytokines and reduced expression of key P. aeruginosa quorum sensing regulators. Together these results demonstrate that rhPON2 protects host cells against P. aeruginosa induced inflammation and attenuates bacterial quorum sensing and virulence, supporting the use of rhPON2 as an anti-Pseudomonal therapy.