Abstract
Purpose: :
To determine the role of specific components of the type III-secretion system (T3SS) and the host response during Pseudomonas aeruginosa keratitis.
Methods: :
Corneas of C57BL/6, MyD88-/-, TLR4/5-/- and Mafia mice were abraded by three parallel scratches, and infected with P. aeruginosa parent strain PAO1, which expresses ExoS, T and Y, but not ExoU, or with T3SS mutants. Corneal opacification, neutrophil infiltration to the stroma and bacterial growth were examined after 24, 48 and 72h.
Results: :
Corneas of PAO1 and ExoY mutants developed severe keratitis with increasing CFU. In contrast, mice infected with mutants in either the entire T3SS system, the translocator proteins PopB and PopD, ExoS or ExoT developed significantly less clinical disease, and bacteria were killed over time, although αExoS,T double mutants had a more pronounced phenotype that single mutants. All T3SS mutants were able to replicate in corneas of MyD88-/-, TLR4/5-/- and macrophage depleted Mafia mouse corneas, which have impaired neutrophil infiltration.
Conclusions: :
These findings demonstrate an essential role for the P. aeruginosa T3SS, notably ExoS and ExoT, and indicate that infiltrating neutrophils are the targets of ExoS and ExoT.
Keywords: inflammation • cornea: basic science