P. aeruginosa infections are a common cause of corneal disease associated with extended-wear contact lens use here in the US. One of the primary virulence factors P. aeruginosa uses to promote disease is its type III secretion system, a molecular syringe that allows the bacterium to directly inject effector proteins into targeted host cells. The role of type III secretion in corneal disease has not been studied extensively, but initial reports suggest that corneal disease depends on the complement of effectors being expressed by the infecting bacteria. "Cytotoxic" strains expressing the potent phospholipase ExoU rely extensively on type III secretion to promote disease, whereas ExoS-producing "invasive" strains, appear to not rely on type III secretion in order to elicit corneal disease. We have revisited the role of type III secretion in the pathogenesis of corneal disease elicited by ExoS+ "invasive" isolates of P. aeruginosa. Our preliminary data demonstrates that corneal disease relies critically on type III secretion and on the two effectors ExoS and ExoT, in particular. In addition, we provide evidence that the primary role of type III secretion in corneal disease is to stave off killing by infiltrating neutrophils. Accordingly, the focus of this proposal is to determine the role of the individual enzymatic activities of ExoS and ExoT in preventing clearance by neutrophils in vivo. We will correlate these findings with experiments aimed at examining the role of ExoS and ExoT in preventing phagocytic killing by isolated primary neutrophils. We will also examine the difference in pathogenesis between ExoU-expressing "cytotoxic" and ExoS- expressing "invasive" strains of P. aeruginosa in order to determine if any differences can be directly linked to the activities of these two effectors. Understanding the role of effector proteins in corneal disease is an important step towards formulating new strategies for preventing and treating P. aeruginosa infections of the eye.

Public Health Relevance

Pseudomonas aeruginosa is a common cause of eye infections, particularly in contact lens wearers. If left untreated these infections can result in rapid to loss of vision. The bacterium injects toxic proteins into host immune cells that normally engulf and kill the invading bacteria. Our research is aimed at understanding how these toxic proteins stave off killing by the host immune system, with the hope that a better understanding of their function will lead to the design of targeted therapies to combat or prevent these infections.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY022052-02
Application #
8404007
Study Section
Special Emphasis Panel (ZRG1-BDCN-H (02))
Program Officer
Mckie, George Ann
Project Start
2012-01-01
Project End
2014-12-31
Budget Start
2013-01-01
Budget End
2013-12-31
Support Year
2
Fiscal Year
2013
Total Cost
$372,875
Indirect Cost
$135,375
Name
Case Western Reserve University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Toska, Jonida; Sun, Yan; Carbonell, Dalina Alvarez et al. (2014) Diversity of virulence phenotypes among type III secretion negative Pseudomonas aeruginosa clinical isolates. PLoS One 9:e86829
Karthikeyan, Rajapandian SivaGanesa; Priya, Jeganathan Lakshmi; Leal Jr, Sixto M et al. (2013) Host response and bacterial virulence factor expression in Pseudomonas aeruginosa and Streptococcus pneumoniae corneal ulcers. PLoS One 8:e64867
Pearlman, Eric; Sun, Yan; Roy, Sanhita et al. (2013) Host defense at the ocular surface. Int Rev Immunol 32:4-18