The overall goal of our research program is to develop better treatment strategies for the prevention of vision loss due to microbial keratitis, as well as increasing our understanding of ocular biology through host-pathogen interaction analysis. This specific study will elucidate a novel host-pathogen interaction important for bacterial infection of the ocular surface. We are focusing on a class of bacteria that frequently cause ocular infections and multidrug resistant hospital infections, the Enterobacteriaceae, that is understudied with respect to ocular infections. Importantly, we will be using recent clinical isolates derived from contact lens associated keratitis event rather than non-ocular laboratory strains that may not share ocular virulence factors. Using the member of the Enterobacteriaceae that most commonly causes keratitis as a model organism, Serratia marcescens, we have uncovered a novel host-pathogen interaction that we will define in this study. Namely, a step in bacteria-mediated ocular cell death is the formation of a distinct type of membrane bleb. Preliminary data indicates the mechanism underlying bleb induction by S. marcescens requires a bacterial type V secretion system, a cytolysin, and a conserved but unstudied stress regulator we are calling GumB. Taking advantage of our state of the art microscopy facility, molecular tools, tunable expression systems, and ocular infection models, we are poised to complete our research goals.
Our aims will: 1) address the hypothesis that a type V secretion system involving cytolysin proteins ShlB and ShlA is necessary and sufficient to induce membrane blebs in human ocular cells. This will introduce a completely new mechanism by which bacteria influence corneal cells; 2) determine the mechanism by which GumB regulates bleb formation and cytotoxicity to corneal epithelial cells.
This aim will uncover the role of GumB as a virulence factor regulator, which is a conserved bacterial protein found in many species associated with ocular host-pathogen interactions; 3) establish the role of GumB in ocular virulence using a rabbit contact lens keratitis model. This work will show that GumB is a novel master regulator of ocular virulence factors, and will identify those factors. These studies have the potential to discover an entirely new mechanism by which bacteria impact human cells and corneal disease. The long-term implication is that CL-associated keratitis is due, at least in part, to this host-pathogen interaction. The resolution of this mechanism could establish the foundation for more effective infection treatments, such as through chemical inhibition of the proteins studied here.

Public Health Relevance

Eye infections caused by bacteria are a common and costly vision-threatening problem in the United States and abroad. Our project will define how an understudied class of bacteria damages cells on the surface of the eye. The scientific mechanism uncovered by this study could establish the foundation for more effective treatments, which are especially important to find given the rise of antibiotic resistant bacteria in the clinic and community.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY027331-04
Application #
9910406
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Mckie, George Ann
Project Start
2017-04-01
Project End
2021-03-31
Budget Start
2020-04-01
Budget End
2021-03-31
Support Year
4
Fiscal Year
2020
Total Cost
Indirect Cost
Name
University of Pittsburgh
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15260
Brothers, Kimberly M; Kowalski, Regis P; Tian, Shenghe et al. (2018) Bacteria induce autophagy in a human ocular surface cell line. Exp Eye Res 168:12-18
Stella, Nicholas A; Brothers, Kimberly M; Callaghan, Jake D et al. (2018) An IgaA/UmoB Family Protein from Serratia marcescens Regulates Motility, Capsular Polysaccharide Biosynthesis, and Secondary Metabolite Production. Appl Environ Microbiol 84:
Zhou, Siwei; Hunt, Kristin M; Grewal, Arman S et al. (2018) Release of Moxifloxacin From Corneal Collagen Shields. Eye Contact Lens 44 Suppl 2:S143-S147
Romanowski, Eric G; Stella, Nicholas A; Yates, Kathleen A et al. (2018) In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution on Established Biofilms. Eye Contact Lens 44 Suppl 2:S187-S191
Antic, Irena; Brothers, Kimberly M; Stolzer, Maureen et al. (2017) Gene Acquisition by a Distinct Phyletic Group within Streptococcus pneumoniae Promotes Adhesion to the Ocular Epithelium. mSphere 2:
Ito, Ryota; Mustapha, Mustapha M; Tomich, Adam D et al. (2017) Widespread Fosfomycin Resistance in Gram-Negative Bacteria Attributable to the Chromosomal fosA Gene. MBio 8:
Melvin, Jeffrey A; Gaston, Jordan R; Phillips, Shawn N et al. (2017) Pseudomonas aeruginosa Contact-Dependent Growth Inhibition Plays Dual Role in Host-Pathogen Interactions. mSphere 2: