# Bacterial Factors that Regulate Ocular Host-Pathogen Interactions and Microbial Keratitis

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2020 · $444,382

## Abstract

7. Project Summary / Abstract
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.

## Key facts

- **NIH application ID:** 9910406
- **Project number:** 5R01EY027331-04
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** ROBERT M SHANKS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $444,382
- **Award type:** 5
- **Project period:** 2017-04-01 → 2022-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9910406

## Citation

> US National Institutes of Health, RePORTER application 9910406, Bacterial Factors that Regulate Ocular Host-Pathogen Interactions and Microbial Keratitis (5R01EY027331-04). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9910406. Licensed CC0.

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