Microbial keratitis is a common cause of vision loss. The cornea is exquisitely sensitive to inflammation- mediated damage and therefore has strong innate defenses. However, when the epithelial barrier function is breached, opportunistic bacterial and fungal pathogens can gain access to the epithelial cell layers and colonize in the cornea, leading to infection. During the initial grant period, flagellin, the ligand of Toll-like receptor 5 (TLR5), was used to fortify corneal innate immunity and render resistance to a broad spectrum of keratitis causing pathogens, including Pseudomonas aeruginosa, Candida albicans and Aspergillus fumigates. This highly inducible and robust innate mucosal protection can be attributed to flagellin-induced genomic reprogramming in the epithelium which, in turn, interacts with professional immune cells to control inflammation and to eradicate invading pathogens. The hypothesis in this application is that flagellin, through TLR5, stimulates protective corneal innate mucosal immunity that involves epithelial cells, infiltrated PMNs, and activated dendritic cells, collectively conferring robust resistance to microbial keratitis.
Three specific aims are proposed to test this hypothesis: 1) To determine how flagellin-induced reprogramming is regulated in corneal epithelial cells and in the cornea. This can be assessed by using the chromatin immunoprecipitation assay and histone deacetylase inhibitors for gene-specific chromatin modification and by using siRNA and knockout mice for delineating the role of activating transcription factor-3, a transcription factor induced by fg, in regulating the innate immune response in the cornea. 2) To determine how the epithelium participates in and coordinates flagellin-induced mucosal innate immune defense against microbial keratitis. The role of the epithelium and its interaction with dendritic cells in innate defense will be determined by using various transgenic and knockout mice, bone marrow reconstitution, and cell depletion. 3) To determine how flagellin induces protection against non-flagellated pathogens in the cornea. The therapeutic potential of flagellin and its mechanisms of action will be characterized by using mouse models of fungal keratitis (Candida and Aspergillus as pathogens and post-infection topical flagellin application) and double TLR knockout mice. The results of the proposed study should shed light on corneal innate immunity and its induction, and may lead to the development of new prophylactic/therapeutic modalities for preventing and treating microbial keratitis.

Public Health Relevance

This proposal is to determine the mechanisms underlying flagellin-induced protective corneal mucosal immunity and to explore its therapeutic potential to treat microbial keratitis, a common cause of vision loss. The knowledge gained will be critical for the long-term goal of developing mechanism-based, efficacious prophylactic/therapeutic modalities for preventing and treating infectious keratitis.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BDCN-H (02))
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Mckie, George Ann
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Wayne State University
Schools of Medicine
United States
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Dandekar, Aditya; Qiu, Yining; Kim, Hyunbae et al. (2016) Toll-like Receptor (TLR) Signaling Interacts with CREBH to Modulate High-density Lipoprotein (HDL) in Response to Bacterial Endotoxin. J Biol Chem 291:23149-23158
Gao, Nan; Yan, Chenxi; Lee, Patrick et al. (2016) Dendritic cell dysfunction and diabetic sensory neuropathy in the cornea. J Clin Invest 126:1998-2011
Gao, Nan; Lee, Patrick; Yu, Fu-Shin (2016) Intraepithelial dendritic cells and sensory nerves are structurally associated and functional interdependent in the cornea. Sci Rep 6:36414
Yan, Chenxi; Gao, Nan; Sun, Haijing et al. (2016) Targeting Imbalance between IL-1β and IL-1 Receptor Antagonist Ameliorates Delayed Epithelium Wound Healing in Diabetic Mouse Corneas. Am J Pathol 186:1466-80
Tolle, Leslie; Yu, Fu-shin; Kovach, Melissa A et al. (2015) Redundant and cooperative interactions between TLR5 and NLRC4 in protective lung mucosal immunity against Pseudomonas aeruginosa. J Innate Immun 7:177-86
Gao, Nan; Kumar, Ashok; Yu, Fu-Shin X (2015) Matrix Metalloproteinase-13 as a Target for Suppressing Corneal Ulceration Caused by Pseudomonas aeruginosa Infection. J Infect Dis 212:116-27
Sun, Haijing; Mi, Xiaofan; Gao, Nan et al. (2015) Hyperglycemia-suppressed expression of Serpine1 contributes to delayed epithelial wound healing in diabetic mouse corneas. Invest Ophthalmol Vis Sci 56:3383-92
Liu, Xiaowei; Gao, Nan; Dong, Chen et al. (2014) Flagellin-induced expression of CXCL10 mediates direct fungal killing and recruitment of NK cells to the cornea in response to Candida albicans infection. Eur J Immunol 44:2667-79
Bettahi, Ilham; Sun, Haijing; Gao, Nan et al. (2014) Genome-wide transcriptional analysis of differentially expressed genes in diabetic, healing corneal epithelial cells: hyperglycemia-suppressed TGFβ3 expression contributes to the delay of epithelial wound healing in diabetic corneas. Diabetes 63:715-27
Pandey, Rajeev K; Yu, Fu-Shin; Kumar, Ashok (2013) Targeting toll-like receptor signaling as a novel approach to prevent ocular infectious diseases. Indian J Med Res 138:609-19

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