Herpes stromal keratitis (HSK) is a chronic inflammatory condition that develops in response to a recurrent corneal infection with herpes simplex virus-1 (HSV-1). HSK is the leading cause of infection-induced corneal blindness in the United States. Clinical manifestation of HSK involves the development of opacity and neovascularization into the avascular cornea. Newly formed leaky blood vessels in the corneal stroma obscure the visual axis, traffic the leukocytes (mostly neutrophils) into the inflamed cornea, and cause the corneal edema. The current mainstay of HSK treatment requires the long-term use of oral antiviral drugs and the topical application of steroids. The prolonged use of topical steroids causes a predisposition to herpetic reactivation, cataract development, and increased intraocular pressure (IOP), which may cause the development of glaucoma. A better understanding of cellular and molecular events involved in the pathogenesis of HSK could provide novel therapeutic targets to reduce the severity of HSK. The focus of this application is to understand the mechanisms by which Insulin-like growth factor binding protein-3 (IGFBP-3) regulates the pathogenesis of HSK. IGFBP-3 exerts its effect through insulin-like growth factor (IGF)-independent and-dependent mechanisms. In an IGF-independent manner, IGFBP-3 is known to induce cellular senescence. The cellular senescence is reported to inhibit viral replication. The IGF-dependent activity of IGFBP-3 involves sequestration of IGF-1 and IGF-2 molecules and limiting their bioavailability to IGF-1R, and thereby regulates IGF-1R signaling. Our preliminary results showed an elevated expression of IGFBP-3 in HSV-1 infected corneas of B6 mice, whereas a significantly reduced amount of IGFBP-3 protein was detected in the circulation of infected B6 mice when compared to uninfected B6 mice. The infected corneas of IGFBP-3 knockout (IGFBP-3 KO) mice showed an increased viral load. Besides, increased phosphorylation of IGF-1R, the first step in IGF-1R signaling, was determined in leukocytes infiltrating the HSK developing corneas of IGFBP-3 KO than B6 mice. A significant increase in hemangiogenesis and opacity was measured in infected corneas of IGFBP-3 KO than B6 mice. Together, these results led us to hypothesize that IGFBP-3 enhances viral clearance, reduces angiogenesis, and decreases the survival and effector function of myeloid cells in HSK developing corneas. Therefore, enhancing the IGFBP-3 protein level in HSV-1 infected cornea should alleviate the severity of HSK. Three aims are proposed to test our hypothesis. Aim I will test the hypothesis that hypoxia enhances IGFBP-3 expression in corneal epithelial cells...