Corneal Lymphatics & Adaptive Immunity

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Neovascularization in the normally avascular cornea can lead to a compromised visual axis. Within the term "neovascularization" is a blood component referred to as hemangiogenesis and a lymphatic component referred to as lymphangiogenesis. Relative to herpes simplex virus type 1 (HSV-1) infection, only hemangiogenesis has been investigated. Recently, we have initiated a study on lymphangiogenesis following corneal infection with HSV-1 and discovered this process precedes hemangiogenesis. More importantly, we have discovered the genesis of lymphatic vessels in the cornea proper in response to HSV-1 infection operates thru a unique pathway distinct from what has been described following corneal transplantation. Specifically, we have found a robust vascular endothelial growth factor (VEGF) A response by corneal epithelium infected with HSV-1 elicits lymphangiogenesis thru a VEGF receptor 2 (VEGFR2)-mediated pathway. This process is independent of VEGF C, VEGF receptor 3, or monocytes/macrophages. We have also found the newly created lymphatic vessels are capable of transporting soluble antigen to the draining lymph node independent of hemangiogenesis. However, what remains unknown is the contribution of the newly created lymphatic conduit to the host immune response within the draining lymph node as well as other inflammatory mediators that contribute to corneal lymphangiogenesis. We hypothesize lymphatic vessel development driven principally by VEGF A and contributing pro-inflammatory molecules generated locally in response to infection are critical for the induction of the adaptive immune response found in the draining lymph node reflected by the severity in the development of herpetic stromal keratitis of HSV-1 infected mice. To address this hypothesis, two specific aims are proposed: Specific aim 1 will address the impact of viral replication and pro- inflammatory cytokine expression on corneal lymphangiogenesis following HSV-1 infection. In addition, trafficking of leukocyte subpopulations and antigen will be monitored as well. Specific aim 2 will address the significance of lymphangiogenesis relative to the genesis of the adaptive immune response in the draining lymph node and development of stromal keratitis following HSV-1 infection. It will further address the role of virus-induced VEGF A production on the production of CD4+ and CD8+ T effector cells that contribute in viral surveillance and corneal pathogenesis. It is anticipated in accomplishing these goals, we will eludicate the contribution of pro-lymphangiogenesis factors in the generation of the adaptive immune response critical for the ocular pathology that includes the debilitating and sometimes blinding stromal keratitis.