Doctoral Dissertations

Date of Award

8-2005

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Comparative and Experimental Medicine

Major Professor

Barry T. Rouse

Committee Members

Robert N. Moore, Albert T. Ichiki, Mark Y. Sangster

Abstract

Herpetic stromal keratitis (SK) is an immunopathological and tissue destructive corneal lesion caused by herpes simplex virus (HSV) infection, which induces an intense autoimmune inflammatory response and finally leads blindness. Accumulating evidence using the murine model has shown that Th-1 phenotype CD4+ T cells orchestrating the inflammation mainly contribute the immunopathological reaction in HSV-1 infected cornea. However, prior to CD4+ T cell infiltration into corneal lesions, various innate immune cells recruit and produce numerous inflammatory molecules into the corneal stroma. Interestingly, one prominent event early in the pathogenesis of SK is neovascularization of the usually avascular cornea. It is assumed that various angiogenic factors produced by inflammatory cells trigger the onset of pathological angiogenesis and the newly formed leaky blood vessels may assist corneal access of inflammatory cells orchestrating herpetic SK. Accordingly, inhibition of unwanted angiogenesis in an HSV infected cornea may moderate the pathologic process of SK lesions.

The first part (Part I) of this dissertation focuses on the understanding of HSV-1 induced SK pathogenesis including how abnormal neovascularization is generated after virus infection and how angiogenesis contributes the process of disease. The other parts (Part II, III, IV) explore the use of different antiangiogenic approaches as an effective therapeutic strategy for herpetic SK. Results in Part II demonstrate that the use of vascular endothelial growth factor (VEGF) pathway-specific siRNAs can efficiently knock down their target genes and consequently inhibit HSV induced angiogenesis. Results of the third section (Part III) clarify the antiangiogenic role of IL-18 in the cornea. The data show that IL-18 down-regulates the expression of VEGF and also controls the proliferation of activated endothelial cells in inflammatory conditions. Furthermore, application of DNA encoding IL-18 into cornea diminished herpetic SK lesion severity. The final section (Part IV) explores the utilization of a VEGF receptor-2 (VEGFR-2 or FLK-1) based DNA vaccine to enhance immune response against endothelial cells expressing VEGFR-2. HSV-1 infected mice receiving attenuated Salmonella typhimurium harboring VEGFR-2 exhibited antiangiogenic response and reduced herpetic SK severity. These effects appeared to be due to the ability of cytotoxic CD8+ T cells targeting VEGFR-2 to control virus induced neovascularization.

In this study, experiments were designed to focus on controlling the pathological angiogenesis in herpetic SK model. We hope that these approaches may represent useful therapeutic strategies against neovascularization-related eye diseases.

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