We reported that fungal anti-oxidant pathways and iron binding molecules (siderophores) are essential for hyphal growth in the mammalian cornea (J Clin Invest 2012, PMC3708856; PLoS Pathogens 2013, PMC3534057). We also demonstrated that these pathways can be targeted using the anti-cancer drug PX-12, which inhibits the thioredoxin pathway, and by Simvastatin, which inhibits production of the Aspergillus siderophore TAFC (9, 10). In the current proposal, we also show preliminary data that inhibition of zinc transport impairs growth of Aspergillus hyphae in vitro. Studies outlined in the current proposal will examine PX-12, statins compared with other drugs that target these pathways, and which are either in routine clinical use, or which have gone through Phase I trials and shown to be non-toxic (all are commercially available). We will then combine the most effective compounds using a multi-target approach. In year 1, we will determine the most effective agents in a direct in vitro hyphal killing assay (Aim 1), in an in vitro assay designed to augment hyphal killing by human neutrophils (Aim 2), and in our established murine models of trauma induced and contact lens/biofilm induced fungal keratitis (Aim 3). In the second year, we will complete Aim 3 and based on findings in the murine models, we will examine efficacy in a new rabbit model of contact lens associated fungal keratitis. Amphotericin B or natamycin, as common therapies for fungal keratitis, will also be included, and we will examine cytotoxicity of each dru and combination. These novel approaches target essential pathways of hyphal growth in the cornea, have no anticipated systemic side effects as they are administered topically, and have considerable potential as novel therapies for this important disease.
Fusarium and Aspergillus filamentous fungi are a major cause of corneal ulcers worldwide. In developing nations, corneal injury being the major risk factor, whereas in the USA and in industrialized nations, contact lenses are the major risk factor. Current therapies, including Amphotericin B and natamycin have toxic side effects and are often ineffective, resulting in corneal transplants. Given the limited treatment options and the frequent treatment failures, there is a pressing need to develop new treatment strategies. In the current proposal, we will examine inhibitors of three essential biochemical pathways of these fungi that are required for growth in the cornea: fungal anti-oxidative pathways, and iron and zinc transport pathways. Compounds that target these pathways will be tested individually and in combination, and we will examine their activity on hyphal growth in vitro, in assays of hyphal killing by human neutrophils, and in murine and rabbit models of trauma induced and contact lens / biofilm related fungal keratitis. We anticipate that targeting these pathways as combined therapy will be more efficacious than standard treatments. Further, as the drugs to be tested are either in use clinically (such as statins) or have undergone clinical trials, we anticipate that they will be saf in addition to effective.
|Clark, Heather L; Minns, Martin S; Sun, Yan et al. (2018) Atovaquone Impairs Growth of Aspergillus and Fusarium Keratitis Isolates by Modulating Mitochondrial Function and Zinc Homeostasis. Invest Ophthalmol Vis Sci 59:1589-1598|