Fungal corneal ulcers are a significant cause of ocular morbidity and unilateral blindness worldwide. Though such infections are most prevalent in tropical climates- accounting for up to 50% of all microbial ulcers in Southern India- they are also commonplace in the subtropical United States. Moreover, from 2005 to 2006, the CDC reported an outbreak of 130 fungal ulcers associated with Renu Moisture Loc contact lens solution, thereby demonstrating that fungal keratitis can transcend traditional geographical barriers. The NEI funded Mycotic Ulcer Treatment Trial (MUTT) enrolled 323 patients across India to determine the relative efficacy of topical voriconazole and natamycin monotherapies. The fact that nearly 20% of all patients developed a corneal perforation or required corneal transplantation, despite the closely monitored administration of the best drugs available, underscores a critical need for better treatment options. This proposal seeks to discover novel antifungal strategies by uncovering pathways important for fungal virulence. To this end, the researchers and clinicians that carried out the MUTT will together leverage the vast collection of fungal specimens and clinical data obtained during that study. A focus will be placed on Fusarium species as they are the most frequent cause of keratitis.
In Aim 1, the 128 Fusarium isolates from the MUTT (50% of culture-positive cases) will be scrutinized with respect to basic growth parameters, stress resistance phenotypes, secreted protein profiles, and immune cell interactions. These in vitro datasets will then be statistically assessed against the prospectively collected patient information to determine which phenotypic parameters or secreted proteins correlate with worsened clinical outcome. In this way, the discovery of fungal virulence pathways will be informed by context-specific clinical data, as opposed to choosing candidate pathways based on work in disparate organism or alternative disease models.
Aim 2 will explore the regulation of fungal virulence pathways by light, an environmental cue that is uniquely relevant to corneal infections. Previous work has shown that fungal photosensory pathways centrally regulate metabolism, stress resistance and even drug sensitivity in Aspergillus as well as all Fusarium species so far tested. Accordingly, the in vitro and proteomics experiments described above will be performed in both the light and dark to systematically determine the extent to which the environment might augment fungal pathogenic potential and be exploited to a therapeutic end. Taken together, the work seeks to better understand the pathogenesis of fungal corneal infection to inform better antifungal therapy for this particularly severe form of keratitis.
Fungal keratitis is an important cause of ocular morbidity and blindness worldwide, owed largely to the lack of effective drugs currently available to manage such infections. This project will involve analyzing biological characteristics of hundreds of fungal keratitis specimens and statistically comparing the data to the associated patient outcomes. Doing so will allow for the identification of fungal traits or pathways that correlate with disease severity and could therefore serve as targets for novel antifungals.
