COS 239-2 - Developing a treatment for Pseudogymnoascus destructans using RNA interference gene silencing

Abstract: White-Nose Syndrome (WNS), a disease caused by the fungal pathogen Pseudogymnoascus destructans (Pd), has led to the decline of several species of North American hibernating bats. The disease has been spreading on the continent since 2006, and several bat species are now threatened with extinction as a result. Suggested treatments to inhibit Pd include probiotics, epidermal fatty acids, fungicides, volatile organic compounds, and vaccines. However, no treatment or strategy has been widely implemented to limit the spread of Pd or its effects on bats. Treatments must both be effective and minimize deleterious non-target effects, particularly for other sympatric organisms. Potential treatments must also minimize any impact on hibernating bats. Ideally, treatment deployment should be effective in large caves harboring hundreds or thousands of widely-dispersed bats and in hidden, inaccessible crevices housing small, dense clusters of roosting bats. A viable solution must be innocuous to nontarget species, cost effective, wide-reaching, and easy to deploy.

We have used the published genomes of Pd and related species to design treatments that target critical fungal cell functions of Pd without nontarget effects. Ergosterol is a key component of fungal cell membranes and a common target of established antifungal treatments. We will attempt to disrupt ergosterol production by triggering RNA-interference-induced gene silencing and will evaluate changes in Pd growth in vitro. RNA interference (RNAi), instigated by the exogenous application of double-stranded RNA (dsRNA), has potential to serve as a viable Pd control. This noninvasive application is conceptually practical as dsRNA is a naturally occurring biological molecule with no expected toxicity or deleterious effects on bats or other organisms. dsRNA-based applications can be designed to target species-specific RNA transcripts to prevent translation into proteins. Our treatment design strategy addresses many challenges such as effectiveness, risk minimization, and ease of deployment, thereby providing a novel alternative to control Pd. Although our treatment is not targeted at inhibit bat to bat transmission, it is targeted at ergosterol pathways which eventually result in lysis and death of fungal cells, reducing pathogen load in the environment when applied to hibernacula substrate. The ultimate goal is designing an aerosolized, RNAi-based, sprayable application that successfully controls Pd growth in North American hibernacula and may give bat populations time to develop resistance to WNS.