Repurposing Fendiline as a novel anti‐viral therapeutic
Authors: Husby Monica L. , Stahelin Robert 
Published: June 2021

The most prolonged and fatal outbreak of the Ebola virus (EBOV) occurred in 2014, claiming the lives of thousands. Although more than 40 years have passed since the initial discovery of EBOV, there are still no available treatments with FDA approval. Clinical case studies from human survivors highlighted that a hallmark of survival is a measurable immune response against specific viral proteins, such as VP40. VP40, is the canonical mediator of EBOV budding. Therefore, slowing down viral propagation through inhibiting replication, trafficking or budding could be the key to developing an efficacious treatment.

VP40 interacts with host proteins and lipids to oligomerize at the plasma membrane (PM) to form the filamentous structure of the virus. The initial association between VP40 and the PM is through electrostatic and stereospecific interactions with phosphatidyl serine (PS). Following PM docking, VP40 filamentous oligomerization is also dependent upon the presence of PS at the PM. These filaments are the building block for nascent viral particles, which will ultimately bud from the cell to propagate the virus within the host. Therefore, PS within the inner leaflet of the PM is essential for viral budding and propagation. Moreover, VP40's ability to produce virus like particles (VLPs) when expressed in mammalian cells, even in the absence of the other viral proteins, allows EBOV budding to be studied in a BSL‐2 setting.

Fendiline, an FDA approved drug for coronary heart disease, has been shown to significantly reduce PS from the PM. Therefore, this project focuses on repurposing Fendiline as a novel anti‐viral therapy to inhibit EBOV budding. We hypothesized that treating HEK 293 with Fendiline, would reduce VP40's ability to bind to the PM, oligomerize, and ultimately inhibit VLP production.

To monitor Fendiline's effect on PS in HEK293 cells, live cell confocal imaging experiments were performed on HEK 293 cells expressing the high affinity PS probe, GFP‐LactC2. After 48 hours of treatment, 5 uM Fendiline significantly reduced GFP‐LactC2 localization at the PM by ~25% (p=0.03). Lipidomic analysis of HEK 293 cells also revealed a significant reduction in total cellular levels of PS after 48 hours of 5 uM treatment (~30%, p=0.03). To assess the effect of Fendiline on VP40 binding to the PM, HEK 293 cells expressing GFP‐VP40 were treated with Fendiline and monitored for 48 hours. Again, after 48 hours of 5 uM treatment, there was a significant reduction of GFP‐VP40 localization to the PM (~15%, p=0.0001). Functional budding assays were performed to assess the effect of Fendiline on VLP production. After 48 hours, 5 uM Fendiline reduced VLP production by ~60% (p=0.025). Scanning electron microscopy experiments revealed a significant reduction in filamentous particle length and density after 48 hours of 1 uM or 5 uM Fendiline treatment compared to untreated cells expressing FLAG‐VP40(p<0.01).

Our project has highlighted that repurposing drugs such as Fendiline and targeting lipid metabolism are promising avenues for developing anti‐viral therapies. The next stop for this project is to extend the studies into live virus models in a BSL‐4 setting.

Support or Funding Information

This work has been supported by NIH training grant T32GM075762 and NIH AI081077

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.