Dissertation Defense Announcement
To: The George Mason University Community
Candidate: Ashwini Brahms
Program: PhD in Biosciences
Date: Friday June 23, 2017
Time: 1:00 PM
Place: George Mason University
Science & Tech campus
Bull Run Hall, Room 257
Title: "The Inhibition of Rift Valley Fever Virus Using FDA-Approved Drugs"
Committee Chair: Dr. Kylene Kehn-Hall
Committee Members: Dr. Monique van Hoek, Dr. Aarthi Narayanan, Dr. Mikell Paige
All are invited to attend the defense.
There are currently no FDA-approved therapeutics available to treat Rift Valley fever virus (RVFV) infection. In an effort to repurpose drugs for RVFV treatment, a library of FDA-approved drugs was screened to determine their ability to inhibit RVFV. Several drugs from varying compound classes, including inhibitors of growth factor receptors, microtubule assembly/disassembly, and DNA synthesis, were found to reduce RVFV replication. The hepatocellular and renal cell carcinoma drug, sorafenib, was the most effective inhibitor, being non-toxic and demonstrating inhibition of RVFV in a cell-type and virus strain independent manner. Mechanism of action studies indicated that sorafenib targets at least two stages in the virus infectious cycle, RNA synthesis and viral egress, and causes a buildup of virions within cells. Computational modeling studies also support this conclusion. In vivo experiments conducted using sorafenib treated mice demonstrated a trend toward increased survival and reduction in viral burden. siRNA knockdown studies suggested that non-classical targets of sorafenib are important for the propagation of RVFV. Confocal microscopy imaging revealed that Gn colocalizes and accumulates within the endoplasmic reticulum (ER), and the transport of Gn from the Golgi to the host cell membrane is reduced. Transmission electron microscopy demonstrated that sorafenib caused virions to be present inside large vacuoles inside the cells. P97/Vasolin-containing protein (VCP), a protein involved in membrane remodeling in the secretory pathway and a known target of sorafenib, was found to be important for RVFV egress. Knockdown of VCP resulted in decreased RVFV replication, reduced Gn Golgi localization, and increased Gn ER accumulation. An intracellular accumulation of RVFV virions was also observed in VCP siRNA transfected cells. Collectively these data indicate that sorafenib causes a disruption in viral egress by targeting VCP and the secretory pathway, resulting in a buildup of virions within dilated ER vesicles.