Abstract:
Rift Valley Fever Virus (RVFV) is an arbovirus that can infect ruminants and
humans. It can cause many diseases including encephalitis, hemorrhagic fever, and ocular
disease. A severe version of the disease is observed predominantly in pregnant and young
livestock. While it is primarily transmitted by mosquitoes, most human cases are acquired
through contact with blood or organs of an infected animal. Autophagy is an intracellular
pathway that allows for the degradation of cytoplasmic organelles during cellular stress.
The role of autophagy during viral infections is unclear. In some cases, it slows the
progression of the infection, whereas, in many other cases the virus uses the autophagy
system to enhance its replication. We hypothesized that inhibition of autophagy will cause
RVFV titer reduction and provide evidence that the process of autophagy can be pro-viral
to RVFV. To explore the impact of autophagy on RVFV replication, small molecule
modulators of autophagy were utilized. CA-5F, DBBC661, and ML240, which are all
known autophagy inhibitors, were shown to be capable of reducing RVFV infectious titers.
CA-5F was selected for further studies due to it being one of the most potent and least toxic
inhibitors. CA-5F is a late-stage autophagy inhibitor that functions by inhibiting the
autophagosome-lysosome fusion. Previous studies have shown CA-5F to have anti-tumor
effects against lung cancer cells. HSEACs (Human Small Airway Epithelial Cells) were
treated with non-toxic concentrations of CA-5F and a significant decrease in viral
production was observed. Furthermore, the greatest decrease in RVFV titers was observed
at 16 and 24 hours post-infection as compared to 8 hours post-infection. Additionally,
intracellular RNA analysis showed that although CA-5F decreases RVFV infectious titers
in a dose-dependent manner, it does not impact viral RNA production. This study provides
evidence that the autophagy inhibitor, CA-5F, is capable of reducing RVFV production.
Future studies will assess the importance of the viral protein NSs in CA-5F inhibition.
