Ebola virus (EBOV) is among the most devastating pathogens causing fatal hemorrhagic
fever in humans. The epidemics from 2013 to 2016 resulted in more than 11,000 deaths, and another outbreak is currently ongoing. Since there is no FDA-approved drug so far to fight EBOV
infection, there is an urgent need to focus on drug discovery. Considering the tight correlation between the high EBOV virulence and its ability to suppress the
type I interferon (IFN-I) system, identifying molecules targeting
viral protein VP24, one of the main virulence determinants blocking the IFN response, is a promising novel anti-EBOV
therapy approach. Hence, in the effort to find novel EBOV inhibitors, a screening of a small set of
flavonoids was performed; it showed that
quercetin and
wogonin can suppress the VP24 effect on IFN-I signaling inhibition. The mechanism of action of the most active compound,
quercetin, showing a half-maximal inhibitory concentration (IC50) of 7.4 μM, was characterized to significantly restore the IFN-I signaling cascade, blocked by VP24, by directly interfering with the VP24 binding to
karyopherin-α and thus restoring P-STAT1 nuclear transport and IFN gene transcription.
Quercetin significantly blocked
viral infection, specifically targeting EBOV VP24 anti-IFN-I function. Overall,
quercetin is the first identified inhibitor of the EBOV VP24 anti-IFN function, representing a molecule interacting with a viral binding site that is very promising for further drug development aiming to block EBOV
infection at the early steps.