The FDA-Approved Oral Drug Nitazoxanide Amplifies Host Antiviral Responses and Inhibits Ebola Virus

Jasenosky, Luke D.; Cadena, Cristhian; Mire, Chad E.; Borisevich, Viktoriya; Haridas, Viraga; Ranjbar, Shahin; Nambu, Aya; Bavari, Sina; Soloveva, Veronica; Sadukhan, Supriya; Cassell, Gail H.; Geisbert, Thomas W.; Hur, Sun; Goldfeld, Anne E.

Here, we show that treatment of cells with NTZ results in broad amplification of the host innate immune response, including an increase in RIG-I-like receptor (RLR) activation in response to stimulation with cytoplasmic dsRNA, enhanced mitochondrial antiviral signaling protein (MAVS) and interferon regulatory factor 3 (IRF3) activities, and transcriptional induction of the antiviral phosphatase GADD34. Based on these data, we hypothesized that NTZ could limit or overcome EBOV's ability to evade detection by critical innate immune sensors following viral entry. At concentrations reflective of routine oral dosing for parasitic infections, NTZ significantly inhibits EBOV replication in A549 cells. Furthermore, using CRISPR/dead (d) Cas9-KRAB promoter targeting to ablate expression of individual host factors, we show that NTZ's inhibitory effect against EBOV relies on both RIG-I and PKR, indicating that NTZ can overcome EBOV VP35's ability to prevent viral detection by these cytoplasmic sensors. We also show that NTZ significantly inhibits a second negative-strand RNA virus, vesicular stomatitis virus (VSV), through a distinct mechanism involving both RIG-I and GADD34, but not PKR, consistent with the different innate immune evasion strategies employed by VSV when compared with EBOV. Thus, NTZ establishes a broad ''antiviral'' milieu that is rapidly amplified upon viral infection and is capable of counteracting varied virus-specific immune evasion strategies, such as those employed by EBOV and VSV.