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.

VP35 blocks RIG-I-driven type I IFN production and PKR activation by both sequestering dsRNA intermediates and binding to the PKR/RIG-I activator PACT (Bale et al., 2013; Cardenas et al., 2006; Feng et al., 2007; Leung et al., 2010; Luthra et al., 2013; Schumann et al., 2009) . Furthermore, mutations in the dsRNA-binding pocket of EBOV VP35 were found to increase type I IFN induction in vitro and severely attenuate viral growth in vivo (Hartman et al., 2008; Prins et al., 2010) . However, the relative importance of individual dsRNA-triggered cytoplasmic sensors for control of EBOV replication has not been clearly delineated. Our data here show that dCas9-KRAB-mediated knockdown of either RIG-I or PKR in A549 cells leads to a significant increase in EBOV replication ($1 log) after 72 h, directly demonstrating that both these host molecules contribute to control of EBOV growth. The fact that a wild-type clinical EBOV isolate with an intact VP35 as part of its genome is still susceptible to the effects of RIG-I and PKR underscores the critical roles played by both these factors in host control of EBOV. Furthermore, our data showing that NTZ's efficacy against EBOV is reduced when host cell expression of either PKR or RIG-I is ablated, indicates that the ability of NTZ to increase the activity of PKR and RIG-I at an early stage of EBOV infection, can tip the balance in favor of the host by blunting VP35's ability to suppress the innate immune response.