Inhibitors of Ubiquitin Signaling Pathways Exhibit Antiviral Activities against Venezuelan Equine Encephalitis Virus
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Abstract
Acutely infectious viruses including alphaviruses, Venezuelan equine encephalitis virus (VEEV) is vector transmitted, resulting in increased disease burden in the civilian and military population. Several of these pathogens are highly infectious and transmissible as aerosols, thus posing an increased threat as a potential bioweapon. Studies from GMU-CIDR laboratory and from several others have demonstrated the critical role of the host ubiquitination pathway in the establishment of a productive infection for acutely infectious viral agents. For example, it has been demonstrated that proteasome inhibitor Bortezomib was a broad-spectrum inhibitor of alphaviruses and bunyaviruses. Published studies have demonstrated that many viral proteins including the capsid protein of VEEV, the NS1, 3, and 5 proteins of Dengue Virus, VP35 protein of Ebola virus are ubiquitinated in infected cells. As part of efforts to characterize the host: viral protein interactome of alphaviruses using VEEV, we have identified several proteins involved in the ubiquitin-proteasome pathway as interacting with all the viral nonstructural proteins. These observations and evidence in the scientific literature prompted us to hypothesize that ubiquitin-proteasome inhibitors will constitute an excellent broad-spectrum strategy to address emerging/re-emerging viral challenges. As several viral proteins are known to be ubiquitinated in multiple sites, inhibiting such a broadly critical post-translational modification event is highly unlikely to result in resistant viruses. We examined multiple inhibitors of host signaling pathways using Venezuelan Equine Encephalitis Virus as a prototype pathogen. Of eight inhibitors that were tested for antiviral activities against the TC-83 strain of VEEV in three different cell lines (Vero, HMC3, and SVG-p12), NSC697923, Bardoxolone methyl (BARM), Omavelexelone (OMA) demonstrated robust inhibition of TC-83 at 1μM concentration. In vitro dosing studies conducted thus far have quantified viral loads following combined pre/post-treatment of cells, pre-treatment only, and post-treatment only conditions. The results identify combined pre/post-treatment as the most effective strategy in robustly reducing viral load between 2-4 logs.