Generation of Novel Antivirals Against Emerging Tick-Borne Viruses

摘要

Tick-borne viral diseases are an emerging threat in the United States and worldwide. Due to their recent emergence and the sporadic nature of zoonotic pathogenic threats, there have yet to be any approved therapeutics or vaccines for emerging viral threats. Severe fever with thrombocytopenia syndrome virus (SFTSV) and Heartland virus (HRTV) are two emerging tick-borne phenuiviruses, which cause hemorrhagic-like fever illness in humans due to an aberrant inflammatory response, which we hypothesized is driven by the nuclear factor kappa B (NF-κB) pathway. In order to address this hypothesis, we first we established BSL-2 systems (miniature genomes; minigenomes) to model transcription and replication of SFTSV and HRTV without the use of infectious virus (Chapter 2). To directly test the hypothesis that a pro-inflammatory environment, stimulated through NF-κB, supports viral replication and transcription, we used the minigenome systems to screen NF- κB inhibitors and other compounds with antiviral and anti-inflammatory properties (Chapter 3). We found that the NF-kB inhibitor, SC75741, prevents viral transcription and replication using minigenome systems for both SFTSV and HRTV and confirmed this finding in vitro using SFTSV or HRTV infected cells. Finally, we hypothesized that the NF-κB pathway is stimulated by the viral non-structural proteins of HRTV and SFTSV, which are virulence determinants (Chapter 4). Indeed, we observed that expression of either the SFTSV or HRTV NSs proteins led to activation of the NF-κB promoter, activation of the IL-8 promoter, and secretion of IL-8, which has been noted to be elevated in patients with fatal SFTSV infection. Taken together, this work not only had established a novel screening system for inhibitors of viral transcription and replication that can be expanded to other drug classes but has also solidified the role of the non-structural proteins of two emerging, tick-borne phenuiviruses in activating the pro-inflammatory response to promote viral persistence. This thesis has broadened our understanding of the role of systemic inflammatory response syndrome seen during SFTSV and HRTV infection and identified druggable targets that could be developed as medical countermeasures.