Combination Kinase Inhibitor Treatment Suppresses Rift Valley Fever Virus Replication

Inhibitors of the Ubiquitin-Mediated Signaling Pathway Exhibit Broad-Spectrum Antiviral Activities against New World Alphaviruses

New World alphaviruses including Venezuelan Equine Encephalitis Virus (VEEV) and Eastern Equine Encephalitis Virus (EEEV) are mosquito-transmitted viruses that cause disease in humans and equines. There are currently no FDA-approved therapeutics or vaccines to treat or prevent exposure-associated encephalitic disease. The ubiquitin proteasome system (UPS)-associated signaling events are known to play an important role in the establishment of a productive infection for several acutely infectious viruses. The critical engagement of the UPS-associated signaling mechanisms by many viruses as host–pathogen interaction hubs led us to hypothesize that small molecule inhibitors that interfere with these signaling pathways will exert broad-spectrum inhibitory activity against alphaviruses. We queried eight inhibitors of the UPS signaling pathway for antiviral outcomes against VEEV. Three of the tested inhibitors, namely NSC697923 (NSC), bardoxolone methyl (BARM) and omaveloxolone (OMA) demonstrated broad-spectrum antiviral activity against VEEV and EEEV. Dose dependency and time of addition studies suggest that BARM and OMA exhibit intracellular and post-entry viral inhibition. Cumulatively, our studies indicate that inhibitors of the UPS-associated signaling pathways exert broad-spectrum antiviral outcomes in the context of VEEV and EEEV infection, supporting their translational application as therapeutic candidates to treat alphavirus infections.

In Vitro Evaluation of Anti-Rift Valley Fever Virus, Antioxidant and Anti-Inflammatory Activity of South African Medicinal Plant Extracts

Rift valley fever virus (RVFV) is a mosquito-borne virus endemic to sub-Saharan African countries, and the first sporadic outbreaks outside Africa were reported in the Asia-Pacific region. There are no approved therapeutic agents available for RVFV; however, finding an effective antiviral agent against RVFV is important. This study aimed to evaluate the antiviral, antioxidant and anti-inflammatory activity of medicinal plant extracts. Twenty medicinal plants were screened for their anti-RVFV activity using the cytopathic effect (CPE) reduction method. The cytotoxicity assessment of the extracts was done before antiviral screening using the MTT assay. Antioxidant and reactive oxygen/nitrogen species' (ROS/RNS) inhibitory activity by the extracts was investigated using non-cell-based and cell-based assays. Out of twenty plant extracts tested, eight showed significant potency against RVFV indicated by a decrease in tissue culture infectious dose (TCID50) < 105. The cytotoxicity of extracts showed inhibitory concentrations values (IC50) > 200 µg/mL for most of the extracts. The antioxidant activity and anti-inflammatory results revealed that extracts scavenged free radicals exhibiting an IC50 range of 4.12-20.41 µg/mL and suppressed the production of pro-inflammatory mediators by 60-80% in Vero cells. This study demonstrated the ability of the extracts to lower RVFV viral load and their potency to reduce free radicals.

Host-based processes as therapeutic targets for Rift Valley fever virus

Rift Valley fever virus (RVFV) is an enveloped, segmented, negative sense RNA virus that replicates within the host's cytoplasm. To facilitate its replication, RVFV must utilize host cell processes and as such, these processes may serve as potential therapeutic targets. This review summarizes key host cell processes impacted by RVFV infection. Specifically the influence of RVFV on host transcriptional regulation, post-transcriptional regulation, protein half-life and availability, host signal transduction, trafficking and secretory pathways, cytoskeletal modulation, and mitochondrial processes and oxidative stress are discussed. Therapeutics targeted towards host processes that are essential for RVFV to thrive as well as their efficacy and importance to viral pathogenesis are highlighted.

Role of mitogen-activated protein kinase signaling in the pathogenesis of dengue virus infection

Dengue virus (DENV) infection is a disease that is endemic to many parts of the world, and its increasing prevalence ranks it among the diseases considered to be a significant threat to public health. The clinical manifestations of DENV infection range from mild dengue fever (DF) to more severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Increased proinflammatory cytokines and vascular permeability, both of which cause organ injury, are the hallmarks of severe dengue disease. Signs of liver injury were observed in studies using hepatic cell lines, mouse models, and autopsy specimens from DENV-infected patients, and these signs substantiated the effects of inflammatory responses and hepatic cell apoptosis. Mitogen-activated protein kinases (MAPK) are involved in inflammatory responses and cellular stress during viral infections. The roles of MAPK signaling in DENV infection were reviewed, and published data indicate MAPK signaling to be involved in inflammatory responses and hepatic cell apoptosis in both in vitro cultures and in vivo models. Modulation of MAPK signaling ameliorates the inflammatory responses and hepatic cell apoptosis in DENV infection. This accumulation of published data relative to the role of MAPK signaling in inflammatory responses and cell apoptosis in DENV infection is elucidatory, and may help to accelerate the development of novel or repositioned therapies to treat this unpredictable and often debilitating disease.