Counteracting Neuroinvasive RNA Viruses: Antiviral and Immune Modulation Strategies Against SARS-CoV-2 and VEEV

Abstract

The global response to the COVID-19 pandemic and our inability to mitigate spread of SARS-CoV-2 has highlighted areas of research that warrant further study. RNA viruses have since been at the forefront for pandemic and prevention preparedness due to their increased potential to cause future outbreaks. SARS-CoV-2 and Venezuelan equine encephalitis virus (VEEV) are both zoonotic positive-sense single-stranded RNA viruses. Clinical cases of VEEV infected humans present with febrile illness that ultimately resolves. VEEV infection in humans cause febrile-like illness with high morbidity and low mortality rates (<1), with a subset of cases exhibiting neurological sequalae (4-14%). Equine (horses, donkeys, mule) are typically more several impacted during epizootic outbreaks with high morbidity and high mortality (up to 75%). VEEV has a history of biological weaponization by the United States and Former Soviet Union and is classified as select agent by the Center for Diseases Control and Prevention due to ease of aerosol dissemination, high morbidity among humans and high mortality rates in equids. VEEV continues to be a pathogen of concern due to its emergence and re-emergence of epizootic strains.

The spread of SARS-CoV-2 was difficult to manage not only because of its novelty but in part due to the lack of established interventions. Non-pharmaceutical countermeasures played a critical role in decreasing viral spread among communities. In instances where social distancing practices were implemented (minimum 6 feet), people quarantine upon feeling ill or exposure to positive cases, proper mask usage by both the infected and uninfected individual, and increased ventilation saw decreased viral transmission. Despite this success, there is still a need for more non-pharmaceutical countermeasures. Personal protective equipment (PPE) such as masks can be augmented with additives to enhance the antimicrobial effects. Bioceramic silicon nitride has been approved and successfully used in patients receiving orthopedic implants. Silicon nitride exhibited antimicrobial activity reducing the likelihood of post-surgical complications due to infection. Our overarching research goal is to test silicon nitride's antiviral activity for potential future integration into PPE for non-pharmaceutical countermeasure use. We have tested the antiviral activity of powered silicon nitride against multiple SARS-CoV-2 variants and MERS-CoV and silicon nitride embedded into nonwoven fabric against a SARS-CoV-2 ancestral strain. The powder form of silicon nitride had pan-coronavirus activity through RNA degradation of SARS-CoV-2 and MERS-CoV. Silicon nitride embedded into nonwoven fabric had significant antiviral activity against SARS-CoV-2. Collectively, we have shown silicon nitride to be a viable option for mask augmentation to enhance broad-spectrum antiviral activity.

Previous studies have shown activation of the Type I interferon (IFN) response prior to VEEV infection led to viral inhibition. Interferon stimulated genes (ISGs) are produced in response to VEEV infection and can be regulated through multiple arms of the Type I IFN response. Numerous studies have explored the role of RIG-I/MAVS signaling during VEEV infection, but little is known about cGAS-STING involvement. The rationale in pursuing this pathway is mechanism studies can lead to discovery of possible targets of therapeutic intervention. cGAS-STING signaling has been proposed to regulate or activate in response to VEEV infection due to VEEV-induced mitochondrial dysregulation and likely release of mtDNA into the cytosol. Limited data is available as it relates to VEEV and the cGAS-STING pathway. Previous studies conducted using chikungunya virus (CHIKV) found CHIKV to not only antagonize this pathway by degrading cGAS but also STING was essential in limiting pathogenesis. We aimed to address this gap in knowledge through characterizing the role of STING during VEEV infection. Our studies utilizing human microglial cells revealed VEEV induces a Type I interferon (IFN) response independent of STING. Additionally, VEEV is able to antagonize this pathway through inhibition of STING phosphorylation at residue Se3r366.

Together, the data shows alternative research approaches in controlling spread of infectious disease. The silicon nitride embedded nonwoven fabric centers around an application-based study design, and the results may provide quicker real-world implications. Whereas the mechanistic studies into STING role during VEEV infection provides foundational science that is necessary for the long-term advancement of both pharmaceutical and nonpharmaceutical interventions alike.