Development and Evaluation of Novel Aptamer-based Therapeutics Targeting SARS-CoV-2 in a Physiologically-Relevant Model of Human Airway Epithelium

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The impact of SARS-CoV-2 on public health and the global economy cannot be overstated. As of September 28, 2020, 33,224,222 cases and 999,298 deaths worldwide have been linked to this emergent virus. This staggering number continues to grow, with the United States baring disproportionately high rates of morbidity and mortality. The virus targets the respiratory tract, leading to a wide range of clinical outcomes including mild upper respiratory tract illness and severe viral pneumonia with respiratory failure. To date, four SARS-CoV-2 vaccine candidates have entered phase 3 clinical trials and a massive parallel effort has been undertaken to repurpose already FDA-approved drugs for the treatment of COVID-19 or identify compounds with potential therapeutic activity. Despite this effort, remdesivir remains the only approved (with emergency use authorization) direct-acting antiviral for the treatment of COVID-19. Of critical importance: there is currently no vaccine or SARS-CoV-2-specific therapy approved for the prevention or treatment of disease. Furthermore, multiple antivirals may be required to avoid the rapid emergence of resistant SARS-CoV-2 strains. Thus, the development of novel therapeutics targeting SARS-CoV-2 are urgently needed. Infection requires interaction between the viral surface protein, spike (S), and a host protein, ACE2, that is expressed on type II alveolar cells and ciliated cells in the human airway epithelium (HAE), making these cells potentially vulnerable to infection. Thus, our goal is to develop a novel therapeutic that blocks this interaction between spike (on the virus) and ACE2 (on the host cell) to prevent infection and ameliorate disease. Aptamers are short nucleic acid-based sequences that bind with high affinity to their targets. Among other applications, aptamers have been shown to have potent antiviral activity and low toxicity in cell culture. While aptamers were originally made with RNA and DNA, Xeno-Nucleic Acids (XNA: nucleotide analogs with altered sugar, base, or phosphate backbones) have emerged as important new substrates and XNA aptamers often demonstrate enhanced target binding and greater stability compared to RNA and DNA aptamers. Thus, we hypothesize that aptamer technology, and specifically XNA aptamers, can be leveraged to inhibit spike-ACE2 interaction and propose to establish an innovative, in vitro screening platform that can serve to assess the efficacy of such aptamers, or other novel therapeutics, in blocking infection. This platform will utilize SARS-CoV-2 pseudoparticles (allowing work under Biosafety Level 2 containment) and a physiologically-relevant in vitro model of human airway epithelium that recapitulates the mucosal surface of the airway in vivo. Aptamers will also be tested using live virus infections of culture cells (Biosafety Level 3). This work is highly significant given the immediate need for novel therapeutics against SARS-CoV-2. Further, the development of a high-throughput, pseudoparticle-based assay to assess viral entry in a relevant culture system will have broad applications for additional drug screens and / or studies that aim to further understand SARSCoV- 2 virus-host interactions at the level of particle uptake.