Development of a mutant aerosolized ACE2 that neutralizes SARS-CoV-2 in vivo (preprint)

The rapid evolution of variants of SARS-CoV-2 highlights the need for new therapies to prevent disease spread. SARS-CoV-2, like SARS-CoV-1, uses the human cell surface protein angiotensin-converting enzyme 2 (ACE2) as its native receptor. Here, we design and characterize a mutant ACE2 that enables rapid affinity purification of a dimeric protein by altering the active site to prevent autoproteolytic digestion of a C-terminal His10 epitope tag. In cultured cells, mutant ACE2 competitively inhibits lentiviral vectors pseudotyped with spike from multiple SARS-CoV-2 variants, as well as infectious SARS-CoV-2. Moreover, the protein can be nebulized and retains virus-binding properties. We developed a system for delivery of aerosolized ACE2 to K18-hACE2 mice and demonstrate protection by our modified ACE2 when delivered as a prophylactic agent. These results show proof-of-concept for an aerosolized delivery method to evaluate anti-SARS-CoV-2 agents in vivo and suggest a new tool in the ongoing fight against SARS-CoV-2 and other ACE2-dependent viruses.

LY6E protects mice from pathogenic effects of murine coronavirus and SARS-CoV-2 (preprint)

LY6E is an antiviral protein that inhibits coronavirus entry. Its expression in immune cells allows mice to control murine coronavirus infection. However, it is not known which immune cell subsets mediate this control or whether LY6E protects mice from SARS-CoV-2. In this study, we used tissue-specific Cre recombinase expression to ablate Ly6e in distinct immune compartments or in all epiblast-derived cells, and bone marrow chimeras to target Ly6e in a subset of radioresistant cells. Mice lacking Ly6e in Lyz2-expressing cells and radioresistant Vav1 expressing cells were more susceptible to lethal murine coronavirus infection. Mice lacking Ly6e globally developed clinical disease when challenged with the Gamma (P.1) variant of SARS-CoV-2. By contrast, wildtype mice and mice lacking type I and type III interferon signaling had no clinical symptoms after SARS-CoV-2 infection. Transcriptomic profiling of lungs from SARS-CoV-2-infected wildtype and Ly6e knockout mice revealed a striking reduction of secretory cell-associated genes in infected knockout mice, including Muc5b, an airway mucin-encoding gene that may protect against SARS-CoV-2-inflicted respiratory disease. Collectively, our study reveals distinct cellular compartments in which Ly6e confers cell intrinsic antiviral effects, thereby conferring resistance to disease caused by murine coronavirus and SARS-CoV-2.

Identification of Atovaquone, Ouabain and Mebendazole as FDA Approved Drugs Tar-geting SARS-CoV-2 (Version 4) (preprint)

The newly emerged coronavirus, SARS-CoV-2, and the resulting COVID-19 disease, has spread swiftly across the globe since its initial detection in December 2019. Given the heavy toll of this pandemic, therapeutic options for treatment are urgently needed. Here, we adopted a repositioning approach using in-silico molecular modeling to screen FDA-approved drugs with established safety profiles for potential inhibitory effects against SARS-CoV-2. We used structure-based drug design to screen more than 2000 FDA approved drugs against SARS-CoV-2 main protease enzyme (Mpro) substrate-binding pocket, focusing on two potential sites (central and terminal sites) to identify hits based on their binding energies, binding modes, interacting amino acids, and therapeutic indications. We additionally screened the top hits from both sites for potential covalent binding via nucleophilic thiol attack of Cys 145. High-scoring candidates were then screened for antiviral activity against infectious SARS-CoV-2 in a cell-based viral replication assay, and counterscreened for toxicity. Atovaquone, Mebendazole, and Ouabain exhibited antiviral efficacy with IC50s well within their respective therapeutic plasma concentrations (low nanomolar to low micromolar range), and limited toxic effects. Notably, all three were predicted in docking studies to covalently bind SARS-CoV-2 Mpro, underscoring the utility of this in-silico approach for identifying putative antivirals for repurposing. These results do not confirm efficacy in animal models or in humans, but rather serve as a starting point for testing the antiviral potential of select FDA-approved drugs, either individually or in combination.