High throughput screening identifies broad-spectrum Coronavirus entry inhibitors (preprint)

The Covid-19 pandemic highlighted the pressing need for antiviral therapeutics capable of mitigating infection and spread of emerging coronaviruses (CoVs). A promising therapeutic strategy lies in inhibiting viral entry mediated by the Spike (S) glycoprotein. To identify small molecule inhibitors that block entry downstream of receptor binding, we established a high-throughput screening (HTS) platform based on pseudoviruses. We employed a three-step process to screen nearly 200,000 small molecules. First, we identified potential inhibitors by assessing their ability to inhibit pseudoviruses bearing the SARS-CoV-2 S glycoprotein. Subsequent counter-screening against pseudoviruses with the Vesicular Stomatitis Virus spike glycoprotein (VSV-G), yielding sixty-five SARS-CoV-2 S-specific inhibitors. These were further tested against pseudoviruses bearing the MERS-CoV S glycoprotein, which uses a different receptor. Out of these, five compounds including the known broad-spectrum inhibitor Nafamostat, were subjected to further validation and tested them against pseudoviruses bearing the S glycoprotein of the alpha, delta, and omicron variants as well as against bona fide SARS-CoV-2 in vitro. This rigorous approach revealed a novel inhibitor and its derivative as a potential broad-spectrum antiviral. These results validate the HTS platform and set the stage for lead optimization and future pre-clinical, in vivo studies.

Genetically engineered MRI-trackable extracellular vesicles as SARS-CoV-2 mimetics for mapping ACE2 binding in vivo (preprint)

The elucidation of viral-receptor interactions and an understanding of virus-spreading mechanisms are of great importance, particularly in the era of pandemic. Indeed, advances in computational chemistry, synthetic biology, and protein engineering have allowed precise prediction and characterization of such interactions. Nevertheless, the hazards of the infectiousness of viruses, their rapid mutagenesis, and the need to study viral-receptor interactions in a complex in vivo setup, call for further developments. Here, we show the development of biocompatible genetically engineered extracellular vesicles (EVs) that display the receptor binding domain (RBD) of SARS-CoV-2 on their surface as coronavirus mimetics (EVsRBD). Loading EVsRBD with iron oxide nanoparticles makes them MRI-visible, and thus, allows mapping of the binding of RBD to ACE2 receptors non-invasively in live subjects. Importantly, the proposed mimetics can be easily modified to display the RBD of SARS-CoV-2mutants, namely Delta and Omicron, allowing rapid screening of newly raised variants of the virus. The proposed platform thus shows relevance and cruciality in the examination of quickly evolving pathogenic viruses in an adjustable, fast, and safe manner.

Receptor binding and escape from Beta antibody responses drive Omicron-B.1.1.529 evolution (preprint)

On the 24th November 2021 the sequence of a new SARS CoV-2 viral isolate spreading rapidly in Southern Africa was announced. Omicron contains a total of 30 substitutions plus deletions and an insertion in Spike, far more than any previously reported variant. The mutations include those previously identified by In-vitro evolution to contribute to high-affinity binding to ACE2, including mutations Q498R and N501Y critical in forming additional interactions in the interface. Together with increased charge complementarity between the RBD and ACE2, these substantially increase affinity and potentially virus transmissibility through increased syncytia formation. Further mutations promote immune evasion. We have studied the binding of a large panel of potent monoclonal antibodies generated from early pandemic or Beta infected cases. Mutations in Omicron will likely compromise the binding of many of these and additionally, the binding of antibodies under commercial development, however residual binding should provide protection from severe disease.