Coronavirus disease 2019 (COVID­-19) is a respiratory illness that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-­CoV-­2) and leads to numerous deaths. SARS-CoV-2 enters cells using its Spike protein, which is also a prospective target for the development of new anti-COVID­-19 drugs. Therefore, searching for novel therapeutic agents with Spike inhibitory activity is an urgent task. Oligoribonucleotides-D-mannitol (ORNs-D-M) complexes possess antiviral activity by inhibiting the activity of surface viral proteins. We hypothesized that the ORNs-D-M could inhibit SARS­-CoV­-2 Spike activity. Because SARS-CoV-2 is a biosafety-level-3 virus, one way to simplify such assays is to pseudotype biosafety-level-2 viral particles with Spike. In this study, we aimed to evaluate the ORNs-D-M efficiency against pseudotyped lentiviral particles with SARS-CoV-2 Spike.

We obtained SARS-CoV-2 Spike-pseudotyped lentiviral particles (Spike-pseudovirus) by transfecting the 293T cells with a plasmid complex (lentiviral backbone (Luciferase-IRES-ZsGreenbackbone), Spike SARS-CoV-2 and the other HIV proteins needed for virion formation). Microscope images showed the ZsGreen expression in the infected 293T-ACE2 cells with Spike-pseudovirus. Low ZsGreen fluorescence was observed in the infected 293T-ACE2 cells with Spike-pseudoviruses that were pre-incubated with the ORNs-D-M compared to the Spike-pseudovirus control. Luciferase expression was indicated in the infected 293T-ACE2 cells with Spike-pseudovirus. It was found that pre-incubation of the Spike-pseudovirus with the ORNs-D-M significantly reduced luciferase activity compared to the Spike-pseudovirus control. Decreased expression of ZsGreen and luciferase, marker proteins of cell infection with Spike-pseudovirus, potentially indicates that the ORNs-D-M interact with SARS-CoV-2 Spike and inhibit the interaction of Spike-pseudovirus with host cells. The obtained results show that the ORNs-D-M can have anti-COVID-­19 activity.