Abstract
The ongoing COVID-19 pandemic is caused by SARS-CoV-2. Although several effective vaccines that target the Spike protein on the viral surface have been deployed, additional therapeutic agents are urgently needed. Here, we developed a system to measure the Spike protein function by quantifying cellular membrane fusion induced by the Spike protein. The system enables the evaluation of the effects of drugs and neutralizing antibodies against SARS-CoV-2 without using live viruses. Furthermore, the system characterizes membrane fusion activity of the Spike protein of each variant to reveal that Delta variant has more potent than Wuhan and Omicron. Our system could lead to develop high-throughput screening for drug candidates and neutralization antibodies that target virus entry and characterize Spike proteins from variants.