Loss of furin site enhances SARS-CoV-2 spike protein pseudovirus infection

Background: SARS-CoV-2 has a significant impact on healthcare systems all around the world. Due to its high pathogenicity, live SARS-CoV-2 must be handled under biosafety level 3 conditions. Pseudoviruses are useful virological tools because of their safety and versatility, but the low titer of these viruses remains a limitation for their more comprehensive applications.Method: Here, we constructed a Luc/eGFP based on a pseudotyped lentiviral HIV-1 system to transduce SARS-CoV-2 S glycoprotein to detect cell entry properties and cellular tropism. Results: The furin cleavage site deletion of the S protein removed (SFko) can help SARS-CoV-2 S to be cleaved during viral packaging to improve infection efficiency. The furin cleavage site in SARS-CoV-2-S mediates membrane fusion and SFko leads to an increased level of S protein and limits S1/S2 cleavage to enhance pseu-dovirus infection in cells. Full-length S (SFL) pseudotyped with N, M, and E helper packaging can effectively help SFL infect cells. Finally, pseudotyped SFko particles were successfully used to detect neutralizing antibodies in RBD protein-immunized mouse serum.Conclusion: Overall, our study indicates a series of modifications that result in the production of relatively high-titer SARS-COV-2 pseudo-particles that may be suitable for the detection of neutralizing antibodies from COVID-19 patients.