Preparation of viral particles for screening
Spike-mNG pseudovirus was generated using pCMV14-3X-Flag-SARS-CoV-2 S (a gift from Zhaohui Qian Lab (Addgene plasmid #145780) (Ou et al., 2020). This vector carries a codon-optimized complementary DNA that encodes SARS-CoV-2-Spike glycoprotein (Wuhan 2019) along with a C-terminal 19 amino acid deletion. We performed site directed mutagenesis to make create the D614G mutation in spike and named it pCMV-SD614G. Spike-mNG pseudovirus was made by co-transfecting Lenti-X 293T (TakaraBio) cells with packaging vector psPAX2 (psPAX2 was a gift from Didier Trono, Addgene plasmid #12260), pLJM1-Lck-mNeonGreenvector and pCMV-SD614G. VSVG-mNG pseudovirus was made the same way except the envelop vector pCMV-VSV-G was used for the envelope instead of pCMV-SD614G (pCMV-VSV-G was a gift from Bob Weinberg, Addgene plasmid #8454) (Stewart et al., 2003). To make GagCre-VSVG viral particles, we transfected Lenti-X 293T cells with the vector pCMV-VSV-G and GagCre vector (GAG-CRErec was a gift from Philippe Mangeot & Théophile Ohlmann & Emiliano Ricci, Addgene plasmid #119971) (P. E. Mangeot et al., 2019). All the viruses were harvested 48h after transfection.