Figure S1.

Generation and HIV-1 pseudotype infection of ACE2-expressing cell lines. (A) 293T cells were stably transduced with a lentivirus vector CSIB expressing either wild-type ACE2 or catalytically inactive mutant ACE2*. Following selection, cells were used as uncloned bulk populations (B), or single-cell clones were isolated. Flow cytometry histograms show staining with an antibody against huACE2 (purple) or an isotype control (gray). (B) HT1080 cells were stably transduced as in A, and a single-cell clone used throughout this study is shown, stained as in A. (C) Infectivity of CCNanoLuc/GFP viruses, pseudotyped with either full-length or C-terminally truncated SARS-CoV and SARS-CoV-2 S proteins on 293T/ACE2*(B) cells. Virus particles generated in the absence of an S protein (No S) were used as background controls. Infectivity was quantified by measuring NanoLuc luciferase activity (RLU). Mean and range from two technical replicates is shown. (D) Infectivity of HIV-1_NLΔEnv-NanoLuc in the various cell lines. Virus generated in the absence of S is used as a background control and infectivity was quantified by measuring NanoLuc luciferase activity (RLU). Mean and range from two technical replicates are shown. (E) Same as D except that CCNanoLuc/GFP virus was used. (F) Effect of virus ultracentrifugation on the infectivity of HIV-1–based pseudotyped virus particles. 293T/ACE2*(B) cells were infected with equivalent doses of unconcentrated HIV-1_NLΔEnv-NanoLuc or the same virus that had be pelleted through 20% sucrose and then diluted to the original volume.