A plasmid expressing a C-terminally truncated SARS-CoV-2 S protein (pSARS-CoV2-S
trunc) was generated by insertion of a human-codon optimized cDNA encoding SARS-CoV-2 S lacking the C-terminal 19 codons (Geneart) into pCR3.1. The S ORF was taken from “Wuhan seafood market pneumonia virus isolate Wuhan-Hu-1” (NC_045512). For expression of full-length SARS-CoV S protein, “Human SARS coronavirus Spike glycoprotein Gene ORF cDNA clone expression plasmid (Codon Optimized)” (here referred to as pSARS-CoV-S) was obtained from SinoBiological (Cat: VG40150-G-N). An
env-inactivated HIV-1 reporter construct (pNL4-3ΔEnv-nanoluc) was generated from pNL4-3
31 (link) by introducing a 940 bp deletion 3’ to the
vpu stop-codon, resulting in a frameshift in
env. The human codon-optimized nanoluc Luciferase reporter gene (
Nluc, Promega) was inserted in place of nucleotides 1–100 of the
nef-gene. To generate pseudotyped viral stocks, 293T cells were transfected with pNL4-3ΔEnv-nanoluc and pSARS-CoV2-S
trunc or pSARS-CoV-S using polyethyleneimine. Co-transfection of pNL4-3ΔEnv-nanoluc and S-expression plasmids leads to production of HIV-1-based virions carrying either the SARS-CoV-2 or SARS-CoV spike protein on the surface. Eight hours after transfection, cells were washed twice with PBS and fresh media was added. Supernatants containing virions were harvested 48 hours post transfection, filtered and stored at −80°C. Infectivity of virions was determined by titration on 293T
ACE2 cells. See also
https://www.biorxiv.org/content/10.1101/2020.06.08.140871v1.
Robbiani D.F., Gaebler C., Muecksch F., Lorenzi J.C., Wang Z., Cho A., Agudelo M., Barnes C.O., Gazumyan A., Finkin S., Hägglöf T., Oliveira T.Y., Viant C., Hurley A., Hoffmann H.H., Millard K.G., Kost R.G., Cipolla M., Gordon K., Bianchini F., Chen S.T., Ramos V., Patel R., Dizon J., Shimeliovich I., Mendoza P., Hartweger H., Nogueira L., Pack M., Horowitz J., Schmidt F., Weisblum Y., Michailidis E., Ashbrook A.W., Waltari E., Pak J.E., Huey-Tubman K.E., Koranda N., Hoffman P.R., West AP J.r., Rice C.M., Hatziioannou T., Bjorkman P.J., Bieniasz P.D., Caskey M, & Nussenzweig M.C. (2020). Convergent Antibody Responses to SARS-CoV-2 in Convalescent Individuals. Nature, 584(7821), 437-442.