The SARS‐CoV‐2, GX/P2V/2017, and GD/1/2019 pseudoviruses were constructed with a GFP encoding replication‐deficient vesicular stomatitis virus (VSV) vector backbone (VSV‐ΔG‐GFP) and the coding sequence of corresponding spike proteins, as previously described (Li et al, 2020 (link); Muik et al, 2021 (link)). Briefly, HEK 293T cells were transfected by 30 μg of spike protein expression plasmids. The VSV‐ΔG‐GFP pseudovirus was added 24 h post‐transfection. The inoculum was removed after incubation for 1 h at 37°C. The culture medium was then changed into DMEM supplemented with 10% FBS and 10 μg/ml of anti‐VSV‐G antibody (I1‐Hybridoma ATCC® CRL2700™) after washing cells with PBS. The pseudoviruses were harvested 20 h post‐inoculation, passed through a 0.45‐μm filter (Millipore, Cat#SLHP033RB) before aliquoted, and stored at −80°C.
All pseudoviruses were treated with 0.5 U/μl BaseMuncher Endonuclease (Abcam, ab270049) for 1.5 h at 37°C to remove unpackaged RNA before quantification. Viral RNA was extracted (Bioer Technology, Cat# BYQ6.6.101711‐213) and quantitated by quantitative RT–PCR (qPCR) using 7500 fast real‐time PCR system (Applied Biosystems) with the primers and probe for detecting the P protein coding sequence of VSV.
All pseudoviruses were treated with 0.5 U/μl BaseMuncher Endonuclease (Abcam, ab270049) for 1.5 h at 37°C to remove unpackaged RNA before quantification. Viral RNA was extracted (Bioer Technology, Cat# BYQ6.6.101711‐213) and quantitated by quantitative RT–PCR (qPCR) using 7500 fast real‐time PCR system (Applied Biosystems) with the primers and probe for detecting the P protein coding sequence of VSV.
