Fig. 2. Characterization of minimal protein requirements for efficient SARS-CoV-2 VLPs production. Western blot analysis of SARS-CoV-2 S and N proteins in WCLs and in ultracentrifuged supernatants (UCF) 48 h after transfection of the plasmids expressing the indicated proteins. 4SP (“4 structural proteins”) stands for a mixture of S, M, E and N-expressing plasmids.