Fig. 1: S expression in CHO cells is sufficient to generate S-coated SARS-CoV-2 VLPs.

a Sedimented supernatants with 15% iodixanol cushion from CHO²³⁵³ cells transfected with S or M-E/S plasmids. On the left, total protein staining (Coomassie blue) of S or M-E/S. On the right, immunoblot with anti-Spike (S1) detecting S (~180 kDa). The SARS-CoV-2 membrane (M) protein is detected with anti-M at ~17 kDa. b Representative TEM image of sedimented M-E/S VLPs. White arrows indicate potential VLPs. A scale bar of 100 nm is shown at the bottom of the image. c Representative TEM image of sedimented VLPs generated by the expression of S protein (S-VLPs). A scale bar of 200 nm is shown at the bottom of the image. White arrows indicate VLPs. d Representative immunoblot of different S-VLPs variants detected with anti-S1. From left to right, mock, beta (B.1.351), delta (B.1.617.2), and omicron (B.1.1.529) S-VLPs. e Representative TEM images of sedimented S-VLPs variants. From left to right, beta (B.1.351), delta (B.1.617.2), and omicron (B.1.1.529). A 50 nm scale bar is shown at the bottom of each image.