Fig. 2: S protein is the main component in purified S-VLPs derived from CHO-C2 cells.

a CHO-C2 (ERVLP-KO) cells. On the left, total protein staining (Coomassie blue) showing supernatants (7.5 µL) and sedimented (0.35 µg of total protein) VLPs produced in CHO²³⁵³ (parental) or CHO-C2. On the right, Western blotting of VLPs produced by CHO²³⁵³ or CHO-C2. The upper part of the blot shows the full-length S protein detected by anti-Spike (S1) in clarified harvest or sedimented VLPs. The lower blot is stained with anti-Gag p30 and shows the absence of Gag in CHO-C2-derived VLPs. b Scatter plot of total S protein (mg/L) from different samples at 5 days of transfection. Data are presented as mean ± SEM of six independent samples. c Total protein staining comparison of sedimented and affinity-purified S-VLPs. On the left, 1 µg of recombinant, soluble S protein (S STD) was loaded. For VLPs, 0.7 µg of total protein was loaded per well. d Representative TEM image of affinity-purified S-VLPs. A 200 nm scale bar is shown at the bottom. e Representative high-resolution TEM image of individual affinity-purified S-VLPs acquired with a HITACHI HT7700 120. A 50 nm scale bar is shown at the bottom. f Scatter plot of total S protein (mg/L) from different purified samples at 5 days of transfection. Data are presented as mean ± SEM of four independent samples. g ELISA assay. Dose-response curve of purified S-VLP (starting concentration [S] = 0.081 mg/mL) showing 11 serial dilutions. Red dots represent S-VLPs on a hACE2-coated plate in an S-shaped sigmoidal curve in red. Blue dots represent S-VLPs on an uncoated (mock) plate connected by a blue line.