Fig. 4

Functional validation of engineered MSCs in vitro. (a) The quantification of SARS-CoV-2 mAbs released by a single MSC clone (pg/cell) was performed by ELISA. MSCs were seeded at limiting cell densities and the level of antibody (ng) in culture supernatant (6-well-plates, 12-well-plates, and 24-well-plates) was determined after 96 h of culture (mean ± SD from three wells of one experiment). (b) The levels of SARS-CoV-2 mAbs released by screened positive MSCs clones at different time points (left; changing medium every 4 days without subculturing) and at different passages (right) (mean ± SD from three wells of one experiment). (c) Reducing SDS-PAGE analysis of SARS-CoV-2 mAbs released by MSCs (XGv347-10 and LY-CoV1404-5). Lane 1: Original cell culture supernatant, Lane 2: Supernatant after bind with protein G, Lane 3: Washing liquid, Lane 4: Purified IgG as positive control. *non-reducing SDS-PAGE. (d) Flow cytometry gating of Th1 and Th17 cells. Gates to exclude debris and cell aggregates in FSC-A/SSC-A and FSC-A/FSC-H plots. Representative flow cytometry gating strategy correspond to Th1(IFN-γ–FITC+) and Th17(IL-17 A–PE+). (e) Representative flow cytometry of Th1 and Th17 cells overlaid on total CD3 + T cells. Percentage of Th1 and Th17 cells quantified by expression of IFN-r and lL-17 A, respectively in acute COVID-19 (n = 8). **p < 0.01, ***p < 0.001. (f) Representative flow cytometry of Th1 and Th17 cells overlaid on total CD3 + T cells. Percentage of Th1 and Th17 cells quantified by expression of IFN-r and lL-17 A, respectively in unexposed (n = 8). **p < 0.01, ***p < 0.001