Fig. 2

In vivo transplantation of transgenic mESCs. A–C Five million clonal transgenic B6 luciferase+ mESCs were subcutaneously injected into the dorsal flank of mice (A, scFv-Fc 33-7 FS-mESCs into B6 animals, n = 9; B and C, scFv-Fc and Db-Fc-scFv 33-7 FS-iACT-mESCs into NSG and B6 animals, n = 5 for each group). D–F Flank teratoma growth over the experimental period, measured by calipers. Ganciclovir (GCV) was administered to all mice over the indicated period to stabilize teratomas. Each line represents a single mouse per group. The dashed line indicates the minimum measurable teratoma volume with calipers, while teratomas are still present and palpable. G–I Levels of plasma nBios over time, assessed by anti-human Fc ELISA of the mouse plasma. The solid and dashed lines indicate previously defined minimum serum neutralizing antibody concentrations required to prevent weight loss (212 ng/ml) and reduce viral burden in the lung (851 ng/ml), respectively, in a mouse model of SARS-CoV-2 pathogenesis [56]. Error bars represent SD. J–L Neutralizing activity of mouse plasma over time against SARS-CoV-2 pseudovirus in vitro on human ACE2-overexpressing HEK293T target cells. Half-maximal neutralization (IC₅₀) values were obtained by nonlinear regression and the neutralizing titer values were obtained by taking the reciprocal of the IC₅₀ plasma dilution. The solid and dashed lines indicate previously defined minimum serum neutralizing titers required to prevent weight loss (104) and reduce viral burden in the lung (381), respectively, in a mouse model of SARS-CoV-2 pathogenesis [56]. Error bars represent 95% CI of neutralizing titers