Fig. 1
From: Cell-based passive immunization for protection against SARS-CoV-2 infection
Development and in vitro characterization of transgenic mESCs. A Architectures of SARS-CoV-2 nBios encoded in human IgG1-based single-chain (sc) constructs. VL, variable light chain; VH, variable heavy chain; CL, constant light chain; CH, constant heavy chain. B The coding sequences of each SARS-CoV-2 nBio format were separately cloned into a piggyBac transposon expression vector. TR, terminal repeat; IRES, internal ribosome entry site; pA, polyadenylation. C Images of transgenic clonal mESCs expressing nBio transgenes linked to mCherry. All scale bars are 65 μm. D Quantification of nBios secreted into the culture supernatant by clonal transgenic mESCs by human anti-Fc ELISA. Each dot represents a separately generated clone expressing the same nBio format, according to its color. Bars represent the mean clonal secretion of nBio formats ± SEM of two independent experiments. The differences between nBio secretion between formats are not significant unless stated. Statistical significance was determined by one-way ANOVA with Tukey’s multiple comparisons test. **P = 0.0037; ***P < 0.0007; ****P < 0.0001. The black asterisks represent statistical significance relative to the Wt mESC control. Wt, wild-type; ND, not detected. E Neutralization of SARS-CoV-2 pseudovirus by mESC-derived nBios on human ACE2-overexpressing HEK293T target cells. Infection inhibition was measured as a function of nBio concentration in the supernatant of the highest expressing mESC clone of each format. Two independent experiments were performed with similar results. Curves were fit by nonlinear regression. Error bars represent SD. F Combined neutralization and secretion properties of each nBio format. The number of mESCs in culture required to reach half-maximal infection inhibition (IC50) by each nBio is plotted as a function of the IC50. The green box indicates the most ideal transgenic mESC line with respect to secretion and nBio potency. *An IC50 value for sACE2-Fc was not obtained due to incomplete neutralization in the assay at the concentrations tested