Fig. 1. Construction and characterization of Ad5-S-nb2.
a Schematic diagram of the genome of Ad5-S-nb2 and the coding sequence for SARS-CoV-2 S protein. b Western blot analysis of the expression of S protein in HEK293 cells transfected with plasmids encoding an original S sequence (pGA1-S-nb1, 4 μg per well) or a codon-modified S sequence (pGA1- S-nb2 1#: 4 μg per well; pGA1- S-nb2 2#: 2 μg per well). A pGA1-empty plasmid was used as the negative control. A purified S protein with the transmembrane domain truncated (SΔTM) was used as the positive control. c Western blot analysis of the expression of S protein in HEK293 cells infected with Ad5-S-nb2. Ad5-S-nb2 1#, 0.2 TCID50 per cell; Ad5-S-nb2 2#, 0.05 TCID50 per cell. SΔTM protein and HEK293 cells infected with Ad5-empty were examined in parallel as the positive and negative controls, respectively. The samples were derived from the same experiment and the blots were processed in parallel. d Immunofluorescence analysis of the expression of S protein in A549 cells mediated by Ad5-S-nb2. A549 cells were infected with Ad5-S-nb2 or Ad5-empty at 0.2 TCID50 per cell. Twenty-four hours later, cells were labeled with a human monoclonal antibody against S protein and then with an Alexa Fluor 488-conjugated mouse anti-human antibody. The cells were observed under a fluorescence microscope. Scale bar = 50 μm. For b and c, two independent experiments were carried out with similar results. For d, one representative result from three independent experiments is shown. Source data are provided as a Source Data file.