Figure A1.

Ad26 vectors encoding variants of the SARS-CoV-2 S protein. From top to bottom: (1) full-length S in which furin cleavage site mutations and proline substitutions have been introduced, (2) native full-length S, (3) full-length S with only the proline substitutions, and (4) full-length S in which tissue plasminogen activator signal peptide is added upstream of the wild-type signal peptide. Green bar represents tissue plasminogen activator signal peptide, yellow bars represent wild-type signal peptide, red vertical lines represent furin cleavage site mutations, and blue vertical lines represent proline substitutions.