(
B) Schematic representation showing organization of the SARS-CoV and Bat-SCoV Spike proteins. The engineered Spike proteins are pictured below with the virus name to the left. Bat-SRBD includes all of the Bat-SCoV Spike sequence except that the Bat-SCoV RBD (Bat-SCoV amino acid 323–505) is replaced with the SARS-CoV RBD (amino acid 319–518) (GenBank accession no.
FJ211860). Bat-SRBD-MA includes the MA15 Spike RBD change at SARS-CoV aa Y436H. Bat-SRBM includes the minimal 13 SARS-CoV residues critical for ACE2 contact, resulting in a chimeric RBD of Bat-SCoV amino acid 323I-429T and SARS-CoV amino acid 426R-518D. Bat-Hinge is Bat-SRBM sequence, with Bat-SCoV amino acid 392L-397E replaced with SARS-CoV amino acid 388V-393D. Bat-F includes nt 1–24057 of SARS-CoV (to Spike amino acid 855), with the remaining 3? sequence from Bat-SCoV. To the right of the schematic representations, observation of transcript activity and approximate stock titers at passage 1 (P1) are indicated. ND indicates no infectious virus detected by plaque assay.