PROS1 and COVID-19: In a 3.4Å cryo-EM structure of the SARS-CoV-2 S protein bound to the C105 mAb, we observed an epitope on the RBD that overlapped with the binding site for COV21 Fab(s) and closely resembled the binding of B38, another mAb isolated from a COVID-19 patient (Wu et al., 2020c).