PSMD1 and COVID-19: To screen for a potent immunogen for COVID-19 vaccine development, we designed four constructs of the SARS-CoV-2 spike (S) protein: the S-protein ectodomain with the wild-type sequence (S-WT), a previously described trimer stabilization design (S-2P) [29], the S1 subunit, and the RBD fragment.