Based on these observations, the investigation hypothesized that exposure to one of the two viruses could elicit cross-reactive and potentially neutralizing Abs against the other virus. The investigation therefore investigated the ability of plasma from mice immunized with a stabilized SARS-CoV S to inhibit SARS-CoV-2 S- and SARS-CoV S-mediated entry into target cells. All sera tested completely inhibited transduction of SARS-CoV S-MLV and reduced SARS-CoV-2 S-MLV transduction to ∼10% of control in VeroE6 cells.