To determine whether the neutralizing activity observed in PRNT translated into SARS-CoV-2 protection in vivo, a group of six K18-ACE2 mice (three male and three female) expressing hACE2 were infected with SARS-CoV-2 WT at 1 × 103 PFU and treated with 5 mg/Kg of IgG-A7 24 h post-infection. Here, ACE2 is linked to infection.