In order to determine the optimal Ad-ACE2 dose for SARS-CoV-2 replication in vivo, separate groups of BALB/c mice were administered with 2.5×108 (data also shown in Figure 2(D)), 1×108, or 7.5×107 PFU of Ad-ACE2 followed by infection with SARS-CoV-2 at D5 post-Ad transduction. Here, ACE2 is linked to infection.