ACE2 and infection: As compared to uninfected ACE2.Tg mice, uninfected ACE2.Tg mice cohoused with SARS-CoV-2-infected ACE2.Tg mice develop infection while uninfected ACE2.Tg mice cohoused with SARS-CoV-2-infected Foxo1fl/fl.CD4Cre+ mice develop low level of infection as indicated by weight loss, lung lesions, viral load and histological score (Fig. 5b–f).