Intranasal treatment with the novel engineered trimeric ACE2 (eT-ACE2) protein fully protected mice from a δ-variant challenge (500 pfu), and the viral load in lung homogenates was lower 4 days post-infection, while the mortality in the control group was 100% within 8 days in the absence of eT-ACE2 treatment. This evidence concerns the gene ACE2 and infection.