ACE2 and infection: Single intranasal pre-treatment of K18-ACE2 mice with VHH-IgA1.1 one hour prior to challenge resulted in a decrease in the expression of SARS-CoV-2 genes including N-protein (Figure 3D), Nsp14 (Figure 3E) and ORF1 (Figure 3F) in lung tissue collected 48 h post-infection.