TMPRSS2 and infection: To address this question (Figure 4), we used the ‘virus-washed’ in vitro assay to compare IFNβ-ACE2 to the unlinked combination of equimolar sACE2(18-611) and IFN-β, with nucleocapsid expression (Figure 4A,B) coupled with ACE2 and TMPRSS2 downregulation (Figure 4C–E and 4F–H, respectively) as measures of infection.