Interestingly, although full-length LF was not able to block TMPRSS2 activity (Figure 1A), it prevented infection of Vero cells by ≈38% when used at 40 μg/mL (Figure 3A), and seemed even more potent in Calu-3 cells, where ≈60-70% inhibition was observed (Figure 3B). Here, TMPRSS2 is linked to infection.