TMPRSS2 and viral infectious disease: We were able to focus this study on the early stages of virus infection, when S-mediated events include virus attachment to the host surface and induction of the fusion with cell membrane, by using a VSV virus, pseudotyped with the SARS-CoV-2 Spike protein in place of the VSV-G, to infect cell types expressing both ACE2 and TMPRSS2 [20, 34].