Abstract The protease TMPRSS2 facilitates coronavirus infections, yet its mechanism of viral glycoprotein recognition remains unclear. Here we show that, following ACE2 engagement of the SARS-CoV-2 spike (S) inducing the early fusion intermediate conformation (E-FIC), TMPRSS2 cleaves the R815 S 2 ′ site and promotes fusogenic conformational changes leading to viral entry. We unveil TMPRSS2 recognition of S 2 ′, identify key residues modulating binding specificity and demonstrate that S 2 ′ site-directed broadly neutralizing antibodies target E-FIC and inhibit viral entry by blocking TMPRSS2 access. We computationally designed stabilized E-FIC as a vaccine candidate, overcoming the transient nature of this state. We describe a TMPRSS2-directed monoclonal antibody inhibiting several coronaviruses, including SARS-CoV-2 variants and protecting mice against SARS-CoV-2 challenge. These results outline the mechanistic role of TMPRSS2 and S 2 ′ site-directed antibodies in coronavirus entry.
McCallum et al. (Tue,) studied this question.