Authors Markus Hoffmann, Hannah Kleine-Weber, Simon Schroeder, ..., Marcel A. Mu¨ ller, Christian Drosten, Stefan Po¨ hlmann Correspondence email@example.com (M.H.), firstname.lastname@example.org (S.P.)
The importance of this Research, It might help to establish options for prevention and treatment from COVID-19.
SARS-CoV-2 uses the SARS-CoV receptor ACE2 for host cell entry
The spike protein of SARS-CoV-2 is primed by TMPRSS2
Antibodies against SARS-CoV spike may offer some protection against SARS-CoV-2
The emerging SARS-coronavirus 2 (SARS-CoV-2) threatens public health. Hoffmann and coworkers show that SARS-CoV-2 infection depends on the host cell factors ACE2 and TMPRSS2 and can be blocked by a clinically proven protease inhibitor.
SARS-CoV-2 uses the SARS-CoV receptor ACE2 for entry and the serine protease TMPRSS2 for S protein priming. A TMPRSS2 inhibitor approved for clinical use blocked entry and might constitute a treatment option. Finally, we show that the sera from convalescent SARS patients cross-neutralized SARS-2- S-driven entry. Our results reveal important commonalities between SARS-CoV-2 and SARS-CoV infection and identify a potential target for antiviral intervention.
The present study provides evidence that host cell entry of SARSCoV-2 depends on the SARS-CoV receptor ACE2 and can beblocked by a clinically proven inhibitor of the cellular serine proteaseTMPRSS2, which is employed by SARS-CoV-2 for S proteinpriming. Moreover, it suggests that antibody responses raisedagainst SARS-CoV could at least partially protect against SARSCoV-2 infection. These results have important implications forour understanding of SARS-CoV-2 transmissibility and pathogenesisand reveal a target for therapeutic intervention.The finding that SARS-2-S exploits ACE2 for entry, which wasalso reported by Zhou and colleagues (Zhou et al., 2020) whilethe present manuscript was in revision, suggests that the virusmight target a similar spectrum of cells as SARS-CoV. In thelung, SARS-CoV infects mainly pneumocytes and macrophages(Shieh et al., 2005). However, ACE2 expression is not limited tothe lung, and extrapulmonary spread of SARS-CoV in ACE2+ tissueswas observed (Ding et al., 2004; Gu et al., 2005; Hamminget al., 2004). The same can be expected for SARS-CoV-2,although affinity of SARS-S and SARS-2-S for ACE2 remains to be compared. It has been suggested that the modest ACE2expression in the upper respiratory tract (Bertram et al., 2012;Hamming et al., 2004) might limit SARS-CoV transmissibility.In light of the potentially increased transmissibility of SARSCoV-2 relative to SARS-CoV, one may speculate that the new virusmight exploit cellular attachment-promoting factors withhigher efficiency than SARS-CoV to ensure robust infection ofACE2+ cells in the upper respiratory tract. This could comprisebinding to cellular glycans, a function ascribed to the S1 domainof certain coronaviruses (Li et al., 2017; Park et al., 2019). Finally,it should be noted that ACE2 expression protects from lung injuryand is downregulated by SARS-S (Haga et al., 2008; Imai et al.,2005; Kuba et al., 2005), which might promote SARS. It will thusbe interesting to determine whether SARS-CoV-2 also interfereswith ACE2 expression.Priming of coronavirus S proteins by host cell proteases isessential for viral entry into cells and encompasses S proteincleavage at the S1/S2 and the S20 sites. The S1/S2 cleavagesite of SARS-2-S harbors several arginine residues (multibasic),which indicates high cleavability. Indeed, SARS-2-S was efficientlycleaved in cells, and cleaved S protein was incorporatedinto VSV particles. Notably, the cleavage site sequence candetermine the zoonotic potential of coronaviruses (Menacheryet al., 2020; Yang et al., 2014, 2015), and a multibasic cleavagesite was not present in RaTG13, the coronavirus most closelyrelated to SARS-CoV-2. It will thus be interesting to determinewhether the presence of a multibasic cleavage site is requiredfor SARS-CoV-2 entry into human cells and how this cleavagesite was acquired.The S proteins of SARS-CoV can use the endosomal cysteineproteases CatB/L for S protein priming in TMPRSS2 cells (Simmonset al., 2005). However, S protein priming by TMPRSS2 butnot CatB/L is essential for viral entry into primary target cells andfor viral spread in the infected host (Iwata-Yoshikawa et al., 2019;Kawase et al., 2012; Zhou et al., 2015). The present study indicatesthat SARS-CoV-2 spread also depends on TMPRSS2 activity,although we note that SARS-CoV-2 infection of Calu-3 cellswas inhibited but not abrogated by camostat mesylate, likely reflectingresidual S protein priming by CatB/L. One can speculatethat furin-mediated precleavage at the S1/S2 site in infected cellsmight promote subsequent TMPRSS2-dependent entry intotarget cells, as reported for MERS-CoV (Kleine-Weber et al.,2018; Park et al., 2016). Collectively, our present findings andprevious work highlight TMPRSS2 as a host cell factor that is criticalfor spread of several clinically relevant viruses, including influenzaA viruses and coronaviruses (Gierer et al., 2013; Glowackaet al., 2011; Iwata-Yoshikawa et al., 2019; Kawase et al., 2012;Matsuyama et al., 2010; Shulla et al., 2011; Zhou et al., 2015).In contrast, TMPRSS2 is dispensable for development and homeostasis(Kim et al., 2006) and thus constitutes an attractivedrug target. In this context, it is noteworthy that the serine proteaseinhibitor camostat mesylate, which blocks TMPRSS2 activity(Kawase et al., 2012; Zhou et al., 2015), has been approved inJapan for human use, but for an unrelated indication. This compoundor related ones with potentially increased antiviral activity(Yamamoto et al., 2016) could thus be considered for off-labeltreatment of SARS-CoV-2-infected patients.Convalescent SARS patients exhibit a neutralizing antibodyresponse that can be detected even 24 months after infection(Liu et al., 2006) and that is largely directed against the S protein.Moreover, experimental SARS vaccines, including recombinantS protein (He et al., 2006) and inactivated virus (Lin et al.,2007), induce neutralizing antibody responses. Although confirmationwith infectious virus is pending, our results indicate thatneutralizing antibody responses raised against SARS-S couldoffer some protection against SARS-CoV-2 infection, whichmay have implications for outbreak control.In sum, this study provided key insights into the first step ofSARS-CoV-2 infection, viral entry into cells, and defined potentialtargets for antiviral intervention.
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Hoffmann et al., 2020, Cell 181, 1–10 April 16, 2020 ª 2020 Elsevier Inc. https://doi.org/10.1016/j.cell.2020.02.052