The endogenous cellular protease inhibitor SPINT2 controls SARS-CoV-2 viral infection and is associated to disease severity

PLoS Pathog. 2021 Jun 28;17(6):e1009687. doi: 10.1371/journal.ppat.1009687. eCollection 2021 Jun.


COVID-19 outbreak is the biggest threat to human health in recent history. Currently, there are over 1.5 million related deaths and 75 million people infected around the world (as of 22/12/2020). The identification of virulence factors which determine disease susceptibility and severity in different cell types remains an essential challenge. The serine protease TMPRSS2 has been shown to be important for S protein priming and viral entry, however, little is known about its regulation. SPINT2 is a member of the family of Kunitz type serine protease inhibitors and has been shown to inhibit TMPRSS2. Here, we explored the existence of a co-regulation between SPINT2/TMPRSS2 and found a tightly regulated protease/inhibitor expression balance across tissues. We found that SPINT2 negatively correlates with SARS-CoV-2 expression in Calu-3 and Caco-2 cell lines and was down-regulated in secretory cells from COVID-19 patients. We validated our findings using Calu-3 cell lines and observed a strong increase in viral load after SPINT2 knockdown, while overexpression lead to a drastic reduction of the viral load. Additionally, we evaluated the expression of SPINT2 in datasets from comorbid diseases using bulk and scRNA-seq data. We observed its down-regulation in colon, kidney and liver tumors as well as in alpha pancreatic islets cells from diabetes Type 2 patients, which could have implications for the observed comorbidities in COVID-19 patients suffering from chronic diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • COVID-19 / genetics
  • COVID-19 / metabolism*
  • Caco-2 Cells
  • Humans
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • SARS-CoV-2 / genetics
  • SARS-CoV-2 / metabolism*
  • Serine Endopeptidases / genetics
  • Serine Endopeptidases / metabolism
  • Severity of Illness Index
  • Virus Internalization*


  • Membrane Glycoproteins
  • SPINT2 protein, human
  • Serine Endopeptidases
  • TMPRSS2 protein, human

Grant support

This work was supported by grants from the Deutsche Forschungsgemeinschaft (DFG) project numbers 415089553 (Heisenberg program), 240245660 (SFB1129), and 278001972 (TRR186) to SB, and project 416072091 to MS. SB also receveived support from the state of Baden Wuerttemberg (AZ: 33.7533.-6-21/5/1), the Bundesministerium Bildung und Forschung (BMBF) (01KI20198A) and the German Federal Ministry of Education and Research, Network University Medicine - Organo-Strat COVID-19. We also acknowledge funding from the Helmholtz International Graduate School for Cancer Research to CK. CRA, SB, CH acknowledge funding through the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – project number 272983813 (TRR 179). SB and CH acknowledge funding through the DFG program “Identification of the molecular origins of comorbidity in COVID-19 patients” (Project-ID 458633366). This study was partly supported by the Deutsche Forschungsgemeinschaft (DFG; German Research Foundation): SFB1403-414786233 (F.I.S.), TRR237-369799452 (F.I.S.), and the Emmy Noether Programme 322568668 (F.I.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.