The OM-85 bacterial lysate inhibits SARS-CoV-2 infection of epithelial cells by downregulating SARS-CoV-2 receptor expression

Vadim Pivniouk, Oksana Pivniouk, Avery DeVries, Jennifer L. Uhrlaub, Ashley Michael, Denis Pivniouk, Sydney R. VanLinden, Michelle Y. Conway, Seongmin Hahn, Sean P. Malone, Peace Ezeh, Jared M. Churko, Dayna Anderson, Monica Kraft, Janko Nikolich-Zugich, Donata Vercelli

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Background: Treatments for coronavirus disease 2019, which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), are urgently needed but remain limited. SARS-CoV-2 infects cells through interactions of its spike (S) protein with angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) on host cells. Multiple cells and organs are targeted, particularly airway epithelial cells. OM-85, a standardized lysate of human airway bacteria with strong immunomodulating properties and an impeccable safety profile, is widely used to prevent recurrent respiratory infections. We found that airway OM-85 administration inhibits Ace2 and Tmprss2 transcription in the mouse lung, suggesting that OM-85 might hinder SARS-CoV-2/host cell interactions. Objectives: We sought to investigate whether and how OM-85 treatment protects nonhuman primate and human epithelial cells against SARS-CoV-2. Methods: ACE2 and TMPRSS2 mRNA and protein expression, cell binding of SARS-CoV-2 S1 protein, cell entry of SARS-CoV-2 S protein–pseudotyped lentiviral particles, and SARS-CoV-2 cell infection were measured in kidney, lung, and intestinal epithelial cell lines, primary human bronchial epithelial cells, and ACE2-transfected HEK293T cells treated with OM-85 in vitro. Results: OM-85 significantly downregulated ACE2 and TMPRSS2 transcription and surface ACE2 protein expression in epithelial cell lines and primary bronchial epithelial cells. OM-85 also strongly inhibited SARS-CoV-2 S1 protein binding to, SARS-CoV-2 S protein–pseudotyped lentivirus entry into, and SARS-CoV-2 infection of epithelial cells. These effects of OM-85 appeared to depend on SARS-CoV-2 receptor downregulation. Conclusions: OM-85 inhibits SARS-CoV-2 epithelial cell infection in vitro by downregulating SARS-CoV-2 receptor expression. Further studies are warranted to assess whether OM-85 may prevent and/or reduce the severity of coronavirus disease 2019.

Original languageEnglish (US)
Pages (from-to)923-933.e6
JournalJournal of Allergy and Clinical Immunology
Issue number3
StatePublished - Mar 2022


  • ACE2
  • COVID-19
  • OM-85
  • SARS-CoV-2
  • bacterial lysate
  • epithelial cells

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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