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  3. SARS-CoV-2 activates the TLR4/MyD88 pathway in human macrophages: A possible correlation with strong pro-inflammatory responses in severe COVID-19

SARS-CoV-2 activates the TLR4/MyD88 pathway in human macrophages: A possible correlation with strong pro-inflammatory responses in severe COVID-19

  • Heliyon. 2023 Nov 17;9(11):e21893. doi: 10.1016/j.heliyon.2023.e21893.
Sabina Sahanic 1,  Richard Hilbe 1,  Christina Dünser 1,  Piotr Tymoszuk 1,  Judith Löffler-Ragg 1,  Dietmar Rieder 2,  Zlatko Trajanoski 2,  Anne Krogsdam 2,  Egon Demetz 1,  Maria Yurchenko 3 4,  Christine Fischer 1,  Michael Schirmer 1,  Markus Theurl 5,  Daniela Lener 5,  Jakob Hirsch 6,  Johannes Holfeld 6,  Can Gollmann-Tepeköylü 6,  Carl P Zinner 7,  Alexandar Tzankov 7,  Shen-Ying Zhang 8 9 10,  Jean-Laurent Casanova 8 9 10 11,  Wilfried Posch 12,  Doris Wilflingseder 12,  Guenter Weiss 1,  Ivan Tancevski 1
Affiliations

Affiliations

  • 1 Department of Internal Medicine II, Medical University of Innsbruck, Innsbruck, Austria.
  • 2 Institute of Bioinformatics, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
  • 3 Centre of Molecular Inflammation Research, Norwegian University of Science and Technology, Trondheim, Norway.
  • 4 The Central Norway Regional Health Authority, St. Olavs Hospital HF, Trondheim, Norway.
  • 5 Department of Internal Medicine III, Medical University of Innsbruck, Innsbruck, Austria.
  • 6 Department of Cardiac Surgery, Medical University of Innsbruck, Innsbruck, Austria.
  • 7 Institute of Medical Genetics and Pathology, University Hospital Basel, Basel, Switzerland.
  • 8 Laboratory of Human Genetics of Infectious Diseases, Necker Branch, INSERM U1163, Necker Hospital for Sick Children, Paris, France.
  • 9 University of Paris, Imagine Institute, Paris, France.
  • 10 St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York, NY, USA.
  • 11 Howard Hughes Medical Institute, New York, NY, 10065, USA.
  • 12 Division of Hygiene and Medical Microbiology, Medical University of Innsbruck, Austria.
PMID: 38034686 DOI: 10.1016/j.heliyon.2023.e21893
Abstract

Background: Toll-like receptors (TLRs) play a pivotal role in the immunologic response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Infection. Exaggerated inflammatory response of innate immune cells, however, may drive morbidity and death in Coronavirus disease 19 (COVID-19).

Objective: We investigated the engagement of SARS-CoV-2 with TLR4 in order to better understand how to tackle hyperinflammation in COVID-19.

Methods: We combined RNA-sequencing data of human lung tissue and of bronchoalveolar lavage fluid cells derived from COVID-19 patients with functional studies in human macrophages using SARS-CoV-2 Spike Proteins and viable SARS-CoV-2. Pharmacological inhibitors as well as gene editing with CRISPR/Cas9 were used to delineate the signalling pathways involved.

Results: We found TLR4 to be the most abundantly upregulated TLR in human lung tissue irrespective of the underlying pathology. Accordingly, bronchoalveolar lavage fluid cells from patients with severe COVID-19 showed an NF-κB-pathway dominated immune response, whereas they were mostly defined by type I interferon signalling in moderate COVID-19. Mechanistically, we found the Spike ectodomain, but not receptor binding domain monomer to induce TLR4-dependent inflammation in human macrophages. By using pharmacological inhibitors as well as CRISPR/Cas9 deleted macrophages, we identify SARS-CoV-2 to engage canonical TLR4-MyD88 signalling. Importantly, we demonstrate that TLR4 blockage prevents exaggerated inflammatory responses in human macrophages infected with different SARS-CoV-2 variants, including immune escape variants B.1.1.7.-E484K and B.1.1.529 (omicron).

Conclusion: Our study critically extends the current knowledge on TLR-mediated hyperinflammatory responses to SARS-CoV-2 in human macrophages, paving the way for novel approaches to tackle severe COVID-19.

Take-home message: Our study combining human lung transcriptomics with functional studies in human macrophages clearly supports the design and development of TLR4 - directed therapeutics to mitigate hyperinflammation in severe COVID-19.

Keywords

COVID-19; Innate immunity; Macrophages; SARS-CoV-2; Toll-like receptors.

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