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
  • 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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