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

Sabina Sahanic; Richard Hilbe; Christina Dünser; Piotr Tymoszuk; Judith Löffler-Ragg; Dietmar Rieder; Zlatko Trajanoski; Anne Krogsdam; Egon Demetz; Maria Yurchenko; Christine Fischer; Michael Schirmer; Markus Theurl; Daniela Lener; Jakob Hirsch; Johannes Holfeld; Can Gollmann-Tepeköylü; Carl P Zinner; Alexandar Tzankov; Shen-Ying Zhang; Jean-Laurent Casanova; Wilfried Posch; Doris Wilflingseder; Guenter Weiss; Ivan Tancevski

doi:10.1016/j.heliyon.2023.e21893

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. eCollection 2023 Nov.

Authors

Sabina Sahanic¹, Richard Hilbe¹, Christina Dünser¹, Piotr Tymoszuk¹, Judith Löffler-Ragg¹, Dietmar Rieder², Zlatko Trajanoski², Anne Krogsdam², Egon Demetz¹, Maria Yurchenko^{3

4}, Christine Fischer¹, Michael Schirmer¹, Markus Theurl⁵, Daniela Lener⁵, Jakob Hirsch⁶, Johannes Holfeld⁶, Can Gollmann-Tepeköylü⁶, Carl P Zinner⁷, Alexandar Tzankov⁷, Shen-Ying Zhang^{8

9

10}, Jean-Laurent Casanova^{8

9

10

11}, Wilfried Posch¹², Doris Wilflingseder¹², Guenter Weiss¹, Ivan Tancevski¹

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.

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.

Grants and funding

UM1 AI068618/AI/NIAID NIH HHS/United States