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Heliyon
. 2023 Nov 17;9(11):e21893.
doi: 10.1016/j.heliyon.2023.e21893. eCollection 2023 Nov. 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 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
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.
. 2023 Nov 17;9(11):e21893.
doi: 10.1016/j.heliyon.2023.e21893. eCollection 2023 Nov. 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 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
- PMID: 38034686
- PMCID: PMC10686889
- DOI: 10.1016/j.heliyon.2023.e21893
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.