Distinct SARS-CoV-2 RNA fragments activate Toll-like receptors 7 and 8 and induce cytokine release from human macrophages and microglia

Thomas Wallach; Martin Raden; Lukas Hinkelmann; Mariam Brehm; Dominik Rabsch; Hannah Weidling; Christina Krüger; Helmut Kettenmann; Rolf Backofen; Seija Lehnardt

doi:10.3389/fimmu.2022.1066456

Distinct SARS-CoV-2 RNA fragments activate Toll-like receptors 7 and 8 and induce cytokine release from human macrophages and microglia

Front Immunol. 2023 Jan 13:13:1066456. doi: 10.3389/fimmu.2022.1066456. eCollection 2022.

Authors

Thomas Wallach¹, Martin Raden², Lukas Hinkelmann¹, Mariam Brehm¹, Dominik Rabsch², Hannah Weidling^{1

3}, Christina Krüger¹, Helmut Kettenmann³, Rolf Backofen^{2

4}, Seija Lehnardt^{1

5}

Affiliations

¹ Institute of Cell Biology and Neurobiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.
² Bioinformatics, Department of Computer Science, Albert-Ludwigs-University Freiburg, Freiburg, Germany.
³ Cellular Neuroscience, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.
⁴ Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.
⁵ Department of Neurology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.

Abstract

Introduction: The pandemic coronavirus disease 19 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is marked by thromboembolic events and an inflammatory response throughout the body, including the brain.

Methods: Employing the machine learning approach BrainDead we systematically screened for SARS-CoV-2 genome-derived single-stranded (ss) RNA fragments with high potential to activate the viral RNA-sensing innate immune receptors Toll-like receptor (TLR)7 and/or TLR8. Analyzing HEK TLR7/8 reporter cells we tested such RNA fragments with respect to their potential to induce activation of human TLR7 and TLR8 and to activate human macrophages, as well as iPSC-derived human microglia, the resident immune cells in the brain.

Results: We experimentally validated several sequence-specific RNA fragment candidates out of the SARS-CoV-2 RNA fragments predicted in silico as activators of human TLR7 and TLR8. Moreover, these SARS-CoV-2 ssRNAs induced cytokine release from human macrophages and iPSC-derived human microglia in a sequence- and species-specific fashion.

Discussion: Our findings determine TLR7 and TLR8 as key sensors of SARS-CoV-2-derived ssRNAs and may deepen our understanding of the mechanisms how this virus triggers, but also modulates an inflammatory response through innate immune signaling.

Keywords: RNA; SARS-CoV-2; iPSC-derived human microglia; inflammatory response; macrophages; toll-like receptors.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

COVID-19*
Cytokines*
Humans
Macrophages
Microglia
RNA, Viral
SARS-CoV-2 / genetics
Toll-Like Receptor 7
Toll-Like Receptor 8

Substances

Cytokines
RNA, Viral
Toll-Like Receptor 7
Toll-Like Receptor 8

Grants and funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG, SFB-TRR 167/B03 and LE 2420/2-1 to SL; BA 2168/11-1 SPP 1738, BA2168/11-2 SPP 1738, and SFB 1425/1 to RB). DR was supported by the Bundesministerium für Bildung und Forschung (BMBF, RNAProNet-031L0164B). MB received a scholarship from the Sonnenfeld-Stiftung, while LH was supported by a scholarship from the German Academic Scholarship Foundation (Studienstiftung des deutschen Volkes).