Frontiers in Immunology (Jan 2023)

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,
  • Hannah Weidling,
  • Christina Krüger,
  • Helmut Kettenmann,
  • Rolf Backofen,
  • Rolf Backofen,
  • Seija Lehnardt,
  • Seija Lehnardt

DOI
https://doi.org/10.3389/fimmu.2022.1066456
Journal volume & issue
Vol. 13

Abstract

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IntroductionThe 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 brainMethodsEmploying 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.ResultsWe 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.DiscussionOur 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.

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