DAMPs/PAMPs induce monocytic TLR activation and tolerance in COVID-19 patients; nucleic acid binding scavengers can counteract such TLR agonists

Abstract

Millions of COVID-19 patients have succumbed to respiratory and systemic inflammation. Hyperstimulation of toll-like receptor (TLR) signaling has been shown to be a key driver of immunopathology following infection by viruses. We found that severely ill COVID-19 patients in the Intensive Care Unit (ICU) display hallmarks of such hyper-stimulation with abundant agonists of nucleic acid sensing TLRs present in their blood and lungs. These nucleic acid-containing Damage and Pathogen Associated Molecular Patterns (DAMPs/PAMPs) can be depleted using nucleic acid-binding microfibers to limit the patient samples’ ability to hyperactivate such innate immune receptors. Single-cell RNA-sequencing revealed that CD16 + monocytes from deceased but not recovered ICU patients exhibit a TLR-tolerant phenotype and a deficient anti-viral response after ex vivo TLR stimulation. Plasma proteomics confirmed such myeloid hyperactivation and revealed DAMP/PAMP carrier consumption in deceased patients. Treatment of these COVID-19 patient samples with MnO nanoparticles effectively neutralizes TLR activation by the abundant nucleic acid-containing DAMPs/PAMPs present in their lungs and blood. Finally, MnO nanoscavenger treatment limits the ability of DAMPs/PAMPs to induce TLR tolerance in monocytes. Thus, treatment with microfiber- or nanoparticle-based DAMP/PAMP scavengers may prove useful for limiting SARS-CoV-2 induced hyperinflammation, preventing monocytic TLR tolerance and improving outcomes in severely ill COVID-19 patients.

Differential chromatin accessibility in peripheral blood mononuclear cells underlies COVID-19 disease severity prior to seroconversion

“…5 A. Expression of these pathways is also elevated in monocyte subsets from subjects with more severe disease, including the ICU subjects treated with TLR agonists 16 . Pathways identified centered on those of the adaptive immune response.…”

“…5 F, Supplemental Tables S8 , S9 ). To perform this analysis, scRNA-seq clusters containing CD14+ monocytes from both mild and moderate subjects were merged were appropriate (Supplemental Methods) and two published datasets were incorporated to enable comparison with more severe COVID-19 disease phenotypes 16 , 17 . We identified an enrichment of interferon response activity in the mild and moderate monocytes from Mild 1, Mild 2 and Moderate 1 CD14+ monocyte subsets (scRNA-seq clusters 2, 4 and 7) which was consistent with our bulk RNA-seq data on the same cohorts.…”

The multifaceted roles of NLRP3-modulating proteins in virus infection

“…This frontline defense is achieved using immune sentinels, or pattern recognition receptors (PRRs), that recognize exogenous pattern-associated molecular patterns (PAMPs) and endogenous damage-associated molecular patterns (DAMPs). In the case of viral infection, PAMPs may be associated with the viral particle, such as the SARS-CoV-2 spike protein which induces inflammation via the C-type lectin receptors ( 14 ) or toll-like receptor (TLR) 2 ( 15 ), or intermediates of viral replication, such as SARS-CoV-2 double-stranded RNA which activates the retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) or TLRs ( 16 , 17 ) ( Figure 1 ). Virus-induced cell lysis can also lead to the release of host products or DAMPs, that similarly initiate innate immune responses.…”

mRNA expression of toll-like receptors 3, 7, 8, and 9 in the nasopharyngeal epithelial cells of coronavirus disease 2019 patients

“…Studies show that COVID-19 patients with severe form of disease hospitalized in the ICU show hallmarks of hyperactivation of TLRs with increased levels of agonists of nucleic acid-sensing TLRs found in the blood and lungs samples. Using nanoparticle- or microfiber-based approaches for Damage associated molecular pattern (DAMP)/PAMP scavenging might be beneficial in confining SARS-CoV-2-stimulated hyperinflammation and improving the outcomes in the COVID-19 patients with higher disease severity [ 31 ].…”