RAGE engagement by SARS-CoV-2 enables monocyte infection and underlies COVID-19 severity

The spread of SARS-CoV-2 has fueled the COVID-19 pandemic with its enduring medical and socioeconomic challenges due to subsequent waves and long-term consequences of great concern. Here we charted the molecular basis of COVID-19 pathogenesis, by analysing patients immune response at single-cell resolution across disease course and severity. This approach uncovered cell subpopulation-specific dysregulation in COVID-19 across disease course and severity and identified a severity-associated activation of the receptor for advanced glycation endproduct (RAGE) pathway in monocytes. In vitro experiments confirmed that monocytes bind the SARS-CoV-2 S1-RBD via RAGE and that RAGE-Spike interactions drive monocyte infection. Our results demonstrate that RAGE is a novel functional receptor of SARS-CoV-2 contributing to COVID-19 severity. One-Sentence SummaryMonocyte SARS-CoV-2 infection via the receptor for advanced glycation endproduct triggers severe COVID-19.

Pentosan polysulfate inhibits attachment and infection by SARS-CoV-2 in vitro: insights into structural requirements for binding.

Two years since the outbreak of the novel coronavirus SARS-CoV-2 pandemic, there remain few clinically effective drugs to complement vaccines. One is the anticoagulant, heparin, which in 2004 was found able to inhibit invasion of SARS CoV (CoV-1) and which has been employed during the current pandemic to prevent thromboembolic complications and moderate potentially damaging inflammation. Heparin has also been shown experimentally to inhibit SARS-CoV-2 attachment and infection in susceptible cells. At high therapeutic doses however, heparin increases the risk of bleeding and prolonged use can cause heparin-induced thrombocytopenia, a serious side-effect. One alternative, with structural similarities to heparin is the plant-derived, semi-synthetic polysaccharide, pentosan polysulfate (PPS). PPS is an established drug for the oral treatment of interstitial cystitis, is well-tolerated and exhibits weaker anticoagulant effects than heparin. In an established Vero cell model, PPS and its fractions of varying molecular weights, inhibited invasion by SARS-CoV-2. Intact PPS and its size-defined fractions were characterized by molecular weight distribution and chemical structure using NMR spectroscopy and LC-MS, then employed to explore the structural basis of interactions with SARS-CoV-2 spike protein receptor-binding domain (S1 RBD) and the inhibition of Vero cell invasion. PPS was as effective as unfractionated heparin, but more effective at inhibiting cell infection than low molecular weight heparin (on a weight/volume basis). Isothermal titration calorimetry and viral plaque-forming assays demonstrated size-dependent binding to S1 RBD and inhibition of Vero cell invasion, suggesting the potential application of PPS as a novel inhibitor of SARS-CoV-2 infection.

Recognition and inhibition of SARS-CoV-2 by humoral innate immunity pattern recognition molecules

The humoral arm of innate immunity includes diverse molecules with antibody-like functions, some of which serve as disease severity biomarkers in COVID-19. The present study was designed to conduct a systematic investigation of the interaction of humoral fluid phase pattern recognition molecules (PRM) with SARS-CoV-2. Out of 10 PRM tested, the long pentraxin PTX3 and Mannose Binding Lectin (MBL) bound the viral Nucleoprotein and Spike, respectively. MBL bound trimeric Spike, including that of variants of concern, in a glycan- dependent way and inhibited SARS-CoV-2 in three in vitro models. Moreover, upon binding to Spike, MBL activated the lectin pathway of complement activation. Genetic polymorphisms at the MBL locus were associated with disease severity. These results suggest that selected humoral fluid phase PRM can play an important role in resistance to, and pathogenesis of, COVID-19, a finding with translational implications.

Rapid Inactivation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) by Tungsten Trioxide-Based (WO3) Photocatalysis

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19), is transmitted person-to-person via respiratory droplets and, likely, via smaller droplet nuclei light enough to remain suspended in the air for hours and contaminate surfaces particularly in indoor conditions. Thus, effective measures are needed to prevent SARS-CoV-2 transmission in indoor environments. In this regard, we have investigated whether a system based on a filter combining Tungsten Trioxide-Based (WO3) photocatalysis and an antiviral fabric treated-copper nanocluster could inactivate SARS-CoV-2. To this purpose, an infectious SARS-CoV-2 suspension was introduced in the upper opening of a closed cylinder containing a WO3 filter and a lightbased system that activates WO3 and the antiviral fabric. From the bottom exit, aliquots of fluid were collected every 10 min (up to 60 min) and tested for their infectivity by means of a viral plaque assay in Vero cells whereas, in parallel, the viral RNA content was measured by quantitative PCR (qPCR). As we have previously shown for SARS-CoV, a 1:1,000 ratio of plaque forming units (PFU) vs. viral RNA copies was observed also for SARS-CoV-2. After 10 min, the infectious viral content was already decreased by 98.2% reaching 100% inactivation after 30 min whereas the SARS-CoV-2 RNA load was decreased of 1.5 log10 after 30 min. Thus, in spite of only a partial decrease of viral RNA, SARS-CoV-2 infectivity was completely abolished by the WO3 photocatalysis system by 30 min. These results support the hypothesis that this system could be exploited to achieve SARS-CoV-2 inactivation in indoor environments.

Vinegar and Its Active Component Acetic Acid Inhibit SARS-CoV-2 Infection In Vitro and Ex Vivo

Effective and economical measures are needed to either prevent or inhibit the replication of SARS-CoV-2, the causative agent of COVID-19, in the upper respiratory tract. As fumigation of vinegar at low concentration (0.34%) ameliorated the symptoms of mild SARS-CoV-2 infection, we tested in vitro the potential antiviral activity of vinegar and of its active component, acetic acid. We here demonstrate that both vinegar and acetic acid indeed strongly inactivate SARS-CoV-2 infectivity in Vero cells. Furthermore, vinegar treatment caused a 90% inhibition of the infectious titer when directly applied to a nasopharyngeal swab transfer medium of a COVID-19 patient. These effects were potentiated if conduced at a temperature of 45 {degrees}C vs. 37 {degrees}C, a condition that is transiently generated in the upper respiratory tract during fumigation. Our findings are consistent and extend the results of studies performed in the early and mid-20th century on the disinfectant capacity of organic acids and can provide an affordable home-made aid to prevent or contain SARS-CoV-2 infection of the upper respiratory tract.

Heparin inhibits cellular invasion by SARS-CoV-2: structural dependence of the interaction of the surface protein (spike) S1 receptor binding domain with heparin.

The dependence of the host on the interaction of hundreds of extracellular proteins with the cell surface glycosaminoglycan heparan sulphate (HS) for the regulation of homeostasis is exploited by many microbial pathogens as a means of adherence and invasion. The closely related polysaccharide heparin, the widely used anticoagulant drug, which is structurally similar to HS and is a common experimental proxy, can be expected to mimic the properties of HS. Heparin prevents infection by a range of viruses if added exogenously, including S-associated coronavirus strain HSR1. Heparin prevents infection by a range of viruses if added exogenously, including S-associated coronavirus strain HSR1. Here, we show that the addition of heparin to Vero cells between 6.25 - 200 g.ml-1, which spans the concentration of heparin in therapeutic use, and inhibits invasion by SARS-CoV-2 at between 44 and 80%. We also demonstrate that heparin binds to the Spike (S1) protein receptor binding domain and induces a conformational change, illustrated by surface plasmon resonance and circular dichroism spectroscopy studies. The structural features of heparin on which this interaction depends were investigated using a library of heparin derivatives and size-defined fragments. Binding is more strongly dependent on the presence of 2-O or 6-O sulphation, and the consequent conformational consequences in the heparin structure, than on N-sulphation. A hexasaccharide is required for conformational changes to be induced in the secondary structure that are comparable to those that arise from heparin binding. Enoxaparin, a low molecular weight clinical anticoagulant, also binds the S1 RBD protein and induces conformational change. These findings have implications for the rapid development of a first-line therapeutic by repurposing heparin as well as for next-generation, tailor-made, GAG-based antiviral agents against SARS-CoV-2 and other members of the Coronaviridae.