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1.
Nature Reviews Microbiology ; 11:11, 2023.
Article in English | MEDLINE | ID: covidwho-2185915

ABSTRACT

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has been associated with substantial global morbidity and mortality. Despite a tropism that is largely confined to the airways, COVID-19 is associated with multiorgan dysfunction and long-term cognitive pathologies. A major driver of this biology stems from the combined effects of virus-mediated interference with the host antiviral defences in infected cells and the sensing of pathogen-associated material by bystander cells. Such a dynamic results in delayed induction of type I and III interferons (IFN-I and IFN-III) at the site of infection, but systemic IFN-I and IFN-III priming in distal organs and barrier epithelial surfaces, respectively. In this Review, we examine the relationship between SARS-CoV-2 biology and the cellular response to infection, detailing how antagonism and dysregulation of host innate immune defences contribute to disease severity of COVID-19.

2.
ACS Bio & Med chem Au ; 2(6):627-641, 2022.
Article in English | MEDLINE | ID: covidwho-2185502

ABSTRACT

The SARS-CoV-2 pandemic is an ongoing threat to global health, and the continuing emergence of contagious variants highlights the urgent need for additional antiviral therapy to attenuate COVID-19 disease. The SARS-CoV-2 main protease (3CLpro) presents an attractive target for such therapy due to its high sequence conservation and key role in the viral life cycle. In this study, we designed a fluorescent-luminescent cell-based reporter for the detection and quantification of 3CLpro intracellular activity. Employing this platform, we examined the efficiency of known protease inhibitors against 3CLpro and further identified potent inhibitors through high-throughput chemical screening. Computational analysis confirmed a direct interaction of the lead compounds with the protease catalytic site and identified a prototype for efficient allosteric inhibition. These developments address a pressing need for a convenient sensor and specific targets for both virus detection and rapid discovery of potential inhibitors.

3.
Chemical Senses ; 46, 2021.
Article in English | EMBASE | ID: covidwho-1665930

ABSTRACT

Olfaction is a closely coordinated partnership between odorant flow and neuronal signaling. Disruption in our ability to detect odors, or anosmia, has emerged as a hallmark symptom of infection with SARS-CoV-2, and yet, decoding the mechanism behind this abrupt sensory deficit remains elusive. Patients with COVID-19 lack symptoms of nasal congestion and rhinorrhea present in many upper respiratory tract infections that result in a conductive reduction in an ability to perceive smells. To investigate the molecular underpinnings of SARS-CoV-2 related smell loss, we performed molecular analysis, including scRNAseq, RNA-FISH, and Hi-C on both human and syrian golden hamster olfactory epithelium. Here, we report that smell loss may be attributable to non-cell autonomous mechanisms that induce genomic compartment dysregulation and subsequent downregulation of critical signaling pathways responsible for production of olfactory receptors.

5.
Blood ; 138:1, 2021.
Article in English | EMBASE | ID: covidwho-1582278

ABSTRACT

Severe SARS-CoV-2 infection is complicated by dysregulation of the blood coagulation system and high rates of thrombosis, but virus-intrinsic mechanisms underlying this phenomenon are poorly understood. Increased intracellular calcium concentrations promote externalization of phosphatidylserine (PS), the membrane anionic phospholipid required for assembly and activation of the tenase and prothrombinase complexes to drive blood coagulation. TMEM16F is a ubiquitous phospholipid scramblase that mediates externalization of PS in a calcium-dependent manner. As SARS-CoV-2 ORF3a encodes a presumed cation channel with the ability to transport calcium, we hypothesized that ORF3a expression by infected host cells perturbs the cellular calcium rheostat, driving TMEM16F-dependent externalization of PS and enhancing procoagulant activity. Using a doxycycline-inducible system, synchronized expression of ORF3a in A549 pulmonary epithelial cells resulted in a time-dependent augmentation of tissue factor (TF) procoagulant activity exceeding 9-fold by 48 hours (p < 0.0001), with no change in TF cell-surface expression. This enhancement was dependent upon PS as determined by inhibition with the PS-binding protein lactadherin. Over 2-fold enhancement of prothrombinase activity (p < 0.0001) was also observed by 48 hours. ORF3a increased intracellular calcium levels by 18-fold at 48 hours (p < 0.0001), as determined by the intracellular calcium indicator fluo-4. After 16 hours of ORF3a expression, more than 60% of cells had externalized PS (p < 0.001) without increased cell death, as quantified by flow cytometry following annexin V binding. Immunofluorescence microscopy staining for ORF3a, annexin V, and nuclei confirmed ORF3a expression within internal and cell surface membranes and increased PS externalization. PS externalization was insensitive to the pan-caspase inhibitor z-VAD-FMK, and there was no evidence of apoptotic activation as determined by caspase-3 cleavage. By contrast, ORF3a expression did not augment coagulation in cells deficient in the calcium-dependent phospholipid scramblase TMEM16F. Similarly, ORF3a-enhanced TF procoagulant activity (p < 0.01) and prothrombinase activity (p<0.05) was completely abrogated using TMEM16 inhibitors, including the uricosuric agent benzbromarone that has been registered for human use in over 20 countries. Live SARS-CoV-2 infection of A549-ACE2 cells increased cell surface factor Xa generation at MOI 0.1 (p < 0.01) but not MOI 0.01 or following heat inactivation of the virus, and RNA sequencing confirmed ORF3a induction without increased F3 expression. RNA sequencing of human SARS-CoV-2 infected lung autopsy and control tissue (n= 53) confirmed these findings in vivo. Immunofluorescence staining for ORF3a and KRT8/18 and CD31 in SARS-CoV-2 infected human lung autopsy specimens demonstrated ORF3a expression in pulmonary epithelium and endothelial cells, highlighting the potential pathologic relevance of this mechanism. Here we demonstrate that expression of the SARS-CoV-2 accessory protein ORF3a increases the intracellular calcium concentration and TMEM16F-dependent PS scrambling to augment procoagulant activity of the tenase and prothrombinase complexes. Our studies of human cells and tissues infected with SARS-CoV-2 support the pathologic relevance of this mechanism. We highlight the therapeutic potential to target the ORF3a-TMEM16F axis as with benzbromarone to mitigate dysregulation of coagulation and thrombosis during severe SARS-CoV-2 infection. Disclosures: Schwartz: Miromatrix Inc: Membership on an entity's Board of Directors or advisory committees;Alnylam Inc.: Consultancy, Speakers Bureau. Schulman: CSL Behring: Consultancy, Research Funding.

6.
Hepatology ; 72(1 SUPPL):278A, 2020.
Article in English | EMBASE | ID: covidwho-986075

ABSTRACT

Background: COVID-19 was declared a pandemic by the World Health Organization, caused by severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) Respiratory failure is the most common mortality outcome in COVID-19 patients, yet serious and even fatal manifestations are seen across multiple organ systems Emerging clinical data from our own hospital revealed a high prevalence of initial presentations with GI manifestations Almost one third of patients presenting to our hospital reported at least one gastrointestinal manifestation including nausea, vomiting, diarrhea, or abdominal pain 62% of patients presented with biochemical evidence of liver injury Moreover, the presence of liver injury on presentation was associated with a significantly higher risk of ICU admission and death As this is a new and novel clinical entity, robust in vitro models that phenocopy SARS-CoV-2 infection and human COVID-19 disease are limited Current in vitro (e g Vero cells) and in vivo models (mouse models engineered with ACE2) are so distinct from human infection that they may not capture key components of viral infection or virus-host interactions Therefore, the development of robust human models of COVID-19 infection will be essential for the study of SARS-Cov-2 viral infection and to identify robust SARS-CoV-2 therapeutics Methods: Human pluripotent stem cells (hPSCs), including human embryonic stem cells hESCs) and induced pluripotent stem cells (hiPSCs), can be used to derive functional human cells/tissues/organoids for modeling human disease and drug discovery, including for infectious diseases Here we leveraged several stem cell platforms (e g endodermal lineages including hepatocyte and cholangiocyte) along with primary human hepatocytes and cholangiocyte organoid systems to study SARS-CoV-2 infection SARS-CoV-2 pseudoparticles were used to study SARS-CoV-2 viral entry SARS-CoV-2 (USA-WA1/2020) was used to validate viral infection and to study cellular response Autopsy liver samples from COVID-19 patients were obtained and compared to SARS-CoV-2 infected liver models Results: Adult hepatocyte and cholangiocyte organoids along with PSC derived hepatocytes and cholangiocytes are Permissive to SARS-CoV-2 virus infection and show similar transcriptome changes and chemokine responses for SARSCoV- 2 infection as seen in autopsy samples from COVID-19 Patients Conclusion: We report here the development of robust models of SARS-CoV-2 infection in primary and PSC derived hepatocyte and cholangiocytes which phenocopy COVID-19 hepatic disease These disease-relevant human cell/organoid-based platforms can be directly applied for drug screening and the evaluation of prospective antiviral therapeutics as well be used to delineate molecular mechanisms underlying COVID-19 disease.

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