A high-throughput screen for TMPRSS2 expression identifies FDA-approved compounds that can limit SARS-CoV-2 entry

Sarbecovirus disease susceptibility is conserved across viral and host models

Coronaviruses have caused three severe epidemics since the start of the 21st century: SARS, MERS and COVID-19. The severity of the ongoing COVID-19 pandemic and increasing likelihood of future coronavirus outbreaks motivates greater understanding of factors leading to severe coronavirus disease. We screened ten strains from the Collaborative Cross mouse genetic reference panel and identified strains CC006/TauUnc (CC006) and CC044/Unc (CC044) as coronavirus-susceptible and resistant, respectively, as indicated by variable weight loss and lung congestion scores four days post-infection. We generated a genetic mapping population of 755 CC006xCC044 F2 mice and exposed the mice to one of three genetically distinct mouse-adapted coronaviruses: clade 1a SARS-CoV MA15 (n=391), clade 1b SARS-CoV-2 MA10 (n=274), and clade 2 HKU3-CoV MA (n=90). Quantitative trait loci (QTL) mapping in SARS-CoV MA15- and SARS-CoV-2 MA10-infected F2 mice identified genetic loci associated with disease severity. Specifically, we identified seven loci associated with variation in outcome following infection with either virus, including one, HrS43, that is present in both groups. Three of these QTL, including HrS43, were also associated with HKU3-CoV MA outcome. HrS43 overlaps with a QTL previously reported by our lab that is associated with SARS-CoV MA15 outcome in CC011xCC074 F2 mice and is also syntenic with a human chromosomal region associated with severe COVID-19 outcomes in humans GWAS. The results reported here provide: (a) additional support for the involvement of this locus in SARS-CoV MA15 infection, (b) the first conclusive evidence that this locus is associated with susceptibility across the Sarbecovirus subgenus, and (c) demonstration of the relevance of mouse models in the study of coronavirus disease susceptibility in humans.

Structure-guided conversion from an anaplastic lymphoma kinase inhibitor into Plasmodium lysyl-tRNA synthetase selective inhibitors

Aminoacyl-tRNA synthetases (aaRSs) play a central role in the translation of genetic code, serving as attractive drug targets. Within this family, the lysyl-tRNA synthetase (LysRS) constitutes a promising antimalarial target. ASP3026, an anaplastic lymphoma kinase (ALK) inhibitor was recently identified as a novel Plasmodium falciparum LysRS (PfLysRS) inhibitor. Here, based on cocrystal structures and biochemical experiments, we developed a series of ASP3026 analogues to improve the selectivity and potency of LysRS inhibition. The leading compound 36 showed a dissociation constant of 15.9 nM with PfLysRS. The inhibitory efficacy on PfLysRS and parasites has been enhanced. Covalent attachment of L-lysine to compound 36 resulted in compound 36K3, which exhibited further increased inhibitory activity against PfLysRS but significantly decreased activity against ALK. However, its inhibitory activity against parasites did not improve, suggesting potential future optimization directions. This study presents a new example of derivatization of kinase inhibitors repurposed to inhibit aaRS.

TMPRSS2-mediated SARS-CoV-2 uptake boosts innate immune activation, enhances cytopathology, and drives convergent virus evolution

The accessory protease transmembrane protease serine 2 (TMPRSS2) enhances severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uptake into ACE2-expressing cells, although how increased entry impacts downstream viral and host processes remains unclear. To investigate this in more detail, we performed infection assays in engineered cells promoting ACE2-mediated entry with and without TMPRSS2 coexpression. Electron microscopy and inhibitor experiments indicated TMPRSS2-mediated cell entry was associated with increased virion internalization into endosomes, and partially dependent upon clathrin-mediated endocytosis. TMPRSS2 increased panvariant uptake efficiency and enhanced early rates of virus replication, transcription, and secretion, with variant-specific profiles observed. On the host side, transcriptional profiling confirmed the magnitude of infection-induced antiviral and proinflammatory responses were linked to uptake efficiency, with TMPRSS2-assisted entry boosting early antiviral responses. In addition, TMPRSS2-enhanced infections increased rates of cytopathology, apoptosis, and necrosis and modulated virus secretion kinetics in a variant-specific manner. On the virus side, convergent signatures of cell-uptake-dependent innate immune induction were recorded in viral genomes, manifesting as switches in dominant coupled Nsp3 residues whose frequencies were correlated to the magnitude of the cellular response to infection. Experimentally, we demonstrated that selected Nsp3 mutations conferred enhanced interferon antagonism. More broadly, we show that TMPRSS2 orthologues from evolutionarily diverse mammals facilitate panvariant enhancement of cell uptake. In summary, our study uncovers previously unreported associations, linking cell entry efficiency to innate immune activation kinetics, cell death rates, virus secretion dynamics, and convergent selection of viral mutations. These data expand our understanding of TMPRSS2's role in the SARS-CoV-2 life cycle and confirm its broader significance in zoonotic reservoirs and animal models.

FDA-Approved Tedizolid Phosphate Prevents Cisplatin-Induced Hearing Loss Without Decreasing Its Anti-tumor Effect

PURPOSE

Cisplatin is a low-cost clinical anti-tumor drug widely used to treat solid tumors. However, its use could damage cochlear hair cells, leading to irreversible hearing loss. Currently, there appears one drug approved in clinic only used for reducing ototoxicity associated with cisplatin in pediatric patients, which needs to further explore other candidate drugs.

METHODS

Here, by screening 1967 FDA-approved drugs to protect cochlear hair cell line (HEI-OC1) from cisplatin damage, we found that Tedizolid Phosphate (Ted), a drug indicated for the treatment of acute infections, had the best protective effect. Further, we evaluated the protective effect of Ted against ototoxicity in mouse cochlear explants, zebrafish, and adult mice. The mechanism of action of Ted was further explored using RNA sequencing analysis and verified. Meanwhile, we also observed the effect of Ted on the anti-tumor effect of cisplatin.

RESULTS

Ted had a strong protective effect on hair cell (HC) loss induced by cisplatin in zebrafish and mouse cochlear explants. In addition, when administered systemically, it protected mice from cisplatin-induced hearing loss. Moreover, antitumor studies showed that Ted had no effect on the antitumor activity of cisplatin both in vitro and in vivo. RNA sequencing analysis showed that the otoprotective effect of Ted was mainly achieved by inhibiting phosphorylation of ERK. Consistently, ERK activator aggravated the damage of cisplatin to HCs.

CONCLUSION

Collectively, these results showed that FDA-approved Ted protected HCs from cisplatin-induced HC loss by inhibiting ERK phosphorylation, indicating its potential as a candidate for preventing cisplatin ototoxicity in clinical settings.

An evolutionarily conserved ubiquitin ligase drives infection and transmission of flaviviruses

Mosquito-borne flaviviruses such as dengue (DENV) and Zika (ZIKV) cause hundreds of millions of infections annually. The single-stranded RNA genome of flaviviruses is translated into a polyprotein, which is cleaved equally into individual functional proteins. While structural proteins are packaged into progeny virions and released, most of the nonstructural proteins remain intracellular and could become cytotoxic if accumulated over time. However, the mechanism by which nonstructural proteins are maintained at the levels optimal for cellular fitness and viral replication remains unknown. Here, we identified that the ubiquitin E3 ligase HRD1 is essential for flaviviruses infections in both mammalian hosts and mosquitoes. HRD1 directly interacts with flavivirus NS4A and ubiquitylates a conserved lysine residue for ER-associated degradation. This mechanism avoids excessive accumulation of NS4A, which otherwise interrupts the expression of processed flavivirus proteins in the ER. Furthermore, a small-molecule inhibitor of HRD1 named LS-102 effectively interrupts DENV2 infection in both mice and Aedes aegypti mosquitoes, and significantly disturbs DENV transmission from the infected hosts to mosquitoes owing to reduced viremia. Taken together, this study demonstrates that flaviviruses have evolved a sophisticated mechanism to exploit the ubiquitination system to balance the homeostasis of viral proteins for their own advantage and provides a potential therapeutic target to interrupt flavivirus infection and transmission.

Halofuginone for non-hospitalized adult patients with COVID-19 a multicenter, randomized placebo-controlled phase 2 trial. The HALOS trial

BACKGROUND

Halofuginone (PJS-539) is an oral prolyl-tRNA synthetase inhibitor that has a potent in vitro activity against SARS-CoV-2 virus. The safety and efficacy of halofuginone in Covid-19 patients has not been studied.

METHODS

We conducted a phase II, randomized, double-blind, placebo-controlled, dose ranging, safety and tolerability trial of halofuginone in symptomatic (≤ 7 days), mostly vaccinated, non-hospitalized adults with mild to moderate Covid-19. Patients were randomized in a 1:1:1 ratio to receive halofuginone 0.5mg, 1mg or placebo orally once daily for 10 days. The primary outcome was the decay rate of the SARS-CoV-2 viral load logarithmic curve within 10 days after randomization.

RESULTS

From September 25, 2021, to February 3, 2022, 153 patients were randomized. The mean decay rate in SARS-CoV-2 viral load log10 within 10 days was -3.75 (95% CI, -4.11; -3.19) in the placebo group, -3.83 (95% CI, -4.40; -2.27) in the halofuginone 0.5mg group and -4.13 (95% CI, -4.69; -3.57) in the halofuginone 1mg group, with no statistically significant difference in between placebo vs. halofuginone 0.5mg (mean difference -0.08; 95% CI -0.82 to 0.66, p = 0.96) and between placebo vs. halofuginone 1mg (mean difference -0.38; 95% CI, -1.11; 0.36, p = 0.41). There was no difference on bleeding episodes or serious adverse events at 28 days.

CONCLUSIONS

Among non-hospitalized adults with mild to moderate Covid-19 halofuginone treatment was safe and well tolerated but did not decrease SARS-CoV-2 viral load decay rate within 10 days.

Assessment of the broad-spectrum host targeting antiviral efficacy of halofuginone hydrobromide in human airway, intestinal and brain organotypic models

Halofuginone hydrobromide has shown potent antiviral efficacy against a variety of viruses such as SARS-CoV-2, dengue, or chikungunya virus, and has, therefore, been hypothesized to have broad-spectrum antiviral activity. In this paper, we tested this broad-spectrum antiviral activity of Halofuginone hydrobomide against viruses from different families (Picornaviridae, Herpesviridae, Orthomyxoviridae, Coronaviridae, and Flaviviridae). To this end, we used relevant human models of the airway and intestinal epithelium and regionalized neural organoids. Halofuginone hydrobomide showed antiviral activity against SARS-CoV-2 in the airway epithelium with no toxicity at equivalent concentrations used in human clinical trials but not against any of the other tested viruses.

Host microbiome associated low intestinal acetate correlates with progressive NLRP3-dependent hepatic-immunotoxicity in early life microcystin-LR exposure

BACKGROUND

Microcystins (MCs), potent hepatotoxins pose a significant health risk to humans, particularly children, who are more vulnerable due to higher water intake and increased exposure during recreational activities.

METHODS

Here, we investigated the role of host microbiome-linked acetate in modulating inflammation caused by early-life exposure to the cyanotoxin Microcystin-LR (MC-LR) in a juvenile mice model.

RESULTS

Our study revealed that early-life MC-LR exposure disrupted the gut microbiome, leading to a depletion of key acetate-producing bacteria and decreased luminal acetate concentration. Consequently, the dysbiosis hindered the establishment of a gut homeostatic microenvironment and disrupted gut barrier function. The NOD-like receptor family pyrin domain - containing 3 (NLRP3) inflammasome, a key player in MC-induced hepatoxicity emerged as a central player in this process, with acetate supplementation effectively preventing NLRP3 inflammasome activation, attenuating hepatic inflammation, and decreasing pro-inflammatory cytokine production. To elucidate the mechanism underlying the association between early-life MC-LR exposure and the progression of metabolic dysfunction associated steatotic liver disease (MASLD), we investigated the role of acetate binding to its receptor -G-protein coupled receptor 43 (GPR43) on NLRP3 inflammasome activation. Our results demonstrated that acetate-GPR43 signaling was crucial for decreasing NLRP3 protein levels and inhibiting NLRP3 inflammasome assembly. Further, acetate-induced decrease in NLRP3 protein levels was likely mediated through proteasomal degradation rather than autophagy. Overall, our findings underscore the significance of a healthy gut microbiome and its metabolites, particularly acetate, in the progression of hepatotoxicity induced by early life toxin exposure, crucial for MASLD progression.

CONCLUSIONS

This study highlights potential therapeutic targets in gut dysbiosis and NLRP3 inflammasome activation for mitigating toxin-associated inflammatory liver diseases.

E3 ubiquitin ligase ZBTB25 suppresses beta coronavirus infection through ubiquitination of the main viral protease MPro

The main protease of severe acute respiratory syndrome coronavirus 2, Mpro, is a key viral protein essential for viral infection and replication. Mpro has been the target of many pharmacological efforts; however, the host-specific regulation of Mpro protein remains unclear. Here, we report the ubiquitin-proteasome-dependent degradation of Mpro protein in human cells, facilitated by the human E3 ubiquitin ligase ZBTB25. We demonstrate that Mpro has a short half-life that is prolonged via proteasomal inhibition, with its Lys-100 residue serving as a potential ubiquitin acceptor. Using in vitro binding assays, we observed ZBTB25 and Mpro bind to each other in vitro, and using progressive deletional mapping, we further uncovered the required domains for this interaction. Finally, we used an orthologous beta-coronavirus infection model and observed that genetic ablation of ZBTB25 resulted in a more highly infective virus, an effect lost upon reconstitution of ZBTB25 to deleted cells. In conclusion, these data suggest a new mechanism of Mpro protein regulation as well as identify ZBTB25 as an anticoronaviral E3 ubiquitin ligase.

How Deep Learning in Antiviral Molecular Profiling Identified Anti-SARS-CoV-2 Inhibitors

The integration of artificial intelligence (AI) into drug discovery has markedly advanced the search for effective therapeutics. In our study, we employed a comprehensive computational-experimental approach to identify potential anti-SARS-CoV-2 compounds. We developed a predictive model to assess the activities of compounds based on their structural features. This model screened a library of approximately 700,000 compounds, culminating in the selection of the top 100 candidates for experimental validation. In vitro assays on human intestinal epithelial cells (Caco-2) revealed that 19 of these compounds exhibited inhibitory activity. Notably, eight compounds demonstrated dose-dependent activity in Vero cell lines, with half-maximal effective concentration (EC50) values ranging from 1 μM to 7 μM. Furthermore, we utilized a clustering approach to pinpoint potential nucleoside analog inhibitors, leading to the discovery of two promising candidates: azathioprine and its metabolite, thioinosinic acid. Both compounds showed in vitro activity against SARS-CoV-2, with thioinosinic acid also significantly reducing viral loads in mouse lungs. These findings underscore the utility of AI in accelerating drug discovery processes.

Influenza A virus replication has a stronger dependency on Raf/MEK/ERK signaling pathway activity than SARS-CoV-2

The recent COVID-19 pandemic again highlighted the urgent need for broad-spectrum antivirals, both for therapeutic use in acute viral infection and for pandemic preparedness in general. The targeting of host cell factors hijacked by viruses during their replication cycle presents one possible strategy for development of broad-spectrum antivirals. By inhibiting the Raf/MEK/ERK signaling pathway, a central kinase cascade of eukaryotic cells, which is being exploited by numerous viruses of different virus phyla, the small-molecule MEK inhibitor zapnometinib has the potential to address this need. We here performed a side-by-side comparison of the antiviral efficacy of zapnometinib against IAV and SARS-CoV-2 to determine the concentration leading to 50% of its effect on the virus (EC50) and the concentration leading to 50% reduction of ERK phosphorylation (IC50) in a comparable manner, using the same experimental conditions. Our results show that the EC50 value and IC50 value of zapnometinib are indeed lower for IAV compared to SARS-CoV-2 using one representative strain for each. The results suggest that IAV's replication has a stronger dependency on an active Raf/MEK/ERK pathway and, thus, that IAV is more susceptible to treatment with zapnometinib than SARS-CoV-2. With zapnometinib's favorable outcome in a recent phase II clinical trial in hospitalized COVID-19 patients, the present results are even more promising for an upcoming phase II clinical trial in severe influenza virus infection.

Prospecting native and analogous peptides with anti-SARS-CoV-2 potential derived from the trypsin inhibitor purified from tamarind seeds

The study aimed to prospect in silico native and analogous peptides with anti-SARS-CoV-2 potential derived from the trypsin inhibitor purified from tamarind seeds (TTIp). From the most stable theoretical model of TTIp (TTIp 56/287), in silico cleavage was performed for the theoretical identification of native peptides and generation of analogous peptides. The anti-SARS-CoV-2 potential was investigated through molecular dynamics (MD) simulation between the peptides and binding sites of transmembrane serine protease 2 (TMPRSS2), responsible for the entry of SARS-CoV-2 into the host cell. Five native and analogous peptides were obtained and validated through chemical and physical parameters. The best interaction potential energy (IPE) occurred between TMPRSS2 and one of the native peptides obtained by cleavage with trypsin and its analogous peptide. Thus, both peptides showed many hydrophobic residues, a common physical-chemical property among the peptides that inhibit the entry of enveloped viruses, such as SARS-CoV-2, present in specific drugs to treat COVID-19.

A semiconductor 96-microplate platform for electrical-imaging based high-throughput phenotypic screening

Profiling compounds and genetic perturbations via high-content imaging has become increasingly popular for drug discovery, but the technique is limited to endpoint images of fixed cells. In contrast, electronic-based devices offer label-free, functional information of live cells, yet current approaches suffer from low-spatial resolution or single-well throughput. Here, we report a semiconductor 96-microplate platform designed for high-resolution real-time impedance "imaging" at scale. Each well features 4,096 electrodes at 25 µm spatial resolution while a miniaturized data interface allows 8× parallel plate operation (768 total wells) within each incubator for enhanced throughputs. New electric field-based, multi-frequency measurement techniques capture >20 parameter images including tissue barrier, cell-surface attachment, cell flatness, and motility every 15 min throughout experiments. Using these real-time readouts, we characterized 16 cell types, ranging from primary epithelial to suspension, and quantified heterogeneity in mixed epithelial and mesenchymal co-cultures. A proof-of-concept screen of 904 diverse compounds using 13 semiconductor microplates demonstrates the platform's capability for mechanism of action (MOA) profiling with 25 distinct responses identified. The scalability of the semiconductor platform combined with the translatability of the high dimensional live-cell functional parameters expands high-throughput MOA profiling and phenotypic drug discovery applications.

Translation dynamics in human cells visualized at high resolution reveal cancer drug action

Ribosomes catalyze protein synthesis by cycling through various functional states. These states have been extensively characterized in vitro, but their distribution in actively translating human cells remains elusive. We used a cryo-electron tomography-based approach and resolved ribosome structures inside human cells with high resolution. These structures revealed the distribution of functional states of the elongation cycle, a Z transfer RNA binding site, and the dynamics of ribosome expansion segments. Ribosome structures from cells treated with Homoharringtonine, a drug used against chronic myeloid leukemia, revealed how translation dynamics were altered in situ and resolve the small molecules within the active site of the ribosome. Thus, structural dynamics and drug effects can be assessed at high resolution within human cells.

Role of E3 ubiquitin ligases and deubiquitinating enzymes in SARS-CoV-2 infection

Ever since its emergence in 2019, COVID-19 has rapidly disseminated worldwide, engendering a pervasive pandemic that has profoundly impacted healthcare systems and the socio-economic milieu. A plethora of studies has been conducted targeting its pathogenic virus, SARS-CoV-2, to find ways to combat COVID-19. The ubiquitin-proteasome system (UPS) is widely recognized as a crucial mechanism that regulates human biological activities by maintaining protein homeostasis. Within the UPS, the ubiquitination and deubiquitination, two reversible modifications, of substrate proteins have been extensively studied and implicated in the pathogenesis of SARS-CoV-2. The regulation of E3 ubiquitin ligases and DUBs(Deubiquitinating enzymes), which are key enzymes involved in the two modification processes, determines the fate of substrate proteins. Proteins associated with the pathogenesis of SARS-CoV-2 may be retained, degraded, or even activated, thus affecting the ultimate outcome of the confrontation between SARS-CoV-2 and the host. In other words, the clash between SARS-CoV-2 and the host can be viewed as a battle for dominance over E3 ubiquitin ligases and DUBs, from the standpoint of ubiquitin modification regulation. This review primarily aims to clarify the mechanisms by which the virus utilizes host E3 ubiquitin ligases and DUBs, along with its own viral proteins that have similar enzyme activities, to facilitate invasion, replication, escape, and inflammation. We believe that gaining a better understanding of the role of E3 ubiquitin ligases and DUBs in COVID-19 can offer novel and valuable insights for developing antiviral therapies.

Review of therapeutic mechanisms and applications based on SARS-CoV-2 neutralizing antibodies

COVID-19 pandemic is a global public health emergency. Despite extensive research, there are still few effective treatment options available today. Neutralizing-antibody-based treatments offer a broad range of applications, including the prevention and treatment of acute infectious diseases. Hundreds of SARS-CoV-2 neutralizing antibody studies are currently underway around the world, with some already in clinical applications. The development of SARS-CoV-2 neutralizing antibody opens up a new therapeutic option for COVID-19. We intend to review our current knowledge about antibodies targeting various regions (i.e., RBD regions, non-RBD regions, host cell targets, and cross-neutralizing antibodies), as well as the current scientific evidence for neutralizing-antibody-based treatments based on convalescent plasma therapy, intravenous immunoglobulin, monoclonal antibodies, and recombinant drugs. The functional evaluation of antibodies (i.e., in vitro or in vivo assays) is also discussed. Finally, some current issues in the field of neutralizing-antibody-based therapies are highlighted.

Rapid Determination of SARS-CoV-2 Antibody Neutralization Titer Using Bio-Rad Bio-Plex Correlates Strongly with Pseudovirus-Determined Neutralization Titer

Accurate and rapid evaluation of SARS-CoV-2 half-maximal neutralizing antibody (nAb) titer (NT50) is an important research tool for measuring nAb responses after prophylaxis or therapeutics for COVID-19 prevention and management. Compared with ACE2-competitive enzyme immunoassays for nAb detection, pseudovirus assays remain low-throughput and labor intensive. A novel application of the Bio-Rad Bio-Plex Pro Human SARS-CoV-2 D614G S1 Variant nAb Assay was used to determine NT50 from COVID-19-vaccinated individuals and showed strong correlation to a laboratory-developed SARS-CoV-2 Pseudovirus nAb assay. The Bio-Plex nAb assay could provide a rapid, high-throughput, culture-free method for NT50 determination in sera.

Protease-Responsive Potential-Tunable AIEgens for Cell Selective Imaging of TMPRSS2 and Accurate Inhibitor Screening

Transmembrane protease serine 2 (TMPRSS2) is a plasma membrane protease that activates both spike protein of coronaviruses for cell entry and oncogenic signaling pathways for tumor progression. TMPRSS2 inhibition can reduce cancer invasion and metastasis and partially prevent the entry of SARS-CoV-2 into host cells. Thus, there is an urgent need for both TMPRSS2-selective imaging and precise screening of TMPRSS2 inhibitors. Here, we report a TMPRSS2-responsive surface-potential-tunable peptide-conjugated probe (EGTP) with aggregation-induced emission (AIE) features for TMPRSS2 selective imaging and accurate inhibitor screening. The amphiphilic EGTP was constructed with tunable surface potential and responsive efficiency with TMPRSS2 and its inhibitor. The rational construction of AIE luminogens (AIEgens) with modular peptides indicated that the cleavage of EGTP led to a gradual aggregation with bright fluorescence in high TMPRSS2-expressing cells. This strategy may have value for selective detection of cancer cells, SARS-CoV-2-target cells, and screening of protease inhibitors.

Potential antiviral effects of pantethine against SARS-CoV-2

SARS-CoV-2 interacts with cellular cholesterol during many stages of its replication cycle. Pantethine was reported to reduce total cholesterol levels and fatty acid synthesis and potentially alter different processes that might be involved in the SARS-CoV-2 replication cycle. Here, we explored the potential antiviral effects of pantethine in two in vitro experimental models of SARS-CoV-2 infection, in Vero E6 cells and in Calu-3a cells. Pantethine reduced the infection of cells by SARS-CoV-2 in both preinfection and postinfection treatment regimens. Accordingly, cellular expression of the viral spike and nucleocapsid proteins was substantially reduced, and we observed a significant reduction in viral copy numbers in the supernatant of cells treated with pantethine. In addition, pantethine inhibited the infection-induced increase in TMPRSS2 and HECT E3 ligase expression in infected cells as well as the increase in antiviral interferon-beta response and inflammatory gene expression in Calu-3a cells. Our results demonstrate that pantethine, which is well tolerated in humans, was very effective in controlling SARS-CoV-2 infection and might represent a new therapeutic drug that can be repurposed for the prevention or treatment of COVID-19 and long COVID syndrome.

Human Coronavirus Cell Receptors Provide Challenging Therapeutic Targets

Coronaviruses interact with protein or carbohydrate receptors through their spike proteins to infect cells. Even if the known protein receptors for these viruses have no evolutionary relationships, they do share ontological commonalities that the virus might leverage to exacerbate the pathophysiology. ANPEP/CD13, DPP IV/CD26, and ACE2 are the three protein receptors that are known to be exploited by several human coronaviruses. These receptors are moonlighting enzymes involved in several physiological processes such as digestion, metabolism, and blood pressure regulation; moreover, the three proteins are expressed in kidney, intestine, endothelium, and other tissues/cell types. Here, we spot the commonalities between the three enzymes, the physiological functions of the enzymes are outlined, and how blocking either enzyme results in systemic deregulations and multi-organ failures via viral infection or therapeutic interventions is addressed. It can be difficult to pinpoint any coronavirus as the target when creating a medication to fight them, due to the multiple processes that receptors are linked to and their extensive expression.

High-Throughput Screening for the Potential Inhibitors of SARS-CoV-2 with Essential Dynamic Behavior

Global health security has been challenged by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic. Due to the lengthy process of generating vaccinations, it is vital to reposition currently available drugs in order to relieve anti-epidemic tensions and accelerate the development of therapies for Coronavirus Disease 2019 (COVID-19), the public threat caused by SARS-CoV-2. High throughput screening techniques have established their roles in the evaluation of already available medications and the search for novel potential agents with desirable chemical space and more cost-effectiveness. Here, we present the architectural aspects of highthroughput screening for SARS-CoV-2 inhibitors, especially three generations of virtual screening methodologies with structural dynamics: ligand-based screening, receptor-based screening, and machine learning (ML)-based scoring functions (SFs). By outlining the benefits and drawbacks, we hope that researchers will be motivated to adopt these methods in the development of novel anti- SARS-CoV-2 agents.

Phenothiazines inhibit SARS-CoV-2 cell entry via a blockade of spike protein binding to neuropilin-1

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters cells using angiotensin-converting enzyme 2 (ACE2) and neuropilin-1 (NRP-1) as the primary receptor and entry co-factor, respectively. Cell entry is the first and major step in initiation of the viral life cycle, representing an ideal target for antiviral interventions. In this study, we used a recombinant replication-deficient vesicular stomatitis virus-based pseudovirus bearing the spike protein of SARS-CoV-2 (SARS2-S) to screen a US Food and Drug Administration-approved drug library and identify inhibitors of SARS-CoV-2 cell entry. The screen identified 24 compounds as primary hits, and the largest therapeutic target group formed by these primary hits was composed of seven dopamine receptor D2 (DRD2) antagonists. Cell-based and biochemical assays revealed that the DRD2 antagonists inhibited both fusion activity and the binding of SARS2-S to NRP-1, but not its binding to ACE2. On the basis of structural similarity to the seven identified DRD2 antagonists, which included six phenothiazines, we examined the anti-SARS-CoV-2 activity of an additional 15 phenothiazines and found that all the tested phenothiazines shared an ability to inhibit SARS2-S-mediated cell entry. One of the phenothiazines, alimemazine, which had the lowest 50% effective concentration of the tested phenothiazines, exhibited a clear inhibitory effect on SARS2-S-NRP-1 binding and SARS-CoV-2 multiplication in cultured cells but not in a mouse infection model. Our findings provide a basis for the development of novel anti-SARS-CoV-2 therapeutics that interfere with SARS2-S binding to NRP-1.

Systematic analysis of alternative splicing in time course data using Spycone

MOTIVATION

During disease progression or organism development, alternative splicing may lead to isoform switches that demonstrate similar temporal patterns and reflect the alternative splicing co-regulation of such genes. Tools for dynamic process analysis usually neglect alternative splicing.

RESULTS

Here, we propose Spycone, a splicing-aware framework for time course data analysis. Spycone exploits a novel IS detection algorithm and offers downstream analysis such as network and gene set enrichment. We demonstrate the performance of Spycone using simulated and real-world data of SARS-CoV-2 infection.

AVAILABILITY AND IMPLEMENTATION

The Spycone package is available as a PyPI package. The source code of Spycone is available under the GPLv3 license at https://github.com/yollct/spycone and the documentation at https://spycone.readthedocs.io/en/latest/.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Structure-Guided Design of Halofuginone Derivatives as ATP-Aided Inhibitors Against Bacterial Prolyl-tRNA Synthetase

Aminoacyl-tRNA synthetases (aaRSs) are promising antimicrobial targets due to their essential roles in protein translation, and expanding their inhibitory mechanisms will provide new opportunities for drug discovery. We report here that halofuginone (HF), an herb-derived medicine, moderately inhibits prolyl-tRNA synthetases (ProRSs) from various pathogenic bacteria. A cocrystal structure of Staphylococcus aureus ProRS (SaProRS) with HF and an ATP analog was determined, which guided the design of new HF analogs. Compound 3 potently inhibited SaProRS at IC₅₀ = 0.18 μM and K_d = 30.3 nM and showed antibacterial activities with an MIC of 1-4 μg/mL in vitro. The bacterial drug resistance to 3 only developed at a rate similar to or slower than those of clinically used antibiotics in vitro. Our study indicates that the scaffold and ATP-aided inhibitory mechanism of HF could apply to bacterial ProRS and also provides a chemical validation for using bacterial ProRS as an antibacterial target.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and M^pro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Circulating Plasma Concentrations of ACE2 in Primary Aldosteronism and Cardiovascular Outcomes

CONTEXT

The plasma concentrations of angiotensin-converting enzyme 2 (pACE2) has been independently associated with cardiovascular diseases.

OBJECTIVE

Higher pACE2 concentrations may be found in patients with primary aldosteronism (PA) and might lead to increased cardiovascular events.

METHODS

Using an inception observational cohort, we examined pACE2 among 168 incident patients with PA. The expression of ACE2, serine protease 2 (TMPRSS2), and metalloprotease 17 (ADAM17) were assessed in peripheral blood mononuclear cells.

RESULTS

Incident PA and essential hypertension (EH) patients had similarly elevated pACE2 (47.04 ± 22.06 vs 46.73 ± 21.06 ng/mL; P = .937). Age was negatively (β = -2.15; P = .033) and higher serum potassium level (β = 2.29; P = .024) was positively correlated with higher pACE2 in PA patients. Clinical complete hypertension remission after adrenalectomy (Primary Aldosteronism Surgery Outcome criteria) was achieved in 36 (50%) of 72 surgically treated unilateral PA (uPA) patients. At follow-up, pACE2 decreased in surgically treated patients who had (P < .001) or had no (P = .006) hypertension remission, but the pACE2 attenuation was not statistically significant in uPA (P = .085) and bilateral PA (P = .409) administered with mineralocorticoid receptor antagonist (MRA). Persistently elevated pACE2 (> 23 ng/mL) after targeted treatments was related to all-cause mortality and cardiovascular events among PA patients (hazard ratio = 8.8; P = .04); with a mean follow-up of 3.29 years. TMPRSS2 messenger RNA (mRNA) expression was higher in uPA (P = .018) and EH (P = .038) patients than in normotensive controls; it was also decreased after adrenalectomy (P < .001).

CONCLUSION

PA and EH patients had elevated pACE2 and higher expression of TMPRSS2 mRNA compared to those of normotensive population. Persistently elevated pACE2 (> 23 ng/mL) after targeted treatments was associated risk of mortality and incident cardiovascular events.

Elucidating host cell response pathways and repurposing therapeutics for SARS-CoV-2 and other coronaviruses

COVID-19, first reported in late 2019, is an ongoing pandemic that has been causing devastation across the globe. Although there are multiple vaccines that can prevent severe symptoms, effective COVID-19 therapeutics are still of importance. Using our proprietary in silico engine, we screened more than 22,000 unique compounds represented by over half a million gene expression profiles to uncover compounds that can be repurposed for SARS-CoV-2 and other coronaviruses in a timely and cost-efficient manner. We then tested 13 compounds in vitro and found three with potency against SARS-CoV-2 with reasonable cytotoxicity. Bortezomib and homoharringtonine are some of the most promising hits with IC₅₀ of 1.39 μM and 0.16 μM, respectively for SARS-CoV-2. Tanespimycin and homoharringtonine were effective against the common cold coronaviruses. In-depth analysis highlighted proteasome, ribosome, and heat shock pathways as key targets in modulating host responses during viral infection. Further studies of these pathways and compounds have provided novel and impactful insights into SARS-CoV-2 biology and host responses that could be further leveraged for COVID-19 therapeutics development.

Transmembrane serine protease TMPRSS2 implicated in SARS-CoV-2 infection is autoactivated intracellularly and requires N-glycosylation for regulation

Transmembrane protease serine 2 (TMPRSS2) is a membrane-bound protease expressed in many human epithelial tissues, including the airway and lung. TMPRSS2-mediated cleavage of viral spike protein is a key mechanism in severe acute respiratory syndrome coronavirus 2 activation and host cell entry. To date, the cellular mechanisms that regulate TMPRSS2 activity and cell surface expression are not fully characterized. In this study, we examined two major post-translational events, zymogen activation and N-glycosylation, in human TMPRSS2. In experiments with human embryonic kidney 293, bronchial epithelial 16HBE, and lung alveolar epithelial A549 cells, we found that TMPRSS2 was activated via intracellular autocatalysis and that this process was blocked in the presence of hepatocyte growth factor activator inhibitors 1 and 2. By glycosidase digestion and site-directed mutagenesis, we showed that human TMPRSS2 was N-glycosylated. N-glycosylation at an evolutionarily conserved site in the scavenger receptor cysteine-rich domain was required for calnexin-assisted protein folding in the endoplasmic reticulum and subsequent intracellular trafficking, zymogen activation, and cell surface expression. Moreover, we showed that TMPRSS2 cleaved severe acute respiratory syndrome coronavirus 2 spike protein intracellularly in human embryonic kidney 293 cells. These results provide new insights into the cellular mechanism in regulating TMPRSS2 biosynthesis and function. Our findings should help to understand the role of TMPRSS2 in major respiratory viral diseases.

Structure and activity of human TMPRSS2 protease implicated in SARS-CoV-2 activation

Transmembrane protease, serine 2 (TMPRSS2) has been identified as key host cell factor for viral entry and pathogenesis of SARS-CoV-2. Specifically, TMPRSS2 proteolytically processes the SARS-CoV-2 Spike (S) protein, enabling virus-host membrane fusion and infection of the airways. We present here a recombinant production strategy for enzymatically active TMPRSS2 and characterization of its matured proteolytic activity, as well as its 1.95 Å X-ray cocrystal structure with the synthetic protease inhibitor nafamostat. Our study provides a structural basis for the potent but nonspecific inhibition by nafamostat and identifies distinguishing features of the TMPRSS2 substrate binding pocket that explain specificity. TMPRSS2 cleaved SARS-CoV-2 S protein at multiple sites, including the canonical S1/S2 cleavage site. We ranked the potency of clinical protease inhibitors with half-maximal inhibitory concentrations ranging from 1.4 nM to 120 µM and determined inhibitor mechanisms of action, providing the groundwork for drug development efforts to selectively inhibit TMPRSS2.

Homoharringtonine is a transdermal granular permeation enhancer

Although modulation of claudin-1-based tight junction (TJ) in stratum granulosum is an option for transdermal absorption of drugs, granular permeation enhancers have never been developed. We previously found that homoharringtonine (HHT), a natural alkanoid, weakened intestinal epithelial barrier with changing expression and cellular localization of TJ components such as claudin-1 and claudin-4. In the present study, we investigated whether HHT is an epidermal granular permeation enhancer. Treatment of normal human epidermal keratinocytes (NHEK) cells with HHT decreased claudin-1 and claudin-4 but not zonula occludens-1 and E-cadherin. HHT lowered TJ-integrity in NHEK cells, accompanied by permeation-enhancement of dextran (4 kDa) in a dose-dependent manner. Transdermal treatment of mice with HHT weakened epidermal barrier. HHT treatment enhanced transdermal absorption of dextran with a molecular mass of up to 10 kDa. Together, HHT may be a transdermal absorption enhancer.

Adjuvant Discovery via a High Throughput Screen using Human Primary Mononuclear Cells

Motivation

Vaccines are a key biomedical intervention to prevent the spread of infectious diseases, but their efficacy can be limited by insufficient immunogenicity and nonuniform reactogenic profiles. Adjuvants are molecules that potentiate vaccine responses by inducing innate immune activation. However, there are a limited number of adjuvants in approved vaccines, and current approaches for preclinical adjuvant discovery and development are inefficient. To enhance adjuvant identification, we developed a protocol based on in vitro screening of human primary leukocytes.

Summary

We describe a methodology utilizing high-throughput and high-content screening for novel adjuvant candidates that was used to screen a library of ~2,500 small molecules via a 384-well quantitative combined cytokine and flow cytometry immunoassay in primary human peripheral blood mononuclear cells (PBMCs) from 4 healthy adult study participants. Hits were identified based on their induction of soluble cytokine (TNF, IFNg and IL-10) secretion and PBMC maturation (CD 80/86, Ox40, and HLA-DR) in at least two of the four donors screened. From an initial set of 197 compounds identified using these biomarkers-an 8.6% hit rate-we downselected to five scaffolds that demonstrated robust efficacy and potency in vitro and evaluated the top hit, vinblastine sulfate, for adjuvanticity in vivo. Vinblastine sulfate significantly enhanced murine humoral responses to recombinant SARS-CoV-2 spike protein, including a four-fold enhancement of IgG titer production when compared to treatment with the spike antigen alone. Overall, we outline a methodology for discovering immunomodulators with adjuvant potential via high-throughput screening of PBMCs in vitro that yielded a lead compound with in vivo adjuvanticity.

Venetoclax Decreases the Expression of the Spike Protein through Amino Acids Q493 and S494 in SARS-CoV-2

The new coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) has been reported and spread globally. There is an urgent need to take urgent measures to treat and prevent further infection of this virus. Here, we use virtual drug screening to establish pharmacophore groups and analyze the ACE2 binding site of the spike protein with the ZINC drug database and DrugBank database by molecular docking and molecular dynamics simulations. Screening results showed that Venetoclax, a treatment drug for chronic lymphocytic leukemia, has a potential ability to bind to the spike protein of SARS-CoV-2. In addition, our in vitro study found that Venetoclax degraded the expression of the spike protein of SARS-CoV-2 through amino acids Q493 and S494 and blocked the interaction with the ACE2 receptor. Our results suggest that Venetoclax is a candidate for clinical prevention and treatment and deserves further research.

Suite of TMPRSS2 Assays for Screening Drug Repurposing Candidates as Potential Treatments of COVID-19

SARS-CoV-2 is the causative viral pathogen driving the COVID-19 pandemic that prompted an immediate global response to the development of vaccines and antiviral therapeutics. For antiviral therapeutics, drug repurposing allows for rapid movement of the existing clinical candidates and therapies into human clinical trials to be tested as COVID-19 therapies. One effective antiviral treatment strategy used early in symptom onset is to prevent viral entry. SARS-CoV-2 enters ACE2-expressing cells when the receptor-binding domain of the spike protein on the surface of SARS-CoV-2 binds to ACE2 followed by cleavage at two cut sites by TMPRSS2. Therefore, a molecule capable of inhibiting the protease activity of TMPRSS2 could be a valuable antiviral therapy. Initially, we used a fluorogenic high-throughput screening assay for the biochemical screening of 6030 compounds in NCATS annotated libraries. Then, we developed an orthogonal biochemical assay that uses mass spectrometry detection of product formation to ensure that hits from the primary screen are not assay artifacts from the fluorescent detection of product formation. Finally, we assessed the hits from the biochemical screening in a cell-based SARS-CoV-2 pseudotyped particle entry assay. Of the six molecules advanced for further studies, two are approved drugs in Japan (camostat and nafamostat), two have entered clinical trials (PCI-27483 and otamixaban), while the other two molecules are peptidomimetic inhibitors of TMPRSS2 taken from the literature that have not advanced into clinical trials (compounds 92 and 114). This work demonstrates a suite of assays for the discovery and development of new inhibitors of TMPRSS2.

Discovery of potential anti-SARS-CoV-2 drugs based on large-scale screening in vitro and effect evaluation in vivo

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global crisis. Clinical candidates with high efficacy, ready availability, and that do not develop resistance are in urgent need. Despite that screening to repurpose clinically approved drugs has provided a variety of hits shown to be effective against SARS-CoV-2 infection in cell culture, there are few confirmed antiviral candidates in vivo. In this study, 94 compounds showing high antiviral activity against SARS-CoV-2 in Vero E6 cells were identified from 2,580 FDA-approved small-molecule drugs. Among them, 24 compounds with low cytotoxicity were selected, and of these, 17 compounds also effectively suppressed SARS-CoV-2 infection in HeLa cells transduced with human ACE2. Six compounds disturb multiple processes of the SARS-CoV-2 life cycle. Their prophylactic efficacies were determined in vivo using Syrian hamsters challenged with SARS-CoV-2 infection. Seven compounds reduced weight loss and promoted weight regain of hamsters infected not only with the original strain but also the D614G variant. Except for cisatracurium, six compounds reduced hamster pulmonary viral load, and IL-6 and TNF-α mRNA when assayed at 4 d postinfection. In particular, sertraline, salinomycin, and gilteritinib showed similar protective effects as remdesivir in vivo and did not induce antiviral drug resistance after 10 serial passages of SARS-CoV-2 in vitro, suggesting promising application for COVID-19 treatment.

The battle between host and SARS-CoV-2: Innate immunity and viral evasion strategies

The SARS-CoV-2 virus, the pathogen causing COVID-19, has caused more than 200 million confirmed cases, resulting in more than 4.5 million deaths worldwide by the end of August, 2021. Upon detection of SARS-CoV-2 infection by pattern recognition receptors (PRRs), multiple signaling cascades are activated, which ultimately leads to innate immune response such as induction of type I and III interferons, as well as other antiviral genes that together restrict viral spread by suppressing different steps of the viral life cycle. Our understanding of the contribution of the innate immune system in recognizing and subsequently initiating a host response to an invasion of SARS-CoV-2 has been rapidly expanding from 2020. Simultaneously, SARS-CoV-2 has evolved multiple immune evasion strategies to escape from host immune surveillance for successful replication. In this review, we will address the current knowledge of innate immunity in the context of SARS-CoV-2 infection and highlight recent advances in the understanding of the mechanisms by which SARS-CoV-2 evades a host's innate defense system.

Design, Synthesis, and Proof-of-Concept of Triple-Site Inhibitors against Aminoacyl-tRNA Synthetases

Aminoacyl-tRNA synthetases (aaRSs) are promising drug targets due to their essential roles in protein translation. Although current inhibitors primarily occupy one or two of the three substrate binding sites on aaRSs, we report here the structure-based design of the first class of triple-site aaRS inhibitors by targeting Salmonella enterica threonyl-tRNA synthetase (SeThrRS). Competition of our compounds with all three substrates on SeThrRS binding was confirmed via isothermal titration calorimetry assays. Cocrystal structures of three compounds bound to SeThrRS unambiguously confirmed their substrate-mimicking triple-site binding mode. Compound 36j exhibited the best enzyme activity against SeThrRS with IC₅₀ = 19 nM and K_d = 35.4 nM. Compounds 36b, 36k, and 36l exhibited antibacterial activities with minimum inhibitory concentration values of 2-8 μg/mL against the tested bacteria, which are superior to those of the reported dual-site ThrRS inhibitors. Our study provides the first proof-of-concept for developing triple-site inhibitors against aaRSs, inspiring future aaRS-based drug discoveries.

The naturally-derived alkaloids as a potential treatment for COVID-19: A scoping review

Coronavirus disease 2019 (COVID‐19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‐CoV‐2), which has a high mortality rate and transmissibility. In this context, medicinal plants have attracted attention due to the wide availability and variety of therapeutic compounds, such as alkaloids, a vast class with several proven pharmacological effects, like the antiviral and anti‐inflammatory activities. Therefore, this scoping review aimed to summarize the current knowledge of the potential applicability of alkaloids for treating COVID‐19. A systematic search was performed on PubMed and Scopus, from database inception to August 2021. Among the 63 eligible studies, 65.07% were in silico model, 20.63% in vitro and 14.28% clinical trials and observational studies. According to the in silico assessments, the alkaloids 10‐hydroxyusambarensine, cryptospirolepine, crambescidin 826, deoxynortryptoquivaline, ergotamine, michellamine B, nigellidine, norboldine and quinadoline B showed higher binding energy with more than two target proteins. The remaining studies showed potential use of berberine, cephaeline, emetine, homoharringtonine, lycorine, narciclasine, quinine, papaverine and colchicine. The possible ability of alkaloids to inhibit protein targets and to reduce inflammatory markers show the potential for development of new treatment strategies against COVID‐19. However, more high quality analyses/reviews in this field are necessary to firmly establish the effectiveness/safety of the alkaloids here described.

A Suite of TMPRSS2 Assays for Screening Drug Repurposing Candidates as Potential Treatments of COVID-19.. [PMID: 35169799 PMCID: PMC8845423 DOI: 10.1101/2022.02.04.479134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

SARS-CoV-2 is the causative viral pathogen driving the COVID-19 pandemic that prompted an immediate global response to the development of vaccines and antiviral therapeutics. For antiviral therapeutics, drug repurposing allowed for rapid movement of existing clinical candidates and therapies into human clinical trials to be tested as COVID-19 therapies. One effective antiviral treatment strategy used early in symptom onset is to prevent viral entry. SARS-CoV-2 enters ACE2-expressing cells when the receptor-binding domain of the spike protein on the surface of SARS-CoV-2 binds to ACE2 followed by cleavage at two cut sites on the spike protein. TMPRSS2 has a protease domain capable of cleaving the two cut sites; therefore, a molecule capable of inhibiting the protease activity of TMPRSS2 could be a valuable antiviral therapy. Initially, we used a fluorogenic high-throughput screening assay for the biochemical screening of 6030 compounds in NCATS annotated libraries. Then, we developed an orthogonal biochemical assay that uses mass spectrometry detection of product formation to ensure that hits from the primary screen are not assay artifacts from the fluorescent detection of product formation. Finally, we assessed the hits from the biochemical screening in a cell-based SARS-CoV-2 pseudotyped particle entry assay. Of the six molecules advanced for further studies, two are approved drugs in Japan (camostat and nafamostat), two have entered clinical trials (PCI-27483 and otamixaban), while the other two molecules are peptidomimetic inhibitors of TMPRSS2 taken from the literature that have not advanced into clinical trials (compounds 92 and 114). This work demonstrates a suite of assays for the discovery and development of new inhibitors of TMPRSS2.

The Transmembrane Protease TMPRSS2 as a Therapeutic Target for COVID-19 Treatment

TMPRSS2 is a type II transmembrane protease with broad expression in epithelial cells of the respiratory and gastrointestinal tract, the prostate, and other organs. Although the physiological role of TMPRSS2 remains largely elusive, several endogenous substrates have been identified. TMPRSS2 serves as a major cofactor in SARS-CoV-2 entry, and primes glycoproteins of other respiratory viruses as well. Consequently, inhibiting TMPRSS2 activity is a promising strategy to block viral infection. In this review, we provide an overview of the role of TMPRSS2 in the entry processes of different respiratory viruses. We then review the different classes of TMPRSS2 inhibitors and their clinical development, with a focus on COVID-19 treatment.

Montelukast is a dual-purpose inhibitor of SARS-CoV-2 infection and virus-induced IL-6 expression identified by structure-based drug repurposing

Drug-repurposing has been instrumental to identify drugs preventing SARS-CoV-2 replication or attenuating the disease course of COVID-19. Here, we identify through structure-based drug-repurposing a dual-purpose inhibitor of SARS-CoV-2 infection and of IL-6 production by immune cells. We created a computational structure model of the receptor binding domain (RBD) of the SARS-CoV-2 spike 1 protein, and used this model for insilico screening against a library of 6171 molecularly defined binding-sites from drug molecules. Molecular dynamics simulation of candidate molecules with high RBD binding-scores in docking analysis predicted montelukast, an antagonist of the cysteinyl-leukotriene-receptor, to disturb the RBD structure, and infection experiments demonstrated inhibition of SARS-CoV-2 infection, although montelukast binding was outside the ACE2-binding site. Molecular dynamics simulation of SARS-CoV-2 variant RBDs correctly predicted interference of montelukast with infection by the beta but not the more infectious alpha variant. With distinct binding sites for RBD and the leukotriene receptor, montelukast also prevented SARS-CoV-2-induced IL-6 release from immune cells. The inhibition of SARS-CoV-2 infection through a molecule binding distal to the ACE-binding site of the RBD points towards an allosteric mechanism that is not conserved in the more infectious alpha and delta SARS-CoV-2 variants.

Neurological manifestations of coronavirus infections, before and after COVID-19: a review of animal studies

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus, which was first identified in December 2019 in China, has resulted in a yet ongoing viral pandemic. Coronaviridae could potentially cause several disorders in a wide range of hosts such as birds and mammals. Although infections caused by this family of viruses are predominantly limited to the respiratory tract, Betacoronaviruses are potentially able to invade the central nervous system (CNS) as well as many other organs, thereby inducing neurological damage ranging from mild to lethal in both animals and humans. Over the past two decades, three novel CoVs, SARS-CoV-1, MERS-CoV, and SARS-CoV-2, emerging from animal reservoirs have exhibited neurotropic properties causing severe and even fatal neurological diseases. The pathobiology of these neuroinvasive viruses has yet to be fully known. Both clinical features of the previous CoV epidemics (SARS-CoV-1 and MERS-CoV) and lessons from animal models used in studying neurotropic CoVs, especially SARS and MERS, constitute beneficial tools in comprehending the exact mechanisms of virus implantation and in illustrating pathogenesis and virus dissemination pathways in the CNS. Here, we review the animal research which assessed CNS infections with previous more studied neurotropic CoVs to demonstrate how experimental studies with appliable animal models can provide scientists with a roadmap in the CNS impacts of SARS-CoV-2. Indeed, animal studies can finally help us discover the underlying mechanisms of damage to the nervous system in COVID-19 patients and find novel therapeutic agents in order to reduce mortality and morbidity associated with neurological complications of SARS-CoV-2 infection.

ACE2, the Counter-Regulatory Renin-Angiotensin System Axis and COVID-19 Severity

Angiotensin (ANG)-converting enzyme (ACE2) is an entry receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). ACE2 also contributes to a deviation of the lung renin-angiotensin system (RAS) towards its counter-regulatory axis, thus transforming harmful ANG II to protective ANG (1-7). Based on this purported ACE2 double function, it has been put forward that the benefit from ACE2 upregulation with renin-angiotensin-aldosterone system inhibitors (RAASi) counterbalances COVID-19 risks due to counter-regulatory RAS axis amplification. In this manuscript we discuss the relationship between ACE2 expression and function in the lungs and other organs and COVID-19 severity. Recent data suggested that the involvement of ACE2 in the lung counter-regulatory RAS axis is limited. In this setting, an augmentation of ACE2 expression and/or a dissociation of ACE2 from the ANG (1-7)/Mas pathways that leaves unopposed the ACE2 function, the SARS-CoV-2 entry receptor, predisposes to more severe disease and it appears to often occur in the relevant risk factors. Further, the effect of RAASi on ACE2 expression and on COVID-19 severity and the overall clinical implications are discussed.