Dauricine interferes with SARS-CoV-2 variants infection by blocking the interface between RBD and ACE2.

The continued viral evolution results in the emergence of various SARS-CoV-2 variants, such as delta or omicron, that are partially resistant to current vaccines and antiviral medicines, posing an increased risk to global public health and raising the importance of continuous development of antiviral medicines. Inhibitor screening targeting the interactions between the viral spike proteins and their human receptor ACE2 represents a promising approach for drug discovery. Here, we demonstrate that the evolutionary trend of the SARS-CoV-2 variants is associated with increased electrostatic interactions between S proteins and ACE2. Virtual screening based on the ACE2-RBD binding interface identified nine monomers of Traditional Chinese medicine (TCM). Furthermore, live-virus neutralization assays revealed that Dauricine, one of the identified monomers, exhibited an antiviral activity with an IC50 range of 18.2 to 33.3 µM for original strain, Delta, and Omicron strains, respectively. The computational study showed that the polycyclic and methoxy groups of Dauricine adhere to the RBD surface through π-π and electrostatic interactions. The discovery of Dauricine is a successful attempt to target viral entry, which will not only help society to respond quickly to viral variants, but also accelerate variant drug development thereby reducing the pressure on health authorities to respond to outbreaks.

Angiotensin converting enzyme 2 gene expression and markers of oxidative stress are correlated with disease severity in patients with COVID-19.

BACKGROUND: Oxidative stress is thought to play a significant role in the pathogenesis and severity of COVID-19. Additionally, angiotensin converting enzyme 2 (ACE2) expression may predict the severity and clinical course of COVID-19. Accordingly, the aim of the present study was to evaluate the association of oxidative stress and ACE2 expression with the clinical severity in patients with COVID-19. METHODS AND RESULTS: The present study comprised 40 patients with COVID-19 and 40 matched healthy controls, recruited between September 2021 and March 2022. ACE 2 expression levels were measured using Hera plus SYBR Green qPCR kits with GAPDH used as an internal control. Serum melatonin (MLT) levels, serum malondialdehyde (MDA) levels, and total antioxidant capacity (TAC) were estimated using ELISA. The correlations between the levels of the studied markers and clinical indicators of disease severity were evaluated. Significantly, lower expression of ACE2 was observed in COVID-19 patients compared to controls. Patients with COVID-19 had lower serum levels of TAC and MLT but higher serum levels of MDA compared to normal controls. Serum MDA levels were correlated with diastolic blood pressure (DBP), Glasgow coma scale (GCS) scores, and serum potassium levels. Serum MLT levels were positively correlated with DBP, mean arterial pressure (MAP), respiratory rate, and serum potassium levels. TAC was correlated with GCS, mean platelet volume, and serum creatinine levels. Serum MLT levels were significantly lower in patients treated with remdesivir and inotropes. Receiver operating characteristic curve analysis demonstrates that all markers had utility in discriminating COVID-19 patients from healthy controls. CONCLUSIONS: Increased oxidative stress and increased ACE2 expression were correlated with disease severity and poor outcomes in hospitalized patients with COVID-19 in the present study. Melatonin supplementation may provide a utility as an adjuvant therapy in decreasing disease severity and death in COVID-19 patients.

Role of Vitamin D, ACE2 and the Proteases as TMPRSS2 and Furin on SARS-CoV-2 Pathogenesis and COVID-19 Severity.

BACKGROUND: COVID-19, the 21st century pandemic disease caused by SARS-CoV-2, has shown a wide clinical spectrum ranging from asymptomatic to deadly serious pneumonia. OBJECTIVE: In our study, the relationship between the pathogenesis and clinical severity of COVID-19 and vitamin D, ACE2, Furin and TMPRSS2 was investigated. METHODS: Serum 25(OH)D, 1,25(OH)2D and ACE2 protein were measured in 85 COVID-19 cases, divided into 5 groups, according to disease severity, from asymptomatic to severe and including a healthy control group. Expression levels of ACE2, VDR, TMPRSS2 and Furin mRNAs in PBMC were also measured. The relationship of the parameters within each group, the severity of the disease and the effect on the patients' fate were investigated. RESULTS: Statistically significant differences were found between the severity of COVID-19 and all study parameters, except for serum 25(OH)D. A strong negative correlation was found between serum ACE2 protein, 1,25(OH)2D, and ACE2 mRNA, and disease severity, length of hospital stay and death/survival rate. Vitamin D deficiency increased the death risk by 5.6-fold (95% CI 0.75-41.47), and the levels of 1,25(OH)2D lower than 1 ng/mL increased the risk of death by 3.8-fold (95% CI 1.07-13.30). CONCLUSION: This study suggests that vitamin D supplementation could be beneficial in the treatment and/or prevention of COVID-19.

Effects of Varying Glucose Concentrations on ACE2's Hypothalamic Expression and Its Potential Relation to COVID-19-Associated Neurological Dysfunction.

The coronavirus disease 2019 (COVID-19) pandemic has negatively impacted millions of lives, despite several vaccine interventions and strict precautionary measures. The main causative organism of this disease is the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) which infects the host via two key players: the angiotensin-converting enzyme 2 (ACE2) and the transmembrane protease, serine 2 (TMPRSS2). Some reports revealed that patients with glycemic dysregulation could have increased susceptibility to developing COVID-19 and its related neurological complications. However, no previous studies have looked at the involvement of these key molecules within the hypothalamus, which is the central regulator of glucose in the brain. By exposing embryonic mouse hypothalamic neurons to varying glucose concentrations, we aimed to investigate the expression of ACE2 and TMPRSS2 using quantitative real time polymerase chain reaction and western blotting. A significant and time-dependent increase and decrease was observed on the viability of hypothalamic neurons with increasing and decreasing glucose concentrations, respectively (p < 0.01 and p < 0.001, respectively). Under the same increasing and decreasing glucose conditions, the expression of hypothalamic ACE2 also revealed a significant and time-dependent increase (p < 0.01). These findings suggest that SARS-CoV-2 invades the hypothalamic circuitry. In addition, it highlights the importance of strict glycemic control for COVID-19 in diabetic patients.

Ginseng Protects ACE2-Transgenic Mice from SARS-CoV-2 Infection.

BACKGROUND: The pandemic caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is ongoing, and despite massive vaccination campaigns, individuals continue to be infected with new SARS-CoV-2 variants. We studied the effects of ginseng, an immune-enhancing agent, on conferring immunity against SARS-CoV-2 in transgenic mice expressing the SARS-CoV-2 human angiotensin-converting enzyme 2 (ACE2) receptor. METHODS: Human ACE2-transgenic (ACE2-tg) mice were fed ginseng extract for 180 days before they were intranasally infected with SARS-CoV-2. The mortality and morbidity were monitored for 10 days. The amount of antiviral interferon in the lung tissues was measured using enzyme-linked immunosorbent assay (ELISA) kits. RESULTS: Thirty percent of the mice fed ginseng extract prior to infection survived, whereas all those that were not fed ginseng extract prior to infection died. Viral titers in the lungs were significantly lower in mice fed ginseng extract than in those not fed ginseng extract. The induction of antiviral interferon-gamma (IFN-γ) was significantly higher in the lungs of mice fed ginseng extract than in those that were not. CONCLUSIONS: Our data indicate that a ginseng-containing diet may enhance immunity against SARS-CoV-2 in a mouse model.

Screening of Natural Products Inhibitors of SARS-CoV-2 Entry.

The COVID-19 pandemic has led to the search for new molecules with antiviral activity against SARS-CoV-2. The entry of the virus into the cell is one of the main targets for inhibiting SARS-CoV-2 infection. Natural products are an important source of new therapeutic alternatives against diseases. Pseudotyped viruses allow the study of SARS-CoV-2 viral entry inhibitors, and due to their simplicity, they allow the screening of a large number of antiviral candidates in Biosafety Level 2 facilities. We used pseudotyped HIV-1 with the D614G SARS-CoV-2 spike glycoprotein to test its ability to infect ACE2-expressing HEK 293T cells in the presence of diverse natural products, including 21 plant extracts, 7 essential oils, and 13 compounds from plants and fungi. The 50% cytotoxic concentration (CC50) was evaluated using the resazurin method. From these analyses, we determined the inhibitory activity of the extract of Stachytarpheta cayennensis, which had a half-maximal inhibitory concentration (IC50) of 91.65 µg/mL, a CC50 of 693.5 µg/mL, and a selectivity index (SI) of 7.57, indicating its potential use as an inhibitor of SARS-CoV-2 entry. Moreover, our work indicates the usefulness of the pseudotyped-virus system in the screening of SARS-CoV-2 entry inhibitors.

Computational profiling of natural compounds as promising inhibitors against the spike proteins of SARS-CoV-2 wild-type and the variants of concern, viral cell-entry process, and cytokine storm in COVID-19.

The continuous spread and evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the rapid surge in infection cases in the coronavirus disease 2019 (COVID-19) evoke a dire need for effective therapeutics. In this study, we explored the inhibitory potential of a library of 605 phytocompounds, selected from Indian medicinal plants with reported antiviral and anti-inflammatory activities, against the receptor-binding domain of spike proteins of the SARS-CoV-2 wild-type and the variants of concern, including variants B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta), and B.1.1.529 (Omicron). Our approach was based on extensive molecular docking, assessment of drug-likeness, and robust molecular dynamics simulations. We also identified promising inhibitory candidates against the host (human) proteins associated with SARS-CoV-2 spike activation and attachment, namely, ACE2 receptor, proteases TMPRSS2 and CTSL, and the endocytic regulator AAK1. In addition, we screened promising inhibitory compounds against the human proinflammatory cytokines- IL-6, IL-1ß, TNF-α, and IFN-γ, that are associated with the adverse cytokine storm in COVID-19 patients. Our analysis returned an encouraging list of promising inhibitory candidates that includes: abietatriene against the spike proteins of the SARS-CoV-2 wild-type and the variants of concern; taraxerol against the human ACE2, CTSL and TNF-α; ß-amyrin against the human TMPRSS2; cynaroside against the human AAK1 and IL-1ß; and friedelin against the human IL-6 and IFN-γ. Our findings provide substantial evidence for the inhibitory potential of these compounds and encourage further in vitro and in vivo studies to validate their use as safe and effective therapeutics against COVID-19.

COVA1-18 neutralizing antibody protects against SARS-CoV-2 in three preclinical models.

Effective treatments against Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) are urgently needed. Monoclonal antibodies have shown promising results in patients. Here, we evaluate the in vivo prophylactic and therapeutic effect of COVA1-18, a neutralizing antibody highly potent against the B.1.1.7 isolate. In both prophylactic and therapeutic settings, SARS-CoV-2 remains undetectable in the lungs of treated hACE2 mice. Therapeutic treatment also causes a reduction in viral loads in the lungs of Syrian hamsters. When administered at 10 mg kg-1 one day prior to a high dose SARS-CoV-2 challenge in cynomolgus macaques, COVA1-18 shows very strong antiviral activity in the upper respiratory compartments. Using a mathematical model, we estimate that COVA1-18 reduces viral infectivity by more than 95% in these compartments, preventing lymphopenia and extensive lung lesions. Our findings demonstrate that COVA1-18 has a strong antiviral activity in three preclinical models and could be a valuable candidate for further clinical evaluation.

A systems-level study reveals host-targeted repurposable drugs against SARS-CoV-2 infection.

Understanding the mechanism of SARS-CoV-2 infection and identifying potential therapeutics are global imperatives. Using a quantitative systems pharmacology approach, we identified a set of repurposable and investigational drugs as potential therapeutics against COVID-19. These were deduced from the gene expression signature of SARS-CoV-2-infected A549 cells screened against Connectivity Map and prioritized by network proximity analysis with respect to disease modules in the viral-host interactome. We also identified immuno-modulating compounds aiming at suppressing hyperinflammatory responses in severe COVID-19 patients, based on the transcriptome of ACE2-overexpressing A549 cells. Experiments with Vero-E6 cells infected by SARS-CoV-2, as well as independent syncytia formation assays for probing ACE2/SARS-CoV-2 spike protein-mediated cell fusion using HEK293T and Calu-3 cells, showed that several predicted compounds had inhibitory activities. Among them, salmeterol, rottlerin, and mTOR inhibitors exhibited antiviral activities in Vero-E6 cells; imipramine, linsitinib, hexylresorcinol, ezetimibe, and brompheniramine impaired viral entry. These novel findings provide new paths for broadening the repertoire of compounds pursued as therapeutics against COVID-19.

The TMPRSS2 Inhibitor Nafamostat Reduces SARS-CoV-2 Pulmonary Infection in Mouse Models of COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic has caused significant morbidity and mortality on a global scale. The etiologic agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), initiates host cell entry when its spike protein (S) binds to its receptor, angiotensin-converting enzyme 2 (ACE2). In airway epithelia, the spike protein is cleaved by the cell surface protease TMPRSS2, facilitating membrane fusion and entry at the cell surface. This dependence on TMPRSS2 and related proteases suggests that protease inhibitors might limit SARS-CoV-2 infection in the respiratory tract. Here, we tested two serine protease inhibitors, camostat mesylate and nafamostat mesylate, for their ability to inhibit entry of SARS-CoV-2 and that of a second pathogenic coronavirus, Middle East respiratory syndrome coronavirus (MERS-CoV). Both camostat and nafamostat reduced infection in primary human airway epithelia and in the Calu-3 2B4 cell line, with nafamostat exhibiting greater potency. We then assessed whether nafamostat was protective against SARS-CoV-2 in vivo using two mouse models. In mice sensitized to SARS-CoV-2 infection by transduction with human ACE2, intranasal nafamostat treatment prior to or shortly after SARS-CoV-2 infection significantly reduced weight loss and lung tissue titers. Similarly, prophylactic intranasal treatment with nafamostat reduced weight loss, viral burden, and mortality in K18-hACE2 transgenic mice. These findings establish nafamostat as a candidate for the prevention or treatment of SARS-CoV-2 infection and disease pathogenesis. IMPORTANCE The causative agent of COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), requires host cell surface proteases for membrane fusion and entry into airway epithelia. We tested the hypothesis that inhibitors of these proteases, the serine protease inhibitors camostat and nafamostat, block infection by SARS-CoV-2. We found that both camostat and nafamostat reduce infection in human airway epithelia, with nafamostat showing greater potency. We then asked whether nafamostat protects mice against SARS-CoV-2 infection and subsequent COVID-19 lung disease. We performed infections in mice made susceptible to SARS-CoV-2 infection by introducing the human version of ACE2, the SARS-CoV-2 receptor, into their airway epithelia. We observed that pretreating these mice with nafamostat prior to SARS-CoV-2 infection resulted in better outcomes, in the form of less virus-induced weight loss, viral replication, and mortality than that observed in the untreated control mice. These results provide preclinical evidence for the efficacy of nafamostat in treating and/or preventing COVID-19.

Resveratrol supplementation reduces ACE2 expression in human adipose tissue.

Angiotensin converting enzyme-2 (ACE2) is the cell-surface receptor enabling cellular entry of SARS-CoV-2. ACE2 is highly expressed in adipose tissue (AT), rendering AT a potential SARS-CoV-2 reservoir contributing to massive viral spread in COVID-19 patients with obesity. Although rodent and cell studies suggest that the polyphenol resveratrol alters ACE2, human studies are lacking. Here, we investigated the effects of 30-days resveratrol supplementation on RAS components in AT and skeletal muscle in men with obesity in a placebo-controlled cross-over study. Resveratrol markedly decreased ACE2 (~40%) and leptin (~30%), but did neither alter angiotensinogen, ACE and AT1R expression in AT nor skeletal muscle RAS components. These findings demonstrate that resveratrol supplementation reduces ACE2 in AT, which might dampen SARS-CoV-2 spread in COVID-19.

Inhibiting SARS-CoV-2 infection in vitro by suppressing its receptor, angiotensin-converting enzyme 2, via aryl-hydrocarbon receptor signal.

Since understanding molecular mechanisms of SARS-CoV-2 infection is extremely important for developing effective therapies against COVID-19, we focused on the internalization mechanism of SARS-CoV-2 via ACE2. Although cigarette smoke is generally believed to be harmful to the pathogenesis of COVID-19, cigarette smoke extract (CSE) treatments were surprisingly found to suppress the expression of ACE2 in HepG2 cells. We thus tried to clarify the mechanism of CSE effects on expression of ACE2 in mammalian cells. Because RNA-seq analysis suggested that suppressive effects on ACE2 might be inversely correlated with induction of the genes regulated by aryl hydrocarbon receptor (AHR), the AHR agonists 6-formylindolo(3,2-b)carbazole (FICZ) and omeprazole (OMP) were tested to assess whether those treatments affected ACE2 expression. Both FICZ and OMP clearly suppressed ACE2 expression in a dose-dependent manner along with inducing CYP1A1. Knock-down experiments indicated a reduction of ACE2 by FICZ treatment in an AHR-dependent manner. Finally, treatments of AHR agonists inhibited SARS-CoV-2 infection into Vero E6 cells as determined with immunoblotting analyses detecting SARS-CoV-2 specific nucleocapsid protein. We here demonstrate that treatment with AHR agonists, including FICZ, and OMP, decreases expression of ACE2 via AHR activation, resulting in suppression of SARS-CoV-2 infection in mammalian cells.

Postinfection treatment with a protease inhibitor increases survival of mice with a fatal SARS-CoV-2 infection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection continues to be a serious global public health threat. The 3C-like protease (3CLpro) is a virus protease encoded by SARS-CoV-2, which is essential for virus replication. We have previously reported a series of small-molecule 3CLpro inhibitors effective for inhibiting replication of human coronaviruses including SARS-CoV-2 in cell culture and in animal models. Here we generated a series of deuterated variants of a 3CLpro inhibitor, GC376, and evaluated the antiviral effect against SARS-CoV-2. The deuterated GC376 displayed potent inhibitory activity against SARS-CoV-2 in the enzyme- and the cell-based assays. The K18-hACE2 mice develop mild to lethal infection commensurate with SARS-CoV-2 challenge doses and were proposed as a model for efficacy testing of antiviral agents. We treated lethally infected mice with a deuterated derivative of GC376. Treatment of K18-hACE2 mice at 24 h postinfection with a derivative (compound 2) resulted in increased survival of mice compared to vehicle-treated mice. Lung virus titers were decreased, and histopathological changes were ameliorated in compound 2-treated mice compared to vehicle-treated mice. Structural investigation using high-resolution crystallography illuminated binding interactions of 3CLpro of SARS-CoV-2 and SARS-CoV with deuterated variants of GC376. Taken together, deuterated GC376 variants have excellent potential as antiviral agents against SARS-CoV-2.

Zinc supplementation augments the suppressive effects of repurposed NF-κB inhibitors on ACE2 expression in human lung cell lines.

AIMS: Angiotensin-converting enzyme 2 (ACE2) is a key negative regulator of the renin-angiotensin system and also a major receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Here, we reveal a role for NF-κB in human lung cell expression of ACE2, and we further explore the potential utility of repurposing NF-κB inhibitors to downregulate ACE2. MAIN METHODS: Expression of ACE2 was assessed by Western blotting and RT-qPCR in multiple human lung cell lines with or without NF-κB inhibitor treatment. Surface ACE2 expression and intracellular reactive oxygen species (ROS) levels were measured with flow cytometry. p50 was knocked down with siRNA. Cytotoxicity was monitored by PARP cleavage and MTS assay. KEY FINDINGS: Pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, suppressed endogenous ACE2 mRNA and protein expression in H322M and Calu-3 cells. The ROS level in H322M cells was increased after PDTC treatment, and pretreatment with N-acetyl-cysteine (NAC) reversed PDTC-induced ACE2 suppression. Meanwhile, treatment with hydrogen peroxide augmented ACE2 suppression in H322M cells with p50 knockdown. Two repurposed NF-κB inhibitors, the anthelmintic drug triclabendazole and the antiprotozoal drug emetine, also reduced ACE2 mRNA and protein levels. Moreover, zinc supplementation augmented the suppressive effects of triclabendazole and emetine on ACE2 expression in H322M and Calu-3 cells. SIGNIFICANCE: These results suggest that ACE2 expression is modulated by ROS and NF-κB signaling in human lung cells, and the combination of zinc with triclabendazole or emetine shows promise for clinical treatment of ACE2-related disease.

Identification and evaluation of the inhibitory effect of Prunella vulgaris extract on SARS-coronavirus 2 virus entry.

Until now, antiviral therapeutic agents are still urgently required for treatment or prevention of SARS-coronavirus 2 (SCoV-2) virus infection. In this study, we established a sensitive SCoV-2 Spike glycoprotein (SP), including an SP mutant D614G, pseudotyped HIV-1-based vector system and tested their ability to infect ACE2-expressing cells. Based on this system, we have demonstrated that an aqueous extract from the Natural herb Prunella vulgaris (NhPV) displayed potent inhibitory effects on SCoV-2 SP (including SPG614 mutant) pseudotyped virus (SCoV-2-SP-PVs) mediated infections. Moreover, we have compared NhPV with another compound, Suramin, for their anti-SARS-CoV-2 activities and the mode of their actions, and found that both NhPV and Suramin are able to directly interrupt SCoV-2-SP binding to its receptor ACE2 and block the viral entry step. Importantly, the inhibitory effects of NhPV and Suramin were confirmed by the wild type SARS-CoV-2 (hCoV-19/Canada/ON-VIDO-01/2020) virus infection in Vero cells. Furthermore, our results also demonstrated that the combination of NhPV/Suramin with an anti-SARS-CoV-2 neutralizing antibody mediated a more potent blocking effect against SCoV2-SP-PVs. Overall, by using SARS-CoV-2 SP-pseudotyped HIV-1-based entry system, we provide strong evidence that NhPV and Suramin have anti-SARS-CoV-2 activity and may be developed as a novel antiviral approach against SARS-CoV-2 infection.

Network-Based Analysis of Fatal Comorbidities of COVID-19 and Potential Therapeutics.

COVID-19 is a highly contagious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The case-fatality rate is significantly higher in older patients and those with diabetes, cancer or cardiovascular disorders. The human proteins, angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2) and basigin (BSG), are involved in high-confidence host-pathogen interactions with SARS-CoV-2 proteins. We considered these three proteins as seed nodes and applied the random walk with restart method on the human interactome to construct a protein-protein interaction sub-network, which captures the effects of viral invasion. We found that 'Insulin resistance', 'AGE-RAGE signaling in diabetic complications' and 'adipocytokine signaling' were the common pathways associated with diabetes, cancer and cardiovascular disorders. The association of these critical pathways with aging and its related diseases explains the molecular basis of COVID-19 fatality. We further identified drugs that have effects on these proteins/pathways based on gene expression studies. We particularly focused on drugs that significantly downregulate ACE2 along with other critical proteins identified by the network-based approach. Among them, COL-3 had earlier shown activity against acute lung injury and acute respiratory distress, while entinostat and mocetinostat have been investigated for non-small-cell lung cancer. We propose that these drugs can be repurposed for COVID-19.

Establishment of a well-characterized SARS-CoV-2 lentiviral pseudovirus neutralization assay using 293T cells with stable expression of ACE2 and TMPRSS2.

Pseudoviruses are useful surrogates for highly pathogenic viruses because of their safety, genetic stability, and scalability for screening assays. Many different pseudovirus platforms exist, each with different advantages and limitations. Here we report our efforts to optimize and characterize an HIV-based lentiviral pseudovirus assay for screening neutralizing antibodies for SARS-CoV-2 using a stable 293T cell line expressing human angiotensin converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2). We assessed different target cells, established conditions that generate readouts over at least a two-log range, and confirmed consistent neutralization titers over a range of pseudovirus input. Using reference sera and plasma panels, we evaluated assay precision and showed that our neutralization titers correlate well with results reported in other assays. Overall, our lentiviral assay is relatively simple, scalable, and suitable for a variety of SARS-CoV-2 entry and neutralization screening assays.

An Updated Review on Betacoronavirus Viral Entry Inhibitors: Learning from Past Discoveries to Advance COVID-19 Drug Discovery.

Even after one year of its first outbreak reported in China, the coronavirus disease 2019 (COVID-19) pandemic is still sweeping the World, causing serious infections and claiming more fatalities. COVID-19 is caused by the novel coronavirus SARS-CoV-2, which belongs to the genus Betacoronavirus (ß-CoVs), which is of greatest clinical importance since it contains many other viruses that cause respiratory disease in humans, including OC43, HKU1, SARS-CoV, and MERS. The spike (S) glycoprotein of ß-CoVs is a key virulence factor in determining disease pathogenesis and host tropism, and it also mediates virus binding to the host's receptors to allow viral entry into host cells, i.e., the first step in virus lifecycle. Viral entry inhibitors are considered promising putative drugs for COVID-19. Herein, we mined the biomedical literature for viral entry inhibitors of other coronaviruses, with special emphasis on ß-CoVs entry inhibitors. We also outlined the structural features of SARS-CoV-2 S protein and how it differs from other ß-CoVs to better understand the structural determinants of S protein binding to its human receptor (ACE2). This review highlighted several promising viral entry inhibitors as potential treatments for COVID-19.

Short linear motif candidates in the cell entry system used by SARS-CoV-2 and their potential therapeutic implications.

The first reported receptor for SARS-CoV-2 on host cells was the angiotensin-converting enzyme 2 (ACE2). However, the viral spike protein also has an RGD motif, suggesting that cell surface integrins may be co-receptors. We examined the sequences of ACE2 and integrins with the Eukaryotic Linear Motif (ELM) resource and identified candidate short linear motifs (SLiMs) in their short, unstructured, cytosolic tails with potential roles in endocytosis, membrane dynamics, autophagy, cytoskeleton, and cell signaling. These SLiM candidates are highly conserved in vertebrates and may interact with the µ2 subunit of the endocytosis-associated AP2 adaptor complex, as well as with various protein domains (namely, I-BAR, LC3, PDZ, PTB, and SH2) found in human signaling and regulatory proteins. Several motifs overlap in the tail sequences, suggesting that they may act as molecular switches, such as in response to tyrosine phosphorylation status. Candidate LC3-interacting region (LIR) motifs are present in the tails of integrin ß3 and ACE2, suggesting that these proteins could directly recruit autophagy components. Our findings identify several molecular links and testable hypotheses that could uncover mechanisms of SARS-CoV-2 attachment, entry, and replication against which it may be possible to develop host-directed therapies that dampen viral infection and disease progression. Several of these SLiMs have now been validated to mediate the predicted peptide interactions.

COVID-19 and diabetes; Possible role of polymorphism and rise of telemedicine.

BACKGROUND: Diabetes has been found to be one of the leading comorbidities associated with fatality in COVID-19 patients. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry is facilitated by interaction with Angiotensin Converting Enzyme-2 (ACE2) and possible polymorphisms in ACE2 can be a determining factor in host-viral protein interaction. A significant shift of healthcare towards 'Telemedicine' is also on the rise. In this review, the possible effects of ACE2 polymorphisms on SARS-CoV-2 entry along with the escalation of 'telemedicine' is discussed. METHOD: An expansive literature search using keywords: "COVID-19", "SARS-CoV-2", "diabetes", "type 2 diabetes'', "type 1 diabetes", "ACE2", "polymorphism", "DPP4" and "telemedicine" was conducted on Pubmed and EMBASE till 7th August 2020. RESULT: Possible polymorphisms in ACE2 gene can play a role in influencing the virus entry in host body. Telemedicine can bring a new revolution for medical sector. CONCLUSION: COVID-19 severity is more heinous among diabetic population. So far, the in-silico studies involving human ACE2-viral Spike (S) interaction showed inconsistent predictions regarding some SNPs. But without actual in-vivo studies, a holistic understanding can't be established.