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Objective To investigated the in vitro antiviral activity of chloroquine and hydroxychloroquine sulfate against different variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Prototype, Beta, Delta, Omicron) by changing the sequence of drug and virus introduction. Methods Prophylactic treatment: Vero E6 cells were treated with Chloroquine or hydroxychloroquine sulfate (200.00, 150.00, 100.00, 50.00, 16.70, 5.55, 1.85, 0.62, 0.21 micromol.L-1) for 1 h, then the virus was added and incubated for another 2 h. The virus-drug mixture was repalced with fresh medium until the end of the experiment. Post-entry treatment: Vero E6 cells were incubated with virus for 2 h, then the virus was removed and the cells were cultured with drug-containing medium until the end of the experiment. Full-time treatment: Vero E6 cells were pretreated with the drug for 1 h ahead, then virus was added and incubated for another 2 h. The virus-drug mixture was discarded and the cells were cultured with drug-containing medium until the end of the experiment. After 72 h of culture, the cells were observed to see whether they became round and shed to determine the cytopathic situation, and the semi-maximum effect concentration (EC50) and drug selection index (SI) were calculated. Results Both drugs were less effective in preventing SARS-CoV-2. Chloroquine/hydroxychloroquine sulfate showed good antiviral activity under both therapeutic and full-time treatment. EC50 of hydroxychloroquine sulfate was less than chloroquine, SI was greater than chloroquine, antiviral effect of hydroxychloroquine sulfate was better than chloroquine. The antiviral effect of chloroquine (EC50 = 0.904 micromol.L-1) and hydroxychloroquine sulfate (EC50 = 0.143 micromol.L-1) was more significant against Omicron variant than other variants under therapeutic and full-time treatment conditions. Conclusion Chloroquine/hydroxychloroquine sulfate showed good antiviral activity under both therapeutic and full-time treatment, and both drugs were significantly more active against the Omicron variant than the other variants.Copyright © 2023 Authors. All rights reserved.
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Background: Different viruses employ similar pathways for replication, revealing key intracellular hotspots to target with host-directed therapies and achieve a broad-spectrum antiviral activity. Plitidepsin is a clinically approved antitumoral agent that blocks the elongation factor eEF1A required for protein translation. This drug counteracts SARS-CoV-2 replication and shows a favorable safety profile in COVID-19 patients. Yet, the precise antiviral mechanism of action of plitidepsin remains unknown. Method(s): Here we used a deep quantitative proteomic analysis to measure the impact of plitidepsin on the proteome of SARS-CoV-2-infected Vero E6 cells. This was complemented with transmission electron microscopy assays, which unraveled the subcellular and morphological changes associated to plitidepsin treatment. In addition, we performed functional in vitro assays to dissect the antiviral activity of plitidepsin against SARS-CoV-2 and other viruses. Result(s): We found that this drug inhibited the synthesis of all SARS-CoV-2 proteins in a dose-dependent manner. These included the R1AB polyproteins, which facilitate the synthesis of non-structural proteins involved in the formation of double membrane vesicles (DMV) required for viral replication. Plitidepsin reduced DMV formation and the morphogenesis of new viruses, having a greater impact on viral than on host proteins. Less than 14% of the cellular proteome was significantly affected by plitidepsin, inducing the up-regulation of key molecules associated with protein biosynthesis, such as the translation initiation factors eIF4A2 and eIF2S3. Therefore, plitidepsin induced a compensatory state that rescued protein translation. This proteostatic response explains how cells preserve the cellular proteome after treatment with a translation inhibitor such as plitidepsin. In addition, it suggests that plitidepsin could inhibit other RNA-dependent and non-integrated DNA viruses, as we confirmed in vitro using Zika virus, Hepatitis C virus replicon and Herpes simplex virus. However, the compensatory proteostasis induced by plitidespin also explains why this drug failed to inhibit the replication of integrated DNA proviruses such as HIV-1. Conclusion(s): Unraveling the mechanism of action of host-directed therapies like plitidepsin is imperative to define the indications and antiviral profile of these compounds. This knowledge will be key to develop broad-spectrum treatments and have them ready to deploy when future pandemic viruses break through.
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The COVID-19 pandemic has dramatically underlined the desperate need for novel therapeutic options for treatment of respiratory viral infections to provide fast and efficacious drugs against new upcoming pathogens. RNA interference (RNAi)-based approaches depict a promising alternative to conventional medication, as they can be rapidly adjusted to the respective viral genome or its host cellular interaction partners. Here, we pursued both strategies. We designed and screened nine siRNAs targeting the viral entry receptor ACE2. SiA1, (siRNA against exon1 of ACE2 mRNA) was most efficient, with up to 90 % knockdown of the ACE2 mRNA and protein for at least six days, as assessed by a specially designed fluorescent reporter assay. siA1 application was found to protect Vero E6 and Huh-7 cells from infection with SARS-CoV-2 with an up to ~92 % reduction of the viral burden. In parallel, we exploited the respective sequence in generation miR30a-embedded lentivirally or AAV encoded shRNAs, which performed equally powerful, with shA1 being the most potent. Since the RNA-encoded genome makes SARS-CoV-2 vulnerable to RNA interference (RNAi), we designed and analyzed eight siRNAs directly targeting the Orf1a/b region of the SARS-CoV-2 RNA genome, encoding for non-structural proteins (nsp). We identified siV1, which targets the nsp1-encoding sequence as particularly efficient. SiV1 inhibited SARS-CoV-2 replication in Vero E6 or Huh-7 cells by more than 99 % or 97 %, respectively. It neither led to toxic effects nor induced type I or III interferon production. Of note, sequence analyses revealed the target sequence of siV1 to be highly conserved in SARS-CoV-2 variants. Thus, our results identify the direct targeting of the viral RNA genome (ORF1a/b) by siRNAs as highly efficient and introduce siV1 as a particularly promising drug candidate for therapeutic intervention. Preliminary in vivo pilot experiments carried out in a K18-hACE-2 mice model showed first promising results. Thereby siRNAs complexed with nanoparticles (LP10Y) were applicated systemically by intravenous injection. Mice were intranasally infected with SARS-CoV-2, euthanized 48 hours later, and the viral burden was determined by RT-qPCR in lung homogenates. A positive trend in viral reduction was found in comparison to corresponding control group.
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Background: Belarus started developing a vaccine against SARS-CoV- 2 in 2021. The aim of the first stage of investigation was to evaluate the immunogenicity of the vaccine prototypes (VP) in vitro. Method(s): SARS-CoV- 2 strains (n = 7) were isolated using Vero E6 cells, inactivated with beta-propiolactone and purified. Antigens (Ag) were adsorbed on adjuvants: Al(OH)3 (Ag+AH group) or Al3PO4 (Ag+AP group). The single dose of VP (500 ul) was composed of 10 mug of Ag adsorbed on adjuvants (200 mug of Al3+). Blood samples from SARS-CoV- 2 recovered donors (n = 18) and healthy controls having no history of COVID-19 infection (n = 5) were used. Whole blood and Tag-it Violet labeled PBMCs were cultivated with VP, pure Ag, adjuvants (0.25-1 mug of Ag, 20 mug of Al3+ for probe) or pool of peptides, covering sequence of SARS-CoV- 2 N, S, M-proteins (PP), for 6 h and 7 days respectively. INF-gamma production and proliferation of CD3+ T-cells were assayed by FACS. Result(s): Counts of CD3+IFN-gamma+ T cells were 3.14(2.72-5.13)/ 1x105 CD3+ T cells in negative control (NC), and 12.73(10.09-33.95)/ 1x105 CD3+ T cells in specific positive control (PP) (n = 18, p < 0.0001), proving presence of antigen-specific T cells (ASCs) in donor blood. Samples were considered positive for VP and Ag immunogenicity when numbers of CD3+IFN-gamma+ T cells were 1.5 times greater compared with NC. Both VP types (Ag+AP, Ag+AH) and pure SARS-CoV- 2 isolates stimulated the production of INF-gamma by ASCs, responses ranged from 1 to 4 isolates of 7 studied per donor. Immunogenicity of Ag+AP, Ag+AH was confirmed by proliferation assay. Proliferation level was 1.07(0.97-2.38)% in Ag group with no differences from NC (n = 7, p > 0.5). Proliferation was significantly greater in VP groups compared with Ag: 2.47(1.65-2.68)% in Ag+AH, 4.03(2.56-4.61)% in Ag+AP (p = 0.009 and 0.002, respectively), stimulation of T cell was stronger by Ag+AP compared with Ag+AH (p = 0.009, M-U test). Pure adjuvants did not induce T cells response. There was no T-cell stimulation by Ag and VP in samples obtained from COVID-19 negative donors. Conclusion(s): The VP against SARS-CoV- 2 infection composed of inactivated virus adsorbed on Al(OH)3 and Al3PO4 adjuvants has immunogenic properties proven in two different immunological assays. VP stimulated activation and proliferation of ASCs in vitro suggesting this VP can be used for further preclinical in vivo evaluation.
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Background: Severe viral pneumonia cases were observed in the people of Wuhan, China in December 2019. It has already affected almost every country around the globe and was declared a pandemic by the World Health Organization. We aim to evaluate the therapeutics and safety of various off label COVID-19 drugs. Method(s): PubMed, Research Gate, Science Direct, Google Scholar, Centre for Disease control and prevention (CDC) portal, Chinese Centre for Disease Control and prevention (CCDC) portal, World Health Organization (WHO) portal were searched for obtaining reliable data. Result(s): COVID-19 is creating a storm of deaths and active cases globally, which is forcing the pharmaceutical companies and scientists to work day and night to find an effective and safer anti-COVID-19 medication. Various in vitro and clinical trials had been performed as well as are currently ongoing to analyze the mechanisms and therapeutics of off label medications like Chloroquine, Hydroxychloro-quine, Amodiaquine, Azithromycin, Remdesivir, Favipiravir, Ritonavir/Lopinavir, Umifenovir, Osel-tamivir, Ribavirin, Nafamostat, Camostat, Tocilizumab, Ivermectin, Nitazoxanide, Famotidine, Vitamin D, Corticosteroids and Dexamethasone. In vitro studies were performed by utilizing Vero E6 cells and hSLAM cells while open/closed, randomized/non-randomized, single-centered/multi-centered and retrospective clinical trials and case studies were organized to determine their safety and efficacy. Conclusion(s): Although these drugs have shown promising results against COVID-19 patients, it cannot be concluded that these drugs are truly safe and effective because there are no conclusive evidence to support the facts since only limited researches and studies had been investigated.Copyright © 2021 Bentham Science Publishers.
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After two years into the pandemic of the coronavirus disease 2019 (COVID-19), it remains unclear how the host RNA interference (RNAi) pathway and host miRNAs regulate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and impact the development of COVID-19. In this study, we profiled small RNAs in SARS-CoV-2-infected human ACE2-expressing HEK293T cells and observed dysregulated host small RNA groups, including specific host miRNAs that are altered in response to SARS-CoV-2 infection. By comparing dysregulated miRNAs in different SARS-CoV-2-infected samples, we identified miRNA-210-3p, miRNA-30-5p, and miR-146a/b as key host miRNAs that may be involved in SARS-CoV-2 infection. Furthermore, by comparing virally derived small RNAs (vsmRNAs) in different SARS-CoV-2-infected samples, we observed multiple hot spots in the viral genome that are prone to generating vsmRNAs, and their biogenesis can be dependent on the antiviral isoform of Dicer. Moreover, we investigated the biogenesis of a recently identified SARS-CoV-2 viral miRNA encoded by ORF7a and found that it is differentially expressed in different infected cell lines or in the same cell line with different viral doses. Our results demonstrate the involvement of both host small RNAs and vsmRNAs in SARS-CoV-2 infection and identify these small RNAs as potential targets for anti-COVID-19 therapeutic development. © 2022 by the authors.
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The COVID-19 disease pandemic remains a significant global problem, resulting in hundreds of millions of cases and millions of deaths. The search for specific inhibitors of SARS-CoV-2 for the treatment of this infection remains relevant. Drugs such as Favipiravir and Molnupiravir, which exhibit specific antiviral activity against SARS-CoV-2, are already being used to treat patients. However, there is limited evidence of their effectiveness, especially against novel genetic variants of the COVID-19 pathogen. The aim of this study was to investigate the antiviral effect of these drugs using an in vitro experimental model of SARS-CoV-2 infection in Vero E6 cell culture and an animal model of infection using Syrian hamsters. It has been established that Molnupiravir has an inhibitory effect against variants of the SARS-CoV-2 with IC50 values from 16.51 to 7.88 microM in vitro, and reduces the infectious titer of the virus in the lungs of animals by ~1.5 Log10 in vivo, in while Favipiravir shows lower activity and severe toxicity. Dose selection and frequency of use remain unexplored.Copyright © 2022 Pirogov Russian National Research Medical University. All rights reserved.
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Background and Aims: Poor glucose control has been associated with increased mortality in COVID-19 patients with type 1 diabetes (T1D). The aim of this study was to assess the effect of glucose control on antibody response to the SARSCoV2 vaccine BNT162b2 in T1D. Method(s): We studied 26 T1D patients scheduled to receive two doses, 21 days apart, of BNT162b2, followed prospectively for six months with regular evaluation of SARS-CoV2 antibodies and glucose control. IgG to spike glycoprotein were assessed by ELISA, and serum neutralization by a live SARS-CoV2 assay (Vero E6 cells system). Continuous glucose monitoring, including time in range (TIR) and above range (TAR), and HbA1c were collected. The primary exposure and outcome measures were prevaccination glucose control, and antibody response after vaccination, respectively. IgG area under the curve (AUC) assessed the overall antibody response along the six-months study timeframe. Result(s): Baseline TIR and TAR strongly correlated with peak- IgG, as well as with the IgG-AUC (TIR: r = 0.75;p = 0.02;TAR: r = -0.81;p = 0.008). Furthermore, pre-vaccination TIR was associated with serum neutralization potency (r = 0.49;P = 0.042). Glucose control along the study timeframe was also associated with IgG response as showed by the correlation between timedependent mean of TIR and TAR and IgG-AUC (TIR: r = 0.93, P < 0.0001;TAR: r = -0.84, P < 0.0001). Pre-vaccination HbA1c was inversely related to peak-IgG, although the relationship did not reach statistical significance (r = -0.33;P = 0.14). Conclusion(s): Our findings indicate a strong relationship between glucose control and antibody response after SARS-CoV2 vaccination, highlighting the importance of achieving wellcontrolled blood glucose for COVID-19 prevention.
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Objective: COVID-19 association with cardiovascular disease is thought to be due to endothelial cell inflammation. ACE2 interactions with SARS-CoV-2 spike protein S1 subunit is important to viral infection. Here we questioned whether SARS-CoV-2 induces vascular inflammation via ACE2 and whether this is related to viral infection. Design and Methods: Human microvascular endothelial cells (EC) were exposed to recombinant S1p (rS1p) 0.66 ug/mL for 10 min, 5 h and 24 h. Gene expression was assessed by RT-PCR and levels of IL6 and MCP1, as well as ACE2 activity, were assessed by ELISA. Expression of ICAM1 and PAI1 was assessed by immunoblotting. ACE2 activity was blocked by MLN4760 (ACE2 inhibitor) and siRNA. Viral infection was assessed by exposing Vero E6 (kidney epithelial cells;pos ctl) and EC to 105 pfu of SARS-CoV-2 where virus titre was measured by plaque assay. Results: rS1p increased IL6 mRNA (14.2 ± 2.1 vs. C:0.61 ± 0.03 2-ddCT) and levels (1221.2 ± 18.3 vs. C:22.77 ± 3.2 pg/mL);MCP1 mRNA (5.55 ± 0.62 vs. C:0.65 ± 0.04 2-ddCT) and levels (1110 ± 13.33 vs. C:876.9 ± 33.4 pg/mL);ICAM1 (17.7 ± 3.1 vs. C:3.9 ± 0.4 AU) and PAI1 (5.6 ± 0.7 vs. C: 2.9 ± 0.2), p < 0.05. MLN4760, but not rS1p, decreased ACE2 activity (367.4 ± 18 vs. C: 1011 ± 268 RFU, p < 0.05) and blocked rS1p effects on ICAM1 and PAI1. ACE2 siRNA blocked rS1p-induced IL6 release, ICAM1, and PAI1 responses as well as rS1p-induced NFkB activation. EC were not susceptible to SARS-CoV-2 infection, while the virus replicated well in Vero E6. Conclusion: rS1p induces an inflammatory response through ACE2 in endothelial cells;an effect that was independent of viral infection.
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The COVID-19 virus has caused a global emergency and has attracted the attention of healthcare professionals and the public around the world. The significant increase in the number of new cases of infection with this virus demonstrates the relevance of the search for drugs that are effective against this pathogen. The aim of this work was to evaluate the antiviral efficacy of Mefloquin® against COVID-19. The antiviral efficacy of Mefloquin® against the new pandemic virus SARS-CoV-2 was studied in in vitro experiments in Vero C1008 cell culture and in vivo on Syrian golden hamsters. The results of the study revealed that the drug Mefloquine® at a concentration of 2.0 µg ml-1, when applied after infection of cells, suppresses the reproduction of the SARS-CoV-2 virus by 1.7-1.9 lg, the inhibition rate is about 99%. When using Mefloquine, pathological changes in the lung tissue were less pronounced than in the control group. 6 days after infection, it was shown that when using Mefloquine, there was a statistically significant decrease in viral load in the lungs of infected Syrian golden hamsters, with an inhibition rate of 95.5%.
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Purpose: To determine if IgM has a direct effect in preventing SARS-CoV-2 replication in Vero E6 cells, and delaying or preventing disease in infected K18- hACE2 mice. Method(s): 1) Vero E6 cells, grown to confluence in 12 well plates, were used to test the effect of IgM in reducing the number of plaque-forming units (PFU).There were 4 groups: a) 25PFU WA-1 SARS-CoV-2 was combined with 20, 5 or 0.8mug IgM in growth medium, and incubated for 1hr in a final volume of 500ul. 100mul was added to Vero E6 cells in replicate wells and incubated for 1hr;b) 100mul of 20, 5 or 0.8mug IgM was added to Vero E6 cells and incubated. Media was aspirated and the cells were then inoculated with 25PFU WA-1 and incubated for 1hr;c) Virus control - as above, but with no IgM;d) No virus or IgM. FBS growth medium containing Avicel was overlain in the wells and incubated for 48 hours. Virus replication was stopped by incubating with 10% buffered formalin. Following removal of formalin, plates were stained with Giemsa violet, dried, and photographed. 2) A COVID -19 Spike- ACE2 binding assay kit was used to determine if IgM (2ug, 4.5ug, 20ug, 45ug IgM) inhibits the interaction between the Spike-receptor binding domain (S-RBD) and Angiotensin I ConvertingEnzyme 2 (ACE2) receptor. 3) K18-hACE2 mice were divided into 3 groups based on treatment regimen;Group 1: with IgM, No virus;2: with Saline, with virus;3: with IgM, with virus. 35ug IgM was injected intraperitoneal in a single dose, 2 days prior to infection. Mice were innoculated intranasally with 1250 pfu of HK SARS-CoV-2. Result(s): 1) Exposure of 25PFU SARS-CoV-2 to IgM (at all concentrations) prior to incubation with Vero E6 cells, inhibited its replication in Vero E6 cells. When Vero E6 cells were incubated with IgM prior to infection, no plaques were seen in wells with 20ug and 5ug IgM but were observed in wells with 0.8ug IgM. Plaques were also observed in the Virus alone group, but none were seen in the 'No IgM-No virus' group. 2) 45ug IgM/100uls inhibited the binding of S-RBD to ACE2 by ~94-100%, 20ug IgM/100uls inhibited it by ~80%, and 2 or 4.5ug/100ul by ~70-75%. Control without IgM did not inhibit the S-RBD-ACE-2 binding. 3) Pretreatment with a single low dose IgM injection delayed weight loss and mortality. Conclusion(s): IgM inhibits the replication of SARS-CoV-2 in Vero cells in vitro. It also inhibits the interaction between S-RBD that is present on the viral surface and the ACE2 receptor, by binding to S-RBD. A single low dose of IgM given prechallenge delayed disease in infected mice. The discovery that IgM interferes with the formation of the S-RBD-ACE2 complex, and that a single low dose can delay disease, indicates its translational potential as a vaccine/therapeutic to prevent or treat COVID-19.
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Background & Aim: From SARS-CoV-1 outbreak in 2002 to the most recent SARS-CoV-2 pandemic (COVID-19), emergence of viral diseases has repeatedly threatened humanity over the recent decades. These viral diseases mainly cause respiratory symptoms, which can even lead to death when appropriate measures are not taken. In this study, we investigated whether adipose tissue-derived mesenchymal stem cell EVs (ASC-EVs) can attenuate acute lung injury (ALI) induced by H1N1 influenza A virus and SARS-CoV-2 and by what mechanism the ant-viral effect may occurs. Methods, Results & Conclusion: EVs were isolated from ASC or HEK293T conditioned media by tangential flow filtration, and were characterized according to MISEV recommendation. Influenza A/ Puerto Rico/08/1934 (H1N1) and SARS-CoV-2 (NCCP43326) were used to model highly pathogenic human influenza A and SARS-CoV-2 virus infection, respectively, in mice and Syrian hamsters respectively. Treatment of ASC-EVs, from 0.15 x 109 to 5.0 x 109 particles/mL, showed inhibitory activities on cytopathic effects and replication of H1N1 and SARS-CoV-2 in MDCK cells and Vero E6 cells, respectively. In the mouse H1N1 influenza A virus induced acute lung injury (ALI) model, total of 4 daily injections of 1 x 1010 particles of ASC-EVs administration resulted in significantly increased survival rate by 30 – 40%, recovery of body weight, and improved clinical disease score from 9 dpi. In addition, ASC-EV treatment downregulated various inflammatory cytokines such as IL-1β, IL-6 and TNFα in lung tissue by up to 77%. In the Syrian hamster SARS-CoV-2 induced ALI model, total of 4 daily injections of ASC-EVs at a dose of 3 x 1010 or 1 x 1010 particles resulted recovery of body weights from 5 dpi, in a dose-dependent manner, by 9.7% - 12.75%. Further, ASC-EV treatment resulted in significant downregulation of viral genes and IL-1 beat in lung tissue. To elucidate the molecular mechanisms of the observed anti-viral effects of ASC-EVs, the role of multiple miRNAs and proteins present in the ASC-EVs were assessed in vitro. We identified one specific protein that conveyed anti-viral efficacy against the two studied viruses including SARS-CoV-2. Loss and gain of function studies revealed that this protein may be involved in the anti-viral efficacy of the ASC-EVs. Our findings support the concept that that ASC-EVs have anti-viral effects against virus induced ALI, which may have implications for the treatment of not only treatment COVID-19, but also future ALI-inducing virus diseases.
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Background: Diarrhea is present in up to 36.6% of patients with COVID-19. The mechanism of SARS-CoV-2-induced diarrhea remains unclear. We hypothesized that enterocyte-enteric neuron interactions were important in SARS-CoV-2-induced diarrhea. SARS-CoV-2 induces endoplasmic reticulum (ER) stress in enterocytes causing the release of Damage Associated Molecular Patterns (DAMPs). The DAMPs then stimulate the release of enteric neurotransmitters that disrupt gut electrolyte homeostasis. The influence of ER stress and enteric neuronderived vasoactive intestinal peptide (VIP) on the expression of Na+/H+ exchanger 3 (NHE3), an important transporter that mediates intestinal Na+/fluid absorption, was further examined. Methods: SARS-CoV-2 propagated in Vero-E6 cells was used to infect Caco-2, a human colon epithelial cell line that expresses SARS-CoV-2 entry receptor ACE2. The expression of ER stress markers, phospho-PERK, Xbp1s, and DAMP proteins, was examined by Western blotting. Primary mouse enteric neurons were treated with a conditioned medium of Caco- 2 cells that were infected with SARS-CoV-2 or treated with tunicamycin. VIP expression by cultured enteric neurons was assessed by RT-qPCR, Western blotting, and ELISA. Membrane expression of NHE3 was determined by surface biotinylation. Results: SARS-CoV-2 infection of Caco-2 cells led to increased expression of phospho-PERK and Xbp1s indicating increased ER stress. Infected Caco-2 cells secreted DAMP proteins, including HSP70 and calreticulin, as revealed by proteomic and Western analyses. The expression of VIP mRNA in enteric neurons was up-regulated after treatment with a conditioned medium of SARS-CoV-2- infected Caco-2 cells (Mock, 1 ± 0.0885;and SARS-CoV-2, 1.351 ± 0.020, P=.005). CD91, a receptor for HSP70 and calreticulin, is abundantly expressed in cultured mouse and human enteric neurons and was up-regulated by a conditioned medium of SARS-CoV-2-infected Caco-2 cells. Tunicamycin, an inducer of ER stress, also induced the secretion of HSP70 and calreticulin, mimicking SARS-CoV-2 infection. Moreover, co-culture of enteric neurons with tunicamycin-treated Caco-2 cells stimulated VIP production as determined by ELISA. Co-treatment of Caco-2 cells with tunicamycin (apical) and VIP (basolateral) induced a synergistic decrease in the membrane expression of NHE3. Conclusions: Our findings demonstrate that SARS-CoV-2 infection of enterocytes leads to ER stress and the release of DAMPs that up-regulate the expression and release of VIP by enteric neurons. The presence of ER stress together with the secreted VIP, in turn, inhibits fluid absorption through the downregulation of brush-border membrane expression of NHE3 in the enterocytes. These data highlight epithelial-neuronal crosstalk in COVID-19 related diarrhea. (Figure Presented)
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Background: The use of COVID-19 convalescent plasma (CCP) as experimental therapy during the SARS-CoV-2 outbreak has led to the need to quantify neutralizing antibodies (Abs) to SARS-CoV-2 to make it suitable for clinical use. In this respect, the National Blood Centre (CNS) and the National Centre for the Control and Evaluation of Medicines (CNCF) of the Istituto Superiore di Sanit(ISS) have organized an External Quality Assessment (EQA) exercise on serological methods for CCP Ab screening. Aims: To present the results deriving from the anti-SARS-COV-2 EQA program. Methods: Blood donations with anti-SARS-CoV-2 Abs at different concentrations were used as positive samples. Negative samples were prepared using a pool of plasma donations negative for anti-SARS-CoV-2 Abs and tested negative for HBV, HCV, HIV and Syphilis markers. A panel of 10 samples (two negative and eight positive) has been sent to each participating laboratory. Production, storage and distribution of the panels were carried out according to pre-established procedures to ensure the homogeneity and stability of the samples. The samples were tested for the presence of neutralizing Abs using a neutralization assay based on the use of lentiviral particles pseudotyped with the SARS-CoV-2 Spike glycoprotein, and expressing luciferase as a detection system infectivity in VERO E6 cells1.On the basis of anti- SARS-CoV-2 Ab content, the 10 panel samples were divided into four groups: negative (2 samples, ID90 < 20), low positive (2 samples ID90 ~ 50), medium positive (three samples, ID90 100-200) and high positive (three samples, ID90 300-800). 28 laboratories participated to the EQA study using five different methods. In particular, three laboratories participated with two different methods. Results: 30 out of 31 panels were correctly identified: one laboratory erroneously identified a negative sample as reactive. The re-test of the panel gave the correct result. Quantitative results (14 laboratories) were converted in Binding Antibody Unit (BAU/ml) using the conversion factor indicated by the kits' manufacturer. The conversion in BAU/ml allowed to standardize the results from different methods: in fact, after conversion, results seem to be more closed even if some differences are still present in two samples with a high content of IgG. Summary/Conclusions: The EQA exercise provided the participants a valid tool to test the laboratory performance and to highlight any critical issues concerning a not-routinely performed test, used by several blood establishments for the qualification of CCP. Moreover, the use of a common measure unit (BAU/ml) using the WHO international standard for SARS-CoV-2 immunoglobulin seems to reduce the differences among methods improving the analytical and diagnostic comparability. However, it is not true for all samples tested. The intrinsic Ab composition of each samples tested (presence of different type of Abs, the Abs' avidity and specificity, time of recovery from the infection) may contribute to the persistence of differences of the results across methods. 1. Dispinseri S, Nat. Commun. 2021.
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For many years, our laboratory has been developing cellular models for the study of human pathogenic viruses with RNA genomes, in order to study the replication of these pathogens, to propose new therapeutic pathways, to screen and test inhibitors. In response to the COVID-19 outbreak, we have set up the tools for the study of SARS-CoV-2 replication. First, clinical and reference SARS-CoV-2 strains have been successfully isolated and amplified using Vero E6 cells in the BSL3 facility of Bordeaux University (UB'L3, www.mfp.cnrs.fr/wp/larecherche/ andevir/ubl3/). We set up the monitoring of SARS-CoV-2 replication using conventional RT-qPCR quantification as well as evaluation of the cytopathic effect by microscopic observation or content analysis. Using VERO cells, we are now able to precisely titer viral supernatant (determination of the TCID50) and screen for potential antiviral molecule (determination of EC50 and CC50). We have developed a full-length Spike sequencing based on a Sanger approach1 as well as whole genome sequencing by nanopore technology, allowing the tracking of emerging variants. In parallel, we developed various other models to study SARS-CoV-2 replication including Calu-3 cells, modified human cells expressing Ace2 (e.g. 293T, U2OS) or even more complex cellular models (reconstituted human airway epithelium, vessels) according to the biological question to resolve. As an example, bronchial epithelia reconstituted from biopsies of adult or child donors were used to evaluate the inflammatory response upon SARS-CoV-2 infection in an age-dependent manner [2] (see poster G. Beucher). Similarly reconstituted blood vessels were used to study the impact of SARS-CoV- 2 infection on the vascular system and determine whether clinical observations (blood brain barrier damages, myocarditis) are due to direct infection of cells or indirect effects. Finally, we evaluate the efficacy of different chemical or physical processes for viral inactivation in air or on surfaces.
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Background: Antivirals are urgently needed to supplement SARS-CoV-2 vaccines and target SARS-CoV-2 variants of concern, particularly in resource-limited regions. Active derivatives from the medicinal plant Gunnera perpensa, already in use as a general antiviral in humans by traditional health practitioners in the Eastern Cape Province of South Africa, warrant further evaluation against SARS-CoV-2. Methods: Active constituents of Gunnera perpensa were identified using hyphenated analytical techniques and for ability to inhibit binding of recombinant SARS-CoV-2 spike with host ACE2 protein as assessed by AlphaScreen. Inhibition was tested against parental (USA-WA1/2020), beta (B.1.351), and delta (B.1.617.2) spike proteins using AlphaScreen and spike-expressing VSVΔG-GFP pseudoviruses. Infection of Vero cells was monitored by high-content imaging of GFP or nucleocapsid-positive Vero-E6 cells in pseudovirus and virus assays, respectively, at 2 days post-infection (dpi). Viral cytopathic effect (CPE) ± GC-376 or remdesivir was also monitored using resazurin viability dye at 4 dpi. All assays were described previously (PMID: 34543092). Synergism was assessed by the Bliss Independence model, and group differences were analyzed by two-sided, paired t-test. Results: Crude extracts from the leaves of Gunnera perpensa were confirmed to inhibit parental spike/ACE2 interactions with an IC50 of 37 ± 23 ng/mL. Bioassay-guided fractionation identified two ellagitannins, punicalin and punicalagin, which inhibited parental, beta, and delta spike/ACE2 binding with IC50s of 2.7 ± 0.6-5.8 ± 4.8 and 6.0 ± 4.5-19 ± 23 nM, respectively. Both compounds inhibited all spike variants in pseudovirus at low to mid micromolar concentrations (see Table). Notably, in CPE-based viral assays, a 1:1 molar mixture of punicalin and punicalagin significantly enhanced antiviral activity (EC50 = 2.9 μM vs. 11.6 and 46.8 μM for single compounds, p < 0.05), on par with activities of preclinical candidate GC-376 (1.3 μM) and remdesivir (2.8 μM;see Table). When combined in a 1:1 molar mixture, punicalin further significantly enhanced activity of GC-376 (EC50 = 0.6 μM, p < 0.05) and remdesivir (EC50 = 1.1 μM, p < 0.05). Conclusion: Punicalin and punicalagin inhibit entry and replication of SARS-CoV-2 variants in vitro and synergize when applied in combination and/or with GC-376 or remdesivir. Ellagitannins and medicinal plant extracts are promising new leads for SARS-CoV-2 antivirals in resource-limited regions.
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Background: SARS-CoV-2 has caused a global pandemic, yet despite vaccine availability, it continues to inflict morbidity and mortality worldwide. The viral main protease (Mpro) is highly conserved across multiple coronaviruses and has a unique viral substrate specificity. Thus, highly selective Mpro inhibitors are expected to be safe, effective, and elude drug resistance for future coronaviruses. Methods: We used a conformationally restricted peptidomimetic to mimic the bioactive conformation of the Mpro-substrate complex to identify potent, selective Mpro inhibitors. We evaluated protease inhibition in biochemical assays, and cellular efficacy in Vero-E6 cells challenged with live virus representing parental (USA-WA1/2020), beta (B.1.351), and delta (B.1.617.2) variants by monitoring infection at day 2 post-infection measuring nucleocapsid-positive cells by high content imaging, and cytopathic effect (CPE) at day 4 post-infection using resazurin viability dye. Results were compared to reference compounds. Group differences were analyzed by two-sided, paired t-test. Results: AP-8-013 required a 2-hour incubation to achieve maximal dose-dependent Mpro inhibition with an IC50 = 230 ± 18 nM, reflecting its highly constrained conformation, compared to the more flexible Cpd 22 (AP-8-001;IC50 = 11 ± 0.7 nM) or GC-376 (IC50 = 18 ± 1.5 μM). Importantly, AP-8-013 showed exquisite selectivity for Mpro with no inhibition at key mammalian cysteine proteases, cathepsin B and L, or the serine protease thrombin, while Cpd 22 (Cat B IC50 = 24 ± 7.5 nM, Cat L IC50 = 1.8 ± 0.3 nM) or GC-376 (Cat B IC50 = 37 ± 1.5 nM, Cat L IC50 = < 1 nM) showed poor selectivity towards mammalian cysteine proteases. AP-8-013 was active in CPE cell-based assays with comparable potency to reference compounds, with EC50 = 4.7 μM compared to Cmp 22 (EC50 = 1.4 μM) or GC-376 (EC50 = 1.1 μM). Using intact SARS-CoV-2 infection-based assays, AP-8-013 significantly inhibited parental virus as well as beta and delta VOC (EC50s = 2.7, 2.5, and 6.0 μM, respectively). Finally, a 3:1 molar mixture of AP-8-013 and remdesivir significantly enhanced antiviral activity in CPE assays (EC50 = 1.3 μM;p < 0.05) when compared against either compound alone (EC50s = 4.7 and 3.3 μM, respectively). Conclusion: We have identified a novel drug-like Mpro inhibitor lead series which is highly selective over cysteine and serine proteases that can inhibit multiple SARS-CoV-2 VOC and increase the antiviral activity of remdesivir.
ABSTRACT
Background: The use of compounds against highly conserved cellular host factors required to complete the replication cycle of distinct viruses such as SARS-CoV-2 offers a common solution to diverse viral threats. This approach is especially relevant for pan-antiviral effects given that viruses converge at intracellular steps such as viral genome replication and protein production. Currently, there are only a limited number of approved drugs involved in targeting intracellular host factors. One of these compounds is plitidiepsin, which has shown a potent preclinical efficacy against SARS-CoV-2 by targeting the host protein eEF1A. Plitidepsin inhibits nucleocapsid viral protein expression and viral induced cytopathic effect in vitro. In addition, it also reduces genomic and subgenomic RNA expression. However, how plitidepsin exerts its antiviral activity remains unknown. Methods: Current models of SARS-CoV-2 replication propose that upon viral fusion, non-structural viral proteins form a replication-transcription complex that associates to compartments with a double membrane vesicle (DMV) morphology that shelters the viral genome replication. Here we have used an electron microcopy analysis to explore the antiviral effect of plitidepsin and its impact on SARS-CoV-2 replication and DMV formation on target Vero E6 cells. Results: This ultrastructural analysis allowed to recapitulate the SARS-CoV-2 infectious life cycle, where evident viral DMV formation was observed as well as viral budding events along with cell-associated viruses. However, in cells treated with plitidepsin at different non-toxic concentrations (0.2 and 0.05 μ M) there was a lack of viral DMV formation and a complete absence of viral particles. Complementary SARS-CoV-2 nucleocapsid and dsRNA immunogold labelling unambiguously confirmed the lack of viral replication in plitidepsin-treated cells. Overall, these data indicate that plitidepsin treatment abrogated the formation of DMVs, and the detection of nucleocapsid or dsRNA viral products. Conclusion: Electron microscopy ultrastructural analysis coupled to immunogold labelling of SARS-CoV-2 products offer a unique approach to understand how antivirals work. This knowledge is key to identify the mechanism of action of promising compounds interfering with host factors whose implication in strategic biological processes can be applied as pan-antiviral strategies.
ABSTRACT
Background: Although presence of SARS-CoV-2 neutralising antibodies can provide protection against development of COVID-19, how reflective circulating anti-SARS-CoV-2 antibody levels are of underlying neutralising capacity, and whether a threshold exists to predict sufficient neutralising capacity remains unclear. Methods: In plasma from individuals with PCR-confirmed COVID-19 recruited to the All Ireland Infectious Diseases Cohort Study, we measured IgG concentrations against RBD, Spike protein sub-unit 1 and 2 (S1, S2) and Nucleocapsid (NC) using multiplex electrochemiluminescence (normalised to World Health Organisation reference serum as IU/mL). Neutralising capacity was measured against live SARS-CoV-2 virus (clinical isolate 2019-nCoV/Italy-INMI1) by determining the maximum plasma dilution required to maintain 50% inhibition of infection of Vero E6 cells (50% Neutralisation Titre (NT50)), by flow cytometry-based micro-neutralisation assay. Given that the Beta SARS-CoV-2 variant of concern (VOC) reduces neutralising activity up to six fold, we estimated a NT50 of 1:1000 against wild type SARS-CoV-2 would maintain neutralising activity against VOC. We used Spearman correlation and linear regression to model relationships between NT50 and IgG concentrations. Data are presented as median (IQR) unless specified. Results: In 190 individuals (age 50 (40-64) years, 55% female, time from symptom onset 98 (35-179) days), NT50 most highly correlated with anti-RBD IgG (Rho 0.81 p<0.001, Fig 1a) compared with other IgG classes (S1;Rho 0.8, S2;0.73, NC;0.72, all p<0.001). Median RBD titre was 246 (71-662) but trended lower over time, with a median of 319 (61-1012) IU/ml at 0-90 days, 244 (86-523) IU/ml at 90-180 days and 157 (80-364) IU/ml at >180 days post symptom onset respectively (p=0.08, Fig 1b). RBD IgG titres of 476 IU/ml corresponded to a NT50 of 1:1000. Overall, RBD ≥476 IU/ml predicted NT50 ≥1:1000 with a sensitivity of 77 (95% CI 65-87)% and specificity 89 (95% CI 82-93)%. This improved in an analysis restricted to convalescent samples (>30 days post symptom onset, n=148), with a sensitivity 88% (95% CI 74-96%) and specificity 90% (95%CI 82-95%) respectively. Conclusion: In convalescent plasma, RBD IgG titres ≥476IU/mL is sensitive and specific for predicting robust underlying neutralising capacity. Further research is required to validate these findings in other cohorts and confirm these thresholds in post-vaccinated individuals.
ABSTRACT
Background: The SARS-CoV-2 pandemic has sickened over 245 million people, and has killed more than 5 million worldwide. Recent data proves that vaccinations are highly effective in preventing Covid-19 disease, however antigenic drift and other functional mutations in the virus genome reduce the efficacy of vaccines, indicating that the development of antiviral treatments remain a crucial priority. We report potent antiviral activity against SARS-CoV-2 for a promising, novel class of nitrogen-based heterocyclic compounds. Methods: 232 compounds based on the same class of nitrogen-based hetereocyclic molecules were synthesized to final purity of greater than 99%. This library was screened for antiviral phenotypes in a cytopathic effect (CPE) assay using VeroE6 cells and the SARS-CoV-2 WA1 isolate. Based on the results of the WA1 CPE screen, 47 lead candidates were structurally analyzed, and this information was utilized to design 56 additional compounds. A second antiviral CPE-based screen was performed using these 103 candidates in VeroE6 cells with the SARS-CoV-2 delta variant. Antiviral assays studying SARS-CoV-1 (Urbani) and MERS-CoV were performed in Vero 76 cells utilizing a Neutral Red cytopathic effect assay. Results: Within the same class of structurally related small molecules, we tested an initial set of 232 compounds using a CPE-based assay with VeroE6 cells and the USA/WA1 SARS-CoV-2 isolate. Of the compounds tested, 124 demonstrated potency 10 to 540-times higher than a Remdesivir control tested in parallel. Importantly, we observed no detectable toxicity for the vast majority of these compounds when tested up to a concentration of 30 μ M. The lead candidate in this screen displayed an IC50 of 0.02 μ M and a selectivity index of >1,500. Based on structural analysis of an initial 47 lead candidates, we synthesized 56 new molecules, and tested all 103 in a CPE-based assay using the delta variant, also observing efficacy against this variant of concern. Examples of this same class of compounds also display antiviral activity against SARS-CoV-1 (Urbani) and MERS-CoV in cell-based assays. Conclusion: We have identified a novel class of antiviral compounds with potent activity against SARS-CoV-2. High potency against both the early WA1 isolate and the more recent delta variant, as well as efficacy against SARS-CoV-1 and MERS-CoV, suggest that this class of antiviral compounds has pan-Coronavirus antiviral activity.