Investigating the Potential Anti-SARS-CoV-2 and Anti-MERS-CoV Activities of Yellow Necklacepod among Three Selected Medicinal Plants: Extraction, Isolation, Identification, In Vitro, Modes of Action, and Molecular Docking Studies.

The anti-MERS-CoV activities of three medicinal plants (Azadirachta indica, Artemisia judaica, and Sophora tomentosa) were evaluated. The highest viral inhibition percentage (96%) was recorded for S. tomentosa. Moreover, the mode of action for both S. tomentosa and A. judaica showed 99.5% and 92% inhibition, respectively, with virucidal as the main mode of action. Furthermore, the anti-MERS-CoV and anti-SARS-CoV-2 activities of S. tomentosa were measured. Notably, the anti-SARS-CoV-2 activity of S. tomentosa was very high (100%) and anti-MERS-CoV inhibition was slightly lower (96%). Therefore, the phytochemical investigation of the very promising S. tomentosa L. led to the isolation and structural identification of nine compounds (1-9). Then, both the CC50 and IC50 values for the isolated compounds against SARS-CoV-2 were measured. Compound 4 (genistein 4'-methyl ether) achieved superior anti-SARS-CoV-2 activity with an IC50 value of 2.13 µm. Interestingly, the mode of action of S. tomentosa against SARS-CoV-2 showed that both virucidal and adsorption mechanisms were very effective. Additionally, the IC50 values of S. tomentosa against SARS-CoV-2 and MERS-CoV were found to be 1.01 and 3.11 µg/mL, respectively. In addition, all the isolated compounds were subjected to two separate molecular docking studies against the spike (S) and main protease (Mpr°) receptors of SARS-CoV-2.

Quercitrin loaded cyclodextrin based nanosponge as a promising approach for management of lung cancer and COVID-19.

Lung cancer and pandemic acute respiratory disease, COVID-19, are examples of the most worldwide widespread diseases. The aim of the current study is to develop cyclodextrin based nanosponge (CD-NS) for loading the flavonoid drug, quercitrin (QCT). This is to improve its solubility in an attempt to enhance its activity against lung cancer as well as SARS-CoV-2 virus responsible for COVID-19. Preparation of CD-NS was performed by ultrasound-assisted synthesis method. Two CDs were employed, namely, ß cyclodextrin (ßCD) and 2-hydroxy propyl-ß-cyclodextrin (2-HPßCD) that were crosslinked with diphenyl carbonate, one at a time. QCT loaded CD-NS revealed entrapment efficiency and particle size ranged between 94.17 and 99.03% and 97.10-325.90 nm, respectively. QCT loaded 2-HPßCD-NS revealed smaller particle size compared with that of QCT loaded ßCD-NS. Zeta potential absolute values of the prepared formulations were >20 mV, indicating physically stable nanosystems. The selected formulations were investigated by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscopy which proved the formation of QCT loaded CD-NS exhibiting porous structure. QCT exhibited partial and complete amorphization in ßCD-NS and 2-HPßCD-NS, respectively. In vitro release revealed an improved release of QCT from CD-NS formulations. The biological activity of free QCT and QCT loaded CD-NS was investigated against lung cancer cell line A549 as well as SARS-CoV-2 virus. The results revealed that IC50 values of free QCT against lung cancer cell line A549 and SARS-CoV-2 were higher than those exhibited by QCT loaded CD-NS by 1.57-5.35 and 5.95-26.95 folds, respectively. QCT loaded 2-HPßCD-NS revealed enhanced in vitro release and superior biological activity compared with QCT loaded ßCD-NS.

Design, Synthesis and In Vitro Evaluation of Spirooxindole-Based Phenylsulfonyl Moiety as a Candidate Anti-SAR-CoV-2 and MERS-CoV-2 with the Implementation of Combination Studies.

The search for an effective anti-viral to inhibit COVID-19 is a challenge for the specialized scientific research community. This work investigated the anti-coronavirus activity for spirooxindole-based phenylsulfone cycloadducts in a single and combination protocols. The newly designed anti-SARS-CoV-2 therapeutics spirooxindoles synthesized by [3 + 2] cycloaddition reactions represent an efficient approach. One-pot multicomponent reactions between phenyl vinyl sulfone, substituted isatins, and amines afforded highly stereoselective anti-SARS-CoV-2 therapeutics spirooxindoles with three stereogenic centers. Herein, the newly synthesized spirooxindoles were assessed individually against the highly pathogenic human coronaviruses and proved to be highly potent and safer. Interestingly, the synergistic effect by combining the potent, tested spirooxindoles resulted in an improved antiviral activity as well as better host-cell safety. Compounds 4i and 4d represented the most potent activity against MERS-CoV with IC50 values of 11 and 23 µM, respectively. Both compounds 4c and 4e showed equipotent activity with the best IC50 against SARS-CoV-2 with values of 17 and 18 µM, respectively, then compounds 4d and 4k with IC50 values of 24 and 27 µM, respectively. Then, our attention oriented to perform a combination protocol as anti-SARS-CoV-2 for the best compounds with a different binding mode and accompanied with different pharmacophores. Combination of compound 4k with 4c and combination of compounds 4k with 4i proved to be more active and safer. Compounds 4k with 4i displayed IC50 = 3.275 µM and half maximal cytotoxic-concentration CC50 = 11832 µM. MD simulation of the most potential compounds as well as in silico ADMET properties were investigated. This study highlights the potential drug-like properties of spirooxindoles as a cocktail anti-coronavirus protocol.

Development of spiro-3-indolin-2-one containing compounds of antiproliferative and anti-SARS-CoV-2 properties.

A series of 1″-(alkylsulfonyl)-dispiro[indoline-3,2'-pyrrolidine-3',3″-piperidine]-2,4″-diones 6a‒o has been synthesized through regioselective multi-component azomethine dipolar cycloaddition reaction of 1-(alkylsulfonyl)-3,5-bis(ylidene)-piperidin-4-ones 3a‒h. X-ray diffraction studies (6b‒d,h) confirmed the structures. The majority of the synthesized analogs reveal promising antiproliferation properties against a variety of human cancer cell lines (MCF7, HCT116, A431 and PaCa2) with good selectivity index towards normal cell (RPE1). Some of the synthesized agents exhibit potent inhibitory properties against the tested cell lines with higher efficacies than the standard references (sunitinib and 5-fluorouracil). Compound 6m is the most potent. Multi-targeted inhibitory properties against EGFR and VEGFR-2 have been observed for the synthesized agents. Flow cytometry supports the antiproliferation properties and shows the tested agents as apoptosis and necrosis forming. Vero cell viral infection model demonstrates the anti-SARS-CoV-2 properties of the synthesized agents. Compound 6f is the most promising (about 3.3 and 4.8 times the potency of the standard references, chloroquine and hydroxychloroquine). QSAR models explain and support the observed biological properties.

Robust antiviral activity of commonly prescribed antidepressants against emerging coronaviruses: in vitro and in silico drug repurposing studies.

During the current coronavirus disease 2019 (COVID-19) pandemic, symptoms of depression are commonly documented among both symptomatic and asymptomatic quarantined COVID-19 patients. Despite that many of the FDA-approved drugs have been showed anti-SARS-CoV-2 activity in vitro and remarkable efficacy against COVID-19 in clinical trials, no pharmaceutical products have yet been declared to be fully effective for treating COVID-19. Antidepressants comprise five major drug classes for the treatment of depression, neuralgia, migraine prophylaxis, and eating disorders which are frequently reported symptoms in COVID-19 patients. Herein, the efficacy of eight frequently prescribed FDA-approved antidepressants on the inhibition of both SARS-CoV-2 and MERS-CoV was assessed. Additionally, the in vitro anti-SARS-CoV-2 and anti-MERS-CoV activities were evaluated. Furthermore, molecular docking studies have been performed for these drugs against the spike (S) and main protease (Mpro) pockets of both SARS-CoV-2 and MERS-CoV. Results showed that Amitriptyline, Imipramine, Paroxetine, and Sertraline had potential anti-viral activities. Our findings suggested that the aforementioned drugs deserve more in vitro and in vivo studies targeting COVID-19 especially for those patients suffering from depression.

Antiviral activity of chitosan nanoparticles encapsulating silymarin (Sil–CNPs) against SARS-CoV-2 (in silico and in vitro study)† † Electronic supplementary information (ESI) available: Table S1;residues interacting with ligands (CNPs, Sil, and RMV) in the predicted binding pockets of Hexon, ACE2, and Spike protein. Fig. S1;a schematic diagram of the chemical interaction of Sil@CNPs nanocomposite. See https://doi.org/10.1039/d2ra00905f

To develop a specific treatment against COVID-19, we investigated silymarin–chitosan nanoparticles (Sil–CNPs) as an antiviral agent against SARS-CoV-2 using in silico and in vitro approaches. Docking of Sil and CNPs was carried out against SARS-CoV-2 spike protein using AutoDock Vina. CNPs and Sil–CNPs were prepared by the ionic gelation method and characterized by TEM, FT-IR, zeta analysis, and the membrane diffusion method to determine the drug release profile. Cytotoxicity was tested on both Vero and Vero E6 cell lines using the MTT assay. Minimum binding energies with spike protein and ACE2 were −6.6, and −8.0 kcal mol−1 for CNPs, and −8.9, and −9.7 kcal mol−1 for Sil, respectively, compared to −6.6 and −8.4 kcal mol−1 respectively for remdesivir (RMV). CNPs and Sil–CNPs were prepared at sizes of 29 nm and 82 nm. The CC50 was 135, 35, and 110 μg mL−1 for CNPs, Sil, and Sil–CNPs, respectively, on Vero E6. The IC50 was determined at concentrations of 0.9, 12 and 0.8 μg mL−1 in virucidal/replication assays for CNPs, Sil, and Sil–CNPs respectively using crystal violet. These results indicate antiviral activity of Sil–CNPs against SARS-CoV-2. To develop a specific treatment against COVID-19, we investigated silymarin–chitosan nanoparticles (Sil–CNPs) as an antiviral agent against SARS-CoV-2 using in silico and in vitro approaches.

Antiviral activity of chitosan nanoparticles encapsulating silymarin (Sil-CNPs) against SARS-CoV-2 (in silico and in vitro study).

To develop a specific treatment against COVID-19, we investigated silymarin-chitosan nanoparticles (Sil-CNPs) as an antiviral agent against SARS-CoV-2 using in silico and in vitro approaches. Docking of Sil and CNPs was carried out against SARS-CoV-2 spike protein using AutoDock Vina. CNPs and Sil-CNPs were prepared by the ionic gelation method and characterized by TEM, FT-IR, zeta analysis, and the membrane diffusion method to determine the drug release profile. Cytotoxicity was tested on both Vero and Vero E6 cell lines using the MTT assay. Minimum binding energies with spike protein and ACE2 were -6.6, and -8.0 kcal mol-1 for CNPs, and -8.9, and -9.7 kcal mol-1 for Sil, respectively, compared to -6.6 and -8.4 kcal mol-1 respectively for remdesivir (RMV). CNPs and Sil-CNPs were prepared at sizes of 29 nm and 82 nm. The CC50 was 135, 35, and 110 µg mL-1 for CNPs, Sil, and Sil-CNPs, respectively, on Vero E6. The IC50 was determined at concentrations of 0.9, 12 and 0.8 µg mL-1 in virucidal/replication assays for CNPs, Sil, and Sil-CNPs respectively using crystal violet. These results indicate antiviral activity of Sil-CNPs against SARS-CoV-2.

Lipid polymer hybrid nanocarriers as a combinatory platform for different anti-SARS-CoV-2 drugs supported by computational studies† † Electronic supplementary information (ESI) available. See DOI: 10.1039/d1ra04576h

The COVID-19 pandemic caused by SARS-CoV-2 has demonstrated the potential of emergent pathogens to severely damage public health and global economies. As a consequence of the pandemic, millions of people have been forced into self-isolation, which has negatively affected the global economy. More efforts are needed to find new innovative approaches that could fundamentally change our understanding and management of this disaster. Herein, lipid polymer hybrid nanoparticles (LPH NPs) were utilized as a platform for the delivery of azithromycin or niclosamide in combination with piroxicam. The obtained systems were successfully loaded with both azithromycin and piroxicam (LPHAzi–Pir) with entrapment efficiencies (EE%) of 74.23 ± 8.14% and 51.52 ± 5.45%, respectively, or niclosamide and piroxicam (LPHNic–Pir) with respective EE% of 85.14 ± 3.47% and 48.75 ± 4.77%. The prepared LPH NPs had a core–shell nanostructure with particle size ≈ 125 nm and zeta potential ≈ −16.5 irrespective of drug payload. A dose-dependent cellular uptake of both LPH NPs was observed in human lung fibroblast cells. An enhanced in vitro antiviral efficacy of both LPHAzi–Pir and LPHNic–Pir was obtained over the mixed solution of the drugs. The LPH NPs of azithromycin or niclosamide with piroxicam displyed a promising capability to hinder the replication of SARS-CoV-2, with IC50 of 3.16 and 1.86 μM, respectively. These results provide a rationale for further in vivo pharmacological as well as toxicological studies to evaluate the potential activity of these drugs to combat the COVID-19 outbreak, especially the concept of combination therapy. Additionally, the molecular docking of macrolide bioactive compounds against papain-like protease (PDB ID:6wuu) was achieved. A ligand-based study, especially rapid overlay chemical structure (ROCS), was also examined to identify the general pharmacophoric features of these compounds and their similarity to reported anti-SARS-CoV-2 drugs. Molecular dynamic simulation was also implemented. Drug repurposing approach to combat SARS-CoV-2: lipid polymer hybrid nanoparticles (LPH) for the delivery of azithromycin or niclosamide in combination with piroxicam.

Scrutinizing the Feasibility of Nonionic Surfactants to Form Isotropic Bicelles of Curcumin: a Potential Antiviral Candidate Against COVID-19.

Investigating bicelles as an oral drug delivery system and exploiting their structural benefits can pave the way to formulate hydrophobic drugs and potentiate their activity. Herein, the ability of non-ionic surfactants (labrasol®, tween 80, cremophore EL and pluronic F127) to form curcumin loaded bicelles with phosphatidylcholine, utilizing a simple method, was investigated. Molecular docking was used to understand the mechanism of bicelles formation. The % transmittance and TEM exhibited bicelles formation with labrasol® and tween 80, while cremophor EL and pluronic F127 tended to form mixed micelles. The surfactant-based nanostructures significantly improved curcumin dissolution (99.2 ± 2.6% within 10 min in case of tween 80-based bicelles) compared to liposomes and curcumin suspension in non-sink conditions. The prepared formulations improved curcumin ex vivo permeation over liposomes and drug suspension. Further, the therapeutic antiviral activity of the formulated curcumin against SARS-CoV-2 was potentiated over drug suspension. Although both Labrasol® and tween 80 bicelles could form bicelles and enhance the oral delivery of curcumin when compared to liposomes and drug suspension, the mixed micelles formulations depicted superiority than bicelles formulations. Our findings provide promising formulations that can be utilized for further preclinical and clinical studies of curcumin as an antiviral therapy for COVID-19 patients. Graphical Abstract.

Structure- and Ligand-Based in silico Studies towards the Repurposing of Marine Bioactive Compounds to Target SARS-CoV-2.

This work was a structured virtual screening for marine bioactive compounds with reported antiviral activities which were subjected to structure-based studies against SARS-CoV-2 co-crystallized proteins. The molecular docking of marine bioactive compounds against the main protease (Mpro, PDB ID: 6lu7 and 6y2f), the spike glycoprotein (PDB ID: 6vsb), and the RNA polymerase (PDB ID: 6m71) of SARS-CoV-2 was performed. Ligand-based approach with the inclusion of rapid overlay chemical structures (ROCS) was also addressed in order to examine the probability of these marine compounds sharing relevance and druggability with the reported drugs. Among the examined marine library, the highest scores in different virtual screening aspects were displayed by compounds with flavonoids core, acyl indole, and pyrrole carboxamide alkaloids. Moreover, a complete overlay with the co-crystallized ligands of Mpro was revealed by sceptrin and debromo-sceptrin. Thalassoilin (A-B) which was found in the Red Sea exhibited the highest binding and similarity outcomes among all target proteins. These data highlight the importance of marine natural metabolites in regard to further studies for discovering new drugs to combat the COVID-19 pandemic.

New Pyrazine Conjugates: Synthesis, Computational Studies, and Antiviral Properties against SARS-CoV-2.

Currently, limited therapeutic options are available for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We have developed a set of pyrazine-based small molecules. A series of pyrazine conjugates was synthesized by microwave-assisted click chemistry and benzotriazole chemistry. All the synthesized conjugates were screened against the SAR-CoV-2 virus and their cytotoxicity was determined. Computational studies were carried out to validate the biological data. Some of the pyrazine-triazole conjugates (5 d-g) and (S)-N-(1-(benzo[d]thiazol-2-yl)-2-phenylethyl)pyrazine-2-carboxamide 12 i show significant potency against SARS-CoV-2 among the synthesized conjugates. The selectivity index (SI) of potent conjugates indicates significant efficacy compared to the reference drug (Favipiravir).

Synthesis of aspirin-curcumin mimic conjugates of potential antitumor and anti-SARS-CoV-2 properties.

Series of piperidone-salicylate conjugates were synthesized through the reaction of 3E,5E-bis(arylidene)-4-piperidones with the appropriate acid chloride of acetylsalicylate in the presence of triethylamine. All the synthesized conjugates reveal antiproliferative properties against A431 (squamous skin) cancer cell line with potency higher than that of 5-fluorouracil. Many of the synthesized agents also exhibit promising antiproliferative properties against HCT116 (colon) cancer cell line, of which 5o and 5c are the most effective with 12.9, 9.8 folds potency compared with Sunitinib. Promising activity is also shown against MCF7 (breast) cancer cell line with 1.19, 1.12 folds relative to 5-fluorouracil. PI-flow cytometry of compound 5c supports the arrest of cell cycle at G1-phase. However, compound 5o and Sunitinib arrest the cell cycle at S-phase. The synthesized conjugates can be considered as multi-targeted tyrosine kinase inhibitors due to the promising properties against VEGFR-2 and EGFR in MCF7 and HCT116. CDOCKER studies support the EGFR inhibitory properties. Compounds 5p and 5i possessing thienylidene heterocycle are anti-SARS-CoV-2 with high therapeutic indices. Many of the synthesized agents show enhanced COX-1/2 properties than aspirin with better selectivity index towards COX-2 relative to COX-1. The possible applicability of the potent candidates discovered as antitumor and anti-SARS-CoV-2 is supported by the safe profile against normal (non-cancer, RPE1 and VERO-E6) cells.

Delineating a potent antiviral activity of Cuphea ignea extract loaded nano-formulation against SARS-CoV-2: In silico and in vitro studies.

The outbreak of coronavirus disease-2019, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a worldwide emerging crisis. Polyphenols are a class of herbal metabolites with a broad-spectrum antiviral activity. However, most polyphenols encounter limited efficacy due to their poor solubility and degradation in neutral and basic environments. Thus, the effectiveness of their pharmaceutical application is critically dependent on the delivery systems to overcome the aforementioned drawbacks. Herein, Polyphenols-rich Cuphea ignea extract was prepared and its constituents were identified and quantified. Molecular docking was conducted for 15 compounds in the extract against SARS-CoV-2 main protease, among which rutin, myricetin-3-O-rhamnoside and rosmarinic acid depicted the most promising antiviral activity. Further, a self-nanoemulsifying formulation, composed of 10% oleic acid, 40% tween 20 and propylene glycol 50%, was prepared to improve the solubility of the extract components and enable its concurrent delivery permitting combined potency. Upon dilution with aqueous phases, the formulation rapidly Formsnanoemulsion of good stability and excellent dissolution profile in acidic pH when compared to the crude extract. It inhibited SARS-CoV-2 completely in vitro at a concentration as low as 5.87 µg/mL presenting a promising antiviral remedy for SARS-CoV-2, which may be attributed to the possible synergism between the extract components.

3-Alkenyl-2-oxindoles: Synthesis, antiproliferative and antiviral properties against SARS-CoV-2.

Sets of 3-alkenyl-2-oxindoles (6,10,13) were synthesized in a facile synthetic pathway through acid dehydration (EtOH/HCl) of the corresponding 3-hydroxy-2-oxoindolines (5,9,12). Single crystal (10a,c) and powder (12a,26f) X-ray studies supported the structures. Compounds 6c and 10b are the most effective agents synthesized (about 3.4, 3.3 folds, respectively) against PaCa2 (pancreatic) cancer cell line relative to the standard reference used (Sunitinib). Additionally, compound 10b reveals antiproliferative properties against MCF7 (breast) cancer cell with IC50 close to that of Sunitinib. CAM testing reveals that compounds 6 and 10 demonstrated qualitative and quantitative decreases in blood vessel count and diameter with efficacy comparable to that of Sunitinib, supporting their anti-angiogenic properties. Kinase inhibitory properties support their multi-targeted inhibitory activities against VEGFR-2 and c-kit in similar behavior to that of Sunitinib. Cell cycle analysis studies utilizing MCF7 exhibit that compound 6b arrests the cell cycle at G1/S phase while, 10b reveals accumulation of the tested cell at S phase. Compounds 6a and 10b reveal potent antiviral properties against SARS-CoV-2 with high selectivity index relative to the standards (hydroxychloroquine, chloroquine). Safe profile of the potent synthesized agents, against normal cells (VERO-E6, RPE1), support the possible development of better hits based on the attained observations.

New quinoline-triazole conjugates: Synthesis, and antiviral properties against SARS-CoV-2.

At present therapeutic options for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are very limited. We designed and synthesized three sets of small molecules using quinoline scaffolds. A series of quinoline conjugates (10a-l, 11a-c, and 12a-e) by incorporating 1,2,3-triazole were synthesized via a modified microwave-assisted click chemistry technique. Among the synthesized conjugates, 4-((1-(2-chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-6-fluoro-2-(trifluoromethyl)quinoline (10g) and 6-fluoro-4-(2-(1-(4-methoxyphenyl)-1H-1,2,3-triazol-4-yl)ethoxy)-2-(trifluoromethyl)quinoline (12c) show high potency against SARS-CoV-2. The selectivity index (SI) of compounds 10g and 12c also indicates the significant efficacy compared to the reference drugs.

Bioactive Polyphenolic Compounds Showing Strong Antiviral Activities against Severe Acute Respiratory Syndrome Coronavirus 2.

Until now, there has been no direct evidence of the effectiveness of repurposed FDA-approved drugs against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections. Although curcumin, hesperidin, and quercetin have broad spectra of pharmacological properties, their antiviral activities against SARS-CoV-2 remain unclear. Our study aimed to assess the in vitro antiviral activities of curcumin, hesperidin, and quercetin against SARS-CoV-2 compared to hydroxychloroquine and determine their mode of action. In Vero E6 cells, these compounds significantly inhibited virus replication, mainly as virucidal agents primarily indicating their potential activity at the early stage of viral infection. To investigate the mechanism of action of the tested compounds, molecular docking studies were carried out against both SARS-CoV-2 spike (S) and main protease (Mpro) receptors. Collectively, the obtained in silico and in vitro findings suggest that the compounds could be promising SARS-CoV-2 Mpro inhibitors. We recommend further preclinical and clinical studies on the studied compounds to find a potential therapeutic targeting COVID-19 in the near future.

Cnicin as an Anti-SARS-CoV-2: An Integrated In Silico and In Vitro Approach for the Rapid Identification of Potential COVID-19 Therapeutics.

Since the emergence of the SARS-CoV-2 pandemic in 2019, it has remained a significant global threat, especially with the newly evolved variants. Despite the presence of different COVID-19 vaccines, the discovery of proper antiviral therapeutics is an urgent necessity. Nature is considered as a historical trove for drug discovery, especially in global crises. During our efforts to discover potential anti-SARS CoV-2 natural therapeutics, screening our in-house natural products and plant crude extracts library led to the identification of C. benedictus extract as a promising candidate. To find out the main chemical constituents responsible for the extract's antiviral activity, we utilized recently reported SARS CoV-2 structural information in comprehensive in silico investigations (e.g., ensemble docking and physics-based molecular modeling). As a result, we constructed protein-protein and protein-compound interaction networks that suggest cnicin as the most promising anti-SARS CoV-2 hit that might inhibit viral multi-targets. The subsequent in vitro validation confirmed that cnicin could impede the viral replication of SARS CoV-2 in a dose-dependent manner, with an IC50 value of 1.18 µg/mL. Furthermore, drug-like property calculations strongly recommended cnicin for further in vivo and clinical experiments. The present investigation highlighted natural products as crucial and readily available sources for developing antiviral therapeutics. Additionally, it revealed the key contributions of bioinformatics and computer-aided modeling tools in accelerating the discovery rate of potential therapeutics, particularly in emergency times like the current COVID-19 pandemic.

Incidence, household transmission, and neutralizing antibody seroprevalence of Coronavirus Disease 2019 in Egypt: Results of a community-based cohort.

SARS-CoV-2 virus is transmitted in closed settings to people in contact with COVID-19 patients such as healthcare workers and household contacts. However, household person-to-person transmission studies are limited. Households participating in an ongoing cohort study of influenza incidence and prevalence in rural Egypt were followed. Baseline enrollment was done from August 2015 to March 2017. The study protocol was amended in April 2020 to allow COVID-19 incidence and seroprevalence studies. A total of 290 households including 1598 participants were enrolled and followed from April to October 2020 in four study sites. When a participant showed respiratory illness symptoms, a serum sample and a nasal and an oropharyngeal swab were obtained. Swabs were tested by RT-PCR for SARS-CoV-2 infection. If positive, the subject was followed and swabs collected on days three, six, nine, and 14 after the first swab day and a serum sample obtained on day 14. All subjects residing with the index case were swabbed following the same sampling schedule. Sera were collected from cohort participants in October 2020 to assess seroprevalence. Swabs were tested by RT-PCR. Sera were tested by Microneutralization Assay to measure the neutralizing antibody titer. Incidence of COVID-19, household secondary attack rate, and seroprevalence in the cohort were determined. The incidence of COVID-19 was 6.9% and the household secondary attack rate was 89.8%. Transmission within households occurred within two-days of confirming the index case. Infections were asymptomatic or mild with symptoms resolving within 10 days. The majority developed a neutralizing antibody titer by day 14 post onset. The overall seroprevalence among cohort participants was 34.8%. These results suggest that within-household transmission is high in Egypt. Asymptomatic or mild illness is common. Most infections seroconvert and have a durable neutralizing antibody titer.

Immunogenicity and Safety of an Inactivated SARS-CoV-2 Vaccine: Preclinical Studies.

Since the emergence of SARS-CoV-2 at the end of 2019, 64 candidate vaccines are in clinical development and 173 are in the pre-clinical phase. Five types of vaccines are currently approved for emergency use in many countries (Inactivated, Sinopharm; Viral-vector, Astrazeneca, and Gamaleya Research Institute; mRNA, Moderna, and BioNTech/Pfizer). The main challenge in this pandemic was the availability to produce an effective vaccine to be distributed to the world's population in a short time. Herein, we developed a whole virus NRC-VACC-01 inactivated candidate SARS-CoV-2 vaccine and tested its safety and immunogenicity in laboratory animals. In the preclinical studies, we used four experimental animals (mice, rats, guinea pigs, and hamsters). Antibodies were detected as of week three post vaccination and continued up to week ten in the four experimental models. Safety evaluation of NRC-VACC-01 inactivated candidate vaccine in rats revealed that the vaccine was highly tolerable. By studying the effect of booster dose in the immunological profile of vaccinated mice, we observed an increase in neutralizing antibody titers after the booster shot, thus a booster dose was highly recommended after week three or four. Challenge infection of hamsters showed that the vaccinated group had lower morbidity and shedding than the control group. A phase I clinical trial will be performed to assess safety in human subjects.

Prevalence of Severe Acute Respiratory Syndrome Coronavirus 2 Neutralizing Antibodies in Egyptian Convalescent Plasma Donors.

Using convalescent plasma as immunotherapy is an old method for treatment of infectious diseases. Several countries have recently allowed the use of such therapy for the treatment of COVID-19 patients especially those who are critically ill. A similar program is currently being tested in Egypt. Here, we tested 227 plasma samples from convalescent donors in Egypt for neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using a microneutralization (MN) assay. A third of the tested samples did not have antibody titers and 58% had titers between 1:10 and 1:80. Only 12% had titers >1:160. We also compared MN assays using different virus concentrations, plaque reduction neutralization (PRNT) assays, and a chemiluminescence assay that measures immunoglobulin G (IgG) binding to N and S proteins of SARS-CoV-2. Our results indicated that a MN assay using 100 TCID50/ml provides comparable results to PRNT and allows for high throughput testing.