Nsp1 facilitates SARS-CoV-2 replication through calcineurin-NFAT signaling

SARS-CoV-2, the causative agent of COVID-19, has been intensely studied in search of effective antiviral treatments. The immunosuppressant cyclosporine A (CsA) has been suggested to be a pan-coronavirus inhibitor, yet its underlying mechanism remained largely unknown. Here, we found that non-structural protein 1 (Nsp1) of SARS-CoV-2 usurped CsA-suppressed nuclear factor of activated T cells (NFAT) signaling to drive the expression of cellular DEAD-box helicase 5 (DDX5), which facilitates viral replication. Nsp1 interacted with calcineurin A (CnA) to displace the regulatory protein regulator of calcineurin 3 (RCAN3) of CnA for NFAT activation. The influence of NFAT activation on SARS-CoV-2 replication was also validated by using the Nsp1-deficient mutant virus. Calcineurin inhibitors, such as CsA and VIVIT, inhibited SARS-CoV-2 replication and exhibited synergistic antiviral effects when used in combination with nirmatrelvir. Our study delineated the molecular mechanism of CsA-mediated inhibition of SARS-CoV-2 replication and the anti-SARS-CoV-2 action of calcineurin inhibitors.

IMPORTANCE

Cyclosporine A (CsA), commonly used to inhibit immune responses, is also known to have anti-SARS-CoV-2 activity, but its mode of action remains elusive. Here, we provide a model to explain how CsA antagonizes SARS-CoV-2 through three critical proteins: DDX5, NFAT1, and Nsp1. DDX5 is a cellular facilitator of SARS-CoV-2 replication, and NFAT1 controls the production of DDX5. Nsp1 is a viral protein absent from the mature viral particle and capable of activating the function of NFAT1 and DDX5. CsA and similar agents suppress Nsp1, NFAT1, and DDX5 to exert their anti-SARS-CoV-2 activity either alone or in combination with Paxlovid.

Development of Pan-Anti-SARS-CoV-2 Agents through Allosteric Inhibition of nsp14/nsp10 Complex

SARS-CoV-2 nsp14 functions both as an exoribonuclease (ExoN) together with its critical cofactor nsp10 and as an S-adenosyl methionine-dependent (guanine-N7) methyltransferase (MTase), which makes it an attractive target for the development of pan-anti-SARS-CoV-2 drugs. Herein, we screened a panel of compounds (and drugs) and found that certain compounds, especially Bi(III)-based compounds, could allosterically inhibit both MTase and ExoN activities of nsp14 potently. We further demonstrated that Bi(III) binds to both nsp14 and nsp10, resulting in the release of Zn(II) ions from the enzymes as well as alternation of protein quaternary structures. The in vitro activities of the compounds were also validated in SARS-CoV-2-infected mammalian cells. Importantly, we showed that nsp14 serves as an authentic target of Bi(III)-based antivirals in SARS-CoV-2-infected mammalian cells by quantification of both the protein and inhibitor. This study highlights the importance of nsp14/nsp10 as a potential target for the development of pan-antivirals against SARS-CoV-2 infection.

Monovalent vaccination with inactivated SARS-CoV-2 BA.5 protects hamsters against Omicron but not non-Omicron variants

We compared the protective effects of inactivated SARS-CoV-2 vaccines derived from the ancestral and the currently circulating BA.5.2 strains against infection with multiple variants in Syrian golden hamsters. Vaccination with BA.5.2 effectively protected against infection with the Omicron subvariants including XBB.1, but not the Alpha or Delta variant. In contrast, hamsters vaccinated with the ancestral strain demonstrated decent neutralization activity against both the Omicron and non-Omicron variants. Our findings might instruct future design and formulation of SARS-CoV-2 vaccines.

Comparative analysis of SARS-CoV-2 Omicron BA.2.12.1 and BA.5.2 variants

The initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants, BA.1 and BA.2, are being progressively displaced by BA.5 in many countries. To provide insight on the replacement of BA.2 by BA.5 as the dominant SARS-CoV-2 variant, we performed a comparative analysis of Omicron BA.2.12.1 and BA.5.2 variants in cell culture and hamster models. We found that BA.5.2 exhibited enhanced replicative kinetics over BA.2.12.1 in vitro and in vivo, which is evidenced by the dominant BA.5.2 viral genome detected at different time points, regardless of immune selection pressure with vaccine-induced serum antibodies. Utilizing reverse genetics, we constructed a mutant SARS-CoV-2 carrying spike F486V substitution, which is an uncharacterized mutation that concurrently discriminates Omicron BA.5.2 from BA.2.12.1 variant. We noticed that the 486th residue does not confer viral replication advantage to the virus. We also found that 486V displayed generally reduced immune evasion capacity when compared with its predecessor, 486F. However, the surge of fitness in BA.5.2 over BA.2.12.1 was not due to stand-alone F486V substitution but as a result of the combination of multiple mutations. Our study upholds the urgency for continuous monitoring of SARS-CoV-2 Omicron variants with enhanced replication fitness.

Human early syncytiotrophoblasts are highly susceptible to SARS-CoV-2 infection

Direct in vivo investigation of human placenta trophoblast's susceptibility to SARS-CoV-2 is challenging. Here we report that human trophoblast stem cells (hTSCs) and their derivatives are susceptible to SARS-CoV-2 infection, which reveals heterogeneity in hTSC cultures. Early syncytiotrophoblasts (eSTBs) generated from hTSCs have enriched transcriptomic features of peri-implantation trophoblasts, express high levels of angiotensin-converting enzyme 2 (ACE2), and are productively infected by SARS-CoV-2 and its Delta and Omicron variants to produce virions. Antiviral drugs suppress SARS-CoV-2 replication in eSTBs and antagonize the virus-induced blockage of STB maturation. Although less susceptible to SARS-CoV-2 infection, trophoblast organoids originating from hTSCs show detectable viral replication reminiscent of the uncommon placental infection. These findings implicate possible risk of COVID-19 infection in peri-implantation embryos, which may go unnoticed. Stem cell-derived human trophoblasts such as eSTBs can potentially provide unlimited amounts of normal and genome-edited cells and facilitate coronavirus research and antiviral discovery.

Production of single-cycle infectious SARS-CoV-2 through a trans-complemented replicon

Single-cycle infectious virus can elicit close-to-natural immune response and memory. One approach to generate single-cycle severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is through deletion of structural genes such as spike (S) and nucleocapsid (N). Transcomplementation of the resulting ΔS or ΔN virus through enforced expression of S or N protein in the cells gives rise to a live but unproductive virus. In this study, ΔS and ΔN BAC clones were constructed and their live virions were rescued by transient expression of S and N proteins from the ancestral and the Omicron strains. ΔS and ΔN virions were visualized by transmission electron microscopy. Virion production of ΔS was more efficient than that of ΔN. The coated S protein from ΔS was delivered to infected cells in which the expression of N protein was also robust. In contrast, expression of neither S nor N was detected in ΔN-infected cells. ΔS underwent viral RNA replication, induced type I interferon (IFN) response, but did not form plaques. Despite RNA replication in cells, ΔS infection did not produce viral progeny in culture supernatant. Interestingly, viral RNA replication was not further enhanced upon overexpression of S protein. Taken together, our work provides a versatile platform for development of single-cycle vaccines for SARS-CoV-2.

The spike receptor-binding motif G496S substitution determines the replication fitness of SARS-CoV-2 Omicron sublineage

AbstractThe replication and pathogenicity of SARS-CoV-2 Omicron BA.2 is comparable to that of BA.1 in experimental animal models. However, BA.2 has rapidly emerged to overtake BA.1 to become the predominant circulating SARS-CoV-2 variant worldwide. Here, we compared the replication fitness of BA.1 and BA.2 in cell culture and in the Syrian hamster model of COVID-19. Using a reverse genetics approach, we found that the BA.1-specific spike mutation G496S compromises its replication fitness, which may contribute to BA.1 being outcompeted by BA.2 in the real world. Additionally, the BA.1-unique G496S substitution confers differentiated sensitivity to therapeutic monoclonal antibodies, which partially recapitulates the immunoevasive phenotype of BA.1 and BA.2. In summary, our study identified G496S as an important determinant during the evolutionary trajectory of SARS-CoV-2.

Cross-variant protection against SARS-CoV-2 infection in hamsters immunized with monovalent and bivalent inactivated vaccines

Rapid development and successful use of vaccines against SARS-CoV-2 might hold the key to curb the ongoing pandemic of COVID-19. Emergence of vaccine-evasive SARS-CoV-2 variants of concern (VOCs) has posed a new challenge to vaccine design and development. One urgent need is to determine what types of variant-specific and bivalent vaccines should be developed. Here, we compared homotypic and heterotypic protection against SARS-CoV-2 infection of hamsters with monovalent and bivalent whole-virion inactivated vaccines derived from representative VOCs. In addition to the ancestral SARS-CoV-2 Wuhan strain, Delta (B.1.617.2; δ) and Theta (P.3; θ) variants were used in vaccine preparation. Additional VOCs including Omicron (B.1.1.529) and Alpha (B.1.1.7) variants were employed in the challenge experiment. Consistent with previous findings, Omicron variant exhibited the highest degree of immune evasion, rendering all different forms of inactivated vaccines substantially less efficacious. Notably, monovalent and bivalent Delta variant-specific inactivated vaccines provided optimal protection against challenge with Delta variant. Yet, some cross-variant protection against Omicron and Alpha variants was seen with all monovalent and bivalent inactivated vaccines tested. Taken together, our findings support the notion that an optimal next-generation inactivated vaccine against SARS-CoV-2 should contain the predominant VOC in circulation. Further investigations are underway to test whether a bivalent vaccine for Delta and Omicron variants can serve this purpose.

Pathogenicity, transmissibility, and fitness of SARS-CoV-2 Omicron in Syrian hamsters

The in vivo pathogenicity, transmissibility, and fitness of the SARS-CoV-2 Omicron (B.1.1.529) variant are unclear. We compared these virological attributes of this new variant of concern with those of the Delta (B.1.617.2) variant in a Syrian hamster model of COVID-19. Omicron-infected hamsters lost significantly less body weight and exhibited reduced clinical scores, respiratory tract viral burdens, cytokine/chemokine dysregulation, and lung damage than Delta-infected hamsters. Both variants were highly transmissible via contact transmission. In non-contact transmission studies, Omicron demonstrated similar or higher transmissibility than Delta. Delta outcompeted Omicron without selection pressure. This scenario drastically changed once immune selection pressure with neutralizing antibodies active against Delta but poorly active against Omicron was introduced. Next-generation vaccines and antivirals effective against this new VOC are urgently needed.

Intranasal administration of a single dose of a candidate live attenuated vaccine derived from an NSP16-deficient SARS-CoV-2 strain confers sterilizing immunity in animals

Live attenuated vaccines might elicit mucosal and sterilizing immunity against SARS-CoV-2 that the existing mRNA, adenoviral vector and inactivated vaccines fail to induce. Here, we describe a candidate live attenuated vaccine strain of SARS-CoV-2 in which the NSP16 gene, which encodes 2′-O-methyltransferase, is catalytically disrupted by a point mutation. This virus, designated d16, was severely attenuated in hamsters and transgenic mice, causing only asymptomatic and nonpathogenic infection. A single dose of d16 administered intranasally resulted in sterilizing immunity in both the upper and lower respiratory tracts of hamsters, thus preventing viral spread in a contact-based transmission model. It also robustly stimulated humoral and cell-mediated immune responses, thus conferring full protection against lethal challenge with SARS-CoV-2 in a transgenic mouse model. The neutralizing antibodies elicited by d16 effectively cross-reacted with several SARS-CoV-2 variants. Secretory immunoglobulin A was detected in the blood and nasal wash of vaccinated mice. Our work provides proof-of-principle evidence for harnessing NSP16-deficient SARS-CoV-2 for the development of live attenuated vaccines and paves the way for further preclinical studies of d16 as a prototypic vaccine strain, to which new features might be introduced to improve safety, transmissibility, immunogenicity and efficacy.

Beneficial effect of combinational methylprednisolone and remdesivir in hamster model of SARS-CoV-2 infection

Effective treatments for coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are urgently needed. Dexamethasone has been shown to confer survival benefits to certain groups of hospitalized patients, but whether glucocorticoids such as dexamethasone and methylprednisolone should be used together with antivirals to prevent a boost of SARS-CoV-2 replication remains to be determined. Here, we show the beneficial effect of methylprednisolone alone and in combination with remdesivir in the hamster model of SARS-CoV-2 infection. Treatment with methylprednisolone boosted RNA replication of SARS-CoV-2 but suppressed viral induction of proinflammatory cytokines in human monocyte-derived macrophages. Although methylprednisolone monotherapy alleviated body weight loss as well as nasal and pulmonary inflammation, viral loads increased and antibody response against the receptor-binding domain of spike protein attenuated. In contrast, a combination of methylprednisolone with remdesivir not only prevented body weight loss and inflammation, but also dampened viral protein expression and viral loads. In addition, the suppressive effect of methylprednisolone on antibody response was alleviated in the presence of remdesivir. Thus, combinational anti-inflammatory and antiviral therapy might be an effective, safer and more versatile treatment option for COVID-19. These data support testing of the efficacy of a combination of methylprednisolone and remdesivir for the treatment of COVID-19 in randomized controlled clinical trials.

Honokiol: A Review of Its Anticancer Potential and Mechanisms

Cancer is characterised by uncontrolled cell division and abnormal cell growth, which is largely caused by a variety of gene mutations. There are continuous efforts being made to develop effective cancer treatments as resistance to current anticancer drugs has been on the rise. Natural products represent a promising source in the search for anticancer treatments as they possess unique chemical structures and combinations of compounds that may be effective against cancer with a minimal toxicity profile or few side effects compared to standard anticancer therapy. Extensive research on natural products has shown that bioactive natural compounds target multiple cellular processes and pathways involved in cancer progression. In this review, we discuss honokiol, a plant bioactive compound that originates mainly from the Magnolia species. Various studies have proven that honokiol exerts broad-range anticancer activity in vitro and in vivo by regulating numerous signalling pathways. These include induction of G0/G1 and G2/M cell cycle arrest (via the regulation of cyclin-dependent kinase (CDK) and cyclin proteins), epithelial-mesenchymal transition inhibition via the downregulation of mesenchymal markers and upregulation of epithelial markers. Additionally, honokiol possesses the capability to supress cell migration and invasion via the downregulation of several matrix-metalloproteinases (activation of 5' AMP-activated protein kinase (AMPK) and KISS1/KISS1R signalling), inhibiting cell migration, invasion, and metastasis, as well as inducing anti-angiogenesis activity (via the down-regulation of vascular endothelial growth factor (VEGFR) and vascular endothelial growth factor (VEGF)). Combining these studies provides significant insights for the potential of honokiol to be a promising candidate natural compound for chemoprevention and treatment.

Malignant peripheral nerve sheath tumor mimicking carotid body tumor--case report and review

Malignant peripheral nerve sheath tumor is a rare neurogenic tumor that usually presents in geriatic patients. Typically, it is found in the trunk and extremities and rarely presents in the head and neck region. It may mimic a carotid body tumor when it presents in the neck. We report the first case of malignant peripheral nerve sheath tumor of the vagus nerve in an adolescent boy. He presented with an asymptomatic lateral neck lump that was thought to be a benign schwannoma on preoperative imaging. We describe the diagnostic dilemma and management difficulties in this patient and review the literature.

Determination of pharmaceuticals and related impurities by capillary electrophoresis

In the first part of this work, the use of capillary electrophoresis (CE) for the separation of two groups of pharmaceuticals, namely a metabolite of tamoxifen and a basic drug substance, DS1 was investigated. The effects of pH and types of modifiers, e.g. surfactant, bile salt, gamma-cyclodextrin and hydroxypropyl-beta-cyclodextrin on selectivity, separation and peak shape were studied. Besides achieving complete separation of the compounds, the CE system was capable of providing separation with significant improvements in overall peak shape of the compounds compared with HPLC. In the case of the basic drug substance DS1, validation of the CE system developed in terms of linearity, selectivity, sensitivity and reproducibility was satisfactorily performed. At the same time, a study of the sample solvent matrix effects on the separation of this group of compounds was examined. The system was successfully applied to the analysis of laboratory-synthesized samples. Good correlation was observed between CE and HPLC, although higher efficiency and faster speed of separation were obtained using the CE system developed. For the tamoxifen metabolite, special emphasis was placed on the use of CE for the separation of the pair of isomers. This was readily achieved through the introduction of gamma-cyclodextrin in the electrolyte. Resolution of at least 1.5 was obtained for the isomers using the CE method.

The use of mixed surfactants in micellar electrokinetic chromatography

The use of mixed surfactants for the separation of nine phenylthiohydantoin amino acids (PTH amino acids) by micellar electrokinetic chromatography (MEKC) was examined. The potential of a mixed surfactant system, consisting of cationic and anionic surfactants, for enhancing the selectivity of MEKC separations was explored. Both sodium dodecyl sulfate (SDS) and cetyltrime-thylammonium bromide (CTAB) in the electrophoretic medium were found to improve the separation of the PTH-amino acids compared to the use of CTAB or SDS alone. Complete separation of the PTH amino acids was achieved using a buffer containing 2.5 mM CTAB and 40 mM SDS. The analysis was performed without the need to reverse the polarity of the electrodes, typically required if oppositely charged micelles are used. The migration behavior of the nine PTH amino acids using the mixed surfactant system was compared with MEKC in presence of SDS alone.

High density cultivation of hybridoma in charged porous carriers

A porous carrier whose surface is charged with polyethyleneimine (PEI) was evaluated for high-density cultivation of immobilized hybridoma cells. The carrier was used either in suspension or in fixed bed. For suspended carriers, the effect of carrier pore size, ion-exchange capacity (IEC), mixing intensity and inoculum concentration on the attachment and growth of HBs MAb-producing hybridoma cells in carrier CELLSNOW EX were studied. The carrier with 100 microns pore size was more efficient than that with 500 microns in supporting cell attachment. In addition, the amount of antibody which was detected by PHA (passive hemagglutination assay) was 4-times higher in 100 microns compared with 500 microns pore size. At low initial cell concentration, 2.8 x 10(5) ml-1, the attached cells did not grow in the first 7 d as indicated by a negligible glucose consumption. However, cell proliferation was observed at high inoculum, 9 x 10(5) ml-1. Hybridoma cells were expected to attach faster to EX with high IEC than with low IEC but results showed no significant difference. A different hybridoma cell line producing monoclonal antibody (MAb) against penicillin-G-amidase was successfully cultivated in an axial-flow fixed bed containing CELLSNOW carriers. The specific glucose uptake rate as an indicator for cell activity was 24-times higher compared with conventional chemostat cultures. The CELLSNOW carriers offers many advantages over other carriers.

Determination of antihistamines in pharmaceuticals by capillary electrophoresis

Capillary electrophoresis with on-column UV detection at 214 nm was used to separate a group of nine antihistamines. All these compounds were satisfactorily separated within ca. 6 min using a mixed carrier system containing sodium dodecyl sulphate with beta-cyclodextrin and tetrabutylammonium hydrogensulphate as modifiers. The application of the method to the determination of the amount of antihistamines present in commercial pharmaceutical samples was demonstrated. In addition, the migration behaviour of the antihistamines in the mixed carrier system was examined.

An optimization procedure for the isocratic high-performance liquid chromatographic separations of environmental pollutants

This paper describes the use of the overlapping resolution mapping procedure to optimize the separation of priority pollutants by isocratic, reversed-phase high-performance liquid chromatography. Three classes of pollutants are considered: polycyclic aromatic hydrocarbons, substituted phenols and phthalate esters. The procedure requires only seven chromatographic runs for each set of pollutants before an optimized mobile phase composition is derived which can satisfactorily resolve all the components in the respective mixtures of pollutants. The main advantage of such a systematic scheme to optimize mobile phase compositions is an improvement in method development times compared to conventional techniques. Another benefit is that expenditures on solvents are reduced.

Direct coupling of supercritical fluid extraction-supercritical fluid chromatography for the determination of selected polycyclic aromatic hydrocarbons in aqueous environmental samples

A rapid and simple method is described for the quantitative determination of polycyclic aromatic hydrocarbons in aqueous environmental samples. A microscale on-line supercritical fluid extraction-supercritical fluid chromatography system using carbon dioxide is employed. The extract is analysed using capillary supercritical fluid chromatography with UV detection. Detection was carried out at 254 nm. An extraction efficiency of as high as 91% was obtained for the PAHs.

Separation of selected PAHs by using high performance capillary electrophoresis with modifiers

The effect of varying SDS concentration in a micellar electrokinetic capillary chromatographic system (MECC) is investigated. In addition, the introduction of γ-cyclodextrin as modifier to the electrophoretic medium, containing SDS and a phosphate-borate buffer, is shown to give satisfactory separation of the seven selected PAHs. The separation efficiency is increased with the addition of γ-cyclodextrin.

Optimization of the gradient HPLC separation of selected phthalates using the overlapping resolution mapping technique

Optimization procedures for the reversed-phase separations of six phthalates using the isoselective multisolvent gradient elution (IMGE) system are described. A systematic experimental design has been employed to gather retention data on the compounds in a mixture. The data were then fitted into a second-order polynomial equation and an overlapping resolution mapping (ORM) technique of data analysis was subsequently used to establish the optimum solvent mixture for the highest resolution of all adjacent peaks in the chromatogram.

Analysis of priority substituted phenols by micellar electrokinetic chromatography

The use of micellar electrokinetic capillary chromatography (MECC) for the separation of eleven substituted phenols listed by the United States Environmental Protection Agency as priority pollutants was demonstrated. The effects of the pH and ionic strength of the buffer, and the length of the separation column on resolution were investigated. The retention characteristics of the eleven phenols in MECC are discussed.

Some applications of Freon-22 in supercritical fluid chromatographic analysis of environmental pollutants

The applications of Freon-22 (R22) as a mobile phase and as a modifier in supercritical fluid chromatography were investigated. For the purpose of this investigation, the separation of eleven phenols listed by the United States Environmental Protection Agency as priority pollutants was studied. It was found that the use of neat R22 greatly reduced the retention times of the phenols compared with the use of neat carbon dioxide as mobile phase. Satisfactory separation of all the eleven phenols could be achieved using 5% R22 as modifier in carbon dioxide. The promising results obtained in this preliminary investigation indicate the potential for the use of R22 in supercritical fluid separation processes.

Retention of eleven priority phenols using micellar electrokinetic chromatography

The use of micellar electrokinetic chromatography (MECC) for the separation of eleven substituted phenols listed by the United States Environmental Protection Agency as priority pollutants was investigated. Solutions of potassium and sodium dodecyl sulphate in phosphate-borate buffer of pH 6.6, 7.0 and 7.5 were used as the electrophoretic media. Satisfactory separation of the eleven phenols was obtained using a 180-microns capillary at 10 kV and pH 6.6 with a solution containing both sodium and potassium dodecyl sulphate. Observations on the retention behaviour of the phenols in MECC were related to their physico-chemical properties.

Supercritical fluid extraction and chromatography of cholesterol in food samples

A method based on supercritical fluid chromatography is presented which can be used for the determination of cholesterol in certain foods. The method involves the extraction with supercritical carbon dioxide and analysis of the extracts using a capillary column with supercritical carbon dioxide as mobile phase and flame ionization detection. Quantification is achieved using cholesteryl chloroacetate as an internal standard.