Gene-Delivery Ability of New Hydrogenated and Partially Fluorinated Gemini bispyridinium Surfactants with Six Methylene Spacers.

The pandemic emergency determined by the spreading worldwide of the SARS-CoV-2 virus has focused the scientific and economic efforts of the pharmaceutical industry and governments on the possibility to fight the virus by genetic immunization. The genetic material must be delivered inside the cells by means of vectors. Due to the risk of adverse or immunogenic reaction or replication connected with the more efficient viral vectors, non-viral vectors are in many cases considered as a preferred strategy for gene delivery into eukaryotic cells. This paper is devoted to the evaluation of the gene delivery ability of new synthesized gemini bis-pyridinium surfactants with six methylene spacers, both hydrogenated and fluorinated, in comparison with compounds with spacers of different lengths, previously studied. Results from MTT proliferation assay, electrophoresis mobility shift assay (EMSA), transient transfection assay tests and atomic force microscopy (AFM) imaging confirm that pyridinium gemini surfactants could be a valuable tool for gene delivery purposes, but their performance is highly dependent on the spacer length and strictly related to their structure in solution. All the fluorinated compounds are unable to transfect RD-4 cells, if used alone, but they are all able to deliver a plasmid carrying an enhanced green fluorescent protein (EGFP) expression cassette, when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE) in a 1:2 ratio. The fluorinated compounds with spacers formed by six (FGP6) and eight carbon atoms (FGP8) give rise to a very interesting gene delivery activity, greater to that of the commercial reagent, when formulated with DOPE. The hydrogenated compound GP16_6 is unable to sufficiently compact the DNA, as shown by AFM images.

EGF domain peptide of Developmentally regulated endothelial locus1 facilitates gene expression of extracellularly applied plasmid DNA.

BACKGROUND: The successful development of messenger RNA vaccines for SARS-CoV-2 opened up venues for clinical nucleotide-based vaccinations. For development of DNA vaccines, we tested whether the EGF domain peptide of Developmentally regulated endothelial locus1 (E3 peptide) enhances uptake of extracellularly applied plasmid DNA. METHODS: DNA plasmid encoding lacZ or GFP was applied with a conditioned culture medium containing E3 peptide to cell lines in vitro or mouse soleus muscles in vivo, respectively. After 48 h incubation, gene expression was examined by ß-galactosidase (ß-gal) assay and fluorescent microscope, respectively. RESULTS: Application of E3 peptide-containing medium to cultured cell lines induced intense ß-gal activity in a dose-dependent manner. Intra-gastrocnemius injection of E3 peptide-containing medium to mouse soleus muscle succeeded in the induction of GFP fluorescence in many cells around the injection site. CONCLUSIONS: The administration of E3 peptide facilitates transmembrane uptake of extracellular DNA plasmid which induces sufficient extrinsic gene expression.

Producing molecular biology reagents without purification.

We recently developed 'cellular' reagents-lyophilized bacteria overexpressing proteins of interest-that can replace commercial pure enzymes in typical diagnostic and molecular biology reactions. To make cellular reagent technology widely accessible and amenable to local production with minimal instrumentation, we now report a significantly simplified method for preparing cellular reagents that requires only a common bacterial incubator to grow and subsequently dry enzyme-expressing bacteria at 37°C with the aid of inexpensive chemical desiccants. We demonstrate application of such dried cellular reagents in common molecular and synthetic biology processes, such as PCR, qPCR, reverse transcription, isothermal amplification, and Golden Gate DNA assembly, in building easy-to-use testing kits, and in rapid reagent production for meeting extraordinary diagnostic demands such as those being faced in the ongoing SARS-CoV-2 pandemic. Furthermore, we demonstrate feasibility of local production by successfully implementing this minimized procedure and preparing cellular reagents in several countries, including the United Kingdom, Cameroon, and Ghana. Our results demonstrate possibilities for readily scalable local and distributed reagent production, and further instantiate the opportunities available via synthetic biology in general.

An easy method for developing fusion enabled SARS-CoV2 virus fusion mimic (SCFM), bypassing the need of Bio Safety Level (BSL) facility.

Widespread infection due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has led to a global pandemic. Currently, various approaches are being taken up to develop vaccines and therapeutics to treat SARS-CoV2 infection. Consequently, the S protein has become an important target protein for developing vaccines and therapeutics against SARS-CoV2. However, the highly infective nature of SARS-CoV2 restricts experimentation with the virus to highly secure BSL3 facilities. The availability of fusion-enabled, nonreplicating, and nonbiohazardous mimics of SARS-CoV2 virus fusion, containing the viral S or S and M protein in their native conformation on mammalian cells, can serve as a useful substitute for studying viral fusion for testing various inhibitors of viral fusion. This would avoid the use of the BSL3 facility for fusion studies required to develop therapeutics. In the present study, we have developed SARS-CoV2 virus fusion mimics (SCFMs) using mammalian cells transfected with constructs coding for S or S and M protein. The fusogenic property of the mimic(s) and their interaction with the functional human ACE2 receptors was confirmed experimentally. We have also shown that such mimics can easily be used in an inhibition assay. These mimic(s) can be easily prepared on a large scale, and such SCFMs can serve as an invaluable resource for viral fusion inhibition assays and in vitro screening of antiviral agents, which can be shared/handled between labs/facilities without worrying about any biohazard while working under routine laboratory conditions, avoiding the use of BSL3 laboratory.Abbreviations :SCFM: SARS-CoV2 Virus Fusion Mimic; ACE2: Angiotensin-Converting Enzyme 2; hACE2: Human Angiotensin-Converting enzyme 2; MEF: Mouse Embryonic Fibroblasts; HBSS: Hanks Balanced Salt Solution; FBS: Fetal Bovine Serum.

SARS-CoV-2 ORF9b antagonizes type I and III interferons by targeting multiple components of the RIG-I/MDA-5-MAVS, TLR3-TRIF, and cGAS-STING signaling pathways.

The suppression of types I and III interferon (IFN) responses by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contributes to the pathogenesis of coronavirus disease 2019 (COVID-19). The strategy used by SARS-CoV-2 to evade antiviral immunity needs further investigation. Here, we reported that SARS-CoV-2 ORF9b inhibited types I and III IFN production by targeting multiple molecules of innate antiviral signaling pathways. SARS-CoV-2 ORF9b impaired the induction of types I and III IFNs by Sendai virus and poly (I:C). SARS-CoV-2 ORF9b inhibited the activation of types I and III IFNs induced by the components of cytosolic dsRNA-sensing pathways of RIG-I/MDA5-MAVS signaling, including RIG-I, MDA-5, MAVS, TBK1, and IKKε, rather than IRF3-5D, which is the active form of IRF3. SARS-CoV-2 ORF9b also suppressed the induction of types I and III IFNs by TRIF and STING, which are the adaptor protein of the endosome RNA-sensing pathway of TLR3-TRIF signaling and the adaptor protein of the cytosolic DNA-sensing pathway of cGAS-STING signaling, respectively. A mechanistic analysis revealed that the SARS-CoV-2 ORF9b protein interacted with RIG-I, MDA-5, MAVS, TRIF, STING, and TBK1 and impeded the phosphorylation and nuclear translocation of IRF3. In addition, SARS-CoV-2 ORF9b facilitated the replication of the vesicular stomatitis virus. Therefore, the results showed that SARS-CoV-2 ORF9b negatively regulates antiviral immunity and thus facilitates viral replication. This study contributes to our understanding of the molecular mechanism through which SARS-CoV-2 impairs antiviral immunity and provides an essential clue to the pathogenesis of COVID-19.

DNA vaccine candidate encoding SARS-CoV-2 spike proteins elicited potent humoral and Th1 cell-mediated immune responses in mice.

More than 65 million people have been confirmed infection with SARS-CoV-2 and more than 1 million have died from COVID-19 and this pandemic remains critical worldwide. Effective vaccines are one of the most important strategies to limit the pandemic. Here, we report a construction strategy of DNA vaccine candidates expressing full length wild type SARS-CoV-2 spike (S) protein, S1 or S2 region and their immunogenicity in mice. All DNA vaccine constructs of pCMVkan-S, -S1 and -S2 induced high levels of specific binding IgG that showed a balance of IgG1/IgG2a response. However, only the sera from mice vaccinated with pCMKkan-S or -S1 DNA vaccines could inhibit viral RBD and ACE2 interaction. The highest neutralizing antibody (NAb) titer was found in pCMVkan-S group, followed by -S1, while -S2 showed the lowest PRNT50 titers. The geometric mean titers (GMTs) were 2,551, 1,005 and 291 for pCMVkan-S, -S1 and -S2, respectively. pCMVkan-S construct vaccine also induced the highest magnitude and breadth of T cells response. Analysis of IFN-γ positive cells after stimulation with SARS-CoV-2 spike peptide pools were 2,991, 1,376 and 1,885 SFC/106 splenocytes for pCMVkan-S, -S1 and -S2, respectively. Our findings highlighted that full-length S antigen is more potent than the truncated spike (S1 or S2) in inducing of neutralizing antibody and robust T cell responses.

1H, 13C and 15N backbone chemical shift assignments of SARS-CoV-2 nsp3a.

The non-structural protein nsp3 from SARS-CoV-2 plays an essential role in the viral replication transcription complex. Nsp3a constitutes the N-terminal domain of nsp3, comprising a ubiquitin-like folded domain and a disordered acidic chain. This region of nsp3a has been linked to interactions with the viral nucleoprotein and the structure of double membrane vesicles. Here, we report the backbone resonance assignment of both domains of nsp3a. The study is carried out in the context of the international covid19-nmr consortium, which aims to characterize SARS-CoV-2 proteins and RNAs, providing for example NMR chemical shift assignments of the different viral components. Our assignment will provide the basis for the identification of inhibitors and further functional and interaction studies of this essential protein.

A Novel Purification Procedure for Active Recombinant Human DPP4 and the Inability of DPP4 to Bind SARS-CoV-2.

Proteases catalyse irreversible posttranslational modifications that often alter a biological function of the substrate. The protease dipeptidyl peptidase 4 (DPP4) is a pharmacological target in type 2 diabetes therapy primarily because it inactivates glucagon-like protein-1. DPP4 also has roles in steatosis, insulin resistance, cancers and inflammatory and fibrotic diseases. In addition, DPP4 binds to the spike protein of the MERS virus, causing it to be the human cell surface receptor for that virus. DPP4 has been identified as a potential binding target of SARS-CoV-2 spike protein, so this question requires experimental investigation. Understanding protein structure and function requires reliable protocols for production and purification. We developed such strategies for baculovirus generated soluble recombinant human DPP4 (residues 29-766) produced in insect cells. Purification used differential ammonium sulphate precipitation, hydrophobic interaction chromatography, dye affinity chromatography in series with immobilised metal affinity chromatography, and ion-exchange chromatography. The binding affinities of DPP4 to the SARS-CoV-2 full-length spike protein and its receptor-binding domain (RBD) were measured using surface plasmon resonance and ELISA. This optimised DPP4 purification procedure yielded 1 to 1.8 mg of pure fully active soluble DPP4 protein per litre of insect cell culture with specific activity >30 U/mg, indicative of high purity. No specific binding between DPP4 and CoV-2 spike protein was detected by surface plasmon resonance or ELISA. In summary, a procedure for high purity high yield soluble human DPP4 was achieved and used to show that, unlike MERS, SARS-CoV-2 does not bind human DPP4.

The anti-HIV drug nelfinavir mesylate (Viracept) is a potent inhibitor of cell fusion caused by the SARSCoV-2 spike (S) glycoprotein warranting further evaluation as an antiviral against COVID-19 infections.

Severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) is the causative agent of the coronavirus disease-2019 (COVID-19) pandemic. Coronaviruses enter cells via fusion of the viral envelope with the plasma membrane and/or via fusion of the viral envelope with endosomal membranes after virion endocytosis. The spike (S) glycoprotein is a major determinant of virus infectivity. Herein, we show that the transient expression of the SARS CoV-2 S glycoprotein in Vero cells caused extensive cell fusion (formation of syncytia) in comparison to limited cell fusion caused by the SARS S glycoprotein. Both S glycoproteins were detected intracellularly and on transfected Vero cell surfaces. These results are in agreement with published pathology observations of extensive syncytia formation in lung tissues of patients with COVID-19. These results suggest that SARS CoV-2 is able to spread from cell-to-cell much more efficiently than SARS effectively avoiding extracellular neutralizing antibodies. A systematic screening of several drugs including cardiac glycosides and kinase inhibitors and inhibitors of human immunodeficiency virus (HIV) entry revealed that only the FDA-approved HIV protease inhibitor, nelfinavir mesylate (Viracept) drastically inhibited S-n- and S-o-mediated cell fusion with complete inhibition at a 10-µM concentration. In-silico docking experiments suggested the possibility that nelfinavir may bind inside the S trimer structure, proximal to the S2 amino terminus directly inhibiting S-n- and S-o-mediated membrane fusion. Also, it is possible that nelfinavir may act to inhibit S proteolytic processing within cells. These results warrant further investigations of the potential of nelfinavir mesylate to inhibit virus spread at early times after SARS CoV-2 symptoms appear.

A Comprehensive, Flexible Collection of SARS-CoV-2 Coding Regions.

The world is facing a global pandemic of COVID-19 caused by the SARS-CoV-2 coronavirus. Here we describe a collection of codon-optimized coding sequences for SARS-CoV-2 cloned into Gateway-compatible entry vectors, which enable rapid transfer into a variety of expression and tagging vectors. The collection is freely available. We hope that widespread availability of this SARS-CoV-2 resource will enable many subsequent molecular studies to better understand the viral life cycle and how to block it.

The ORF6, ORF8 and nucleocapsid proteins of SARS-CoV-2 inhibit type I interferon signaling pathway.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel human coronavirus causing the pandemic of severe pneumonia (Coronavirus Disease 2019, COVID-19). SARS-CoV-2 is highly pathogenic in human, having posed immeasurable public health challenges to the world. Innate immune response is critical for the host defense against viral infection and the dysregulation of the host innate immune responses probably aggravates SARS-CoV-2 infection, contributing to the high morbidity and lethality of COVID-19. It has been reported that some coronavirus proteins play an important role in modulating innate immunity of the host, but few studies have been conducted on SARS-CoV-2. In this study, we screened the viral proteins of SARS-CoV-2 and found that the viral ORF6, ORF8 and nucleocapsid proteins were potential inhibitors of type I interferon signaling pathway, a key component for antiviral response of host innate immune. All the three proteins showed strong inhibition on type I interferon (IFN-ß) and NF-κB-responsive promoter, further examination revealed that these proteins were able to inhibit the interferon-stimulated response element (ISRE) after infection with Sendai virus, while only ORF6 and ORF8 proteins were able to inhibit the ISRE after treatment with interferon beta. These findings would be helpful for the further study of the detailed signaling pathway and unveil the key molecular player that may be targeted.