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A bacterial artificial chromosome (BAC)-vectored noninfectious replicon of SARS-CoV-2.

ABSTRACT: Vaccines and antiviral agents are in urgent need to stop the COVID-19 pandemic. To facilitate antiviral screening against SARS-CoV-2 without requirement for high biosafety level facility, we developed a bacterial artificial chromosome (BAC)-vectored replicon of SARS-CoV-2, nCoV-SH01 strain, in which secreted Gaussia luciferase (sGluc) was encoded in viral subgenomic mRNA as a reporter gene. The replicon was devoid of structural genes spike (S), membrane (M), and envelope (E). Upon transfection, the replicon RNA replicated in various cell lines, and was sensitive to interferon alpha (IFN-?), remdesivir, but was resistant to hepatitis C virus inhibitors daclatasvir and sofosbuvir. Replication of the replicon was also sensitive overexpression to zinc-finger antiviral protein (ZAP). We also constructed a four-plasmid in-vitro ligation system that is compatible with the BAC system, which makes it easy to introduce desired mutations into the assembly plasmids for in-vitro ligation. This replicon system would be helpful for performing antiviral screening and dissecting virus-host interactions.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC7670965 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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A bacterial artificial chromosome (BAC)-vectored noninfectious replicon of SARS-CoV-2.

Zhang Yang Y Song Wuhui W Chen Shuiye S Yuan Zhenghong Z Yi Zhigang Z

Antiviral research 20201117

Vaccines and antiviral agents are in urgent need to stop the COVID-19 pandemic. To facilitate antiviral screening against SARS-CoV-2 without requirement for high biosafety level facility, we developed a bacterial artificial chromosome (BAC)-vectored replicon of SARS-CoV-2, nCoV-SH01 strain, in which secreted Gaussia luciferase (sGluc) was encoded in viral subgenomic mRNA as a reporter gene. The replicon was devoid of structural genes spike (S), membrane (M), and envelope (E). Upon transfection, ...[more]

PMID: 33217430

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Project description:Infectious coronavirus (CoV) disease 2019 (COVID-19) emerged in the city of Wuhan (China) in December 2019, causing a pandemic that has dramatically impacted public health and socioeconomic activities worldwide. A previously unknown coronavirus, severe acute respiratory syndrome CoV-2 (SARS-CoV-2), has been identified as the causative agent of COVID-19. To date, there are no U.S. Food and Drug Administration (FDA)-approved vaccines or therapeutics available for the prevention or treatment of SARS-CoV-2 infection and/or associated COVID-19 disease, which has triggered a large influx of scientific efforts to develop countermeasures to control SARS-CoV-2 spread. To contribute to these efforts, we have developed an infectious cDNA clone of the SARS-CoV-2 USA-WA1/2020 strain based on the use of a bacterial artificial chromosome (BAC). Recombinant SARS-CoV-2 (rSARS-CoV-2) was readily rescued by transfection of the BAC into Vero E6 cells. Importantly, BAC-derived rSARS-CoV-2 exhibited growth properties and plaque sizes in cultured cells comparable to those of the natural SARS-CoV-2 isolate. Likewise, rSARS-CoV-2 showed levels of replication similar to those of the natural isolate in nasal turbinates and lungs of infected golden Syrian hamsters. This is, to our knowledge, the first BAC-based reverse genetics system for the generation of infectious rSARS-CoV-2 that displays features in vivo similar to those of a natural viral isolate. This SARS-CoV-2 BAC-based reverse genetics will facilitate studies addressing several important questions in the biology of SARS-CoV-2, as well as the identification of antivirals and development of vaccines for the treatment of SARS-CoV-2 infection and associated COVID-19 disease.IMPORTANCE The pandemic coronavirus (CoV) disease 2019 (COVID-19) caused by severe acute respiratory syndrome CoV-2 (SARS-CoV-2) is a major threat to global human health. To date, there are no approved prophylactics or therapeutics available for COVID-19. Reverse genetics is a powerful approach to understand factors involved in viral pathogenesis, antiviral screening, and vaccine development. In this study, we describe the feasibility of generating recombinant SARS-CoV-2 (rSARS-CoV-2) by transfection of a single bacterial artificial chromosome (BAC). Importantly, rSARS-CoV-2 possesses the same phenotype as the natural isolate in vitro and in vivo This is the first description of a BAC-based reverse genetics system for SARS-CoV-2 and the first time that an rSARS-CoV-2 isolate has been shown to be phenotypically identical to a natural isolate in a validated animal model of SARS-CoV-2 infection. The BAC-based reverse genetics approach will facilitate the study of SARS-CoV-2 and the development of prophylactics and therapeutics for the treatment of COVID-19.

Project description:The emerging coronavirus disease 2019 (COVID-19) outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread worldwide, resulting in global public health emergencies and economic crises. In the present study, a noninfectious and biosafety level 2 (BSL2)-compatible SARS-CoV-2 replicon expressing a nano luciferase (nLuc) reporter was constructed in a bacterial artificial chromosomal (BAC) vector by reverse genetics. The nLuc reporter is highly sensitive, easily quantifiable, and high throughput adaptable. Upon transfecting the SARS-CoV-2 replicon BAC plasmid DNA into Vero E6 cells, we could detect high levels of nLuc reporter activity and viral RNA transcript, suggesting the replication of the replicon. The replicon replication was further demonstrated by the findings that deleting nonstructural protein 15 or mutating its catalytic sites significantly reduced replicon replication, whereas providing the nucleocapsid protein in trans enhanced replicon replication in a dose-dependent manner. Finally, we showed that remdesivir, a U.S. Food and Drug Administration-approved antiviral drug, significantly inhibited the replication of the replicon, providing proof of principle for the application of our replicon as a useful tool for developing antivirals. Taken together, this study established a sensitive and BSL2-compatible reporter system in a single BAC plasmid for investigating the functions of SARS-CoV-2 proteins in viral replication and evaluating antiviral compounds. This should contribute to the global effort to combat this deadly viral pathogen. IMPORTANCE The COVID-19 pandemic caused by SARS-CoV-2 is having a catastrophic impact on human lives. Combatting the pandemic requires effective vaccines and antiviral drugs. In the present study, we developed a SARS-CoV-2 replicon system with a sensitive and easily quantifiable reporter. Unlike studies involving infectious SARS-CoV-2 virus that must be performed in a biosafety level 3 (BSL3) facility, the replicon is noninfectious and thus can be safely used in BSL2 laboratories. The replicon will provide a valuable tool for testing antiviral drugs and studying SARS-CoV-2 biology.

Project description:Dopamine ?-hydroxylase (DBH) converts dopamine (DA) to norepinephrine (NE) in noradrenergic/adrenergic cells. DBH deficiency prevents NE production and causes sympathetic failure, hypotension and ptosis in humans and mice; DBH knockout (Dbh -/-) mice reveal other NE deficiency phenotypes including embryonic lethality, delayed growth, and behavioral defects. Furthermore, a single nucleotide polymorphism (SNP) in the human DBH gene promoter (-970C>T; rs1611115) is associated with variation in serum DBH activity and with several neurological- and neuropsychiatric-related disorders, although its impact on DBH expression is controversial. Phenotypes associated with DBH deficiency are typically treated with L-3,4-dihydroxyphenylserine (DOPS), which can be converted to NE by aromatic acid decarboxylase (AADC) in the absence of DBH. In this study, we generated transgenic mice carrying a human bacterial artificial chromosome (BAC) encompassing the DBH coding locus as well as ~45 kb of upstream and ~107 kb of downstream sequence to address two issues. First, we characterized the neuroanatomical, neurochemical, physiological, and behavioral transgenic rescue of DBH deficiency by crossing the BAC onto a Dbh -/- background. Second, we compared human DBH mRNA abundance between transgenic lines carrying either a "C" or a "T" at position -970. The BAC transgene drove human DBH mRNA expression in a pattern indistinguishable from the endogenous gene, restored normal catecholamine levels to the peripheral organs and brain of Dbh -/- mice, and fully rescued embryonic lethality, delayed growth, ptosis, reduced exploratory activity, and seizure susceptibility. In some cases, transgenic rescue was superior to DOPS. However, allelic variation at the rs1611115 SNP had no impact on mRNA levels in any tissue. These results indicate that the human BAC contains all of the genetic information required for tissue-specific, functional expression of DBH and can rescue all measured Dbh deficiency phenotypes, but did not reveal an impact of the rs11115 variant on DBH expression in mice.

Project description:Reporter-expressing recombinant virus represents an excellent option and a powerful tool to investigate, among others, viral infection, pathogenicity, and transmission, as well as to identify therapeutic compounds that inhibit viral infection and prophylactic vaccines. To combat the ongoing coronavirus disease 2019 (COVID-19) pandemic, we have established a robust bacterial artificial chromosome (BAC)-based reverse genetics (RG) system to rapidly generate recombinant severe acute respiratory syndrome coronavirus 2 (rSARS-CoV-2) to study the contribution of viral proteins in viral pathogenesis. In addition, we have engineered reporter-expressing recombinant viruses in which we placed the reporter genes upstream of the viral nucleocapsid (N) gene to promote high levels of reporter gene expression, which facilitates the study of SARS-CoV-2 in vitro and in vivo. To date, we have shared our BAC-based RG system with more than 100 laboratories around the world, which has helped to expedite investigations with SARS-CoV-2. However, genetic manipulation of the BAC containing the entire SARS-CoV-2 genome (~30,000 nt) is challenging. Herein, we provide the technical details to engineer rSARS-CoV-2 using the BAC-based RG approach. We describe (i) assembly of the full-length (FL) SARS-CoV-2 genome sequences into the empty pBeloBAC, (ii) verification of pBeloBAC-FL, (iii) cloning of a Venus reporter gene into pBeloBAC-FL, and (iv) recovery of the Venus-expressing rSARS-CoV-2. By following this protocol, researchers with knowledge of basic molecular biology and gene engineering techniques will be able to generate wild-type (WT) and reporter-expressing rSARS-CoV-2. IMPORTANCE We have established a bacterial artificial chromosome (BAC)-based RG system to generate recombinant severe acute respiratory syndrome coronavirus 2 (rSARS-CoV-2) and to engineer reporter-expressing recombinant viruses to assess viral infection in vitro and in vivo. To date, we have shared our BAC-based RG system with more than 100 laboratories around the world, which has helped to expedite investigations with SARS-CoV-2. However, genetic manipulation of the BAC containing the full-length SARS-CoV-2 genome of ~30,000 nucleotides is challenging. Here, we provide all the detailed experimental steps required for the successful generation of wild-type (WT) recombinant SARS-CoV-2 (rSARS-CoV-2). Likewise, we provide a comprehensive protocol on how to generate and rescue rSARS-CoV-2 expressing high levels of a Venus fluorescent reporter gene from the locus of the viral nucleocapsid (N) protein. By following these protocols, researchers with basic knowledge in molecular biology will be able to generate WT and Venus-expressing rSARS-CoV-2 within 40 days.

Dataset Information

A bacterial artificial chromosome (BAC)-vectored noninfectious replicon of SARS-CoV-2.

Publications

A bacterial artificial chromosome (BAC)-vectored noninfectious replicon of SARS-CoV-2.

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