Abstract

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.

Highlights

  • 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

  • We used a bacterial artificial chromosome (BAC)-based approach, similar to the one that we previously described for Zika virus [16,17,18,19,20,21], to assemble an infectious clone of SARS-CoV-2 based on the USA-WA1/2020 strain (Fig. 1A)

  • We selected this SARS-CoV-2 strain because it was isolated from an oropharyngeal swab from a patient with respiratory illness in Snohomish County, Washington state, USA

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Summary

Introduction

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. 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). 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. Reverse genetics facilitates the generation of recombinant viruses expressing reporter genes for their use in cell-based screening assays or in vivo models of infection for the rapid and easy identification of prophylactic and therapeutic approaches for the treatment of viral infections, as well as to generate attenuated forms of viruses for their implementation as safe, immunogenic, and protective live attenuated vaccines (LAVs)

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