Rescue of SARS-CoV-2 from a single bacterial artificial chromosome

An infectious coronavirus 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 around the world. A previously unknown coronavirus, Severe Acute Respiratory Syndrome CoV-2 (SARS-CoV-2), has been identified as the causative agent of COVID-19, raising challenges for understanding this new human pathogen. To date, there are no United States (US) Food and Drug Administration (FDA)-approved vaccines or therapeutics available for the prevention or treatment, respectively, of SARS-CoV-2 infection, which has triggered a large 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 a SARS-CoV-2, USA-WA1/2020 strain, based on the use of a bacterial artificial chromosome (BAC). Recombinant (r)SARS-CoV-2 was easily rescued by transfection of the BAC into Vero E6 cells. Importantly, the BAC-derived rSARS-CoV-2 replicated and formed plaque sizes comparable to those of the SARS-CoV-2 natural isolate. Notably, rSARS-CoV-2 showed similar levels of replication to those of the SARS-CoV-2 natural isolate in the nasal turbinates and lungs of golden Syrian hamsters. This is, to our knowledge, the first reverse genetics system to generate rSARS-CoV-2 based on a BAC that has similar features in vivo to those of a natural viral isolate. This SARS-CoV-2 BAC-based reverse genetics will facilitate studies addressing a number of important questions in the biology of SARS-CoV-2 and in the identification of antivirals and/or development of vaccines for the treatment of SARS-CoV-2 infection and associated COVID-19 disease