A novel cell culture system modeling the SARS-CoV-2 life cycle

PLoS Pathog. 2021 Mar 12;17(3):e1009439. doi: 10.1371/journal.ppat.1009439. eCollection 2021 Mar.

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the global pandemic of COVID-19. SARS-CoV-2 is classified as a biosafety level-3 (BSL-3) agent, impeding the basic research into its biology and the development of effective antivirals. Here, we developed a biosafety level-2 (BSL-2) cell culture system for production of transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). This trVLP expresses a reporter gene (GFP) replacing viral nucleocapsid gene (N), which is required for viral genome packaging and virion assembly (SARS-CoV-2 GFP/ΔN trVLP). The complete viral life cycle can be achieved and exclusively confined in the cells ectopically expressing SARS-CoV or SARS-CoV-2 N proteins, but not MERS-CoV N. Genetic recombination of N supplied in trans into viral genome was not detected, as evidenced by sequence analysis after one-month serial passages in the N-expressing cells. Moreover, intein-mediated protein trans-splicing approach was utilized to split the viral N gene into two independent vectors, and the ligated viral N protein could function in trans to recapitulate entire viral life cycle, further securing the biosafety of this cell culture model. Based on this BSL-2 SARS-CoV-2 cell culture model, we developed a 96-well format high throughput screening for antivirals discovery. We identified salinomycin, tubeimoside I, monensin sodium, lycorine chloride and nigericin sodium as potent antivirals against SARS-CoV-2 infection. Collectively, we developed a convenient and efficient SARS-CoV-2 reverse genetics tool to dissect the virus life cycle under a BSL-2 condition. This powerful tool should accelerate our understanding of SARS-CoV-2 biology and its antiviral development.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antiviral Agents / pharmacology
  • COVID-19 / virology*
  • Cell Culture Techniques / methods*
  • Containment of Biohazards
  • Genome, Viral / drug effects
  • High-Throughput Screening Assays
  • Humans
  • SARS-CoV-2 / drug effects
  • SARS-CoV-2 / genetics
  • SARS-CoV-2 / growth & development
  • SARS-CoV-2 / physiology*
  • Virus Replication / drug effects

Substances

  • Antiviral Agents

Grants and funding

Beijing Municipal Natural Science Foundation (M21001 to QD), Tsinghua University Initiative Scientific Research Program (2019Z06QCX10 to QD), National Natural Science Foundation of China (32041005 to QD), National Key Research and Development Program of China (2020YFA0707701 to RZ), Tsinghua-Peking University Center of Life Sciences (045-61020100120 to QD), Beijing Advanced Innovation Center for Structure Biology (100300001 to QD), Start-up Foundation of Tsinghua University (53332101319 to QD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.