Engineering a Reliable and Convenient SARS-CoV-2 Replicon System for Analysis of Viral RNA Synthesis and Screening of Antiviral Inhibitors.

The etiologic agent of COVID-19 is highly contagious and has caused a severe global pandemic. Until now, there has been no simple and reliable system available in a lower-biosafety-grade laboratory for SARS-CoV-2 virologic research and inhibitor screening. In this study, we reported a replicon system which consists of four plasmids expressing the required segments of SARS-CoV-2. Our study revealed that the features for viral RNA synthesis and responses to antivirus drugs of the replicon are similar to those of wild-type viruses. Further analysis indicated that ORF6 provided potent in trans stimulation of the viral replication. Some viral variations, such as 5'UTR-C241T and ORF8-(T28144C) L84S mutation, also exhibit their different impact upon viral replication. Besides, the screening of clinically used drugs identified that several tyrosine kinase inhibitors and DNA-Top II inhibitors potently inhibit the replicon, as well as authentic SARS-CoV-2 viruses. Collectively, this replicon system provides a biosafety-worry-free platform for studying SARS-CoV-2 virology, monitoring the functional impact of viral mutations, and developing viral inhibitors.IMPORTANCE COVID-19 has caused a severe global pandemic. Until now, there has been no simple and reliable system available in a lower-biosafety-grade laboratory for SARS-CoV-2 virologic research and inhibitor screening. We reported a replicon system which consists of four ordinary plasmids expressing the required segments of SARS-CoV-2. Using the replicon system, we developed three application scenarios: (i) to identify the effects of viral proteins on virus replication, (ii) to identify the effects of mutations on viral replication during viral epidemics, and (iii) to perform high-throughput screening of antiviral drugs. Collectively, this replicon system would be useful for virologists to study SARS-CoV-2 virology, for epidemiologists to monitor virus mutations, and for industry to develop antiviral drugs.