LAUSR

The ongoing COVID‐19 pandemic severely impacts global public health and economies. To facilitate research on severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) virology and antiviral discovery, a noninfectious viral replicon system operating under biosafety level 2 containment is warranted. We report herein the construction and characterization of two SARS‐CoV‐2 minigenome replicon systems. First, we constructed the IVT‐CoV2‐Rep complementary DNA template to generate a replicon messenger RNA (mRNA) with nanoluciferase (NLuc) reporter via in vitro transcription (IVT). The replicon mRNA transfection assay demonstrated a rapid and transient replication of IVT‐CoV2‐Rep in a variety of cell lines, which could be completely abolished by known SARS‐CoV‐2 replication inhibitors. Our data also suggest that the transient phenotype of IVT‐CoV2‐Rep is not due to host innate antiviral responses. In addition, we have developed a DNA‐launched replicon BAC‐CoV2‐Rep, which supports the in‐cell transcription of a replicon mRNA as initial replication template. The BAC‐CoV2‐Rep transient transfection system exhibited a much stronger and longer replicon signal compared to the IVT‐CoV2‐Rep version. We also found that a portion of the NLuc reporter signal was derived from the spliced BAC‐CoV2‐Rep mRNA and was resistant to antiviral treatment, especially during the early phase after transfection. In summary, the established SARS‐CoV‐2 transient replicon systems are suitable for basic and antiviral research, and hold promise for stable replicon cell line development with further optimization.