The biosafety level-3 (BSL-3) requirement to culture severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a bottleneck for research and countermeasure development. Here we report a trans-complementation system that produces single-round infectious SARS-CoV-2 that recapitulates authentic viral replication. We demonstrate that the single-round infectious SARS-CoV-2 can be used at BSL-2 laboratories for high-throughput neutralization and antiviral testing. The trans-complementation system consists of two components: a genomic viral RNA containing a deletion of ORF3 and envelope gene, and a producer cell line expressing the two deleted genes. Trans-complementation of the two components generates virions that can infect naive cells for only one round, but does not produce wild-type SARS-CoV-2. Hamsters and K18-hACE2 transgenic mice inoculated with the complementation-derived virions exhibited no detectable disease, even after intracranial inoculation with the highest possible dose. The results suggest that the trans-complementation platform can be safely used at BSL-2 laboratories for research and countermeasure development.

中文翻译：

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SARS-CoV-2的反补系统

培养严重急性呼吸系统综合症冠状病毒2（SARS-CoV-2）的生物安全等级3（BSL-3）要求是研究和对策开发的瓶颈。在这里，我们报告了一个反式互补系统，该系统产生单轮传染性SARS-CoV-2，概括了真实的病毒复制。我们证明，单轮传染性SARS-CoV-2可以在BSL-2实验室用于高通量中和和抗病毒测试。反式互补系统由两个部分组成：包含ORF3和包膜基因缺失的基因组病毒RNA，以及表达两个缺失基因的生产细胞系。这两个成分的反式互补产生的病毒粒子只能感染幼稚细胞一轮，但不会产生野生型SARS-CoV-2。接种补体衍生病毒粒子的仓鼠和K18-hACE2转基因小鼠即使在颅内接种最高剂量后也未表现出可检测的疾病。结果表明，反互补平台可在BSL-2实验室安全地用于研究和对策开发。