Tracking the Transcription Kinetic of SARS-CoV-2 in Human Cells by Reverse Transcription-Droplet Digital PCR

Viral transcription is an essential step of SARS-CoV-2 infection after invasion into the target cells. Antiviral drugs such as remdesivir, which is used to treat COVID-19 patients, targets the viral RNA synthesis. Understanding the mechanism of viral transcription may help to develop new therapeutic treatment by perturbing virus replication. In this study, we established 28 ddPCR assays and designed specific primers/probe sets to detect the RNA levels of 15 NSP, 9 ORF, and 4 structural genes of SARS-CoV-2. The transcriptional kinetics of these viral genes were determined longitudinally from the beginning of infection to 12 h postinfection in Caco-2 cells. We found that SARS-CoV-2 takes around 6 h to hijack the cells before the initiation of viral transcription process in human cells. Our results may contribute to a deeper understanding of the mechanisms of SARS-CoV-2 infection.