Genome-wide CRISPR Knockout Screen Identified PLAC8 as an Essential Factor for SADS-CoVs Infection

Zoonotic transmission of coronaviruses poses an ongoing threat to human populations. Endemic outbreaks of Swine Acute Diarrhea Syndrome Coronavirus (SADS-CoV) have caused severe economic losses in the pig industry and have the potential to cause human outbreaks. Currently, there are no vaccines or specific antivirals against SADS-CoV, and our limited understanding of SADS-CoV host entry factors could hinder prompt responses to a potential human outbreak. Using a genome-wide CRISPR knockout screen, we identified placenta-associated 8 protein (PLAC8) as an essential host factor for SADS-CoV infection. Knockout of PLAC8 abolished SADS-CoV infection, which was restored by complementing PLAC8 from multiple species, including human, rhesus macaques, mouse, pig, pangolin, and bat, suggesting a conserved infection pathway and susceptibility of SADS-CoV among mammals. Mechanistically, PLAC8 knockout does not affect viral entry; rather, knockout cells displayed a delay and reduction in viral subgenomic RNA expression. In a swine primary intestinal epithelial culture (IEC) infection model, differentiated cultures have high levels of PLAC8 expression and support SADS-CoV replication. In contrast, expanding IEC have low levels of PLAC8 expression and are resistant to SADS-CoV infection. PLAC8 expression patterns translate in vivo; immunohistochemistry of swine ileal tissue revealed high levels of PLAC8 protein in neonatal compared to adult tissue, mirroring the known SADS-CoV pathogenesis in neonatal piglets. Overall, PLAC8 is an essential factor for SADS-CoV infection and may serve as a promising target for antiviral development for the potential pandemic SADS-CoV virus. Comparative gene expression profiling analysis of RNA-seq data for Huh7.5 cells and its PLAC8 KO derivative, with or without SADS-CoV infection.