PROS1 and severe acute respiratory syndrome: Flavonoids, luteolin, and quercetin have been shown to bind with S protein of SARS-CoV with high affinity and prevent SARS-CoV infection by inhibiting virus entry into Vero E6 cells, a cell line established from isolated kidney epithelial cells of an African green monkey [46], suggesting a possible anti-SARS-CoV-2 mechanism by targeting the S protein and viral entry.