To control for potential unspecific effects of PAM treatment on cell viability, water-soluble tetrazolium salt (WST)-1 assays were performed in uninfected Vero B4, A549-ACE2/TMPRSS2+, Caco-2, or Calu-3 cells under otherwise identical conditions as the virus infection experiments. The gene discussed is ACE2; the disease is viral infectious disease.