Cyclosporin A, but not FK506 suppresses FIPV replication in fcwf-4 cells. (A) Cells were infected with FIPV and incubated with or without the indicated concentrations of CsA or FK506. Total RNA extracted from cells 22 h later were reverse-transcribed to cDNA and assayed by real-time PCR assays targeting FIPV-N and β2M genes. Relative amounts of FIPV RNA expression data were normalized with β2M gene expression. Error bars indicate means ± 2SD. (B) Western blots of cells incubated with various concentrations of CsA and FK506. Lanes show total cellular proteins resolved by electrophoresis. Effects of CsA and FK506 were assessed using monoclonal anti-FIPV-N and anti-β-actin primary antibodies.