Vero C1008 cells (ATCC No. CRL-1586) were maintained in growth medium containing Dulbecco’s modified Eagle’s medium (DMEM, Gibco, Grand Island, NY, USA) supplemented with 10% fetal bovine protein (FBS), 250 ng/mL Amphotericin B, 100 U/mL Penicillin and 100 μg/mL Streptomycin. The recombinant viruses (iPEDVPT-P5 and iPEDVPT-P96), and the chimeric viruses (iPEDVPT-P5-96S and iPEDVPT-P96-5S), were propagated in post-inoculation medium (PI medium) containing DMEM supplemented with 0.3% tryptose phosphate broth (TBP), 0.02% yeast extract, and 10 μg/mL trypsin as described previously [18].