Suckling mice (8 groups of 20 each) were subcutaneously injected in the neck with 100 lg of plasmids in 100 lL of phosphate-buffered saline (PBS). After 6 h, the suckling mice were challenged with 20 LD 50 of FMDV per 0.1 mL via subcutaneous injection into the neck near the site that received the injected DNA. The mice were then observed for 5 days post-challenge (dpc). Statistical analysis was performed with a log rank test 2 .