Based on the experiments in guinea pigs, we evaluated the antiviral activity of p3D-NT56/S. cho in swine. Animals were intramuscularly inoculated with 5 · 10 9 CFU of p3D-NT56/S. cho and challenged 24 h later with 100 ID 50 of HKN/2002. All of the saline-treated swine developed acute signs of FMD, including vesicles and fever (Fig. 3A) . Animal 1-48 had vesicles as early as 3 dpc, and its symptoms were extraordinarily severe. In comparison with this group, animals inoculated with either pLacZ/ S. cho or S. cho showed no signs of significant antiviral activity (Figs. 3B and 3C) . However, p3D-NT56/S. cho conferred marked antiviral activity that could be seen for more than 9 days of observation (Fig. 3D) . Animal 2-7 in this group developed a fever but no vesicles during the observation period. Although animals 5-6, 3-3 and 1-1 developed vesicles, they were fewer and developed much later. In another group inoculated with 5 · 10 10 CFU of p3D-NT56/S. cho, none of the animals were protected (Fig. 3E ), but animal 7-1 showed delayed disease onset and milder disease than the control animals. Serum samples were collected at 0, 7, and 14 dpc and tested for the presence of neutralizing antibodies and antibodies against viral NS protein 3ABC of FMDV. No animals had marked FMDV-specific antibodies at 0 dpc, including anti-3ABC antibodies (Tab. II). Animals in the control groups treated with saline, S. cho or pLacZ/S. cho developed a high neutralizing antibody response at 7 and 14 dpc, suggesting that these animals were exposed to a very large amount of FMDV (Tab. II). A very low neutralizing antibody response was detected at 7 dpc in animals (2-7, 5-6, 3-3, 1-1, 7-1 and 1-34) that were inoculated with p3D-NT56/S. cho, suggesting that these animals effectively suppressed virus replication. A key distinguishing feature of infected animals is the induction of antibodies against the polyprotein 3ABC of FMDV [45] . Using an LPB-ELISA, we showed that the animals developing FMD had significantly higher levels of antibodies against 3ABC as compared to the disease-free animals (Tab. II). These results of serological analysis were consistent with the observation of clinical signs.