To further examine the anti-FMDV potential of p3D-NT56 or p2B-NT25 in vivo, we challenged suckling mice pretreated by subcutaneous injection of plasmids with FMDV strains HKN/2002 or YNBS/58. All PBS-treated mice died within 60 h after either HNK/2002 or YNBS/58 challenge (Fig. 2) . The animals treated with control plasmids were also not protected at all, although death in some groups was delayed slightly (p = 0.47, p = 0.157) (Fig. 2) . In HKN/2002 challenge experiments, 20% of the animals treated with either p3D-NT56 or p2B-NT25 were protected ( Fig. 2A) . The difference between the survival of mice treated with either p3D-NT56 or p2B-NT25 and the PBS control was statistically significant (p < 0.0001). In the case of challenge with YNBS/58, 8 of 20 mice treated with p3D-NT56 and 7 of 20 mice treated with p2B-NT25 survived a viral challenge of 20 LD 50 (Fig. 2B) , and a significant difference in mouse survival was seen between mice treated with either p3D-NT56 or p2B-NT25 and controls (p < 0.0001). Furthermore, in both HNK/2002 and YNBS/58 challenge assays, the time of 50% death of mice was delayed for 9 to 24 h in groups treated with FMDV-specific siRNAexpressing plasmids as compared with control groups. 