Evaluation of a combinatorial RNAi lentivirus vector targeting foot-and-mouth disease virus in vitro and in vivo.

Foot-and-mouth disease virus (FMDV) causes a highly contagious disease of cloven‑hoofed animals, which leads to serious economical losses. FMDV is not adequately controlled by vaccination or biosecurity measures. To generate genetically modified FMDV‑resistant animals, a combinatorial expression cassette producing three short hairpin (sh)RNAs was constructed using the lentivirus (LV) vector, LV‑3shRNA. The three shRNAs were expressed under the regulation of DNA polymerase III promoters from a buffalo and a bovine source, with one targeted to the non‑structural protein 3B, and the other two targeted to the viral polymerase protein 3D of FMDV, respectively. The role of LV‑3shRNA in the inhibition of the replication of FMDV was determined in BHK‑21 cells and in suckling mice. The results revealed that LV‑3shRNA reduced viral growth 3‑fold (24 h post‑infection) when the cells were challenged with 107‑times the tissue culture infective dose (TCID50)/ml of O serotype FMDV. The suckling mice pretreated with LV‑3shRNA were completely protected on administration of 5‑times the dose of FMDV otherwise sufficient to kill 50% of the experimental animals (LD50). These results demonstrated that the LV‑mediated dual expression of three FMDV‑specific shRNAs provided a novel strategy towards combating FMDV, which facilitates the permanent introduction of novel disease-resistance traits into the buffalo and bovine genomes in the future.