Multiple shRNAs driven by U6 and CMV promoter enhances efficiency of antiviral effects against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is an economically significant animal disease because of the speed of its transmission. The current vaccine for FMD provides no protection until 7 days post-vaccination, thus reducing its effectiveness in the case of an outbreak. Small interfering RNA (siRNA) is a promising antiviral approach because it can induce a protective response much more rapidly. This study is the first report to apply multiple short hairpin RNA (shRNA) expression systems to inhibit foot-and-mouth disease virus (FMDV) replication. Three different shRNAs, one targeting 2B region and two targeting 3C region, were driven by three RNA Polymerase III (Pol III) promoters, U6 or a combination of two U6 promoters and one RNA Polymerase II (Pol II) promoter, CMV. The adenoviruses simultaneously expressing three different shRNAs in a single construct had significantly enhanced antiviral effects compared with those expressing only a single shRNA, those expressing double shRNAs or a mixture of adenoviruses expressing a single shRNA and the adenovirus expressing double shRNAs, both in vitro and in vivo. The adenoviruses had broad antiviral effects against seven serotypes of FMDV, including O, A, Asia1, C, SAT1, SAT2, and SAT3 in vitro, but differed in their efficacy. The adenovirus expressing multiple shRNAs driven by three U6 promoters had strong antiviral effects in suckling mice challenged with O, A, and Asia1 serotype of FMDV.