In vitro Inhibition of Porcine Hemagglutinating Encephalomyelitis Virus Replication with siRNAs Targeting the Spike Glycoprotein and Replicase Polyprotein Genes

Lan, Y.; Lan, Yungang; Lu, Huijun; Zhao, Kui; He, Wenqi; Chen, Keyan; Wang, GaiLi; Song, Deguang; Gao, Feng

OBJECTIVE: The specific effect of RNA interference on the replication of porcine hemagglutinating encephalomyelitis virus (PHE-CoV) was explored. METHODS: Four species of small interfering RNA (siRNA), targeting different regions of the PHE-CoV spike glycoprotein and replicase polyprotein genes, were prepared by in vitro transcription. After transfection of PK-15 cells with each of the siRNAs followed by infection with PHE-CoV, the cytopathic effect (CPE) was examined by phase-contrast microscope, and viral proliferation within cells was examined by indirect immunofluorescence microscopy, hemagglutination (HA) test, TCID(50) assay and real-time RT-PCR. RESULTS: Examination of CPE demonstrated that the four siRNAs were capable of protecting cells against PHE-CoV invasion with very high specificity and efficiency. At 48 h post-infection, only a few siRNA-treated cells were positive for viral antigen staining, whereas most untreated virus-infected cells were positive. Transfection with siRNAs also suppressed the production of infectious virus by up to 18- to 32-fold as assessed by a HA test and 93- to 494-fold as assessed by TCID(50) assay. Furthermore, treatment with siRNAs caused a 53-91% reduction in the viral genome copy number as assessed by real-time RT-PCR. CONCLUSION: These results suggested that the four species of siRNAs can efficiently inhibit PHE-CoV genome replication and infectious virus production.