In vitro inhibition of porcine hemagglutinating encephalomyelitis virus replication with siRNAs targeting the spike glycoprotein and replicase polyprotein genes

Abstract

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. Copyright © 2011 S. Karger AG, Basel.