Selection and Inhibitory Effect Analysis of siRNAs Specific to ORF2-4 of Porcine Reproductive and Respiratory Syndrome Virus

RNA interference (RNAi) is a powerful tool for gene function research. In order to investigate the role of GP2, GP3 and GP4 of porcine reproductive and respiratory syndrome virus (PRRSV) in the viral replication, small interference RNAs (siRNAs) directed to ORF2, ORF3 and ORF4 were designed and 12 short hairpin RNA (shRNA) expression vectors were constructed (designated as 21, 22, 23, 24, 31, 32, 33, 34, 41, 42, 43 and 44). Cells treated with shRNA expression vectors were infected by PRRSV. The effective shRNA expression vectors were selected by cytopathic effect (CPE) and fluorescence quantitative PCR (FQ-PCR). The virus titer of culture supernatant of cells treated with effective shRNA expression vectors (23, 24, 31, 34 and 41) were reduced by 184 to 4.65 folds to compare with that of controls.