Construction of a minigenome rescue system for Newcastle disease virus strain Italien.

Newcastle disease virus (NDV) Italien, a velogenic strain, is an oncolytic virus that is considered to be a potential agent for antitumor viral therapy. We constructed three helper plasmids expressing the NP, P and L genes of NDV Italien based on the eukaryotic expression plasmid pcDNA3.1(+). The minigenome consisting of the 3' leader and 5' trailer regions of NDV Italien flanking a reporter gene encoding firefly luciferase was constructed to examine the efficacy of the three helper plasmids in viral genome replication and transcription. After co-transfection of BSR-T7/5 cells with the three helper plasmids and the minigenome plasmid, replication of minigenome RNA was evaluated by determining luciferase activity. In the minigenome rescue system, expression of the reporter gene was detected. Our results indicate that the three proteins NP, P, and L are correctly expressed and can assemble into a functional ribonucleoprotein complex that effectively directs the transcription of minigenome RNA.