Recovery of avirulent, thermostable Newcastle disease virus strain NDV4-C from cloned cDNA and stable expression of an inserted foreign gene.

A reverse genetics system for thermostable Newcastle disease virus (NDV) is not currently available. In this study, we developed a reverse genetics system for the avirulent and thermostable NDV4-C strain. Successful recovery of NDV4-C was achieved by using either T7 RNA polymerase or cellular RNA polymerase II to drive transcription of the full-length virus antigenome from cloned cDNA. The recovered viruses rNDV4-C (T7) and rNDV4-C (CMV) showed similar growth properties, thermostability, and virulence as the parental strain NDV4-C. The potential of rNDV4-C (T7) to serve as a viral vector was assessed by generating a recombinant virus, rNDV4-eGFP, which expressed enhanced green fluorescent protein. The rNDV4-eGFP could stably carry and express eGFP for at least fifteen passages. The reverse genetics system for NDV4-C will make it possible to analyze the genetic elements that determine thermostability and the oncolytic properties of NDV.