Attenuation Of Goose Paramyxovirus Strain NA-1 By Reverse Genetics

Newcastle disease (ND) is widely accepted as one of the most serious infectious diseases in poultry industry worldwide. The causative pathogen of the disease, Newcastle disease virus (NDV), which also has been designated as avian paramyxovirus serotype 1 (APMV-1), is a member of the genus Avulavirus within family Paramyxoviridae. The negative-sense, single-stranded RNA genome of NDV contains six genes in the order of 3′-Leader-NP-P-M-F-HN-L-Trailer-5′encoding six major structural proteins: nucleocapsid protein (NP), phosphoprotein (P), matrix protein (M), fusion protein (F), hemagglutinin-neuraminidase (HN), and large polymerase protein (L). Two additional gene products, designated as V and W protein, may be generated by an RNA-editing event of the P gene mRNA.Based on the results of standard pathotyping assays, NDV strains are classified into three phenotypes: velogenic (highly virulent), mesogenic (intermediate), and lentogenic (non-virulent). For decades, even the most virulent NDV strain had not been considered as a cause of serious disease in domestic and wild waterbird species. However, at least four NDV strains have been found to be responsible for a fatal disease of goose flocks in many provinces of South, East and Northeast China since 1997.To improve a novel NDV live-attenuated vaccine candidate for geese, we set out to develop a system that would allow genetic modification of virulent NDV strain NA-1. To improve a novel NDV live-attenuated vaccine candidate for geese, we set out to develop a system that would be allowed of the genetic modification of virulent NDV strain NA-1. The present article describes the establishment of an infectious full-length cDNA clone of NDV strain NA-1. Additionally, the generated NDV was observed a similar pathogenicity and growth characteristics to that of the wild-type virus. This recovery system, which is based on the intracellular synthesis of T7 RNA polymerase transcripts corresponding to the complete genome of NDV, not only serves as a technical tool for analysis of gene function in the goose NDV, but also provides the possibility for the development of a new vaccine vector.The present article describes the recovery of attenuated virus with reverse genetics techniques. Based on the establishment of a full-length cDNA clone of NDV strain NA-1, we successfully rescued infectious virus by co-transfection the full-length cDNA clone with three helper plasmids. Additionally, the generated NDV was observed the similar pathogenicity and growth characteristics to that of the wild-type virus. Then we introduced three nucleotide changes in the cDNA clone to generate a genetically tagged derivative of the NA-1 strain (GRRQKR↓F) in which the amino acid sequence of the protease cleavage site of the fusion protein F0 was changed to the consensus cleavage site of the vaccine strain LaSota (GGRQER↓L). The result of the pathogenicity of attenuated virus and cross immune protection for animal showed that it is a potential vaccine candidate for the control of current ND epidemic in China.