biostudies-literatureUnknown10Liu J<h4>Background</h4>The virulent Newcastle disease virus (NDV) strain NA-1 (genotype VII) was isolated from an epizootic involving a flock of geese in Jilin Province, Northeast China, in 1999. Compared with the classical NDV strains, which have a genome size of 15,186 bp, the more recently isolated NDV strains, including that involved in the goose outbreak, have an extra six nucleotides in the 5'-untranslated region (UTR) of the nucleoprotein (NP) gene. This extra sequence, TCCCAC, is highly conserved and has been found in multiple NDV strains, including ZJ-1, WF00G, JSG0210, and NA-1. In the current study, an infectious clone from strain NA-1 was isolated and designated rNA-1. Subsequently, strain rNA-1 was mutated to delete the six-nucleotide insertion, producing strain rNA-1(-). VirulencBMC veterinary research964https://www.ebi.ac.uk/biostudies/studies/S-EPMC4297397biostudies-literatureThe deletion of an extra six nucleotides in the 5' -untranslated region of the nucleoprotein gene of Newcastle disease virus NA-1 decreases virulence.PMC4297397Liu XLiu JDing CYu SWang CYin RCong YDing ZfalseThe deletion of an extra six nucleotides in the 5' -untranslated region of the nucleoprotein gene of Newcastle disease virus NA-1 decreases virulence.<h4>Background</h4>The virulent Newcastle disease virus (NDV) strain NA-1 (genotype VII) was isolated from an epizootic involving a flock of geese in Jilin Province, Northeast China, in 1999. Compared with the classical NDV strains, which have a genome size of 15,186 bp, the more recently isolated NDV strains, including that involved in the goose outbreak, have an extra six nucleotides in the 5'-untranslated region (UTR) of the nucleoprotein (NP) gene. This extra sequence, TCCCAC, is highly conserved and has been found in multiple NDV strains, including ZJ-1, WF00G, JSG0210, and NA-1. In the current study, an infectious clone from strain NA-1 was isolated and designated rNA-1. Subsequently, strain rNA-1 was mutated to delete the six-nucleotide insertion, producing strain rNA-1(-). Virulenc2014-01-01T00:00:00Z2014 Dec2025-04-22T15:18:26.637Z2019-03-27T01:43:33ZS-EPMC42973972552858110.1186/s12917-014-0305-5