Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2004
Publication Date: 2/25/2005
Citation: Seal, B.S., Wise, M., Pedersen, J.C., Senne, D.A., Alvarez, R., Scott, M.A., King, D.J., Yu, Q., Kapczynski, D.R. 2005. Genomic sequences of low virulence avian paramyxovirus 1 (Newcastle disease virus) isolates obtained from live-bird markets in North America not related to commonly utilized commercial vaccine strains. Veterinary Microbiology. 106(1-2):7-16. Interpretive Summary: Newcastle disease virus (NDV), also referred to as avian paramyxovirus 1 (APMV1) can cause devastating disease among commercial poultry when virulent forms of the virus infect chickens. The highly virulent form of the disease must be reported to regulatory agencies at the national and international level when detected among any type of birds. It is important to be able to distinguish between low-virulence viruses and the more virulent forms of NDV. This is especially true since low-virulence NDV isolates have been detected among birds in live-bird markets of the northeastern United States. This situation has been particularly frustrating because the live-bird market isolates have not been amenable to molecular typing methods utilized by national diagnostic labs. Consequently, these viruses were characterized by sequencing of the viral genome. It was discovered that the low-virulence, live-bird market NDV isolates were most similar to viruses not previously reported in the United States and very different from NDV vaccine strains used by the poultry industry. The genome sequence of these viruses can now be utilized to devise more precise diagnostic tools for diagnostic labs involved with Newcastle disease surveillance.
Technical Abstract: Avian paramyxovirus 1 (APMV1), also referred to as Newcastle disease virus (NDV), variants of low virulence were isolated from chickens, ducks and other unidentified species found in live-bird markets of the northeastern United States. These isolates were characterized as APMV1 by the hemagglutination inhibition (HI) assay utilizing NDV-specific polyclonal antisera. However, the isolates failed to react with a monoclonal antibody that has specificity for a wide variety of APMV1 isolates. Although only highly virulent isolates require reporting to international regulatory agencies, the ability to correctly identify APMV1 types is important for control and regulatory purposes. Protein gel patterns of the purified isolates resembled previously reported APMV1 and anti-NDV polyclonal sera recognized the viral proteins. For three representative strains oligonucleotide primers specific for the nucleoprotein, fusion protein and polymerase genes of NDV were utilized to synthesize cDNA using viral RNA as a template. Approximately 12kb of the genome was subsequently sequenced for the three isolates that included the nucleoprotein, phosphoprotein, matrix protein, fusion (F) protein, hemagglutinin-neuraminidase protein genes and a portion of the polymerase gene. The isolates had a F protein cleavage site sequence of ERQER/LVG indicating low virulence viruses that phylogentically separated with other unique NDV isolates designated as a lineage 6 genotype. Additionally, a four amino acid insert was detected in the predicted phosphoprotein which complies with the 'rule of six' among paramyxoviruses. These APMV1 genotypes have not been previously reported in North America and further substantiate the heterogeneous genetic nature of these commercially important pathogens found worldwide.