Submitted to: Microbial Pathogenesis
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/7/2005
Publication Date: 8/9/2005
Citation: Oldoni, I., Brown, C., King, D.J., Samal, S., Seal, B.S. 2005. The use of in situ hybridization and immunohistochemistry to study the pathogenesis of varous newcastle disease virus strains and recombinants in embryonated chicken eggs. Microbial Pathogenesis. 39:69-75. Interpretive Summary: Newcastle disease virus (NDV) formally designated avian paramyxovirus-1 (APMV1) causes a serious, economically important disease that must be reported internationally to regulatory agencies when outbreaks of virulent disease occur among poultry. Embryonated chicken eggs were utilized to examine the contribution of different NDV proteins to virulence of the virus by pathology-based techniques. The protein on the surface of the virus important for attachment to cells during infection from very virulent viruses was genetically placed into viruses of low virulence. The low virulent viruses with the highly virulent NDV attachment protein behaved more similar to the highly virulent virus types in that they could be detected extensively in chicken embryos. Also, the phosphoprotein (P) important for the virus to replicate was genetically altered and this made NDV less virulent than parent strains in chicken embryos. Consequently, the viral attachment protein and the P protein are important to NDV virulence. Also, the embryonated chicken egg can be utilized for determining which NDV proteins are important to virulence of the virus and this will be useful during future development of vaccines for this virus.
Technical Abstract: Avian paramyxovirus type 1, commonly referred to as Newcastle disease virus (NDV), is a serious pathogen of significant economic importance to the poultry industry. To investigate the role of the fusion (F), hemagglutinin-neuraminidase (HN), and P protein gene sequences in virulence, six strains of Newcastle disease virus (NDV) representing all pathotypes and seven recombinant strains created by reverse genetics were inoculated into 9-day-old chicken embryos. Tissues and chorioallantoic membranes were harvested at 24- hour intervals post inoculation. Riboprobe in situ hybridization and immunohistochemistry highlighted distinct tissue tropisms among the viruses. Presence of F and/or HN from virulent viruses inserted into lentogenic backbones caused dissemination of virus in a manner similar to wild type virulent viruses. Disruption of P gene decreased dissemination of velogeinic infectious clones. It is concluded that each of these genes contributes to virulence.