title: Titration of avirulent Newcastle disease virus by the plaque assay method.
abstract: Parameters of a plaque assay for avirulent strains of Newcastle disease virus (NDV) were optimized for reproducibility and optimum titer in LLC-MK2 cells. Plaques were visible after 2 days and maximum virus titers were reached in 3 days. Virus titers were not affected by continued incubation through 6 days, although plaque size increased. An adsorption volume of 0.1 or 0.2 ml per 60 mm Petri dish was optimal, as was an adsorption time of 45 min. Trypsin (2.5 micrograms/ml) and magnesium sulfate (0.03 M) were essential requirements of the overlay medium and the presence of DEAE-dextran (0.02%) resulted in a 30% increase in titer. The use of cell monolayers, 1, 2, or 3 days old facilitated the performance of multiple assays per week and did not affect the virus titer.
authors.affiliation: Defence Research Establishment Suffield, Biomedical Defence Section, Ralston, Alberta, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Kournikakis
authors.forename: J
authors.initials: J
authors.lastname: Fildes
mesh_terms: D000818:Animals; D002460:Cell Line; D009522:Newcastle disease virus / Q000254:growth & development* / Q000472:pathogenicity; D010948:Viral Plaque Assay; D014774:Virulence