Abstract
A soluble Newcastle disease virus (NDV) agar gel precipitin (AGP) antigen was prepared by treating 100-fold concentrated NDV with a nonionic detergent. Virus concentration prior to detergent treatment was best accomplished by ultracentrifugation or by a simple, less expensive, and more practical method involving acid (HCl) precipitation of NDV. Virus concentrated by polyethylene glycol precipitation was found to have a low antigen titer and was not considered suitable as an AGP antigen. Antigens derived from the LaSota, Roakin, and Texas GB strains formed at least two lines of identity in the AGP test as early as 24 hr after inoculation of the agar gels. Virus used for AGP antigen production could be grown in chicken embryos from an NDV-immune as well as susceptible breeder flock. The NDV AGP antigen was found to be stable after 20 consecutive freezing and thawing cycles and storage at -20 C or 4 C for at least 6 months. Detergent-treated NDV was used as an AGP test antigen to determine serum antibody responses of chickens following infection and vaccination. Hemagglutination-inhibition, virus neutralization, and enzyme-linked immunosorbent assay antibody production was also evaluated for comparative purposes. The AGP test was found to be useful as an aid in diagnosing field infections and assessing inactivated virus vaccination responses. These purposes were achieved by demonstrating an increase in the number of AGP positive chickens between preinfection and postinfection or vaccination bleedings. The ease of performance and low cost of the AGP test favors its use for screening large numbers of serum samples, perhaps in conjunction with a quantitative serological test.(ABSTRACT TRUNCATED AT 250 WORDS)