Early Immunological Response of Young Chickens to Modified Newcastle Virus

NEWCASTLE disease virus, California strain #11914, adapted to the Syrian hamster by Reagan, Lillie, Poelma and Brueckner (1947) (1948a) proved valuable as an immunizing agent in young chickens. Further studies by Reagan et al. (1948b) of the modified Newcastle virus prompted the following experiments to determine early immunological responses of chickens to the living hamster-adapted virus and to the living hamster-chick embryo virus. EXPERIMENTAL PROCEDURE Healthy six-week-old New Hampshire chickens from a Newcastle disease-free source, which were identified with wing bands, were used for this experiment. Serum from these birds showed no Newcastle virus neutralizing antibodies when tested by the hemagglutination-inhibition method prior to vaccination. To avoid exposure to the vaccine virus and the challenge virus, approximately 250 of the young non-vaccinated chickens which were to be used for challenge virus titrations, were not brought to the laboratory grounds until the day before respective challenges. One large group of the . . .