Mucosal immunity in chickens vaccinated with the V4 strain of Newcastle disease virus.

Chickens vaccinated orally with the V4 strain of Newcastle disease virus (NDV) and possessing low levels or undetectable levels of serum haemagglutination-inhibition (HI) antibodies against NDV may resist challenge with virulent virus. Evidence for vaccine-induced mucosal immunity was sought. HI antibodies were detected in serum, lachrymal fluid and tracheal washing after vaccination with V4 virus by intranasal, eyedrop or intracrop routes. IgA was detected by immunodiffusion in lachrymal fluid of both vaccinated and control birds. Lymphoid accumulations were detected in tracheas of chickens after vaccination and there were significant increases in the numbers of plasma cells in sections of Harderian glands from chickens after vaccination. In a second experiment, ELISA was used to demonstrate the production of NDV-specific IgA which was detected in serum, lachrymal fluid, tracheal washing and intestinal washing after intracrop or eyedrop vaccination with V4 virus. It was concluded that oral vaccination of chickens with V4 virus induces a mucosal immune response.