Cell-mediated immunity in chickens vaccinated with the V4 strain of Newcastle disease virus.

A leukocyte migration inhibition assay was used to demonstrate antigen-specific cell-mediated immunity (CMI) in chickens vaccinated with the V4 strain of Newcastle disease virus. Chickens were vaccinated when 5 weeks old, and again 3 and 7 weeks later. CMI was detected 9 days after initial vaccination by eyedrop, but only after the second dose of vaccine delivered into the crop. In some chickens there was a temporary suppression of CMI to Newcastle disease virus, especially after the initial application of vaccine to the crop. Haemagglutination inhibition antibodies developed to similar levels in chickens after vaccination by either route. There was no obvious correlation between antibody and CMI responsiveness.

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.

Oral vaccination of chickens against Newcastle disease with V4 vaccine delivered on processed rice grains.

An international effort (sponsored by the Australian Centre for International Agricultural Research) is being made to develop oral vaccines that will protect village chickens against Newcastle disease. The vaccines being used are derivatives of the avirulent Australian V4 strain that have been selected for enhanced heat resistance. The present study, undertaken in Sri Lanka, used local processed (parboiled) rice as a vehicle for the vaccine. Chickens receiving two doses of vaccine on cooked, parboiled rice were completely protected against contact challenge with the virulent SL 88/1 Sri Lankan strain of Newcastle disease virus Chickens kept in contact with these vaccinated chickens were similarly protected. Lower levels of protection were achieved with vaccine given on uncooked parboiled rice. V4 vaccine administered intranasally also gave complete protection. Serums from vaccinated chickens that survived challenge were tested for haemagglutination-inhibition antibodies, using both vaccine virus and challenge virus as antigens. Titres were higher against vaccine virus.