Respiratory and GIT tract immune responses of broiler chickens following experimental infection with Newcastle disease's virus.

Newcastle disease causes a lymphoproliferative response in the tracheal and intestinal mucosa of the infected birds. In this study, the Hitchner B1 and I-2 vaccine and challenging of ND field strains were used to evaluate the populations of T lymphocyte subsets infiltrated intestinal and tracheal, also to shed some light on cell-mediated immune response using enzyme-linked immunosorbent assay (ELISA) detecting chicken's serum interferon-γ. Three hundred-day-old broilers were randomly divided into four groups. Groups 1 and 2 received I-2 and B1 vaccines, respectively, while groups 3 and 4 were challenged-unvaccinated and unchallenged-unvaccinated groups. Blood samples were taken from five random chicks and were then tested with ELISA test. Three chicks of each group were euthanized after vaccine administration and also challenging with acute virus. Interferon-γ changes were significant in time (p < 0.001). Totally, there was no significant difference between I-2 and B1 groups. The number of CD3+, CD4+, and CD8+ cells of I-2 and B1 vaccinated group's intestine and the trachea samples was significantly increased compared with the negative control group (p < 0.001). The results indicated the significant increase in CD4+ and CD8+ in intestinal and tracheal tissues, while the level of interferon-γ of the vaccinated group was more than the unvaccinated one. Finding no significant differences between the vaccinated groups indicated the potential of both vaccines in producing CD4+ and CD8+ in the tracheal and intestinal tissues and the equality of interferon-γ production in the sera.