In the present study, the potential immunoprotective
role of infectious bursal disease (IBD) vaccine on
immunopotentiated chickens challenged with velogenic
viscerotropic Newcastle disease virus (vvNDV) genotype
VIId was investigated. The chickens were divided into five
groups vaccinated with NDV vaccine, but group (G1) was
kept as control unvaccinated birds. The G2 and G4 were
immunopotentiated using mannan oligosaccharides (MOS)
while G3 and G5 received MOS and IBD vaccine. The G1,
G2, and G3 were infected with vvNDV while G4 and G5
served as uninfected birds. The humoral response to NDV
vaccine was measured by hemagglutination inhibition test
while cellular response was estimated by chicken
interleukin-2 ELISA, total and differential leucocytic count,
bursa body weight index, and histopathological examination
of the bursae. The results revealed that the immunopotentiated
groups possessed a good cellular and humoral response to
vvNDV although the severity of histopathological lesions
was variable. The G3 had the best cellular and humoral response,
and IBD vaccine enhanced the immune response
against the infection with vvNDV. Histopathologically, the
typical bursal lesions of NDV were observed in G1 such as
lymphocytic depletion, acute inflammatory reaction, and degenerative
changes of the bursal follicles. In contrast, such
histopathological changes in the immunopotentiated groups
were less evident both in severity and prevalence, while the
immune reactive lymphoid hyperplasia was a prominent finding
in G4 and G5. In conclusion, the immunopotentiation of
the chickens as well as NDV and IBD vaccination improved
the bird immunity and diminished the immunosuppressive
effect of the vvNDV.