Infectious bursal disease vaccine ameliorates velogenic Newcastle disease virus infection in immunopotentiated chickens

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.