PATHOLOGICAL MONITORING OF VISCERAL LESIONS INDUCED BY VELOGENIC NEWCASTLE DISEASE IN EXPERIMENTALLY INFECTED BROILER CHICKENS AT DIFFERENT AGES WITH SPECIAL REFERENCE TO PULMONARY INFLAMMATORY CYTOKINES EXPRESSION

The present work aimed to study the impact of infection with a locally isolated vNDV genotype VII in commercial broiler chickens of different ages from a histopathological point of view with related changes in pulmonary cytokine expression. 100 commercial broiler chickens were allocated into 4 groups as follows; group 1 served as control non-infected group and three infected groups, were infected with 106 EID50 NDV at ages of 10,20, and 30 days. Tissue samples from different organs were collected at the 1st, 3rd, 5th, and 7th days post-inoculation for histopathological and immunohistochemical examination. Quantitative real-time RT-PCR for virus re-isolation as well as expression of IL-6 and IFN-γ genes estimation were performed on lung tissue collected at 3 dpi. RT-PCR for virus revealed increased virus load in the lungs of older birds and cytokines profiling revealed significant up-regulation of both IL-6 and IFN-γ genes in the groups that received infection at older ages. The severity and distribution of pathological lesions were directly proportioned to the age of infection and the time interval post-infection. Immunostaining of the viral antigen in the different tissues confirmed the pantropic nature of the virus.