الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In this study IBD vaccination regimes were evaluated against vvIBDV challenge and were compared, moreover studying pathogenic effect of experiment strain through pathological, immunohistochemical, molecular, weekly body weight gain and serological investigation furthermore monitoring IBD specific parameters as Bursa/ Body weight ratio and cytokines gene expression in bursal tissue. A total of 120-day-old white Leghorn SPF chickens were divided into 6 groups (each was20 birds). Two groups were vaccinated on either day 1 with an immune-complex vaccine. The second groups were vaccinated at days 9 and 14 of age using intermediate & intermediate plus IBD vaccines, respectively the balance groups are controls. All vaccines were administered according to the manufacturer’s instructions. The challenge was conducted on the 16th day of age using 105 EID50 /0.1 ml of a vvIBDV strain via the oculonasal route. The antibody immune response was monitored in all groups at 14, 21, 28, and 35 days of age by IBDV specific ELISA test. The performance, bursal gross lesions, challenge virus shedding detection and bursal histopathology were evaluated in vaccinated non challenged, vaccinated challenged and controls groups at days 21 and 28 of age. All vaccinated groups were protected against the vvIBDV challenge compared to the challenged control group which reveals 40% mortality. Both the immune-complex and live attenuated IBD vaccine groups showed lower BB ratio compared to the negative control group, while immune-complex showed slightly lower BB ratio compared to live attenuated as well as higher performance in challenged and/or non challenged groups which represented by higher body weight gain. The immune-complex vaccinated
groupsantibody titers were significantly higher compared to live attenuated. Whereas upon challenge, the intermediate/intermediate plus vaccinated challenged group showed higher antibody titers at 21 and 35th with the challenge virus detection and quantification on the 28th day but there was no virus shedding detection in immune-complex group which means that it induced sterile immunity. The immune-complex vaccinated challenged group developed milder bursal histopathological lesions and lesser apoptosis in bursa of Fabricius, thymus, spleen and kidney compared to live attenuated which represented by lower number of Caspase-3 positive cells by applyingapoptotic marker Caspase-3 staining on these organs at 12 days post challenge.