الفهرس 
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Abstract
Bacterial oligodeoxynucleotide containing cytosine guanine motifs (CpG-ODN) has been reported to induce immunostimulatory activity against a variety of bacterial, viral, and protozoan infections in a variety of vertebrate species. The objective of this study was to investigate the dose-dependent immunomodulatory effect of CpG ODN on Salmonella Enteritidis bacterin in broiler chickens. Two hundreds one-day-old broiler chicks, divided into 5 groups, were used in this study. Three groups were immunized with Salmonella Enteritidis bacterin adjuvanted with different doses of CpG ODN (50µg, 100µg and 200µg). The control groups included a group that was immunized with Salmonella Enteritidis bacterin adjuvanted with aluminium hydroxide and a non-immunized group. The intestinal colonization, cellular responses, mucosal and systemic immune responses of immunized chickens were measured at different intervals, until 42 days of age. At two weeks of post-immunization, 20 chicks from each group were orally challenged by Salmonella Enteritidis fresh bacterial culture (1.2x108 CFU/ml). The survival rates and the pathological changes of challenged chickens in the different groups were monitored for extra 10 days. Compared to the aluminium hydroxide adjuvanted bacterin the CpG-ODN adjuvant bacterin induced significant protection and improved survival rate of challenged chickens. Also Salmonella Enteritidis was not recovered from the intestinal tract of vaccinated challenged groups. There was a significant dose-dependent immunostimulatory effect of CPG-ODN on the level of secretory IgA and the induced mucosal responses. The 200-CpG ODN group showed the highest IgA response followed by 100-CpG ODN group then the 50-CpG ODN and the aluminium hydroxide groups (P < 0.05). Also, cellular interactions were remarkably reduced in the liver and intestine of CpG ODN-treated chickens. No inflammatory cellular infiltrations were seen in the liver and intestine of 200-CpG ODN treated group. In conclusion, the presented findings have shown the significant immunostimulatory effect of CpG-ODN and its effect on Salmonella Enteritidis bacterin in controlling Salmonella infection in broiler chickens.