Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 1999
Publication Date: N/A
Interpretive Summary: Avian coccidiosis, an intestinal disease caused by single-cell protozoan parasites that infect the intestine of birds, is estimated to cost the U.S. poultry industry $350 million annually. The parasites are partially controlled by the use of anticoccidials that are fed in the feed of domestically raised chicken and turkeys, but increased resistance of the coccidia to the anticoccidial compounds currently cleared for use with these birds has caused concern in the poultry industry. Development of a recombinant vaccine against the parasites would be a viable alternative to use of anticoccidials, but an effective delivery system is needed to insure that a protective immune response can be elicited in birds against the parasite. In a series of experiments it was shown that a plasmid DNA promotor (designated pCMV-LUC) would give increased expression of a luciferase gene when injected into the thigh skeletal muscle of 1 and 4 week-old broiler chickens. These results indicate that this promotor coul be used in gene vaccination techniques to introduce DNA plasmids containing recombinant coccidial antigens that could elicit protective immune response to coccidial infection.
Skeletal muscle from one-day and four-week-old male broiler chickens was evaluated for luciferase expression after jet-gun injection with DNA plasmids encoding the luciferase gene driven by either RSV or 2 different CMV promotors. Birds of both ages were injected with 100ug of DNA plasmid in the upper thigh muscle. Tissue samples were taken at 24-hr intervals, quick frozen in liquid nitrogen, and then stored at -70 C until digested for fluorometric analysis. Comparison of luciferase expression showed that one CMV promoter (designated pCMV-LUC) produced a higher degree of expression at 1-8 days post-injection (PI) in birds from both age groups than did the RSV and other CMV promotor. The highest degree of expression for both bird-age groups occurred in tissue collected at 1-5 days PI. Expression decreased in tissue collected at later time periods, but was still measurable at 7-15 days PI. These results indicated that the CMV promotor could be incorporated into a DNA plasmid delivery system to immunize chickens with recombinant antigens.