Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 28, 1998
Publication Date: N/A
Technical Abstract: The purpose of the present study was to evaluate direct DNA injection as a way to elicit protective immune responses in chickens against coccidiosis. Preliminary studies showed that tissue expression of luciferase could be detected in one-day-old and one-week-old chickens immunized by jet-gun injection with a plasmid DNA expressing luciferase under control of a CMV promoter. DNAs encoding three different Eimeria acervulina antigens (EASZ240, EAMZ250, EASZ22) were then cloned into the pCMV vector and injected either singly or in combination into leg muscle of one-day-old and seven-day-old outbred chickens. The chickens were then challenged at 5 weeks of age with a high dose of E. acervulina oocysts and evaluated one week later by protection against weight loss and intestinal lesions associated with coccidiosis. Plasma was collected from all chickens and tested for nitrite + nitrate concentration and for antibodies (Ab) against the recombinant proteins. Chickens immunized with either pEAMZ250 or pEASZ22 plasmid DNA showed nearly complete protection against challenge infection as measured by weight gain compared to control groups immunized with non-recombinant pCMV plasmid. Direct DNA injection elicited antigen-specific Ab, but there did not appear to be any correlation with protective immunity. However, plasmid DNA-injected chickens that were protected against coccidiosis exhibited elevated plasma NO2 and NO3 levels. Studies are now underway to improve gene expression whereby lower amounts of recombinant plasmid DNA can be used to elicit immunity against coccidiosis.