Development of future strategies for vaccinating chickens against coccidiosis using recombinant antibodies, genes and peptides.

Lillehoj, H. S., Dalloul, R. A., and Park, D.W. Animal Parasitic Diseases Laboratory, Animal and Natural Resources Institute, U.S. Department of Agriculture, Beltsville, MD. 20705, (email address of presenting author: hlilleho@anri.barc.usda.gov )


Avian coccidiosis is caused by several different species of the intestinal protozoan parasites, Eimeria. Ability to develop novel control strategies against coccidiosis will reduce major economic losses to the poultry industry worldwide. Using functional genomics and molecular biology tools, we have now better understanding of host innate and acquired immunity to Eimeria. This paper will discuss various new strategies that we have taken to induce protective immunity to avian coccidiosis. Furthermore, novel vaccine delivery technologies are being applied to poultry to induce protective immunity against coccidioisis using recombinant proteins, genes and immunomodulators. For example, we have demonstrated that recombinant coccidian protein or recombinant DNA carrying a coccidian gene, when injected either into 18-day-old embryos using a commercial in ovo injector, Intelliject, or injected intramuscularly using a gene gun, reduced oocyst shedding and enhanced body weight gain. Addition of chicken cytokines or CpG oligodinucleotides further enhanced the vaccine-induced protection against coccidiosis. These results indicated that the type and dose of DNA vaccine and adjuvant influence the quality of the local immune response to DNA vaccination against coccidiosis. Another method that we are developing utilize recombinant antibodies whose specificities are directed against apical complex proteins involved in host cell invasion. Recombinant antibodies directed against apical complex antigen of Eimeria blocked sporozoite invasion of host cells and reduced oocyst shedding when injected in ovo at 18-day of embryonic development. Taken together, we have demonstrated how new generation vaccines and immunomodulators could be used to enhance host resistance against avian coccidiosis.