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.