Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2000
Publication Date: N/A
Interpretive Summary: Coccidiosis is a major parasitic disease of poultry which costs a significant economic loss to the poultry industry worldwide. Ability to develop vaccine for coccidiosis would significantly reduce production loss due to this parasite and enhances US economy. In this study, ARS scientists developed a DNA vaccine for coccidiosis and demonstrated its protective effect against live coccidia challenge infection. Furthermore, this study demonstrated a feasibility of using chicken cytokines such as interferon-gamma and IL-2 as an vaccine adjuvant for the first time. These results establish a groundwork for future development of recombinant vaccine for avian coccidiosis and will help poultry industry to devise an efficient control strategy against avian coccidiosis in the near future.
A rabbit antiserum against an 18 - 27 kDa native protein fraction (F3) from E. acervulina merozoites identified a cDNA (3-1E) containing a 1,086 base pair insertion with an open reading frame of 170 amino acids (predicted molecular weight, 18,523). The recombinant 3-1E cDNA expressed in E. coli produced a 60 kDa fusion protein and a 23 kDa protein after factor Xa treatment of the fusion protein. Both proteins were reactive with the F3 antiserum by Western blot analysis. A rabbit antiserum against a synthetic peptide deduced from the amino acid sequence of the 3-1E cDNA reacted with a 27 kDa recombinant 3-1E protein expressed in Sf9 insect cells and a 20 kDa native protein expressed by E. acervulina sporozoites and E. tenella sporozoites and merozoites. By immunofluorescence staining, a monoclonal antibody produced against the E. coli expressed recombinant 3-1E protein reacted with sporozoites and merozoites of E. acervulina, E. tenella, and E. maxima. Spleen lymphocytes from E. acervulina immune chickens showed antigen specific proliferation and IFN-gamma production upon stimulation with the recombinant 3-1E protein indicating that it activates cell mediated immunity during coccidiosis. Immunization of chickens with either the E. coli or Sf9 expressed recombinant 3-1E protein, or direct injection of the 3-1E cDNA, induced protective immunity against live E. acervulina. Simultaneous injection of the recombinant 3-1E protein, or the 3-1E cDNA, with cDNAs encoding chicken IFN-gamma or IL-2/15 further enhanced protective immunity. These results indicate that the recombinant E. acervulina 3-1E cDNA or its polypeptide product may prove useful as vaccines against avian coccidiosis.