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Title: Immunostimulatory complexes containing Eimeria tenella antigens and low toxicity plant saponins induce antibody response and provide protection from challenge in broiler chickens

item ALEXUK, P
item Barfield, Ruth
item Fetterer, Raymond

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2009
Publication Date: 10/8/2009
Citation: Berezin, V.E., Bogoyavlenskyi, A.P., Khudiakova, S.S., Alexuk, P.G., Omirtaeva, E.S., Zaitceva, I.A., Tustikbaeva, G.B., Barfield, R.C., Fetterer, R.H. 2010. Immunostimulatory complexes containing Eimeria tenella antigens and low toxicity plant saponins induce antibody response and provide protection from challenge in broiler chickens. Veterinary Parasitology. 167:28-35.

Interpretive Summary: Poultry coccidiosis is the result of several different species of a protozoan intestinal parasite which causes considerable annual losses to the poultry industry. The primary control for the disease is through application of medications in the feed as birds are raised in confinement housing. The controls by medications are becoming less effective because of increased resistance to the drugs and less desirable due to concerns about drugs possibly remaining in the meat and within the environment. Vaccination of poultry against coccidiosis with defined antigens is one of the most desirable ways to control the disease but practical vaccines are lacking. The use of novel methods to deliver vaccine candidates offers promise in the fight against poultry coccidiosis. ISCOMs are a unique, multimolecular structure formed by encapsulating antigens, lipids and plant saponins and have been shown to be an effective delivery system for various kinds of antigens. The current research continues studies utilizing ISCOMs to vaccinate against poultry coccidiosis. ISCOMs of various formulations were assessed in their ability to stimulate serum antibody response and to protect chickens from coccidiosis. Variables that were tested included, the amount of antigen, type of saponin and the most desirable route of vaccination. The results of the study indicated that a single intranasal immunization with 5-10 ug of antigen gave the maximum antibody response and resulted in a greater than 90% protection of chickens against a challenge infection with coccidia. The results also indicate that ISCOMs have value as a delivery system for vaccines directed against avian coccidosis.

Technical Abstract: Immunostimulating complexes (ISCOMs) are unique multimolecular structures formed by encapsulating antigens, lipids and triterpene saponins and are one of the most successful antigen delivery systems for microbial antigens. In the current study, both the route of administration and the antigen concentration of ISCOMs, containing partially purified saponins from native plants, were evaluated in their ability to stimulate humoral immunity and to protect chickens against a challenge infection with Eimeria tenella. Broiler chickens were immunized with ISCOM preparations containing E.tenella antigens and the partially purified saponins Gg6, Ah6 and Gp7 isolated from Glycyrrhiza glabra, Aesculus hippocastanum and Gipsophila paniculata respectively. The effect of the route of administration, dose of antigen and type of saponin used for construction of ISCOMs were evaluated for ability to stimulate serum IgG and IgM and to protect chickens to homologous challenge. A single intranasal immunization was the most effective route for administering ISCOMs although the in ovo route was also quite effective. Dose titration experiments demonstrated efficacy after single immunization with ISCOMs but maximum effects were observed when ISCOMs contained 5-10 ug antigen. Immunization of birds by any of the three routes with E. tenella antigens alone or antigens mixed with alum hydroxide adjuvant resulted in lower serum antibody levels and reduced protection upon challenge relative to immunization with ISCOMs. Overall the results of this study confirm that significant immunostimulation and protection to challenge are achieved by immunization of chickens with ISCOMs containing partially purified saponins and native E. tenella antigens and suggest that ISCOMs may be successfully used to develop a safe and effective vaccine for prevention of avian coccidiosis.