The Induction of Protective Immunity against Experimental Eimeria tenella Infection using Serum Exosomes

Authors: DEL CACHO, E - University Of Zaragoza; Lillehoj, Hyun; GALLEGO, MARGARITA - University Of Zaragoza; QUILEZ, JOAQUIN - University Of Zaragoza; LILLEHOJ, ERICK - University Of Maryland Eastern Shore (UMES); SANCHEZ-ACEVEDO, CARIDAD - University Of Zaragoza

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2016
Publication Date: 5/3/2016
Publication URL: https://handle.nal.usda.gov/10113/5258372
Citation: Del Cacho, E., Lillehoj, H.S., Gallego, M., Quilez, J., Lillehoj, E.P., Sanchez-Acevedo, C. 2016. The induction of protective immunity against experimental Eimeria tenella Infection using serum Exosomes. Veterinary Parasitology. 224:1–6.

Interpretive Summary: Enteric pathogens cause major economic losses due to nutrient malabsorption and poor growth. Avian coccidiosis is caused by several different Eimeria parasites which infect the intestine and cause major weight losses. There are no recombinant vaccines which can protect chickens against avian coccidiosis. In this study which ARS scientists collaborated with scientists in Spain, a novel vaccination strategy using parasite antigen-stimulating complex of antigen presenting cells called dendritic cells was evaluated. The parasite antigen-containing immunity-stimulating complex was effective in eliciting protective immune response against avian coccidiosis. This represents an effective way to stimulate intestinal immunity against enteric pathogen and is the first time this finding is reported for avian coccidiosis. These results suggest the possibility of producing an effective, parasite-free vaccine strategy against avian coccidiosis under field conditions using parasite antigen-derived immune stimulating complex.

Technical Abstract: Avian coccidiosis is caused by Eimeria, a unicellular, apicomplexan protist which primarily infects intestinal epithelia resulting in nutrition malabsorption and reduced growth of commercial poultry. Vaccination of chickens with exosomes isolated from antigen presenting cells and containing parasite antigens (Ags) represents a promising alternative strategy to control avian coccidiosis, but is restricted in its commercial application due to limitations on production scale-up for mass immunization programs. Here, we report the biochemical and physiologic characteristics of exosomes derived from serum of E. tenella-infected chickens and their feasibility for inducing protective immunity to experimental coccidiosis. Exosomes isolated from the serum of E. tenella-infected chickens contained a subset of protein Ags found in the intact parasite. Serum-derived exosomes containing these E. tenella Ags localized to the intestine and spleen following intramuscular injection into naïve chickens. In vitro ELISPOT assays revealed increased numbers of IL-2-, IL-4-, IL-6-, and IFN-'-secreting cells in the intestine and spleen of exosome-administered chickens, compared with vehicle controls. Pre-immunization of chickens with serum exosomes from E. tenella-infected chickens increased both body weight gain and feed conversion efficiency, and reduced both fecal parasite shedding and gut lesion scores following parasite infection, compared with vehicle controls. Finally, immunization with CD80+ serum exosomes stimulated greater numbers of cytokine-producing cells, and higher levels of protective immunity to E. tenella infection, compared with CD80– exosomes. These results suggest the possibility of producing an effective, parasite-free vaccine against avian coccidiosis under field conditions using serum-derived CD80+ exosomes containing parasite Ags.