Protective immunity against Eimeria infection using dendritic cells or exosomes

한국가금학회 심포지움(2012)

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Coccidiosis is a complex intestinal disease of major economic importance in chickens that is caused by multiple species of the protozoan, Eimeria. Conventional disease control methods have relied on prophylactic administration of drugs with anticoccidial activity, or on vaccination with live or attenuated parasites. However, alternative methods of disease mitigation are needed due to increasing government restrictions on the use of coccidiostats. An immunization strategy against Eimeria tenella infection was for the first time undertaken using parasite antigen(Ag)-loaded dendritic cells(DCs), or their derived exosomes, in the absence of free Ag. In a first clinical trial, chickens were immunized with E.tenella Ag-loaded DCs or exosomes and subsequently given a live parasite challenge infection to determine which immunization was most efficient in preventing disease. Immune parameters demonstrated that increased protective immunity against E.tenella infection was induced in chickens by immunization with Ag-loaded exosomes, compared with chickens immunized with Ag-loaded DCs or Ag alone. These findings led us to undertake a second clinical trial to evaluate Ag-loaded exososomes as potential vaccines against coccidiosis. Chickens were immunized with exosomes loaded with Ags from E.tenella, E.acervulina, and E.maxima. Subsequently, the animals were coinfected with oocysts from these three eimerian species. Cecal tonsils, Peyer’s patches and spleens of immunized and infected chickens had increased numbers of cells secreting IL-16, IL-2, and IFN-γ, greater Ag-stimulated proliferative responses, and higher numbers of Ag-reactive IgG- and IgA-producing cells following in vitro stimulation with the Ags, compared with the non-immunized/non-infected and non-immunized/infected controls. In addition, immunized and infected chickens had increased body weight gains, reduced feed conversion ratios, diminished fecal oocyst shedding, lessened intestinal lesion scores, and reduced mortality compared with the non-immunized/infected controls. These results suggest that successful vaccination may be possible against avian coccidiosis using exosomes derived from DCs incubated with Ags isolated from Eimeria species.
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