Transgenic Eimeria tenella Expressing Profilin of Eimeria maxima Elicits Enhanced Protective Immunity and Alters Gut Microbiome of Chickens

Coccidiosis is one of the most serious diseases of livestock and birds in the world. Vaccination with live-parasite anticoccidial vaccines with genetic manipulation improving the immunogenicity of vaccine strains would be the best means for controlling coccidiosis in breeder and layer stocks, even in fast-growing broilers. Profilin from apicomplexan parasites is the first molecularly defined ligand for Toll-like receptor 11 (TLR11) and TLR12 in mice and is a potential molecular adjuvant. Here, we constructed a transgenic Eimeria tenella line (Et-EmPro) expressing the profilin of Eimeria maxima, the most immunogenic species of chicken coccidia, and evaluated the adjuvant effects of EmPro on the immunogenicity of E. tenella. We found that immunization with the transgenic Eimeria parasites, compared with the wild type, elicited greater parasite antigen-specific cell-mediated immunity, characterized by increased numbers of interferon gamma (IFN-gamma)-secreting lymphocytes. The transgenic parasite also induced better protective immunity against E. tenella challenge than the wild type. In addition, the diversity of the fecal microbiome of the birds immunized with the transgenic parasite differed from that of the microbiome of the wildtype-immunized birds, indicating interactions of Eimeria with the gut microbiome of chickens. Our results showing enhanced immunogenicity of E. tenella by use of EmPro as a molecular adjuvant derived from the most immunogenic affinis species represent a large step forward in the development of the next generation of coccidiosis vaccines using Eimeria as a vaccine platform expressing molecular adjuvants and potentially other pathogen antigens against not only coccidiosis but also other infectious diseases.