Development of transgenic lines of Eimeria tenella expressing M2e-enhanced yellow fluorescent protein (M2e-EYFP).

Eimeria parasites are obligate intracellular apicomplexan protists that can cause coccidiosis, resulting in substantial economic losses in the poultry industry annually. As the component of anticoccidial vaccines, seven Eimeria spp. of chickens are characterized with potent immunogenicity. Whether genetically modified Eimeria spp. maintains this property or not needs to be verified. In this study, two identical transgenic lines of Eimeria tenella were developed by virtue of single sporocyst isolation from a stably transfected population expressing fused protein of M2 ectodomain of avian influenza virus (M2e) and enhanced yellow fluorescent protein (EYFP). The chromosomal integration and expression of M2e-EYFP were confirmed by Southern blot, plasmid rescue and Western blot analysis. We found that the reproduction of transgenic parasites was higher than that of the parental strain. Chickens challenged with wild type E. tenella after immunization with 200 oocysts of transgenic parasites had similar performance compared to those in non-immunized and non-challenged group. In another trial, the performance of transgenic parasite-immunized birds was also comparable to that of the Decoquinate Premix-treated chickens. These results suggest that this transgenic line of E. tenella is capable of inducing potent protection against homologous challenge as a live anticoccidial vaccine. Taking together, our study indicates that transgenic eimerian parasites have the potential to be developed as a vaccine vehicle for animal use in the future.