{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T06:05:01Z","timestamp":1789538701979,"version":"build-2803163510"},"reference-count":36,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T00:00:00Z","timestamp":1789516800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>\n                    Coccidiosis, caused by protozoan parasites of the genus\n                    <jats:italic>Eimeria<\/jats:italic>\n                    , remains a major enteric disease that requires effective antigen-specific cellular immunity for protection. In this study, we evaluated genetically engineered\n                    <jats:italic>Toxoplasma gondii<\/jats:italic>\n                    , an apicomplexan parasite closely related to\n                    <jats:italic>Eimeria<\/jats:italic>\n                    , as a live-vector platform for antigen delivery and induction of protective immunity against\n                    <jats:italic>Eimeria<\/jats:italic>\n                    infection. Recombinant RH\u0394\n                    <jats:italic>ku80<\/jats:italic>\n                    strains expressing ovalbumin (OVA) alone or fused with four tandem copies of complement fragment C3d (OVA-C3d\n                    <jats:sub>4<\/jats:sub>\n                    ) were generated using a CRISPR\/Cas9-mediated strategy. Stable transgene integration and expression were confirmed by PCR, immunofluorescence assay, western blotting, and whole-genome resequencing. Phenotypic characterization demonstrated that expression of OVA or OVA-C3d\n                    <jats:sub>4<\/jats:sub>\n                    did not significantly affect parasite invasion, intracellular replication, plaque formation, or acute virulence in mice. Immunization with recombinant parasites induced robust antigen-specific cellular immune responses, as evidenced by increased frequencies of IFN-\u03b3\u2013secreting splenocytes following stimulation with OVA-derived CD4\n                    <jats:sup>+<\/jats:sup>\n                    and CD8\n                    <jats:sup>+<\/jats:sup>\n                    \u00a0T-cell epitopes. Fusion with C3d\n                    <jats:sub>4<\/jats:sub>\n                    modestly influenced immune responses by\u00a0altering antibody isotype profiles in an inversely dose-dependent manner, although total antibody titers were not substantially increased. Protective efficacy was evaluated using challenge infection with OVA-expressing\n                    <jats:italic>Eimeria<\/jats:italic>\n                    falciformis. Mice immunized with RH\u0394\n                    <jats:italic>ku80-OVA<\/jats:italic>\n                    or RH\u0394\n                    <jats:italic>\n                      ku80-OVA-C3d\n                      <jats:sub>4<\/jats:sub>\n                    <\/jats:italic>\n                    exhibited significantly reduced oocyst shedding and alleviated intestinal pathology compared with unimmunized controls. However, no significant additional protective benefit was observed for the C3d\n                    <jats:sub>4<\/jats:sub>\n                    -containing recombinant strain compared with the OVA-expressing strain under the experimental conditions tested. Collectively, these findings demonstrate that recombinant\n                    <jats:italic>T. gondii<\/jats:italic>\n                    can serve as an effective\u00a0live-vector platform for inducing antigen-specific cellular immunity and partial\u00a0protection against OVA-expressing\n                    <jats:italic>E. falciformis<\/jats:italic>\n                    challenge. This study highlights\u00a0the potential of protozoan-based vaccine platforms and supports a potential\u00a0contribution of antigen-specific cellular immunity to protection against coccidiosis.\n                  <\/jats:p>","DOI":"10.3389\/fimmu.2026.1915667","type":"journal-article","created":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T05:33:03Z","timestamp":1789536783000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Recombinant Toxoplasma gondii expressing OVA confers antigen-specific protection against Eimeria falciformis"],"prefix":"10.3389","volume":"17","author":[{"given":"Yingying","family":"Sun","sequence":"first","affiliation":[{"name":"State Key Laboratory of Veterinary Public Health and Safety; Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yilin","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Veterinary Public Health and Safety; Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fujie","family":"Xie","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Veterinary Public Health and Safety; Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zongyue","family":"Tao","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Veterinary Public Health and Safety; Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sixin","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Veterinary Medicine, Southwest University","place":["Chongqing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaotong","family":"Yao","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Veterinary Public Health and Safety; Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University","place":["Beijing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tingyu","family":"Zhang","sequence":"additional","affiliation":[{"name":"State Key Laboratory 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