Serum, intestinal lavage fluid, and spleen samples were collected 10 d after the second immunization for ELISA, flow cytometry, cell proliferation assays, and qRT-PCR experiments. Body weight and clinical signs were recorded daily for 7 d after infection, and fecal samples were collected from d 4 to 7 for oocyst shedding analysis. Cecal tissues were collected for cecal lesion scoring and hematoxylin and eosin examination at 7 d postinfection.