Prokaryotic Expression of Eimeria magna SAG10 and SAG11 Genes and the Preliminary Evaluation of the Effect of the Recombinant Protein on Immune Protection in Rabbits.

Eimeria magna is a common coccidia in the intestines of rabbits, causing anorexia, weight loss, diarrhea, and bloody stools. This study cloned and determined the expression levels of four Eimeria surface antigens (EmSAGs) at different developmental stages and showed that EmSAG10 and EmSAG11 are highly expressed at the merozoite stage. Rabbits were immunized with r EmSAG10 and r EmSAG11 , and then challenged with E. magna after 2 weeks. Serum-specific antibodies and cytokine levels were detected using ELISA. Immune protection was evaluated based on the rate of the oocysts decrease, the output of oocysts ( p < 0.05), the average weight gain, and the feed: meat ratio. Our results showed that rabbits immunized with r EmSAG10 and r EmSAG11 had a higher average weight gain (62.7%, 61.1%), feed; meat ratio (3.8:1, 4.5:1), and the oocysts decrease rate (70.8%, 81.2%) than those in the control group, and also significantly reduced intestinal lesions. The specific IgG level increased one week after the first r EmSAG10 and r EmSAG11 immunization and was maintained until two weeks after the challenge ( p < 0.05). The TGF-β, IL-4, and IL-10 levels in the serum increased significantly after the secondary immunization with r EmSAG10 and r EmSAG11 , while the IL-2 levels increased significantly after the secondary immunization with r EmSAG11 (both p < 0.05), suggesting that r EmSAG10 can induce a humoral and cellular immunity, while r EmSAG11 can only induce a humoral immunity. Therefore, r EmSAG10 is a candidate antigen for E. magna recombinant subunit vaccines.