Evaluation of immune protective efficacy of recombinant subunit vaccines based on Eimeria tenella EtAMA1 and EtSAG13

Avian coccidiosis is a severe parasitic disease caused by infection with species of the genus Eimeria, among which Eimeria tenella (E. tenella) is one of the most pathogenic. This study aimed to evaluate the protective efficacy of recombinant subunit vaccine candidates based on E. tenella apical membrane antigen 1 (EtAMA1) and surface antigen 13 (EtSAG13) against E. tenella infection in chickens. To this end, the EtAMA1 and EtSAG13 genes were cloned, the regions encoding the predicted signal peptides and transmembrane domains were removed, the sequences were optimized, and the resulting fragments were inserted into the pET-28a(+) vector. The recombinant subunit vaccine candidates rEtAMA1, rEtSAG13, and rEtAMA1-SAG13 were successfully constructed, and the corresponding recombinant proteins were expressed. Subsequently, animal experiments were conducted to evaluate the immunoprotective effects of the recombinant proteins at different doses (50 and 100 μg). The results showed that all three recombinant proteins were specifically recognized by sera from chickens infected with E. tenella and by polyclonal antibodies prepared in the laboratory. The group immunized with 50 μg rEtAMA1-SAG13 showed the greatest protective effect, with an anticoccidial index (ACI) of 175.48, indicating moderate anticoccidial efficacy. Histopathological analysis further revealed that cecal lesions were significantly alleviated in the immunized groups. Furthermore, serum levels of specific antibodies (IgG and IgY) and cytokines (IL-2, IL-6, IL-17, and IFN-γ) were significantly higher in the immunized groups than in the unimmunized group (P < 0.05). In conclusion, the recombinant subunit vaccine candidate combining EtAMA1 and EtSAG13 provides effective immune protection against E. tenella infection and holds promise for the prevention and control of chicken coccidiosis.