Combined oral immunization with probiotics Entercoccus faecalis delivering surface-anchored Eimeria tenella proteins provide protective efficacies against homologous infection in chickens

BACKGROUND AND OBJECTIVES: Avian coccidiosis is an intestinal parasitic disease exerting a highly negative impact on the global poultry industry. The aim of the present study is to evaluate the immune protective efficacies against Eimeria tenella infection in chickens orally immunized with combined recombinant probiotics Entercoccus faecalis (E. faecalis) delivering surface-anchored E. tenella proteins. METHODS: Four kinds of novel probiotics vaccines that surface-expressing four Eimeria tenella (E. tenella) proteins EtAMA1, EtIMP1, EtMIC2 and Et3-1E were produced, respectively. The expression of four target proteins on the surface of recombinant bacteria was detected by Western blot and indirect immunofluorescence assay (IFA). Then the four kinds of recombinant E. faecalis were combined to immunize chickens via oral route in different combinations. The immunizations were performed three times at two-week intervals, and each for three consecutive days. After immunizations, chickens in each immunized group were orally challenged with E. tenella sporulated oocysts. The immune responses and protective efficacies against homologous infection were evaluated. RESULTS: The results showed that three or four live recombinant E. faecalis induced effective antigen-specific humoral, intestinal mucosal immune responses, stimulated peripheral T lymphocytes proliferation, and displayed partial protections against homologous challenge as measured by cecal lesions, oocyst shedding, and body weight gain (BWG). Notably, higher levels of protective efficacies were observed when the four recombinant E. faecalis delivering target proteins were combined. CONCLUSION: Chickens orally administrated with three or four, especially the four combined recombinant E. faecalis stimulated specific immune responses, which provided anti-coccidial effects. This study offers an idea for future development of novel vaccines based on multi-antigens delivered by probiotic bacteria.