Eimeria tenella: IMP1 protein delivered by Lactococcus lactis induces immune responses against homologous challenge in chickens

Avian coccidiosis leads to severe economic losses on the global poultry industry. Immune mapped protein-1 (IMP1) is a novel membrane protein, and was reported to be a candidate protective antigen. However, production and utilization modes of IMP1 using Lactococcus lactis as delivery vector were not reported untill now. In the present study, Eimeria tenella IMP1 (EtIMP1) protein was expressed in L. lactis under the nisin-inducible promoter, and EtIMP1 protein was produced in cytoplasmic, cell wall-anchored and secreted forms. Each chicken was orally immunized with one of the three live EtIMP1-expressing lactococci three times at 2 weeks intervals (immunized group), or with live bacteria harboring empty vector (immunized control group). Chickens in immunized and immunized control group were challenged with E. tenella sporulated oocysts to assess the immune responses. The results showed that proliferative responses of peripheral blood T lymphocytes, mRNA expression levels of IL-2, IL-4, IL-10 and IFN-γ in spleen tissues, levels of serum IgG and secretory IgA (sIgA) in cecal lavage fluids from chickens in immunized group were all significantly elevated compared to that in immunized control group. All three the live EtIMP1-expressing lactococci significantly decreased oocyst shedding, alleviated pathological damage in cecum and improved weight gain compared with bacteria harboring empty vector. These results suggested EtIMP1 protein delivered by L. lactis might be a promising candidate in developing novel vaccines against Eimeria Infection.