Expression of IL-1β in transgenic Eimeria necatrix enhances the immunogenicity of parasites and promotes mucosal immunity against coccidiosis

Anticoccidial vaccines comprising living oocysts of <i>Eimeria tenella, Eimeria necatrix, Eimeria maxima</i>, and <i>Eimeria acervulina</i> are used to control coccidiosis. This study explored the potential of IL-1β to act as a molecular adjuvant for enhancing the immunogenicity of <i>Eimeria necatrix</i> and mucosal immunity. We engineered <i>E. necatrix</i> to express a functional chIL-1β (EnIL-1β) and immunized chickens with oocysts of the wild type (EnWT) and tranegenic (EnIL-1β) strains, respectively. The chickens were then challenged with EnWT oocysts to examine the immunogenicity-enhancing potential of chIL-1β. As expected, the oocyst output of EnIL-1β-immunized chickens was significantly reduced compared to those immunized using EnWT. No difference in body weight gain and lesion scores of EnIL-1β and EnWT groups was observed. The parasite load in the small intestine and caeca showed that the invasion and replication of EnIL-1β was not affected. However, the markers of immunogenicity and mucosal barrier, Claudin-1 and avian β-defensin-1, were elevated in EnIL-1β-infected chickens. Ectopic expression of chIL-1β in <i>E. necatrix</i> thus appears to improve its immunogenicity and mucosal immunity, without increasing pathogenicity. Our findings support chIL-1β as a candidate for development of effective live-oocyst-based anticoccidial vaccines.