Eimeria species parasites as novel vaccine delivery vectors: anti-Campylobacter jejuni protective immunity induced by Eimeria tenella-delivered CjaA.

Vaccination of poultry against coccidiosis caused by the Eimeria species is almost entirely based upon varied formulations of live parasites. The recent development of a series of protocols that support genetic complementation by transfection in Eimeria now provides an opportunity to utilise live anticoccidial vaccines to deliver additional vaccinal antigens. The capacity of Eimeria tenella to express an exogenous antigen and induce an immune response during in vivo infection which is protective against subsequent bacterial challenge has been tested here using the anti-Campylobacter jejuni vaccine candidate CjaA. Using restriction enzyme mediated integration (REMI) a transgenic E. tenella population expressing CjaA and the fluorescent reporter mCitrine has been developed. Vaccination of specific pathogen free chickens by single or multiple oral inoculation of E. tenella-CjaA oocysts induced 91% and 86% immune protection against C. jejuni challenge compared with unvaccinated and wild-type E. tenella vaccinated controls (p<0.001). Increasing vaccination number had no significant influence on the magnitude of protection. These results support the hypothesis that eimerian parasites can be developed as multivalent vaccine vectors and encourage the extension of these studies.