Optimization of Immunization Procedure for Eimeria tenella DNA Vaccine pVAX1-pEtK2-IL-2 and Its Stability

Purpose To seek for the optimal immunization procedure of DNA vaccine pVAX1-pEtK2-IL-2 which was produced via cloning pEtK2 antigen gene of Eimeria tenella (E. tenella) and chicken IL-2 (chIL-2) gene into expression vector pVAX1. Methods The doses, routes, times of inoculation and ages of the first inoculation of chickens were optimized. The stability of the vaccine, including store temperature and time, was also explored. The effects of the protective immunity against challenge infection were assessed according to average body weight gain, survival rate, oocyst output, lesion score and the anti-coccidial index (ACI). Results The results suggested that intramuscular inoculation was the most efficient route to elicit immune response and 80 mu g was the optimal immune dose. Two time injections induced more effective protection compared to single injection, the effect of the first injection at 14 days old was optimal. The immune efficacy of the vaccine stored at different time and temperature was very stable. Conclusions The optimal immunization procedure for Eimeria tenella DNA vaccine pVAX1-pEtK2-IL-2 is 80 mu g DNA, two time injections at 14 and 21 days old, respectively, by intramuscular inoculation.