Construction of Eimeria tenella multi-epitope DNA vaccines and their protective efficacies against experimental infection.

The search for effective vaccines against chicken coccidiosis remains a challenge because of the complex organisms with multiple life cycle stages of Eimeria . Combination of T-cell epitopes from different stages of Eimeria life cycle could be an optimal strategy to overcome the antigen complexity of the parasite. In this study, 4 fragments with concentrated T-cell epitopes from the sporozoite antigen SO7 and the merozoite antigen MZ5-7 of Eimeria tenella were cloned into eukaryotic expression vector pVAX1 in different forms, with or without chicken cytokines IL-2 or IFN-γ genes as genetic adjuvants, to construct multistage, multi-epitope DNA vaccines against Eimeria tenella . Transcription and expression of the multi-epitope DNA vaccines in vivo were detected by reverse transcription-PCR (RT-PCR) and Western blot. On the basis of survival rate, lesion score, body weight gain, oocyst decrease ratio and the anti-coccidial index (ACI), Animal experiments were carried out to evaluate the protective efficacy against Eimeria tenella. Results showed the constructed DNA vaccines were transcribed and translated successfully in vivo . Animal experiment showed that the multi-epitopes DNA vaccines were more effective to stimulate immune response than single fragment. Compared with the DNA vaccines composed with less T-cell epitopes, DNA vaccine pVAX1-m1-m2-s1-s2 containing 4 fragments with concentrated T-epitopes provided the highest ACI of 180.39. DNA vaccines composed of antigens from two developmental stages were more effective than the single-stage ones. Especially DNA vaccine pVAX1-m1-m2-s1-s2 provided the most effective protection with the ACI of 180.39. Furthermore, cytokines IL-2 or IFN-γ could improve the efficacy of the multi-epitope DNA vaccines significantly. Overall, pVAX1-m1-m2-s1-s2-IFN-γ provided the most effective protection with the ACI of 189.92. The multi-epitope DNA vaccines revealed in this study provide new candidates for Eimeria vaccine development. [ABSTRACT FROM AUTHOR]