Chimeric DNA vaccines encoding Eimeria acervulina macrophage migration inhibitory factor (E.MIF) induce partial protection against experimental Eimeria infection.

Abstract

Chimeric DNA vaccines co-expressing Eimeria acervulina macrophage migration inhibitory factor (E.MIF) and chicken IL-2 (IL-2) or interferon-γ (IFN-γ) were constructed and their efficacies against E. acervulina were evaluated. The open reading frame (ORF) of E.MIF was cloned from E. acervulina merozoites and subcloned into the eukaryotic expression vector pVAX1 with chicken cytokine gene IFN-γ or IL-2 to construct the DNA vaccines pVAX-E.MIF-IFN-γ, pVAX-E.MIF-IL-2 and pVAX-E.MIF. The in vivo transfection of the target genes was detected by use of reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Immunizations were carried out by vaccinating chickens twice with a dose rate of 100 μg intramuscularly. Seven days post second immunization, all chickens except the unchallenged control group were challenged orally with 1 × 105 sporulated oocysts of E. acervulina. Seven days later, the duodenum was collected. The results showed that the target genes were expressed effectively in vivo. DNA vaccines and the recombinant E.MIF protein could alleviate body weight loss and duodenal lesions significantly compared to the control groups. Furthermore, pVAX-E.MIF-IL-2 and pVAX-E.MIF-IFN-γ induced anticoccidial indexs (ACIs) of 179.12 and 170, respectively, which were significantly higher than that of pVAX-E.MIF (ACI = 162.31). Our results demonstrated that E.MIF is a potential vaccine candidate against E. acervulina and chicken IFN-γ or IL- 2 may be used as genetic adjuvants to improve the efficacies of DNA vaccines against avian coccidiosis.