Construction of DNA vaccines and their induced protective immunity against experimental Eimeria tenella infection

Abstract

In an attempt to construct a DNA vaccine against chicken coccidiosis, the TA4 gene of Eimeria tenella strain BJ was ligated to the mammalian expression vector pcDNA3.1/Zeo(+) to give pcDNA3.1-TA4 (pcDT). Then, Et1A (E. tenella refractile body gene) was ligated to it, upstream, aiming to be expressed in fusion with TA4, giving pcDNA3.1-Et1A-TA4 (pcDET). The constructed DNA vaccines were given to broilers intramuscularly 10-15 min after the breasts had been pretreated with 25% sucrose solution. At 7 days after the second vaccination, chickens were challenged with 3×104 sporulated oocysts of E. tenella BJ. The chickens were killed and the lesion scores of the ceca, the relative bodyweight gains and the numbers of oocysts in the ceca of each group of chickens were calculated at day 8 post-inoculation. Results indicated that both pcDT and pcDET could induce protective immunity against coccidial challenge. Their use could obviously reduce oocyst output and alleviate chicken body-weight decrease due to coccidial infection. An anti-coccidial index of 160 was achieved with a treatment of 50 μg pcDET and 100 μg pcDT. © Springer-Verlag 2004.