In an attempt to investigate the immune efficacy ofa
DNA prime-
protein booster strategy against avian
coccidiosis with a chimeric construct, the Eimeria tenella
antigen gene (3-1E) and chicken
interferon gamma gene (ChIFN-gamma) were subcloned into the mammalian expression vector proVAX forming the plasmids proE and prol, and then linked by splicing overlap extension by polymerase chain reaction to construct the chimeric plasmid prolE; the chimeric
protein (rlE) was expressed in Escherichia coli harboring the constructed plasmid pGEX/IE. Broilers were administered two
intramuscular injections with the constructed
DNA vaccines (50 microg); in the
protein booster groups 100 microg of the rlE were given following the proIE prime. After challenge the proIE-vaccinated chickens showed the protective immunity as demonstrated by significantly reduced oocyst shedding compared with chickens immunized with proE, but the prolE
vaccine did not have an additive effect of increasing antibody titer and
body weight gain. The chickens in the rlE booster groups had significantly higher specific antibody responses than those immunized with prolE, and displayed further decreased oocyst shedding and increased
body weight gain. Taken together, these results indicate that ChIFN-gamma exerts an adjuvant effect coexpressed with 3-1E and provide the first evidence that the
DNA prime-
protein booster strategy is able to augment the protective efficacy of chimeric
DNA vaccine against challenge with Eimeria tenella.