Immunoprotective Efficacy of Recombinant Protein rEnApiAP2 against Coccidia in Chicken
The recombinant protein rEnApiAP2 of Eimeria necatrix alone and in combination with the recombinant proteins rEtGAM56 or rEtGAM59 of E.tenella were used to immunize chicks.The groups immunized with rEtGAM56 or rEtGAM59 alone,and the groups unimmu-nized and challenged(UC)or unimmunized and unchallenged were used as controls.The chicks were infected with E.necatrix or E.tenella,respectively.The survival rate,bloody stool,weight gain(WG),relative weight gain(RWG),lesion score(LC),oocyst reduction(OR),an-ticoccidial index(ACI)and serum antibody level(SAL)were used as indexes to evaluate the im-mune protective effect of rEnApiAP2 alone and in combination with rEtGAM56 or rEtGAM59,respectively.The results showed that the survival rate of all groups was 100％,the total number of bloody stools excreted by chicks in the immunized groups was less than that in the UC group,and the WG of the immunized groups were higher than that of UC group.Among the groups im-munized with rEnApiAP2 alone,the RWG,LC and ACI in the group immunized with low dos-age was the highest(82.36％,73.88％and 155.26 respectively),and the LC was the lowest(1.71).Among the groups infected with E.necatrix,the ACI in the co-immunization groups was higher than that in the groups immunized with rEnApiAP2 or rEtGAM alone,of which the ACI in the group co-immunized with rEnApiAP2 and rEtGAM56 was the highest(169.83).A-mong the groups infected with E.tenella,the ACI in the group immunized with rEnApiAP2(128.37)was lower than that of the group immunized with rEtGAM56(130.12)and the group immunized with rEtGAM59(151.88).The ACI in the group co-immunized with rEnApiAP2 and rEtGAM59(141.62)was close to that in the group immunized with rEtGAM59 alone,and the ACI in the group co-immunized with rEnApiAP2 and rEtGAM56(115.46)was lower than that in the group immunized with rEtGAM56 alone.The SAL of all immunized groups was signifi-cantly higher than that of the control group(P＜0.05).In conclusion,rEnApiAP2 protein had good immunogenicity and was able to induce effective immune protection against E.necatrix,and co-immunization with rEtGAM could enhance its immune protection against E.necatrix.These results laid a foundation to develop a recombinant coccidiosis vaccine.
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