柔嫩艾美耳球虫丝氨酸蛋白酶抑制剂基因核酸疫苗的免疫保护效果

Immune protective effect of Eimeria tenella Serpin gene DNA vaccine

目的观察柔嫩艾美耳球虫(Eimeria tenella,E.tenella)丝氨酸蛋白酶抑制剂(Serine protease inhibitor,Serpin)基因核酸疫苗对E.tenella感染雏鸡的免疫保护效果。方法取14日龄雏鸡,随机分为7组:pVAX1-Serpin高剂量组(100μg/只)、pVAX1-Serpin中剂量组(50μg/只)、pVAX1-Serpin低剂量组(25μg/只)、pVAX1组(50μg/只)、E.tenella卵囊组(15日龄时,口服5 000个卵囊/只,不加强免疫)、未免疫攻虫对照组(0.1 ml PBS)和未免疫未攻虫对照组(0.1 ml PBS),除E.tenella卵囊组外,均经胸肌注射免疫,21日龄时加强免疫1次,28日龄时,除未免疫未攻虫对照组外,均经口感染1×104个E.tenella孢子化卵囊。攻虫后第8天剖杀,计算各组的存活率、平均增重、相对增重率、盲肠病变减少率、卵囊减少率及抗球虫指数(Anticoccidial index,ACI)。结果未免疫攻虫对照组和pVAX1组的存活率分别为75%和70%,其余各组的存活率均为100%。pVAX1-Serpin高、中剂量组、E.tenella卵囊组和未免疫未攻虫对照组的平均增重2均较未免疫攻虫对照组显著增加(P<0.05),其中pVAX1-Serpin高剂量组相对增重率2达95.26%;E.tenella卵囊组、pVAX1-Serpin高、中剂量组的盲肠病变记分明显低于pVAX1组和未免疫攻虫对照组(P<0.05),前两组病变减少率较高;各免疫组卵囊产量均较未免疫攻虫对照组显著下降(P<0.05),pVAX1-Serpin高剂量组卵囊减少率达67.04%;各免疫攻虫组ACI值均高于未免疫攻虫对照组,其中E.tenella卵囊组最高(181.23),pVAX1-Serpin高剂量组次之(166.26),而pVAX1-Serpin中、低剂量组和pVAX1组均小于160。结论高剂量pVAX1-Serpin对鸡E.tenella感染具有一定的免疫保护作用。

Objective To observe the immunoprotection of Eimeria tenella serine protease inhibitor（Serpin） gene DNA vaccine on chickens infected with E.tenella.Methods Fourteen-day old chickens were randomly divided into seven groups.The chickens in groups 1,2 and 3 were injected i.m.with pVAX1-Serpin at high（100 μg）,moderate（50 μg） and low（25 μg） dosages respectively,while those in group 4 with pVAX1 at a dosage of 50 μg,and boostered at age of 21 d.The chickens in group 5 were immunized 0.5 × 104 E.tenella sporulated oocysts by oral route once at age of 15 d.However,the chickens in groups 6 and 7 were injected i.m.with 0.1 ml PBS.Except for those in group 7,all the chickens were orally challenged with 1 × 104 E.tenella sporulated oocysts at age of 28 d and killed on day 8 post challenge.The survival rates,mean weight gain,relative weight gain rates,decrease rates of lesion in cecum,oocyst decrease ratio and anticoccidial indexes（ACIs） of various groups were calculated.Results The survival rates in groups 7 and 4 were 75% and 70% respectively,while those in other groups were 100%.The mean weight gain 2 of chickens in groups 1,2,5 and 7 were significantly higher than that in group 6（P 0.05）.The relative weight gain rate 2 of chickens in group 1 reached 95.26%.The scores for lesions in cecum of chickens in groups 5,1 and 2 were significantly lower than those in groups 4 and 6（P 0.05）,while the decrease rates of lesion were relatively high in groups 5 and 1.The oocyst outputs of chickens in groups 1 ~ 5 decreased significantly as compared with the oocyst decrease ratio in group 6（P 0.05）,while the oocyst decrease ratio in group 1 was 67.04%.The ACIs of chickens in groups 1 ~ 5 were higher than those in group 6,of which that in group 5 was the highest（181.23）,and that in group 1（166.26） came second,while those in groups 2,3 and 4 were less than 160.Conclusion The pVAX1-Serpin at a high dosage showed a certain immune protection against E.tenella infection in chickens.