B亚型禽偏肺病毒病灭活疫苗对商品蛋鸡的免疫效果研究

Study on immune effect of inactivated vaccine of avian Metapneumovirus(Subtype B) disease on commercial layer chickens

为研究B亚型禽偏肺病毒病灭活疫苗对商品蛋鸡的免疫保护效果,本研究选取21日龄的商品蛋鸡,将本团队前期研制的B亚型禽偏肺病毒病灭活疫苗通过肌肉注射方式免疫蛋鸡(0.5 mL/只),并于首免后3周以相同剂量加强免疫1次。免疫后1周~6周每周采血,分离血清,采用ELISA检测及中和试验分别检测相应抗体,结果显示,初次免疫后6周,免疫组血清平均ELISA抗体效价达到1:73 522,平均中和抗体效价达到7.6log2。加强免疫后3周通过滴鼻的方式攻毒(aMPV/B LN16强毒滴鼻200μL,5 000 TCID50/只),观察攻毒后1 d~8 d蛋鸡的临床症状。结果显示,攻毒对照组蛋鸡发病率为92.3%,免疫组蛋鸡不发病;攻毒后1 d~8 d采集各组蛋鸡的鼻腔拭子,通过RT-qPCR方法检测病毒拷贝数,结果显示,免疫组蛋鸡鼻腔拭子中的病毒拷贝数较攻毒对照组下降约73.7%~95.0%;攻毒后9 d,采集各组蛋鸡的鼻甲、气管、肺脏制备病理切片后进行病理组织学观察,结果显示,攻毒对照组蛋鸡鼻甲、气管、肺脏出现不同程度的病理损伤,免疫组蛋鸡各组织器官未见明显病理变化。本研究结果首次表明,B亚型禽偏肺病毒病灭活疫苗对商品蛋鸡具有良好的免疫保护效果。本研究为商品蛋鸡的B亚型禽偏肺病毒病的防控和免疫程序的制定提供了参考。

In order to study the immune protection effect of avian metapneumovirus disease(subtype B) inactivated vaccine on commercial layer chickens, 21-day-old commercial layer chickens were selected and immunized intramuscularly with the inactivated vaccine developed in our previous work(0.5 m L per chicken), and the immunization was enhanced with the same dose three weeks after the first immunization. Blood samples were collected weekly 1 to 6 weeks after immunization, and the serum was separated and detected with ELISA assay and neutralizing antibody test. The results showed that the mean titer of serum ELISA antibody was 1:73522, and the mean neutralization antibody titer was 7.6 log2 at 6 weeks after the priming immunization. Three weeks after boosting immunization, the layer chickens were challenged with virulent a MPV/B LN16 strain by dropping nose(5000 TCID50 per chicken). Clinical symptoms of layer chickens were observed at 1 to 8 days after challenge. It was showed that the incidence of layer chickens in the challenge control group was 92.3%, while the layer chickens in the immunization group did not get sick. Choanal swabs of layer chickens in each group were collected at 1 to 5 days after challenge, and the virus copy number was detected by RT-q PCR. The results showed that the virus copy number in choanal swabs of layer chickens in the immune group decreased by about 73.7%-95.0% compared with the challenge control group. At 9 days after challenge, the turbinate, trachea and lung of layer chickens in each group were collected for histopathological observation. The turbinate, trachea and lung of layer chickens in the challenge group showed different degrees of pathological damage, while no obvious pathological change was found in the tissues and organs of layer chickens in the immunization group. The results of our study showed for the first time that the inactivated vaccine of avian metapneumovirus(subtype B) disease has a good immune protection effect on commercial layer chickens. This study provides a reference for the prevention and control of subtype B avian metapneumovirus disease in commercial laying hens and the formulation of immunization procedures.