嵌合型猪圆环病毒(PCV1-2)灭活苗对商品猪免疫保护效力的研究

Chimeric PCV1-2 Inactivation Vaccine Evaluated in Commercial Pigs for Its Protective Efficacy against PCV2 Infection

运用多功能细胞电穿孔仪将本实验室构建的重组pSK-dPCVl-2质粒转染Dulac细胞，传代培养后获得具有稳定感染细胞的重组嵌合型猪圆环病毒PCV1-2。将该重组病毒灭活后与ISA206VG佐剂乳化制成灭活苗，通过免疫效力试验来评价该疫苗的免疫保护效力。将42日龄PCV2母源抗体水平较低的20头商品猪随机分成4组，另外2头作为健康对照组。分2次免疫，通过检测不同时间的间接免疫荧光抗体滴度、中和抗体滴度、平均日增重、攻毒后病毒血症以及解剖后病理变化和组织中的病毒载量等各项指标评价疫苗的免疫保护效果。结果显示：二免后14d，所有免疫组试验猪都表现为PCV2血清学阳性，且中和抗体水平在1／15～1／20。在猪的增重方面，免疫组猪和健康对照组猪的体重都有增加，而攻毒对照组猪的体重没有增加，且3个免疫组和攻毒对照组之间平均日增重差异显著（P〈0．05）。攻毒后21d扑杀试验猪，免疫组猪的淋巴结和各脏器的大体和显微病变都比攻毒对照组轻微。攻毒对照组的淋巴结出现多核巨细胞和嗜酸性粒细胞，且有多量的淋巴细胞缺失，免疫组未见多核巨细胞，淋巴细胞缺失也较少。淋巴结中PCV2病毒载量的log10在攻毒对照组为5．566±0．432，在10^（4.0）、10^（5.0）、10^（6.0）。TCID50·mL^（-1）免疫组分别为4．469±1.023、4．434±0．716、3．521±0．958，其中10^（5.0）、10^（6.0）TCID50·mL^（-1）免疫组与攻毒对照组差异显著（P〈O．05），但是，试验期间各试验组和健康对照组均未观察到明显的类似PMWS的临床症状。断奶仔猪免疫10^（5.0）TCID52·mL^（-1）以上嵌合型猪圆环病毒PCV1-2灭活苗可以有效地抵抗PCV2b／1B／Jiangsu／JingJiang／2012／11／08病毒感染。

In this study, Dulac cells were electroporated with the recombinant plasmid pSK- dPCV1-2 constructed in our laboratory to obtain chimeric PCV1-2 virus by passage cultures. The inactivated vaccine of chimeric PCV1-2 virus emulsified with ISA 206 VG adjuvant was vaccinated commercial pigs to evaluate its protective efficacy against PCV2 infection. Twenty 42-day-old conventional pigs were randomly assigned to four groups of five pigs each, and other two pigs served as healthy control. The immune efficacy was evaluated by detecting indirect immunofluo- rescent assay （IFA） antibody titers, neutralizing antibody titers, growth parameters, viremiapost-challenge, gross pathology and histopathology. By 35 days post-vaccination （DPV）, all vac- cinated pigs had seroconversion to antibody against PCV2 and developed high IFA antibody titers and neutralizing antibody titers at 1/15-1/20. In growth parameters, the average daily weight gain （ADWG） was increased in three immunized groups and the mock group, but there were no gains in challenge control group. Comparison of ADWG of vaccinated pigs with that of challenge pigs revealed statistically significant difference between them （P〈0.05）. By 21 days post-chal- lenge, gross and microscopic lesions of lymph nodes and lungs in non-vaccinated but challenged pigs were significantly more severe than those found in vaccinated groups. There were muhinu- cleated giant cells, a number of eosinophilia and lymphocyte depletion in lymph nodes in non-vac- cinated but challenged pigs. There were no muhinucleated giant cells and less lymphocyte deple- tion in vaccinated pigs. The log10 of PCV2 viral copy loads detected in lymph nodes in non-vacci- nated but challenged pigs were 5. 566 q-0. 432, in vaccinated pigs with 104.0, 105.0, 106.0 TCID50 · mL were4.469±1.023, 4. 434±0. 716,3. 521±0. 958, respectively. Comparison be- tween pigs vaccinated with 105.o, 106.0 TCID50 · mL-1 and challenging only pigs, the differences were significant （P〈0.05）, but there were no clinical syndrome during the whole experiment pe- riod. The results illuminated that the inactivated chimeric PCV1-2 could induce protective immu- nity against PCV2b/1B/Jiangsu/Jingjiang/2012/11/08 infection effectively.