嵌合型猪圆环病毒（PCV1—2）及PCV2 ORF2真核表达质粒对商品猪的免疫保护

应用本实验室构建的嵌合型猪圆环病毒（PCV1—2）及真核表达质粒pcDNA3．1／V5-His-ORF2作为免疫原免疫母源抗体ELISA效价在0．07～0．60不等的商品猪，9头猪随机分为4组，1组（3头）肌肉注射免疫10^3.5 TCID50的PCV1-2／头，2组（2头）肌肉注射真核表达质粒200μg／头，3组（2头）肌肉注射空载体（pcDNA3．1）200μg／头，4组（2头）不免疫作为攻毒对照组。于免疫后42d，PCV1—2组及真核表达质粒组产生了PCV2抗体。免疫后42d所有组攻毒PCV2和PRRSV，剂量分别为2×10^4.5 TCID50／头和10^6 TCID50／头。攻毒后21d，攻毒对照组猪淋巴结比免疫组显著肿大，免疫组猪血清、淋巴结中PCV2病毒栽量低于对照组，攻毒对照组猪淋巴结中PCV2抗原含量高于免疫组。这些结果表明，嵌合型PCV1-2及真核表达质粒肌肉注射免疫商品猪后，对PCV2感染能产生保护性免疫应答，有可能成为候选疫苗。

A chimeric PCVI-2 live virus and recombinant plasmid expressing major nucleocapsid gene of PCV2 induce protective immunity against PCV2 infection in commercial pigs

A chimeric PCV1-2 live virus and eukaryotic expression vector pcDNA3.1/VS-His-ORF2 were vaccinated in commercial pigs with maternal antibody titers determined by ELISA varied from 0.07 to 0.60. A total of 9 pigs were randomly assigned to four groups,3 pigs in group 1 and 2 pigs in each other groups. Pigs in group 1 were vaccinated by intramuscular injection with 10^3.5 TCID50 of the chimeric PCV1-2 live virus. Pigs in group 2 were vaccinated by intramuscular injection with 200 μg of recombinant plasmid. Pigs in group 3 were vaccinated by intramuscular injection with 200 μg of pcDNA3.1. Pigs in group 4 were served as challenge control. Pigs in group 1 and group 2 had seroconverted to PCV2 capsid antibody by 42 days postvaccination （DPV）. All pigs were challenged intramuscularly with both 2 × 10^4.5 TCID50 of pathogenic PCV2 and 10^6TCID50 of PRRSV at 42 DPV. Necropsies were performed at 21 days post-challenge, the lymph nodes in the nonvaccinated but challenged pigs were larger than those of vaccinated pigs. The PCV2 genomic copy loads in lymph nodes and sera were reduced in vaccinated pigs. Moderate amounts of PCV2 antigen were detected in most lymphoid tissues of nonvaccinated pigs. These data indicated that when given intramuscularly in pigs,the chimeric PCV1- 2 live virus and recombinant plasmid induced protective immunity against PCV2 infection and could potentially serve as an effective vaccine.