中文摘要：

以本实验室分离的猪胸膜肺炎放线杆菌血清2型（Actinobacillus pleuropneumoniae serotype2，APP-2）菌株HB08的基因组为模板，扩增了2871bp的APP毒素Ⅱ的结构基因apxⅡA，并克隆到pET-28a原核表达载体中构建重组表达质粒pET28aⅡA，转化到大肠杆菌（Escherichia coli）BL21（DE3），经SDS—PAGE和Western blot分析表明，表达的重组蛋白具有良好的反应活性。将表达的蛋白经或不经复性处理，与纯化的天然毒素Ⅱ分别免疫昆明小鼠，同时设PBS空白对照组，每组12只．间隔2周免疫2次，采血检测其抗体效价，二免后2周用致死剂量的APP血清7型（APP-7）菌株（1．08×10^8CFU（菌落形成单位，colony form unit）／只）腹腔攻击。结果显示，复性蛋白组的保护率为83.3％，非复性蛋白组的保护率为58.3％，天然毒素蛋白对照组保护率为91．7％，空白对照组小鼠全部死亡，说明复性的重组毒素Ⅱ具有良好的免疫原性。

英文摘要：

The structural gene encoding Apx Ⅱ toxin （apxHA） was amplified from the genomic DNA of Actinobacillus pleuropneumoniae serotype 2 （APP-2） strain HB08 and cloned into the prokaryotic expression vector pET-28a. SDS-PAGE and Western blotting analysis showed that the apx/L4 gene was expressed in Escherichia coli BL21 （DE3） and the expression products could react with Apx Ⅱ antibodies. The recombinant Apx Ⅱ was purified from the inclusion bodies. Kunming mice were intraperitoneally vaccinated twice with an interval of two weeks using unfolded and refolded recombinant proteins, the native Apx Ⅱ extracted from the cultural supernatant of APP strain of serotype 7 （APP-7） and PBS, respectively. Serum antibody was examined by Apx Ⅱ -specific ELISA two weeks post every vaccination. Two weeks after the second vaccination, mice were challenged intraperitoneally with a lethal dose of APP-7 （1.08× 10^8CFU （colony form unit） per mouse）. The protection rate reached 91.7% in the native Apx Ⅱ group, 83.3 % in the refolded recombinant protein group and 58.3 % in the misfolded recombinant protein group, while all the mice in the PBS group died in 36 h post challenge. The data revealed that the refolded recombinant Apx Ⅱ had excellent immunogenicity and could elicit protection from the lethal challenge of APP.