StxB/HlyA(CT)融合蛋白的分泌表达和StxB在小鼠内的特异免疫反应

Secretive Export of StxB/HlyA (CT) Fusion Protein and B Subunit Specific Antibody Responses in Mice

本文将志贺氏毒素B亚单位(StxB)与大肠杆菌溶血素A的C末端(HlyA(CT))相融合,蛋白StxB/HlyA(CT)不仅能在大肠杆菌中分泌到胞外,而且也能从aroA突变的减毒鼠伤寒沙门氏菌中分泌出去。当用高拷贝质粒pUC18作载体时,上述融合蛋白对宿主细胞有毒性,但以低拷贝质粒pBR322取代之后,该融合蛋白不再对宿主细胞产生任何不利影响。融合蛋白StxB/HlyA(CT)无论是在aerobactin启动子、或是在β-内酰胺酶启动子的控制下,均能在大肠杆菌和鼠伤寒沙门氏菌中恒定地表达,并能输送至胞外。以表达StxB/HlyA(CT)的aroA突变的鼠伤寒沙门氏菌SL3261免疫小鼠,引起了显著的B亚单位特异的粘膜和血清抗体反应。首次报道了融合至大肠杆菌溶血素A的C末端的外源多肽能从沙门氏菌中分泌至胞外,这种分泌多肽且能刺激抗原的特异性免疫反应。

In this study, the Shiga toxin B subunit has been fused to haemolysin A C-ter-minus. The fusion protein StxB/HlyA(CT) can be exported to the external medium not only from E. coli K-12 but also from S. typhimurium aroA strain SL3261. When the plasmid pUC18 was used as vector, StxB/HlyA(CT) was toxic to hosts. But the fusion protein was stable and safe to hosts when the pUC18 was replaced with pBR322. The fusion protein can be expressed and exported to the external medium under either the aerobactin promoter or β-lactomase promoter. Oral and i. p. immunization of mice with StxB/HlyA(CT) carrying S. typhimurium aroA strain SL3261 resulted in significant B subunit specific mucosal and serum antibody responses. This the first report demonstrating that foreign polypeptides fused to the 23kD C-terminus of E. coli haemolysin A can be exported from attenuated Salmonella Vaccine strains and that such exported polypeptides can result in antigtn specific immune responses.