具核梭杆菌外膜囊泡的免疫原性

Immunogenicity of outer membrane vesicles of Fusobacterium nucleatum

摘要:

【目的】 评价模拟正常肠道和肿瘤微环境的pH条件下制备的具核梭杆菌外膜囊泡(outer membrane vesicles, OMVs)的安全性和免疫原性，为后期开发基于外膜囊泡的具核梭杆菌疫苗奠定基础。【方法】 采用超高速离心和密度梯度离心方法制备在不同pH条件下生成的外膜囊泡，建立人结肠癌细胞HCT116、人正常结肠上皮细胞HCoEpiC、小鼠巨噬细胞Raw264.7感染模型；采用3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT]和细胞活性检测试剂盒(cell counting kit-8, CCK-8)检测细胞增殖的影响；用流式细胞仪和贴壁细胞原位荧光检测细胞凋亡情况；通过小鼠的血常规检测体内安全性；通过酶联免疫吸附法(enzyme-linked immunosorbent assay, ELISA)检测免疫原性；通过细胞黏附抑制实验检测免疫保护效果。【结果】 酸性条件生成的外膜囊泡(acidic outer membrane vesicles, aOMVs)和中性条件生成的外膜囊泡(neutral outer membrane vesicles, nOMVs)对人正常结肠上皮细胞HCoEpiC、人结肠癌细胞HCT116和小鼠巨噬细胞Raw264.7的细胞增殖均无显著性影响，也不能引起细胞凋亡；aOMVs和nOMVs在浓度为25 μg/mL处理红细胞时仍未见明显的溶血现象产生，并且在小鼠体内血常规和全血检测指标数据均在正常范围内；aOMVs和nOMVs均具有免疫原性，可有效减少具核梭杆菌在结肠癌细胞DLD-1上的黏附，aOMVs抗体性能优于nOMVs抗体。【结论】 aOMVs和nOMVs的安全性均良好，均具有免疫原性，aOMVs优于nOMVs。

Abstract:

[Objective] To evaluate the safety and immunogenicity of outer membrane vesicles (OMVs) of Fusobacterium nucleatum prepared under the pH conditions simulating normal intestinal and tumor microenvironments, and to lay a foundation for the later development of OMV-based vaccines against F. nucleatum. [Methods] Ultra-high-speed centrifugation and density gradient centrifugation were employed to isolate the OMVs of F. nucleatum under different pH conditions. Three models of human colorectal cancer cells (HCT116), human colonic epithelial cells (HCoEpiC), and mouse macrophage Raw264.7 were infected by F. nucleatum. The cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell counting kit-8 (CCK-8) assay, and the cell apoptosis were evaluated by flow cytometry and in situ fluorescence of adherent cells. The safety in vivo was detected by blood routine and whole blood index of mice. The enzyme-linked immunosorbent assay (ELISA) was employed to examine the cell immunogenicity, and the adhesion inhibition assay was conducted to assess cell immunoprotection. [Results] Acidic outer membrane vesicles (aOMVs) and neutral outer membrane vesicles (nOMVs) had no significant different effects on the proliferation or apoptosis of HCoEpiC, HCT116, and Raw264.7 cells. Both nOMVs and aOMVs at a concentration of 25 μg/mL did not lead to significant hemolysis of red blood cells, and the routine blood and whole blood test results of the mice treated with aOMVs were within the normal ranges. The results demonstrated that both aOMVs and nOMVs exhibited good immunogenicity and reduced the adhesion of F. nucleatum to colon cancer cells DLD-1. The aOMVs outperformed nOMVs regarding immunogenicity. [Conclusion] Both aOMVs and nOMVs had good safety and immunogenicity, and aOMVs were superior to nOMVs.