Tanikawa T, Ishikawa T, Maekawa T, Kuronane K, Imai Y
Laboratory of Microbiology and Immunology and the Global COE Program, University of Shizuoka School of Pharmaceutical Sciences, Shizuoka-shi, Shizuoka, Japan.
Scand J Immunol. 2008 Oct;68(4):414-22. doi: 10.1111/j.1365-3083.2008.02153.x.
Immunoglobulin A (IgA) is considered to play a major role in protection of the mucosal surface. However, its immunological and biological properties have not been extensively studied because the production of IgA class monoclonal antibodies (mAbs) is difficult. We compared the properties of IgA and IgG mAbs against Shiga toxin B subunits (Stx1B). These mAbs were secreted from hybridomas that had been produced from mice after intranasal immunization with recombinant Stx1B and cholera toxin. The dose response curves for the binding of the IgA (clone G2G7) and IgG (clone D11C6) mAbs to immobilized Stx1B were similar, as revealed on ELISA. The majority of the IgA mAb formed dimers while the IgG mAb was monomeric, as judged by immunoblot analysis. The IgG mAb completely inhibited the binding of Stx1B to Burkitt's lymphoma cell line Ramos, while the inhibition by the IgA mAb was only partial. The IgG mAb was able to neutralize the cytotoxicity of Stx1 holotoxin towards Vero cells, whereas the IgA mAb was not. The binding affinity of each binding site was compared by means of surface plasmon resonance analysis involving a capture method, with which the binding of soluble Stx1B to immobilized mAb was detected. The association rate was similar but the dissociation rate was twofold faster in the case of the IgA mAb, resulting in twofold higher affinity of the IgG mAb. These results suggest that one can obtain high affinity IgA mAb but toxin neutralization is another challenge as to therapeutic antibodies of the IgA class.
免疫球蛋白A（IgA）被认为在保护黏膜表面方面发挥着主要作用。然而，由于IgA类单克隆抗体（mAb）的生产困难，其免疫学和生物学特性尚未得到广泛研究。我们比较了针对志贺毒素B亚基（Stx1B）的IgA和IgG单克隆抗体的特性。这些单克隆抗体由用重组Stx1B和霍乱毒素经鼻内免疫的小鼠产生的杂交瘤分泌。ELISA结果显示，IgA单克隆抗体（克隆G2G7）和IgG单克隆抗体（克隆D11C6）与固定化Stx1B结合的剂量反应曲线相似。免疫印迹分析表明，大多数IgA单克隆抗体形成二聚体，而IgG单克隆抗体为单体。IgG单克隆抗体完全抑制Stx1B与伯基特淋巴瘤细胞系Ramos的结合，而IgA单克隆抗体的抑制作用仅为部分抑制。IgG单克隆抗体能够中和Stx1全毒素对Vero细胞的细胞毒性，而IgA单克隆抗体则不能。通过涉及捕获方法的表面等离子体共振分析比较了每个结合位点的结合亲和力，利用该方法检测可溶性Stx1B与固定化单克隆抗体的结合。结合速率相似，但IgA单克隆抗体的解离速率快两倍，导致IgG单克隆抗体的亲和力高两倍。这些结果表明，可以获得高亲和力的IgA单克隆抗体，但对于IgA类治疗性抗体而言，毒素中和是另一项挑战。
