Institut National de Santé Et de Recherche Médicale Unité Mixte de Recherche-Santé, Nantes, France.
MAbs. 2013 Jan-Feb;5(1):47-55. doi: 10.4161/mabs.22697. Epub 2012 Dec 5.
Antagonist antibodies targeting CD28 have been proposed as an alternative to the use of CD80/86 antagonists to modulate T cell responses in autoimmunity and transplantation. Advantages would be the blockade of CD28-mediated co-stimulatory signals without impeding the co-inhibitory signals dependent on CD80 interactions with CTLA-4 and PD-L1 that are important for the control of immune responses and for the function of regulatory T cells. Anti-CD28 antibodies are candidate antagonists only if they prevent access to the CD80/86 ligands without simultaneously stimulating CD28 itself, a process that is believed to depend on receptor multimerization. In this study, we evaluated the impact of different formats of a potentially antagonist anti-human CD28 antibody on T cell activation. In particular, we examined the role of valency and of the presence of an Fc domain, two components that might affect receptor multimerization either directly or in the presence of accessory cells expressing Fc receptors. Among monovalent (Fab', scFv), divalent (Fab'2), monovalent-Fc (Fv-Fc) and divalent-Fc (IgG) formats, only the monovalent formats showed consistent absence of induced CD28 multimerization and absence of associated activation of phosphoinositol-3-kinase, and clear antagonist properties in T cell stimulation assays. In contrast, divalent antibodies showed agonist properties that resulted in cell proliferation and cytokine release in an Fc-independent manner. Conjugation of monovalent antibodies with polyethylene glycol, α-1-antitrypsin or an Fc domain significantly extended their in vivo half-life without modifying their antagonist properties. In conclusion, these data indicate that monovalency is mandatory for maintaining the antagonistic activity of anti-CD28 monoclonal antibodies.
靶向 CD28 的拮抗剂抗体被提议作为替代 CD80/86 拮抗剂的方法，以调节自身免疫和移植中的 T 细胞反应。其优势在于阻断 CD28 介导的共刺激信号，而不阻碍依赖于 CD80 与 CTLA-4 和 PD-L1 相互作用的共抑制信号，这些信号对于控制免疫反应和调节性 T 细胞的功能很重要。只有当抗 CD28 抗体能够阻止与 CD80/86 配体的结合，而不同时刺激 CD28 本身时，它们才是潜在的拮抗剂，这一过程被认为依赖于受体的多聚化。在这项研究中，我们评估了不同形式的潜在拮抗剂抗人 CD28 抗体对 T 细胞激活的影响。特别是，我们研究了价态和 Fc 结构域的存在对受体多聚化的作用，这两个因素可能直接或在表达 Fc 受体的辅助细胞存在的情况下影响受体的多聚化。在单价（Fab'，scFv）、二价（Fab'2）、单价-Fc（Fv-Fc）和二价-Fc（IgG）形式中，只有单价形式显示出一致的 CD28 多聚化缺失和相关的磷酸肌醇-3-激酶激活缺失，以及在 T 细胞刺激测定中明显的拮抗剂特性。相比之下，二价抗体表现出激动剂特性，导致细胞增殖和细胞因子释放，而不依赖于 Fc。将单价抗体与聚乙二醇、α-1-抗胰蛋白酶或 Fc 结构域缀合，显著延长了其体内半衰期，而不改变其拮抗剂特性。总之，这些数据表明单价是维持抗 CD28 单克隆抗体拮抗活性的必要条件。
