Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford, UK.
J Mol Biol. 2012 Jun 29;420(1-2):1-7. doi: 10.1016/j.jmb.2012.04.002. Epub 2012 Apr 5.
Serum IgG is a potent inhibitor of monoclonal antibody (mAb) binding to the cell-surface Fcγ receptors (FcγRs), which mediate cytotoxic and phagocytic effector functions. Here, we show that this competition can be eliminated, selectively, by the introduction to serum of (i) an enzyme that displaces Fc from FcγRs and (ii) a modification present in the therapeutic mAb that renders it resistant to that enzyme. Specifically, we show that (i) EndoS (endoglycosidase S) cleaves only complex-type glycans of the type found on IgG but (ii) is inactive against an engineered IgG Fc with oligomannose-type glycans. EndoS thus reduces FcγR binding of serum IgG, but not that of engineered mAb. Introduction of both the engineered mAb and endoglycosidase in serum leads to a dramatic increase in FcγR binding compared to the introduction of mAb in serum alone. Antibody receptor refocusing is a general technique for boosting the effector signal of therapeutic antibodies.
血清 IgG 是一种有效的单克隆抗体（mAb）与细胞表面 Fcγ 受体（FcγRs）结合的抑制剂，该受体介导细胞毒性和吞噬作用的效应功能。在这里，我们表明，通过向血清中引入（i）一种从 FcγRs 上置换 Fc 的酶和（ii）一种存在于治疗性 mAb 中的修饰，可以有选择性地消除这种竞争，该修饰使 mAb 对该酶具有抗性。具体来说，我们表明（i）内切糖苷酶 S 仅切割 IgG 上存在的那种复杂型糖链，但（ii）对具有寡甘露糖型糖链的工程化 IgG Fc 无活性。因此，内切糖苷酶 S 降低了血清 IgG 与 FcγR 的结合，但不降低工程化 mAb 的结合。与仅向血清中引入 mAb 相比，向血清中同时引入工程化 mAb 和内切糖苷酶 S 可显著增加 FcγR 的结合。抗体受体重聚焦是一种增强治疗性抗体效应信号的通用技术。
