J Clin Invest. 2014 Feb;124(2):725-9. doi: 10.1172/JCI72676. Epub 2014 Jan 9.
The effector activity of antibodies is dependent on engagement with Fcγ receptors (FcγRs) and activation of the associated intracellular signaling pathways. Preclinical evaluation of therapeutic humanized or chimeric mAbs to study the interactions of their Fc regions with FcγRs is hampered by substantial structural and functional FcγR diversity among species. In this report, we used mice expressing only human FcγRs to evaluate the contribution of FcγR-mediated pathways to the neutralizing activity of an anti-anthrax toxin chimeric mAb. We observed that the protective activity of this mAb was highly dependent upon FcγR engagement, with minimal protection against anthrax toxin observed in FcγR-deficient mice following mAb administration. We generated anti-anthrax toxin mAbs with specific Fc domain variants with selectively enhanced affinity for particular human FcγRs and assessed their activity in FcγR-humanized mice. We determined that Fc domain variants that were capable of selectively engaging activating FcγRs substantially enhanced the in vitro and in vivo activity of anthrax toxin-neutralizing antibodies. These findings indicate that the application of Fc domain engineering is a feasible strategy to enhance toxin-neutralizing activity and suggest that engineered antitoxin antibodies will have improved therapeutic efficacy.
抗体的效应功能取决于与 Fcγ 受体（FcγRs）的结合以及相关细胞内信号通路的激活。为了研究治疗性人源化或嵌合单克隆抗体的 Fc 区与 FcγRs 的相互作用，需要对其进行临床前评估，但由于物种间 FcγR 存在实质性的结构和功能多样性，这一评估受到了阻碍。在本报告中，我们使用仅表达人 FcγRs 的小鼠来评估 FcγR 介导的途径对一种抗炭疽毒素嵌合单克隆抗体的中和活性的贡献。我们观察到，这种单克隆抗体的保护活性高度依赖于 FcγR 的结合，在给予单克隆抗体后，FcγR 缺陷型小鼠对炭疽毒素的保护作用极小。我们生成了具有特定 Fc 结构域变体的抗炭疽毒素单克隆抗体，这些变体对特定的人 FcγR 具有选择性增强的亲和力，并在 FcγR 人源化小鼠中评估了它们的活性。我们发现，能够选择性结合激活型 FcγR 的 Fc 结构域变体可显著增强炭疽毒素中和抗体的体外和体内活性。这些发现表明，Fc 结构域工程的应用是增强毒素中和活性的可行策略，并表明工程化抗毒素抗体将具有更高的治疗效果。
