Key Points Anti-FH Ab enhances aHUS-associated mutant FH in binding to C3b and DAA. Cell surface regulatory function of FH mutants is restored by addition of anti-FH. The complement system plays an important role in our innate immune system. Complement activation results in clearance of pathogens, immune complex, and apoptotic cells. The host is protected from complement-mediated damage by several complement regulators. Factor H (FH) is the most important fluid-phase regulator of the alternative pathway of the complement system. Heterozygous mutations in FH are associated with complement-related diseases such as atypical hemolytic uremic syndrome (aHUS) and age-related macular degeneration. We recently described an agonistic anti-FH mAb that can potentiate the regulatory function of FH. This Ab could serve as a potential new drug for aHUS patients and alternative to C5 blockade by eculizumab. However, it is unclear whether this Ab can potentiate FH mutant variants in addition to wild-type (WT) FH. In this study, the functionality and potential of the agonistic Ab in the context of pathogenic aHUS-related FH mutant proteins was investigated. The binding affinity of recombinant WT FH and the FH variants, W1183L, V1197A, R1210C, and G1194D to C3b was increased upon addition of the potentiating Ab and similarly, the decay-accelerating activity of all mutants is increased. The potentiating anti-FH Ab is able to restore the surface regulatory function of most of the tested FH mutants to WT FH levels on a human HAP-1 cell line and on sheep erythrocytes. In conclusion, our potentiating anti-FH is broadly active and able to enhance both WT FH function as well as most aHUS-associated FH variants tested in this study.

中文翻译：

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阐明强效抗因子 H 抗体对非典型溶血性尿毒症综合征相关因子 H 变体的影响

关键点 Anti-FH Ab 增强了 aHUS 相关突变体 FH 与 C3b 和 DAA 的结合。FH 突变体的细胞表面调节功能通过添加抗 FH 恢复。补体系统在我们的先天免疫系统中起着重要作用。补体激活导致病原体、免疫复合物和凋亡细胞的清除。几种补体调节剂保护宿主免受补体介导的损伤。因子 H (FH) 是补体系统替代途径最重要的液相调节剂。FH 中的杂合突变与补体相关疾病有关，例如非典型溶血性尿毒症综合征 (aHUS) 和年龄相关性黄斑变性。我们最近描述了一种激动性抗 FH mAb，它可以增强 FH 的调节功能。这种抗体可以作为 aHUS 患者的潜在新药，并可以替代依库珠单抗对 C5 的阻断。然而，除了野生型 (WT) FH 之外，尚不清楚该 Ab 是否可以增强 FH 突变变体。在这项研究中，研究了激动性抗体在致病性 aHUS 相关 FH 突变蛋白的背景下的功能和潜力。重组 WT FH 和 FH 变体 W1183L、V1197A、R1210C 和 G1194D 对 C3b 的结合亲和力在添加增强抗体后增加，类似地，所有突变体的衰变加速活性增加。增强的抗 FH Ab 能够将大多数测试的 FH 突变体的表面调节功能恢复到人类 HAP-1 细胞系和绵羊红细胞上的 WT FH 水平。综上所述，