Hemostasis Branch, Division of Plasma Protein Therapeutics, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
Department of Otorhinolaryngology-Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
J Thromb Haemost. 2017 Apr;15(4):721-734. doi: 10.1111/jth.13649. Epub 2017 Mar 2.
Essentials Fc-fusion increases a therapeutic's half-life, but FcγR interactions may impact immunogenicity. Species-specific Fc-FcγR interactions allow for mechanistic in vivo studies using mouse models. Fc fusion modulates the immune response to factor IX in hemophilia B mice by eliciting Th1 bias. This model could inform future studies of IgE-associated anaphylaxis in hemophilia B patients.
Background Fc fusion is a platform technology used to increase the circulating half-life of protein and peptide therapeutics. However, there are potential immunological consequences with this approach, such as changes in the molecule's immunogenicity as well as possible interactions with a repertoire of Fc receptors (FcR) that can modulate immune responses. Objectives/Methods Using a mouse hemophilia B (HB) model, we compared the immune responses to infusions of recombinant human factor IX (hFIX) and hFIX fused to mouse IgG2a-Fc (hFIX-mFc). The mFc was employed to allow species-specific Fc-FcγR interactions. Results Although treatment with hFIX-mFc altered the early development of anti-FIX IgG, no significant differences in anti-FIX antibody titers were observed at the end of the treatment regimen (5 weeks) or upon anamnestic response (5 months). However, treatment with hFIX-mFc elicited higher FIX-neutralizing antibody levels and resulted in reduced IgE titers compared with the hFIX-treated group. Additionally, differences in plasma cytokine levels and in vitro CD4 T-cell responses suggest that whereas hFIX treatment triggered a Th2-biased immune response, hFIX-mFc treatment induced Th1-biased CD4 T cells. We also show that hFIX-mFc bound to soluble FcγRs and engaged with FcγRs on different cell types, which may impact antigen presentation. Conclusions These studies provide a model system to study how Fc-fusion proteins may affect immune mechanisms. We used this model to demonstrate a plausible mechanism by which Fc fusion may modulate the IgE response to hFIX. This model may be appropriate for investigating the rare but severe IgE-mediated anaphylaxis reaction to hFIX infusions in HB patients.
目的/方法：利用小鼠血友病 B (HB) 模型，我们比较了输注重组人凝血因子 IX (hFIX) 和与人 IgG2a-Fc 融合的 hFIX (hFIX-mFc) 后的免疫反应。使用 mFc 可允许种属特异性的 Fc-FcγR 相互作用。结果：尽管 hFIX-mFc 的治疗改变了早期抗 FIX IgG 的发展，但在治疗方案结束时（5 周）或在回忆反应时（5 个月），并未观察到抗 FIX 抗体滴度的显著差异。然而，与 hFIX 治疗组相比，hFIX-mFc 治疗组产生了更高的 FIX 中和抗体水平，并导致 IgE 滴度降低。此外，血浆细胞因子水平和体外 CD4 T 细胞反应的差异表明，尽管 hFIX 治疗引发了 Th2 偏向性免疫反应，但 hFIX-mFc 治疗诱导了 Th1 偏向性 CD4 T 细胞。我们还表明，hFIX-mFc 与可溶性 FcγR 结合，并与不同细胞类型上的 FcγR 相互作用，这可能影响抗原呈递。结论：这些研究提供了一个研究 Fc 融合蛋白如何影响免疫机制的模型系统。我们使用该模型证明了 Fc 融合可能调节 hFIX 免疫球蛋白 E 反应的一种合理机制。该模型可能适用于研究 HB 患者中罕见但严重的 hFIX 输注引起的 IgE 介导的过敏反应。
