The C5a/C5aR1 axis as a regulator of autoreactive IgG antibody glycosylation in pemphigoid diseases

C5a/C5aR1 轴作为类天疱疮疾病中自身反应性 IgG 抗体糖基化的调节剂

• 批准号: 279184395
• 负责人: Professor Dr. Jörg Köhl
• 金额: --
• 依托单位: Institut für Systemische Entzündungsforschung (ISEF)
• 依托单位国家: 德国
• 项目类别: Clinical Research Units
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/279184395?language=en
• 关键词: C5a; C5aR1; axis; regulator; autoreactive

Deposition of autoreactive IgG antibodies (AAb) at the dermal-epidermal junction and activation of complement are hallmarks of PD. While AAb deposition is necessary to drive tissue inflammation and skin blistering, it is not sufficient, as AAb deposition often precedes clinical symptoms for a long time. In addition to the IgG isotype, the composition of the IgG Fc glycan structure determines the inflammatory potential of AAbs. More specifically, IgG Fc-glycan structures terminating with galactosyl- or additional sialyl-residues suppress, whereas agalactosylated (G0) IgG drive inflammation. In the 1st FP, we found in an experimental model of active epidermolysis bullosa acquisita (EBA) a higher frequency of G0 IgG1 AAbs in EBA-sensitive C57BL6/S than in EBA-resistant C57BL6/J mice. This increase in G0 IgG1 AAbs was associated with a decrease in single galactosylated as well as galactosylated and sialylated AAbs. Surprisingly, we observed a strong impact of complement on AAb Fc glycosylation, in particular of C5a, the small cleavage fragment of C5. Similar to the EBA-resistant mice, the frequency of G0 IgG1 AAb was low in C5a receptor 1 (C5aR1)-deficient mice and was associated with a high frequency of anti-inflammatory, highly galactosylated IgG1 AAbs, some of which were also highly sialylated. Moreover, the C5a/C5aR1 axis not only controlled the glycosylation pattern of IgG1 but also that of IgG2 AAbs and collagen type VII (COL7)-specific IgG2 serum levels, which were significantly lower in C5ar1-/- than in WT mice. Importantly, C5ar1-/- mice were completely protected from the development of blister formation during the entire observation period. Preliminary data further suggest that the C5a/C5aR1 axis regulates the expression of 1,4 galactosyltransferase 1 in B cells. Based on these findings, we hypothesize that the IgG Fc glycan pattern changes in clinically overt PD from an anti-inflammatory to a pro-inflammatory phenotype. Further, we propose that this change increases the potency of IgG AAbs to activate complement locally in the skin. The increased local generation of C5a activates the C5aR1 axis on innate immune cells, inducing a chain of events, ultimately suppressing galactosylation and sialylation of IgG AAbs. During the 2nd FP, we aim to further delineate the IgG Fc glycosylation pattern in experimental and clinical PD and define the molecular mechanisms underlying C5aR1-mediated regulation of AAb glycosylation in PD. Translationally, we aim to evaluate the impact of preventive and therapeutic C5aR1 targeting in the active EBA mouse model, with a particular emphasis on IgG AAb production and N-glycan composition.We expect that the IgG Fc glycan patterns in PD patients will serve as a novel biomarker to identify patients at risk for relapse and guide immunotherapy. Preventive and therapeutic C5aR1 targeting in the active EBA model may pave the way for clinical use of C5aR1 inhibitors in PD, some of which are about to be marketed.

自身反应性IgG抗体（AAb）在真皮-表皮交界处的沉积和补体的激活是PD的标志。虽然AAb沉积是驱动组织炎症和皮肤起泡所必需的，但这是不够的，因为AAb沉积通常在临床症状之前很长一段时间。除了IgG同种型之外，IgG Fc聚糖结构的组成决定了AAb的炎症潜力。更具体地，以半乳糖基或额外的唾液酸残基终止的IgG Fc-聚糖结构抑制炎症，而无半乳糖基化（G 0）IgG驱动炎症。在第一次FP中，我们发现在活动性获得性大疱性表皮病（EBA）实验模型中，对EBA敏感的C57 BL 6/S小鼠中G 0 IgG 1 AAbs的频率高于对EBA耐药的C57 BL 6/J小鼠。G 0 IgG 1 AAb的增加与单个半乳糖基化以及半乳糖基化和唾液酸化AAb的减少相关。令人惊讶的是，我们观察到补体对AAb Fc糖基化，特别是C5的小切割片段C5 a的强烈影响。与EBA耐药小鼠相似，C5 a受体1（C5 aR 1）缺陷小鼠中G 0 IgG 1 AAb的频率较低，并且与抗炎、高度半乳糖基化IgG 1 AAb的频率较高相关，其中一些也是高度唾液酸化的。此外，C5 a/C5 aR 1轴不仅控制IgG 1的糖基化模式，还控制IgG 2 AAbs和VII型胶原蛋白（COL 7）特异性IgG 2血清水平的糖基化模式，C5 ar 1-/-小鼠的血清水平显著低于WT小鼠。重要的是，在整个观察期内，C5 ar 1-/-小鼠完全免受水疱形成的发展。初步数据进一步表明，C5 a/C5 aR 1轴调节B细胞中β 1，4半乳糖基转移酶1的表达。基于这些发现，我们假设IgG Fc聚糖模式在临床上明显的PD中从抗炎表型变为促炎表型。此外，我们认为这种变化增加了IgG AAb在皮肤中局部激活补体的效力。增加的C5 a局部生成激活先天免疫细胞上的C5 aR 1轴，诱导一连串事件，最终抑制IgG AAb的半乳糖基化和唾液酸化。在第二次FP期间，我们旨在进一步描述实验和临床PD中的IgG Fc糖基化模式，并确定PD中C5 aR 1介导的AAb糖基化调节的分子机制。在转化方面，我们的目标是评估在活动性EBA小鼠模型中预防性和治疗性C5 aR 1靶向的影响，特别强调IgG AAb的产生和N-聚糖组成。我们预计PD患者中的IgG Fc聚糖模式将作为一种新的生物标志物，用于识别有复发风险的患者并指导免疫治疗。在活性EBA模型中的预防性和治疗性C5 aR 1靶向可能为C5 aR 1抑制剂在PD中的临床使用铺平道路，其中一些即将上市。