Determination of molecular mechanisms supporting the anti-inflammatory properties of IgG4 antibodies in filarial infected individuals

本项目旨在分析支持丝虫感染中IgG 4抗体的免疫抑制特性的结构和分子基础。我们小组通过基础研究和免疫流行病学研究广泛描述了这种特殊抗体同种型在丝虫感染中的重要性。扩展我们早期的结果，丝虫诱导的IgG 4是必不可少的维持调节免疫应答，我们目前的初步数据表明，IgG 4可以抑制/调节粒细胞活性。这种功能途径适用于没有或几乎没有疾病症状/病理的个体，但我们不能从表现出病理的淋巴丝虫病个体（如水肿患者）中观察到IgG 4的这种能力。这使我们研究了赋予IgG 4抗体免疫抑制特性的生化模式及其对丝虫感染的生理病理学的影响。我们将研究来自地方病正常人、感染但免疫反应低下的无症状个体和有症状患者的IgG 4分子之间的结构和功能差异。将通过结合酶促去糖基化和差示质谱肽图谱分析不同临床组中IgG亚类的糖基化特征。然后，将使用我们完善的体外共培养粒细胞抑制系统和功能性抗体依赖性细胞介导的细胞毒性（ADCC）试验研究表征的抑制性IgG 4糖型的抑制活性的机制。我们将特别关注哪些FcR和下游信号通路参与IgG 4介导的粒细胞亚群抑制。此外，由于遗传变异性可能会调节粒细胞对IgG 4抗体的反应，我们将使用整合基因组和转录组信息的表达数量性状位点（eQTL）方法进一步研究此类共培养物如何影响基因表达。最后，我们将研究所观察到的糖基化模式和IgG 4抗体的抑制特性是否对淋巴丝虫病具有特异性，或者也与另一种主要丝虫病的生理病理学相关：盘尾丝虫病。该项目的结果将对我们理解抗体同种型在丝虫病病理生理学中的作用产生深远影响，并对一般传染病的预防和治疗产生直接影响。

The present project aims at analysing the structural and molecular basis supporting the immunosuppressive properties attributed to IgG4 antibodies in filarial infections. Our group has extensively described the importance of this particular antibody isotype in filarial infections through both basic research and immunoepidemiological studies. Expanding on our earlier results that filarial-induced IgG4 is essential for maintaining a regulated immune response, our current preliminary data shows that IgG4 can inhibit/modulate granulocyte activity. This functional pathway applies to individuals that show no or little disease symptoms/pathology, but we could not observe this ability of IgG4 from lymphatic filariasis individuals presenting pathology, such as patients with lymphedema. This led us to investigate the biochemical patterns conferring immune suppressive properties to IgG4 antibodies and their impact on the physiopathology of filarial infections. We will investigate the structural and functional differences between IgG4 molecules from endemic normals, infected but immunologically hyporesponsive individuals without symptoms and symptomatic patients. The glycosylation profile of IgG subclasses in the different clinical groups will be analysed by combining enzymatic deglycosylation and differential mass spectrometric peptide mapping. The mechanisms underlying the suppressive activities of the characterized inhibitory IgG4 glycoforms will be then investigated using our well-established in vitro co-culture granulocyte suppression system and functional antibody-dependent cell mediated cytotoxicity (ADCC) assays. We will particularly focus on which FcR and downstream signalling pathways are involved in the IgG4-mediated suppression of granulocyte subsets. Moreover, since genetic variability may modulate granulocyte responses to IgG4 antibodies we will additionally investigate how such co-cultures impact gene expression using an expression quantitative trait locus (eQTL) approach which integrates genomic and transcriptomic information. Finally, we will investigate whether the observed glycosylation patterns and suppressive properties of IgG4 antibodies are specific for lymphatic filariasis, or also correlate with the physiopathology of another major filarial disease: onchocerciasis. The results from the project will have a profound impact on our understanding of the role of antibody isotypes in the physiopathology of filarial diseases and should have direct implications for the prevention and the treatment of infectious diseases in general.