Table_3_Unraveling cross-reactivity of anti-glycan IgG responses in filarial nematode infections.xlsx

Parasitic nematodes responsible for filarial diseases cause chronic disablement in humans worldwide. Elimination programs have substantially reduced the rate of infection in certain areas, but limitations of current diagnostics for population surveillance have been pointed out and improved assays are needed to reach the elimination targets. While serological tests detecting antibodies to parasite antigens are convenient tools, those currently available are compromised by the occurrence of antibodies cross-reactive between nematodes, as well as by the presence of residual antibodies in sera years after treatment and clearance of the infection. We recently characterized the N-linked and glycosphingolipid derived glycans of the parasitic nematode Brugia malayi and revealed the presence of various antigenic structures that triggered immunoglobulin G (IgG) responses in infected individuals. To address the specificity of IgG binding to these glycan antigens, we screened microarrays containing Brugia malayi glycans with plasma from uninfected individuals and from individuals infected with Loa loa, Onchocerca volvulus, Mansonella perstans and Wuchereria bancrofti, four closely related filarial nematodes. IgG to a restricted subset of cross-reactive glycans was observed in infection plasmas from all four species. In plasma from Onchocerca volvulus and Mansonella perstans infected individuals, IgG binding to many more glycans was additionally detected, resulting in total IgG responses similar to the ones of Brugia malayi infected individuals. For these infection groups, Brugia malayi, Onchocerca volvulus and Mansonella perstans, we further studied the different IgG subclasses to Brugia malayi glycans. In all three infections, IgG1 and IgG2 appeared to be the major subclasses involved in response to glycan antigens. Interestingly, in Brugia malayi infected individuals, we observed a marked reduction in particular in IgG2 to parasite glycans post-treatment with anthelminthic, suggesting a promising potential for diagnostic applications. Thus, we compared the IgG response to a broad repertoire of Brugia malayi glycans in individuals infected with various filarial nematodes. We identified broadly cross-reactive and more specific glycan targets, extending the currently scarce knowledge of filarial nematode glycosylation and host anti-glycan antibody response. We believe that our initial findings could be further exploited to develop disease-specific diagnostics as part of an integrated approach for filarial disease control.

引发丝虫病的寄生线虫（Parasitic nematodes）会在全球范围内造成人类慢性失能。消除项目已在部分地区大幅降低了感染率，但当前用于人群监测的诊断方法存在局限，亟需优化检测手段以达成消除目标。虽检测寄生虫抗原抗体的血清学检测方法是便捷的检测工具，但现有手段存在缺陷：一方面会出现线虫间交叉反应性抗体，另一方面感染经治疗清除后，数年内血清中仍会残留抗体。我们近期对寄生线虫马来布鲁线虫（Brugia malayi）的N-连接糖蛋白及糖鞘脂衍生聚糖进行了表征，并揭示了多种可在感染者体内触发免疫球蛋白G（IgG）应答的抗原结构。为探究IgG与这些聚糖抗原的结合特异性，我们使用来自未感染者，以及感染罗阿丝虫（Loa loa）、盘尾丝虫（Onchocerca volvulus）、常现曼森线虫（Mansonella perstans）和班氏吴策线虫（Wuchereria bancrofti）这四种亲缘关系相近的丝虫线虫个体的血浆，对包含马来布鲁线虫聚糖的微阵列进行了筛选。在四种线虫感染的血浆样本中，均检测到针对有限子集的交叉反应性聚糖的IgG结合信号。在感染盘尾丝虫与常现曼森线虫的个体血浆中，还检测到更多聚糖的IgG结合，总IgG应答水平与马来布鲁线虫感染者相近。针对马来布鲁线虫、盘尾丝虫与常现曼森线虫这三类感染群体，我们进一步研究了其针对马来布鲁线虫聚糖的不同IgG亚类应答情况。在三类感染中，IgG1与IgG2似乎是介导聚糖抗原免疫应答的主要亚类。有趣的是，在马来布鲁线虫感染者中，我们观察到接受抗蠕虫治疗后，其针对寄生虫聚糖的IgG（尤其是IgG2）水平显著降低，这提示其在诊断应用中具有良好的潜在价值。因此，我们比较了感染多种丝虫线虫的个体对马来布鲁线虫聚糖广谱库的IgG应答情况。我们鉴定出了广泛交叉反应性及特异性更强的聚糖靶点，拓展了当前对丝虫线虫糖基化及宿主抗聚糖抗体应答的有限认知。我们认为，本研究的初步发现可进一步用于开发疾病特异性诊断方法，作为丝虫病防控综合策略的组成部分。