Control of immediate hypersensitivity responses in parasitic and other diseases

已经对可能与空气过敏原发生交叉反应的寄生虫过敏原进行了详尽的搜索。 我们已经确定了一些寄生虫抗原和过敏原直系同源物，并研究了IgE和IgG对这些抗原的反应。 我们已经明确表明，寄生虫感染诱导寄生虫特异性IgE和IgE与环境过敏原的寄生虫抗原密切相关的相互作用。 具体而言，我们调查了一个主要的谷胱甘肽-S转移酶过敏原的蟑螂（Bla g 5）和谷胱甘肽-S转移酶的班氏吴策线虫（WbGST），一个主要的淋巴丝虫病原体的人类之间的交叉反应。我们通过计算机分析和线性表位作图比较了Bla g 5和WbGST之间的分子和结构相似性。检测丝虫感染和未感染丝虫患者的IgE、IgG和IgG（4）抗体水平。小鼠感染Heligmosomoides bakeri，并测试其皮肤的交叉反应性过敏反应。我们能够表明，这2种蛋白质在氨基酸水平上具有30%的相同性，在N-末端区域具有显着的相似性，并且基于预测的三维模型具有整体结构保守性。丝虫感染与IgE、IgG和IgG（4）抗Bla g 5抗体的产生有关，Bla g 5抗体（不论同种型）与WbGST抗体之间存在显著相关性。 将蟑螂过敏受试者的血清与WbGST部分耗尽（50%-70%）的抗Bla g 5 IgE、IgG和IgG（4）抗体预孵育。Bla g 5的IgE表位作图显示，在WbGST中有2个线性N端表位高度保守，对应于部分参与抑制WbGST结合的Bla g 5肽段。最后，小鼠感染H bakeri开发抗-HbGST IgE，并表现出直接型皮肤试验反应Bla g 5。 接下来，我们使用了详尽的生物信息学方法来了解寄生虫蛋白质和过敏性之间的界面。因为目前的范式表明，过敏蛋白与微生物的结构同源性，（特别是蠕虫）或人类蛋白质的过敏性的基础上，我们系统地研究了过敏原和病原体蛋白质之间的结构关系（蠕虫、原生动物、真菌和细菌），因为它们与变应原性有关，我们比较了499种分子定义的过敏原的氨基酸序列与15种已知病原体的预测蛋白质组，包括Th 2诱导蠕虫和Th 1诱导原生动物，和人类使用各种生物信息学工具。过敏性评估的基础上IgE流行使用公开访问的数据库和文献。我们在蠕虫、原生动物、真菌和人类的蛋白质中发现了常见过敏原的多种同源物，但在细菌中没有发现。相比之下，187过敏原没有表现出与任何研究的微生物属的同源性。有趣的是，没有同源物的过敏原或具有有限水平的序列保守性的过敏原是最过敏的，在过敏人群中显示高IgE患病率。无论是寄生虫，包括蠕虫，或人类蛋白质的变应原性和氨基酸保守水平之间呈反比关系。我们的研究结果表明，变应原性可能与抗原的相对“独特性”，即免疫原性，而相似性将导致免疫耐受。

An exhaustive search for parasite allergens that may cross-react with aeroallergens has been performed. We have identified a number of parasite antigens and the allergens orthologues and have studied the IgE and IgG responses to these. We have demonstrated unequivocally that parasite infections induced both parasite-specific IgE and IgE that interacts with environmental allergens to which the parasite antigens are closely related. Specifically,we investigates the cross-reactivity between a major glutathione-S transferase allergen of cockroach (Bla g 5) and the glutathione-S transferase of Wuchereria bancrofti (WbGST), a major lymphatic filarial pathogen of humans. We compared the molecular and structural similarities between Bla g 5 and WbGST by in silico analysis and by linear epitope mapping. The levels of IgE, IgG, and IgG(4) antibodies were measured in filarial-infected and filarial-uninfected patients. Mice were infected with Heligmosomoides bakeri, and their skin was tested for cross-reactive allergic responses. We were able to show that these 2 proteins are 30% identical at the amino acid level with remarkable similarity in the N-terminal region and overall structural conservation based on predicted 3-dimensional models. Filarial infection was associated with IgE, IgG, and IgG(4) anti-Bla g 5 antibody production, with a significant correlation between antibodies (irrespective of isotype) to Bla g 5 and WbGST. Preincubation of sera from cockroach-allergic subjects with WbGST partially depleted (by 50%-70%) anti-Bla g 5 IgE, IgG, and IgG(4) antibodies. IgE epitope mapping of Bla g 5 revealed that 2 linear N-terminal epitopes are highly conserved in WbGST corresponding to Bla g 5 peptides partially involved in the inhibition of WbGST binding. Finally, mice infected with H bakeri developed anti-HbGST IgE and showed immediate-type skin test reactivity to Bla g 5. We next used an exhaustive bioinformatics approach to understand the interface between parasite proteins and allergenicty. Because the current paradigm suggests that structural homology of allergenic proteins to microbial (particularly helminths) or human proteins underlie their allergenic nature, we examined systematically the structural relationships among allergens and proteins of pathogens (helminths, protozoans, fungi and bacteria) as they relate to allergenicity, we compared the amino acid sequence of 499 molecularly-defined allergens with the predicted proteomes of fifteen known pathogens, including Th2 inducing helminths and Th1-inducing protozoans, and humans using a variety of bioinformatic tools. Allergenicity was assessed based on IgE prevalences using publicly accessible databases and the literature. We found multiple homologues of common allergens among proteins of helminths, protozoans, fungi and humans, but not of bacteria. In contrast, 187 allergens showed no homology with any of the microbial genera studied. Interestingly, allergens without homologues or those with limited levels of sequence conservation were the most allergenic displaying high IgE prevalences in the allergic population. There was an inverse relationship between allergenicity and amino acid conservation levels with either parasite, including helminth, or human proteins. Our results suggest that allergenicity may be associated with the relative "uniqueness" of an antigen, i.e. immunogenicity, while similarity would lead to immunological tolerance.