Analysis of host cell binding specificity mediated by the Tp0136 adhesin of the syphilis agent Treponema pallidum subsp. pallidum
Analysis of host cell binding specificity mediated by the Tp0136 adhesin of the syphilis agent Treponema pallidum subsp. pallidum
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DOI：
10.1371/journal.pntd.0007401
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发表时间：
2019-05-01
影响因子：
3.8
通讯作者：
Parveen, Nikhat
中科院分区：
文献类型：
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作者：
Djokic, Vitomir;Giacani, Lorenzo;Parveen, Nikhat
背景梅毒每年影响全球约1100万人，是美国第三大流行的性传播细菌感染。不能独立培养和遗传操作梅毒螺旋体亚种。梅毒的致病因子，阻碍了我们对梅毒发病机制的分子机制的理解。在这里，我们使用非感染性和粘附性差的莱姆病致病螺旋体B314菌株，伯氏疏螺旋体，表达两种已知的纤连蛋白结合粘附素的变体，Tp 0136，来自T。pallidum SS 14和Nichols菌株。使用这种替代系统，我们研究了Tp 0136促进与哺乳动物细胞系的差异结合的能力，从而深入了解这种毒力因子在T.主要结果：Tp 0136在B细胞表面表达。使用不与用空载体转化的完整B314螺旋体反应的二期梅毒患者的血清通过间接免疫荧光测定法检测伯氏螺旋体。观察到Tp 0136介导的B314菌株对人上皮HEK 293细胞的粘附增加，两种Tp 0136等位基因表现出的结合水平相当。表达Tp 0136的B314对上皮HEK 293和C6胶质瘤细胞的粘附性最高。表达Tp 0136的B314菌株与纯化的纤连蛋白的结合增加，而这些螺旋体与纤连蛋白缺陷细胞系（HEp-2）的结合较差，表明Tp 0136与该宿主受体的相互作用在螺旋体附着于哺乳动物细胞中起重要作用。此外，金黄色葡萄球菌FnbA-2蛋白的纤连蛋白结合肽预孵育可显著抑制表达Tp 0136的B314细胞与Tp 0136的结合。结论Tp 0136可促进Tp 0136与不同宿主组织细胞的结合，提示Tp 0136在T.梅毒是世界上最流行的性传播疾病之一，影响着全世界数百万人。梅毒螺旋体（Treponema pallidum subsp.苍白球，可在母体感染期间由母体传播给胎儿，导致不良妊娠结局。虽然及时治疗梅毒是非常有效的，但未经治疗的感染会导致晚期梅毒，几乎影响到每个器官，并导致严重的临床表现。因此，梅毒仍然是一个严重的卫生保健问题。T.传统方法不能在实验室中培养梅毒螺旋体，这减缓了对这种病原体生物学和发病机制的了解。我们采用了一种新的方法，使用相关的细菌，伯氏疏螺旋体，表达TP 0136蛋白从两个不同的T。pallidum分离物，以研究该蛋白的功能。这种策略使我们能够证明这种蛋白质结合各种宿主细胞表面上的纤连蛋白和层粘连蛋白受体的能力。我们发现，TP 0136促进结合只有那些产生纤连蛋白的宿主细胞。此外，我们发现Tp 0136介导的结合在所有宿主细胞类型中并不等同，这表明该蛋白质可能有助于在T.苍白球
Background Syphilis affects approximately 11 million people each year globally, and is the third most prevalent sexually transmitted bacterial infection in the United States. Inability to independently culture and genetically manipulate Treponema pallidum subsp. pallidum, the causative agent of this disease, has hindered our understanding of the molecular mechanisms of syphilis pathogenesis. Here, we used the non-infectious and poorly adherent B314 strain of the Lyme disease-causing spirochete, Borrelia burgdorferi, to express two variants of a known fibronectin-binding adhesin, Tp0136, from T. pallidum SS14 and Nichols strains. Using this surrogate system, we investigated the ability of Tp0136 in facilitating differential binding to mammalian cell lines offering insight into the possible role of this virulence factor in colonization of specific tissues by T. pallidum during infection.Principal findings Expression of Tp0136 could be detected on the surface of B. burgdorferi by indirect immunofluorescence assay using sera from a secondary syphilis patient that does not react with intact B314 spirochetes transformed with the empty vector. Increase in Tp0136-mediated adherence of B314 strain to human epithelial HEK293 cells was observed with comparable levels of binding exhibited by both Tp0136 alleles. Adherence of Tp0136-expressing B314 was highest to epithelial HEK293 and C6 glioma cells. Gain in binding of B314 strain expressing Tp0136 to purified fibronectin and poor binding of these spirochetes to the fibronectin-deficient cell line (HEp-2) indicated that Tp0136 interaction with this host receptor plays an important role in spirochetal attachment to mammalian cells. Furthermore, preincubation of these cell lines with fibronectin-binding peptide from Staphylococcus aureus FnbA-2 protein significantly inhibited binding of B314 expressing Tp0136.Conclusions Our results show that Tp0136 facilitates differential level of binding to cell lines representing various host tissues, which highlights the importance of this protein in colonization of human organs by T. pallidum and resulting syphilis pathogenesis.Author summary Syphilis is one of the most prevalent sexually transmitted infections that affect millions of people around the world. The causative bacterium, Treponema pallidum subsp. pallidum, can be transmitted from mother to fetus during maternal infection, resulting in adverse pregnancy outcomes. Although timely treatment of syphilis is highly effective, untreated infection causes late syphilis that affects virtually every organ and leads to serious clinical manifestations. Therefore, syphilis remains a serious healthcare problem. T. pallidum cannot be grown in laboratory using traditional methods, which has slowed the progress in understanding this pathogen biology and pathogenesis. We employed a novel approach of using a related bacterium, Borrelia burgdorferi, to express Tp0136 protein from two different T. pallidum isolates to study the function of this protein. This strategy enabled us to demonstrate the ability of this protein to bind to fibronectin and laminin receptors present on the surface of various host cells. We showed that Tp0136 facilitates binding to only those host cells that produce fibronectin. In addition, we found that Tp0136-mediated binding is not equivalent in all host cell types, suggesting that the protein could help in colonization of specific human organs and tissues during infection by T. pallidum.