Fine Mapping of the Interaction between C4b-Binding Protein and Outer Membrane Proteins LigA and LigB of Pathogenic Leptospira interrogans.
Fine Mapping of the Interaction between C4b-Binding Protein and Outer Membrane Proteins LigA and LigB of Pathogenic Leptospira interrogans.
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DOI：
10.1371/journal.pntd.0004192
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发表时间：
2015
影响因子：
3.8
通讯作者：
Isaac L
中科院分区：
文献类型：
--
作者：
Breda LC;Hsieh CL;Castiblanco Valencia MM;da Silva LB;Barbosa AS;Blom AM;Chang YF;Isaac L
补体系统由 40 多种蛋白质组成，参与炎症反应和病原体杀灭。补体抑制剂对于避免宿主细胞上该系统的过度消耗和激活是必要的。钩端螺旋体病是一种由钩端螺旋体属螺旋体引起的世界性人畜共患病。致病性钩端螺旋体能够通过与宿主补体抑制剂 H 因子 [FH] 和 C4b 结合蛋白 (C4BP) 结合而逃避补体激活，而非致病性钩端螺旋体在新鲜血清存在下会被迅速杀死。在这项研究中，我们证明了 C4BP α 链的补体控制蛋白结构域 (CCP) 7 和 8 与致病性钩端螺旋体问号钩端螺旋体的外膜蛋白 LcpA、LigA 和 LigB 相互作用。 C4BP与LcpA、LigA和LigB之间的相互作用对离子强度敏感并被肝素抑制。我们精细绘制了参与其与 C4BP 和肝素结合的 LigA 和 LigB 结构域，发现这两种相互作用都是通过 LigA 和 LigB 的细菌免疫球蛋白样（大）结构域 7 和 8（LigA7-8 和 LigB7-8）以及 LigB9-10 介导的。因此，C4BP 和肝素在 Lig 蛋白上可能具有相同的结合位点。钩端螺旋体病是一种具有公共卫生意义的被忽视的传染病。它是世界上最重要的人畜共患病之一，每年影响至少 50 万人，其中约 10-20% 的病例是致命的。大多数病例发生在缺乏适当卫生设施的热带发展中国家。补体系统在控制这种感染方面发挥着重要作用，致病性钩端螺旋体开发了多种策略来逃避该系统，例如，结合补体调节蛋白，如 C4b 结合蛋白 (C4BP)。在这项工作中，我们精细地映射了对于这种规避很重要的 C4BP 域。我们还绘制了 C4BP 与 LigA 和 LigB 的相互作用，这两种表面蛋白存在于所有致病性钩端螺旋体中。现有的钩端螺旋体病疫苗基于地区特异性血清型，保护性不强。因此，有必要寻找更好的疫苗，而 Lig A 和 Lig B 代表了有希望为全世界人民提供免疫的候选疫苗。我们相信，深入了解 C4BP 与 LigA 和 LigB 之间的相互作用可以为免疫治疗和开发在感染第一天使用的新药物开辟新的前景，此时特异性抗体的产生仍然较低，而补体系统在控制这种感染方面发挥着重要作用。
The complement system consists of more than 40 proteins that participate in the inflammatory response and in pathogen killing. Complement inhibitors are necessary to avoid the excessive consumption and activation of this system on host cells. Leptospirosis is a worldwide zoonosis caused by spirochetes from the genus Leptospira. Pathogenic leptospires are able to escape from complement activation by binding to host complement inhibitors Factor H [FH] and C4b-binding protein (C4BP) while non-pathogenic leptospires are rapidly killed in the presence of fresh serum. In this study, we demonstrate that complement control protein domains (CCP) 7 and 8 of C4BP α-chain interact with the outer membrane proteins LcpA, LigA and LigB from the pathogenic leptospire L. interrogans. The interaction between C4BP and LcpA, LigA and LigB is sensitive to ionic strength and inhibited by heparin. We fine mapped the LigA and LigB domains involved in its binding to C4BP and heparin and found that both interactions are mediated through the bacterial immunoglobulin-like (Big) domains 7 and 8 (LigA7-8 and LigB7-8) of both LigA and LigB and also through LigB9-10. Therefore, C4BP and heparin may share the same binding sites on Lig proteins. Leptospirosis is a neglected infectious disease of public health significance. It is one of the most important zoonosis worldwide, affecting at least 500,000 people each year of which approximately 10–20% of cases are fatal. Most of the cases occur in tropical developing countries which lack proper sanitation facilities. The complement system plays an important role to control this infection and pathogenic leptospires developed several strategies to escape from this system, for example, binding to complement regulatory proteins such as C4b binding protein (C4BP). In this work, we fine mapped the C4BP domains important for this evasion. We also mapped C4BP interactions with LigA and LigB, two surface proteins present in all pathogenic leptospires. The available leptospirosis vaccines are based on region-specific serovars and are not very protective. Consequently, the search of better vaccines is necessary and Lig A and Lig B represent promising vaccine candidates to immunize people worldwide. We believe that deeply understanding the interactions between C4BP with LigA and LigB could open new perspectives for immunotherapy and development of new drugs to be used during the first days of infection, when the production of specific antibodies is still low and the complement system plays an important role to control this infection.