Immunomodulatory Effects of Pneumococcal Extracellular Vesicles on Cellular and Humoral Host Defenses.
Immunomodulatory Effects of Pneumococcal Extracellular Vesicles on Cellular and Humoral Host Defenses.
复制标题
DOI：
10.1128/mbio.00559-18
复制
发表时间：
2018-04-10
期刊：
影响因子：
6.4
通讯作者：
Henriques-Normark B
中科院分区：
文献类型：
--
作者：
Codemo M;Muschiol S;Iovino F;Nannapaneni P;Plant L;Wai SN;Henriques-Normark B
革兰氏阳性菌，包括主要的呼吸道病原体肺炎链球菌，最近被证明产生细胞外小泡(EVS)，这些小泡可能起源于质膜并释放到细胞外环境中。EV可以作为许多细菌蛋白质的载体，然而，它们参与细胞过程以及它们与先天性免疫系统的相互作用却知之甚少。在这里，肺炎球菌EV的特征和它们的免疫调节作用进行了研究。肺炎球菌EV从细菌表面突出并释放到介质中，形成25-250 nm的脂染囊泡，其中包含大量的胞浆、膜和表面相关蛋白。与细菌总裂解物相比，EVS中的胞质致孔毒素肺炎溶血素显著丰富，但不是EV形成所必需的。肺炎球菌EV内化到A549肺上皮细胞和人单核细胞来源的树突状细胞中，并诱导促炎细胞因子反应，而与肺炎溶血素含量无关。来自被包裹的肺炎球菌的EV被血清蛋白识别，导致C3b沉积和C5b-9膜攻击复合体的形成以及因子H的募集，这取决于胆碱结合蛋白PSPC的存在。在人血清中加入EVS可减少对被包裹的肺炎球菌的吞噬细胞杀伤力。我们的数据表明，EVS可能通过允许囊泡相关蛋白和其他大分子进入宿主细胞而发挥免疫调节作用。此外，EV暴露了血清中补体因子的靶标，促进了肺炎球菌对体液宿主防御的逃避。肺炎链球菌是全世界发病率和死亡率的主要贡献者，是中耳炎和鼻窦炎等轻度呼吸道感染和社区获得性肺炎、合并或不合并败血症和脑膜炎等严重感染的主要原因。需要更多关于肺炎球菌如何与宿主相互作用、传递毒力因子和激活免疫防御的知识。在这里，我们显示肺炎球菌形成细胞外小泡，这些小泡从质膜发出，并包含毒力特性，包括浓缩肺炎溶血素。我们发现肺炎球菌的囊泡可以内化到上皮细胞和树突状细胞中，并与补体蛋白结合，从而促进肺炎链球菌逃避补体介导的吞噬作用。它们还能诱导不依赖肺炎溶血素的促炎反应。我们认为，这些小泡可以作为一种机制，将肺炎球菌蛋白和其他免疫调节成分运送到宿主细胞中，并帮助肺炎球菌避免补体沉积和吞噬介导的杀伤，从而可能导致肺炎球菌感染的症状。
Gram-positive bacteria, including the major respiratory pathogen Streptococcus pneumoniae, were recently shown to produce extracellular vesicles (EVs) that likely originate from the plasma membrane and are released into the extracellular environment. EVs may function as cargo for many bacterial proteins, however, their involvement in cellular processes and their interactions with the innate immune system are poorly understood. Here, EVs from pneumococci were characterized and their immunomodulatory effects investigated. Pneumococcal EVs were protruding from the bacterial surface and released into the medium as 25 to 250 nm lipid stained vesicles containing a large number of cytosolic, membrane, and surface-associated proteins. The cytosolic pore-forming toxin pneumolysin was significantly enriched in EVs compared to a total bacterial lysate but was not required for EV formation. Pneumococcal EVs were internalized into A549 lung epithelial cells and human monocyte-derived dendritic cells and induced proinflammatory cytokine responses irrespective of pneumolysin content. EVs from encapsulated pneumococci were recognized by serum proteins, resulting in C3b deposition and formation of C5b-9 membrane attack complexes as well as factor H recruitment, depending on the presence of the choline binding protein PspC. Addition of EVs to human serum decreased opsonophagocytic killing of encapsulated pneumococci. Our data suggest that EVs may act in an immunomodulatory manner by allowing delivery of vesicle-associated proteins and other macromolecules into host cells. In addition, EVs expose targets for complement factors in serum, promoting pneumococcal evasion of humoral host defense. Streptococcus pneumoniae is a major contributor to morbidity and mortality worldwide, being the major cause of milder respiratory tract infections such as otitis and sinusitis and of severe infections such as community-acquired pneumonia, with or without septicemia, and meningitis. More knowledge is needed on how pneumococci interact with the host, deliver virulence factors, and activate immune defenses. Here we show that pneumococci form extracellular vesicles that emanate from the plasma membrane and contain virulence properties, including enrichment of pneumolysin. We found that pneumococcal vesicles can be internalized into epithelial and dendritic cells and bind complement proteins, thereby promoting pneumococcal evasion of complement-mediated opsonophagocytosis. They also induce pneumolysin-independent proinflammatory responses. We suggest that these vesicles can function as a mechanism for delivery of pneumococcal proteins and other immunomodulatory components into host cells and help pneumococci to avoid complement deposition and phagocytosis-mediated killing, thereby possibly contributing to the symptoms found in pneumococcal infections.