Institute of Molecular Biosciences, University of Graz, Graz, Austria.
PLoS Pathog. 2013;9(9):e1003614. doi: 10.1371/journal.ppat.1003614. Epub 2013 Sep 5.
The Gram negative bacterium Vibrio cholerae is the causative agent of the secretory diarrheal disease cholera, which has traditionally been classified as a noninflammatory disease. However, several recent reports suggest that a V. cholerae infection induces an inflammatory response in the gastrointestinal tract indicated by recruitment of innate immune cells and increase of inflammatory cytokines. In this study, we describe a colonization defect of a double extracellular nuclease V. cholerae mutant in immunocompetent mice, which is not evident in neutropenic mice. Intrigued by this observation, we investigated the impact of neutrophils, as a central part of the innate immune system, on the pathogen V. cholerae in more detail. Our results demonstrate that V. cholerae induces formation of neutrophil extracellular traps (NETs) upon contact with neutrophils, while V. cholerae in return induces the two extracellular nucleases upon presence of NETs. We show that the V. cholerae wild type rapidly degrades the DNA component of the NETs by the combined activity of the two extracellular nucleases Dns and Xds. In contrast, NETs exhibit prolonged stability in presence of the double nuclease mutant. Finally, we demonstrate that Dns and Xds mediate evasion of V. cholerae from NETs and lower the susceptibility for extracellular killing in the presence of NETs. This report provides a first comprehensive characterization of the interplay between neutrophils and V. cholerae along with new evidence that the innate immune response impacts the colonization of V. cholerae in vivo. A limitation of this study is an inability for technical and physiological reasons to visualize intact NETs in the intestinal lumen of infected mice, but we can hypothesize that extracellular nuclease production by V. cholerae may enhance survival fitness of the pathogen through NET degradation.
革兰氏阴性细菌霍乱弧菌是分泌性腹泻病霍乱的病原体，传统上被归类为非炎症性疾病。然而，最近的几项报告表明，霍乱弧菌感染会在胃肠道中引发炎症反应，表现为固有免疫细胞的募集和炎症细胞因子的增加。在这项研究中，我们描述了一种双重细胞外核酸酶霍乱弧菌突变体在免疫功能正常的小鼠中的定植缺陷，这种缺陷在中性粒细胞缺乏的小鼠中并不明显。鉴于这一观察结果，我们更详细地研究了中性粒细胞作为固有免疫系统的核心部分对病原体霍乱弧菌的影响。我们的结果表明，霍乱弧菌在与中性粒细胞接触时会诱导形成中性粒细胞胞外陷阱（NETs），而霍乱弧菌在存在 NETs 的情况下会诱导两种细胞外核酸酶。我们表明，野生型霍乱弧菌通过两种细胞外核酸酶 Dns 和 Xds 的联合活性迅速降解 NETs 的 DNA 成分。相比之下，在双核酸酶突变体存在的情况下，NETs 表现出更长的稳定性。最后，我们证明 Dns 和 Xds 介导霍乱弧菌逃避 NETs，并在存在 NETs 的情况下降低细胞外杀伤的敏感性。本报告首次全面描述了中性粒细胞和霍乱弧菌之间的相互作用，并提供了新的证据表明固有免疫反应会影响霍乱弧菌在体内的定植。本研究的一个局限性是由于技术和生理原因，无法在感染小鼠的肠道腔中可视化完整的 NETs，但我们可以假设霍乱弧菌产生细胞外核酸酶可能通过 NET 降解增强病原体的生存适应性。
