Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, United States of America.
Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M University, Bryan, TX, United States of America.
PLoS One. 2018 Sep 11;13(9):e0203698. doi: 10.1371/journal.pone.0203698. eCollection 2018.
Neutrophils are innate immune response cells designed to kill invading microorganisms. One of the mechanisms neutrophils use to kill bacteria is generation of damaging reactive oxygen species (ROS) via the respiratory burst. However, during enteric salmonellosis, neutrophil-derived ROS actually facilitates Salmonella expansion and survival in the gut. This seeming paradox led us to hypothesize that Salmonella may possess mechanisms to influence the neutrophil respiratory burst. In this work, we used an in vitro Salmonella-neutrophil co-culture model to examine the impact of enteric infection relevant virulence factors on the respiratory burst of human neutrophils. We report that neutrophils primed with granulocyte-macrophage colony stimulating factor and suspended in serum containing complement produce a robust respiratory burst when stimulated with viable STm. The magnitude of the respiratory burst increases when STm are grown under conditions to induce the expression of the type-3 secretion system-1. STm mutants lacking the type-3 secretion system-1 induce less neutrophil ROS than the virulent WT. In addition, we demonstrate that flagellar motility is a significant agonist of the neutrophil respiratory burst. Together our data demonstrate that both the type-3 secretion system-1 and flagellar motility, which are established virulence factors in enteric salmonellosis, also appear to directly influence the magnitude of the neutrophil respiratory burst in response to STm in vitro.
中性粒细胞是先天免疫反应细胞，旨在杀死入侵的微生物。中性粒细胞杀死细菌的一种机制是通过呼吸爆发产生有害的活性氧（ROS）。然而，在肠道沙门氏菌病中，中性粒细胞衍生的 ROS 实际上促进了沙门氏菌在肠道中的扩张和存活。这一似乎矛盾的现象促使我们假设沙门氏菌可能具有影响中性粒细胞呼吸爆发的机制。在这项工作中，我们使用体外沙门氏菌-中性粒细胞共培养模型来研究与肠道感染相关的毒力因子对人中性粒细胞呼吸爆发的影响。我们报告说，用粒细胞-巨噬细胞集落刺激因子预处理并悬浮在含有补体的血清中的中性粒细胞在受到活 STm 刺激时会产生强烈的呼吸爆发。当 STm 在诱导 I 型 III 型分泌系统表达的条件下生长时，呼吸爆发的幅度会增加。缺乏 III 型分泌系统 I 的 STm 突变体诱导的中性粒细胞 ROS 比毒力 WT 少。此外，我们证明鞭毛运动是中性粒细胞呼吸爆发的一个重要激动剂。我们的数据表明，III 型分泌系统 I 和鞭毛运动，这是肠道沙门氏菌病中的既定毒力因素，也似乎直接影响 STm 在体外对中性粒细胞呼吸爆发的幅度。
