<b>TolC facilitates the Intracellular Survival and Immunomodulation of </b><b><i>Salmonella</i></b><b> Typhi in Human Host Cells</b>

<b>Introduction:</b> <i>Salmonella enterica</i> serovar Typhi (<i>S</i>. Typhi) causes typhoid fever, a systemic infection that affects millions of people worldwide. <i>S</i>. Typhi can invade and survive within host cells, such as intestinal epithelial cells and macrophages, by modulating their immune responses. However, the immunomodulatory capability of <i>S</i>. Typhi in relation to TolC-facilitated efflux pump function remains unclear. <b>Methods: </b>The role of TolC, an outer membrane protein that facilitates efflux pump function, in the invasion and immunomodulation of <i>S</i>. Typhi, was studied in human intestinal epithelial cells and macrophages. The <i>tolC</i> deletion mutant of <i>S</i>. Typhi was compared with the wild-type and its complemented strain in terms of their ability to invade epithelial cells, survive and induce cytotoxicity in macrophages, and elicit proinflammatory cytokine production in macrophages. <b>Results:</b> The <i>tolC</i> mutant, which has a defective outer membrane, was impaired in invading epithelial cells compared to the wild-type strain, but the intracellular presence of the <i>tolC</i> mutant exhibited greater cytotoxicity and induced higher levels of proinflammatory cytokines (<i>IL-1β</i> and <i>IL-8</i>) in macrophages compared to the wild-type strain. These effects were reversed by complementing the <i>tolC</i> mutant with a functional <i>tolC</i> gene. <b>Discussion:</b> Our results suggest that TolC plays a role in <i>S</i>. Typhi to efficiently invade epithelial cells and suppress host immune responses during infection. TolC may be a potential target for the development of novel therapeutics against typhoid fever.<b>引言：</b><i>伤寒沙门菌（Salmonella enterica serovar Typhi，简称S. Typhi）可引发伤寒——一种在全球范围内累及数百万人的全身性感染疾病。该菌可通过调控宿主免疫应答，侵入并寄生于肠上皮细胞、巨噬细胞等宿主细胞内。然而，伤寒沙门菌的免疫调控能力与TolC介导的外排泵功能之间的关联机制仍有待阐明。</i> <b>方法：</b>本研究以人肠上皮细胞与巨噬细胞为实验模型，探究介导外排泵功能的外膜蛋白TolC在伤寒沙门菌侵袭与免疫调控过程中的作用。我们将伤寒沙门菌的<i>tolC</i>基因缺失突变株、野生株及其互补株进行比对，分别检测三者侵袭上皮细胞的能力、在巨噬细胞内的存活情况与诱导细胞毒性的能力，以及在巨噬细胞中促炎细胞因子的产生水平。 <b>结果：</b>尽管<i>tolC</i>突变株的外膜存在缺陷，其侵袭上皮细胞的能力相较于野生株有所减弱，但该<i>tolC</i>突变株在巨噬细胞内寄生时，所诱导的细胞毒性更强，且促炎细胞因子（<i>IL-1β</i>、<i>IL-8</i>）的表达水平显著高于野生株。通过向<i>tolC</i>突变株导入功能性<i>tolC</i>基因进行互补，上述表型均得到恢复。 <b>讨论：</b>本研究结果表明，TolC在伤寒沙门菌高效侵袭上皮细胞以及感染过程中抑制宿主免疫应答的过程中发挥关键作用。TolC或可成为研发新型抗伤寒治疗药物的潜在靶点。