Centre for Molecular Microbiology and Infection, Department of Life Sciences, Imperial College, London, United Kingdom.
Functional Proteomics Group, Chester Beatty Laboratories, Institute of Cancer Research, London, United Kingdom.
mBio. 2021 Feb 22;13(1):e0323321. doi: 10.1128/mbio.03233-21. Epub 2022 Feb 1.
Most studies of infections at mucosal surfaces have focused on the acute phase of the disease. Consequently, little is known about the molecular processes that underpin tissue recovery and the long-term consequences postinfection. Here, we conducted temporal deep quantitative proteomic analysis of colonic intestinal epithelial cells (cIECs) from mice infected with the natural mouse pathogen Citrobacter rodentium over time points corresponding to the late steady-state phase (10 days postinfection [DPI]), the clearance phase (13 to 20 DPI), and 4 weeks after the pathogen has been cleared (48 DPI). , which relies on a type III secretion system to infect, is used to model infections with enteropathogenic and enterohemorrhagic . We observe a strong upregulation of inflammatory signaling and nutritional immunity responses during the clearance phase of the infection. Despite morphological tissue recovery, chromogranin B (ChgB)-positive endocrine cells remained significantly below baseline levels at 48 DPI. In contrast, we observed an increased abundance of proteins involved in antigen processing and presentation 4 weeks after pathogen clearance. In particular, long-term changes were characterized by a persistent interferon gamma (IFN-γ) response and the expression of major histocompatibility complex class II (MHCII) molecules in 60% of the EpCAM cIECs, which were not seen in γ mice. Nonetheless, both wild-type and γ mice mounted similar systemic and colonic IgG responses to C. rodentium and were equally protected from rechallenge, suggesting that cIEC MHCII is not necessary for protective immunity against C. rodentium. Mucosal surfaces respond to infection by mounting an array of metabolic, inflammatory, and tissue repair responses. While these have been well studied during acute infection, less is known about tissue recovery after pathogen clearance. We employ the mouse pathogen Citrobacter rodentium, which binds colonic intestinal epithelial cells (cIECs), to investigate the long-term effects of bacterial infection on gut physiology. Using global proteomic analysis, we study cIEC temporal responses during and after the clearance phase of infection. While the overall tissue morphology recovered, cIECs showed persistent signs of infection 4 weeks after pathogen clearance. These were characterized by a strong IFN-γ signature, including the upregulation of major histocompatibility complex class II (MHCII) antigen presentation proteins, suggesting that the tissue remains on "high alert" for weeks after the acute insult is resolved. However, we demonstrate that cIEC MHCII expression, which is induced by IFN-γ, is not required for protective IgG-mediated immunity against C. rodentium; instead, it may play a role in mucosal recovery.
大多数针对黏膜表面感染的研究都集中在疾病的急性期。因此，对于支持组织恢复和感染后长期后果的分子过程知之甚少。在这里，我们对感染了天然鼠病原体柠檬酸杆菌的小鼠的结肠肠上皮细胞（cIEC）进行了时间上的深度定量蛋白质组学分析，时间点对应于晚期稳定期（感染后 10 天[DPI]）、清除期（13 至 20 DPI）和病原体清除后 4 周（48 DPI）。柠檬酸杆菌通过 III 型分泌系统感染，用于模拟肠致病性和肠出血性病原体的感染。我们观察到在感染的清除阶段炎症信号和营养免疫反应强烈上调。尽管组织形态学恢复，但在 48 DPI 时，嗜铬粒蛋白 B（ChgB）阳性内分泌细胞仍明显低于基线水平。相比之下，我们观察到在清除病原体 4 周后，参与抗原加工和呈递的蛋白质的丰度增加。特别是，长期变化的特征是干扰素γ（IFN-γ）反应持续存在，60%的 EpCAM cIEC 中主要组织相容性复合体 II （MHCII）分子的表达，而在 γ 小鼠中则没有观察到。尽管如此，野生型和 γ 小鼠对柠檬酸杆菌均产生类似的系统性和结肠 IgG 反应，并同样免受再挑战的保护，这表明 cIEC MHCII 对于柠檬酸杆菌的保护性免疫不是必需的。黏膜表面通过启动一系列代谢、炎症和组织修复反应来应对感染。虽然这些在急性感染期间已经得到了很好的研究，但对于清除病原体后组织的恢复知之甚少。我们利用结合结肠肠上皮细胞（cIEC）的鼠病原体柠檬酸杆菌来研究细菌感染对肠道生理学的长期影响。通过全蛋白质组学分析，我们研究了感染清除期间和清除后 cIEC 的时间反应。虽然整体组织形态学恢复，但在清除病原体 4 周后，cIEC 仍显示出持续感染的迹象。其特征是强烈的 IFN-γ 特征，包括主要组织相容性复合体 II（MHCII）抗原呈递蛋白的上调，表明在急性损伤解决后数周内，组织仍然处于“高度警戒”状态。然而，我们证明 cIEC MHCII 表达，由 IFN-γ 诱导，对于柠檬酸杆菌的保护性 IgG 介导的免疫不是必需的；相反，它可能在黏膜恢复中发挥作用。
