Deciphering a novel lipid-based mechanism of innate immune modulation

破译一种新型的基于脂质的先天免疫调节机制

基本信息

批准号：
10726010
负责人：
Roarke Alexander Kamber
金额：
$ 24.23万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-05-23 至 2025-04-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10726010
关键词：
ANXA2 gene Animals Antibodies Antifungal Agents Biological Blood Circulation Bone Marrow CRISPR screen Candida albicans Cell surface Cells Clustered Regularly Interspaced Short Palindromic Repeats Coculture Techniques Data Dendritic Cells Dendritic cell activation Disease Disseminated candidiasis Dyes Exhibits Exposure to Fatty Acids Foundations Fungal Components Genes Genomic DNA Host Defense Hour Human Hydrolysis IL17 gene Immune Immune response Immunity Immunosuppression In Vitro Incubated Infection Integration Host Factors Interleukin-1 beta Interleukin-6 Invaded Kidney Knock-out Knockout Mice Libraries Lipase Lipids Macrophage Mediating Messenger RNA Microbe Modeling Molecular Morphogenesis Mucocutaneous Candidiasis Mus Mycoses Natural Immunity Nonesterified Fatty Acids Organ Palmitic Acids Pathogenesis Production Proteins Role Sepsis Signal Pathway Signal Transduction Solid Sorting Source Stains Systemic infection T-Lymphocyte TLR2 gene TLR4 gene Testing Tissues Virulence Work Yeasts cell preparation cell type cytokine experimental study genetic approach genome-wide gut microbiota high risk immune activation immunoregulation innate immune mechanisms insight interleukin-23 mouse model mutant new therapeutic target novel pathogen pathogenic bacteria pathogenic fungus pathogenic virus prevent response

项目摘要

Our understanding of antifungal immunity remains relatively limited, and examples of fungal mechanisms to modulate these responses are even rarer. C. albicans is a ubiquitous fungal component of mammalian gut microbiota as well as the most common cause of fungal infections in humans. We identified the lip2-/- virulence mutant in a screen of ~1500 C. albicans mutants in a mouse model of systemic infection (Basso et al., Cell Host and Microbe, in press). Whereas a lip2-/- strain exhibits normal virulence attributes during the first 6 hours of infection, including dissemination through the bloodstream, solid organ invasion, and yeast-to-hypha morphogenesis, its titers progressively decline at subsequent timepoints, and the host typically survives. Immune profiling of infected kidneys (the primary target organ in this infection model) revealed significant increases in levels of IL-17 mRNA and protein in organs infected with lip2-/- compared to wild-type C. albicans (WT). Strikingly, the virulence of lip2-/- was fully restored when infections were performed in Il17af-/- animals that fail to produce IL-17. These results suggested that 1) IL-17 is required for a potent antifungal response during systemic candidiasis and 2) Lip2 somehow opposes this response. We identified renal 𝛄δ T cells as a major source of IL- 17 in lip2-/--infected kidneys and renal dendritic cells as a major source of IL-23 (a cytokine known to stimulate IL-17 production by 𝛄δ T cells). Further, under in vitro conditions, we observed that lip2-/- (but not WT C. albicans) activates IL-23 expression by co-cultured bone marrow-derived dendritic cells (BMDCs). Using BMDCs prepared from Tlr2-/-, Tlr4-/-, Tlr2/Tlr4-/-, and Clec7a-/- animals, we further showed that TLR2 and/or TLR4 but not Dectin-1 are required for this response. Remarkably, immune activation was blocked when the coculture experiment is performed in the presence of 0.1 𝛍M palmitic acid, a hydrolysis product of Lip2. The data support a model in which WT C. albicans secretes Lip2 in solid organs, thereby raising local concentrations of palmitic acid, which suppresses TLR2- and TLR4-dependent activation of tissue-resident DCs and, thereby, a downstream IL-17- dependent antifungal immune response. Beyond unveiling a novel fungal virulence mechanism, this work unveils a role for IL-17 during systemic fungal infection, in addition to its previously well-documented role in defense against mucocutaneous candidiasis. To understanding this novel lipid-mediated modulation of the innate response to C. albicans, we will use a forward genetic approach to identify factors required for modulation of the innate responses to C. albicans by free fatty acids produced by its lipase activity. These exploratory, high-risk studies will provide insights lipid-mediated immunosuppression, a novel mechanism of fungal pathogenesis and immune modulation.

我们对抗真菌免疫的理解仍然相对有限，并且真菌机制的例子调节这些反应的情况更为罕见。白色念珠菌是哺乳动物肠道中普遍存在的真菌成分。我们确定了 lip2-/- 毒力。在全身感染小鼠模型中筛选出约 1500 个白色念珠菌突变体（Basso 等人，Cell Host 和微生物，正在出版），但 lip2-/- 菌株在感染的前 6 小时内表现出正常的毒力属性。感染，包括通过血流传播、实体器官侵入和酵母菌到菌丝的传播形态发生中，其滴度在随后的时间点逐渐下降，并且宿主通常能够免疫存活。对受感染肾脏（该感染模型中的主要目标器官）的分析显示，与野生型白色念珠菌 (WT) 相比，感染 lip2-/- 的器官中 IL-17 mRNA 和蛋白质的水平。引人注目的是，当对未能成功感染的 Il17af-/- 动物进行感染时，lip2-/- 的毒力完全恢复。这些结果表明 1) IL-17 是全身有效抗真菌反应所必需的。念珠菌病和 2) Lip2 以某种方式反对这种反应，我们确定肾 δ T 细胞是 IL-的主要来源。 17 在 lip2-/- 感染的肾脏和肾树突细胞中作为 IL-23（一种已知可刺激细胞因子的细胞因子）的主要来源 𝛄δ T 细胞产生 IL-17）此外，在体外条件下，我们观察到 lip2-/-（但不是 WT 白色念珠菌）。使用制备的骨髓树突状细胞 (BMDC) 共培养来激活 IL-23 表达。从 Tlr2-/-、Tlr4-/-、Tlr2/Tlr4-/- 和 Clec7a-/- 动物中，我们进一步表明 TLR2 和/或 TLR4 而不是 Dectin-1 值得注意的是，当共培养实验进行时，免疫激活被阻断。在存在 0.1 𝛍M 棕榈酸（Lip2 的水解产物）的情况下进行该数据支持模型。 WT 白色念珠菌在实体器官中分泌 Lip2，从而提高局部棕榈酸浓度，抑制组织驻留 DC 的 TLR2 和 TLR4 依赖性激活，从而抑制下游 IL-17- 除了揭示一种新的真菌毒力机制之外，这项工作还揭示了依赖的抗真菌免疫反应。除了先前已充分记录的防御作用外，IL-17 在全身真菌感染期间也发挥作用对抗皮肤粘膜念珠菌病，了解这种新型脂质介导的先天调节。针对白色念珠菌的反应，我们将使用正向遗传方法来识别调节白色念珠菌所需的因素其脂肪酶活性产生的游离脂肪酸对白色念珠菌的先天反应，这些探索性的、高风险的。研究将提供脂质介导的免疫抑制、真菌发病机制的新机制和免疫调节。