Regulation of Innate Immune System Sensing of C. albicans Infection

天然免疫系统对白色念珠菌感染感知的调节

• 批准号: 9262609
• 负责人: JIAN ZHANG
• 金额: $ 1.32万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9262609
• 关键词: Adverse effects; Antifungal Agents; Binding; Bone Marrow; C Type Lectin Receptors; CBLB gene; Candida; Candida albicans; Candidiasis; Cell Wall; Cell surface; Cells; Clinical; Data; Development; Diagnostic; Disseminated candidiasis; Dose; Drug resistance; Enzymes; Family; Family member; Homeostasis; Hospitals; Host Defense; Host Defense Mechanism; Hyphae; Immune; Immune system; Immunity; Immunocompetent; Immunocompromised Host; Impairment; In Vitro; Infection; Infectious Skin Diseases; Inflammatory; Inflammatory Response; Innate Immune Response; Innate Immune System; Lead; Life; LoxP-flanked allele; Lymphoma; Lysine; Mannans; Mediating; Molecular; Morbidity - disease rate; Mucous Membrane; Mus; Mutation; Mycoses; Patients; Pattern recognition receptor; Pharmaceutical Preparations; Phenotype; Play; Polyubiquitination; Preventive; Proteins; Recruitment Activity; Recycling; Regulation; Role; Sepsis; Signal Transduction; Site; Small Interfering RNA; Surface; T-Cell Activation; TLR2 gene; Testing; Therapeutic; Tyrosine Phosphorylation; Ubiquitination; Vagina; Wild Type Mouse; Yeasts; base; beta-Glucans; candidate identification; candidemia; cell type; combat; cytokine; dectin 1; fungus; immune resistance; in vivo; insight; macrophage; member; mortality; mouse dectin-2; oral infection; pathogen; protein B; public health relevance; response; therapeutic target; tool; ubiquitin ligase; ubiquitin-protein ligase

 DESCRIPTION (provided by applicant): Disseminated C. albicans infection in patients who have a weakened immune system is life-threatening. In hospitals 40% of bloodstream infections (candidemia) are caused by Candida spp. Despite the availability of several anti-fungal drugs, invasive candidiasis still has a high mortality rate ranging from 45 to 75%. The high morbidity and mortality associated with disseminated candidiasis are mainly due to the lack of early and accurate diagnostic tools, the limited anti-fungal drugs, and the emergence of drug resistance, thus highlighting the need to further understand host-pathogen interactions and the mechanisms of immune resistance to fungal spread, and to develop alternative immune-based strategies to combat candidemia. In normal hosts, C. albicans is controlled after activation of innate immune cells via cell surface pattern recognition receptors (PRRs) such as TLR2 and C-type lectin receptors (CLRs) that detect the infecting fungi. The CLRs Dectin-1 and Dectin-2/3 recognize C. albicans yeast cells and hyphae by binding to the surface β-glucans and α- mannans of the two fungal forms, respectively. Recognition of these molecules results in release of inflammatory cytokines from innate immune cells, which is critical for anti-fungal immunity. The mechanisms that control this CLR-mediated innate immune response to fungal infection are completely unknown. Our preliminary results showed that bone marrow-derived macrophages (BMDMs) from Cblb-/- mice infected with C. albicans yeast and hyphae produce more inflammatory cytokines than do BMDMs from wild type (WT) mice. This response involves signaling via Dectin-1, -2, and/or -3 but not via the TLRs. This finding suggests that Cbl-b acts through the Dectin CLRs but not the TLRs in macrophages. Consistent with this notion, BMDMs from Cblb-/- mice have impaired Dectin-1, -2, and -3 degradation upon interaction with C. albicans yeast and hyphae. In support of this finding, Dectin-1 undergoes poly-ubiquitination in macrophages upon infection with C. albicans yeasts, whereas this ubiquitination is abrogated in BMDMs lacking Cbl-b. Furthermore, Cblb-/- mice are protected from infection with a lethal dose of C. albicans. Based on these results, we hypothesize that during C. albicans infection, Cbl-b is recruited to Dectin CLRs, and this targets Dectins for ubiquitination which dampens CLR-mediated innate immune responses against fungi. To test this hypothesis, we propose to determine (1) whether and how Cbl-b regulates Dectin down-modulation via protein ubiquitination in vitro; and (2) whether Cbl-b dampens host effective responses against C. albicans mediated by the Dectin family of CLRs. Successful completion of this project will reveal a previously unknown host defense mechanism and provide molecular insight into the host defense machinery and ultimately facilitate the identification of candidate targets for appropriate modulation of anti-fungal responses and therapeutic options.

 描述（由申请人提供）：尽管有多种抗真菌药物，但在医院中，40% 的血液感染（念珠菌血症）是由念珠菌引起的。 ，侵袭性念珠菌病仍然具有45%至75%的高死亡率，与播散性念珠菌病相关的高发病率和死亡率主要是由于。缺乏早期准确的诊断工具、有限的抗真菌药物以及耐药性的出现，因此强调需要进一步了解宿主与病原体的相互作用以及对真菌传播的免疫抵抗机制，并开发替代性免疫疗法。在正常宿主中，通过检测感染的 TLR2 和 C 型凝集素受体 (CLR) 等细胞表面模式识别受体 (PRR) 激活先天免疫细胞后，白色念珠菌得到控制。 CLR Dectin-1 和 Dectin-2/3 通过分别与两种真菌形式的表面 β-葡聚糖和 α-甘露聚糖结合来识别白色念珠菌酵母细胞和菌丝，识别这些分子会导致炎症的释放。来自先天免疫细胞的细胞因子对于抗真菌免疫至关重要。我们的初步结果表明，控制这种 CLR 介导的针对真菌感染的先天免疫反应的机制完全未知。感染白色念珠菌酵母和菌丝的 Cblb-/- 小鼠的巨噬细胞 (BMDM) 比野生型 (WT) 小鼠的 BMDM 产生更多的炎症细胞因子。这种反应涉及通过 Dectin-1、-2 和/或 -3 进行信号传导。但不是通过 TLR Cblb-/- 小鼠在与白色念珠菌酵母和菌丝相互作用后，Dectin-1、-2 和 -3 的降解受损。为支持这一发现，在感染白色念珠菌酵母后，Dectin-1 在巨噬细胞中发生多泛素化。 ，而这种泛素化在缺乏 Cbl-b 的 BMDM 中被消除。此外，Cblb-/- 小鼠可以免受致死剂量的 C.基于这些结果，我们发现在白色念珠菌感染期间，Cbl-b 被招募到 Dectin CLR，并且这针对 Dectin 进行泛素化，从而抑制 CLR 介导的针对真菌的先天免疫反应。确定 (1) Cbl-b 是否以及如何在体外通过蛋白质泛素化调节 Dectin 下调；以及 (2) Cbl-b 是否抑制宿主对念珠菌的有效反应。该项目的成功完成将揭示以前未知的宿主防御机制，并提供对宿主防御机制的分子洞察，并最终促进适当调节抗真菌反应和治疗方案的候选靶点的识别。 。