Control of Type I Interferon Production in Response to Candida albicans

项目摘要 侵袭性真菌感染是免疫功能低下患者的主要威胁， 真菌抗生素，死亡率仍高达50%。念珠菌在医院获得性病原体中排名第五， 第四是血液感染。I型干扰素（IFN）途径中的人类SNP与以下因素相关： 增加对念珠菌血症的易感性。虽然这些数据表明I型IFN在C.白色念珠菌宿主防御， 在C.白色念珠菌感染仍然是难以捉摸的。 浆细胞样树突状细胞（plasmacytoid dendritic cells，pDC）是I型干扰素（IFNα和IFNβ）的主要产生者，但数量较少 尽管其它细胞（即巨噬细胞和单核细胞）也有助于I型IFN 生产也是。在激活后，Toll样受体（TLR）7和9可以上调I型IFN的产生，或 分别通过IRF-7和NF-κB途径产生趋化因子/细胞因子。虽然I型IFN的诱导是良好的， 描述了对病毒和细菌病原体的反应，一个关键的知识缺口仍然是关于机制， 该途径影响真菌的发病机制。我们已经做了几个关键的观察，以确定I型IFN的作用， 回应C。白色念珠菌。我们发现感染C.静脉注射白色念珠菌显著上调 活化标志物，CD 40和CD 86。IFNα/β需要TLR 9和Dectin-1 生产TLR 9运输到真菌内体需要Dectin-1和Syk信号传导。此外，微阵列分析 野生型和TLR 9敲除的巨噬细胞显示IFN诱导型家族基因（IFI 203，Mnda和Ifi 1）依赖于 在TLR 9上，暗示其在IFN信号传导的调节中的作用。I型干扰素提高嗜中性粒细胞的杀伤能力， 回应C。白色念珠菌我们还证明了在缺乏关键的IFN信号传导组分（即STING， cGAS、IRF-3和IFN受体）小鼠表现出对念珠菌血症的显著抗性，但以较高的真菌感染为代价。 负担这些令人兴奋的数据表明，干扰素信号的失调显着影响的结果，侵入性 念珠菌感染。最后，我们的初步研究暗示了STING在负反馈产生中的作用 调节器SOCS 1（细胞因子信号传导抑制剂）。因此，我们的长期目标是了解 I型干扰素在宿主防御侵袭性念珠菌病中的作用。为了实现我们的长期目标，我们提出以下三点建议 目的：（1）阐明C.白色念珠菌，（2） 确定cGAS、STING和IRF-3在宿主防御念珠菌血症中的影响，以及（3）确定其机制 梭白色念珠菌诱导的SOCS 1阻断TLR 9依赖的I型IFN的产生。这项工作将提供更大 了解I型干扰素对侵袭性念珠菌病的反应，并可能导致新的治疗靶点，以调节 免疫应答改变念珠菌病患者的临床结果。

PROJECT SUMMARY Invasive fungal infections represent a major threat to immunocompromised patients and despite the availability of anti- fungal antibiotics, mortality rates remain as high as 50%. Candida spp. is fifth among hospital-acquired pathogens and fourth among bloodstream infections. Human SNPs in the type I interferon (IFN) pathway have been associated with increased susceptibility to candidemia. While these data suggest a significant role of type I IFNs in C. albicans host defense, the signaling pathway that licenses type I IFN production and regulation during C. albicans infection remains elusive. Although small in numbers, plasmacytoid dendritic cells (pDCs) are the primary producers of type I IFNs (IFNα and IFNβ) in response to viral and bacterial pathogens though other cells (i.e. macrophages and monocytes) contribute to type I IFN production as well. Upon activation, toll-like receptors (TLRs) 7 and 9 can upregulate type I IFN production or chemokine/cytokine production via IRF-7 and NF-κB pathways, respectively. Although induction of type I IFNs are well described in response to viral and bacterial pathogens, a crucial knowledge gap remains with respect to the mechanisms by which this pathway affects fungal pathogenesis. We have made several key observations to define the role of type I IFNs in response to C. albicans. We show that pDCs from mice infected with C. albicans intravenously significantly upregulate the activation markers, CD40 and CD86, as compared to uninfected mice. TLR9 and Dectin-1 are required for IFNα/β production. TLR9 trafficking to fungal endosomes require Dectin-1 and Syk signaling. Furthermore, a microarray analysis of wild-type and TLR9-knockout macrophages revealed IFN inducible family genes (IFI203, Mnda, and Ifi1) as dependent on TLR9, implicating its role in the regulation of IFN signaling. Type I IFNs improve killing capacity of neutrophils in response to C. albicans. We additionally demonstrated that in the absence of critical IFN signaling components (i.e. STING, cGAS, IRF-3, and IFN receptor) mice demonstrate striking resistance to candidemia, but at the cost of a higher fungal burden. These exciting data suggest that dysregulation of IFN signaling significantly affects the outcomes of invasive Candida infections. Lastly, our preliminary studies implicate a role for STING in the production of the negative feedback regulator SOCS1 (suppressor of cytokine signaling). Thus, our long-term goal is to understand the regulation and role of type I IFNs in host defense against invasive candidiasis. To address our long-term goal, we propose the following three aims: (1) elucidate the signaling pathway for TLR9-dependent type I IFN production in response to C. albicans, (2) determine the impact of cGAS, STING, and IRF-3 in the host defense against candidemia, and (3) identify the mechanism of C. albicans-induced SOCS1 to block TLR9-dependent type I IFN production. This work will provide greater understanding of type I IFN response to invasive candidiasis and may lead to novel therapeutic targets to modulate the immune response to alter clinical outcomes in candidemic patients.