Pathogenesis of Cryptococcus Spores

描述（由申请人提供）：我们的目标是确定控制新型隐球菌与哺乳动物免疫系统之间相互作用的分子机制，以最终预防和治疗真菌疾病。真菌是新兴病原体，发病率和死亡率在免疫功能低下的人群中最为明显，特别是在艾滋病毒/艾滋病患者中。引起脑膜炎的真菌新生梭状菌在艾滋病患者中具有特别强的攻击性，据估计，每年在全世界造成100多万例疾病和60万例死亡。这一负担的大部分发生在撒哈拉以南非洲，在那里，隐球菌性脑膜炎的死亡人数现在似乎超过了结核病的死亡人数。在该地区，13-44%的艾滋病毒/艾滋病相关死亡是由隐球菌病造成的，平均生存时间在发病后几周左右。在世界范围内，抗真菌药物治疗的存活率约为80%，个体预后受到抗真菌药物的可用性和宿主免疫状态的强烈影响。关于隐球菌感染发生的过程知之甚少，我们认识到在理解真菌病原体和宿主免疫反应之间的交集方面存在实质性差距。过去二十年的研究已经开始确定新形梭菌酵母菌和宿主免疫系统之间的关系，但没有一个研究评估过孢子，它们可能是自然界中的感染性颗粒。我们最近纯化的孢子数量均匀，足以进行全面的生化、分子和毒力研究。使用这种新型试剂，我们发现孢子可以在小鼠模型中引起疾病，并且小鼠肺泡巨噬细胞（抵抗呼吸道真菌病原体的第一道防线）与孢子的相互作用与与酵母的相互作用根本不同。我们的发现使我们处于一个独特的位置，可以提出以前不可能提出的关于C.新生生物-哺乳动物细胞界面的问题。我们将利用这一重大进展来研究孢子的基本特性及其与肺泡巨噬细胞的相互作用。我们的假设是，肺泡巨噬细胞通过特定的机制与孢子相互作用，这与那些介导与酵母相互作用的机制不同。我们将通过解决以下三个目标来验证我们的假设：1)鉴定介导新生芽孢杆菌孢子和小鼠肺泡巨噬细胞之间相互作用的受体和配体。2)阐明孢子在巨噬细胞内存活的机制。3)利用小鼠感染模型研究孢子介导疾病的特性。我们的研究将为理解新生隐球菌如何被先天免疫反应识别以及隐球菌疾病如何在健康个体中被抑制或在免疫功能低下者中传播提供基础见解。最终，我们的发现有望为真菌引起疾病的更一般过程提供信息，促进发现新的预防和/或治疗策略。

DESCRIPTION (provided by applicant): Our goal is to define the molecular mechanisms that control interactions between Cryptococcus neoformans and the mammalian immune system in an effort to ultimately prevent and treat fungal disease. Fungi are emerging pathogens, and morbidity and mortality are most apparent among the immunocompromised, especially in individuals with HIV/AIDS. The meningitis-causing fungus C. neoformans is particularly aggressive among people with AIDS, estimated to cause over a million cases of disease and ~600,000 deaths world-wide annually. The bulk of this burden is in Sub-Saharan Africa where the number of deaths from cryptococcal meningitis now appears to surpass the number of deaths from tuberculosis. In this region 13-44% of HIV/AIDS-related deaths are due to cryptococcosis, and mean survival times are on the order of a few weeks after onset. Worldwide, treatment with antifungal agents results in ~80% survival, and individual prognoses are strongly influenced by the availability of antifungal drugs and the immune status of the host. Little is known about the processes by which cryptococcal infection occurs, and we recognize a substantial gap in understanding the intersection between fungal pathogens and the host immune response. Studies over the last two decades have begun to define the relationships between C. neoformans yeast and the host immune system, but none has evaluated spores, likely infectious particles in nature. We have recently purified spores to homogeneity in numbers sufficient for comprehensive biochemical, molecular, and virulence studies. Using this novel reagent we have discovered that spores can cause disease in a mouse model and that murine alveolar macrophages, the first line of defense against respiratory fungal pathogens, interact fundamentally differently with spores than with yeast. Our findings place us in a unique position to ask questions about the C. neoformans-mammalian cell interface that have not been possible previously. We will take advantage of this major advance to investigate the fundamental properties of spores and their interactions with alveolar macrophages. Our hypothesis is that alveolar macrophages interact with spores via specific mechanisms that are distinct from those that mediate interactions with yeast. We will test our hypothesis by addressing the following three Aims. 1) Identify the receptors and ligands that mediate interactions between C. neoformans spores and murine alveolar macrophages. 2) Elucidate mechanisms that govern the ability of spores to survive inside macrophages. 3) Investigate the properties of spore-mediated disease using a murine model of infection. Our studies will provide insights fundamental to understanding how C. neoformans is recognized by the innate immune response and how cryptococcal disease is either suppressed in healthy individuals or disseminated in the immunocompromised. Ultimately, our findings promise to inform more general processes by which fungi cause disease, facilitating the discovery of novel prevention and/or treatment strategies. PUBLIC HEALTH RELEVANCE: Fungi, including Cryptococcus, are emerging pathogens that cause life-threatening diseases in humans, particularly people who are immunocompromised. Investigating interactions between Cryptococcus spores and the human immune system promises to provide the information necessary to understand how fungal spores cause disease. This project is relevant to public health and the mission of the NIH because it has the potential to lead to new strategies for preventing and/or treating severe fungal infections among the most vulnerable patients, including those with HIV/AIDS.