Pathogenesis of Cryptococcus Spores

描述(申请人提供)：我们的目标是确定控制新生隐球菌和哺乳动物免疫系统之间相互作用的分子机制，以努力最终预防和治疗真菌疾病。真菌是新出现的病原体，在免疫受损的人中发病率和死亡率最明显，特别是在感染艾滋病毒/艾滋病的人中。引起脑膜炎的真菌新生隐孢子菌在艾滋病患者中尤其具有攻击性，据估计，每年在全球范围内导致100多万人患病，约60万人死亡。这一负担的大部分发生在撒哈拉以南非洲，那里死于隐球菌性脑膜炎的人数现在似乎超过了死于结核病的人数。在这一地区，与艾滋病毒/艾滋病有关的死亡有13-44%是由隐球菌病引起的，平均存活时间在发病后几周左右。在世界范围内，抗真菌药物的治疗可导致约80%的存活率，个体预后受到抗真菌药物的可获得性和宿主的免疫状态的强烈影响。人们对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很大差距。过去20年的研究已经开始确定新生芽孢杆菌酵母和宿主免疫系统之间的关系，但还没有人评估孢子，即自然界中可能具有感染性的颗粒。我们最近已经将孢子纯化成同质的数量，足以进行全面的生化、分子和毒力研究。使用这种新的试剂，我们发现孢子可以在小鼠模型中导致疾病，而小鼠肺泡巨噬细胞是抵抗呼吸道真菌病原体的第一道防线，与孢子和酵母的相互作用从根本上不同。我们的发现使我们处于一个独特的位置，可以提出关于新生葡萄球菌-哺乳动物细胞界面的问题，这在以前是不可能的。我们将利用这一重大进展来研究孢子的基本性质及其与肺泡巨噬细胞的相互作用。我们的假设是，肺泡巨噬细胞通过不同于与酵母菌相互作用的特定机制与孢子相互作用。我们将通过解决以下三个目标来验证我们的假设。1)确定介导新生葡萄球菌孢子与小鼠肺泡巨噬细胞相互作用的受体和配体。2)阐明控制孢子在巨噬细胞内存活能力的机制。3)用小鼠感染模型研究孢子介导性疾病的特性。我们的研究将提供基本的见解，以了解新生葡萄球菌是如何被先天性免疫反应识别的，以及隐球菌疾病是如何在健康的个体中被抑制或在免疫受损的人中传播的。最终，我们的发现有望告知真菌致病的更一般过程，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.