The link between dimorphism and virulence in Cryptococcus

新型隐球菌引起隐球菌病，每年夺去数十万人的生命。 这种真菌病的死亡率高得令人无法接受（10-70%）。目前的抗真菌治疗 隐球菌病极为有限，而且没有疫苗可用。因此，我们迫切需要了解 隐球菌程序，可以选择性地通过新的抗真菌药或疫苗的目标。隐球菌可以 假设不同的形态型：酵母形式被认为是致病性的，而丝状形式被认为是致病性的。 毒性减弱因此，了解形态变化的分子基础及其 可以利用对隐球菌毒力的影响来对抗这种致命疾病。在第一阶段， 研究项目，我们建立了Znf 2作为调节桥梁的形态和毒力潜力， 隐球菌ZNF 2的缺失将细胞锁定在酵母形式并增强隐球菌的毒力。相反地， ZNF 2过表达促进菌丝生长。过表达ZNF-2的隐球菌细胞诱导保护性免疫反应 在哺乳动物宿主中的防御反应，并且是无毒的。更重要的是，用ZNF 2免疫 过表达细胞，无论是活的还是热灭活的形式，都可以为宿主提供100%的保护， 随后通过其它致死野生型H99感染进行攻击。这种保护很少得到遵守 对抗这种致命的真菌病原体因此，Znf 2的活化代表了一种有前途的手段， 妥协隐球菌的致病性，并提供了一个载体，研究宿主免疫。假设Znf 2是 隐球菌菌丝形态发生的决策者，其调节子富含分泌蛋白 包括粘附蛋白，我们假设ZNF 2的激活改变了细胞表面的组成， 存在于ZNF 2过表达细胞中的某些细胞组分是有效的免疫原。因此对于 在本研究项目的第二阶段，我们将鉴定ZNF 2过表达细胞中存在的免疫原， 可以在AIM 1中引发保护性宿主免疫应答。在目标2中，我们将确定Znf 2调节回路 （激活子、阻遏子和/或受体），并评估它们在隐球菌毒力中的作用。我们假设 开启激活物和/或抑制这种有效的抗毒力因子的阻遏物， 在感染期间损害隐球菌的致病性。我们的初步数据表明，ZnF 2可以 在感染过程中人工强烈激活，但其激活在野生型细胞中被抑制。我们预计 第二阶段的研究成果将使我们更接近我们的长期目标： 了解形态发生和致病性的基本要求，使用隐球菌作为 遗传模型，并利用这些知识来制定预防和治疗措施， 侵袭性真菌病

Cryptococcus neoformans causes cryptococcosis that claims hundreds of thousands of lives annually. The mortality rates of this fungal disease are unacceptably high (10-70%). Current antifungal treatments for cryptococcosis are extremely limited and no vaccine is available. Thus, there is a critical need to understand cryptococcal programs that could be selectively targeted by novel antifungals or vaccines. Cryptococcus can assume different morphotypes: the yeast form is considered pathogenic and the filamentous form is associated with attenuated virulence. Therefore, understanding the molecular bases for morphological changes and their impact on cryptococcal virulence could be exploited to combat this fatal disease. During the first phase of this research project, we established Znf2 as the regulator bridging morphotype and virulence potential in Cryptococcus. Deletion of ZNF2 locks cells in the yeast form and enhances cryptococcal virulence. Conversely, ZNF2 overexpression promotes hyphal growth. Cryptococcal cells overexpressing ZNF2 elicit protective defense responses in the mammalian host and are avirulent. More importantly, immunization with ZNF2 overexpression cells, either in live or heat-killed form, can offer 100% protection to the host against a subsequent challenge by an otherwise lethal wild-type H99 infection. Such protection is rarely observed against this deadly fungal pathogen. Therefore, activation of Znf2 represents a promising means to compromise cryptococcal pathogenicity and provides a vehicle to study host immunity. Given that Znf2 is the decision-maker for cryptococcal hyphal morphogenesis and its regulon is enriched with secretory proteins including adhesion proteins, we hypothesize that activation of ZNF2 alters cell surface composition and that certain cellular components present in ZNF2 overexpression cells are effective immunogens. Therefore, for the second phase of this research project, we will identify immunogens present in ZNF2 overexpression cells that can elicit protective host immune responses in aim 1. In aim 2, we will determine Znf2 regulatory circuits (activators, repressors, and/or receptors) and assess their roles in cryptococcal virulence. We hypothesize that turning on the activator and/or inhibiting the repressor of this potent anti-virulence factor could be exploited to compromise cryptococcal pathogenicity during infection. Our preliminary data suggest that Znf2 can be strongly activated artificially during infection, but its activation is subdued in wild-type cells. We expect that results obtained from the second phase of the research project will move us closer to our long term goals: to understand the fundamental requirements for morphogenesis and pathogenicity using Cryptococcus as a genetic model, and to harness such knowledge to develop preventative and therapeutic measures against invasive mycoses.