Molecular dissection of Histoplasma-induced host-cell death

描述（由申请人提供）：我们研究的长期目标是了解真菌病原体荚膜组织胞浆菌如何引起疾病。H.荚膜组织胞浆菌是一种高毒力病原体，在免疫功能低下和免疫功能正常的个体中引起显著的发病率，在美国估计每年发生约500，000例组织胞浆菌感染。荚膜是巨噬细胞的病原体，巨噬细胞吞噬微生物并通过杀微生物机制的武库消化它们。与大多数微生物不同，H.荚膜在巨噬细胞吞噬体中复制到高水平。巨噬细胞定植后宿主细胞死亡并释放活酵母细胞，但引发宿主细胞死亡的机制尚不清楚。我们已经确定，以前确定的组织胞浆菌因子Cbp1是高细胞内真菌负荷，但需要宿主细胞裂解。此外，我们的初步研究发现，在感染期间，需要Cbp1诱导一组特定和有限的巨噬细胞基因的转录，我们将其命名为组织胞浆菌反应簇（HRC）。我们假设Cbp1与未知的宿主因子相互作用，导致这种独特的转录特征的诱导以及宿主细胞死亡。我们将（1）研究Cbp 1是否通过已建立的或新的途径触发宿主细胞死亡，（2）确定Cpb 1的哪些分子特征对宿主细胞死亡很重要，（3）确定Cbp 1是否是人类巨噬细胞发病所必需的，（4）评估Cbp 1在组织胞浆菌病小鼠模型中宿主细胞死亡和炎症中的作用。这些研究将产生人类真菌病原体在感染过程中使用的毒力策略的新范例。此外，确定宿主途径是Cbp1的潜在靶点，以及了解Cbp1调节的宿主细胞死亡如何促进疾病进展，将大大丰富我们对真核病原体如何进化以操纵其哺乳动物宿主的理解。 公共卫生相关性：荚膜组织胞浆菌是一种主要病原体，在美国每年感染约500，000人，是免疫功能低下患者发病率和死亡率的重要来源。对一种来自H. capsulatum将极大地推进我们对这种生物如何导致疾病的理解。

DESCRIPTION (provided by applicant): The long-term goal of our research is to understand how the fungal pathogen Histoplasma capsulatum causes disease. H. capsulatum is a highly virulent pathogen that causes significant morbidity in both immunocompromised and immunocompetent individuals, with approximately 500,000 Histoplasma infections estimated to occur every year in the U.S. H. capsulatum is a pathogen of macrophages, which phagocytose microbes and digest them via an arsenal of microbicidal mechanisms. In contrast to most microbes, H. capsulatum replicates to high levels in the macrophage phagosome. Colonization of the macrophage is followed by host-cell death and release of live yeast cells, but the mechanism that triggers host-cell death is unknown. We have determined that the previously identified Histoplasma factor Cbp1 is dispensable for high intracellular fungal burden, but required for host-cell lysis. Additionally, our preliminary studies uncovered that Cbp1 is required to induce transcription of a specific and limited set of macrophage genes during infection, which we have named the Histoplasma response cluster (HRC). We hypothesize that Cbp1 interacts with unknown host factors, resulting in the induction of this unique transcriptional signature as well as host-cell death. Here we will (1) investigate whether Cbp1 triggers host-cell death by established or novel pathways, (2) determine which molecular characteristics of Cpb1 are important for host cell death, (3) establish if Cbp1 is required for pathogenesis of human macrophages, and (4) assess the role of Cbp1 in host-cell death and inflammation in the mouse model of histoplasmosis. These studies will generate new paradigms of virulence strategies used by human fungal pathogens during infection. Additionally, identifying host pathways that are potential targets of Cbp1, as well as understanding how Cbp1-modulated host-cell death contributes to disease progression, will significantly enrich our understanding of how eukaryotic pathogens have evolved to manipulate their mammalian hosts. PUBLIC HEALTH RELEVANCE: Histoplasma capsulatum is a primary pathogen that infects approximately 500,000 individuals per year in the U.S. and is a significant source of morbidity and mortality in immunocompromised patients. The characterization of a fungal virulence factor from H. capsulatum will significantly advance our understanding of how this organism causes disease.