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组织胞浆菌是如何导致疾病的。包膜螺旋体是一种高度毒力的病原体，在免疫功能低下和免疫功能正常的人中都会导致显著的发病率，据估计，美国每年约有500,000例组织原体感染。包膜螺旋体是巨噬细胞的病原体，巨噬细胞吞噬微生物并通过大量杀菌机制将其消化。与大多数微生物不同的是，包膜螺旋体在巨噬细胞吞噬小体中复制水平很高。巨噬细胞定植之后是宿主细胞死亡和活酵母细胞的释放，但触发宿主细胞死亡的机制尚不清楚。我们已经确定，先前确定的组织胞浆因子Cbp1对于高细胞内真菌负荷是必要的，但对于宿主细胞裂解是必需的。此外，我们的初步研究发现，Cbp1在感染过程中需要诱导一组特定的和有限的巨噬细胞基因的转录，我们将其命名为组织胞浆反应簇(HRC)。我们假设Cbp1与未知的宿主因素相互作用，导致这种独特的转录信号的诱导以及宿主细胞的死亡。在这里，我们将(1)研究Cbp1是否通过已建立的或新的途径触发宿主细胞死亡，(2)确定Cbb1的哪些分子特征对宿主细胞死亡是重要的，(3)确定Cbp1是否是人类巨噬细胞发病所必需的，以及(4)在组织胞浆菌病小鼠模型中，评估Cbp1在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，识别作为Cbp1潜在靶标的宿主途径，以及了解Cbp1调节的宿主细胞死亡如何促进疾病进展，将极大地丰富我们对真核病原体如何进化来操纵它们的哺乳动物宿主的理解。

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.