Brain dissemination of Cryptococcus neoformans mediated by neutrophils

描述（由申请方提供）：新型隐球菌是一种胶囊化芽殖酵母，在免疫功能低下的个体中引起危及生命的疾病，如艾滋病患者、器官移植受者和接受免疫抑制治疗的患者。虽然感染始于肺部，但隐球菌病通常表现为脑膜脑炎，这是中枢神经系统最常见的感染之一，也是HIV感染者死亡的主要原因。血行播散C.从肺到脑的新型隐球菌被认为是隐球菌脑膜脑炎进展中最关键的一步。然而，由于体内研究的技术挑战，人们对它是如何发生的仍然知之甚少。C. neoformans是一种兼性细胞内 能在吞噬细胞中存活的病原体。我们的初步研究为C.新生儿在肺中被吞噬，随后在吞噬细胞内扩散到血液中。由于中性粒细胞是血流中最丰富的吞噬细胞，并且已被证明被招募到感染的肺中用于吞噬酵母细胞，因此我们开发了一种新的体内吞噬模型来研究含有摄入的C.使用活体显微镜观察新生儿。根据我们的初步数据显示，相当数量的中性粒细胞含有C。新生儿感染后滚动/爬行并粘附于脑血管，我们假设中性粒细胞介导了C.通过真菌的非溶解性胞吐作用和细胞内的直接细胞间扩散， 真菌从粘附的受感染的中性粒细胞到脑血管系统中的内皮细胞。我们将通过活体显微镜和其他先进的方法在体外和体内验证这一假设：（1）研究携带摄入的C。新生儿从肺到脑血管系统;（2）表征C.通过嗜中性粒细胞和酵母细胞的BBB交叉，通过从粘附的感染的嗜中性粒细胞到脑血管系统中的内皮细胞的直接细胞-细胞传播，感染新生儿。这些研究将为C.新形式，促进新的预防和治疗策略的发展。

DESCRIPTION (provided by applicant): Cryptococcus neoformans is an encapsulated budding yeast that causes a life-threatening illness in immunocompromised individuals, such as patients with AIDS, organ transplant recipients, and those treated with immunosuppressive therapies. Although the infection starts in the lung, cryptococcosis commonly presents as meningoencephalitis, which is one of the most common infections of the central nervous system and the leading cause of death in HIV-infected individuals. Hematogenous dissemination of C. neoformans from the lung to the brain is believed to be the most critical step in the progression of cryptococcal meningoencephalitis. How it happens, however, remains poorly understood because of the technical challenge of in vivo studies. C. neoformans is a facultative intracellular pathogen that can survive in phagocytes. Our preliminary study has provided direct evidence that C. neoformans is engulfed in the lung and subsequently disseminate to the blood within phagocytes. As neutrophils are the most abundant phagocytes in the bloodstream and have been shown to be recruited to the infected lung for phagocytosis of the yeast cells, we have developed a novel in vivo phagocytosis model to study the migration of neutrophils containing ingested C. neoformans using intravital microscopy. Based on our preliminary data showing that considerable numbers of neutrophils containing C. neoformans roll/crawl and adhere to brain vasculature after infection, we hypothesize that neutrophils mediate brain dissemination of C. neoformans by nonlytic exocytosis of the fungus and direct cell-to-cell spread of the intracellular fungus from adherent infected neutrophils to endothelial cells in the brain vasculature. We will test the hypothesis in vitro as well as in vivo by addressing the following aims using intravital microscopy and other advanced approaches: (1) Investigate migration of neutrophils harboring ingested C. neoformans from the lung to the brain vasculature; (2) Characterize nonlytic exocytosis of C. neoformans by neutrophils and the BBB crossing of the yeast cells via a direct cell-to-cell spread from adherent infected neutrophils to endothelial cells in the brain vasculature. The proposed studies will provide unique insights into brain dissemination of C. neoformans, facilitating the development of novel prevention and therapeutic strategies.