Interaction of H. capsulatum with Dendritic Cells

描述(由申请人提供)：组织胞浆菌(HC)是一种具有世界重要性的二相性真菌病原体，可引起广泛的疾病活动。尽管大多数有免疫能力的人感染过程轻微，但在因血液系统恶性肿瘤、细胞毒治疗或获得性免疫缺陷综合征(AIDS)而免疫受损的人中，HC可能会产生进行性播散性感染。感染HC是通过吸入微孢子进入肺泡而获得的。分生孢子转化为致病酵母期，酵母被肺泡巨噬细胞(AM)吞噬。分裂的酵母菌破坏AM，然后它们被其他AM摄取，并被炎性中性粒细胞和巨噬细胞(M-Phi)摄取。重复这个循环会导致HC通过血液和淋巴管传播。针对HC的特异性细胞介导免疫(CMI)的成熟激活了M-Phi，从而阻止了酵母的增殖，逐渐解决了疾病的过程。 尽管树突状细胞(DC)是免疫系统中最强大的抗原提呈细胞(APC)，并且在CMI的诱导中起关键作用，但它们在宿主抵抗真菌中的作用在很大程度上被忽视了。这项研究的总体目标是了解HC与DC相互作用的生物学和生物化学，并表征DC在诱导HC保护性免疫中的作用。该提案的主要目的是：1)确定小鼠肺DC是否摄取并限制HC分生孢子向酵母菌的转化。具体来说，我们将确定肺树突状细胞是否吞噬HC分生孢子，确定识别是否通过VLA-5，确定分生孢子在细胞内的命运，鉴定感染HC的DC产生的细胞因子，并确定为什么HC被M-Phi和DC上的不同受体识别。2)从T细胞增殖、细胞因子的产生和对共刺激分子的需求方面，确定HC感染的DC和T细胞之间的抗原提呈的功能相关性，并确定DC-HC-T细胞相互作用是否产生激活M-Phi抗组织胞浆活性的细胞因子。3)确定HC抗原致敏的DC在肺组织胞浆菌病小鼠模型中是否具有保护性免疫作用，并确定免疫活性和免疫缺陷小鼠保护性免疫的免疫学参数。这些研究的结果将为组织胞浆菌病的发病机制提供重要的洞察力，并有助于设计新的疫苗策略来预防疾病。

DESCRIPTION (provided by applicant): Histoplasma capsulatum (Hc) is a dimorphic fungal pathogen of worldwide importance that causes a broad spectrum of disease activity. Although the course of infection is mild in most immunocompetent individuals, Hc may produce progressive disseminated infections in individuals immunocompromised by hematologic malignancies, cytotoxic therapy, or in individuals with the acquired immunodeficiency syndrome (AIDS). Infection with Hc is acquired by inhalation of microconidia into the pulmonary alveoli. The conidia convert into the pathogenic yeast phase, and yeasts are phagocytized by alveolar macrophages (AM). Dividing yeasts destroy the AM, and then they are ingested by other AM, and by inflammatory neutrophils and macrophages (M-phi). Repetition of this cycle leads to dissemination of Hc via blood and lymphatics. Maturation of specific cell-mediated immunity (CMI) against Hc activates M-phi to halt yeast proliferation with gradual resolution of the disease process. Although, dendritic cells (DC) are the most potent antigen-presenting cells (APC) of the immune system, and are critical for the induction of CMI, their role in host defense against fungi has been largely ignored. The overall goal of the proposed research is to understand the biology and biochemistry of the interaction of Hc with DC, and to characterize the role of DC in the induction of protective immunity to Hc. The major objectives of the proposal are: 1) To determine if murine lung DC ingest and restrict the conversion of Hc conidia into yeasts. Specifically we will determine if lung DC phagocytose Hc conidia, determine if recognition is via VLA-5, determine the intracellular fate of conidia, identify the cytokines produced by Hc-infected DC, and determine why Hc is recognized by different receptors on M-phi and DC. 2) To identify the functional correlates for antigen presentation between Hc-infected DC and T cells with respect to T cell proliferation, cytokine production, and the requirement for co-stimulatory molecules, and to determine if DC-Hc-T cell interaction produces cytokines that activate M-phi anti-histoplasma activity. 3) To determine if Hc antigen-pulsed DC confer protective immunity in a murine model of pulmonary histoplasmosis, and to define the immunologic parameters of protective immunity in immunocompetent and immunocompromised mice. The results of these studies should provide significant insight into the pathogenesis of histoplasmosis and aid in the design of novel vaccine strategies for the prevention of disease.