Role of fascin1 in dendritic cell-mediated immunity against listeria infection

描述（由申请方提供）：本R03申请的目的是确定fascin1在抗单核细胞增生李斯特菌（Lm）感染的树突状细胞（DC）免疫中的体内作用。DC是最强的抗原提呈细胞，在先天性和获得性免疫中起着核心作用。当DC遇到病原体时，它们经历称为成熟的终末分化：它们组装许多面纱样膜突起，从外周组织行进到引流淋巴结，并将抗原呈递给幼稚T细胞。Fascin1是DC中独特的肌动蛋白捆绑蛋白，因为它在DC成熟时被大量且特异性地诱导。Fascin1在未成熟的DC或其他血细胞（包括巨噬细胞、中性粒细胞和自然杀伤细胞）中不存在，表明Fascin1在成熟后的DC生物学中的特定作用。事实上，我们和其他人已经证明，fascin1是至关重要的成熟相关的功能，包括大量重组的肌动蛋白细胞骨架，趋化性迁移的DC到引流淋巴结，T细胞活化和组装的免疫突触。我们已经发现，通过表征fascin1 KO DC，fascin1在DC介导的宿主防御系统中起着新的作用。有报道称，DC对Lm的细胞内杀伤活性强于巨噬细胞。这种对Lm的抗性被认为对于DC的抗原呈递的主要功能是至关重要的：DC必须在外周感染后存活，然后移动到引流淋巴结以将抗原信息转移到T细胞。我们发现fascin1 KO DC对Lm介导的杀伤显示出更高的易感性。重要的是，具有高fascin1表达的DC对Lm感染具有极强的抵抗力。我们进一步发现，fascin1使LM包裹的吞噬体更酸性，并增加自噬通量。这些结果表明，fascin1增加了用于细菌清除的吞噬体和自噬体的溶酶体融合，解释了为什么DC（fascin1阳性）比巨噬细胞（fascin1阴性）更具抗性。然而，一个关键问题仍有待回答：fascin1对于体内基于DC的针对Lm感染的适应性和先天性免疫至关重要吗？我们将研究，通过使用Lm小鼠模型，是否fascin1基因敲除小鼠表现出降低的适应性和先天性免疫反应Lm感染。该提案可能会提供重要信息，帮助我们开发新的基于DC的细菌感染免疫疗法。 公共卫生相关性：阐明fascin1在抗单核细胞增生李斯特菌（Lm）感染的先天性和适应性免疫中的体内作用，可能会对我们理解宿主对细胞内病原体的防御产生变革性影响。表达Fascin1的树突状细胞（DC）通过控制Lm和可能的其他病原体的细胞内增殖，预期有效地将病原体信息转移到T细胞，从而导致细菌病原体的清除。我们认为，fascin1表达树突状细胞（DC），因此可以利用DC为基础的免疫治疗。

DESCRIPTION (provided by applicant): The goal of this R03 application is to determine in vivo roles of fascin1 in dendritic cell (DC)-based immunity against infection of Listeria monocytogenes (Lm). DCs, the most potent antigen presenting cells, play central roles in both innate and acquired immunity. When DCs encounter pathogens, they undergo terminal differentiation called maturation: they assemble numerous veil-like membrane protrusions, travel from the peripheral tissues to draining lymph nodes, and present antigens to naive T-cells. Fascin1 is a unique actin-bundling protein in DCs because it is greatly and specifically induced upon DC maturation. Fascin1 is absent in immature DCs or in other blood cells including macrophages, neutrophils and natural killer cells, suggesting a specific role for fascin1 in DC biology upon maturation. Indeed, we and others have demonstrated that fascin1 is critical for the maturation-associated functions including massive reorganization of the actin cytoskeleton, chemotactic migration of DCs into draining lymph nodes, T-cell activation and assembly of the immunological synapse. We have found, by characterizing fascin1 KO DCs, that fascin1 plays a novel role in a DC-mediated host defense system. It has been reported that DCs show a stronger intracellular killing activity toward Lm than do macrophages. This resistance to Lm is thought to be crucial for the DCs primary function of antigen presentation: DCs must survive infection at the periphery and then move to draining lymph nodes for transferring antigen information to T-cells. We found that fascin1 KO DCs displayed higher susceptibility to Lm-mediated killing. Importantly, DCs with high fascin1 expression was extremely resistant to Lm infection. We further found that fascin1 made Lm-encapsulated phagosomes more acidic, and increases autophagy flux. These results indicate that fascin1 increases lysosomal fusion of both phagosomes and autophagosomes for bacterial clearance, explaining why DCs (fascin1-positive) are more resistant than macrophages (fascin1-negative). However, a key question remains to be answered: Is fascin1 crucial for DC-based adaptive and innate immunity against Lm infection in vivo? We will examine, by using the Lm mouse model, whether fascin1 KO mice show reduced adaptive and innate immune responses to Lm infection. The proposal is likely to provide vital information that will help us develop new DC-based immunotherapy against bacterial infection. PUBLIC HEALTH RELEVANCE: The elucidation of the in vivo role of fascin1 in innate and adaptive immunity against Listeria monocytogenes (Lm) infection could have a transformative effect on our understanding of host defense toward intracellular pathogens. Fascin1-expressing dendritic cells (DCs), by controlling intracellular proliferation of Lm and possibly other pathogens, are expected to effectively transfer pathogen information to T-cells, thereby leading to clearance of bacterial pathogens. We suggest that fascin1-expressing dendritic cells (DCs) could thus be utilized in DC-based immunotherapy.