Dysregulation of Innate Immune Responses by Borrelia burgdorferi:A Role for IL-10

描述（由申请人提供）：大多数感染伯氏疏螺旋体（Bb）的人将发展莱姆病，莱姆病占美国所有媒介传播疾病的90%以上，每年直接医疗费用和生产力损失达10 - 20亿美元。这种感染激发了强有力的先天性和适应性免疫反应，通常无法清除细菌，导致靶组织中的持续感染和疾病。通过先天免疫细胞上的Toll样受体2早期识别Bb脂蛋白似乎对于从宿主组织中清除细菌至关重要，然而我们目前对预防莱姆病至关重要的特定先天反应没有明确的了解。我们以前的研究表明，IL-10缺陷型小鼠（IL-10-/-）控制宿主组织中的Bb水平显著优于野生型（WT）小鼠，因此使IL-10成为唯一显示出显著影响Bb清除的细胞因子。我们的初步数据进一步表明，1）可行的（但不被杀死）Bb从鼠巨噬细胞（MX）和树突细胞（DC）中引发高IL-10水平，2）IL-10的分泌水平可以显著抑制驻留MX的随后活化，3）在感染的24小时内在小鼠皮肤中检测到显著的IL-10水平，和4）IL-10-/-小鼠不表现出这些抑制作用，导致增强的MX活性和免疫清除。我们假设，IL-10阐述在响应于Bb感染，抑制宿主先天性免疫反应，这是至关重要的有效的Bb清除宿主组织，和MX和DC功能是中央的这种失调的主机响应。该提议的总体目标是：1）鉴定最初检测并响应于鼠组织中的Bb的细胞类型，2）确定哪些细胞类型负责在感染过程中产生IL-10，以及3）描述哪些免疫细胞类型受到Bb引发的IL-10的不利影响以及哪些免疫机制失调。为了实现这些目标，目标1将比较IL-10对MX和DC摄取、内部运输和介导体外Bb杀伤的能力的影响，包括活化/成熟标志物的表达。目的2将利用一些遗传突变的小鼠系来描述造血和非造血细胞以及MX、DC和T细胞在体内Bb感染期间产生IL-10和/或对IL-10应答的相对重要性。目的3将严格测试IL-10受体阻断抗体的施用是否可用作感染Bb的小鼠的治愈性疗法。这些研究应该澄清在莱姆病发展过程中受到抑制的特定宿主免疫机制，从而开发新的治疗方法。与公共卫生的关系感染B。莱姆病引起宿主组织显著增加IL-10的产生，这抑制了宿主免疫应答并阻碍了它们清除这种感染的能力，导致莱姆病的发展。IL-10是目前已知的唯一显著影响莱姆病发展的细胞因子，并且代表了该病原体的免疫逃避机制的重要线索。这些研究旨在鉴定产生IL-10的宿主细胞，以及受IL-10失调的免疫细胞，从而鉴定可以靶向治疗莱姆病患者的机制。

DESCRIPTION (provided by applicant): Most people infected with Borrelia burgdorferi (Bb) will develop Lyme disease, which accounts for >90% of all vector-borne illnesses in the United States, and e $1-2 billion each year in direct medical expenses and lost productivity. This infection elicits potent innate and adaptive immune responses that often fail to clear the bacteria, leading to persistent infection and disease in targeted tissues. Early recognition of Bb lipoproteins through Toll-like receptor 2 on innate immune cells appears to be crucial for bacterial clearance from host tissues, however we currently have no clear understanding of the particular innate responses that are critical for preventing Lyme disease. Our previous studies revealed that IL-10-deficient mice (IL-10-/-) control Bb levels in host tissues significantly better than wild type (WT) mice, thus making IL-10 the only cytokine shown to significantly affect Bb clearance. Our preliminary data further indicate that 1) viable (but not killed) Bb elicit high IL-10 levels from murine macrophages (MXs) and dendritic cells (DCs), 2) that the secreted levels of IL-10 can significantly inhibit subsequent activation of resident MXs, 3) that significant IL-10 levels are detected in mouse skin within 24h of infection, and 4) that IL-10-/- mice do not exhibit these suppressive effects, leading to enhanced MX activity and immune clearance. We hypothesize that the IL-10 elaborated in response to Bb infection, suppresses host innate immune responses that are crucial for efficient Bb clearance from host tissues, and that MX and DC functions are central to this dysregulated host response. The overall goals of this proposal are: 1) to identify the cell types that initially detect and respond to Bb in murine tissues, 2) to determine which cell types are responsible for producing IL-10 during the course of infection, and 3) to delineate which immune cell types are adversely affected by Bb-elicited IL-10 and which immune mechanisms are dysregulated. To approach these goals, Aim 1 will compare IL-10 effects on the abilities of MXs and DCs to ingest, internally traffic, and mediate killing of Bb in vitro, including the expression of activation/maturation markers. Aim 2 will utilize a number of genetically mutated mouse lines to delineate the relative importance of hemopoietic and nonhemopoietic cells, as well as MXs, DCs, and T cells to both produce IL-10 and/or respond to IL-10 during Bb infection in vivo. Aim 3 will rigorously test whether administration of IL-10 receptor-blocking antibodies could be used as a curative therapy for mice infected with Bb. These studies should clarify specific host immune mechanisms that are suppressed during the development of Lyme disease, leading to the development of novel treatments. PUBLIC HEALTH RELEVANCE Infection with B. burgdorferi causes host tissues to significantly increase IL-10 production, which suppresses the host immune responses and hinders their ability to clear this infection, leading to the development of Lyme disease. IL-10 is the only cytokine that is currently known to significantly affect the development of Lyme disease and represents an important clue into the immune evasion mechanism of this pathogen. These studies intend to identify the host cells that produce IL-10, as well as the immune cells that are dysregulated by IL-10, thus identifying mechanisms that could be targeted to treat Lyme disease patients.