Genetic determinants of mammalian host adaptation by the Lyme disease spirochete.

描述（由申请人提供）：伯氏疏螺旋体是一种专性寄生虫，并通过涉及蜱虫和哺乳动物宿主的复杂循环在自然界中维持。在这两种非常不同的宿主类型之间的转换需要通过基因表达的变化快速适应的能力。人工感染研究已经提供了许多这些基因的信息，这些基因可能在与脊椎动物宿主相似的条件下差异表达。尽管取得了这些进展，但我们对许多基因在哺乳动物宿主适应中的作用和功能的理解仍然存在根本性的差距。我们的长期目标是鉴定和表征伯氏疏螺旋体适应蜱虫和哺乳动物宿主环境所必需的蛋白质。本应用程序的总体目标是利用小鼠模型鉴定伯氏疏螺旋体适应哺乳动物宿主所需的候选基因。中心假设是大量功能未知的伯氏疏螺旋体基因被适应性表达。此外，我们假设许多对宿主适应很重要的基因要么是短暂表达，要么是在小鼠感染的后期才被开启。提出这项研究的基本原理是，一旦确定了与适应宿主环境有关的基因，就有可能确定它们在建立哺乳动物感染中的各自作用。因此，拟议的研究与NIH的使命有关，即发展基础知识，这可能有助于减轻人类疾病和残疾的负担。在已发表的伯氏疏螺旋体基因组序列和其他研究小组引用的工作的指导下，我们的假设将通过两个特定目标进行验证：1)确定伯氏疏螺旋体适应哺乳动物宿主环境的相关基因；2)确定伯氏疏螺旋体在哺乳动物感染中重要的后期宿主适应因子。在第一个目标下，我们将利用体内表达技术（IVET）。该系统将利用基于启动子的伯氏疏螺旋体基因组DNA文库，该文库旨在选择仅在小鼠宿主中具有活性的启动子。第二个目标是利用IVET系统的改进版本，称为重组酶型IVET （RIVET）。该系统还将利用基于启动子的伯氏疏螺旋体基因组DNA文库，但其设计仅允许选择那些在小鼠宿主中短暂或在感染后期活跃的启动子。提出的工作是创新的，因为它利用了特定伯氏疏螺旋体蛋白的基本活性作为识别重要毒力因子的新手段。当应用时，拟议研究的结果有望允许靶向该系统，以显着降低该病原体在哺乳动物宿主中建立感染的能力。

DESCRIPTION (provided by applicant): Borrelia burgdorferi is an obligate parasite, and is maintained in nature through a complex cycle involving both a tick and mammalian host. The transition between these two very different host types requires the ability to rapidly adapt through changes in gene expression. Artificial infection studies have provided information on a number of these genes that may be differentially expressed under conditions similar to that of the vertebrate host. Despite this advance, there remains a fundamental gap in our understanding of the role and function of a number of genes for mammalian host adaptation. Our long-term goal is to identify and characterize the proteins necessary for adaptation of B. burgdorferi to both the tick and mammalian host environments. The overall objective of this application is to identify B. burgdorferi candidate genes required for adapting specifically to the mammalian host using a mouse model. The central hypothesis is that a large number of B. burgdorferi genes of unknown function are adaptively expressed. Furthermore, we hypothesize that a number of genes important for host adaptation are either transiently expressed, or are turned on only during late-stage infection of mice. The rationale for the proposed research is that, once the genes involved in adapting to the host environment have been identified, it will be possible to determine their respective roles in establishing mammalian infection. Thus, the proposed research is relevant to that part of NIH's mission that pertains to developing fundamental knowledge that will potentially help to reduce the burdens of human illness and disability. Guided by the published B. burgdorferi genome sequence and cited work by other groups, our hypothesis will be tested by pursuing two specific aims: 1) Identify genes involved in the adaptation of B. burgdorferi to the mammalian host environment; and 2) Identify late-stage host adaptation factors of B. burgdorferi important for mammalian infection. Under the first aim, we will make use of In Vivo Expression Technology (IVET). This system will utilize a promoter-based genomic DNA library of B. burgdorferi that is designed to allow for the selection of only those promoters that are active exclusively within the mouse host. The second aim will utilize a modified version of the IVET system, termed Recombinase-based IVET (RIVET). This system will also make use of a promoter-based genomic DNA library of B. burgdorferi, but is designed to allow for the selection of only those promoters that are active transiently or during late-stage infection in the mouse host. The proposed work is innovative because it capitalizes on the essential activities of specific B. burgdorferi proteins as a new means of identifying important virulence factors. When applied, the results from the proposed studies are expected to allow the targeting of this system in order to significantly reduce the ability of this pathogen to establish infection in the mammalian host. PUBLIC HEALTH RELEVANCE: The proposed studies are of an important area of Lyme disease research that has applicability to understanding infectivity and pathogenesis by Borrelia burgdorferi. The proposed research has relevance to public health because the resulting discoveries have the potential to fundamentally advance the field of B. burgdorferi adaptive gene expression, and may have broad implications for host adaptation systems in other animal and human pathogens. Thus, the findings are ultimately expected to be applicable to the health of human beings.