M. avium GPLs in Macrophage Activation and Virulence

描述（由申请人提供）：鸟分枝杆菌是艾滋病患者的主要机会致病菌，也是肺部潜在疾病患者肺部感染的主要原因。然而，我们对鸟支原体发病机制的了解还很缺乏，部分原因是关于鸟支原体参与调节宿主反应的成分的信息有限。然而，先前的研究表明，糖肽类磷脂（GPLs）是许多非结核分枝杆菌表达的主要表面成分，可能在指导宿主对鸟分枝杆菌感染的反应中起作用。我们发现gpl可以参与模式识别受体toll样受体2 (TLR2)，导致巨噬细胞活化。有趣的是，我们发现GPL与TLR2相互作用的能力不同，GPL乙酰化和甲基化模式的细微变化决定了这种糖脂是否可以通过TLR2发出信号。gpl还可以与甘露糖受体结合，并且这种相互作用对于含有gpl包被珠的吞噬体观察到的溶酶体标记物的延迟指责是必需的。基于这些观察结果，我们推测鸟分枝杆菌在感染过程中可以改变其GPL结构，这是一个重要的毒力机制。此外，我们预测某些GPL变体在鸟分枝杆菌中的表达增加将与菌株的致病性相关。为了验证这些预测，我们将：1)定义GPL与MR结合和延迟吞噬体成熟的能力所必需的GPL结构成分，以及GPL介导这种延迟的机制。2)表征巨噬细胞和小鼠感染后M. avium菌株的GPL组成，并确定GPL组成与菌株毒力的关系。3)生成参与GPL生物合成基因的鸟分枝杆菌敲除突变体，并在小鼠感染模型中评估GPL介导的活性，包括通过TLR2和MR信号传导、生物膜形成和滑动运动以及毒力。在完成这些研究后，我们将更好地了解鸟分枝杆菌的发病机制和gpl在这一过程中所起的作用，所获得的信息可能会导致开发新的诊断工具来评估鸟分枝杆菌的毒力。

DESCRIPTION (provided by applicant): Mycobacterium avium is a major opportunistic pathogen in AIDS patients as well as a major cause of pulmonary infection in individuals with underlying lung disease. However, our understanding of M. avium pathogenesis is lacking due in part to limited information on M. avium components involved in modulating the host response. Nevertheless, previous studies suggest that glycopeptidolipids (GPLs), which are major surface components expressed on many non-tuberculosis mycobacteria, may function in directing the host response to an M. avium infection. We have found that GPLs can engage the pattern recognition receptor Toll-like receptor 2 (TLR2) leading to macrophage activation. Interestingly, we found that GPLs varied in their ability to interact with TLR2 and that slight changes in the GPL acetylation and methylation patterns determine whether this glycolipid can signal through TLR2. GPLs can also engage the mannose receptor and that this interaction is required for the delayed accusation of lysosomal markers observed for phagosomes containing GPL-coated beads. Based on these observations we hypothesize that M. avium can modify its GPL structure during the course of an infection and that this is an important virulence mechanism. Further, we predict that increased expression of certain GPL variants by M. avium will correlate with a strain's pathogenicity. To test these predictions we will: 1) Define the GPL structural components necessary for its binding to the MR and for its ability to delay phagosome maturation and the mechanism by which GPLs mediate this delay. 2) Characterize the GPL composition of M. avium strains following macrophage and mouse infections and define how the GPL composition correlates with strain virulence. 3) Generate M. avium knockout mutants for genes involved in GPL biosynthesis and evaluate the mutants for GPL-mediated activities including signaling through TLR2 and MR, biofilm formation and sliding motility and for virulence in a mouse infection model. Upon completion of these studies we will have a better understanding of M. avium pathogenesis and the role that GPLs play in this process and the information garnered may lead to the development of new diagnostic tools to evaluate M. avium virulence. PUBLIC HEALTH RELEVANCE: Mycobacterium avium is a major opportunistic pathogen in AIDS patients and a significant cause of morbidity and mortality in HIV infected individuals. It is also a common cause of pulmonary infections in individuals with underlying lung disease. The goal of this proposal is to better understand M. avium pathogenesis so as to develop new methods to limit M. avium infections and to treat those infected.