M. avium GPLs in Macrophage Activation and Virulence

描述(申请人提供)：鸟分枝杆菌是艾滋病患者的主要机会致病菌，也是潜在肺部疾病患者肺部感染的主要原因。然而，我们对鸟型支原体的致病机制缺乏了解，部分原因是关于参与调节宿主反应的禽型支原体成分的信息有限。然而，先前的研究表明，糖肽脂(GPLs)是许多非结核分枝杆菌上表达的主要表面成分，可能在指导宿主对禽类分支杆菌感染的反应中发挥作用。我们发现GPLs可以与模式识别受体Toll样受体2(TLR2)结合，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微小变化决定了这种糖脂是否可以通过TLR2发出信号。GPL也可以与甘露糖受体结合，这种相互作用是对含有GPL包被珠的吞噬小体观察到的溶酶体标志物的延迟指控所必需的。基于这些观察结果，我们推测，在感染过程中，鸟型支原体可以改变其GPL结构，这是一种重要的毒力机制。此外，我们预测，某些GPL变异体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)确定GPL与MR结合所必需的结构成分，以及它延迟吞噬小体成熟的能力，以及GPL介导这种延迟的机制。2)确定巨噬细胞和小鼠感染后禽类支原体菌株的GPL组成，并确定GPL组成与菌株毒力之间的关系。3)建立GPL生物合成相关基因的敲除突变株，并在小鼠感染模型中评价GPL介导的活性，包括通过TLR2和MR的信号、生物膜的形成和滑动运动以及毒力。在这些研究完成后，我们将更好地了解禽类分枝杆菌的致病机理和GPLs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禽类分枝杆菌的毒力。 公共卫生相关性：禽分枝杆菌是艾滋病患者的主要机会性病原体，也是艾滋病毒感染者发病和死亡的重要原因。它也是肺部感染的常见原因，在有潜在肺部疾病的人中。这项建议的目的是为了更好地了解禽类分枝杆菌的发病机制，以便开发新的方法来限制禽类分枝杆菌感染和治疗那些感染的人。

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.