RECOGNITION OF MYCOBACTERIUM AVIUM COMPLEX BY HOST CELLS

这是一个继续研究的项目， 鸟分枝杆菌复合体（MAC）感染的初始事件。我们的工作取得 这一点导致了两个基本发现。首先，我们已经证明， MAC微生物通过纤连蛋白附着结合纤连蛋白（Fn 蛋白（FAP），并且这种结合对于有效侵入 上皮细胞，这可能是一个关键组成部分， 感染MAC。我们的第二个基本发现是， 上皮细胞浸润，MAC的FN调理作用不导致感染 巨噬细胞相反，巨噬细胞的侵袭依赖于补体 activation.特别是我们发现补体的一个片段 一种叫做C2 a的激活，通常是不活动的，可以与MAC一起工作 辅助因子切割巨噬细胞衍生的C3，从而提供识别 MAC巨噬细胞摄取信号。M.非常重要。 tuberculosis，M. leprae和M.牛BCG共享使用C2 a的能力， MAC侵入巨噬细胞，但快速生长的分枝杆菌如M. vaccae、牛痘M. smegalgae和M.草，不是细胞内病原体， 不要。这表明这种特性是一种保守的毒力因子 胞内致病分枝杆菌中。基于这些结果，我们 建议i）确定MAC与 感染中的上皮细胞;和ii）确定补体在MAC中的作用 体内感染。为了做到这一点，我们将使用各种生化和 细胞和分子生物学方法来了解FAP-Fn结合， 建立全身感染; FAP生物合成、分泌和 与MAC细胞壁的相互作用，抑制FAP- 通过整联蛋白α 4 β 1介导上皮细胞的侵袭，以及 表征激活补体C2 a的MAC糖脂。最后我们 将使用基因突变小鼠来确定补体的重要性， 用于体内感染。这些研究将建立在我们之前的工作基础上， 提供了MAC感染初始事件的非常完整的图片。 这些数据将有助于通过彻底评估潜在的 治疗干预的重要目标。

This is a project to continue studies which emphasize understanding of initial events in Mycobacterium avium complex (MAC) infection. Our work to this point has led to two fundamental discoveries. First, we have shown that MAC organisms bind fibronectin (Fn) via fibronectin attachment protein (FAP) and that this binding is essential for efficient invasion of epithelial cells, which is likely to be a critical component of initial infection by MAC. Our second fundamental discovery was that, unlike epithelial cell invasion, FN opsonization of MAC did not lead to infection of macrophages. Instead, macrophage invasion depended on complement activation. In particular we showed that a fragment of complement activation called C2a, normally inactive, could work together with a MAC co-factor to cleave macrophage-derived C3 and thus provide a recognition signal for macrophage uptake of MAC. It is very important that M. tuberculosis, M. leprae, and M. bovis BCG share the ability to use C2a to invade macrophages with MAC, but the fast growing mycobacteria such as M. vaccae, M. smegmatis and M. phlei, which are not intracellular pathogens, do not. This suggests that this property is a virulence factor conserved among intracellular pathogenic mycobacteria. Based on these results we propose to i) determine the significance of MAC interaction with epithelial cells in infection; and ii) establish role of complement in MAC infection in vivo. To do this, we will use a variety of biochemical and cell and molecular biologic approaches to understand FAP-Fn binding during establishment of systemic infection; FAP biosynthesis, secretion, and interaction with MAC cell wall, the mechanism of inhibition of FAP- mediated invasion of epithelial cells by integrin alpha4beta1, and to characterize the MAC glycolipid which activates complement C2a. Finally we will use genetically mutant mice to determine the importance of complement for in vivo infection. These studies will build on our previous work to provide a very complete picture of the initial events in MAC infection. These data will facilitate through a thorough evaluation of potentially important targets for therapeutic intervention.