RECOGNITION OF MYCOBACTERIUM AVIUM COMPLEX BY HOST CELLS

这是一个继续研究的项目，强调对 禽分枝杆菌复合体(MAC)感染的初始事件。我们的工作是 这一点导致了两个根本性的发现。首先，我们已经展示了 MAC生物通过纤维连接蛋白结合纤维连接蛋白(FN) 蛋白质(FAP)，这种结合是有效入侵的关键 上皮细胞，这很可能是初始阶段的关键组成部分 被MAC感染。我们的第二个基本发现是，与 MAC上皮细胞侵袭、FN调理未导致感染 巨噬细胞。相反，巨噬细胞的入侵依赖于补体。 激活。特别是，我们展示了补体的一段 被称为C2a的激活通常是不活动的，可以与MAC一起工作 辅助因子裂解巨噬细胞来源的C3，从而提供识别 巨噬细胞摄取MAC的信号。非常重要的是，M。 结核病、麻风杆菌和卡介苗分枝杆菌都有能力利用C2a来 用MAC侵入巨噬细胞，但快速生长的分枝杆菌如M。 维卡、耻垢分枝杆菌和草分枝杆菌，它们不是细胞内的病原体， 不要这样做。这表明这一特性是一种保守的毒力因子。 在胞内致病分枝杆菌中。基于这些结果，我们 建议i)确定MAC交互的重要性 上皮细胞在感染中的作用；以及ii)确定补体在MAC中的作用 体内感染。要做到这一点，我们将使用各种生化和 细胞和分子生物学方法了解FAP-FN结合 建立全身性感染；FAP的生物合成、分泌和 与MAC细胞壁的相互作用，抑制FAP-2的机制。 整合素α4β1介导的上皮细胞侵袭 描述激活补体C2a的MAC糖脂。最后我们 将使用基因突变的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以前工作的基础上 提供有关MAC感染的初始事件的非常完整的图景。 这些数据将有助于通过对潜在的 治疗干预的重要靶点。

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.