CD180 and the Macrophage Response to Legionella pneumophila

嗜肺军团菌（Legionella pneumophila, Lp）是一种革兰氏阴性的细胞内细菌，可感染人肺泡巨噬细胞并引起军团病（Legionnaire's Disease， LD）。CD180 （RP105）是TLR家族的非信号成员，调节TLR2和TLR4功能，在军团菌发病机制中的作用尚不清楚。我们假设CD180调节小鼠和人类对Lp感染的易感性。我们用Lp感染骨髓源性巨噬细胞，发现在野生型和鞭毛蛋白缺失型Lp菌株的MOIs范围内，CD180-/-小鼠的复制明显高于C57BL/6对照组。CD180-/-巨噬细胞中Lp复制的增强与关键先天免疫细胞因子（如IL-1、IL-6或TNF）的释放无关。通过对1999年荷兰军团病暴发个体的病例对照研究，我们发现CD180单核苷酸多态性与LD保护显著相关（OD值0.27-0.50）。其中一种多态性与单核细胞中CD180的表达减少有关。在这项应用中，我们建议研究cd180依赖性宿主对小鼠Lp感染抗性的体外机制。此外，我们将研究CD180的人类变体及其在调节单核细胞和巨噬细胞对Lp感染的反应中的作用。我们将研究CD180功能的改变，通过人类的多态性或小鼠的靶向基因缺失，是否会在分子和细胞水平上改变宿主对鞭毛细胞内细菌的反应。CD180缺乏的个体提供了一个独特的机会来研究人类CD180变异的体外和体内影响，并且与CD180-/-小鼠一起，将使我们能够检查CD180在Lp先天免疫应答中的作用。从这些研究中获得的免疫遗传学模型将阐明宿主对Lp和可能的其他细胞内细菌引起的疾病的易感性机制，并最终为未来的治疗提供新的见解。

DESCRIPTION (provided by applicant): CD180 and the Macrophage Response to Legionella neumophila Legionella pneumophila (Lp) is a gram-negative intracellular bacterium that infects human alveolar macrophages and causes a pneumonic illness known as Legionnaire's Disease (LD). The role of CD180 (RP105), a non-signaling member of the TLR family that regulates TLR2 and TLR4 function, in Legionella pathogenesis is unknown. We hypothesized that CD180 regulates susceptibility to Lp infection in mice and humans. We infected bone-marrow derived macrophages with Lp and observed significantly greater replication in CD180-/- mice compared to C57BL/6 controls over a range of MOIs in both wildtype and flagellin-deficient Lp strains. The enhanced replication of Lp in CD180-/- macrophages was not associated with release of key innate immune cytokines, such as IL-1¿, IL-6, or TNF. Using a case-control study of individuals from a 1999 outbreak of Legionnaire's Disease in the Netherlands, we found CD180 single nucleotide polymorphisms that were significantly associated with protection from LD (OD 0.27-0.50). One of these polymorphisms was associated with decreased expression of CD180 in monocytes. In this application, we propose to examine the in vitro mechanisms underlying CD180-dependent host resistance to Lp infection in mice. In addition, we will examine human variants of CD180 and their role in regulating monocyte and macrophage responses to Lp infection. We will examine whether alteration of CD180 function, via polymorphisms in humans or targeted gene deletion in mice, changes the host response to a flagellated, intracellular bacteria at the molecular and cellular level. Individuals with CD180 deficiency provide a unique opportunity to study the in vitro and in vivo effects of human CD180 variation and, along with CD180-/- mice, will enable us to examine the role of CD180 in the innate immune response to Lp. The immunogenetic models derived from these studies will illuminate mechanisms of host susceptibility to diseases caused by Lp and possibly other intracellular bacteria and culminate in novel insights for future therapies.