Role of human innate immune mutations in loss of tolerance to Borrelia burgdorferi

莱姆病的大多数症状是由于宿主对疏螺旋体的免疫反应。 甚至在没有抗生素治疗的情况下，也会随着时间的推移而消退。在其自然宿主中，很少或没有反应 尽管生物体终生存活，但仍然可以看到感染。在人类和近亲交配的小鼠身上(这是 对生物体产生免疫反应)，炎症被认为是由先天受体启动的 免疫系统。在体外，识别伯氏杆菌的固有病原体感知受体的丧失，如Toll- 类受体2(TLR2)导致炎症反应减少。然而，对动物的活体研究 缺乏这些受体或其适配器分子并不能减轻炎症，而且在许多情况下 显示炎症增加。最近，在人类中，TLR1基因的单核苷酸多态性(SNP) 这导致细胞表面受体表达的丧失与增加有关 炎症和症状。这表明，在最初的刺激之后，这些先天免疫的主要作用 分子具有抑制炎症的作用。体外研究和体内研究的一个主要区别是 感染是体外实验通常通过测量几分钟到几小时的反应来进行的 在接触到这种有机体之后。我们有证据表明，更长时间的体外暴露会导致 对伯氏杆菌刺激的天然免疫“耐受性”的形成。 在这个方案中，我们将研究TLR1-1805GG SNP在扰乱先天性免疫耐受中的作用， 从而导致过度的炎症反应。1805GG SNP导致本地化损失到 但不影响受体的活性。因此，在目标1中，我们将首先确定 SNP对特异性、定位依赖性信号通路及下游细胞因子的影响 回应。我们之前已经证明，TLR1/TLR2配体Pam3CSK4可以启动来自 细胞内和细胞表面的位置，尽管每个位置的信号不同。很可能TLR1- 1805GG SNP继续在内脏发出信号。我们还将跟踪受体和配体的运动。 将TLR1缺失与TLR1-1805GG SNP进行比较。在目标2中，我们将评估TLR1-1805GG SNP的作用 巨噬细胞重编程导致对伯氏杆菌先天免疫耐受丧失的研究。我们将重点关注 了解其对巨噬细胞极化、细胞死亡和糖代谢作用的影响。最后，在 目的3，使用启动或不启动耐受性的伯氏杆菌同基因分离株，我们将确定 机体在调节巨噬细胞重新编程和耐受性丧失方面的特定成分。 我们认为，伯氏杆菌感染，在有最少证据的情况下存在长期感染 随着时间的推移，炎症是一个很好的模型来理解免疫系统如何控制对 侵袭性细菌对健康的威胁比持续努力清除感染更小-本质上 通过先天免疫耐受的发展，使生物体成为侵入性的“共生体”。

The majority of symptoms of Lyme disease are due to the host immune response to the organism, Borrelia burgdorferi, and resolve over time, even without antibiotic treatment. In its natural host, little or no reaction to infection can be seen despite the fact that the organism persists for life. In humans and inbred mice (which do develop immune responses to the organism), inflammation is thought to be initiated by receptors of the innate immune system. In vitro, loss of innate, pathogen-sensing receptors that recognize B. burgdorferi such as toll- like receptor 2 (TLR2) results in a decrease inflammatory response. However, in vivo studies of animals deficient in these receptors or their adaptor molecules do not show reduced inflammation and in many cases show increased inflammation. Recently, in humans, a single nucleotide polymorphism (SNP) in the tlr1 gene that results in loss of expression of the receptor on the cell surface was found to be associated with increased inflammation and symptoms. This suggests that after the initial stimulus, a major role for these innate immune molecules is in dampening inflammation. One major difference between in vitro studies and the in vivo infections is that the in vitro experiments are typically conducted by measuring responses minutes to hours after exposure to the organism. We have evidence that more prolonged exposures in vitro result in the development of innate immune “tolerance” to stimulation by B. burgdorferi. In this proposal, we will study the role of the tlr1-1805GG SNP in disrupting innate immune tolerance, thereby leading to excessive inflammatory responses. The 1805GG SNP results in a loss of localization to the cell surface but does not affect the activity of the receptor. Therefore, in Aim 1, we will first determine the effects of the SNP on specific, localization-dependent signaling pathways and downstream cytokine responses. We have previously shown that the TLR1/TLR2 ligand Pam3CSK4 can initiate signaling from both intracellular and cell surface locations although the signals are different in each location. It is likely that the tlr1- 1805GG SNP continues to signal endosomally. We will track movements of the receptors and ligands as well as compare a tlr1 deletion to the tlr1-1805GG SNP. In Aim 2, we will assess the role of the tlr1-1805GG SNP on macrophage reprogramming leading to loss of innate immune tolerance to B. burgdorferi. We will focus on understanding its effects on macrophage polarization, cell death and the role of glucose metabolism. Finally, in Aim 3, using isogenic B. burgdorferi isolates that do or do not initiate tolerance, we will identify the role of specific components of the organism in moderating macrophage reprograming and loss of tolerance. We believe that B. burgdorferi infection, where there is prolonged infection with minimal evidence of inflammation over time, is an excellent model to understand how the immune system can control responses to invasive bacteria that pose less threat to health than continued efforts to clear the infection—in essence making the organism an invasive “commensal” through the development of innate immune tolerance.