NOS2 and arginase in visceral leishmaniasis

描述（由申请人提供）：叙利亚仓鼠再现了人类感染多诺瓦利什曼原虫的两种主要形式。在全身性感染后，这些动物发展成一种模仿人类VL临床病理特征的进行性疾病。然而，皮肤感染的仓鼠局部控制感染，并获得对全身挑战的免疫力，类似于亚临床感染的个体对内脏疾病产生免疫力。这两个广泛的特征促使我们在这种独特的动物模型中开始研究多诺瓦氏乳杆菌感染的分子免疫发病机制。在初步研究中，我们发现在VL仓鼠模型的进行性疾病过程中，1型T细胞反应出现，但无效且伴有无法检测到的NOS2表达。此外，与小鼠巨噬细胞相比，ifn - γ激活的仓鼠巨噬细胞不能产生可检测到的NO，也不能控制细胞内感染。仓鼠和小鼠之间的这些差异为直接比较和对比巨噬细胞激活/失活的机制提供了动力，特别是nos2精氨酸酶代谢途径。我们将把体外研究结果扩展到仓鼠体内的原理验证研究，再次关注nos2 -精氨酸酶代谢途径在抵抗疾病和保护性免疫中的作用。我们将从两个相反但互补的方向探讨NOS2和精氨酸酶在L donovani感染中的作用。在Specific Aims 1和2中，我们将通过感染仓鼠和小鼠巨噬细胞的体外研究以及全身感染仓鼠的体内研究，确定NOS2和精氨酸酶表达在内脏感染发病机制中的作用。特异性目的1将验证仓鼠巨噬细胞控制多诺多氏杆菌感染的能力受损是NOS2对ifn - γ介导的激活反应低下的结果，并且这种NOS2反应低下是通过转录机制介导的。特异性目的2将验证一种假设，即在感染的仓鼠或人巨噬细胞中，NOS2表达受损为精氨酸酶主导的替代激活或失活途径奠定了基础，从而导致寄生虫杀伤能力受损。在特异性目标3中，我们将确定获得免疫后对原发性皮肤感染的控制和对继发性内脏攻击的保护是否通过低NOS2和高精氨酸酶表达的默认逆转来介导。我们假设不依赖nos2的机制有助于抵抗，我们将在发现仓鼠对原发和继发感染的抗性基因表达谱方面取得新的进展。这些在仓鼠身上的研究将通过定义与小鼠模型截然不同的疾病和免疫机制来填补知识空白。

DESCRIPTION (provided by the applicant): Syrian hamsters recapitulate the two major forms of infection with Leishmania donovani seen in man. After systemic infection, these animals develop a progressive disease that mimics the clinical-pathological features of human VL. However, hamsters infected in the skin control the infection locally, and acquire immunity to systemic challenge, akin to sub-clinically infected individuals who develop immunity against visceral disease. These two broad features prompted us to initiate studies to dissect the molecular immunopathogenesis of L. donovani infection in this unique animal model. In preliminary studies we found that during progressive disease in the hamster model of VL, a Type 1 T cell response is mounted, but is ineffective and accompanied by undetectable NOS2 expression. Furthermore, in contrast to mouse macrophages, IFN-gamma-activated hamster macrophages do not produce detectable NO and are unable to control intracellular infection. These distinctions between hamsters and mice provide the impetus to directly compare and contrast mechanisms of macrophage activation/deactivation in these species, with particular focus on the NOS2-arginase metabolic pathways. We will extend in vitro findings to in vivo proof-of-principle studies in the hamster, again with the focus on the role of the NOS2-arginase metabolic pathways in resistance to disease and protective immunity. We will approach the role of NOS2 and arginase in infection with L donovani from two opposite, but complementary directions. In Specific Aims 1 and 2 we will determine the role of NOS2 and arginase expression in the pathogenesis of visceral infection through in vitro studies of infected hamster and mouse macrophages, and in vivo studies of systemically infected hamsters. Specific Aim 1 will test the hypothesis that the impaired capacity of hamster macrophages to control L. donovani infection is a result of the hypo-responsiveness of NOS2 to IFN-gamma-mediated activation, and that this NOS2 hyporesponsiveness is mediated through transcriptional mechanism(s). Specific Aim 2 will test the hypothesis that the impaired NOS2 expression sets the stage for an arginase-dominated alternative activation or deactivation pathway in infected hamster or human macrophages, which leads to impaired parasite killing. In Specific Aim 3 we will determine if the control of primary cutaneous infection and protection against secondary visceral challenge following acquisition of immunity is mediated by a reversal of the default toward low NOS2 and high arginase expression. We hypothesize that NOS2-independent mechanisms contribute to resistance and we will break new ground in the discovery of a gene expression profile that characterizes resistance to primary and secondary infection in the hamster. These studies in the hamster will fill a knowledge gap by defining mechanisms of disease and immunity that are strikingly different from those of the murine model.