NOS2 and arginase in visceral leishmaniasis

描述(由申请人提供)：叙利亚仓鼠概括了在人类中发现的两种主要形式的杜氏利什曼原虫感染。在系统感染后，这些动物会发展成一种类似于人类VL的临床病理特征的进行性疾病。然而，在皮肤感染的仓鼠局部控制感染，并获得对系统性挑战的免疫力，类似于亚临床感染的人对内脏疾病产生免疫力。这两个广泛的特征促使我们开始研究在这个独特的动物模型中感染多诺瓦氏杆菌的分子免疫发病机制。在初步研究中，我们发现在VL的仓鼠模型中，在进行性疾病期间，1型T细胞反应被启动，但无效，并伴随着不可检测到的NOS2表达。此外，与小鼠巨噬细胞相比，干扰素-γ激活的仓鼠巨噬细胞不产生可检测到的NO，也无法控制细胞内感染。仓鼠和小鼠之间的这些差异为直接比较和对比这些物种中巨噬细胞激活/失活的机制提供了动力，尤其是对NOS2-精氨酸酶代谢途径的关注。我们将把体外研究结果扩展到仓鼠体内的原理验证研究，重点再次放在NOS2-精氨酸酶代谢途径在抗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来探讨NOS2和精氨酸酶在L多诺瓦尼感染中的作用。在特定的目标1和2中，我们将通过对感染的仓鼠和小鼠巨噬细胞的体外研究以及对系统感染的仓鼠的体内研究来确定NOS2和精氨酸酶的表达在内脏感染发病机制中的作用。具体目的1将检验一种假设，即仓鼠巨噬细胞控制杜诺瓦氏杆菌感染的能力受损是由于NOS2对干扰素-γ介导的激活的低反应性，并且这种NOS2的低反应性是通过转录机制介导的(S)。特定目标2将测试假设，即受损的NOS2表达为感染的仓鼠或人类巨噬细胞中精氨酸酶主导的替代激活或失活途径奠定了基础，这将导致寄生虫被削弱的杀灭。在特定的目标3中，我们将确定在获得免疫后控制原发皮肤感染和抵抗继发内脏攻击的保护是否通过逆转默认的低NOS2和高精氨酸酶表达而介导。我们假设NOS2非依赖的机制有助于抗药性，我们将在发现表征仓鼠对原发和继发感染的抗药性的基因表达谱方面开辟新的天地。在仓鼠身上进行的这些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.