Innate and adaptive immune responses to Leishmania

描述(由申请人提供)：本提案旨在测试这样一种假设，即细胞内的原生动物利什曼原虫能够操纵宿主的先天免疫反应和获得性免疫反应，从而对它们有利。我们认为，前鞭毛体之所以具有传染性，是因为它们逃避先天免疫反应。我们还提出无鞭毛体具有传染性，因为它们利用适应性免疫反应。该提案的第一个目标将检查利什曼原虫前鞭毛体的先天免疫激活。这一目标是建立在观察到利什曼原虫感染白细胞的过程中无法诱导细胞因子和共刺激分子的产生的基础上的。这导致我们假设利什曼原虫前鞭毛体不能与TLRs相互作用，因此无法在巨噬细胞和树突状细胞中转移核因子-kappaB。我们将在目标1中提出的主要问题是，这种静止的进入机制是否是寄生虫毒力的关键组成部分。为了解决这个问题，我们开发了转基因利什曼原虫，在它们的表面表达TLR激活剂。我们将测量这些转基因生物在小鼠和细胞培养中的传染性。这一建议的第二个目的是基于我们的观察结果，即缺乏重链免疫球蛋白G的小鼠(JH小鼠)尽管是BALB/c背景，但对主要乳杆菌感染具有抵抗力。我们还观察到，给这些小鼠添加抗利什曼原虫抗体后，它们又恢复了对主要利什曼原虫感染的敏感性。在这项提议的第二个目标中，我们计划确定免疫球蛋白如何作用于感染细胞内病原体的宿主。我们将确定IL-10在这一过程中的作用，特别是APC衍生的IL-10作为免疫球蛋白诱导的允许因子的作用。这些研究直接与利什曼原虫感染的发病机制有关。它们还可能提供关于抗体在细胞内感染过程中的作用以及关于APC影响适应性免疫反应性质的能力的重要基本信息。

DESCRIPTION (provided by the applicant): This proposal seeks to test the hypothesis that the intracellular protozoan, Leishmania spp., is able to manipulate both the innate and the adaptive immune response of the host to their advantage. We propose that promastigotes are infectious because they evade the innate immune response. We also propose that amastigotes are infectious because they exploit the adaptive immune response. The first aim of the proposal will examine innate immune activation by Leishmania promastigotes. This aim is built on the observation that Leishmania promastigotes infect leukocytes by a process that fails to induce the production of cytokines and co-stimulatory molecules. This led us to hypothesize that Leishmania promastigotes fail to interact with TLRs, and as a consequence fail to translocate NF-kappaB in macrophages and dendritic cells. The main question that we will ask in Aim 1 is whether this quiescent mechanism of entry is a critical component of parasite virulence. To address this question, we have developed transgenic Leishmania parasites that express TLR activators on their surface. We will measure the infectivity of these transgenic organisms in mice and in cell cultures. The second aim of this proposal is based on our observation that mice lacking the heavy chain of IgG (JH mice) are resistant to L. major infections despite being on a BALB/c background. We have also observed that the addition of anti-Leishmania IgG to these mice reverts them back to being susceptible to L. major infections. In the second aim of this proposal, we plan to determine how IgG can work to the detriment of the host infected with an intracellular pathogen. We will determine the role of IL-10 in this process, and specifically the role of APC-derived IL-10 as an IgG-induced permissive factor. These studies pertain directly to the pathogenesis of Leishmania infection. They may also provide important basic information about the role of antibody during infections with intracellulars, and about the ability of APCs to influence the nature of an adaptive immune response.