IL 12 RESPONSIVENESS DURING L AMAZONENSIS INFECTION

亚马逊线虫感染期间的 IL 12 反应

• 批准号: 6626390
• 负责人: Douglas E Jones
• 金额: $ 24.91万
• 依托单位: IOWA STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-01-15 至 2004-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6626390
• 关键词: CD4 molecule; Leishmania; Leishmania major; RNase protection assay; antibody receptor; cellular immunity; centrifugation; dendritic cells; disease /disorder proneness /risk; enzyme linked immunosorbent assay; flow cytometry; helper T lymphocyte; host organism interaction; immunoregulation; interleukin 12; laboratory mouse; leishmaniasis; leukocyte activation /transformation; pathologic process; receptor expression; tissue /cell culture

The immune response to chronic leishmaniasis in humans is not well understood. These clinical diseases are not easily classified as polarized T helper 1(Th1) or Th2 immune responses. In contrast, murine infection with Leishmania major has been extensively studied as an in vivo model of Th1 or Th2 development. This proposal is based on the finding that CH3 and C57BL/6 mice are resistant to infection with the parasite Leishmania major but they are susceptible to infection with the related parasite L. amazonensis. This susceptibility is manifested by a single persistent non-healing cutaneous lesion, which is accompanied by a poor cellular immune response. We feel that the chronic L. amazonensis infection in these mice may more accurately reflect the immune response seen in chronic leishmaniasis of humans. The differences in the immune response to these two related parasites provide an excellent opportunity to study factors critical to host resistance and susceptibility, while eliminating host genetics as a variable. Resistance to L. major is is mediated by the development of a CD4+ Th 1 response, which is initiated by the cytokines IL-12 and IFN-g. The preliminary data demonstrates t during L. amazonensis infection endogenous IL-12 is reduced, the IL-12 receptor (IL-12R) is decreased on CD4+ T cells and the lymph node cell population is unresponsive to IL-12. The absence of these mediators of Th1 development correlate with a remarkable finding that exogenous IL-12 is unable to promote an effective Th1, cell-mediated, immune response towards L. amazonensis. Our hypothesis is that a Th1 response would resolve L. amazonensis infection and that the L. amazonensis prevents cell-mediated immunity by inhibiting IL-12 responsiveness. The experiments in this proposal will determine if the loss of functional IL-12R expression on the CD4+ T cell population and loss of IL-12 responsiveness of these cells is a primary factor in the development of a chronic infection. Since IL-4KO mice are also resistant to the Th1 promoting effects of exogenous IL-12 after L. amazonensis infection, experiments are proposed to determine if regulation of the IL-12R in vivo is independent of IL-4 and influenced by endogenous TGF-b. An active role of the parasites for the suppression of the Th1 response will be tested by the elimination of the parasites in vivo and it will be determined if there is a differential regulation of the CD4+ T cell population with the different stages of the infectious parasite. In addition, the T cell response will be characterized and it will be determined if differences in costimulation can modify the expression of the IL-12R and regulate IL-12 responsiveness on the antigen specific T cell population. Potential defects in T cell cytokine production and proliferation will also be assessed. Since dendritic cells become activated after L. major infection, the dendritic cell response to L. amazonensis will also be examined. L. amazonensis infected dendritic cells will be assessed for activation, IL-12 production, and their ability to promote T cell proliferation and regulation of the IL-12R. The efforts of this proposal will have direct application to the development of more effective immunomodulatory regimes for Leishmania and other infectious diseases.

人类对慢性利什曼病的免疫反应尚不清楚。 这些临床疾病不容易被分类为极化T辅助器1（TH1）或TH2免疫反应。相比之下，用利什曼原虫大调的鼠类感染已被广泛研究为Th1或Th2发育的体内模型。该提议是基于以下发现：CH3和C57BL/6小鼠抗寄生虫Leishmania Major具有抗性，但它们容易感染相关的寄生虫L. amazonensis。 这种敏感性由单个持续的非愈合皮肤病变表现出来，该病变伴随着细胞免疫反应不良。 我们认为，这些小鼠的慢性亚马逊感染可能会更准确地反映人类慢性利什曼病的免疫反应。 对这两个相关寄生虫的免疫反应的差异为研究对宿主抗药性和敏感性至关重要的因素提供了一个绝佳的机会，同时消除了宿主遗传学作为变量。 CD4+ Th 1响应的发展介导了对L. Major的抗性，CD4+ Th 1响应是由细胞因子IL-12和IFN-G引发的。 初步数据表明，在亚马逊乳杆菌感染内源性IL-12期间的T减少，CD4+ T细胞上IL-12受体（IL-12R）降低，淋巴结细胞群对IL-12不反应。 这些TH1发育的这些介体的缺乏与一个非凡的发现，即外源IL-12无法促进对亚马逊乳杆菌的有效TH1，细胞介导的免疫反应。 我们的假设是，TH1反应可以解决亚马逊乳杆菌的感染，而亚马逊乳杆菌通过抑制IL-12反应性来阻止细胞介导的免疫力。 该提案中的实验将确定CD4+ T细胞群体功能性IL-12R表达的丧失以及这些细胞IL-12反应性的丧失是慢性感染发展的主要因素。由于IL-4KO小鼠在亚马逊乳杆菌感染后也对促进外源IL-12的Th1促进作用有抵抗力，因此提出了实验以确定体内IL-12R的调节是否独立于IL-4并受内源性TGF-B的影响。 寄生虫在抑制Th1反应中的积极作用将通过消除体内的寄生虫进行测试，如果对CD4+ T细胞种群有差异调节，其感染性寄生虫的阶段不同。 此外，将表征T细胞反应，并确定共刺激的差异是否可以改变IL-12R的表达并调节对抗原特异性T细胞群的IL-12响应性。 T细胞细胞因子产生和增殖的潜在缺陷也将得到评估。 由于树突状细胞在主要感染后被激活，因此还将检查树突状细胞对亚马逊乳杆菌的反应。将评估亚马逊菌感染的树突状细胞的激活，IL-12产生以及它们促进T细胞增殖和调节IL-12R的能力。 该提案的努力将直接应用于利什曼尼亚和其他传染病的更有效的免疫调节制度。