Nicotine & Immunopathogenesis of Cryptococcal meningitis

描述(申请人提供)：机会性中枢神经系统感染是获得性免疫缺陷综合症(AIDS)患者常见的并发症。新生隐球菌(CNE)是一种被包裹的酵母，通常会导致7%-30%的艾滋病患者患上致命的隐球菌性脑膜脑炎(CM)。虽然高效抗逆转录病毒疗法成功地降低了许多机会性感染的发生率，但在降低晚期艾滋病患者机会性真菌感染的发生率方面效果较差。宿主对CNE的反应是先天免疫和获得性免疫之间复杂的相互作用。在动物模型中，无法增加大脑促炎细胞因子的水平或促进白细胞迁移到大脑中通常与致死性CM有关。因此，需要“促炎”反应来遏制中枢神经系统中的CNE感染。流行病学研究表明，吸烟是隐球菌病和其他机会性真菌感染的重要危险因素，85%的患有隐球菌病的艾滋病患者吸烟。然而，吸烟影响CNE发病的机制还完全不清楚。我们已经证明，香烟烟雾会抑制免疫系统，而尼古丁(NT)是香烟烟雾中导致T细胞无能和抑制炎症反应的主要免疫抑制成分。我们的初步研究表明，慢性NT治疗抑制了趋化/趋化和白细胞向炎症部位的迁移，减少了对松节油和CNE等炎性刺激的反应，减少了脑IL-1β的表达，促进了CNE的生长和早期扩散。因此，我们假设香烟烟雾/NT调节CNE的先天和获得性免疫反应，从而促进其扩散到大脑和发育中的CM。为了验证这一假说，并探讨NT促进CNE脑感染的机制(S)，我们开展了以下研究：1.研究NT对CNE诱导的先天免疫的影响，包括脑组织促炎细胞因子/趋化因子的表达和白细胞对CNE影响的细胞因子/趋化因子的反应，建立CNE和白细胞向脑内迁移的动力学以及CM的发生发展，并观察NT对CNE诱导的发热反应的影响。2.研究CNE对小鼠适应性免疫反应的影响，包括产生抗CNE抗体、对隐球菌抗原的增殖型和迟发型超敏反应、产生针对CNE蛋白免疫优势表位的细胞毒性T细胞，以及评价CNE感染后迁移到脑内的T细胞的保护功能。3.探讨NT抑制白细胞向感染部位迁移的机制。我们相信，这些研究将阐明吸烟/NT促进CNE和其他真菌感染进入艾滋病患者大脑的机制(S)，并确定治疗CM的潜在靶点。

DESCRIPTION (provided by applicant): Opportunistic infections of the central nervous system are common complication in acquired immunodeficiency syndrome (AIDS) patients. Cryptococcus neoformans (Cne) is an encapsulated yeast that causes often fatal cryptococcal meningoencephalitis (CM) in 7-30% of AIDS patients. While highly active anti-retroviral therapy has successfully decreased the incidence of many opportunistic infections, it is less effective in decreasing the incidence of opportunistic fungal infections in advanced AIDS patients. The host's response to Cne is a complex interplay between the innate and adaptive immunities. In animal models, the inability to increase the brain levels of proinflammatory cytokines or promote leukocyte migration into the brain is typically associated with lethal CM. Thus, "proinflammatory" responses are required to contain Cne infection in the central nervous system. Epidemiological studies show that cigarette smoking is a significant risk factor in cryptococcosis and other opportunistic fungal infections, and >85% of AIDS patients with cryptococcosis are cigarette smokers. However, the mechanism by which smoking affects the pathogenesis of Cne is totally unknown. We have demonstrated that cigarette smoke suppresses the immune system, and nicotine (NT) is a major immunosuppressive component of cigarette smoke that causes T cell anergy and inhibits the inflammatory responses. Our preliminary studies suggest that chronic NT treatment inhibits chemokinesis/chemotaxis and the migration of leukocytes to the site of inflammation, decreases brain IL-1beta expression in response to an inflammatory stimuli such as turpentine and Cne, and promotes growth and early dissemination of Cne into the brain. Therefore, we hypothesize that cigarette smoke/NT modulates both the innate and adaptive immune responses to Cne, thus facilitating its dissemination to the brain and the development CM. To test this hypothesis and to identify mechanism(s) by which NT facilitates brain infection by Cne, the following studies are proposed: 1. To investigate the effects of NT on Cne-induced innate immunity, including the expression of proinflammatory cytokines/chemokines in the brain and the response of leukocytes to cytokines/chemokines that are affected by Cne, to establish the kinetics of Cne and leukocyte migration into the brain and the development of CM, and to examine the effects of NT on the Cne-induced fever response. 2. To ascertain the effects on the adaptive immune responses including generation of anti-Cne antibodies, proliferative and delayed-type hypersensitivity responses to cryptococcal antigens, and generation of cytotoxic T cells to immunodominant epitopes of Cne proteins, as well as to evaluate the protective function of T cells that migrate into the brain after Cne infection. 3. To investigate the mechanisms by which NT suppresses the migration of leukocytes toward the site of infection. These studies, we believe, will delineate the mechanism(s) by which smoking/NT encourages dissemination of Cne and, perhaps, other fungal infections into the brain of AIDS patients, and identify potential therapeutic targets for treatment of CM.