Immunity To Chlamydial Infection

对衣原体感染的免疫力

• 批准号: 6669561
• 负责人: HARLAN D CALDWELL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6669561
• 关键词: Chlamydia trachomatis; bacterial antigens; bacterial vaccines; bactericidal immunity; biotechnology; chlamydial disease; disease /disorder model; laboratory mouse; mucosal immunity; vaccine development

The purpose of this work is to define the immunological basis that mediates protective immunity against Chlamydia trachomatis infection of the female genital tract. The long-term goal is to then use this information to develop a safe and efficacious vaccine against chlamydial caused sexually transmitted diseases (STD. The project involves the study of immunity in a murine model of chlamydial infection of the female genital tract. The goal of the work is to identify mechanisms of protective immunity and protective antigens, information that then can used to formulate novel vaccines to test in this pre-clinical model. The long-range goal is to move the most promising of these vaccines to human clinical trials to assess their safety and efficacy in preventing chlamydial STDs. Past studies from this laboratory using gene knock out mice, adoptive transfer of immune T cells, and in vivo depletion of T cell subsets strongly implicate CD4+ Th1 cell mediated immunity as the major protective arm of the immune response against chlamydial genital infection. Conversely, CD8+ T cells, gamma/delta T cells, and antibodies play only a limited role in mediating protective immunity. We have continued studies along these lines to further define effector function(s) of CD4+ Th1 mediated immunity and lymphocyte homing to the genital mucosal. Our findings support a role for IFN-gamma but not TNF-alpha, iNOS, or Fas mediated apoptopic killing in protective anti-chlamydial mediated T cell immunity. The effector mechanims by which IFN-gamma functions is through the induction of indoleamine 2,3-dioxygnease (IDO) and subsequent starvation of chlamydiae by the deprivation host tryptophan. Thus, vaccines capable of generating a chlamydial specific type 1 CD4+ immune response at the genital mucosae are likely to elicit protective immunity. Lymphoctye homing studies implicate both systemic and mucosal integrins and their cognate receptors in lymphocyte homing to the genital mucosa. To date, vaccination using conventional approaches such as targeted chlamydial recombinant proteins or DNA encoding proteins delivered either systemically or locally with and without Th1 promoting adjuvants have failed in eliciting a protective Th1 immunity at the genital mucosae. Infection of the genital tract or immunization with ex vivo pulsed dendritic cells (DC? are the only highly efficacious ways of generating protective immunity against chlamydial genital re-challenge. Our conclusions are that the antigenic complexity of the chlamydiae, its complex life cycle, and tropism for mucosal epithelial cells constitute overwhelming challenges for the generation of a conventional vaccine. Consequently, we are currently focusing on the generation of live-attenuated vaccine strains. This is being accomplished by the clonal selection of variants that are incapable of synthesizing tryptophan synthase, a key enzyme in the ability of the pathogen to persist in epithelial cells in the presence host defense. We are selecting attenuated trp-/- strains by growth in trp deficient medium supplemented with 5 fluoroindole (5-FI). Organisms with mutations in the tryptophane synthase gene (trpRBA) will not incorporate 5-FI and will survive its lethal effect. 5-FI resistant clones will be characterized biologically for sensitivity to IFN-gamma in vitro, indole rescuablility, and trpRBA sequence analysis. Clones whose growth is highly sensitive to IFN-gamma in vitro and that have mutations in the trpRBA genes will be tested in in vivo models of infection for attenuated growth and pathological properties. Strains demonstrating attenuated in vitro growth for the murine female genital tract will then be tested for their ability to induce protective immunity against challenge infections with virulent chlamydiae. These studies should yield information important to the development of a highly efficacious and safe vaccine capable of preventing or controlling chlamydial caused STDs in humans.

这项工作的目的是确定介导针对女性生殖道沙眼衣原体感染的保护性免疫的免疫学基础。长期目标是利用这些信息开发一种安全有效的疫苗，预防衣原体引起的性传播疾病（STD）。该项目涉及女性生殖道衣原体感染的小鼠模型中的免疫研究。这项工作的目标是确定保护性免疫和保护性抗原的机制，这些信息随后可用于配制新疫苗，以在该临床前模型中进行测试。 长期目标是将这些疫苗中最有前途的疫苗进行人体临床试验，以评估其预防衣原体性传播疾病的安全性和有效性。该实验室过去使用基因敲除小鼠、免疫 T 细胞的过继转移以及 T 细胞亚群体内耗竭的研究强烈表明 CD4+ Th1 细胞介导的免疫是针对衣原体生殖器感染的免疫反应的主要保护臂。相反， CD8+ T 细胞、γ/δ T 细胞和抗体在介导保护性免疫方面仅发挥有限的作用。我们沿着这些思路继续研究，以进一步定义 CD4+ Th1 介导的免疫和淋巴细胞归巢到生殖器粘膜的效应器功能。我们的研究结果支持 IFN-γ 的作用，但不支持 TNF-α、iNOS 或 Fas 介导的细胞凋亡杀伤作用 保护性抗衣原体介导的 T 细胞免疫。 IFN-γ 发挥作用的效应机制是通过诱导吲哚胺 2,3-双氧酶 (IDO) 并随后通过剥夺宿主色氨酸来饥饿衣原体。因此，能够在生殖器粘膜产生衣原体特异性 1 型 CD4+ 免疫反应的疫苗可能会引发 保护性免疫力。淋巴细胞归巢研究表明全身和粘膜整合素及其同源受体在淋巴细胞归巢到生殖器粘膜中。迄今为止，使用常规方法进行疫苗接种，例如全身或局部递送靶向衣原体重组蛋白或 DNA 编码蛋白（含或不含 Th1 促进佐剂），未能引发保护性 Th1 生殖器粘膜的免疫力。生殖道感染或用离体脉冲树突状细胞（DC？）进行免疫是产生针对衣原体生殖器再次攻击的保护性免疫的唯一高效方法。我们的结论是，衣原体的抗原复杂性、其复杂的生命周期以及对粘膜上皮细胞的趋向性构成了压倒性的因素。 生产传统疫苗面临的挑战。因此，我们目前的重点是减毒活疫苗株的产生。这是通过克隆选择无法合成色氨酸合酶的变体来实现的，色氨酸合酶是病原体在存在宿主防御的情况下在上皮细胞中持续存在的能力的关键酶。我们通过在色氨酸缺陷中生长来选择减毒色氨酸-/-菌株 培养基补充有 5 氟吲哚 (5-FI)。色氨酸合酶基因 (trpRBA) 发生突变的生物体不会吸收 5-FI，因此不会受到其致命效应的影响。 5-FI 抗性克隆将在体外对 IFN-γ 敏感性、吲哚可挽救性和 trpRBA 序列分析方面进行生物学表征。体外生长对 IFN-γ 高度敏感的克隆 trpRBA 基因突变的小鼠将在体内感染模型中测试生长减弱和病理特性。然后，将测试小鼠雌性生殖道体外生长减弱的菌株诱导针对强毒衣原体攻击感染的保护性免疫的能力。这些研究应该提供对于开发能够预防或控制衣原体引起的高效且安全的疫苗非常重要的信息。 人类性病。