Masters of immunology- how Toxoplasma gondii directly manipulates T cell activation

项目总结 免疫记忆是我们的免疫系统以更强大和更快的速度做出反应的能力 当再次遇到相同的病原体(即二次感染)时。免疫记忆是 疫苗接种仍然是预防传染病最成功的方法。然而，一个完全保护性的 到目前为止，还没有实现预防任何人类寄生虫病的疫苗。为什么绝育免疫力对 寄生病原体这么难做到？我们之前关于心尖复合体继发感染的工作 弓形虫寄生虫表明，寄生毒力因子是逃避适应性免疫的关键 回应。而抗原变异是非洲等原生动物病原体 锥虫、疟原虫和贾第鞭毛虫逃避B细胞介导的抗体反应，关于 操纵T细胞反应的毒力因子。鉴于CD8 T细胞介导的免疫应答的核心作用 各种原生动物病原体，包括弓形虫，这项建议旨在发现寄生毒力 影响CD8 T细胞反应的因素。在这里，我们报告弓形虫分泌效应器，ROP5和a 我们命名的第二个决定因素是‘ROCTR’(CD8 T细胞反应的调节因子)，它能抑制弓形虫的特异性 CD8T细胞对寄生虫感染细胞的反应。ROP5是一个多基因可变的假蛋白激酶家族，它是 注射到它入侵的宿主细胞中。在入侵后，弓形虫形成一个寄生液泡(PV)，使其 在体内复制。ROP5定位于光伏膜(PVM)的胞液一侧，保护其免受破坏 通过宿主干扰素γ诱导的免疫相关GTP酶(IRGS)。进入MHC1抗原的蛋白质 提呈途径主要来源于被宿主蛋白酶体降解的胞浆蛋白。 Apicomplexan寄生虫将自己隔离在一个非融合性PV中，主要缺乏宿主蛋白。多么 免疫系统是否获得了不在常规内吞细胞内的空泡抗原？ 牢房的隔间？我们的中心假设是弓形虫ROP5和IRG与MHC1相交 抗原提呈途径，而弓形虫ROCTR可能调节这一过程。然而，身份T。 弓形虫ROCTR和调节CD8 T细胞激活的宿主IRGS尚不清楚。这项建议旨在 确定这些因素。通过分析拥有单一T细胞受体的T57小鼠的CD8 T细胞 针对弓形虫TGD05796-103/KB抗原复合体，发现T57T细胞能分泌干扰素γ。 对弓形虫感染的巨噬细胞的反应具有菌株依赖性。使用最新的方法 基因组工程和寄生虫遗传学，我们将阐明弓形虫和寄生虫免疫逃避的机制。 确定空泡病原体的MHC1抗原呈递的宿主要求。通过细心 解剖，弓形虫甲壳上的下巴可能被揭示，并为疫苗设计提供洞察力 顶端复合体病原体。

PROJECT SUMMARY Immunological memory is the ability of our immune system to respond with greater strength and quickness upon re-encounter with the same pathogen (i.e. secondary infection). Immunological memory is the basis for vaccination which remains the most successful method for preventing infectious disease. Yet, a fully protective vaccine to prevent any human parasitic disease has not been realized to date. Why is sterilizing immunity to parasitic pathogens so difficulty to achieve? Our previous work on secondary infections with the apicomplexan parasite, Toxoplasma gondii, suggests that parasitic virulence factors are the key to evading adaptive immune responses. Whereas antigenic variation is a major mechanism by which protozoan pathogens such as African Trypanosomes, Plasmodium and Giardia evade B cell-mediated antibody responses, little is known regarding virulence factors that manipulate T cell responses. Given the central role of CD8 T cell-mediated immunity to a wide variety of protozoan pathogens, including T. gondii, this proposal aims to discover parasitic virulence factors that manipulate CD8 T cell responses. Here we report that T. gondii secreted effectors, ROP5 and a second determinant we name ‘ROCTR’ (Regulator Of CD8 T Cell Responses), work to inhibit T. gondii-specific CD8 T cell responses to parasite-infected cells. ROP5 is a multigene variable family of pseudokinases that are injected into the host cell it invades. Following invasion, T. gondii forms a parasitophorous vacuole (PV) that it replicates within. ROP5 localizes to the cytosolic side of the PV membrane (PVM) protecting it from destruction by the host’s IFNγ-induced Immunity Related GTPases (IRGs). Proteins that enter the MHC1 antigen presentation pathway are mainly derived from cytosolic proteins that are degraded by the host’s proteasome. Apicomplexan parasites sequester themselves in a non-fusogenic PV, mostly devoid of host proteins. How does the immune system gain access to vacuolar antigens that are not within conventional endocytic compartments of the cell? Our central hypothesis is that T. gondii ROP5 and an IRG intersect the MHC1 antigen presentation pathway, and that T. gondii ROCTR may regulate this process. However, the identities T. gondii ROCTR and the host IRGs that regulate CD8 T cell activation are unknown. This proposal aims to identify these factors. By analyzing CD8 T cells from T57 mice, which possess a single T cell receptor specificity for the T. gondii TGD05796-103 / Kb antigen complex, T57 T cells were found to secrete IFNγ in response to T. gondii-infected macrophages in a strain dependent manner. Using the latest approaches in genome engineering and parasite genetics, we will elucidate mechanisms of immune evasion by T. gondii and determine host requirements for MHC1 antigen presentation of vacuolated pathogens. Through careful dissection, a ‘chink in the armor’ of T. gondii may be revealed, and give insight into vaccine design for apicomplexan pathogens.