Cooperation of CD8+ T cells and phagocytes to eliminate Toxoplasma cysts

CD8 T细胞和吞噬细胞合作消除弓形虫包囊

基本信息

批准号：
10162486
负责人：
YASUHIRO SUZUKI
金额：
$ 45.9万
依托单位：
UNIVERSITY OF KENTUCKY
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-01-01 至 2024-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10162486
关键词：
Acquired Immunodeficiency Syndrome Acute Address Amino Acids Antigens Brain CD28 gene CD8 Antigens CD8-Positive T-Lymphocytes CD86 gene CD8B1 gene CXCL10 gene CXCR3 gene Cell surface Cells Chronic Combined Vaccines Cyst Cytoplasmic Granules Disease Epitopes Excision Funding HLA-A2 Antigen Histocompatibility Antigens Class I Human Immune Immune Evasion Immunity Immunize Immunocompromised Host Immunologics Individual Interleukin-2 Knockout Mice Life Ligands MHC Class I Genes Mediating Messenger RNA Methods Microglia Molecular Mouse Strains Mus N-terminal Parasites Patients Phagocytes Phagocytosis Phagolysosome Pharmaceutical Preparations Play Population Process Proteins Role System T-Lymphocyte Tissues Toxoplasma Toxoplasma gondii Toxoplasmosis Transgenic Mice Tumor stage Vaccines base chemokine chronic infection design immunological intervention immunosuppressed improved macrophage mouse model novel pathogen perforin prevent rab GTP-Binding Proteins recruit rhoptry toxoplasmic encephalitis vaccine development

项目摘要

Chronic infection with Toxoplasma gondii can reactivate and cause life-threatening toxoplasmic encephalitis in AIDS patients and other immunocompromised individuals. The basis of persistence of this chronic infection is the tissue cyst. Thus, eliminating T. gondii cysts from chronically infected individuals before they become severely immunosuppressed will be able to prevent this serious disease. However, there are currently no drugs effective against the cysts. Our recent studies using a murine model uncovered that CD8+ immune T cells have a potent activity to directly penetrate into the cysts and induce their elimination through perforin- mediated mechanisms. We also identified that the N-terminal region (amino acids 41-152) of dense granule protein (GRA) 6 (GRA6Nt) of the parasite presented by the H-2Ld molecule is a key antigen to activate the anti- cyst CD8+ T cells. Our studies also identified that Iba1+ microglia and Ly6C+ macrophages accumulate to the cysts during the T cell-initiated immune process, and that these phagocytes kill T. gondii bradyzoites within the cysts, at least in part, by phagolysosome acidification. Based on these observations, the proposed studies are designed to obtain the information required for proceeding towards development of a vaccine to activate CD8+ T cells capable of targeting T. gondii cysts and eradicate chronic infection with this parasite in humans. For this purpose, we need to determine whether GRA6Nt activates anti-cyst CD8+ T cells through human MHC class I molecules, since the MHC class I molecules present antigens to activate CD8+ T cells. Aim 1 will address this point by employing three transgenic mouse strains expressing either of the three major MHC class I supermotifs that cover 90% of human population. Once the anti-cyst T cells are primed, these T cells need to be recruited to cyst-containing cells and activated not only by recognizing T. gondii antigens but also by appropriate costimulatory molecules expressed on the cyst-containing cells. Our recent studies suggested an involvement of CXCL10 chemokine and inducible constimulator ligand (ICOSL) in these processes. Thus, Aim 2 will determine the roles of CXCL10 and ICOSL in recruitment and activation of anti-cyst CD8+ T cells, respectively. Another critical but unsolved issue is that small numbers of cysts persist in the brains of infected mice even in the presence of anti-cyst CD8+ T cells. Our recent study revealed that these persisting cysts express significantly greater levels of mRNA for selected GRA and rhoptry (ROP) proteins when compared to the overall cyst population that exists in the absence of the T cells. Since GRAs and ROPs are secreted from the parasite into infected cells, upregulated secretion of these selected GRAs and ROPs could play crucial roles in manipulating the functions of cyst-containing cells to prevent the attack by CD8+ T cells. Thus, Aim 3 focuses to determine whether these GRAs and ROPs play key roles in the evasion of the cysts from the T cell attack. We will also address the molecular mechanisms underlying this evasion process. The information from these studies will establish the basis for developing a novel method to eradicate chronic T. gondii infection.

弓形虫慢性感染可重新激活并导致危及生命的弓形虫脑炎艾滋病患者和其他免疫功能低下的人。这种慢性感染持续存在的基础是组织囊肿。因此，在慢性感染个体成为弓形虫包囊之前将其消除严重的免疫抑制将能够预防这种严重的疾病。不过，目前还没有对囊肿有效的药物。我们最近使用小鼠模型的研究发现 CD8+ 免疫 T 细胞具有直接渗透到囊肿中并通过穿孔诱导其消除的有效活性中介机制。我们还发现致密颗粒的 N 末端区域（氨基酸 41-152） H-2Ld 分子呈递的寄生虫蛋白 (GRA) 6 (GRA6Nt) 是激活抗- 囊肿 CD8+ T 细胞。我们的研究还发现 Iba1+ 小胶质细胞和 Ly6C+ 巨噬细胞积累到在 T 细胞启动的免疫过程中形成包囊，并且这些吞噬细胞杀死 T. gondii 缓殖子囊肿，至少部分是通过吞噬溶酶体酸化。基于这些观察，拟议的研究是旨在获取继续开发激活 CD8+ 的疫苗所需的信息 T 细胞能够靶向弓形虫包囊并根除人类体内这种寄生虫的慢性感染。为了为此，我们需要确定GRA6Nt是否通过人MHC激活抗囊肿CD8+ T细胞 I 类分子，因为 MHC I 类分子呈递抗原来激活 CD8+ T 细胞。目标1将通过使用表达三种主要 MHC 类别之一的三种转基因小鼠品系来解决这一点 I 超级主题涵盖了 90% 的人口。一旦抗囊肿 T 细胞被激活，这些 T 细胞就需要被招募到含有包囊的细胞中，并不仅通过识别弓形虫抗原，而且还通过在含有囊肿的细胞上表达适当的共刺激分子。我们最近的研究表明 CXCL10 趋化因子和诱导刺激配体 (ICOSL) 参与这些过程。因此，目标 2 将确定 CXCL10 和 ICOSL 在抗囊肿 CD8+ T 细胞的招募和激活中的作用，分别。另一个关键但尚未解决的问题是，感染者的大脑中持续存在少量囊肿。即使在存在抗囊肿 CD8+ T 细胞的情况下，小鼠也能获得同样的效果。我们最近的研究表明，这些持续存在的囊肿与相比，所选 GRA 和棒状体 (ROP) 蛋白的 mRNA 表达水平明显更高在没有 T 细胞的情况下存在的囊肿总数。由于 GRA 和 ROP 是由当寄生虫进入受感染细胞时，这些选定的 GRA 和 ROP 的分泌上调可能发挥至关重要的作用操纵含囊细胞的功能以防止 CD8+ T 细胞的攻击。因此，目标 3 重点确定这些 GRA 和 ROP 是否在 T 细胞逃避包囊过程中发挥关键作用攻击。我们还将探讨这一逃避过程背后的分子机制。信息来自这些研究将为开发根除慢性弓形虫感染的新方法奠定基础。