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：
10626881
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 2025-05-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10626881
关键词：
Acquired Immunodeficiency Syndrome Acute Address Amino Acids Antigen Presentation Antigens Brain CD28 gene CD8 Antigens CD8-Positive T-Lymphocytes 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 Macrophage Mediating Messenger RNA Methods Microglia Molecular Mouse Strains Mus N-terminal Parasites Patients Penetration Phagocytes Phagocytosis Phagolysosome Pharmaceutical Preparations Play Population Process Protein Secretion Proteins Rag1 Mouse Role System T-Cell Activation T-Lymphocyte Tissues Toxoplasma Toxoplasma gondii Toxoplasmosis Transgenic Mice Vaccines chemokine chronic infection design immunological intervention immunosuppressed improved inducible gene expression 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.

弓形虫的慢性感染可重新激活并导致威胁生命 AIDS患者和其他免疫功能低下的个体。这种慢性感染的持久性的基础是组织囊肿。因此，在变成长期感染的个体中消除gondii囊肿严重的免疫抑制作用将能够预防这种严重的疾病。但是，目前没有对囊肿有效的药物。我们最近使用鼠模型的研究发现了CD8+免疫T 细胞具有有效的活性，可以直接渗透到囊肿中，并通过穿孔蛋白 - 中介机制。我们还确定了致密颗粒的N末端区域（氨基酸41-152） H-2LD分子提出的寄生虫的蛋白质（GRA）6（GRA6NT）是激活抗抗原的关键抗原囊肿CD8+ T细胞。我们的研究还确定IBA1+小胶质细胞和Ly6c+巨噬细胞积聚到 T细胞发射的免疫过程中的囊肿，并且这些吞噬细胞杀死了gondii bradyzoites的囊肿至少部分通过吞噬酸性酸化。基于这些观察结果，拟议的研究是旨在获取开发疫苗以激活CD8+所需的信息 T细胞能够靶向T. gondii囊肿并用这种寄生虫在人类中消除慢性感染。为了此目的，我们需要确定GRA6NT是否通过人MHC激活抗Cyst CD8+ T细胞 I类分子，因为MHC I类分子提出抗原以激活CD8+ T细胞。目标1意志通过使用三个表达三个主要MHC类之一的转基因小鼠菌株来解决这一点我的超级木制占了90％的人口。一旦抗囊T细胞启动，这些T细胞就需要被募集到含囊肿的细胞中，不仅通过识别弓形虫抗原，而且通过在含囊肿的细胞上表达的适当共刺激分子。我们最近的研究表明 CXCL10趋化因子和可诱导的混血儿配体（ICOSL）参与这些过程。因此，瞄准 2将确定CXCL10和ICOSL在抗Cyst CD8+ T细胞的募集和激活中的作用，分别。另一个关键但未解决的问题是，少数囊肿持续了被感染的大脑小鼠即使存在抗Cyst CD8+ T细胞。我们最近的研究表明，这些持续的囊肿与之相比在没有T细胞的情况下存在的总体囊肿群。由于gras和rops是从中分泌的这些选定的gras和rops的寄生虫在受感染的细胞中的分泌上调可能发挥至关重要的作用在操纵含囊肿细胞的功能以防止CD8+ T细胞攻击的功能中的作用。因此，目标3 专注于确定这些GRA和ROP是否在从T细胞的囊肿逃避中起关键作用攻击。我们还将解决这种逃避过程的基础机制。来自这些研究将建立开发一种新的方法来消除慢性T. gondii感染的基础。