Mechanisms of Resistance and Susceptibility to African Trypanosome Infection

非洲锥虫感染的耐药性和易感性机制

• 批准号: 8079473
• 负责人: STEPHEN L HAJDUK
• 金额: $ 36.75万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-02-15 至 2015-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8079473
• 关键词: Address; Affinity; Africa South of the Sahara; African; African Trypanosomiasis; Anabolism; Antigen-Antibody Complex; Apolipoprotein A-I; Apolipoproteins; Binding; Binding Proteins; Biochemical; Biological Assay; Cattle; Complex; Cytolysis; Down-Regulation; Environment; Fluorescence; Genes; Goals; Grant; Hemoglobin; High Density Lipoproteins; Human; Immune; Immune system; In Vitro; Infection; Lead; Leishmania; Ligands; Lipids; Lipoproteins; Liposomes; Lysosomes; Lytic; Mammalian Cell; Mammals; Measures; Mediating; Membrane; Minor; Modeling; Molecular; Multiprotein Complexes; Natural Immunity; Outcome; Parasite resistance; Parasites; Pathway interactions; Peptide Signal Sequences; Pharmaceutical Preparations; Phospholipids; Plasmodium; Play; Predisposition; Primates; Protein Biosynthesis; Proteins; Relative (related person); Resistance; Risk; Role; Serum; Site; Sterility; Toxic effect; Toxin; Transgenic Mice; Trypanosoma; Trypanosoma brucei brucei; Trypanosoma brucei gambiense; Trypanosoma brucei rhodesiense; Vaccines; Variant; base; cytotoxic; haptoglobin-related protein; human disease; inhibitor/antagonist; killings; monolayer; mouse model; nagana; novel strategies; public health relevance; receptor; research study; resistance factors; resistance mechanism; therapeutic development

DESCRIPTION (provided by applicant): Trypanosoma brucei brucei causes Nagana in cattle but is non-infectious to humans because of its susceptibility to the cytotoxic activity of normal human serum. This innate immune activity is due to a minor subclass of high-density lipoprotein (HDL) termed the Trypanosome Lytic Factor (TLF). TLF contains apolipoprotein A-1 (apoA-1), a protein found in all HDLs, and two primate specific proteins, haptoglobin related protein (Hpr) and apolipoprotein L-1 (apoL-1). Both Hpr and apoL-1 have been shown to be necessary for maximal trypanosome killing in vitro and in a transgenic mouse model. Hpr is a hemoglobin (Hb) binding protein and Hb is an essential co-factor for trypanosome killing by TLF. The cellular pathway of TLF mediated lysis of T. b. brucei initiates with binding of TLF to a high affinity receptor (Tb927.6.440) located in the flagellar pocket. Following binding TLF is rapidly taken up and localized to the lysosome. Within the acidified lysosome TLF is activated and kills T. b. brucei by destabilization of the lysosomal membrane. The human sleeping sickness parasite Trypanosoma brucei rhodesiense has evolved a defense against TLF. T. b. rhodesiense produces a potent inhibitor of TLF, Serum Resistance Associated protein (SRA), which binds apoL-1 and neutralizes the activity of TLF. Trypanosoma brucei gambiense also infects humans but lacks SRA and, as shown in this proposal, resists TLF killing by down regulation of the TLF receptor. In this proposal, we outline a number of experiments that will provide important information on the mechanism of assembly of TLF and how its composition might be altered to produce "variant TLFs" with activity against the human sleeping sickness parasites (Aim 1). To better understand the biophysical basis for membrane destabilization by native TLF and its constituent proteins we will use model liposomes of defined composition in fluorescence based assays to measure TLF induced changes in lipid dynamics (Aim 2). Finally, we will investigate the cellular, molecular and biochemical basis of SRA-dependent and SRA-independent resistance to TLF. In addition to resolving a longstanding question concerning how SRA inhibits TLF activity we will investigate the mechanism of T. b. gambiense resistance to TLF (Aim 3). Our long-term goals are to develop a better understanding of the mechanism of TLF killing and how the human sleeping sickness parasites evade this activity. This may allow us to develop novel approaches for the treatment of this important human disease. PUBLIC HEALTH RELEVANCE: African sleeping sickness is a re-emerging human disease in sub- Saharan Africa. It is currently estimated that over 35 million people are at risk and the number of infected people may exceed 300,000. There is no vaccine for African sleeping sickness and most of the drugs have serious toxicity problems. The proposed studies on the mechanism of action of the innate immune complex, TLF, may lead to the identification of novel approaches for therapeutic development.

描述（由申请人提供）：布氏锥虫会导致牛的Nagana，但由于其对正常人血清的细胞毒活性敏感，因此对人类无传染性。这种先天免疫活性是由于高密度脂蛋白（HDL）的一个小亚类，称为锥虫溶解因子（TLF）。TLF含有载脂蛋白A-1（apoA-1），一种在所有HDL中发现的蛋白质，以及两种灵长类特异性蛋白质，触珠蛋白相关蛋白（Hpr）和载脂蛋白L-1（apoL-1）。Hpr和apoL-1都已被证明是体外和转基因小鼠模型中最大锥虫杀伤所必需的。Hpr是血红蛋白（Hb）结合蛋白，Hb是TLF杀死锥虫的必需辅助因子。TLF介导T. B. 布氏杆菌通过TLF与位于鞭毛袋中的高亲和力受体（Tb 927.6.440）结合而启动。结合后，TLF被迅速摄取并定位于溶酶体。在酸化的溶酶体内，TLF被激活并杀死T。B. 通过溶酶体膜的去稳定化来抑制布氏杆菌。人类昏睡病寄生虫布氏罗得西亚锥虫已经进化出了对TLF的防御。t. B.罗得西亚杆菌产生TLF的有效抑制剂，血清抗性相关蛋白（SRA），其结合apoL-1并中和TLF的活性。布氏冈比亚锥虫也感染人类，但缺乏SRA，并且如该提议所示，通过下调TLF受体来抵抗TLF杀伤。在本提案中，我们概述了一些实验，这些实验将提供有关TLF组装机制的重要信息，以及如何改变其组成以产生具有抗人类昏睡病寄生虫活性的"变体TLF"（目标1）。为了更好地理解天然TLF及其组成蛋白引起的膜去稳定的生物物理基础，我们将在基于荧光的测定中使用确定组成的模型脂质体来测量TLF诱导的脂质动力学变化（目的2）。最后，我们将研究细胞，分子和生化基础的SRA依赖性和SRA非依赖性的TLF的阻力。除了解决一个长期存在的关于SRA如何抑制TLF活性的问题外，我们还将研究T。B.冈比亚对TLF的抗性（Aim 3）。我们的长期目标是更好地了解TLF杀死的机制以及人类昏睡病寄生虫如何逃避这种活动。这可能使我们能够开发新的方法来治疗这种重要的人类疾病。 公共卫生相关性：非洲昏睡病是一种在撒哈拉以南非洲重新出现的人类疾病。目前估计有3 500多万人处于危险之中，感染人数可能超过30万。非洲昏睡病没有疫苗，大多数药物都有严重的毒性问题。对先天免疫复合物TLF的作用机制的拟议研究可能会导致确定新的治疗方法。