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: 8274806
• 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/8274806
• 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）：布氏锥虫在牛中引起那加那病，但由于其对正常人血清的细胞毒性活性敏感，因此对人类不具有感染性。这种先天免疫活性归因于高密度脂蛋白 (HDL) 的一个小亚类，称为锥虫裂解因子 (TLF)。 TLF 含有载脂蛋白 A-1 (apoA-1)（一种存在于所有 HDL 中的蛋白质）以及两种灵长类动物特异性蛋白质：触珠蛋白相关蛋白 (Hpr) 和载脂蛋白 L-1 (apoL-1)。 Hpr 和 apoL-1 均已被证明对于体外和转基因小鼠模型中最大程度地杀死锥虫是必需的。 Hpr 是一种血红蛋白 (Hb) 结合蛋白，Hb 是 TLF 杀死锥虫的重要辅助因子。 TLF 介导的 T. b. 裂解的细胞途径。 brucei 首先将 TLF 与位于鞭毛袋中的高亲和力受体 (Tb927.6.440) 结合。结合后，TLF 被迅速吸收并定位到溶酶体。在酸化的溶酶体内，TLF 被激活并杀死 T. b． 布鲁氏菌通过溶酶体膜的不稳定而产生。人类昏睡病寄生虫罗得西亚布氏锥虫已经进化出针对 TLF 的防御能力。 T.b. rhodesense 产生一种有效的 TLF 抑制剂，即血清耐药相关蛋白 (SRA)，它与 ​​apoL-1 结合并中和 TLF 的活性。布氏冈比亚锥虫也感染人类，但缺乏 SRA，并且如该提案所示，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对抗人类昏睡病寄生虫活性的“变体 TLF”（目标 1）。为了更好地了解天然 TLF 及其组成蛋白造成膜不稳定的生物物理基础，我们将在基于荧光的测定中使用具有确定成分的模型脂质体来测量 TLF 诱导的脂质动力学变化（目标 2）。最后，我们将研究 SRA 依赖性和 SRA 独立性 TLF 耐药性的细胞、分子和生化基础。除了解决有关 SRA 如何抑制 TLF 活性的长期问题外，我们还将研究 T. b. 的机制。冈比亚对 TLF 的抵抗（目标 3）。我们的长期目标是更好地了解 TLF 杀灭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出治疗这种重要人类疾病的新方法。 公共卫生相关性：非洲昏睡病是撒哈拉以南非洲重新出现的人类疾病。目前估计超过3500万人处于危险之中，感染人数可能超过30万。非洲昏睡病尚无疫苗，且大多数药物都存在严重的毒性问题。对先天免疫复合物 TLF 作用机制的拟议研究可能会导致治疗开发新方法的确定。