Origin of Virulence Factors in African Trypanosomes

非洲锥虫毒力因子的起源

• 批准号: 6725346
• 负责人: ANDREW G MCARTHUR
• 金额: $ 7.75万
• 依托单位: MARINE BIOLOGICAL LABORATORY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-04-01 至 2006-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6725346
• 关键词: Trypanosoma brucei rhodesiense; cellular immunity; computer program /software; gene expression; genetic regulation; haptoglobins; host organism interaction; immunogenetics; messenger RNA; microorganism culture; molecular cloning; nucleic acid sequence; polymerase chain reaction; protein structure function; serial analysis of gene expression; transfection; virulence

DESCRIPTION (provided by the applicant): Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are protozoan parasites that cause African sleeping sickness in humans while Trypanosoma brucei brucei causes a wasting disease in cattle called Nagana. These parasites are morphologically indistinguishable and the only clear phenotypic distinction is the inability of T. b. brucei to infect humans. Innate protection against T. b. brucei infection is mediated by Trypanosome Lytic Factors (TLF) found in the serum of humans, apes and old-world monkeys. The active component of TLF is the primate specific haptoglobin related protein (HPR). This protein is the sole factor preventing infection of humans by T. b. brucei, thus severely restricting its host range. The human sleeping sickness trypanosomes, T. b. rhodesiense and T. b. gambiense, are able to infect humans due to their resistance to the cytotoxic action of HPR. Analysis of human infectious and non-infectious lines of T. b. rhodesiense resulted in the identification of a trypanosome gene what is necessary for human infection. The serum resistance associated (SRA) gone is highly conserved in T. b. rhodesiense isolates and is a member of the variant surface glycoprotein (VSG) superfamily. The SRA gene is absent in T. b. brucei, although similar gene sequences are present. To define the mechanism of human infectivity, we have selected for T. b. brucei lines resistant to TLF. The TLF resistant lines of T. b. brucei are able to avoid the cytotoxicity of HPR despite lacking the SRA gene. Examination of genome-wide gene expression patterns in TLF susceptible and resistant 7-.b. brucei lines will provide a coherent picture of the biological pathways in trypanosomes that influence host range and human infection. As the genome sequence of T. b. brucei is largely complete and we have been able to select for isogenic lines of T. b. brucei with differing degrees of susceptibility to TLF in vitro, we propose to utilize Serial Analysis of Gene Expression (SAGE) to monitor genome-wide levels of mRNA expression associated with human virulence. To detect regulation of genes related to human infectivity, we will perform SAGE by generating approximately 14,000 21 bp sequence tags from the mRNA of 10 isogenic lines of T. b. brucei (427 strain) differing in level of resistance to TLF. This research will provide a comprehensive understanding of changes in trypanosome gene expression in response to selective pressure of human innate immunity and will provide clues as to the origin of the SRA gene.

描述（由申请人提供）：布氏冈比亚锥虫和罗得西亚布氏锥虫是原生动物寄生虫，会导致人类非洲昏睡病，而布氏锥虫会导致牛患一种名为 Nagana 的消耗性疾病。这些寄生虫在形态上无法区分，唯一明显的表型区别是 T. b. 无法区分。布氏杆菌感染人类。针对结核菌的先天保护。布氏杆菌感染是由人类、猿和古猴血清中发现的锥虫裂解因子 (TLF) 介导的。 TLF 的活性成分是灵长类动物特异性触珠蛋白相关蛋白 (HPR)。这种蛋白质是防止人类感染结核菌的唯一因素。 brucei，从而严重限制了其寄主范围。人类昏睡病锥虫，T. b.罗德西亚和 T. b.冈比亚人由于对 HPR 的细胞毒性作用具有抵抗力而能够感染人类。 T. b. 人类传染性和非传染性系的分析。罗德西亚导致了人类感染所必需的锥虫基因的鉴定。相关血清耐药性（SRA）在 T. b 中高度保守。 rhodesense 分离出来，并且是变异表面糖蛋白 (VSG) 超家族的成员。 T. b. 中不存在 SRA 基因。 brucei，尽管存在相似的基因序列。为了定义人类传染性的机制，我们选择了 T. b。 brucei 系对 TLF 具有抗性。 T. b.的TLF抗性品系。尽管缺乏 SRA 基因，布鲁氏菌仍能够避免 HPR 的细胞毒性。检查 TLF 易感性和抗性 7-.b 中的全基因组基因表达模式。布鲁斯系将提供锥虫中影响宿主范围和人类感染的生物途径的连贯图景。作为 T. b. 的基因组序列。 brucei 基本上是完整的，我们已经能够选择 T. b. 的等基因系。布鲁氏菌在体外对 TLF 具有不同程度的易感性，我们建议利用基因表达系列分析 (SAGE) 来监测与人类毒力相关的全基因组 mRNA 表达水平。为了检测与人类感染性相关的基因的调控，我们将通过从 T. b. 的 10 个同基因系的 mRNA 生成约 14,000 个 21 bp 序列标签来执行 SAGE。 brucei（427 菌株）对 TLF 的抗性水平不同。这项研究将全面了解锥虫基因表达因人类先天免疫选择性压力而发生的变化，并为 SRA 基因的起源提供线索。