Origin of Virulence Factors in African Trypanosomes

描述（由申请方提供）：冈比亚布氏锥虫和罗得西亚布氏锥虫是引起人类非洲昏睡病的原生动物寄生虫，而布氏锥虫引起牛的消耗性疾病，称为Nagana。这些寄生虫在形态上难以区分，唯一明确的表型区别是T。B.布鲁氏菌感染人类。对T. B.布氏菌感染由人、猿和旧世界猴血清中发现的锥虫溶解因子（TLF）介导。TLF的活性成分是灵长类特异性触珠蛋白相关蛋白（HPR）。这种蛋白质是防止人类被T. B.布氏杆菌，从而严重限制了其寄主范围。人类昏睡病锥虫T. B. rhodesiense和T. B. gambiense，由于它们对HPR的细胞毒性作用具有抗性，因此能够感染人类。 分析人感染性和非感染性T。B.罗得西亚病毒导致了人类感染所必需的锥虫基因的鉴定。血清抗性相关基因（SRA）在T. B.罗得西亚分离物是变异表面糖蛋白（VSG）超家族的成员。SRA基因在T. B.布氏杆菌，尽管存在类似的基因序列。为了确定人类感染性的机制，我们选择了T。B.抗TLF的布鲁氏菌品系。TLF抗性株系的抗TLF能力较强。B.布氏杆菌能够避免HPR的细胞毒性，尽管缺乏SRA基因。TLF易感和抗性7-b中全基因组基因表达模式的检查布氏细胞系将提供锥虫中影响宿主范围和人类感染的生物学途径的连贯画面。作为T. B.布氏杆菌基本上是完整的，我们已经能够选择T. B.在体外对TLF具有不同程度敏感性的布氏杆菌中，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mRNA表达的全基因组水平。为了检测与人类感染性相关的基因的调控，我们将通过从10个T的等基因系的mRNA产生大约14，000个21 bp的序列标签来进行SAGE。B.布氏菌（427株）对TLF的抗性水平不同。这项研究将提供一个全面的了解锥虫基因表达的变化，以响应人类先天免疫的选择性压力，并将提供线索的SRA基因的起源。

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.