Pathogenesis of Trypanosoma cruzi infection

摘要 拉丁美洲与恰加斯病相关的发病率和死亡率超过了众所周知的情况 例如疟疾、结核病或艾滋病。数百万人受到这种锥虫病的影响。不是 疫苗可以预防这种疾病，药物治疗有严重的副作用，而不是 完全有效。克氏锥虫在哺乳动物宿主中的存活取决于寄生虫的存活 能够感染宿主细胞、繁殖并在宿主的血液中存活足够长的时间以保证其 通过吸血昆虫媒介传播。我们的目标是研究这些生存机制 以及它们在克氏毛滴虫感染发病机制中的作用，并揭示了控制弓形虫感染的潜在方法 疾病。克氏锥虫在哺乳动物宿主血液和肠道中的存活 这种载体在很大程度上取决于它们在体内对渗透压急剧变化的耐受性。 通过哺乳动物宿主肾髓质的循环(1,300-1,400 mOsm/kg)或它们的通道 通过直肠的昆虫媒介(1000mOsm/kg)，我们发现聚磷酸盐(Polyp) 而收缩空泡复合体(CVC)在其生存机制中起着至关重要的作用。近期 我们实验室的结果表明，息肉和/或焦磷酸盐(PPI)也可能参与了 克氏毛滴虫感染的发病机制。为了降低息肉水平，我们过度表达了一种降解酶 同时对PPI和息肉进行水解，导致PPI/息肉显著降低。突变类鞭毛虫 过度表达这种酶不会产生可检测到的寄生虫病，在几个实验中 受感染的动物在其他致命的感染中幸存下来。感染PPI/息肉缺陷寄生虫的小鼠 环磷酰胺免疫抑制后未出现寄生虫血症强烈提示 感染已完全清除。我们的结果强调了PPI/息肉在 克氏毛滴虫感染的发病机制。息肉已被证明是细菌的毒力因子，但几乎没有 已知其在真核病原体中的作用，以及其促凝血和促炎活性。 在哺乳动物宿主内的生存还取决于克氏锥虫入侵不同宿主细胞的能力， 从寄生蜂的液泡中逃脱，在细胞内复制。克鲁兹毛滴虫的转唾液酸酶 被证明在这些机制中起着至关重要的作用。然而，评估的主要障碍是 反式唾液酸酶的作用是由于大量的敲除寄生虫 基因拷贝散布在基因组中。我们发现，反式唾液酸会减少通过 可收缩的液泡通向质膜，并通过干扰干扰这种运输 当它们通过CVC时，会导致寄生虫的表面没有这些蛋白质。这个 研究这一贩运机制和干扰这种贩运的方法将有助于 对克氏毛滴虫感染发病机制的认识。

Abstract Morbidity and mortality associated with Chagas disease in Latin America exceed better-known conditions such as malaria, tuberculosis, or AIDS. Millions of people are affected by this trypanosomiasis. No vaccines are available to prevent this disease and drug treatments have serious side effects and are not completely effective. Survival of Trypanosoma cruzi in the mammalian hosts depends on the parasite's ability to infect host cells, reproduce, and live in the blood of the host long enough to warrant its transmission through a bloodsucking insect vector. Our aim is to investigate these survival mechanisms and their role in the pathogenesis of T. cruzi infection, and shed light into potential ways to control the disease. Survival of T. cruzi trypomastigotes in the blood of the mammalian host and in the intestine of the vector depends in great part on their ability to tolerate dramatic changes in osmolarity during their circulation through the kidney medulla of the mammalian host (1,300-1,400 mOsm/Kg) or their passage through the rectum of the insect vector (1,000 mOsm/Kg), and we have found that polyphosphate (polyP) and the contractile vacuole complex (CVC) have en essential role in their survival mechanisms. Recent results from our laboratory suggest that polyP and/or pyrophosphate (PPi) could also be involved in the pathogenesis of T. cruzi infection. To reduce polyP levels we overexpressed a degradative enzyme that hydrolyzes both PPi and polyP resulting in a dramatic decrease of PPi/polyP. Mutant trypomastigotes overexpressing the enzyme did not produce detectable parasitemias and in several experiments all infected animals survived an otherwise lethal infection. Mice infected with parasites deficient in PPi/polyP failed to develop parasitemia after immunosuppression with cyclophosphamide strongly suggesting that infection had been completely cleared. Our results underscore an important role for PPi/polyP in the pathogenesis of T. cruzi infection. PolyP has been shown to act as a virulence factor in bacteria but little is known on its role in eukaryotic pathogens, besides its pro-coagulant and pro-inflammatory activities. Survival within the mammalian host also depends on the ability of T. cruzi to invade different host cells, escape from the parasitophorus vacuole and replicate intracellularly. T. cruzi trans-sialidases have been demonstrated to have essential roles in these mechanisms. However, the main obstacle in assessing the function of trans-sialidases is that knockout parasites were never obtained due to the large number of gene copies scattered through the genome. We have found that trans-sialidases traffic through the contractile vacuole in their way to the plasma membrane, and that disruption of this traffic by interfering with their passage through the CVC results in parasites devoid of these proteins in their surface. The study of this trafficking mechanism and of ways to interfere with this traffic will contribute to the understanding of the pathogenesis of T. cruzi infection.