Pathogenesis of Trypanosoma cruzi infection

摘要 在拉丁美洲，与恰加斯病相关的发病率和死亡率超过了更知名的疾病 如疟疾、肺结核或艾滋病。数百万人受到这种锥虫的影响。没有 疫苗可用于预防这种疾病，药物治疗具有严重的副作用， 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 感染宿主细胞、繁殖并在宿主血液中存活足够长时间以保证其 通过吸血昆虫传播我们的目的是研究这些生存机制 及其在T. cruzi感染，并揭示了潜在的方法来控制 疾病T的生存。哺乳动物宿主血液和肠道中的克氏锥鞭毛体 载体在很大程度上取决于它们在其施用期间耐受渗透压的急剧变化的能力。 通过哺乳动物宿主肾髓质的循环（1，300 - 1，400 mOsm/Kg）或其通道 通过直肠的昆虫载体（1,000 mOsm/Kg），我们已经发现，聚磷酸盐（聚P） 收缩泡复合体（CVC）在其生存机制中起重要作用。最近 我们实验室的结果表明，聚P和/或焦磷酸盐（PPi）也可能参与 致病性T.克氏感染为了降低polyP水平，我们过度表达了一种降解酶， 水解PPi和聚P，导致PPi/聚P的显著降低。突变型锥鞭毛体 过表达该酶没有产生可检测的寄生虫血症，并且在几个实验中， 被感染的动物在致命的感染中存活了下来。感染PPi/polyP缺陷型寄生虫的小鼠 环磷酰胺免疫抑制后未发生寄生虫血症，这强烈表明， 感染已被完全清除。我们的研究结果强调了PPi/polyP在肿瘤发生中的重要作用。 致病性T.克氏感染PolyP已被证明是细菌中的毒力因子，但很少 除了其促凝血和促炎活性外，已知其在真核病原体中的作用。 在哺乳动物宿主中的存活也取决于T. cruzi入侵不同的宿主细胞， 逃离寄生虫液泡并在细胞内复制。T. Cruzi转唾液酸酶已经被 在这些机制中发挥着重要作用。然而，评估的主要障碍是， 转唾液酸酶的功能是，由于大量的转唾液酸酶， 基因拷贝散布在基因组中。我们已经发现，转唾液酸酶通过 收缩的液泡在他们的方式质膜，并中断这种交通干扰 它们通过CVC导致寄生虫在其表面缺乏这些蛋白质。的 研究这种贩运机制和干预这种贩运的方法将有助于 对T.克氏感染

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.