Tropical Disease Research Unit and Sandler Center for Drug Discovery, Department of Pathology, University of California, San Francisco, California, United States of America.
PLoS Pathog. 2011 Sep;7(9):e1002139. doi: 10.1371/journal.ppat.1002139. Epub 2011 Sep 1.
Trypanosoma cruzi is the causative agent of Chagas' disease. Novel chemotherapy with the drug K11777 targets the major cysteine protease cruzain and disrupts amastigote intracellular development. Nevertheless, the biological role of the protease in infection and pathogenesis remains unclear as cruzain gene knockout failed due to genetic redundancy. A role for the T. cruzi cysteine protease cruzain in immune evasion was elucidated in a comparative study of parental wild type- and cruzain-deficient parasites. Wild type T. cruzi did not activate host macrophages during early infection (<60 min) and no increase in ∼P iκB was detected. The signaling factor NF-κB P65 colocalized with cruzain on the cell surface of intracellular wild type parasites, and was proteolytically cleaved. No significant IL-12 expression occurred in macrophages infected with wild type T. cruzi and treated with LPS and BFA, confirming impairment of macrophage activation pathways. In contrast, cruzain-deficient parasites induced macrophage activation, detectable iκB phosphorylation, and nuclear NF-κB P65 localization. These parasites were unable to develop intracellularly and survive within macrophages. IL 12 expression levels in macrophages infected with cruzain-deficient T. cruzi were comparable to LPS activated controls. Thus cruzain hinders macrophage activation during the early (<60 min) stages of infection, by interruption of the NF-κB P65 mediated signaling pathway. These early events allow T. cruzi survival and replication, and may lead to the spread of infection in acute Chagas' disease.
克氏锥虫是恰加斯病的病原体。以药物 K11777 为靶点的新型化疗药物针对主要半胱氨酸蛋白酶克氏锥虫蛋白酶，并破坏内阿米巴体的细胞内发育。然而，由于基因冗余，克氏锥虫蛋白酶基因敲除失败，该蛋白酶在感染和发病机制中的生物学作用仍不清楚。在对亲本野生型和克氏锥虫缺陷型寄生虫的比较研究中，阐明了 T. cruzi 半胱氨酸蛋白酶克氏锥虫在免疫逃避中的作用。野生型 T. cruzi 在早期感染(<60 min)期间不会激活宿主巨噬细胞，也不会检测到∼P iκB 的增加。信号因子 NF-κB P65 与细胞内野生型寄生虫表面的克氏锥虫共定位，并被蛋白水解切割。用 LPS 和 BFA 处理感染野生型 T. cruzi 的巨噬细胞后，未发生明显的 IL-12 表达，证实了巨噬细胞激活途径受损。相比之下，克氏锥虫缺陷型寄生虫诱导巨噬细胞激活，可检测到 iκB 磷酸化和核 NF-κB P65 定位。这些寄生虫无法在细胞内发育并在巨噬细胞内存活。感染克氏锥虫缺陷型 T. cruzi 的巨噬细胞中的 IL 12 表达水平与 LPS 激活对照相当。因此，克氏锥虫通过中断 NF-κB P65 介导的信号通路，在感染的早期(<60 min)阶段阻碍巨噬细胞的激活。这些早期事件允许 T. cruzi 存活和复制，并可能导致急性恰加斯病中的感染传播。
