Instituto de Biofisica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, Brazil.
J Immunol. 2011 Jan 1;186(1):411-22. doi: 10.4049/jimmunol.1002175. Epub 2010 Nov 22.
Leishmania major is a protozoan parasite that causes skin ulcerations in cutaneous leishmaniasis. In the mammalian host, the parasite resides in professional phagocytes and has evolved to avoid killing by macrophages. We identified L. major genes encoding inhibitors of serine peptidases (ISPs), which are orthologs of bacterial ecotins, and found that ISP2 inhibits trypsin-fold S1A family peptidases. In this study, we show that L. major mutants deficient in ISP2 and ISP3 (Δisp2/3) trigger higher phagocytosis by macrophages through a combined action of the complement type 3 receptor, TLR4, and unregulated activity of neutrophil elastase (NE), leading to parasite killing. Whereas all three components are required to mediate enhanced parasite uptake, only TLR4 and NE are necessary to promote parasite killing postinfection. We found that the production of superoxide by macrophages in the absence of ISP2 is the main mechanism controlling the intracellular infection. Furthermore, we show that NE modulates macrophage infection in vivo, and that the lack of ISP leads to reduced parasite burdens at later stages of the infection. Our findings support the hypothesis that ISPs function to prevent the activation of TLR4 by NE during the Leishmania-macrophage interaction to promote parasite survival and growth.
利什曼原虫是一种原生动物寄生虫，可引起皮肤利什曼病的皮肤溃疡。在哺乳动物宿主中，寄生虫存在于专业吞噬细胞中，并已进化为避免被巨噬细胞杀死。我们鉴定了编码丝氨酸蛋白酶抑制剂（ISPs）的利什曼原虫基因，这些基因是细菌生态素的同源物，发现 ISP2 抑制胰蛋白酶折叠 S1A 家族肽酶。在这项研究中，我们表明，缺乏 ISP2 和 ISP3 的利什曼原虫突变体（Δisp2/3）通过补体 3 受体、TLR4 和不受调节的中性粒细胞弹性蛋白酶（NE）的联合作用，触发巨噬细胞吞噬作用增加，导致寄生虫杀伤。虽然所有三个成分都需要介导增强的寄生虫摄取，但只有 TLR4 和 NE 是感染后促进寄生虫杀伤所必需的。我们发现，在没有 ISP2 的情况下，巨噬细胞中超氧化物的产生是控制细胞内感染的主要机制。此外，我们表明，NE 在体内调节巨噬细胞感染，并且缺乏 ISP 会导致感染后期寄生虫负荷减少。我们的研究结果支持以下假设：ISPs 的功能是防止 NE 在利什曼原虫与巨噬细胞相互作用过程中激活 TLR4，以促进寄生虫的存活和生长。
