Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA.
J Virol. 2013 Jul;87(13):7471-85. doi: 10.1128/JVI.03316-12. Epub 2013 Apr 24.
Ebola virus (EBOV) infections are characterized by deficient T lymphocyte responses, T lymphocyte apoptosis, and lymphopenia in the absence of direct infection of T lymphocytes. In contrast, dendritic cells (DC) are infected but fail to mature appropriately, thereby impairing the T cell response. We investigated the contributions of EBOV proteins in modulating DC maturation by generating recombinant viruses expressing enhanced green fluorescent protein and carrying mutations affecting several potentially immunomodulating domains. They included envelope glycoprotein (GP) domains, as well as innate response antagonist domains (IRADs) previously identified in the VP24 and VP35 proteins. GP expressed by an unrelated vector, but not the wild-type EBOV, was found to strongly induce DC maturation, and infections with recombinant EBOV carrying mutations disabling GP functional domains did not restore DC maturation. In contrast, each of the viruses carrying mutations disabling any IRAD in VP35 induced a dramatic upregulation of DC maturation markers. This was dependent on infection, but not interaction with GP. Disabling of IRADs also resulted in up to a several hundredfold increase in secretion of cytokines and chemokines. Furthermore, these mutations induced formation of homotypic DC clusters, which represent close correlates of their maturation and presumably facilitate transfer of antigen from migratory DC to lymph node DC. Thus, an individual IRAD is insufficient to suppress DC maturation; rather, the suppression of DC maturation and the "immune paralysis" observed during EBOV infections results from a cooperative effect of two or more individual IRADs.
埃博拉病毒（EBOV）感染的特征是 T 淋巴细胞反应不足、T 淋巴细胞凋亡和淋巴细胞减少，而 T 淋巴细胞未直接感染。相比之下，树突状细胞（DC）被感染但未能适当成熟，从而损害 T 细胞反应。我们通过生成表达增强型绿色荧光蛋白并携带影响几个潜在免疫调节结构域的突变的重组病毒，研究了 EBOV 蛋白在调节 DC 成熟中的作用。这些结构域包括包膜糖蛋白（GP）结构域，以及先前在 VP24 和 VP35 蛋白中鉴定出的先天反应拮抗剂结构域（IRAD）。由相关载体表达的 GP，但不是野生型 EBOV，被发现强烈诱导 DC 成熟，而携带使 GP 功能结构域失活的突变的重组 EBOV 感染并未恢复 DC 成熟。相比之下，携带使 VP35 中任何一个 IRAD 失活的突变的病毒都导致 DC 成熟标志物的显著上调。这依赖于感染，但不依赖于与 GP 的相互作用。IRAD 的失活还导致细胞因子和趋化因子的分泌增加了数百倍。此外，这些突变诱导同源型 DC 簇的形成，这与它们的成熟密切相关，并且可能有助于从迁移的 DC 将抗原转移到淋巴结 DC。因此，单个 IRAD 不足以抑制 DC 成熟；相反，EBOV 感染期间观察到的 DC 成熟抑制和“免疫麻痹”是由两个或更多个单独的 IRAD 的协同作用导致的。
