Zhang Yue, Tam Jason W, Mena Patricio, van der Velden Adrianus W M, Bliska James B
Center for Infectious Diseases and Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America.
PLoS Pathog. 2015 Oct 15;11(10):e1005167. doi: 10.1371/journal.ppat.1005167. eCollection 2015 Oct.
During Yersinia pseudotuberculosis infection of C57BL/6 mice, an exceptionally large CD8+ T cell response to a protective epitope in the type III secretion system effector YopE is produced. At the peak of the response, up to 50% of splenic CD8+ T cells recognize the epitope YopE69-77. The features of the interaction between pathogen and host that result in this large CD8+ T cell response are unknown. Here, we used Y. pseudotuberculosis strains defective for production, secretion and/or translocation of YopE to infect wild-type or mutant mice deficient in specific dendritic cells (DCs). Bacterial colonization of organs and translocation of YopE into spleen cells was measured, and flow cytometry and tetramer staining were used to characterize the cellular immune response. We show that the splenic YopE69-77-specific CD8+ T cells generated during the large response are polyclonal and are produced by a "translocation-dependent" pathway that requires injection of YopE into host cell cytosol. Additionally, a smaller YopE69-77-specific CD8+ T cell response (~10% of the large expansion) can be generated in a "translocation-independent" pathway in which CD8α+ DCs cross present secreted YopE. CCR2-expressing inflammatory DCs were required for the large YopE69-77-specific CD8+ T cell expansion because this response was significantly reduced in Ccr2-/- mice, YopE was translocated into inflammatory DCs in vivo, inflammatory DCs purified from infected spleens activated YopE69-77-specific CD8+ T cells ex vivo and promoted the expansion of YopE69-77-specific CD8+ T cells in infected Ccr2-/- mice after adoptive transfer. A requirement for inflammatory DCs in producing a protective CD8+ T cell response to a bacterial antigen has not previously been demonstrated. Therefore, the production of YopE69-77-specific CD8+ T cells by inflammatory DCs that are injected with YopE during Y. pseudotuberculosis infection represents a novel mechanism for generating a massive and protective adaptive immune response.
在C57BL/6小鼠感染假结核耶尔森菌期间，会产生针对III型分泌系统效应蛋白YopE中一个保护性表位的异常强烈的CD8⁺ T细胞应答。在应答高峰期，高达50%的脾脏CD8⁺ T细胞识别表位YopE69 - 77。导致这种强烈CD8⁺ T细胞应答的病原体与宿主之间相互作用的特征尚不清楚。在此，我们使用在YopE产生、分泌和/或转运方面存在缺陷的假结核耶尔森菌菌株感染缺乏特定树突状细胞（DC）的野生型或突变小鼠。检测了器官中的细菌定植情况以及YopE向脾细胞的转运情况，并使用流式细胞术和四聚体染色来表征细胞免疫应答。我们发现，在强烈应答过程中产生的脾脏YopE69 - 77特异性CD8⁺ T细胞是多克隆的，并且是通过一条“转运依赖”途径产生的，该途径需要将YopE注入宿主细胞胞质溶胶中。此外，在一条“转运非依赖”途径中可以产生较小的YopE69 - 77特异性CD8⁺ T细胞应答（约为强烈扩增的10%），在该途径中，CD8α⁺ DC交叉呈递分泌的YopE。表达CCR2的炎性DC是YopE69 - 77特异性CD8⁺ T细胞强烈扩增所必需的，因为在Ccr2⁻/⁻小鼠中这种应答显著降低，YopE在体内转运到炎性DC中，从感染脾脏中纯化的炎性DC在体外激活YopE69 - 77特异性CD8⁺ T细胞，并在过继转移后促进感染的Ccr2⁻/⁻小鼠中YopE69 - 77特异性CD8⁺ T细胞的扩增。此前尚未证明炎性DC在产生针对细菌抗原的保护性CD8⁺ T细胞应答中具有必要性。因此，在假结核耶尔森菌感染期间，由注入YopE的炎性DC产生YopE69 - 77特异性CD8⁺ T细胞代表了一种产生大规模保护性适应性免疫应答的新机制。
