CCR2+ Inflammatory Dendritic Cells and Translocation of Antigen by Type III Secretion Are Required for the Exceptionally Large CD8+ T Cell Response to the Protective YopE69-77 Epitope during Yersinia Infection

Abstract

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.

CD8 + T cells specific to a single Yersinia pseudotuberculosis epitope restrict bacterial replication in the liver but fail to provide sterilizing immunity

“…Mice intranasally immunized with YopE, which contain a dominant CD8 epitope, YopE 69-77 , (Lin et al, 2011) were only partially protected from oral Y. pseudotuberculosis challenge, with 36% of the mice unable to survive the challenge out to 28 days (Lin et al, 2011; Zhang et al, 2015). Taken together, with our data demonstrating tissue-specific immunity, these data suggest that CD8+ T cell driven immunity, as previously reported (Bergman et al, 2009), requires a polyclonal response.…”

Yersinia pseudotuberculosis supports Th17 differentiation and limits de novo regulatory T cell induction by directly interfering with T cell receptor signaling

“…Besides studies underpinning the importance of CD8 + T cells in control of Yersinia infection [8, 11, 12], there are only few studies focusing on CD4 + T helper cell responses. These studies suggest the involvement of IFNγ-producing proinflammatory Th1 cells in protection against Yersinia [13], and report a capacity of CD4 + T cells in responding to Y. pseudotuberculosis superantigens in an MHCII-dependent manner [14].…”

“…While innate immunity represents a well-characterized part of the immune response against Y. pseudotuberculosis , involving neutrophils, macrophages, dendritic cells (DCs), and natural killer cells [ 7 – 10 ], the role of the adaptive immune system in combatting invading Yersiniae is only incompletely understood. Besides studies underpinning the importance of CD8 + T cells in control of Yersinia infection [ 8 , 11 , 12 ], there are only few studies focusing on CD4 + T helper cell responses. These studies suggest the involvement of IFNγ-producing proinflammatory Th1 cells in protection against Yersinia [ 13 ], and report a capacity of CD4 + T cells in responding to Y. pseudotuberculosis superantigens in an MHCII-dependent manner [ 14 ].…”

CCR2 + Inflammatory Monocytes Are Recruited to Yersinia pseudotuberculosis Pyogranulomas and Dictate Adaptive Responses at the Expense of Innate Immunity during Oral Infection

“…We previously employed intravenous (i.v.) infection of mice with attenuated Y. pseudotuberculosis to investigate the features of YopE and the host immune response that are important for the production of large numbers of YopE 69 -77 -specific CD8 ϩ T cells (30,31). An attenuated yopE GAP mutant was used for these studies because we found that YopE catalytic activity was not required for the large YopE 69 -77 -specific CD8 ϩ T cell response (30).…”

“…An attenuated yopE GAP mutant was used for these studies because we found that YopE catalytic activity was not required for the large YopE 69 -77 -specific CD8 ϩ T cell response (30). Interestingly, CCR2 Ϫ/Ϫ mice, which are defective for the recruitment of IMs out of bone marrow, had a significant defect in the production of YopE 69 -77 -specific CD8 ϩ T cells when they were infected with a Y. pseudotuberculosis yopE GAP mutant (31). Moreover, CCR2 Ϫ/Ϫ mice were more susceptible to lethal infection than wild-type controls, when they were infected with the yopE GAP mutant, suggesting that IMs are important for the control of Y. pseudotuberculosis in addition to their role in the production of YopE 69 -77 -specific CD8 ϩ T cells (31).…”