• Activated protein C protects from GvHD via PAR2/PAR3 signalling in regulatory T-cells.

      Ranjan, Satish; Goihl, Alexander; Kohli, Shrey; Gadi, Ihsan; Pierau, Mandy; Shahzad, Khurrum; Gupta, Dheerendra; Bock, Fabian; Wang, Hongjie; Shaikh, Haroon; Kähne, Thilo; Reinhold, Dirk; Bank, Ute; Zenclussen, Ana C; Niemz, Jana; Schnöder, Tina M; Brunner-Weinzierl, Monika; Fischer, Thomas; Kalinski, Thomas; Schraven, Burkhart; Luft, Thomas; Huehn, Jochen; Naumann, Michael; Heidel, Florian H; Isermann, Berend; Helmholtz Centre for infection research GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-21)
      Graft-vs.-host disease (GvHD) is a major complication of allogenic hematopoietic stem-cell(HSC) transplantation. GvHD is associated with loss of endothelial thrombomodulin, but the relevance of this for the adaptive immune response to transplanted HSCs remains unknown. Here we show that the protease-activated protein C (aPC), which is generated by thrombomodulin, ameliorates GvHD aPC restricts allogenic T-cell activation via the protease activated receptor (PAR)2/PAR3 heterodimer on regulatory T-cells (Tregs, CD4(+)FOXP3(+)). Preincubation of pan T-cells with aPC prior to transplantation increases the frequency of Tregs and protects from GvHD. Preincubation of human T-cells (HLA-DR4(-)CD4(+)) with aPC prior to transplantation into humanized (NSG-AB°DR4) mice ameliorates graft-vs.-host disease. The protective effect of aPC on GvHD does not compromise the graft vs. leukaemia effect in two independent tumor cell models. Ex vivo preincubation of T-cells with aPC, aPC-based therapies, or targeting PAR2/PAR3 on T-cells may provide a safe and effective approach to mitigate GvHD.Graft-vs.-host disease is a complication of allogenic hematopoietic stem cell transplantation, and is associated with endothelial dysfunction. Here the authors show that activated protein C signals via PAR2/PAR3 to expand Treg cells, mitigating the disease in mice.
    • Alloantigen-Induced Regulatory T Cells Generated in Presence of Vitamin C Display Enhanced Stability of Foxp3 Expression and Promote Skin Allograft Acceptance.

      Nikolouli, Eirini; Hardtke-Wolenski, Matthias; Hapke, Martin; Beckstette, Michael; Geffers, Robert; Floess, Stefan; Jaeckel, Elmar; Huehn, Jochen; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
      Regulatory T cells (Tregs) are critical for the maintenance of immune homeostasis and self-tolerance and can be therapeutically used for prevention of unwanted immune responses such as allotransplant rejection. Tregs are characterized by expression of the transcription factor Foxp3, and recent work suggests that epigenetic imprinting of Foxp3 and other Treg-specific epigenetic signatures genes is crucial for the stabilization of both Foxp3 expression and immunosuppressive properties within Tregs. Lately, vitamin C was reported to enhance the activity of enzymes of the ten-eleven translocation family, thereby fostering the demethylation of Foxp3 and other Treg-specific epigenetic signatures genes in developing Tregs. Here, we in vitro generated alloantigen-induced Foxp3(+) Tregs (allo-iTregs) in presence of vitamin C. Although vitamin C hardly influenced the transcriptome of allo-iTregs as revealed by RNA-seq, those vitamin C-treated allo-iTregs showed a more pronounced demethylation of Foxp3 and other Treg-specific epigenetic signatures genes accompanied with an enhanced stability of Foxp3 expression. Accordingly, when being tested in vivo in an allogeneic skin transplantation model, vitamin C-treated allo-iTregs showed a superior suppressive capacity. Together, our results pave the way for the establishment of novel protocols for the in vitro generation of alloantigen-induced Foxp3(+) Tregs for therapeutic use in transplantation medicine.
    • CD8+ Foxp3+ T cells share developmental and phenotypic features with classical CD4+ Foxp3+ regulatory T cells but lack potent suppressive activity.

      Mayer, Christian T; Floess, Stefan; Baru, Abdul Mannan; Lahl, Katharina; Huehn, Jochen; Sparwasser, Tim (2011-03)
      "Suppressor T cells" were historically defined within the CD8(+) T-cell compartment and recent studies have highlighted several naturally occurring CD8(+) Foxp3(-) Treg populations. However, the relevance of CD8(+) Foxp3(+) T cells, which represent a minor population in both thymi and secondary lymphoid organs of nonmanipulated mice, remains unclear. We here demonstrate that de novo Foxp3 induction in peripheral CD8(+) Foxp3(-) T cells is counter-regulated by DC-mediated co-stimulation via CD80/CD86. CD8(+) Foxp3(+) T cells fail to develop in TCR-transgenic mice with Rag1(-/-) background, similar to classical CD4(+) Foxp3(+) Tregs. Notably, both naturally occurring and induced CD8(+) Foxp3(+) T cells express bona fide Treg markers including CD25, GITR, CTLA4 and CD103, and show defective IFN-γ production upon restimulation when compared with their CD8(+) Foxp3(-) counterparts. However, utilizing DEREG transgenic mice for the isolation of Foxp3(+) cells by eGFP reporter expression, we demonstrate that induced CD8(+) Foxp3(+) T cells similar to activated CD8(+) Foxp3(-) T cells only mildly suppress T-cell proliferation and IFN-γ production. We therefore categorize CD8(+) Foxp3(+) T cells as a tightly controlled population sharing certain developmental and phenotypic properties with classical CD4(+) Foxp3(+) Tregs, but lacking potent suppressive activity.
    • Development of a unique epigenetic signature during in vivo Th17 differentiation.

      Yang, Bi-Huei; Floess, Stefan; Hagemann, Stefanie; Deyneko, Igor V; Groebe, Lothar; Pezoldt, Joern; Sparwasser, Tim; Lochner, Matthias; Huehn, Jochen; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015-02-18)
      Activated naive CD4(+) T cells are highly plastic cells that can differentiate into various T helper (Th) cell fates characterized by the expression of effector cytokines like IFN-γ (Th1), IL-4 (Th2) or IL-17A (Th17). Although previous studies have demonstrated that epigenetic mechanisms including DNA demethylation can stabilize effector cytokine expression, a comprehensive analysis of the changes in the DNA methylation pattern during differentiation of naive T cells into Th cell subsets is lacking. Hence, we here performed a genome-wide methylome analysis of ex vivo isolated naive CD4(+) T cells, Th1 and Th17 cells. We could demonstrate that naive CD4(+) T cells share more demethylated regions with Th17 cells when compared to Th1 cells, and that overall Th17 cells display the highest number of demethylated regions, findings which are in line with the previously reported plasticity of Th17 cells. We could identify seven regions located in Il17a, Zfp362, Ccr6, Acsbg1, Dpp4, Rora and Dclk1 showing pronounced demethylation selectively in ex vivo isolated Th17 cells when compared to other ex vivo isolated Th cell subsets and in vitro generated Th17 cells, suggesting that this unique epigenetic signature allows identifying and functionally characterizing in vivo generated Th17 cells.
    • Effector molecules released by Th1 but not Th17 cells drive an M1 response in microglia.

      Prajeeth, Chittappen K; Löhr, Kirsten; Floess, Stefan; Zimmermann, Julian; Ulrich, Reiner; Gudi, Viktoria; Beineke, Andreas; Baumgärtner, Wolfgang; Müller, Marcus; Huehn, Jochen; Stangel, Martin (2014-03)
      Microglia act as sensors of inflammation in the central nervous system (CNS) and respond to many stimuli. Other key players in neuroinflammatory diseases are CD4+ T helper cell (Th) subsets that characteristically secrete IFN-γ (Th1) or IL-17 (Th17). However, the potential of a distinct cytokine milieu generated by these effector T cell subsets to modulate microglial phenotype and function is poorly understood. We therefore investigated the ability of factors secreted by Th1 and Th17 cells to induce microglial activation. In vitro experiments wherein microglia were cultured in the presence of supernatants derived from polarized Th1 or Th17 cultures, revealed that Th1-associated factors could directly activate and trigger a proinflammatory M1-type gene expression profile in microglia that was cell-cell contact independent, whereas Th17 cells or its associated factors did not have any direct influence on microglia. To assess the effects of the key Th17 effector cytokine IL-17A in vivo we used transgenic mice in which IL-17A is specifically expressed in astrocytes. Flow cytometric and histological analysis revealed only subtle changes in the phenotype of microglia suggesting only minimal effects of constitutively produced IL-17A on microglia in vivo. Neither IL-23 signaling nor addition of GM-CSF, a recently described effector molecule of Th17 cells, changed the incapacity of Th17 cells to activate microglia. These findings demonstrate a potent effect of Th1 cells on microglia, however, the mechanism of how Th17 cells achieve their effect in CNS inflammation remains unclear.
    • Effectors of Th1 and Th17 cells act on astrocytes and augment their neuroinflammatory properties.

      Prajeeth, Chittappen K; Kronisch, Julius; Khorooshi, Reza; Knier, Benjamin; Toft-Hansen, Henrik; Gudi, Viktoria; Floess, Stefan; Huehn, Jochen; Owens, Trevor; Korn, Thomas; Stangel, Martin; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-10-16)
      Autoreactive Th1 and Th17 cells are believed to mediate the pathology of multiple sclerosis in the central nervous system (CNS). Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of the neuroinflammation. Previously, we have shown that only Th1 but not Th17 effectors activate microglia. However, it is not clear which cells are targets of Th17 effectors in the CNS.
    • Effectors of Th1 and Th17 cells act on astrocytes and augment their neuroinflammatory properties.

      Prajeeth, Chittappen K; Kronisch, Julius; Khorooshi, Reza; Knier, Benjamin; Toft-Hansen, Henrik; Gudi, Viktoria; Floess, Stefan; Huehn, Jochen; Owens, Trevor; Korn, Thomas; Stangel, Martin; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (2017-10-16)
      Autoreactive Th1 and Th17 cells are believed to mediate the pathology of multiple sclerosis in the central nervous system (CNS). Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of the neuroinflammation. Previously, we have shown that only Th1 but not Th17 effectors activate microglia. However, it is not clear which cells are targets of Th17 effectors in the CNS. To understand the effects driven by Th17 cells in the CNS, we induced experimental autoimmune encephalomyelitis in wild-type mice and CD4 We observed in α4-deficient mice weak microglial activation but comparable astrogliosis to that of wild-type mice in the regions of the brain populated with Th17 infiltrates, suggesting that Th17 cells target astrocytes and not microglia. In vitro, in response to supernatants from Th1 and Th17 cultures, astrocytes showed altered expression of neurotrophic factors, pro-inflammatory cytokines and chemokines. Furthermore, increased expression of chemokines in Th1- and Th17-treated astrocytes enhanced recruitment of microglia and transendothelial migration of Th17 cells in vitro. Our results demonstrate the delicate interaction between T cell subsets and glial cells and how they communicate to mediate their effects. Effectors of Th1 act on both microglia and astrocytes whereas Th17 effectors preferentially target astrocytes to promote neuroinflammation.
    • Epigenetic modification of the human CCR6 gene is associated with stable CCR6 expression in T cells.

      Steinfelder, Svenja; Floess, Stefan; Engelbert, Dirk; Haeringer, Barbara; Baron, Udo; Rivino, Laura; Steckel, Bodo; Gruetzkau, Andreas; Olek, Sven; Geginat, Jens; Huehn, Jochen; Hamann, Alf; Dept. of experimental immunology, Helmholtz Centre for infection reseach, Inhoffenstr. 7, D38124 Braunschweig, Germany. (2011-03-10)
      CCR6 is a chemokine receptor expressed on Th17 cells and regulatory T cells that is induced by T-cell priming with certain cytokines, but how its expression and stability are regulated at the molecular level is largely unknown. Here, we identified and characterized a noncoding region of the human CCR6 locus that displayed unmethylated CpG motifs (differentially methylated region [DMR]) selectively in CCR6(+) lymphocytes. CCR6 expression on circulating CD4(+) T cells was stable on cytokine-induced proliferation but partially down-regulated on T-cell receptor stimulation. However, CCR6 down-regulation was mostly transient, and the DMR within the CCR6 locus remained demethylated. Notably, in vitro induction of CCR6 expression with cytokines in T-cell receptor-activated naive CD4(+) T cells was not associated with a demethylated DMR and resulted in unstable CCR6 expression. Conversely, treatment with the DNA methylation inhibitor 5'-azacytidine induced demethylation of the DMR and led to increased and stable CCR6 expression. Finally, when cloned into a reporter gene plasmid, the DMR displayed transcriptional activity in memory T cells that was suppressed by DNA methylation. In summary, we have identified a noncoding region of the human CCR6 gene with methylation-sensitive transcriptional activity in CCR6(+) T cells that controls stable CCR6 expression via epigenetic mechanisms.
    • Epigenetic orchestration of thymic Treg cell development.

      Beyer, Marc; Huehn, Jochen; Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-01-19)
    • Extracellular NAD+ shapes the Foxp3+ regulatory T cell compartment through the ART2-P2X7 pathway.

      Hubert, Sandra; Rissiek, Björn; Klages, Katjana; Huehn, Jochen; Sparwasser, Tim; Haag, Friedrich; Koch-Nolte, Friedrich; Boyer, Olivier; Seman, Michel; Adriouch, Sahil; Institut National de la Santé et de la Recherche Medicale, U905, 76183 Rouen, France. (2010-11-22)
      CD4(+)CD25(+)FoxP3(+) regulatory T cells (T reg cells) play a major role in the control of immune responses but the factors controlling their homeostasis and function remain poorly characterized. Nicotinamide adenine dinucleotide (NAD(+)) released during cell damage or inflammation results in ART2.2-mediated ADP-ribosylation of the cytolytic P2X7 receptor on T cells. We show that T reg cells express the ART2.2 enzyme and high levels of P2X7 and that T reg cells can be depleted by intravenous injection of NAD(+). Moreover, lower T reg cell numbers are found in mice deficient for the NAD-hydrolase CD38 than in wild-type, P2X7-deficient, or ART2-deficient mice, indicating a role for extracellular NAD(+) in T reg cell homeostasis. Even routine cell preparation leads to release of NAD(+) in sufficient quantities to profoundly affect T reg cell viability, phenotype, and function. We demonstrate that T reg cells can be protected from the deleterious effects of NAD(+) by an inhibitory ART2.2-specific single domain antibody. Furthermore, selective depletion of T reg cells by systemic administration of NAD(+) can be used to promote an antitumor response in several mouse tumor models. Collectively, our data demonstrate that NAD(+) influences survival, phenotype, and function of T reg cells and provide proof of principle that acting on the ART2-P2X7 pathway represents a new strategy to manipulate T reg cells in vivo.
    • Foxp3(+) T cells expressing RORγt represent a stable regulatory T-cell effector lineage with enhanced suppressive capacity during intestinal inflammation.

      Yang, B-H; Hagemann, S; Mamareli, P; Lauer, U; Hoffmann, U; Beckstette, M; Föhse, L; Prinz, I; Pezoldt, J; Suerbaum, S; Sparwasser, Tim; Hamann, A; Floess, S; Huehn, J; Lochner, M; Helmholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2016-03)
      Foxp3 (forkhead box P3 transcription factor)-expressing regulatory T cells (Tregs) are essential for immunological tolerance, best illustrated by uncontrolled effector T-cell responses and autoimmunity upon loss of Foxp3 expression. Tregs can adopt specific effector phenotypes upon activation, reflecting the diversity of functional demands in the different tissues of the body. Here, we report that Foxp3(+)CD4(+) T cells coexpressing retinoic acid-related orphan receptor-γt (RORγt), the master transcription factor for T helper type 17 (Th17) cells, represent a stable effector Treg lineage. Transcriptomic and epigenetic profiling revealed that Foxp3(+)RORγt(+) T cells display signatures of both Tregs and Th17 cells, although the degree of similarity was higher to Foxp3(+)RORγt(-) Tregs than to Foxp3(-)RORγt(+) T cells. Importantly, Foxp3(+)RORγt(+) T cells were significantly demethylated at Treg-specific epigenetic signature genes such as Foxp3, Ctla-4, Gitr, Eos, and Helios, suggesting that these cells have a stable regulatory rather than inflammatory function. Indeed, adoptive transfer of Foxp3(+)RORγt(+) T cells in the T-cell transfer colitis model confirmed their Treg function and lineage stability in vivo, and revealed an enhanced suppressive capacity as compared with Foxp3(+)RORγt(-) Tregs. Thus, our data suggest that RORγt expression in Tregs contributes to an optimal suppressive capacity during gut-specific immune responses, rendering Foxp3(+)RORγt(+) T cells as an important effector Treg subset in the intestinal system.
    • Gut memories do not fade: epigenetic regulation of lasting gut homing receptor expression in CD4(+) memory T cells.

      Szilagyi, B A; Triebus, J; Kressler, C; de Almeida, M; Tierling, S; Durek, P; Mardahl, M; Szilagyi, A; Floess, S; Huehn, J; Syrbe, U; Walter, J; Polansky, J K; Hamann, A; Helmholtz-Zentrum für Infektionsforschhung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-11)
      The concept of a "topographical memory" in lymphocytes implies a stable expression of homing receptors mediating trafficking of lymphocytes back to the tissue of initial activation. However, a significant plasticity of the gut-homing receptor α4β7 was found in CD8(+) T cells, questioning the concept. We now demonstrate that α4β7 expression in murine CD4(+) memory T cells is, in contrast, imprinted and remains stable in the absence of the inducing factor retinoic acid (RA) or other stimuli from mucosal environments. Repetitive rounds of RA treatment enhanced the stability of de novo induced α4β7. A novel enhancer element in the murine Itga4 locus was identified that showed, correlating to stability, selective DNA demethylation in mucosa-seeking memory cells and methylation-dependent transcriptional activity in a reporter gene assay. This implies that epigenetic mechanisms contribute to the stabilization of α4β7 expression. Analogous DNA methylation patterns could be observed in the human ITGA4 locus, suggesting that its epigenetic regulation is conserved between mice and men. These data prove that mucosa-specific homing mediated by α4β7 is imprinted in CD4(+) memory T cells, reinstating the validity of the concept of "topographical memory" for mucosal tissues, and imply a critical role of epigenetic mechanisms.
    • Helicobacter pylori and its secreted immunomodulator VacA protect against anaphylaxis in experimental models of food allergy.

      Kyburz, Andreas; Urban, Sabine; Altobelli, Aleksandra; Floess, Stefan; Huehn, Jochen; Cover, Timothy L; Müller, Anne; Helmholtz Centre for infection research GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-12)
      Food allergy is an increasingly common health problem in Western populations. Epidemiological studies have suggested both positive and negative associations between food allergy and infection with the gastric bacterium Helicobacter pylori.
    • IFN-γ Producing Th1 Cells Induce Different Transcriptional Profiles in Microglia and Astrocytes.

      Prajeeth, Chittappen K; Dittrich-Breiholz, Oliver; Talbot, Steven R; Robert, Philippe A; Huehn, Jochen; Stangel, Martin; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.; BRICS, Braunschweiger Zentrum für Systembiologie, Rebenring 56,38106 Braunschweig, Germany. (2018-01-01)
      Autoreactive T cells that infiltrate into the central nervous system (CNS) are believed to have a significant role in mediating the pathology of neuroinflammatory diseases like multiple sclerosis. Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of neuroinflammatory processes. Our previous work demonstrated that effectors secreted by Th1 and Th17 cells have different capacities to influence the phenotype and function of glial cells. We have shown that Th1-derived effectors altered the phenotype and function of both microglia and astrocytes whereas Th17-derived effectors induced direct effects only on astrocytes but not on microglia. Here we investigated if effector molecules associated with IFN-γ producing Th1 cells induced different gene expression profiles in microglia and astrocytes. We performed a microarray analysis of RNA isolated from microglia and astrocytes treated with medium and Th-derived culture supernatants and compared the gene expression data. By using the criteria of 2-fold change and a false discovery rate of 0.01 (corrected
    • Impact of CCR7 on T-Cell Response and Susceptibility to Yersinia pseudotuberculosis Infection.

      Pezoldt, Joern; Pisano, Fabio; Heine, Wiebke; Pasztoi, Maria; Rosenheinrich, Maik; Nuss, Aaron M; Pils, Marina C; Prinz, Immo; Förster, Reinhold; Huehn, Jochen; Dersch, Petra; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-09-15)
      To successfully limit pathogen dissemination, an immunological link between the entry tissue of the pathogen and the underlying secondary lymphoid organs (SLOs) needs to be established to prime adaptive immune responses. Here, the prerequisite of CCR7 to mount host immune responses within SLOs during gastrointestinal Yersinia pseudotuberculosis infection to limit pathogen spread was investigated.
    • Inhibition of the JAK/STAT Signaling Pathway in Regulatory T Cells Reveals a Very Dynamic Regulation of Foxp3 Expression.

      Goldstein, Jérémie D; Burlion, Aude; Zaragoza, Bruno; Sendeyo, Kélhia; Polansky, Julia K; Huehn, Jochen; Piaggio, Eliane; Salomon, Benoit L; Marodon, Gilles; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      The IL-2/JAK3/STAT-5 signaling pathway is involved on the initiation and maintenance of the transcription factor Foxp3 in regulatory T cells (Treg) and has been associated with demethylation of the intronic Conserved Non Coding Sequence-2 (CNS2). However, the role of the JAK/STAT pathway in controlling Foxp3 in the short term has been poorly investigated. Using two different JAK/STAT pharmacological inhibitors, we observed a detectable loss of Foxp3 after 10 min. of treatment that affected 70% of the cells after one hour. Using cycloheximide, a general inhibitor of mRNA translation, we determined that Foxp3, but not CD25, has a high turnover in IL-2 stimulated Treg. This reduction was correlated with a rapid reduction of Foxp3 mRNA. This loss of Foxp3 was associated with a loss in STAT-5 binding to the CNS2, which however remains demethylated. Consequently, Foxp3 expression returns to normal level upon restoration of basal JAK/STAT signaling in vivo. Reduced expression of several genes defining Treg identity was also observed upon treatment. Thus, our results demonstrate that Foxp3 has a rapid turn over in Treg partly controlled at the transcriptional level by the JAK/STAT pathway.
    • Intact interleukin-10 receptor signaling protects from hippocampal damage elicited by experimental neurotropic virus infection of SJL mice.

      Uhde, Ann-Kathrin; Ciurkiewicz, Malgorzata; Herder, Vanessa; Khan, Muhammad Akram; Hensel, Niko; Claus, Peter; Beckstette, Michael; Teich, René; Floess, Stefan; Baumgärtner, Wolfgang; Jung, Klaus; Huehn, Jochen; Beineke, Andreas; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-04-17)
      Theiler's murine encephalomyelitis virus (TMEV) infection represents an experimental mouse model to study hippocampal damage induced by neurotropic viruses. IL-10 is a pleiotropic cytokine with profound anti-inflammatory properties, which critically controls immune homeostasis. In order to analyze IL-10R signaling following virus-induced polioencephalitis, SJL mice were intracerebrally infected with TMEV. RNA-based next generation sequencing revealed an up-regulation of Il10, Il10rα and further genes involved in IL-10 downstream signaling, including Jak1, Socs3 and Stat3 in the brain upon infection. Subsequent antibody-mediated blockade of IL-10R signaling led to enhanced hippocampal damage with neuronal loss and increased recruitment of CD3+ T cells, CD45R+ B cells and an up-regulation of Il1α mRNA. Increased expression of Tgfβ and Foxp3 as well as accumulation of Foxp3+ regulatory T cells and arginase-1+ macrophages/microglia was detected in the hippocampus, representing a potential compensatory mechanism following disturbed IL-10R signaling. Additionally, an increased peripheral Chi3l3 expression was found in spleens of infected mice, which may embody reactive regulatory mechanisms for prevention of excessive immunopathology. The present study highlights the importance of IL-10R signaling for immune regulation and its neuroprotective properties in the context of an acute neurotropic virus infection.
    • The invasin D protein fromYersinia pseudotuberculosisselectively binds the Fab region of host antibodies and affects colonization of the intestine.

      Sadana, Pooja; Geyer, Rebecca; Pezoldt, Joern; Helmsing, Saskia; Huehn, Jochen; Hust, Michael; Dersch, Petra; Scrima, Andrea; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-03-13)
      Yersinia pseudotuberculosis is a Gram-negative bacterium and zoonotic pathogen responsible for a wide range of diseases, ranging from mild diarrhea, enterocolitis, lymphatic adenitis to persistent local inflammation. TheY. pseudotuberculosisinvasin D (InvD) molecule belongs to the invasin (InvA)-type autotransporter proteins, but its structure and function remain unknown. In this study, we present the first crystal structure of InvD, analyzed its expression and function in a murine infection model, and identified its target molecule in the host. We found that InvD is induced at 37°C and expressed in vivo2-4 days after infection, indicating that InvD is a virulence factor. During infection, InvD was expressed in all parts of the intestinal tract, but not in deeper lymphoid tissues. The crystal structure of the C-terminal adhesion domain of InvD revealed a distinct Ig-related fold, that, apart from the canonical β-sheets, comprises various modifications of and insertions into the Ig-core structure. We identified the Fab fragment of host-derived IgG/IgA antibodies as the target of the adhesion domain. Phage display panning and flow cytometry data further revealed that InvD exhibits a preferential binding specificity toward antibodies with VH3/VK1 variable domains and that it is specifically recruited to a subset of B cells. This finding suggests that InvD modulates Ig functions in the intestine and affects direct interactions with a subset of cell surface-exposed B-cell receptors. In summary, our results provide extensive insights into the structure of InvD and its specific interaction with the target molecule in the host.
    • Limited role of regulatory T cells during acute Theiler virus-induced encephalitis in resistant C57BL/6 mice

      Prajeeth, Chittappen K; Beineke, Andreas; Iskandar, Cut D; Gudi, Viktoria; Herder, Vanessa; Gerhauser, Ingo; Haist, Verena; Teich, René; Huehn, Jochen; Baumgärtner, Wolfgang; Stangel, Martin (2014-11-13)
      Abstract Background Theiler’s murine encephalomyelitis virus (TMEV) infection represents a commonly used infectious animal model to study various aspects of the pathogenesis of multiple sclerosis (MS). In susceptible SJL mice, dominant activity of Foxp3+ CD4+ regulatory T cells (Tregs) in the CNS partly contributes to viral persistence and progressive demyelination. On the other hand, resistant C57BL/6 mice rapidly clear the virus by mounting a strong antiviral immune response. However, very little is known about the role of Tregs in regulating antiviral responses during acute encephalitis in resistant mouse strains. Methods In this study, we used DEREG mice that express the diphtheria toxin (DT) receptor under control of the foxp3 locus to selectively deplete Foxp3+ Tregs by injection of DT prior to infection and studied the effect of Treg depletion on the course of acute Theiler’s murine encephalomyelitis (TME). Results As expected, DEREG mice that are on a C57BL/6 background were resistant to TMEV infection and cleared the virus within days of infection, regardless of the presence or absence of Tregs. Nevertheless, in the absence of Tregs we observed priming of stronger effector T cell responses in the periphery, which subsequently resulted in a transient increase in the frequency of IFNγ-producing T cells in the brain at an early stage of infection. Histological and flow cytometric analysis revealed that this transiently increased frequency of brain-infiltrating IFNγ-producing T cells in Treg-depleted mice neither led to an augmented antiviral response nor enhanced inflammation-mediated tissue damage. Intriguingly, Treg depletion did not change the expression of IL-10 in the infected brain, which might play a role for dampening the inflammatory damage caused by the increased number of effector T cells. Conclusion We therefore propose that unlike susceptible mice strains, interfering with the Treg compartment of resistant mice only has negligible effects on virus-induced pathologies in the CNS. Furthermore, in the absence of Tregs, local anti-inflammatory mechanisms might limit the extent of damage caused by strong anti-viral response in the CNS.
    • Limited role of regulatory T cells during acute Theiler virus-induced encephalitis in resistant C57BL/6 mice.

      Prajeeth, Chittappen K; Beineke, Andreas; Iskandar, Cut Dahlia; Gudi, Viktoria; Herder, Vanessa; Gerhauser, Ingo; Haist, Verena; Teich, René; Huehn, Jochen; Baumgärtner, Wolfgang; Stangel, Martin; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2014)
      Theiler's murine encephalomyelitis virus (TMEV) infection represents a commonly used infectious animal model to study various aspects of the pathogenesis of multiple sclerosis (MS). In susceptible SJL mice, dominant activity of Foxp3(+) CD4(+) regulatory T cells (Tregs) in the CNS partly contributes to viral persistence and progressive demyelination. On the other hand, resistant C57BL/6 mice rapidly clear the virus by mounting a strong antiviral immune response. However, very little is known about the role of Tregs in regulating antiviral responses during acute encephalitis in resistant mouse strains.