Recent Submissions

  • Beware the intruder: Real time observation of infiltrated neutrophils and neutrophil-Microglia interaction during stroke in vivo.

    Neumann, Jens; Henneberg, Sophie; von Kenne, Susanne; Nolte, Niklas; Müller, Andreas J; Schraven, Burkhart; Görtler, Michael W; Reymann, Klaus G; Gunzer, Matthias; Riek-Burchardt, Monika; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018)
    Inflammation plays an important role in the pathogenesis of ischemic stroke including an acute and prolonged inflammatory process. The role of neutrophil granulocytes as first driver of the immune reaction from the blood site is under debate due to controversial findings. In bone marrow chimeric mice we were able to study the dynamics of tdTomato-expressing neutrophils and GFP-expressing microglia after photothrombosis using intravital two-photon microscopy. We demonstrate the infiltration of neutrophils into the brain parenchyma and confirm a long-lasting contact between neutrophils and microglia as well as an uptake of neutrophils by microglia clearing the brain from peripheral immune cells.
  • Targeted antigen delivery to dendritic cells elicits robust antiviral T cell-mediated immunity in the liver.

    Volckmar, Julia; Gereke, Marcus; Ebensen, Thomas; Riese, Peggy; Philipsen, Lars; Lienenklaus, Stefan; Wohlleber, Dirk; Klopfleisch, Robert; Stegemann-Koniszewski, Sabine; Müller, Andreas J; Gruber, Achim D; Knolle, Percy; Guzman, Carlos A; Bruder, Dunja; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-03-07)
    Hepatotropic viruses such as hepatitis C virus cause life-threatening chronic liver infections in millions of people worldwide. Targeted in vivo antigen-delivery to cross-presenting dendritic cells (DCs) has proven to be extraordinarily efficient in stimulating antigen-specific T cell responses. To determine whether this approach would as well be suitable to induce local antiviral effector T cells in the liver we compared different vaccine formulations based on either the targeting of DEC-205 or TLR2/6 on cross-presenting DCs or formulations not involving in vivo DC targeting. As read-outs we used in vivo hepatotropic adenovirus challenge, histology and automated multidimensional fluorescence microscopy (MELC). We show that targeted in vivo antigen delivery to cross-presenting DCs is highly effective in inducing antiviral CTLs capable of eliminating virus-infected hepatocytes, while control vaccine formulation not involving DC targeting failed to induce immunity against hepatotropic virus. Moreover, we observed distinct patterns of CD8+ T cell interaction with virus-infected and apoptotic hepatocytes in the two DC-targeting groups suggesting that the different vaccine formulations may stimulate distinct types of effector functions. Our findings represent an important step toward the future development of vaccines against hepatotropic viruses and the treatment of patients with hepatic virus infection after liver transplantation to avoid reinfection.
  • A mathematical model of the impact of insulin secretion dynamics on selective hepatic insulin resistance.

    Zhao, Gang; Wirth, Dagmar; Schmitz, Ingo; Meyer-Hermann, Michael; Braunschweiger Zentrum für Systembiologie, Rebenring 56, 38106, Germany. (2017-11-08)
    Physiological insulin secretion exhibits various temporal patterns, the dysregulation of which is involved in diabetes development. We analyzed the impact of first-phase and pulsatile insulin release on glucose and lipid control with various hepatic insulin signaling networks. The mathematical model suggests that atypical protein kinase C (aPKC) undergoes a bistable switch-on and switch-off, under the control of insulin receptor substrate 2 (IRS2). The activation of IRS1 and IRS2 is temporally separated due to the inhibition of IRS1 by aPKC. The model further shows that the timing of aPKC switch-off is delayed by reduced first-phase insulin and reduced amplitude of insulin pulses. Based on these findings, we propose a sequential model of postprandial hepatic control of glucose and lipid by insulin, according to which delayed aPKC switch-off contributes to selective hepatic insulin resistance, which is a long-standing paradox in the field.
  • TCR signalling network organization at the immunological synapses of murine regulatory T cells.

    van Ham, Marco; Teich, René; Philipsen, Lars; Niemz, Jana; Amsberg, Nicole; Wissing, Josef; Nimtz, Manfred; Gröbe, Lothar; Kliche, Stefanie; Thiel, Nadine; Klawonn, Frank; Hubo, Mario; Jonuleit, Helmut; Reichardt, Peter; Müller, Andreas J; Huehn, Jochen; Jänsch, Lothar; Helmholtz-Zetrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-08-17)
    Regulatory T (Treg) cells require T-cell receptor (TCR) signalling to exert their immunosuppressive activity, but the precise organization of the TCR signalling network compared to conventional T (Tconv) cells remains elusive. By using accurate mass spectrometry and multi-epitope ligand cartography (MELC) we characterized TCR signalling and recruitment of TCR signalling components to the immunological synapse (IS) in Treg cells and Tconv cells. With the exception of Themis which we detected in lower amounts in Treg cells, other major TCR signalling components were found equally abundant, however, their phosphorylation-status notably discriminates Treg cells from Tconv cells. Overall, this study identified 121 Treg cell-specific phosphorylations. Short-term triggering of T cell subsets via CD3 and CD28 widely harmonized these variations with the exception of eleven TCR signalling components that mainly regulate cytoskeleton dynamics and molecular transport. Accordingly, conjugation with B cells indeed caused variant cellular morphology and revealed a Treg cell-specific recruitment of TCR signalling components such as PKCθ, PLCγ1 and ZAP70 as well as B cell-derived CD86 into the IS. Together, results from this study support the existence of a Treg cell-specific IS and suggest Treg cell-specific cytoskeleton dynamics as a novel determinant for the unique functional properties of Treg cells.
  • UL36 Rescues Apoptosis Inhibition and In vivo Replication of a Chimeric MCMV Lacking the M36 Gene.

    Chaudhry, M Zeeshan; Kasmapour, Bahram; Plaza-Sirvent, Carlos; Bajagic, Milica; Casalegno Garduño, Rosaely; Borkner, Lisa; Lenac Roviš, Tihana; Scrima, Andrea; Jonjic, Stipan; Schmitz, Ingo; Cicin-Sain, Luka; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
    Apoptosis is an important defense mechanism mounted by the immune system to control virus replication. Hence, cytomegaloviruses (CMV) evolved and acquired numerous anti-apoptotic genes. The product of the human CMV (HCMV) UL36 gene, pUL36 (also known as vICA), binds to pro-caspase-8, thus inhibiting death-receptor apoptosis and enabling viral replication in differentiated THP-1 cells. In vivo studies of the function of HCMV genes are severely limited due to the strict host specificity of cytomegaloviruses, but CMV orthologues that co-evolved with other species allow the experimental study of CMV biology in vivo. The mouse CMV (MCMV) homolog of the UL36 gene is called M36, and its protein product (pM36) is a functional homolog of vICA that binds to murine caspase-8 and inhibits its activation. M36-deficient MCMV is severely growth impaired in macrophages and in vivo. Here we show that pUL36 binds to the murine pro-caspase-8, and that UL36 expression inhibits death-receptor apoptosis in murine cells and can replace M36 to allow MCMV growth in vitro and in vivo. We generated a chimeric MCMV expressing the UL36 ORF sequence instead of the M36 one. The newly generated MCMV(UL36) inhibited apoptosis in macrophage lines RAW 264.7, J774A.1, and IC-21 and its growth was rescued to wild type levels. Similarly, growth was rescued in vivo in the liver and spleen, but only partially in the salivary glands of BALB/c and C57BL/6 mice. In conclusion, we determined that an immune-evasive HCMV gene is conserved enough to functionally replace its MCMV counterpart and thus allow its study in an in vivo setting. As UL36 and M36 proteins engage the same molecular host target, our newly developed model can facilitate studies of anti-viral compounds targeting pUL36 in vivo.
  • 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.
  • A highly conserved redox-active Mx(2)CWx(6)R motif regulates Zap70 stability and activity.

    Thurm, Christoph; Poltorak, Mateusz P; Reimer, Elisa; Brinkmann, Melanie M; Leichert, Lars; Schraven, Burkhart; Simeoni, Luca; Helmholtz Centre of infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-05-09)
    ζ-associated protein of 70 kDa (Zap70) is crucial for T-cell receptor (TCR) signaling. Loss of Zap70 in both humans and mice results in severe immunodeficiency. On the other hand, the expression of Zap70 in B-cell malignancies correlates with the severity of the disease. Because of its role in immune-related disorders, Zap70 has become a therapeutic target for the treatment of human diseases. It is well-established that the activity/expression of Zap70 is regulated by post-translational modifications of crucial amino acids including the phosphorylation of tyrosines and the ubiquitination of lysines. Here, we have investigated whether also oxidation of cysteine residues regulates Zap70 functions. We have identified C575 as a major sulfenylation site of Zap70. A C575A substitution results in protein instability, reduced activity, and increased dependency on the Hsp90/Cdc37 chaperone system. Indeed, Cdc37 overexpression reconstituted partially the expression but fully the function of Zap70C575A. C575 lies within a Mx(2)CWx(6)R motif which is highly conserved among almost all human tyrosine kinases. Mutation of any of the conserved amino acids, but not of a non-conserved residue preceding the cysteine, also results in Zap70 instability. Collectively, we have identified a new redox-active motif which is crucial for the regulation of Zap70 stability/activity. We believe that this motif has the potential to become a novel target for the development of therapeutic tools to modulate the expression/activity of kinases.
  • HIPP neurons in the dentate gyrus mediate the cholinergic modulation of background context memory salience.

    Raza, Syed Ahsan; Albrecht, Anne; Çalışkan, Gürsel; Müller, Bettina; Demiray, Yunus Emre; Ludewig, Susann; Meis, Susanne; Faber, Nicolai; Hartig, Roland; Schraven, Burkhart; Lessmann, Volkmar; Schwegler, Herbert; Stork, Oliver; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-04)
    Cholinergic neuromodulation in the hippocampus controls the salience of background context memory acquired in the presence of elemental stimuli predicting an aversive reinforcement. With pharmacogenetic inhibition we here demonstrate that hilar perforant path-associated (HIPP) cells of the dentate gyrus mediate the devaluation of background context memory during Pavlovian fear conditioning. The salience adjustment is sensitive to reduction of hilar neuropeptide Y (NPY) expression via dominant negative CREB expression in HIPP cells and to acute blockage of NPY-Y1 receptors in the dentate gyrus during conditioning. We show that NPY transmission and HIPP cell activity contribute to inhibitory effects of acetylcholine in the dentate gyrus and that M1 muscarinic receptors mediate the cholinergic activation of HIPP cells as well as their control of background context salience. Our data provide evidence for a peptidergic local circuit in the dentate gyrus that mediates the cholinergic encoding of background context salience during fear memory acquisition.Intra-hippocampal circuits are essential for associating a background context with behaviorally salient stimuli and involve cholinergic modulation at SST(+) interneurons. Here the authors show that the salience of the background context memory is modulated through muscarinic activation of NPY(+) hilar perforant path associated interneurons and NPY signaling in the dentate gyrus.
  • ChIP-on-chip analysis identifies IL-22 as direct target gene of ectopically expressed FOXP3 transcription factor in human T cells

    Jeron, Andreas; Hansen, Wiebke; Ewert, Franziska; Buer, Jan; Geffers, Robert; Bruder, Dunja (2012-12-17)
    Abstract Background The transcription factor (TF) forkhead box P3 (FOXP3) is constitutively expressed at high levels in naturally occurring CD4+CD25+ regulatory T cells (nTregs). It is not only the most accepted marker for that cell population but is also considered lineage determinative. Chromatin immunoprecipitation (ChIP) of TFs in combination with genomic tiling microarray analysis (ChIP-on-chip) has been shown to be an appropriate tool for identifying FOXP3 transcription factor binding sites (TFBSs) on a genome-wide scale. In combination with microarray expression analysis, the ChIP-on-chip technique allows identification of direct FOXP3 target genes. Results ChIP-on-chip analysis of the human FOXP3 expressed in resting and PMA/ionomycin–stimulated Jurkat T cells revealed several thousand putative FOXP3 binding sites and demonstrated the importance of intronic regions for FOXP3 binding. The analysis of expression data showed that the stimulation-dependent down-regulation of IL-22 was correlated with direct FOXP3 binding in the IL-22 promoter region. This association was confirmed by real-time PCR analysis of ChIP-DNA. The corresponding ChIP-region also contained a matching FOXP3 consensus sequence. Conclusions Knowledge of the general distribution patterns of FOXP3 TFBSs in the human genome under resting and activated conditions will contribute to a better understanding of this TF and its influence on direct target genes, as well as its importance for the phenotype and function of Tregs. Moreover, FOXP3-dependent repression of Th17-related IL-22 may be relevant to an understanding of the phenomenon of Treg/Th17 cell plasticity.
  • c-FLIP Expression in Foxp3-Expressing Cells Is Essential for Survival of Regulatory T Cells and Prevention of Autoimmunity.

    Plaza-Sirvent, Carlos; Schuster, Marc; Neumann, Yvonne; Heise, Ulrike; Pils, Marina C; Schulze-Osthoff, Klaus; Schmitz, Ingo; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-01-03)
    Regulatory T (Treg) cells are critical for the shutdown of immune responses and have emerged as valuable targets of immunotherapies. Treg cells can rapidly proliferate; however, the homeostatic processes that limit excessive Treg cell numbers are poorly understood. Here, we show that, compared to conventional T cells, Treg cells have a high apoptosis rate ex vivo correlating with low c-FLIP expression. Treg-specific deletion of c-FLIP in mice resulted in fatal autoimmune disease of a scurfy-like phenotype characterized by absent peripheral Treg cells, activation of effector cells, multi-organ immune cell infiltration, and premature death. Surprisingly, blocking CD95L did not rescue Treg survival in vivo, suggesting additional survival functions of c-FLIP in Treg cells in addition to its classical role in the inhibition of death receptor signaling. Thus, our data reveal a central role for c-FLIP in Treg cell homeostasis and prevention of autoimmunity.
  • ImmunoPET/MR imaging allows specific detection of Aspergillus fumigatus lung infection in vivo.

    Rolle, Anna-Maria; Hasenberg, Mike; Thornton, Christopher R; Solouk-Saran, Djamschid; Männ, Linda; Weski, Juliane; Maurer, Andreas; Fischer, Eliane; Spycher, Philipp R; Schibli, Roger; Boschetti, Frederic; Stegemann-Koniszewski, Sabine; Bruder, Dunja; Severin, Gregory W; Autenrieth, Stella E; Krappmann, Sven; Davies, Genna; Pichler, Bernd J; Gunzer, Matthias; Wiehr, Stefan; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-02-23)
    Invasive pulmonary aspergillosis (IPA) is a life-threatening lung disease caused by the fungus Aspergillus fumigatus, and is a leading cause of invasive fungal infection-related mortality and morbidity in patients with hematological malignancies and bone marrow transplants. We developed and tested a novel probe for noninvasive detection of A. fumigatus lung infection based on antibody-guided positron emission tomography and magnetic resonance (immunoPET/MR) imaging. Administration of a [(64)Cu]DOTA-labeled A. fumigatus-specific monoclonal antibody (mAb), JF5, to neutrophil-depleted A. fumigatus-infected mice allowed specific localization of lung infection when combined with PET. Optical imaging with a fluorochrome-labeled version of the mAb showed colocalization with invasive hyphae. The mAb-based newly developed PET tracer [(64)Cu]DOTA-JF5 distinguished IPA from bacterial lung infections and, in contrast to [(18)F]FDG-PET, discriminated IPA from a general increase in metabolic activity associated with lung inflammation. To our knowledge, this is the first time that antibody-guided in vivo imaging has been used for noninvasive diagnosis of a fungal lung disease (IPA) of humans, an approach with enormous potential for diagnosis of infectious diseases and with potential for clinical translation.
  • D120 and K152 within the PH domain of T cell adapter SKAP55 regulate plasma membrane targeting of SKAP55 and LFA-1 affinity modulation in human T lymphocytes.

    Witte, Amelie; Meineke, Bernhard; Sticht, Jana; Philipsen, Lars; Kuropka, Benno; Müller, Andreas J; Freund, Christian; Schraven, Burkhart; Kliche, Stefanie; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-01-04)
    The β2-integrin lymphocyte function-associated antigen-1 (LFA-1) is needed for T cell receptor (TCR) induced activation of LFA-1 to promote T cell adhesion and interaction with antigen presenting cells (APCs). LFA-1-mediated cell-cell interactions are critical for proper T cell differentiation and proliferation. The Src Kinase-Associated Phosphoprotein of 55 kDa (SKAP55) is a key regulator of TCR-mediated LFA-1 signaling (inside-out/outside-in signaling). To gain understanding of how SKAP55 controls TCR-mediated LFA-1 activation, we assessed the functional role of its Pleckstrin Homology (PH) domain. We identified two critical amino acid residues within the PH domain of SKAP55, aspartic acid 120 (D120) and lysine 152 (K152). D120 facilitates retention of SKAP55 in the cytoplasm of non-stimulated T cells while K152 promotes SKAP55 membrane recruitment via Actin binding upon TCR-triggering. Importantly, the K152-dependent interaction of the PH domain with Actin promotes the binding of Talin to LFA-1 thus facilitating LFA-1 activation. These data suggest that K152 and D120 within the PH domain of SKAP55 regulate plasma membrane targeting and TCR-mediated activation of LFA-1.
  • A cell culture-derived whole virus influenza A vaccine based on magnetic sulfated cellulose particles confers protection in mice against lethal influenza A virus infection.

    Pieler, Michael M; Frentzel, Sarah; Bruder, Dunja; Wolff, Michael W; Reichl, Udo; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-12-07)
    Downstream processing and formulation of viral vaccines employs a large number of different unit operations to achieve the desired product qualities. The complexity of individual process steps involved, the need for time consuming studies towards the optimization of virus yields, and very high requirements regarding potency and safety of vaccines results typically in long lead times for the establishment of new processes. To overcome such obstacles, to enable fast screening of potential vaccine candidates, and to explore options for production of low cost veterinary vaccines a new platform for whole virus particle purification and formulation based on magnetic particles has been established. Proof of concept was carried out with influenza A virus particles produced in suspension Madin Darby canine kidney (MDCK) cells. The clarified, inactivated, concentrated, and diafiltered virus particles were bound to magnetic sulfated cellulose particles (MSCP), and directly injected into mice for immunization including positive and negative controls. We show here, that in contrast to the mock-immunized group, vaccination of mice with antigen-loaded MSCP (aMSCP) resulted in high anti-influenza A antibody responses and full protection against a lethal challenge with replication competent influenza A virus. Antiviral protection correlated with a 400-fold reduced number of influenza nucleoprotein gene copies in the lungs of aMSCP immunized mice compared to mock-treated animals, indicating the efficient induction of antiviral immunity by this novel approach. Thus, our data proved the use of MSCP for purification and formulation of the influenza vaccine to be fast and efficient, and to confer protection of mice against influenza A virus infection. Furthermore, the method proposed has the potential for fast purification of virus particles directly from bioreactor harvests with a minimum number of process steps towards formulation of low-cost veterinary vaccines, and for screening studies requiring fast purification protocols.
  • A Precise Temperature-Responsive Bistable Switch Controlling Yersinia Virulence.

    Nuss, Aaron Mischa; Schuster, Franziska; Roselius, Louisa; Klein, Johannes; Bücker, René; Herbst, Katharina; Heroven, Ann Kathrin; Pisano, Fabio; Wittmann, Christoph; Münch, Richard; Müller, Johannes; Jahn, Dieter; Dersch, Petra; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-12)
    Different biomolecules have been identified in bacterial pathogens that sense changes in temperature and trigger expression of virulence programs upon host entry. However, the dynamics and quantitative outcome of this response in individual cells of a population, and how this influences pathogenicity are unknown. Here, we address these questions using a thermosensing virulence regulator of an intestinal pathogen (RovA of Yersinia pseudotuberculosis) as a model. We reveal that this regulator is part of a novel thermoresponsive bistable switch, which leads to high- and low-invasive subpopulations within a narrow temperature range. The temperature range in which bistability is observed is defined by the degradation and synthesis rate of the regulator, and is further adjustable via a nutrient-responsive regulator. The thermoresponsive switch is also characterized by a hysteretic behavior in which activation and deactivation occurred on vastly different time scales. Mathematical modeling accurately mirrored the experimental behavior and predicted that the thermoresponsiveness of this sophisticated bistable switch is mainly determined by the thermo-triggered increase of RovA proteolysis. We further observed RovA ON and OFF subpopulations of Y. pseudotuberculosis in the Peyer's patches and caecum of infected mice, and that changes in the RovA ON/OFF cell ratio reduce tissue colonization and overall virulence. This points to a bet-hedging strategy in which the thermoresponsive bistable switch plays a key role in adapting the bacteria to the fluctuating conditions encountered as they pass through the host's intestinal epithelium and suggests novel strategies for the development of antimicrobial therapies.
  • Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects.

    Lindqvist, Richard; Mundt, Filip; Gilthorpe, Jonathan D; Wölfel, Silke; Gekara, Nelson O; Kröger, Andrea; Överby, Anna K; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-10-24)
    Neurotropic flaviviruses such as tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Zika virus (ZIKV) are causative agents of severe brain-related diseases including meningitis, encephalitis, and microcephaly. We have previously shown that local type I interferon response within the central nervous system (CNS) is involved in the protection of mice against tick-borne flavivirus infection. However, the cells responsible for mounting this protective response are not defined.
  • Intracellular Staphylococcus aureus eludes selective autophagy by activating a host cell kinase.

    Neumann, Yvonne; Bruns, Svenja A; Rohde, Manfred; Prajsnar, Tomasz K; Foster, Simon J; Schmitz, Ingo; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-11)
    Autophagy, a catabolic pathway of lysosomal degradation, acts not only as an efficient recycle and survival mechanism during cellular stress, but also as an anti-infective machinery. The human pathogen Staphylococcus aureus (S. aureus) was originally considered solely as an extracellular bacterium, but is now recognized additionally to invade host cells, which might be crucial for persistence. However, the intracellular fate of S. aureus is incompletely understood. Here, we show for the first time induction of selective autophagy by S. aureus infection, its escape from autophagosomes and proliferation in the cytoplasm using live cell imaging. After invasion, S. aureus becomes ubiquitinated and recognized by receptor proteins such as SQSTM1/p62 leading to phagophore recruitment. Yet, S. aureus evades phagophores and prevents further degradation by a MAPK14/p38α MAP kinase-mediated blockade of autophagy. Our study demonstrates a novel bacterial strategy to block autophagy and secure survival inside the host cell.
  • Immunomodulation by memantine in therapy of Alzheimer's disease is mediated through inhibition of Kv1.3 channels and T cell responsiveness.

    Lowinus, Theresa; Bose, Tanima; Busse, Stefan; Busse, Mandy; Reinhold, Dirk; Schraven, Burkhart; Bommhardt, Ursula H H; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-07-22)
    Memantine is approved for the treatment of advanced Alzheimer´s disease (AD) and reduces glutamate-mediated neuronal excitotoxicity by antagonism of N-methyl-D-aspartate receptors. In the pathophysiology of AD immune responses deviate and infectious side effects are observed during memantine therapy. However, the particular effects of memantine on human T lymphocytes are unresolved. Here, we provide evidence that memantine blocks Kv1.3 potassium channels, inhibits CD3-antibody- and alloantigen-induced proliferation and suppresses chemokine-induced migration of peripheral blood T cells of healthy donors. Concurrent with the in vitro data, CD4+ T cells from AD patients receiving therapeutic doses of memantine show a transient decline of Kv1.3 channel activity and a long-lasting reduced proliferative response to alloantigens in mixed lymphocyte reactions. Furthermore, memantine treatment provokes a profound depletion of peripheral blood memory CD45RO+ CD4+ T cells. Thus, standard doses of memantine profoundly reduce T cell responses in treated patients through blockade of Kv1.3 channels. This may normalize deviant immunopathology in AD and contribute to the beneficial effects of memantine, but may also account for the enhanced infection rate.
  • Differences and Similarities in TRAIL- and Tumor Necrosis Factor-Mediated Necroptotic Signaling in Cancer Cells.

    Sosna, Justyna; Philipp, Stephan; Fuchslocher Chico, Johaiber; Saggau, Carina; Fritsch, Jürgen; Föll, Alexandra; Plenge, Johannes; Arenz, Christoph; Pinkert, Thomas; Kalthoff, Holger; Trauzold, Anna; Schmitz, Ingo; Schütze, Stefan; Adam, Dieter; Helmholtz Centre for infection research (2016-10-15)
    Recently, a type of regulated necrosis (RN) called necroptosis was identified to be involved in many pathophysiological processes and emerged as an alternative method to eliminate cancer cells. However, only a few studies have elucidated components of TRAIL-mediated necroptosis useful for anticancer therapy. Therefore, we have compared this type of cell death to tumor necrosis factor (TNF)-mediated necroptosis and found similar signaling through acid and neutral sphingomyelinases, the mitochondrial serine protease HtrA2/Omi, Atg5, and vacuolar H(+)-ATPase. Notably, executive mechanisms of both TRAIL- and TNF-mediated necroptosis are independent of poly(ADP-ribose) polymerase 1 (PARP-1), and depletion of p38α increases the levels of both types of cell death. Moreover, we found differences in signaling between TNF- and TRAIL-mediated necroptosis, e.g., a lack of involvement of ubiquitin carboxyl hydrolase L1 (UCH-L1) and Atg16L1 in executive mechanisms of TRAIL-mediated necroptosis. Furthermore, we discovered indications of an altered involvement of mitochondrial components, since overexpression of the mitochondrial protein Bcl-2 protected Jurkat cells from TRAIL- and TNF-mediated necroptosis, and overexpression of Bcl-XL diminished only TRAIL-induced necroptosis in Colo357 cells. Furthermore, TRAIL does not require receptor internalization and endosome-lysosome acidification to mediate necroptosis. Taken together, pathways described for TRAIL-mediated necroptosis and differences from those for TNF-mediated necroptosis might be unique targets to increase or modify necroptotic signaling and eliminate tumor cells more specifically in future anticancer approaches.
  • Influenza A virus infection predisposes hosts to secondary infection with different Streptococcus pneumoniae serotypes with similar outcome but serotype-specific manifestation.

    Sharma-Chawla, Niharika; Sender, Vicky; Kershaw, Olivia; Gruber, Achim D; Volckmar, Julia; Henriques-Normark, Birgitta; Stegemann-Koniszewski, Sabine; Bruder, Dunja; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-09-19)
    Influenza A virus (IAV) and Streptococcus pneumoniae (S. pn.) are major causes of respiratory tract infections, particularly during co-infection. The synergism between these two pathogens is characterized by a complex network of dysregulated immune responses, some of which last until recovery post IAV infection. Despite the high serotype-diversity of S. pn. and the serotype-replacement observed since the introduction of conjugate vaccines, little is known about pneumococcal strain-dependency in the enhanced susceptibility to severe secondary S. pn. infection following IAV infection. Thus we studied how pre-infection with IAV alters host susceptibility to different S. pn. strains with varying degrees of invasiveness using a highly invasive serotype 4, an invasive serotype 7F and a carrier serotype 19F strain. A murine model of pneumococcal co-infection during the acute phase of IAV infection showed a significantly increased degree of pneumonia and mortality for all tested pneumococcal strains at otherwise sublethal doses. The incidence and kinetics of systemic dissemination however remained bacterial strain-dependent. Furthermore we observed strain-specific alterations in the pulmonary levels of alveolar macrophages, neutrophils and inflammatory mediators ultimately affecting immunopathology. During the recovery phase following IAV infection, bacterial growth in the lungs and systemic dissemination were enhanced in a strain-dependent manner. Altogether, this study shows that acute IAV infection predisposes the host to lethal S. pn. infection irrespective of the pneumococcal serotype, while the long lasting synergism between IAV and S. pn. is bacterial strain-dependent. These results hold implications for developing tailored therapeutic treatment regimens for dual infections during future IAV outbreaks.
  • Early changes in the metabolic profile of activated CD8(+) T cells.

    Cammann, Clemens; Rath, Alexander; Reichl, Udo; Lingel, Holger; Brunner-Weinzierl, Monika; Simeoni, Luca; Schraven, Burkhart; Lindquist, Jonathan A; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
    Antigenic stimulation of the T cell receptor (TCR) initiates a change from a resting state into an activated one, which ultimately results in proliferation and the acquisition of effector functions. To accomplish this task, T cells require dramatic changes in metabolism. Therefore, we investigated changes of metabolic intermediates indicating for crucial metabolic pathways reflecting the status of T cells. Moreover we analyzed possible regulatory molecules required for the initiation of the metabolic changes.

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