Recent Submissions

  • Differential magnesium implant corrosion coat formation and contribution to bone bonding.

    Rahim, Muhammad Imran; Weizbauer, Andreas; Evertz, Florian; Hoffmann, Andrea; Rohde, Manfred; Glasmacher, Birgit; Windhagen, Henning; Gross, Gerhard; Seitz, Jan-Marten; Mueller, Peter P; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
    Magnesium alloys are presently under investigation as promising biodegradable implant materials with osteoconductive properties. To study the molecular mechanisms involved, the potential contribution of soluble magnesium corrosion products to the stimulation of osteoblastic cell differentiation was examined. However, no evidence for the stimulation of osteoblast differentiation could be obtained when cultured mesenchymal precursor cells were differentiated in the presence of metallic magnesium or in cell culture medium containing elevated magnesium ion levels. Similarly, in soft tissue no bone induction by metallic magnesium or by the corrosion product magnesium hydroxide could be observed in a mouse model. Motivated by the comparatively rapid accumulation solid corrosion products physicochemical processes were examined as an alternative mechanism to explain the stimulation of bone growth by magnesium-based implants. During exposure to physiological solutions a structured corrosion coat formed on magnesium whereby the elements calcium and phosphate were enriched in the outermost layer which could play a role in the established biocompatible behavior of magnesium implants. When magnesium pins were inserted into avital bones, corrosion lead to increases in the pull out force, suggesting that the expanding corrosion layer was interlocking with the surrounding bone. Since mechanical stress is a well-established inducer of bone growth, volume increases caused by the rapid accumulation of corrosion products and the resulting force development could be a key mechanism and provide an explanation for the observed stimulatory effects of magnesium-based implants in hard tissue. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 697-709, 2017.
  • Budesonide in Autoimmune Hepatitis: The Right Drug at the Right Time for the Right Patient.

    Manns, Michael P; Jaeckel, Elmar; Taubert, Richard; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-11-08)
  • Future Organization of Clinical Research in Germany: The Road to the "German Centre for Digestive Health" (GCDH).

    Manns, Michael P; Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School (MHH), Hannover, Germany. (2016-12)
  • Gain of function in Jak2V617F-positive T-cells.

    Nishanth, G; Wolleschak, D; Fahldieck, C; Fischer, T; Mullally, A; Perner, F; Schnöder, T M; Just, S; Heidel, F H; Schlüter, D; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-04)
  • Hepatitis D virus in Africa: several unmet needs.

    Manns, Michael P; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-10)
  • Challenges in warranting access to prophylaxis and therapy for hepatitis B virus infection.

    Debarry, Jennifer; Cornberg, Markus; Manns, Michael P; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-01)
    Despite an available vaccine and efficient treatment for hepatitis B virus (HBV) infection, chronic HBV infection still remains a major global threat, and one of the top 20 causes of human mortality worldwide. One of the major challenges in controlling HBV infection is the high number of undiagnosed chronic carriers and the lack of access to prophylaxis and treatment in several parts of the world. We discuss relevant barriers that need to be overcome to achieve global control of HBV infection and make eradication possible. Most important, vaccination must be scaled-up to lower the risk of vertical transmission and decrease the number of new infections, and comprehensive screening programs must be linked to care to obtain a better rate of diagnosis and treatment. This can probably only be achieved if sustainable funding is available. We therefore emphasize the importance of making the management of viral hepatitis a global health priority.
  • Linoleic and palmitoleic acid block streptokinase-mediated plasminogen activation and reduce severity of invasive group A streptococcal infection

    Rox, Katharina; Jansen, Rolf; Loof, Torsten G.; Gillen, Christine M.; Bernecker, Steffen; Walker, Mark J.; Chhatwal, Gursharan Singh; Müller, Rolf; Helmholtz-Institut für pharmazeutische Forschung Saarland,Universitätscampus E8.1, 66123 Saarbrücken, Germany. (2017-09-18)
    In contrast to mild infections of Group A Streptococcus (GAS) invasive infections of GAS still pose a serious health hazard: GAS disseminates from sterile sites into the blood stream or deep tissues and causes sepsis or necrotizing fasciitis. In this case antibiotics do not provide an effective cure as the bacteria are capable to hide from them very quickly. Therefore, new remedies are urgently needed. Starting from a myxobacterial natural products screening campaign, we identified two fatty acids isolated from myxobacteria, linoleic and palmitoleic acid, specifically blocking streptokinase-mediated activation of plasminogen and thereby preventing streptococci from hijacking the host’s plasminogen/plasmin system. This activity is not inherited by other fatty acids such as oleic acid and is not attributable to the killing of streptococci. Moreover, both fatty acids are superior in their inhibitory properties compared to two clinically used drugs (tranexamic or ε-amino caproic acid) as they show 500–1000 fold lower IC50 values. Using a humanized plasminogen mouse model mimicking the clinical situation of a local GAS infection that becomes systemic, we demonstrate that these fatty acids ameliorate invasive GAS infection significantly. Consequently, linoleic and palmitoleic acid are possible new options to combat GAS invasive diseases.
  • Controlled re-activation of epigenetically silenced Tet promoter-driven transgene expression by targeted demethylation.

    Gödecke, Natascha; Zha, Lisha; Spencer, Shawal; Behme, Sara; Riemer, Pamela; Rehli, Michael; Hauser, Hansjörg; Wirth, Dagmar; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, D38124 Braunschweig, Germany. (2017-09-19)
    Faithful expression of transgenes in cell cultures and mice is often challenged by locus dependent epigenetic silencing. We investigated silencing of Tet-controlled expression cassettes within the mouse ROSA26 locus. We observed pronounced DNA methylation of the Tet promoter concomitant with loss of expression in mES cells as well as in differentiated cells and transgenic animals. Strikingly, the ROSA26 promoter remains active and methylation free indicating that this silencing mechanism specifically affects the transgene, but does not spread to the host's chromosomal neighborhood. To reactivate Tet cassettes a synthetic fusion protein was constructed and expressed in silenced cells. This protein includes the enzymatic domains of ten eleven translocation methylcytosine dioxygenase 1 (TET-1) as well as the Tet repressor DNA binding domain. Expression of the synthetic fusion protein and Doxycycline treatment allowed targeted demethylation of the Tet promoter in the ROSA26 locus and in another genomic site, rescuing transgene expression in cells and transgenic mice. Thus, inducible, reversible and site-specific epigenetic modulation is a promising strategy for reactivation of silenced transgene expression, independent of the integration site.
  • Analysis of mitochondrial metabolism in situ: Combining stable isotope labeling with selective permeabilization.

    Nonnenmacher, Yannic; Palorini, Roberta; d'Herouël, Aymeric Fouquier; Krämer, Lisa; Neumann-Schaal, Meina; Chiaradonna, Ferdinando; Skupin, Alexander; Wegner, Andre; Hiller, Karsten; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-09)
    To date, it is well-established that mitochondrial dysfunction does not only play a vital role in cancer but also in other pathological conditions such as neurodegenerative diseases and inflammation. An important tool for the analysis of cellular metabolism is the application of stable isotope labeled substrates, which allow for the tracing of atoms throughout metabolic networks. While such analyses yield very detailed information about intracellular fluxes, the determination of compartment specific fluxes is far more challenging. Most approaches for the deconvolution of compartmented metabolism use computational models whereas experimental methods are rare. Here, we developed an experimental setup based on selective permeabilization of the cytosolic membrane that allows for the administration of stable isotope labeled substrates directly to mitochondria. We demonstrate how this approach can be used to infer metabolic changes in mitochondria induced by either chemical or genetic perturbations and give an outlook on its potential applications.
  • TLR9-Mediated Conditioning of Liver Environment Is Essential for Successful Intrahepatic Immunotherapy and Effective Memory Recall.

    Cebula, Marcin; Riehn, Mathias; Hillebrand, Upneet; Kratzer, Ramona F; Kreppel, Florian; Koutsoumpli, Georgia; Daemen, Toos; Hauser, Hansjörg; Wirth, Dagmar; Helmholtz -Zentrum für Infektionsforschung GmbH. Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-07-14)
    Immune defense against hepatotropic viruses such as hepatitis B (HBV) and hepatitis C (HCV) poses a major challenge for therapeutic approaches. Intrahepatic cytotoxic CD8 T cells that are crucial for an immune response against these viruses often become exhausted resulting in chronic infection. We elucidated the T cell response upon therapeutic vaccination in inducible transgenic mouse models in which variable percentages of antigen-expressing hepatocytes can be adjusted, providing mosaic antigen distribution and reflecting the varying viral antigen loads observed in patients. Vaccination-induced endogenous CD8 T cells could eliminate low antigen loads in liver but were functionally impaired if confronted with elevated antigen loads. Strikingly, only by conditioning the liver environment with TLR9 ligand prior and early after peripheral vaccination, successful immunization against high intrahepatic antigen density with its elimination was achieved. Moreover, TLR9 immunomodulation was also indispensable for functional memory recall after high frequency antigen challenge. Together, the results indicate that TLR9-mediated conditioning of liver environment during therapeutic vaccination or antigen reoccurrence is crucial for an efficacious intrahepatic T cell response.
  • Structural, mechanistic and functional insight into gliotoxin bis-thiomethylation in Aspergillus fumigatus.

    Dolan, Stephen K; Bock, Tobias; Hering, Vanessa; Owens, Rebecca A; Jones, Gary W; Blankenfeldt, Wulf; Doyle, Sean; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-02)
    Gliotoxin is an epipolythiodioxopiperazine (ETP) class toxin, contains a disulfide bridge that mediates its toxic effects via redox cycling and is produced by the opportunistic fungal pathogen Aspergillus fumigatus Self-resistance against gliotoxin is effected by the gliotoxin oxidase GliT, and attenuation of gliotoxin biosynthesis is catalysed by gliotoxin S-methyltransferase GtmA. Here we describe the X-ray crystal structures of GtmA-apo (1.66 Å), GtmA complexed to S-adenosylhomocysteine (1.33 Å) and GtmA complexed to S-adenosylmethionine (2.28 Å), providing mechanistic insights into this important biotransformation. We further reveal that simultaneous elimination of the ability of A. fumigatus to dissipate highly reactive dithiol gliotoxin, via deletion of GliT and GtmA, results in the most significant hypersensitivity to exogenous gliotoxin observed to date. Indeed, quantitative proteomic analysis of ΔgliT::ΔgtmA reveals an uncontrolled over-activation of the gli-cluster upon gliotoxin exposure. The data presented herein reveal, for the first time, the extreme risk associated with intracellular dithiol gliotoxin biosynthesis-in the absence of an efficient dismutation capacity. Significantly, a previously concealed protective role for GtmA and functionality of ETP bis-thiomethylation as an ancestral protection strategy against dithiol compounds is now evident.
  • Cell Polarization and Epigenetic Status Shape the Heterogeneous Response to Type III Interferons in Intestinal Epithelial Cells.

    Bhushal, Sudeep; Wolfsmüller, Markus; Selvakumar, Tharini A; Kemper, Lucas; Wirth, Dagmar; Hornef, Mathias W; Hauser, Hansjörg; Köster, Mario; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
    Type I and type III interferons (IFNs) are crucial components of the first-line antiviral host response. While specific receptors for both IFN types exist, intracellular signaling shares the same Jak-STAT pathway. Due to its receptor expression, IFN-λ responsiveness is restricted mainly to epithelial cells. Here, we display IFN-stimulated gene induction at the single cell level to comparatively analyze the activities of both IFN types in intestinal epithelial cells and mini-gut organoids. Initially, we noticed that the response to both types of IFNs at low concentrations is based on a single cell decision-making determining the total cell intrinsic antiviral activity. We identified histone deacetylase (HDAC) activity as a crucial restriction factor controlling the cell frequency of IFN-stimulated gene (ISG) induction upon IFN-λ but not IFN-β stimulation. Consistently, HDAC blockade confers antiviral activity to an elsewise non-responding subpopulation. Second, in contrast to the type I IFN system, polarization of intestinal epithelial cells strongly enhances their ability to respond to IFN-λ signaling and raises the kinetics of gene induction. Finally, we show that ISG induction in mini-gut organoids by low amounts of IFN is characterized by a scattered heterogeneous responsiveness of the epithelial cells and HDAC activity fine-tunes exclusively IFN-λ activity. This study provides a comprehensive description of the differential response to type I and type III IFNs and demonstrates that cell polarization in gut epithelial cells specifically increases IFN-λ activity.
  • Helicobacter pylori vacA genotype is a predominant determinant of immune response to Helicobacter pylori CagA.

    Link, Alexander; Langner, Cosima; Schirrmeister, Wiebke; Habendorf, Wiebke; Weigt, Jochen; Venerito, Marino; Tammer, Ina; Schlüter, Dirk; Schlaermann, Philipp; Meyer, Thomas F; Wex, Thomas; Malfertheiner, Peter; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-07-14)
    To evaluate the frequency of Helicobacter pylori (H. pylori) CagA antibodies in H. pylori infected subjects and to identify potential histopathological and bacterial factors related to H. pylori CagA-immune response.
  • Divergent co-transcriptomes of different host cells infected with Toxoplasma gondii reveal cell type-specific host-parasite interactions.

    Swierzy, Izabela J; Händel, Ulrike; Kaever, Alexander; Jarek, Michael; Scharfe, Maren; Schlüter, Dirk; Lüder, Carsten G K; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-03)
    The apicomplexan parasite Toxoplasma gondii infects various cell types in avian and mammalian hosts including humans. Infection of immunocompetent hosts is mostly asymptomatic or benign, but leads to development of largely dormant bradyzoites that persist predominantly within neurons and muscle cells. Here we have analyzed the impact of the host cell type on the co-transcriptomes of host and parasite using high-throughput RNA sequencing. Murine cortical neurons and astrocytes, skeletal muscle cells (SkMCs) and fibroblasts differed by more than 16,200 differentially expressed genes (DEGs) before and after infection with T. gondii. However, only a few hundred of them were regulated by infection and these largely diverged in neurons, SkMCs, astrocytes and fibroblasts indicating host cell type-specific transcriptional responses after infection. The heterogeneous transcriptomes of host cells before and during infection coincided with ~5,400 DEGs in T. gondii residing in different cell types. Finally, we identified gene clusters in both T. gondii and its host, which correlated with the predominant parasite persistence in neurons or SkMCs as compared to astrocytes or fibroblasts. Thus, heterogeneous expression profiles of different host cell types and the parasites' ability to adapting to them may govern the parasite-host cell interaction during toxoplasmosis.
  • Sonderforschungsbereich SFB 738: Optimierung konventioneller und innovativer Transplantate

    Manns, Michael P; Huber, Petra; Jaeckel, Elmar; Helmholtz Zentrum für Infektionsforschung GmbH, Inhoofenstr. 7, 38124 Braunschweig, Germany. (2017-08-09)
  • Human Anti-Lipopolysaccharid (LPS) antibodies against Legionella with high species specificity.

    Kuhn, Philipp; Thiem, Stefanie; Steinert, Michael; Purvis, Duncan; Lugmayr, Veronika; Treutlein, Ulrich; Plobner, Lutz; Leiser, Robert-Matthias; Hust, Michael; Dübel, Stefan; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-07-19)
    Legionella are Gram-negative bacteria that are ubiquitously present in natural and man-made water reservoirs. When humans inhale aerosolized water contaminated with Legionella, alveolar macrophages can be infected, which may lead to a life-threatening pneumonia called Legionnaires' disease. Due to the universal distribution of Legionella in water and their potential threat to human health, the Legionella concentration in water for human use must be strictly monitored, which is difficult since the standard detection still relies on lengthy cultivation and analysis of bacterial morphology. In this study, an antibody against L. pneumophila has been generated from the naïve human HAL antibody libraries by phage-display for the first time. The panning was performed on whole bacterial cells in order to select antibodies that bind specifically to the cell surface of untreated Legionella. The bacterial cell wall component lipopolysaccharide (LPS) was identified as the target structure. Specific binding to the important pathogenic L. pneumophila strains Corby, Philadelphia-1 and Knoxville was observed, while no binding was detected to seven members of the families Enterobacteriaceae, Pseudomonadaceae or Clostridiaceae. Production of this antibody in the recombinant scFv-Fc format using either a murine or a human Fc part allowed the set-up of a sandwich-ELISA for detection of Legionella cells. The scFv-Fc construct proved to be very stable, even when stored for several weeks at elevated temperatures. A sensitivity limit of 4,000 cells was achieved. The scFv-Fc antibody pair was integrated on a biosensor, demonstrating the specific and fast detection of L. pneumophila on a portable device. With this system, 10,000 Legionella cells were detected within 35 min. Combined with a water filtration/concentration system, this antibody may be developed into a promising reagent for rapid on-site Legionella monitoring.
  • [Individualized infection medicine : Challenges and opportunities].

    Debarry, J; Heinz, D; Manns, M P; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-07)
  • Degradable magnesium implant-associated infections by bacterial biofilms induce robust localized and systemic inflammatory reactions in a mouse model.

    Rahim, Muhammad Imran; Babbar, Anshu; Lienenklaus, Stefan; Pils, Marina; Rohde, M; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-06-01)
    Biomaterial-associated Pseudomonas aeruginosa biofilm infections constitute cascade of host immune reactions ultimately leading towards implant failure. Due to lack of relevant in vivo biofilm models, majority of the studies report host immune responses against free living or planktonic bacteria while bacteria in clinical situations live more frequently as biofilm communities than as single cells. Present study investigated host immune responses against biomaterial-associated P. aeruginosa biofilms in a clinically relevant mouse model. Previously, we reported metallic magnesium, a prospective biodegradable implant, to be permissive for bacterial biofilms in vivo even though it exhibits antibacterial properties in vitro. Therefore, magnesium was employed as biomaterial to investigate in vivo biofilm formation and associated host immune responses by using two P. aeruginosa strains and two mouse strains. P. aeruginosa formed biofilms on subcutaneously implanted magnesium discs. Non-invasive in vivo imaging indicated transient inflammatory responses at control sites whereas robust prolonged interferon-β (IFN-β) expression was observed from biofilms in a transgenic animal reporter. Further, immunohistology and electron microscopic results showed that bacterial biofilms were located in two dimensions immediately on the implant surface and at a short distance in the adjacent tissue. These biofilms were surrounded by inflammatory cells (mainly polymorphonuclear cells) as compared to controls. Interestingly, even though the number of live bacteria in various organs remained below detectable levels, splenomegaly indicated systemic inflammatory processes. Overall, these findings confirmed the resistance of biofilm infections in vivo to potentially antibacterial properties of magnesium degradation products. In vivo imaging and histology indicated the induction of both, local and systemic host inflammatory responses against P. aeruginosa biofilms. Even though the innate host immune defenses could not eliminate the local infection for up to two weeks, there was no apparent systemic bacteremia and all animals investigated survived the infection.
  • Pathogen-induced ubiquitin-editing enzyme A20 bifunctionally shuts off NF-κB and caspase-8-dependent apoptotic cell death.

    Lim, Michelle C C; Maubach, Gunter; Sokolova, Olga; Feige, Michael H; Diezko, Rolf; Buchbinder, Jörn; Backert, Steffen; Schlüter, Dirk; Lavrik, Inna N; Naumann, Michael; Helmholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-06-02)
    The human pathogen Helicobacter pylori infects more than half of the world's population and is a paradigm for persistent yet asymptomatic infection but increases the risk for chronic gastritis and gastric adenocarcinoma. For successful colonization, H. pylori needs to subvert the host cell death response, which serves to confine pathogen infection by killing infected cells and preventing malignant transformation. Infection of gastric epithelial cells by H. pylori provokes direct and fast activation of the proinflammatory and survival factor NF-κB, which regulates target genes, such as CXCL8, BIRC3 and TNFAIP3. However, it is not known how H. pylori exploits NF-κB activation and suppresses the inflammatory response and host apoptotic cell death, in order to avert the innate immune response and avoid cell loss, and thereby enhance colonization to establish long-term infection. Here we assign for the first time that H. pylori and also Campylobacter jejuni-induced ubiquitin-editing enzyme A20 bifunctionally terminates NF-κB activity and negatively regulates apoptotic cell death. Mechanistically, we show that the deubiquitinylase activity of A20 counteracts cullin3-mediated K63-linked ubiquitinylation of procaspase-8, therefore restricting the activity of caspase-8. Interestingly, another inducible NF-κB target gene, the scaffold protein p62, ameliorates the interaction of A20 with procaspase-8. In conclusion, pathogen-induced de novo synthesis of A20 regulates the shut-off of the survival factor NF-κB but, on the other hand, also impedes caspase-8-dependent apoptotic cell death so as to promote the persistence of pathogens.Cell Death and Differentiation advance online publication, 2 June 2017; doi:10.1038/cdd.2017.89.
  • Structural similarities and functional differences clarify evolutionary relationships between tRNA healing enzymes and the myelin enzyme CNPase.

    Muruganandam, Gopinath; Raasakka, Arne; Myllykoski, Matti; Kursula, Inari; Kursula, Petri; Helmholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-05-16)
    Eukaryotic tRNA splicing is an essential process in the transformation of a primary tRNA transcript into a mature functional tRNA molecule. 5'-phosphate ligation involves two steps: a healing reaction catalyzed by polynucleotide kinase (PNK) in association with cyclic phosphodiesterase (CPDase), and a sealing reaction catalyzed by an RNA ligase. The enzymes that catalyze tRNA healing in yeast and higher eukaryotes are homologous to the members of the 2H phosphoesterase superfamily, in particular to the vertebrate myelin enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase).

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