• Composing a Tumor Specific Bacterial Promoter.

      Deyneko, Igor V; Kasnitz, Nadine; Leschner, Sara; Weiss, Siegfried; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      Systemically applied Salmonella enterica spp. have been shown to invade and colonize neoplastic tissues where it retards the growth of many tumors. This offers the possibility to use the bacteria as a vehicle for the tumor specific delivery of therapeutic molecules. Specificity of such delivery is solely depending on promoter sequences that control the production of a target molecule. We have established the functional structure of bacterial promoters that are transcriptionally active exclusively in tumor tissues after systemic application. We observed that the specific transcriptional activation is accomplished by a combination of a weak basal promoter and a strong FNR binding site. This represents a minimal set of control elements required for such activation. In natural promoters, additional DNA remodeling elements are found that alter the level of transcription quantitatively. Inefficiency of the basal promoter ensures the absence of transcription outside tumors. As a proof of concept, we compiled an artificial promoter sequence from individual motifs representing FNR and basal promoter and showed specific activation in a tumor microenvironment. Our results open possibilities for the generation of promoters with an adjusted level of expression of target proteins in particular for applications in bacterial tumor therapy.
    • In-vivo expression profiling of Pseudomonas aeruginosa infections reveals niche-specific and strain-independent transcriptional programs.

      Bielecki, Piotr; Puchałka, Jacek; Wos-Oxley, Melissa L; Loessner, Holger; Glik, Justyna; Kawecki, Marek; Nowak, Mariusz; Tümmler, Burkhard; Weiss, Siegfried; dos Santos, Vítor A P Martins; et al. (2011)
      Pseudomonas aeruginosa is a threatening, opportunistic pathogen causing disease in immunocompromised individuals. The hallmark of P. aeruginosa virulence is its multi-factorial and combinatorial nature. It renders such bacteria infectious for many organisms and it is often resistant to antibiotics. To gain insights into the physiology of P. aeruginosa during infection, we assessed the transcriptional programs of three different P. aeruginosa strains directly after isolation from burn wounds of humans. We compared the programs to those of the same strains using two infection models: a plant model, which consisted of the infection of the midrib of lettuce leaves, and a murine tumor model, which was obtained by infection of mice with an induced tumor in the abdomen. All control conditions of P. aeruginosa cells growing in suspension and as a biofilm were added to the analysis. We found that these different P. aeruginosa strains express a pool of distinct genetic traits that are activated under particular infection conditions regardless of their genetic variability. The knowledge herein generated will advance our understanding of P. aeruginosa virulence and provide valuable cues for the definition of prospective targets to develop novel intervention strategies.
    • An Intrinsic Propensity of Murine Peritoneal B1b Cells to Switch to IgA in Presence of TGF-β and Retinoic Acid.

      Roy, Bishnudeo; Brennecke, Anne-Margarete; Agarwal, Shiwani; Krey, Martina; Düber, Sandra; Weiss, Siegfried (2013)
      In the present study we have investigated the comparative switching propensity of murine peritoneal and splenic B cell subpopulations to IgA in presence of retinoic acid (RA) and TGF-β.
    • Murine toll-like receptor 2 activation induces type I interferon responses from endolysosomal compartments.

      Dietrich, Nicole; Lienenklaus, Stefan; Weiss, Siegfried; Gekara, Nelson O; Molecular Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany. (2010)
      BACKGROUND: Toll-like receptors (TLRs) are among the first-line sentinels for immune detection and responsiveness to pathogens. The TLR2 subfamily of TLRs (TLR1, TLR2, TLR6) form heterodimers with each other and are thus able to recognize a broad range of components from several microbes such as yeast, Gram-positive bacteria and protozoa. Until now, TLR2 activation by bacterial ligands has long been associated with pro-inflammatory cytokines but not type I interferon responses. METHODOLOGY/PRINCIPAL FINDINGS: Using a variety of transgenic mice, here we provide in vivo and in vitro data showing that TLR2 activation does in fact induce interferon-beta and that this occurs via MyD88-IRF1 and -IRF7 pathways. Interestingly, by microscopy we demonstrate that although a cell surface receptor, TLR2 dependent induction of type I interferons occurs in endolysosomal compartments where it is translocated to upon ligand engagement. Furthermore, we could show that blocking receptor internalization or endolysosomal acidification inhibits the ability of TLR2 to trigger the induction type I interferon but not pro-inflammatory responses. CONCLUSION/SIGNIFICANCE: The results indicate that TLR2 activation induces pro-inflammatory and type I interferon responses from distinct subcellular sites: the plasma membrane and endolysosomal compartments respectively. Apart from identifying and characterizing a novel pathway for induction of type I interferons, the present study offers new insights into how TLR signaling discriminates and regulates the nature of responses to be elicited against extracellular and endocytosed microbes. These findings may also have clinical implication. Excessive production of pro-inflammatory cytokines and type I IFNs following activation of TLRs is a central pathologic event in several hyper-inflammatory conditions. The discovery that the induction of pro-inflammatory and type I IFN responses can be uncoupled through pharmacological manipulation of endolysosomal acidification suggests new avenues for potential therapeutic intervention against inflammations and sepsis.
    • Systemic and Mucosal Immune Reactivity upon Mycobacterium avium ssp. paratuberculosis Infection in Mice.

      Koc, Arzu; Bargen, Imke; Suwandi, Abdulhadi; Roderfeld, Martin; Tschuschner, Annette; Rath, Timo; Gerlach, Gerald F; Hornef, Mathias; Goethe, Ralph; Weiss, Siegfried; et al. (2014)
      Mycobacterium avium ssp. paratuberculosis (MAP) is the cause of Johne's disease, an inflammatory bowel disorder of ruminants. Due to the similar pathology, MAP was also suggested to cause Crohn's disease (CD). Despite of intensive research, this question is still not settled, possibly due to the lack of versatile mouse models. The aim of this study was to identify basic immunologic mechanisms in response to MAP infection. Immune compromised C57BL/6 Rag2-/- mice were infected with MAP intraperitoneally. Such chronically infected mice were then reconstituted with CD4+ and CD8+ T cells 28 days after infection. A systemic inflammatory response, detected as enlargement of the spleen and granuloma formation in the liver, was observed in mice infected and reconstituted with CD4+ T cells. Whereby inflammation in infected and CD4+CD45RBhi T cell reconstituted animals was always higher than in the other groups. Reconstitution of infected animals with CD8+ T cells did not result in any inflammatory signs. Interestingly, various markers of inflammation were strongly up-regulated in the colon of infected mice reconstituted with CD4+CD45RBlo/int T cells. We propose, the usual non-colitogenic CD4+CD45RBlo/int T cells were converted into inflammatory T cells by the interaction with MAP. However, the power of such cells might be not sufficient for a fully established inflammatory response in the colon. Nevertheless, our model system appears to mirror aspects of an inflammatory bowel disease (IBD) like CD and Johne's diseases. Thus, it will provide an experimental platform on which further knowledge on IBD and the involvement of MAP in the induction of CD could be acquired.
    • Tumor invasion of Salmonella enterica serovar Typhimurium is accompanied by strong hemorrhage promoted by TNF-alpha.

      Leschner, Sara; Westphal, Kathrin; Dietrich, Nicole; Viegas, Nuno; Jablonska, Jadwiga; Lyszkiewicz, Marcin; Lienenklaus, Stefan; Falk, Werner; Gekara, Nelson; Loessner, Holger; et al. (2009)
      Several facultative anaerobic bacteria with potential therapeutic abilities are known to preferentially colonize solid tumors after systemic administration. How they efficiently find and invade the tumors is still unclear. However, this is an important issue to be clarified when bacteria should be tailored for application in cancer therapy.