group leader: Kröger

Recent Submissions

  • Intrabodies against the Polysialyltransferases ST8SiaII and ST8SiaIV inhibit Polysialylation of NCAM in rhabdomyosarcoma tumor cells.

    Somplatzki, Stefan; Mühlenhoff, Martina; Kröger, Andrea; Gerardy-Schahn, Rita; Böldicke, Thomas; Helmholtz Centr for infection research (2017-05-12)
    Polysialic acid (polySia) is a carbohydrate modification of the neural cell adhesion molecule (NCAM), which is implicated in neural differentiation and plays an important role in tumor development and metastasis. Polysialylation of NCAM is mediated by two Golgi-resident polysialyltransferases (polyST) ST8SiaII and ST8SiaIV. Intracellular antibodies (intrabodies; IB) expressed inside the ER and retaining proteins passing the ER such as cell surface receptors or secretory proteins provide an efficient means of protein knockdown. To inhibit the function of ST8SiaII and ST8SiaIV specific ER IBs were generated starting from two corresponding hybridoma clones. Both IBs αST8SiaII-IB and αST8SiaIV-IB were constructed in the scFv format and their functions characterized in vitro and in vivo.
  • The role of the poly(A) tract in the replication and virulence of tick-borne encephalitis virus.

    Asghar, Naveed; Lee, Yi-Ping; Nilsson, Emma; Lindqvist, Richard; Melik, Wessam; Kröger, Andrea; Överby, Anna K; Johansson, Magnus; Helmholtz Centre for infection research. Inhoffenstr. 7. 38124 Braunschweig, Germany. (2016-12-16)
    The tick-borne encephalitis virus (TBEV) is a flavivirus transmitted to humans, usually via tick bites. The virus causes tick-borne encephalitis (TBE) in humans, and symptoms range from mild flu-like symptoms to severe and long-lasting sequelae, including permanent brain damage. It has been suggested that within the population of viruses transmitted to the mammalian host, quasispecies with neurotropic properties might become dominant in the host resulting in neurological symptoms. We previously demonstrated the existence of TBEV variants with variable poly(A) tracts within a single blood-fed tick. To characterize the role of the poly(A) tract in TBEV replication and virulence, we generated infectious clones of Torö-2003 with the wild-type (A)3C(A)6 sequence (Torö-6A) or with a modified (A)3C(A)38 sequence (Torö-38A). Torö-38A replicated poorly compared to Torö-6A in cell culture, but Torö-38A was more virulent than Torö-6A in a mouse model of TBE. Next-generation sequencing of TBEV genomes after passaging in cell culture and/or mouse brain revealed mutations in specific genomic regions and the presence of quasispecies that might contribute to the observed differences in virulence. These data suggest a role for quasispecies development within the poly(A) tract as a virulence determinant for TBEV in mice.
  • Growing tumors induce a local STING dependent Type I IFN response in dendritic cells.

    Andzinski, Lisa; Spanier, Julia; Kasnitz, Nadine; Kröger, Andrea; Jin, Lei; Brinkmann, Melanie M; Kalinke, Ulrich; Weiss, Siegfried; Jablonska, Jadwiga; Lienenklaus, Stefan; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-09-15)
    The importance of endogenous Type I IFNs in cancer immune surveillance is well established by now. Their role in polarization of tumor-associated neutrophilic granulocytes into anti-tumor effector cells has been recently demonstrated. Yet, the cellular source of Type I IFNs as well as the mode of induction is not clearly defined. Here, we demonstrate that IFN-β is induced by growing murine tumors. Induction is mainly mediated via STING-dependent signaling pathways, suggesting tumor derived DNA as trigger. Transcription factors IRF3 and IRF5 were activated under these conditions which is consistent with tumor infiltrating dendritic cells (DCs) being the major cellular source of IFN-β at the tumor site. Besides DCs, tumor cells themselves are induced to contribute to the production of IFN-β. Taken together, our data provide further information on immune surveillance by Type I IFNs and suggest novel potent cellular targets for future cancer therapy.
  • Immune Protection against Virus Challenge in Aging Mice Is Not Affected by Latent Herpesviral Infections.

    Marandu, Thomas F; Oduro, Jennifer D; Borkner, Lisa; Dekhtiarenko, Iryna; Uhrlaub, Jennifer L; Drabig, Anja; Kröger, Andrea; Nikolich-Zugich, Janko; Cicin-Sain, Luka; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015-11-15)
    Latent herpesvirus infections alter immune homeostasis. To understand if this results in aging-related loss of immune protection against emerging infections, we challenged old mice carrying latent mouse cytomegalovirus (CMV), herpes simplex virus 1 (HSV-1), and/or murine gammaherpesvirus 68 (MHV-68) with influenza virus, West Nile virus (WNV), or vesicular stomatitis virus (VSV). We observed no increase in mortality or weight loss compared to results seen with herpesvirus-negative counterparts and a relative but not absolute reduction in CD8 responses to acute infections. Therefore, the presence of herpesviruses does not appear to increase susceptibility to emerging infections in aging patients.
  • DNA Damage Primes the Type I Interferon System via the Cytosolic DNA Sensor STING to Promote Anti-Microbial Innate Immunity.

    Härtlova, Anetta; Erttmann, Saskia F; Raffi, Faizal Am; Schmalz, Anja M; Resch, Ulrike; Anugula, Sharath; Lienenklaus, Stefan; Nilsson, Lisa M; Kröger, Andrea; Nilsson, Jonas A; Ek, Torben; Weiss, Siegfried; Gekara, Nelson O; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015-02-17)
    Dysfunction in Ataxia-telangiectasia mutated (ATM), a central component of the DNA repair machinery, results in Ataxia Telangiectasia (AT), a cancer-prone disease with a variety of inflammatory manifestations. By analyzing AT patient samples and Atm(-/-) mice, we found that unrepaired DNA lesions induce type I interferons (IFNs), resulting in enhanced anti-viral and anti-bacterial responses in Atm(-/-) mice. Priming of the type I interferon system by DNA damage involved release of DNA into the cytoplasm where it activated the cytosolic DNA sensing STING-mediated pathway, which in turn enhanced responses to innate stimuli by activating the expression of Toll-like receptors, RIG-I-like receptors, cytoplasmic DNA sensors, and their downstream signaling partners. This study provides a potential explanation for the inflammatory phenotype of AT patients and establishes damaged DNA as a cell intrinsic danger signal that primes the innate immune system for a rapid and amplified response to microbial and environmental threats.
  • Cell entry, efficient RNA replication, and production of infectious hepatitis C virus progeny in mouse liver-derived cells

    Frentzen, Anne; Anggakusuma; Gürlevik, Engin; Hueging, Kathrin; Knocke, Sarah; Ginkel, Corinne; Brown, Richard J.P.; Heim, Markus; Dill, Michael T.; Kröger, Andrea; Kalinke, Ulrich; Kaderali, Lars; Kuehnel, Florian; Pietschmann, Thomas (2014-01-15)
  • Distinct modes of action applied by transcription factors STAT1 and IRF1 to initiate transcription of the IFN-gamma-inducible gbp2 gene.

    Ramsauer, Katrin; Farlik, Matthias; Zupkovitz, Gordin; Seiser, Christian; Kröger, Andrea; Hauser, Hansjörg; Decker, Thomas; Max F. Perutz Laboratories, Department of Microbiology and Immunobiology, University of Vienna, A1030 Vienna, Austria. (2007-02-20)
    A subgroup of genes induced by IFN-gamma requires both STAT1 and IRF1 for transcriptional activation. Using WT, stat1(-/-), or irf1(-/-) cells, we analyzed the changes induced by IFN-gamma in gbp2 promoter chromatin. STAT1 associated with the promoter independently of IRF1 and played an essential role in the ordered recruitment of the coactivator/histone acetyl transferase CREB-binding protein (CBP) and the histone deacetylase HDAC1. Hyperacetylation of histone 4 also required STAT1. Phosphorylation at S727 in the transactivating domain increased transcriptional activity of STAT1. In cells expressing a STAT1S727A-mutant CBP recruitment, histone 4 hyperacetylation and RNA polymerase II association with the gbp2 promoter were strongly reduced. IRF1 association with the gbp2 promoter followed that of STAT1, but STAT1 association with DNA or histone hyperacetylation were not necessary for IRF1 binding. RNA polymerase II association with the gbp2 promoter required both STAT1 and IRF1, suggesting that both proteins mediate essential steps in transcriptional activation. IRF1, but not STAT1, was found to coimmunoprecipitate with RNA polymerase II. Together, the data support the assumption that the main role of STAT1 in activating gbp2 transcription is to provide transcriptionally competent chromatin, whereas the function of IRF1 may lie in directly contacting RNA polymerase II-containing transcriptional complexes.
  • Composition and arrangement of genes define the strength of IRES-driven translation in bicistronic mRNAs

    Hennecke, Meike; Kwissa, Marcin; Metzger, Karin; Oumard, André; Kröger, Andrea; Schirmbeck, Reinhold; Reimann, Jörg; Hauser, Hansjörg (Oxford University Press, 2001-08-15)