• Strict control of transgene expression in a mouse model for sensitive biological applications based on RMCE compatible ES cells.

      Sandhu, U; Cebula, M; Behme, S; Riemer, P; Wodarczyk, C; Metzger, D; Reimann, J; Schirmbeck, R; Hauser, H; Wirth, D; et al. (2011-01-01)
      Recombinant mouse strains that harbor tightly controlled transgene expression proved to be indispensible tools to elucidate gene function. Different strategies have been employed to achieve controlled induction of the transgene. However, many models are accompanied by a considerable level of basal expression in the non-induced state. Thereby, applications that request tight control of transgene expression, such as the expression of toxic genes and the investigation of immune response to neo antigens are excluded. We developed a new Cre/loxP-based strategy to achieve strict control of transgene expression. This strategy was combined with RMCE (recombinase mediated cassette exchange) that facilitates the targeting of genes into a tagged site in ES cells. The tightness of regulation was confirmed using luciferase as a reporter. The transgene was induced upon breeding these mice to effector animals harboring either the ubiquitous (ROSA26) or liver-specific (Albumin) expression of CreER(T2), and subsequent feeding with Tamoxifen. Making use of RMCE, luciferase was replaced by Ovalbumin antigen. Mice generated from these ES cells were mated with mice expressing liver-specific CreER(T2). The transgenic mice were examined for the establishment of an immune response. They were fully competent to establish an immune response upon hepatocyte specific OVA antigen expression as indicated by a massive liver damage upon Tamoxifen treatment and did not show OVA tolerance. Together, this proves that this strategy supports strict control of transgenes that is even compatible with highly sensitive biological readouts.
    • Synthetic rewiring and boosting type I interferon responses for visualization and counteracting viral infections.

      Gödecke, Natascha; Riedel, Jan; Herrmann, Sabrina; Behme, Sara; Rand, Ulfert; Kubsch, Tobias; Cicin-Sain, Luka; Hauser, Hansjörg; Köster, Mario; Wirth, Dagmar; et al. (Oxford Academic, 2020-11-18)
      Mammalian first line of defense against viruses is accomplished by the interferon (IFN) system. Viruses have evolved numerous mechanisms to reduce the IFN action allowing them to invade the host and/or to establish latency. We generated an IFN responsive intracellular hub by integrating the synthetic transactivator tTA into the chromosomal Mx2 locus for IFN-based activation of tTA dependent expression modules. The additional implementation of a synthetic amplifier module with positive feedback even allowed for monitoring and reacting to infections of viruses that can antagonize the IFN system. Low and transient IFN amounts are sufficient to trigger these amplifier cells. This gives rise to higher and sustained-but optionally de-activatable-expression even when the initial stimulus has faded out. Amplification of the IFN response induced by IFN suppressing viruses is sufficient to protect cells from infection. Together, this interfaced sensor/actuator system provides a toolbox for robust sensing and counteracting viral infections.
    • Targeting cardiac fibrosis with engineered T cells.

      Aghajanian, Haig; Kimura, Toru; Rurik, Joel G; Hancock, Aidan S; Leibowitz, Michael S; Li, Li; Scholler, John; Monslow, James; Lo, Albert; Han, Wei; et al. (Nature publishing group(NPG), 2019-09-11)
      Fibrosis is observed in nearly every form of myocardial disease1. Upon injury, cardiac fibroblasts in the heart begin to remodel the myocardium by depositing excess extracellular matrix, resulting in increased stiffness and reduced compliance of the tissue. Excessive cardiac fibrosis is an important factor in the progression of various forms of cardiac disease and heart failure2. However, clinical interventions and therapies that target fibrosis remain limited3. Here we demonstrate the efficacy of redirected T cell immunotherapy to specifically target pathological cardiac fibrosis in mice. We find that cardiac fibroblasts that express a xenogeneic antigen can be effectively targeted and ablated by adoptive transfer of antigen-specific CD8+ T cells. Through expression analysis of the gene signatures of cardiac fibroblasts obtained from healthy and diseased human hearts, we identify an endogenous target of cardiac fibroblasts-fibroblast activation protein. Adoptive transfer of T cells that express a chimeric antigen receptor against fibroblast activation protein results in a significant reduction in cardiac fibrosis and restoration of function after injury in mice. These results provide proof-of-principle for the development of immunotherapeutic drugs for the treatment of cardiac disease.
    • Targeting Kaposi's Sarcoma-Associated Herpesvirus ORF21 Tyrosine Kinase and Viral Lytic Reactivation by Tyrosine Kinase Inhibitors Approved for Clinical Use

      Beauclair, Guillaume; Naimo, Eleonora; Dubich, Tatyana; Rückert, Jessica; Koch, Sandra; Dhingra, Akshay; Wirth, Dagmar; Schulz, Thomas F; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (American Society for Microbiology (ASM), 2019-12-11)
      Kaposi's Sarcoma-associated herpesvirus (KSHV) is the cause of three human malignancies, Kaposi's Sarcoma, Primary Effusion Lymphoma and the plasma cell variant of Multicentric Castleman's Disease. Previous research has shown that several cellular tyrosine kinases play crucial roles during several steps in the virus replication cycle. Two KSHV proteins also have protein kinase function: open reading frame (ORF) 36 encodes a serin-threonine kinase, while ORF21 encodes a thymidine kinase (TK), which has recently been found to be an efficient tyrosine kinase. In this study, we explore the role of the ORF21 tyrosine kinase function in KSHV lytic replication. By generating a recombinant KSHV mutant with an enzymatically inactive ORF21 protein we show that the tyrosine kinase function of ORF21/TK is not required for the progression of the lytic replication in tissue culture, but that it is essential for the phosphorylation and activation to toxic moieties of the antiviral drugs zidovudine and brivudine. In addition, we identify several tyrosine kinase inhibitors, already in clinical use against human malignancies, which potently inhibit not only ORF21 TK kinase function, but also viral lytic reactivation and the development of KSHV-infected endothelial tumors in mice. As they target both cellular tyrosine kinases and a viral kinase, some of these compounds might find a use in the treatment of KSHV-associated malignancies.Importance: Our findings address the role of KSHV ORF21 as a tyrosine kinase during lytic replication and the activation of prodrugs in KSHV-infected cells. We also show the potential of selected clinically approved tyrosine kinase inhibitors to inhibit KSHV TK, KSHV lytic replication, infectious virions release and the development of an endothelial tumor. Since they target both cellular tyrosine kinases supporting productive viral replication and a viral kinase, these drugs, which are already approved for clinical use, may be suitable for repurposing for the treatment of KSHV-related tumors in AIDS patients or transplant recipients.
    • 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, Hansjoerg; 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.
    • Towards rational engineering of cells: Recombinant gene expression in defined chromosomal loci

      Nehlsen, Kristina; da Gama-Norton, Leonor; Schucht, Roland; Hauser, Hansjörg; Wirth, Dagmar (2011-11-22)
    • Toxin-antitoxin based transgene expression in mammalian cells.

      Nehlsen, K; Herrmann, S; Zauers, J; Hauser, Hansjoerg; Wirth, D; Helmholtz Centre for Infection Research, Braunschweig, Germany. (2010-03)
      Long-term, recombinant gene expression in mammalian cells depends on the nature of the transgene integration site and its inherent properties to modulate transcription (epigenetic effects). Here we describe a method by which high transgene expression is achieved and stabilized in extensively proliferating cultures. The method is based on strict co-expression of the transgene with an antitoxin in cells that express the respective toxin. Since the strength of antitoxin expression correlates with an advantage for cell growth, the cells with strong antitoxin expression are enriched over time in cultures of heterogeneous cells. This principle was applied to CHO cell lines that conditionally express the toxin kid and that are transduced to co-express the antitoxin kis together with different transgenes of interest. Cultivation of pools of transfectants that express the toxin steadily increase their transgene expression within several weeks to reach a maximum that is up to 120-fold over the initial status. In contrast, average transgene expression drops in the absence of toxin expression. Together, we show that cells conditionally expressing kid can be employed to create overexpressing cells by a simple coupling of kis to the transgene of interest, without further manipulation and in absence of selectable drugs.
    • Type I interferon receptor signaling delays Kupffer cell replenishment during acute fulminant viral hepatitis.

      Borst, Katharina; Frenz, Theresa; Spanier, Julia; Tegtmeyer, Pia-Katharina; Chhatbar, Chintan; Skerra, Jennifer; Ghita, Luca; Namineni, Sukumar; Lienenklaus, Stefan; Köster, Mario; et al. (2017-12-21)
      Virus-induced fulminant hepatitis is a major cause of acute liver failure. During acute viral hepatitis the impact of type I interferon (IFN-I) on myeloid cells, including liver-resident Kupffer cells (KC), is only partially understood. Herein, we dissected the impact of locally induced IFN-I responses on myeloid cell function and hepatocytes during acute liver inflammation. Two different DNA-encoded viruses, vaccinia virus (VACV) and murine cytomegalovirus (MCMV), were studied. In vivo imaging was applied to visualize local IFN-β induction and IFN-I receptor (IFNAR) triggering in VACV-infected reporter mice. Furthermore, mice with a cell type-selective IFNAR ablation were analyzed to dissect the role of IFNAR signaling in myeloid cells and hepatocytes. Experiments with Cx3cr1 VACV infection induced local IFN-β responses, which lead to IFNAR signaling primarily within the liver. IFNAR triggering was needed to control the infection and prevent fulminant hepatitis. The severity of liver inflammation was independent of IFNAR triggering of hepatocytes, whereas IFNAR triggering of myeloid cells protected from excessive inflammation. Upon VACV or MCMV infection KC disappeared, whereas infiltrating monocytes differentiated to KC afterwards. During IFNAR triggering such replenished monocyte-derived KC comprised more IFNAR-deficient than -competent cells in mixed bone marrow chimeric mice, whereas after the decline of IFNAR triggering both subsets showed an even distribution. Upon VACV infection IFNAR triggering of myeloid cells, but not of hepatocytes, critically modulates acute viral hepatitis. During infection with DNA-encoded viruses IFNAR triggering of liver-infiltrating blood monocytes delays the development of monocyte-derived KC, pointing towards new therapeutic strategies for acute viral hepatitis.
    • Uncoupling of the dynamics of host-pathogen interaction uncovers new mechanisms of viral interferon antagonism at the single-cell level.

      Rand, Ulfert; Hillebrand, Upneet; Sievers, Stephanie; Willenberg, Steffi; Köster, Mario; Hauser, Hansjörg; Wirth, Dagmar (Oxford University Press, 2014-06-03)
      Antiviral defence in mammals is mediated through type-I interferons (IFNs). Viruses antagonise this process through expression of IFN antagonist proteins (IAPs). Understanding and modelling of viral escape mechanisms and the dynamics of IAP action has the potential to facilitate the development of specific and safe drugs. Here, we describe the dynamics of interference by selected viral IAPs, NS1 from Influenza A virus and NS3/4A from Hepatitis C virus. We used Tet-inducible IAP gene expression to uncouple this process from virus-driven dynamics. Stochastic activation of the IFN-β gene required the use of single-cell live imaging to define the efficacy of the inhibitors during the virus-induced signalling processes. We found significant correlation between the onset of IAP expression and halted IFN-β expression in cells where IFN-β induction had already occurred. These data indicate that IAPs not only prevent antiviral signalling prior to IFN-β induction, but can also stop the antiviral response even after it has been activated. We found reduced NF-κB activation to be the underlying mechanism by which activated IFN expression can be blocked. This work demonstrates a new mechanism by which viruses can antagonise the IFN response.