Infection Immunology
Granuloma formation is a hallmark of Mycobacterium tuberculosis (Mtb) infection and represents the histological correlate of inflammatory tissue responses generally associated with protective immunity. In most cases the immune system of the host is capable to control the pathogen in these protective lung granulomas. However, in some infected individuals the disease tuberculosis (TB) develops when a formerly protective granuloma loses the capability to keep mycobacterial replication in check. It increases in size and transforms in a damaging granuloma that eventually necrotizes. The Infection Immunology research group wants to understand the cytokine-mediated regulation of (i) protection and (ii) pathology within these two types of TB-associated granulomas (Fig. 1) in order to dissect protective and pathology-promoting mechanisms to develop adjuvant vaccination and therapy strategies (Control and Care). In this respect, (iii) novel antibiotics and host directed therapeutics should be evaluated in optimized experimental models to improve anti TB therapy and/or vaccination.
Th1/Th17-mediated formation of protective granulomas
Interferon-gamma (IFN-γ) and interleukin (IL)-17A are two prototype T helper (Th) 1 and Th17 cytokines, respectively, that play a critical role in protection against infections with intracellular pathogens. As we have previously shown, mice lacking IL-23 or IL-17A production are highly susceptible to infection identifying an IL-23-dependent Th17 immune reaction as an important effector arm of protective immune responses (Hölscher 2001 J Immunol 167:6957; Schulz 2008 Int Immunol 20:1129; Werninghaus 2009 J Exp Med 206:89; Hernandez 2015 Nat Immunol). On the other hand, Th17 cells also play an essential role in the development of chronic inflammatory diseases, especially those mediated by T effector cells. For example, Th17 cells have been shown to promote the pathogenesis of various inflammatory and autoimmune diseases (Hölscher 2005 Curr Opin Investig Drugs 6:489; Paus 2009 J Am Soc Nephrol 20: 969; Gelderblom 2012 Blood 120: 3793). This proverbial function of Th17 cytokines as a “double-edged sword” is highlighted by our studies of TB in IL-27 receptor-alpha (Rα)-deficient mice. In these animals, an enhanced inflammatory immune response to Mtb infection results in a better control of mycobacterial growth but also lead to immunopathology and premature death (Hölscher 2005 J Immunol 167:6957).
We could now show that these opposed effects are exclusively mediated by an elevated expression of IL-17A. Of importance, however, is that the increased levels of IL-17A lead to the formation of highly structured „protective“ granulomas (Fig. 2). The exact mechanisms how these granulomas are induced by IL-17A and which mechanism expressed in these lesions in fact promote protection is not clear at the moment. Moreover, given that an increased expression of IL-17A fosters protective immune responses, a controlled increase in IL-17A or of downstream effects may represent an immunomodulatory approach for host directed therapy. Nevertheless, further detailed analysis of regulatory and of IL-17A-dependent cell type-specific mechanisms that mediate its protective effect are imperative. References: Sodenkamp 2011 Eur J Cell Biol 90:505; Sodenkamp 2012 Immunobiol 217:996; Heitmann 2013 Immunobiol 218:506; Erdmann 2013 Immunobiol 6:910; Behrends 2013 PLoS One 8:e57379; Berod 2014 PLoS One 9:e102804; Böhme 2016 Immunol; Erdmann 2016 Sci Rep; Stüve 2018 Front Immunol; Erdmann 2018 Muc Immunol.
Th2-dependent development of damaging granulomas
Until today, factors influencing the course of Mtb infection are only incompletely defined. One important reason is the fact that genetically or immunologically tractable mouse models do not exist that displays the characteristic features of granulomas in TB patients: centrally necrotizing lesions, a strict stratification of a fibrous capsule that separates the necrotizing granuloma from the adjoining tissue, foamy macrophages found adjacent to the fibrous capsule within the necrotic lesion, and most importantly hypoxia. Because lipid-containing foamy macrophages and necrosis-related hypoxia might be key factors in the pathogenesis of post-primary TB and eventually the distribution and success of Mtb, the Infection Immunology research group developed a mouse model in which Mtb infection results in granuloma necrosis strongly resembling the pathology of human TB (Fig. 3). In these IL-13-overexpressing (tg) mice, arginase-1-expressing alternatively activated macrophages, which have previously shown by us to promote susceptibility to intracellular pathogens (Herbert 2004 Immunity 20:623, Hölscher 2006 J Immunol 176:1115, Schreiber 2009 J Immunol 183:1301), drive the typical pathology with centrally necrotizing granulomas, a fibrous rim and foamy macrophages. Because IL-13 signals through the IL-4 receptor-alpha (α) we performed genetic analysis in humans and found a mutation in this receptor chain in humans that was linked to the degree of pathology in TB patients. These genetic association study further supports our assumption that IL-13/IL-4Rα-dependent mechanisms are involved in mediating tissue pathology of human TB. As the pathology observed in Mtb-infected IL-13tg mice display many features of post-primary TB in humans, this mouse model is an ideal tool to study the progression of TB and to determine factors important for the clinical outcome. References: Heitmann 2014 J Pathol; Hölscher 2016 Mediators Inflamm; Herrtwich 2016 Cell; Schmok 2017 Front Immunol.
Evaluation of antibiotics in optimized preclinical models
Drug resistant Mtb strains represent the major threat for the global control of TB and new anti-TB drugs are urgently needed. Drug development against multidrug-resistant (MDR)-TB requires preclinical testing in optimized models that mimic pathobiological aspects of human TB. Within the German Centre for Infection Research (DZIF), the Infection Immunology research group has implemented in collaboration with other scientists a preclinical test station (TTU-TB “New Drugs and Regimen”) which further develops existing models of in vitro and in vivo drug testing to advance several selected compounds, or therapeutic modalities, from “candidate” to “potential regimen for human use” status. One important aspects of the DZIF infrastructure TTU-TB „MycoDrug and Trials“ executed by the Infection Immunology research group is to further develop the animal model of IL-13tg mice (see above) for the in vivo analysis of anti-mycobacterial compounds under more physiological conditions resembling the pathology of human post-primary TB. Based on proof of principle studies with standard antibiotics IL-13tg mice will further serve as a “close to human” model to proof the efficacy of novel anti-mycobacterial compounds under physiological conditions in vivo.
The development of a vaccine against rickettsioses
Rickettsioses are emerging febrile, potentially fatal infectious diseases caused by small intracellular bacteria (rickettsiae). Rickettsial infections are highly prevalent in developing countries and a serious global health threat. Within the past decades, rickettsial infections have been occurring around the world with increasing frequency and geographic distribution. Since the bacteria only respond to very few antibiotics, treatment with wrong antibiotics or delayed treatment due to a lack of diagnosis or misdiagnosis often leads to severe disease courses. It is problematic that there is evidence of the development of antibiotic resistance. In addition, some rickettsiae species can persist and cause recurrent diseases regardless of antibiotic treatment. Finally, certain rickettsial species are classified as potential biological weapons. For these reasons, prophylactic vaccines against the infection with these bacteria are urgently needed. The aim of this project is to gain deeper insight into protective immune mechanisms and the identification of immunogenic determinants of rickettsial pathogens that can serve as a vaccine. Rickettsia typhi, the causative agent of endemic typhus, is used as a model organism for these studies that are funded by the German Research Foundation (DFG, No. OS583) and conducted by Dr. Anke Osterloh.
Awarded with the Memento Award for Neglected Diseases 2020
- BMBF; DZIF TTU-TB 02.705 Infrastructure „Myco Drug and Trials“
- BMBF; DZIF TTU-TB 02.806 Project „New Drugs and Regimen“
- BMBF; DZIF TTU-TB 02.906 FlexFund „Optimization of mycobacterial thioredoxin reductase inhibitors, novel lead compounds against M. tuberculosis“
- BMBF; DZIF TTU-TI 07.003_Garrelts MD Project „Local activity of anti-TB therapeutics in highly stratified human-like lesions of a novel pre-clincial mouse model“
- BMBF, DZIF „InhibitMycoRex: Optimization of mycobacterial thioredoxin reductase inhibitors, novel lead compounds against M. tuberculosis“
- DFG; IRTG191: "Immunoregulation of Inflammation in Allergy and Infection“: Project B6 "ProThe impact of Tr1 cells in aged mice on susceptibility and vaccination efficacy in TB“
- DFG; IRTG191: "Immunoregulation of Inflammation in Allergy and Infection“: MD Project "Spatial analysis of host and pathogen responses in highly structured tuberculous granulomas after laser capture microdissection“
- DFG; GRK 1727: „Modulation von Autoimmunität“ : Projekt A3: "Cell type-specific effects of interleukin-17 in Epidermolysis bullous acquisita"
- EU / Horizon 2020: CORVOS / Marie Sklodowska-Curie Joint European PhD:“ Complement regulation and variations in opportunistic infections“
- EU / Horizon 2020: ETBRA / „European tuberculosis regimen accelerator“
- Biochemical methods
- Cultivation of hybridoma, production and purification of monoclonal antibodies
- Cultivation, preparation and identification of BSL2 and BSL3 pathogens (e.g. Mycobacterium tuberculosis or Trypanosoma cruzi)
- Infection of experimental mice (subcutaneous, intravenous, intraperitoneal, aerosol infection with mycobacteria)
- In vitro differentiation, infection and analysis of bone marrow derived macrophages and dendritic cells
- In vitro differentiation of TH1, TH2 and TH17 cells
- Isolation of organs from experimental mice, preparation of single cell suspension and cell sorting
- Isolation of cells and granulomas from perfused lungs and livers of infected animals
- Magnetic cell sorting
- Flowcytometry and immunofluorescence
- Histological and immunohistochemical techniques
- Confocal microscopy
- Quantitative RT-PCR, real time PCR
- Detection of antibodies, cytokines and chemokines intermediates in tissue culture supernatants, tissue homogenates and serum/plasma
- Cytometric bead arrays
- Determination of reactive nitrogen intermediates and quantification of arginase activity
- Cytokine bioassays
- Functional T cell assays (proliferation, antigen-specific recall and cytokine-secretion assays, ELISPOT, CTL assays, preparation of Mtb-specific class I and class II tetramers and staining of specific CD4+ and CD8+ T cells)
2024
Götz, MP, Duque Villegas, MA, Fageräng, B, Kerfin, A, Skjoedt, M-O, Garred, P & Rosbjerg, A 2024, 'Transient Binding Dynamics of Complement System Pattern Recognition Molecules on Pathogens', JOURNAL OF IMMUNOLOGY, Jg. 212, Nr. 9, S. 1493-1503. https://doi.org/10.4049/jimmunol.2300768
Walter, K, Te Brake, LHM, Lemm, A-K, Hoelscher, M, Svensson, EM, Hölscher, C & Heinrich, N 2024, 'Investigating the treatment shortening potential of a combination of bedaquiline, delamanid and moxifloxacin with and without sutezolid, in a murine tuberculosis model with confirmed drug exposures', JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY. https://doi.org/10.1093/jac/dkae266
2022
Brandenburg, J, Heyckendorf, J, Marwitz, F, Zehethofer, N, Linnemann, L, Gisch, N, Karaköse, H, Reimann, M, Kranzer, K, Kalsdorf, B, Sanchez-Carballo, P, Weinkauf, M, Scholz, V, Malm, S, Homolka, S, Gaede, KI, Herzmann, C, Schaible, UE, Hölscher, C, Reiling, N & Schwudke, D 2022, 'Tuberculostearic Acid-Containing Phosphatidylinositols as Markers of Bacterial Burden in Tuberculosis', ACS infectious diseases, Jg. 8, Nr. 7, S. 1303-1315. https://doi.org/10.1021/acsinfecdis.2c00075
Kokesch-Himmelreich, J, Treu, A, Race, AM, Walter, K, Hölscher, C & Römpp, A 2022, 'Do Anti-tuberculosis Drugs Reach Their Target?─High-Resolution Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging Provides Information on Drug Penetration into Necrotic Granulomas', ANALYTICAL CHEMISTRY , Jg. 94, Nr. 14, S. 5483-5492. https://doi.org/10.1021/acs.analchem.1c03462
Osterloh, A 2022, 'Vaccination against Bacterial Infections: Challenges, Progress, and New Approaches with a Focus on Intracellular Bacteria', Vaccines, Jg. 10, Nr. 5, 751. https://doi.org/10.3390/vaccines10050751
Ritter, K, Behrends, J, Rückerl, D, Hölscher, A, Volz, J, Prinz, I & Hölscher, C 2022, 'High-Dose Mycobacterium tuberculosis H37rv Infection in IL-17A- and IL-17A/F-Deficient Mice', Cells, Jg. 11, Nr. 18, 2875. https://doi.org/10.3390/cells11182875
Ritter, K, Rousseau, J & Hölscher, C 2022, 'Interleukin-27 in Tuberculosis: A Sheep in Wolf's Clothing?', FRONTIERS IN IMMUNOLOGY, Jg. 12, S. 810602. https://doi.org/10.3389/fimmu.2021.810602
Walter, K, Kokesch-Himmelreich, J, Treu, A, Waldow, F, Hillemann, D, Jakobs, N, Lemm, A-K, Schwudke, D, Römpp, A & Hölscher, C 2022, 'Interleukin-13 overexpressing mice represent an advanced pre-clinical model for detecting the distribution of anti-mycobacterial drugs within centrally necrotizing granulomas', ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Jg. 66, Nr. 6, S. e0158821. https://doi.org/10.1128/AAC.01588-21
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