Priority Research Area Infections
Microbial Interface Biology
Mission Projects Funding Techniques Publications Staff
M. tuberculosis pathogen variability
Clinical strains of the Mycobacterium tuberculosis complex (MTBC) are genetically more diverse than previously anticipated. We have identified Clade-specific virulence patterns of clinical isolates of the Mycobacterium tuberculosis Complex in human primary macrophages and aerogenically infected mice. Exclusively human-adapted M. tuberculosis lineages, also termed clade I, comprising “modern” lineages, such as Beijing and Euro-American Haarlem strains, showed a significantly enhanced capability to grow in human macrophages compared to that of clade II strains, which include “ancient” lineages, such as, e.g., East African Indian or M. africanum strains.
However, a simple correlation of the inflammatory response profile to a given isolate to the virulence of that same strain was not apparent. We currently focus on the detailed characterization of different pathogenicity programs induced by different strains and lineages. Our findings have significant implications for our understanding of host-pathogen interaction and factors that modulate the outcomes of mycobacterial infections. Future studies addressing the underlying mechanisms and clinical implications need to take into account the diversity of both the pathogen and the host.
Reiling N, et al., MBio. (2013). https://www.ncbi.nlm.nih.gov/pubmed/23900170
Prosser G, el al., Microbes Infect. (2017). https://www.ncbi.nlm.nih.gov/pubmed/27780773
Reiling N, et al., Int J Med Microbiol. (2017). https://www.ncbi.nlm.nih.gov/pubmed/28969988
Intracellular compartments – The M. tuberculosis phagosome
Pathogenic Mycobacterium spp. effectively manipulate the normal progression of their phagosomal compartment and prevent it from fusing with or maturing into an active lysosomal compartment. To identify structural differences between MTBC phagosomes we established a lipid-based, immunomagnetic method to isolate and functionally characterize M. tuberculosis–containing phagosomes from primary host cells.
Electron microscopic and biochemical analyses of the magnetic phagosome-containing fractions provided evidence of an enhanced presence of bacterial antigens and a differential distribution of proteins involved in the endocytic pathway over time as well as cytokine-dependent changes in the phagosomal protein composition.
Due to its relative speed and versatility, the magnetic isolation procedure facilitates the comparative biochemical and mass spectrometric analysis of M. tuberculosis-containing phagosomes. This should promote the identification of essential cellular factors and mechanisms, which are either employed by the pathogen to ensure its intracellular survival or needed by its the host cell to successfully eradicate M. tuberculosis. In addition, the technique is suitable for the isolation of different pathogen-containing vesicles, thus, it may enable comparative analyses of compartments containing of a broad range of intracellular pathogens in order to identify pathogen-specific novel targets for the treatment of infectious diseases.
Steinhäuser C, et al., Traffic. (2013). https://www.ncbi.nlm.nih.gov/pubmed/23231467
Steinhäuser C, et al., Curr Protoc Immunol. (2014). https://www.ncbi.nlm.nih.gov/pubmed/24700322
Reiling N, et al. Int J Med Microbiol. (2017). https://www.ncbi.nlm.nih.gov/pubmed/28969988
Identification of novel regulatory factors during M. tuberculosis infection -
The WNT signaling pathway
Using systematic gene expression profiling of macrophages infected with mycobacteria we were able to identify novel factors which influence antimicrobial effector mechanisms. We and others have recently identified a regulatory role for components of the evoloutionary highly conserved WNT signaling network to be operative at the interface between innate and adaptive immunity in inflammatory and infectious disease settings including tuberculosis. In essence WNTs can exert both, pro- and anti-inflammatory functions on macrophages and other cells of the immune system. We now demonstrate that WNT6 is expressed in granulomatous lesions of M. tuberculosis-infected mice and is involved in macrophage differentiation and proliferation. We identified foamy macrophage-like cells as the primary source of WNT6 in the infected lung. Our findings point towards a novel and unexpected role for WNT6 in macrophage function. Based on these findings and the observation that the majority of WNT6 expressing cells contain lipid vesicles as shown by BODIPY staining, it is intriguing to speculate that M. tuberculosis induces WNT6 to promote the formation of foamy macrophages as a cellular habitat to persist and replicate within the host.
Blumenthal A, et al., Blood (2006). https://www.ncbi.nlm.nih.gov/pubmed/16601243
Neumann J, et al. The FASEB Journal (2010). https://www.ncbi.nlm.nih.gov/pubmed/20667980
Schaale K, et al. Eur J Cell Biol. (2011) . https://www.ncbi.nlm.nih.gov/pubmed/21185106
Schaale K, et al. Journal of Immunology (2013). https://www.ncbi.nlm.nih.gov/pubmed/24123681
Brandenburg J & Reiling N. Front Immunol. (2016). https://www.ncbi.nlm.nih.gov/pubmed/28082976
Identification of new lead compounds against M. tuberculosis – Relevant and rapid test systems
Our macrophages expertise has prompted us to screen the drug efficacy of novel anti-TB lead compounds in M. tuberculosis-infected primary macrophages. Compounds are first analyzed in a newly developed 96 well based medium throughput system based on GFP-expressing M. tuberculosis, which allows the screening of small to medium compound libraries for anti-TB activity. In parallel putative cytotoxic effects on primary macrophages are measured by realtime impedance measurements using human macropahges. Compounds with exert high anti-TB activity but low macrophage cytotoxicity are then tested on M. tuberculosis-infected primary humane macrophages as an inportant step to identfy new anti-TB lead compounds. All three systems have been successfully used and are embedded within the thematic translational transfer unit Tuberculosis (TTU-Tb) within the “Deutsches Zentrum für Infektionsforschung” (DZIF).
Michelucci A, et al., Proc Natl Acad Sci U S A. (2013). https://www.ncbi.nlm.nih.gov/pubmed/23610393
Lehmann J, et al., MedChemCommun. (2016). https://pubs.rsc.org/en/content/articlelanding/2016/md/c6md00231
Kolbe K, et al., Chembiochem. (2017). https://www.ncbi.nlm.nih.gov/pubmed/28249101
Lentz F, et al., Molecules. (2018). https://www.ncbi.nlm.nih.gov/pubmed/29617279
Radloff J, et al., Front Immunol. (2018). https://www.ncbi.nlm.nih.gov/pubmed/30087678