This thesis focuses on the role of chemokine receptors CXCR3 and CCR2 in the inflammatory process and infection control using the zebrafish model. It describes the regulatory interplay between an... Show moreThis thesis focuses on the role of chemokine receptors CXCR3 and CCR2 in the inflammatory process and infection control using the zebrafish model. It describes the regulatory interplay between an atypical and a conventional chemokine receptor during chemotaxis in macrophages, the role of chemotactic signaling in cell polarization and explores an in vivo screening workflow for human anti-inflammatory drugs using zebrafish. Show less
Mycobacterium tuberculosis, the agent of TB, is one of the deadliest human pathogens, infecting one third of the global population. Establishment of infection by mycobacteria relies on complex... Show moreMycobacterium tuberculosis, the agent of TB, is one of the deadliest human pathogens, infecting one third of the global population. Establishment of infection by mycobacteria relies on complex interactions with host innate immune cells, especially macrophages. Once engulfed by macrophages, mycobacteria “usurp” the host cell machineries to facilitate dissemination and to establish an intracellular niche for survival and replication. To investigate how mycobacteria force the immune cells to support infection, we explored the chemokine pathway, best known for its capability to induce cell migration. To dissect the interplay between immune cells and the pathogen, we modelled human TB using the zebrafish-Mycobacterium marinum natural host-pathogen pair, which is attractive for the excellent optical accessibility of the zebrafish larvae and the possibility to apply genetic tools to impair the chemokine signaling. We show that depletion of either CXCR3 or CXCR4 axes are beneficial to the host. Exploitation of CXCR3 signaling leads to macrophage recruitment and to transcriptional changes in macrophages that make them more permissive for mycobacterial intracellular persistence. Activating CXCR4 signaling triggers instead vascularization of the nascent tuberculous granulomas, which in turn supports expansion of the infection. Therefore, inhibitions of these pathways represent promising host-directed therapeutic avenues to counteract mycobacterial diseases. Show less
Mladic, M.; Scholten, D.J.; Wijtmans, M.; Falck, D.; Leurs, R.; Niessen, W.M.A.; ... ; Kool, J. 2015
Chemokines are signaling proteins that direct the migration and function of many cell types during development and responses of the immune system. The zebrafish embryo model is highly suited to... Show moreChemokines are signaling proteins that direct the migration and function of many cell types during development and responses of the immune system. The zebrafish embryo model is highly suited to investigate cell migration because of its optical transparency and availability of transgenic lines with fluorescently labeled cell types of the innate immune system. In this thesis, we analyzed the phylogenetic relationships between zebrafish and human chemokines and used Salmonella and Mycobacterium infection models to study the function of a zebrafish chemokine receptor gene, cxcr3.2, homologous to human CXCR3. Our data have demonstrated that cxcr3.2 is predominantly expressed in macrophages of the zebrafish embryo and plays an essential role in bacterial-induced macrophage migration and control of local infections. Furthermore, we used in vivo cell migration assays in wild type and cxcr3.2 mutant embryos to discover the putative ligand of the cxcr3.2 receptor. Injection of Cxcl11, an infection-inducible chemokine, resulted in the directional migration of macrophages in a cxcr3.2-dependent manner. As the first ligand-receptor pair with a proposed function in migration of zebrafish macrophages in response to bacterial infection, the identification of Cxcl11-Cxcr3.2 interaction is an important step towards understanding the chemokine signaling network underlying innate immune responses in the zebrafish model. Show less
