New drugs for use as tuberculosis (TB) treatment are needed due to the constrains of classical antibiotics against TB and the rise of antibiotic-resistant strains, making TB a harder and harder... Show moreNew drugs for use as tuberculosis (TB) treatment are needed due to the constrains of classical antibiotics against TB and the rise of antibiotic-resistant strains, making TB a harder and harder disease to treat. This thesis is focused on using the in vivo whole animalzebrafish embryo model for TB to evaluate potential anti-TB host-directed therapeutics (HDTs) arising from in vitro screens. Although in vitro screens for HDTs using cellular models can be performed at high throughput, a limiting step is the validation in whole animal models and translation of results to clinical applications. Due to the complex infection dynamics of mycobacteria, the use of whole animal models is indispensable in research into TB and the zebrafish model has contributed key findings about host-pathogen dynamics during mycobacterial infection. One of the most promising host targets of HDTs is autophagy, which is recognized as an important host-protective pathway. Boosting autophagy levels using HDTs could be a way to overcome the pathogen’s autophagy evasion strategies and could therefore be a promising therapeutic route. For this thesis we took advantage of the possibilities of the zebrafish embryo model for TB and the zebrafish toolkit to study several autophagy-modulating HDTs as potential anti-TB drugs. Show less
The work in this thesis describes the fundamental role of Lkb1 as a conductor of metabolism-related processes in zebrafish larvae. We show that Lkb1 is essential for the regulation of glucose... Show moreThe work in this thesis describes the fundamental role of Lkb1 as a conductor of metabolism-related processes in zebrafish larvae. We show that Lkb1 is essential for the regulation of glucose metabolism, the activation of autophagy, and hematopoiesis under conditions of metabolic stress. Furthermore, we also uncovered gene transcription profiles and hematological characteristics that are specific to lkb1 larvae, and independent of metabolic stress. Finally, we illustrate and highlight the potential of lkb1 larvae as screening platform in research related to metabolism, hematopoiesis, and tumors bearing LKB1 mutations. Overall, we have strengthened the value of lkb1 zebrafish larvae as a model to study the effects of Lkb1-inactivation on various metabolism-related processes Show less
The effective treatment of tuberculosis (TB) remains a major challenge to global health. Drug-resistant Mycobacterium tuberculosis (Mtb) strains and co-infection with HIV further increase the... Show moreThe effective treatment of tuberculosis (TB) remains a major challenge to global health. Drug-resistant Mycobacterium tuberculosis (Mtb) strains and co-infection with HIV further increase the difficulty of controlling TB. Thus, under the current situation, it is essential to develop effective treatment strategies for Mtb infections. Autophagy is a lysosomal degradation process and substantial experimental evidence has demonstrated that autophagy is an important host immune defense mechanism against mycobacterial infection. However, the development of effective therapies requires a better understanding of the interaction between the host and invading pathogens to identify host processes that can be targeted. A useful tool for such studies is the zebrafish model for TB. Zebrafish can be infected with Mycobacterium marinum (Mm), which is closely related to Mtb and causes similar disease characteristics. Taking advantage of the zebrafish TB model, this thesis presents new in vivo evidence for the important function of autophagy to inhibit mycobacterial proliferation inside macrophages. Furthermore, this study supports that stimulating the innate host defense processes that are dependent on the autophagy modulator, Dram1, and the selective autophagy receptors, p62 and Optineurin, could be a useful strategy to explore for adjunctive treatment of antibiotic-resistant TB infections. Show less
Control of infectious diseases poses continuous challenges for human health. Salmonella bacteria are a major cause of gastrointestinal infections and systemic disease like typhoid fever. We used... Show moreControl of infectious diseases poses continuous challenges for human health. Salmonella bacteria are a major cause of gastrointestinal infections and systemic disease like typhoid fever. We used zebrafish-Salmonella infection models to study host immune responses to Salmonella, particularly focusing on the role of the autophagy machinery. Autophagy and a related process known as Lc3-associated phagocytosis (LAP) trap invading microbes in intracellular vesicles and eventually eliminate them through the lysosomal degradation pathway. We show that macrophages and neutrophils trap Salmonella in Lc3-decorated phagosomes by a process dependent on the host factors Rubicon and NADPH oxidase, which generates anti-bacterial reactive oxygen species. This process could be defined as LAP as it requires some but not all components of the autophagy machinery. Genetic inhibition of LAP and ablation of macrophages resulted in hypersusceptibility to infections with both wild type and attenuated strains, revealing that LAP is an essential line of defense against Salmonella during systemic disease, when macrophages are the main carriers of the infection. Our studies also revealed a novel functional link between the autophagy modulator Dram1 and induction of LAP. This work encourages further studies aimed at the identification of autophagy modulating drugs for host-directed therapy of antibiotic-resistant Salmonella infections. Show less
