In this thesis we describe our work regarding the identification of novel biomarkers, host targets and candidate pharmacological compounds for the development of therapies against various... Show moreIn this thesis we describe our work regarding the identification of novel biomarkers, host targets and candidate pharmacological compounds for the development of therapies against various intracellular bacterial infections, focusing primarily on the interplaybetween tuberculosis and diabetes mellitus. We conducted two longitudinal cohort studies in South Africa and Indonesia, and we applied unbiased and selective transcriptomic approaches to identify novel biomarker profiles in tuberculosis patients with concomitant diabetes or hyperglycaemia. Further, we performed experiments with standardized in vitro cellular infection models for drug discovery. We identified potential host targets during Mycobacterium tuberculosis infections and we describe the role of central metabolic pathways bacterial infections in human macrophages. Show less
A 23-year-old man presented with a painful swelling of his left shin approximately 5 weeks after a very mild trauma. He had not experienced fever, abdominal pain, or diarrhea. Magnetic resonance... Show moreA 23-year-old man presented with a painful swelling of his left shin approximately 5 weeks after a very mild trauma. He had not experienced fever, abdominal pain, or diarrhea. Magnetic resonance images were compatible with chronic osteomyelitis. The cultures of the bone biopsy showed growth of Salmonella enterica serovar Enteritidis. Blood cultures remained sterile, there were no signs of a carrier state, and no immune deficiency could be found. After surgical debridement, the patient was treated with ceftriaxone and co-trimoxazole and later ciprofloxacin because of an allergic reaction. Nontyphoidal Salmonella osteomyelitis is rare in immunocompetent adults without a hemoglobinopathy. The treatment consists of surgical debridement and prolonged antibiotics. Show less
Endocytosis is a crucial mechanism for the cell to maintain homeostasis. By vesicular transport the cell is able to take up cargo from the cell surface, send molecules to the plasma membrane for... Show moreEndocytosis is a crucial mechanism for the cell to maintain homeostasis. By vesicular transport the cell is able to take up cargo from the cell surface, send molecules to the plasma membrane for excretion or to regulate positioning of internalized cargo in the cell. This thesis describes the regulation of transport complexes associated to these vesicles that determines their movement in the cell. Through recruitment of RAB7GAP the GTPase Rab7 can be removed from the vesicular membrane, allowing for transport mediated by another GTPase called Arl8b.The second part of this thesis focusses on the bacterium Salmonella which manipulates the endosomal system in order to create a niche that supports its own survival. By excretion of effector molecules Salmonella imodulates the membrane content of vesicles and thereby prevents its own lysosomal degradation. This allows Salmonella to create a Salmonella containing vesicle compartment that benefits its own survival in the host cell. This thesis describes how release of these effector molecules can support transformation of host cells. These results explain the strrong correlation between gallbladder cancer and chronic S. Typhi infections observed in patients from countries like India, where S. Typhi infections are still common. Show less
Antibiotic resistance is an increasing problem in the battle against (bacterial) infectious diseases. The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) threatens to render... Show moreAntibiotic resistance is an increasing problem in the battle against (bacterial) infectious diseases. The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) threatens to render tuberculosis (TB) untreatable. Efforts to develop novel antibiotics have so far been unsuccessful, calling for additional approaches for treatment of bacterial infections. Intracellular pathogens like Mtb and Salmonella can survive in the host by manipulating host cell signaling. This provides opportunities for novel therapeutic strategies by targeting the host, rather than the bacterium (host-directed therapy). In this thesis we report the development and application of novel (in vitro and in vivo) methods for identifying host genes and proteins involved in host control of intracellular bacteria, as well as chemical compounds that target host molecules as a basis for drug development for host-directed therapies. As a result, we report the identification of RTK inhibitors, the novel kinase inhibitor 97i, the human kinase family PCTAIRE and the host protein DRAM1 as promising leads for further drug development for host-directed therapeutic strategies for intracellular bacterial infections. Show less
Vaccines can serve as essential tools to prevent bacterial diseases via the induction of long-lasting IgG responses. The efficacy of such vaccines depends on the effector mechanisms triggered by... Show moreVaccines can serve as essential tools to prevent bacterial diseases via the induction of long-lasting IgG responses. The efficacy of such vaccines depends on the effector mechanisms triggered by IgG. The complement system and Fc-gamma receptors (FcRs) can potentially play a crucial role in IgG-mediated immunity against bacterial diseases. However, their relative importance in vivo is unclear, and has been the object of controversy and debate. In this brief study, we have used gene-targeted mice lacking either FcRI, II, II and IV or the C3 complement component as well as a novel mouse strain lacking both C3 and FcRs to conclusively show the essential role of complement in antibody-mediated host resistance to Salmonella enterica systemic infection. By comparing the effect of IgG2a antibodies against Salmonella O-antigen in gene-targeted mice, we demonstrate that the complement system is essential for the IgG-mediated reduction of bacterial numbers in the tissues. Show less
Aboutaleb, N.; Kuijper, E.J.; Dissel, J.T. van 2014
Part 1: The role of IL-23 in inducing IFN-g production and in the initiation of a Th1 response. Part 2: Genetic variations in the type-1 cytokine pathway. Part 3: Treatment options for a genetic... Show morePart 1: The role of IL-23 in inducing IFN-g production and in the initiation of a Th1 response. Part 2: Genetic variations in the type-1 cytokine pathway. Part 3: Treatment options for a genetic deficiency in the type-1 cytokine pathway Show less
MHC class II antigen presentation by B cells is important to activate CD4+ T cells that stimulate the B cell to produce antibodies. Besides this, disruption of MHC class II antigen presentation... Show moreMHC class II antigen presentation by B cells is important to activate CD4+ T cells that stimulate the B cell to produce antibodies. Besides this, disruption of MHC class II antigen presentation could play a role in immune escape by tumor cells. This thesis describes MHC class II antigen presentation by B cells during bacterial infections and leukemia. We show that, in contrast to the current dogma, human B cells are able to phagocytose whole, living Salmonella bacteria via their B cell receptor (BCR). Salmonella survives intracellular and is transported by the B cell to the spleen where Salmonella can infect other cells. Although Salmonella uses the B cell to disseminate and escape the immune system, uptake of Salmonella by B cells also results in a good immune response consisting of specific antibody production, antigen presentation and activation of both CD4+ T helper cells and cytotoxic CD8+ T cells that are able to eliminate infected cells. Many leukemic cells express MHC class II. For AML (acute myeloid leukemia) we show that expression of the self-peptide CLIP could be a measure for immune escape because a high percentage of HLA-DR+/CLIP- blasts correlates with a longer disease-free survival. In B-CLL (chronic lymphocytic leukemia), the percentage of activated CD4+ and CD8+ T cells is enhanced and inversely correlated to CLIP. In addition, transcription of all MHC class II genes is increased and B-CLL patients with high HLA-DOA mRNA levels have a less favorable prognosis. Show less
The last decade has witnessed an increased occurrence of bacterial resistance against antibiotics. The first part of this thesis describes the discovery of a novel target, protein kinase B / Akt1,... Show moreThe last decade has witnessed an increased occurrence of bacterial resistance against antibiotics. The first part of this thesis describes the discovery of a novel target, protein kinase B / Akt1, that may be used to combat infection with pathogenic bacteria like Salmonella typhimurium. Inhibitors of this enzyme are currently being developed as anti-tumor agents. These molecules can now also be seen as potential antibiotics. The synthesis and biological evaluation of several series of new inhibitors of this enzyme are described. This resulted in the identification of a compound with sufficient potency and selectivity to allow in vivo inhibition of Salmonella outgrowth. The second part describes the optimization of an existing antibiotic, Gramicidin S. This is a naturally occurring decapeptide that disrupts the cellular membrane of bacteria. This results in leakage of intracellular contents and bacterial death. Unfortunately, Gramicidin S is toxic for red blood cells since their membrane is also destroyed. As part of an ongoing project to reduce the toxicity against red blood cells, part of the original decapeptide is replaced by synthetic molecules. One compound showed similar activity against bacteria and reduced toxicity against red blood cells. Further research is needed to further improve this antibiotic. Show less
Endocytosis can be conceptually broken down into two stages: The formation of the nascent vesicle containing the ingested proteins and lipids, and its subsequent maturation into a degradative... Show moreEndocytosis can be conceptually broken down into two stages: The formation of the nascent vesicle containing the ingested proteins and lipids, and its subsequent maturation into a degradative compartment. During this maturation process proteins can be recycled back to the plasma membrane to prevent degradation. The vesicular membrane and the luminal contents undergo considerable remodeling to transform this compartment into a degradative one. This stops signal transduction by degrading the receptors within the vesicle and also generates antigens for presentation on MHC class II molecules in order to elicit an adaptive immune response. The engulfment of large particles and microorganisms (e.g. pathogens) is referred to as phagocytosis. The vesicle created by phagocytosis is called the phagosome. Phagosome maturation is considered to involve a complex sequence of fusion and fission events with the sub compartments of the endocytic pathway. In many ways, phagosome maturation recapitulates the progression of cargo along the endocytic pathway. In this thesis we have described molecular mechanisms that regulate the endocytic route and how pathogens explore this endocytic route to ensure survival. Show less
Many intracellular compartments, including (MHC class II-containing) lysosomes, melanosomes and phagosomes, move along microtubules in a bi-directional manner due to the alternating activities of... Show moreMany intracellular compartments, including (MHC class II-containing) lysosomes, melanosomes and phagosomes, move along microtubules in a bi-directional manner due to the alternating activities of the plus-end directed kinesin motor and the minus-end directed dynein-dynactin motor. However, it is largely unclear how these motor proteins are targeted to specific compartments. Rab GTPases recruit and/or activate several proteins involved in membrane fusion and vesicular transport. They associate with specific compartments and therefore are ideal candidates for controlling motor protein recruitment. This work shows that dynein-dynactin motor recruitment to lysosomal compartments requires activation of the GTPase Rab7 that subsequently associates with its effector protein, RILP (for Rab7-Interacting Lysosomal Protein). RILP maintains Rab7 in the vesicle-bound, activated state and transmits a signal for specific recruitment of the dynein-dynactin motor. As a consequence, lysosomes are transported towards the minus-end of microtubules. This signalling cascade thus regulates lysosomal transport. In addition, we showed that this pathway also regulates transport of several other lysosomal compartments, including Salmonella-containing vacuoles and melanosomes. Show less
