The research described in this thesis focused on the use of bioorthogonal antigens to investigate immunological processes in antigen presenting cells. Bioorthogonal antigens are antigenic proteins... Show moreThe research described in this thesis focused on the use of bioorthogonal antigens to investigate immunological processes in antigen presenting cells. Bioorthogonal antigens are antigenic proteins produced through recombinant expression in a methionine auxotrophic E. coli strain. This allows for the replacement of methionine residues with the bioorthogonal non-canonical amino acid, azidohomoalanine (Aha), that resembles methionine. Aha contains an azide group that enables the selective and rapid visualization or enrichment of the antigen after a biological experiment using alkyne-modified fluorophores or alkyne-containing resins, respectively, via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The research involved studying the effects of post-translational modifications (PTMs), antigen complexation and glycosylation of antibodies in immune complexes on the uptake, proteolysis, and T cell activation by dendritic cells (DCs) of Aha-containing antigens. Additionally, a new method was developed to enrich low abundant bioorthogonal antigenic fragments from complex mixtures. This method can be used in future studies to identify processed Aha-containing fragments from immune cells that are preserved for T cell presentation. Show less
Chronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues,... Show moreChronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues, also coined metaflammation. In this context, white adipose tissue and liver-resident innate and adaptive immune cells produce proinflammatory cytokines that exacerbate inflammation and inhibit canonical insulin signaling. Among them, macrophages and dendritic cells were shown to play central roles in metaflammation, although the environmental and cellular changes dictating proinflammatory activation in the context of obesity are not fully understood. This thesis describes novel mechanisms by which macrophages and dendritic cells control metabolic homeostasis in obese mice. In addition, we show that immunomodulatory molecules derived from parasitic worm eggs promote an immune response in metabolic tissues that maintains insulin sensitivity. Finally, we describe the pleiotropic beneficial effects of a novel plant-derived nutritional supplement on metaflammation and metabolic homeostasis in obese mice. Altogether, this work may provide new leads for interventions aimed at improving immunological control of metabolic dysfunctions. Show less
Transplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation... Show moreTransplantation is the golden standard for the treatment of end-stage renal disease. During this process, the transplanted organ is often damaged. In this thesis, we investigated whether activation of the complement system, part of our innate immune system, plays a local role. We reviewed that properdin, the only known positive regulator of the complement system, was detected in serum, plasma and urine from patients with various complement-mediated renal diseases. In protocol biopsies obtained 10 days after transplantation, properdin was found deposited in addition to complement activation markers. Next, we showed that dendritic cells secrete properdin and a decrease in properdin levels during dendritic cell- T-cell interaction resulted in reduced T-cell proliferation and activation. We also showed that properdin is able to bind to surfaces of both viable and dead cells, contributing to complement activation. Macrophages can also produce properdin and negative regulators factor H and its splice variant FHL-1. Increasing knowledge on complement factor production by other cells than hepatocytes, including immune cells, hints towards a local role of the complement system in various processes. These findings contribute to a better understanding of the local role of the complement system and are important for the applications of (new) complement-inhibiting drugs. Show less
Dendritic cells are the canonical professional antigen-presenting cell and are therefore crucial in the generation of efficient adaptive T cell responses. It is now well described that immune cells... Show moreDendritic cells are the canonical professional antigen-presenting cell and are therefore crucial in the generation of efficient adaptive T cell responses. It is now well described that immune cells – including dendritic cells – make drastic changes to their biology to transition between different life stages and to deal efficiently with the threat of infection. However, an unanswered question was if DCs with different T cell polarizing properties - that is to say they preferentially skew T cells towards a specific specialization (for example T helper 1 cells over T helper 2 cells) - rely on distinct metabolic characteristics for their T cell polarizing ability. This thesis tries to address that question by studying the metabolism of dendritic cells after in vitro stimulation with antigens or immunomodulatory compounds that are known to prime either T helper 1 cells, T helper 2 cells, T helper 17 cells or regulatory T cells. In addition, we interrogate the role of liver kinase B1 (LKB1) and mechanistic target of rapamycin complex 1 (mTORC1) in DC biology. Show less
Type 1 Diabetes (T1D) is an auto-immune disease in which beta cells in the pancreas are killed by auto-reactive T-cells. Auto-reactive T-cells are activated by dendritic cells that present antigens... Show moreType 1 Diabetes (T1D) is an auto-immune disease in which beta cells in the pancreas are killed by auto-reactive T-cells. Auto-reactive T-cells are activated by dendritic cells that present antigens. Immunotherapy could reverse T1D, however. A case report of a T1D patient showed that after intravenous immunoglobulin treatment her insulin needs dropped completely. Similarly, the majority of T1D patients were insulin independent after autologous hematopoietic stem cell transplantation. As these therapies only showed incidental success or are a drastic reset of the immune system, respectively, other milder therapies were studied as well. Autologous tolerogenic dendritic cell therapy, for instance, is a reproducible, stable therapy and does not differ between T1D patients and healthy subjects. In addition, the author described that when mesenchymal stromal cells were activated, they were able to suppress an antigen-specific immune response, thereby potentiating them as an antigen-specific therapy besides their natural immunosuppressive nature. Activated mesenchymal stromal cells could also improve the islet of Langerhans’ microenvironment, as they secreted immunosuppressive and angiogenic factors. To conclude, the future of T1D therapies lies in finding a balance between suppressing the immune system and antigen-specific therapies combined with therapies that increase the vitality of beta cells. Show less
In the current thesis, we provide novel insights in antigen uptake, storage, processing, and sustained cross-presentation mechanisms in dendritic cells (DCs) in vitro and in vivo. We have studied... Show moreIn the current thesis, we provide novel insights in antigen uptake, storage, processing, and sustained cross-presentation mechanisms in dendritic cells (DCs) in vitro and in vivo. We have studied antigen handling functions by dendritic cells in three different antigen delivery routes: antibody targeting involving Fcγ receptors and complement factor C1q, C-type lectin receptor targeting, and toll-like receptor ligand targeting systems. Our data highlights that antigen storage in specialized compartments in DCs, despite the chosen uptake route, is beneficial for prolonged antigen cross-presentation by DCs and sustained T cell activation. Further in vivo studies in different antigen presenting cell (APC) subsets confirmed the presence of antigen storage compartments by isolating APC subsets after in vivo antigen uptake. Besides, we revealed a dominant role of C1q in antigen-antibody immune complex uptake and cross-presentation in vivo in contrast to the crucial role of Fcγ receptors in vitro. Furthermore, we demonstrated that autophagosomes have a negative impact on the storage of antigen in those specialized compartments and thereby affecting DC cross-presentation efficiency. With the current studies, we unraveled some mechanics of antigen processing in DCs which contribute to future vaccine designs against diseases such as cancer. Show less
Immunotherapy of cancer has established itself in recent years as a promising novel approach to treat cancer patients. One of the experimental approaches is based on therapeutic vaccination. We... Show moreImmunotherapy of cancer has established itself in recent years as a promising novel approach to treat cancer patients. One of the experimental approaches is based on therapeutic vaccination. We have previously developed vaccines consisting of synthetic long peptides (SLP) which successfully eradicated premalignant lesions in 50% of patients. To further improve these vaccines, a Toll-like receptor ligand (TLR-L) was conjugated to SLP which enables targeting of the SLP to relevant antigen-presenting cells while concomitantly activating these cells. In fact, the research described in this thesis shows that TLR-L SLP conjugates induce enhanced antitumor immunity. Furthermore, optimization of the TLR-L led to even furher improved antitumor responses in mice. Using human cancer patient-derived lymph node cells, we show that lymph node-derived T cells are favorably activated by the TLR-L SLP conjugates. Finally, we combine multiple innate immune stimulatory agonists (TLR2-L and NOD2-L) in one molecule to establish synergistic immune activation. Overall, the research described in this thesis demonstrates the potency of TLR-L SLP conjugates as cancer vaccines, which could strongly contribute to the treatment of cancer patients. Show less
Parasitic helminths are important organisms to study because their infections have both adverse and beneficial effects on the human host. Helminth infections are considered a burden, as these... Show moreParasitic helminths are important organisms to study because their infections have both adverse and beneficial effects on the human host. Helminth infections are considered a burden, as these infections cause significant morbidity in a large proportion worldwide. However, helminth infections, by means of their ability to modify host immune responses can also provide protection against inflammatory diseases (inflammatory bowel disease, diabetes, and asthma). It is important to better understand the underlying mechanisms of these Yin (positive) and Yang (negative) consequences of helminth infections. The general objective of this thesis is to track helminths at different levels. On the one hand to improve the detection of helminth infections, essential for the studying helminths and the interaction with their human host. Moreover, a more sensitive diagnostics is instrumental for monitoring the distribution of helminth infections and to evaluate the helminth infections elimination program. On the other hand, to understand the mechanistic insights of the interplay between helminths and the host immune system results in priming of Th2 and regulatory T cell responses. This could contribute to the identification of targeted pathways to manipulate immune responses, as part of developing therapeutics to treat inflammatory disorders characterized by deregulated Th2 and/or Treg responses. Show less
In this thesis, we have addressed aspects of two main arms of the adaptive immune system; the B cell and antibody arm and the T cell arm. This led to a division in the presentation of the... Show more In this thesis, we have addressed aspects of two main arms of the adaptive immune system; the B cell and antibody arm and the T cell arm. This led to a division in the presentation of the results described in this thesis into two sections. In the first section, we present the results regarding the characterization of ACPA responses, B cells and ACPA secreting plasmablasts/-cells in RA as well as autoantibody responses and their regulation by an effective anti-rheumatic drug, abatacept, in the arthritis mouse model; Collagen Induced Arthritis (CIA). The second section is compiled of results obtained from studies examining the regulatory and other aspects of CD49b+CD4+ T cells on proinflammatory responses involved in the pathogenesis of arthritis. Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by inflammation of the synovial membrane of the joints, culminating in destruction of cartilage and deformity of the joints if remains untreated. Infiltration of inflammatory immune cells such as B cells and T cells into the inflamed joints is a characteristic feature of RA. These immune cells are in continuous interaction with each other and create a viscous circle that sustains persistent synovitis and damage to articular cartilage. Show less
Synthetic long peptides (SLPs) derived from cancer antigens hold great promise as well-defined antigens for immunotherapy of cancer. However, the formulation of SLPs for in vivo administration... Show moreSynthetic long peptides (SLPs) derived from cancer antigens hold great promise as well-defined antigens for immunotherapy of cancer. However, the formulation of SLPs for in vivo administration still needs to be improved. So far, SLPs have been formulated in Montanide-based water-in-oil emulsions in (pre-)clinical trials. However, the use of Montanide as an adjuvant has some important limitations, such as: non-biodegradability; significant local side effects; poor control of release rate; lack of specific dentritic cell (DC)-activating capacity; and the presence of organic solvents (needed to dissolve the peptides prior to mixing with the adjuvant) in the final formulation. Therefore, alternative formulations containing an effective delivery system for peptide-based cancer vaccines are highly needed. Among the numerous vaccine delivery systems, poly(lactic-co-glycolic acid) (PLGA) biodegradable particulate delivery systems are particularly interesting because they are biocompatible; can protect soluble antigens from degradation and rapid clearance once administered; allow for co-encapsulation of (multiple) antigens and adjuvants; and mimic the size and structure of a pathogen, being more efficiently taken up by DCs than soluble antigen. This thesis describes fundamental studies on the design and applicability in a preclinical setting of PLGA-based particulate formulations for the delivery of SLP-based cancer vaccines. Show less
Nearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T... Show moreNearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T helper 2 (Th2) cells. In addition to their involvement in anti-helminth immunity, recent studies have shown that components of the type 2 immune responses can have additional functions. For example, recent evidence indicates that multiple facets of the type 2 immune response can regulate tissue-specific metabolic processes and whole-body nutrient homeostasis, and protect against insulin resistance. In this work we use omega-1, a glycosylated RNase excreted from Schistsoma mansoni eggs with strong Th2-inducing capacities, to study the requirements that equip DCs for Th2 skewing. In addition, we analyse the effect of chronic S. mansoni infection and administration of S. mansoni-derived egg antigens on metabolic homeostasis in diet-induced obese mice. Elucidating how helminths generate Th2 responses and contribute to metabolic homeostasis will not only shed light on the mechanisms that promote control of parasite infection, but may provide valuable leads for the development of pharmaceutical agents for the treatment of metabolic disorders. Show less
Atherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process... Show moreAtherosclerosis is one of the primary causes of cardiovascular disease; the number one cause of death in the western society. Atherosclerotic plaque formation is a dynamic multi-cellular process where regulation of different genes essentially determines the activity of the different cell types involved. Gene expression is regulated, amongst others, by epigenetic processes. Epigenetic mechanisms change the accessibility of the DNA sequence and is thought to form a link between environmental factors and gene expression. Epigenetics may therefor play an important role in atherosclerosis pathology. The research described in this thesis evaluated the role of epigenetic regulation on various aspects of atherosclerosis pathology. It was found that the epigenetic H3K27Me3-mark was reduced in later stages of the disease. Monocytes differentiating into dendritic cells and macrophages (an important process in atherosclerosis pathology) showed higher transcription of the epigenetic regulatory gene KMT1c. Specifically blocking this gene resulted in reduction of DC-SIGN (a dendritic cell specific molecule) expression. By specifically blocking other epigenetic proteins, CCR5 (a molecule important to monocyte migration) was re-expressed on cells which did not express CCR5. This shows that epigenetic regulation is an important process in atherosclerosis pathology and might prove to be novel pharmacological target for treatment of atherosclerosis. Show less
Type 1 diabetes is a T-cell mediated autoimmune disease in which the insulin producing cells in the islets of Langerhans are destroyed. No cure exists yet, but multiple types of immune suppressive... Show moreType 1 diabetes is a T-cell mediated autoimmune disease in which the insulin producing cells in the islets of Langerhans are destroyed. No cure exists yet, but multiple types of immune suppressive regimens are explored. In this thesis I studied the opportunities to dampen autoimmunity in type 1 diabetes, with the focus on the possibility of using tolerogenic dendritic cells loaded with islet antigens as cell therapy in patients with type 1 diabetes. Tolerogenic DCs appear suitable candidates to modulate T-cell response at different levels and are able to induce antigen specific regulatory T-cells, utilizing various mechanisms to suppress pro-inflammatory responses. Hence, the chance for successful control of autoimmunity in patients treated with tolerogenic DC therapy may be increased compared to monotherapy. Tolerogenic DCs as cell therapy have the potential to modulate the immune system. Although replacement or enhancement of insulin producing beta-cells is warranted, focusing on diminishing the causal pathology, the immune attack on the islets of Langerhans, could be a preferential option, as it is still difficult to challenge existing autoimmunity with the current arsenal of immunosuppressive drugs. This tissue-specific intervention cell therapy might offer new opportunities for the treatment of type 1 diabetes. Show less
In this thesis we describe our studies aimed at optimizing the efficacy of synthetic long peptide (SLP) vaccines via the encapsulation in Poly-(lactic-co-glycolic acid) (PLGA)particles.... Show moreIn this thesis we describe our studies aimed at optimizing the efficacy of synthetic long peptide (SLP) vaccines via the encapsulation in Poly-(lactic-co-glycolic acid) (PLGA)particles. Immunotherapy based on SLP-vaccines has resulted in strong tumor specific immune response and importantly, improved clinical benefit in patients with pre-malignant lesions. One important drawback associated with SLP-vaccines is their current form of administration in Montanide, a clinical grade water-in-oil emulsion. The aim of this Ph.D project was to device an alternative method of delivery which overcomes the drawbacks associated with the use of Montanide. For this purpose we explored the use of PLGA (nano)particles (NP) as a delivery vehicle for SLP. Several important aspects for vaccination were assessed in this thesis; from the pharmaceutical formulation to the immunological characterization of different PLGA-SLP preparations. Together, the data presented in this thesis show that PLGA-NP mediated delivery of SLP is a very efficient method to target, load and mature Dendritic cells (DCs) as immune stimulatory compounds can be co-encapsulated with the vaccine Ag Show less
Dendritic cells (DCs) are antigen-presenting cells (APCs) which play a key role in the regulation of immune responses. DCs are often referred to as __professional__ APCs, since their primary... Show moreDendritic cells (DCs) are antigen-presenting cells (APCs) which play a key role in the regulation of immune responses. DCs are often referred to as __professional__ APCs, since their primary function is to present antigens from pathogens or malignant cells. Consequently, there is a great deal of interest in how DCs might be exploited as a form of immunotherapy e.g. to induce immunity to cancers. However, DCs are also thought to play an important role in directing regulatory immune responses to innocuous antigens, which are targeted in autoimmune disease or during transplantation. Soluble factors secreted by DCs are crucial mediators in determining this balance between the immunogenic and regulatory arms of the immune system. One such group of factors is cytokines and one family which is gaining increasing attention is the IL-12 family. It is composed of four members; two are immunogenic and their expression has been very well characterised in DCs. The other two are regulatory, but relatively little is known about their regulation and expression in DC populations. In this thesis we aim to give a comprehensive overview of the expression and regulation of IL-12 family members in human DCs, with a particularly emphasis on IL-12, IL-27 and IL-35. Show less
This thesis aimed to provide insight into the role of microbiota-host interactions in the regulation of mucosal and systemic immunity in the context of IBD. Regulation of microbiota composition (e... Show moreThis thesis aimed to provide insight into the role of microbiota-host interactions in the regulation of mucosal and systemic immunity in the context of IBD. Regulation of microbiota composition (e.g. by probiotics and prebiotics) offers the possibility to modulate immune responses and contribute to the prevention and treatment of (autoimmune) - diseases. By evaluating immune modulation capacities of probiotics with genome-wide gene expression profiling in both in vivo and in vitro models, novel mechanisms were identified in which probiotic bacteria modulate immune responses under conditions of homeostasis and inflammation. These new insights will allow more rational selection and validation of probiotic usage in a variety of clinical conditions Show less
The aim of thesis was to increase our insight into the pathological mechanisms behind Langerhans cell histiocytosis (LCH) by studying different aspects of healthy dendritic cells (DC), LCH cells,... Show moreThe aim of thesis was to increase our insight into the pathological mechanisms behind Langerhans cell histiocytosis (LCH) by studying different aspects of healthy dendritic cells (DC), LCH cells, and a mouse model of histiocytosis. Furthermore, we initiated a study to evaluate a human monoclonal antibody directed against the cell surface protein CD1a in order to find a rational therapy for LCH. Chapter 3 describes a role for transcriptionally active beta-catenin in the differentiation and maturation of monocyte-derived DC, which are a putative precursor for LCH cells. The absence of this form of beta-catenin in LCH cells might be an important factor responsible for the immature phenotype of these pathological cells. In Chapter 4 a mouse model of malignant histiocytosis (MHSV) is re-evaluated. The conclusion is that the MHSV model represents a heterogeneous neoplastic disease with characteristics of macrophage/DC sarcomas. LCH cells express the CD1a antigen. In Chapter 5, the evaluation of a completely human anti-human anti-CD1a monoclonal antibody CR2113 is described. This antibody has cytotoxic potency on CD1a expressing cells and should, therefore, be further investigated in a pre-clinical setting for its usefulness as a therapeutic agent for LCH. Chapter 6 describes significant telomere length shortening in LCH cells suggesting that a possible intrinsic and fundamental alteration, similar to neoplastic disorders, might play a role in the etiology and/or pathogenesis of LCH. Show less
Major advancements in the understanding of the immune system have provided us with the opportunity for rational design of therapeutic immunological interventions. The notion that dendritic cells ... Show moreMajor advancements in the understanding of the immune system have provided us with the opportunity for rational design of therapeutic immunological interventions. The notion that dendritic cells (DC) play a crucial role in the activation of T lymphocytes has made DC biology of central importance for vaccine development. Accordingly, efficient delivery of antigen to DCs is one of main objectives in vaccine development. In this thesis, antibody-mediated antigen targeting is evaluated as a potential antigen delivery strategy for therapeutic vaccination. Complexes of protein antigen and antigen-specific antibodies are natural formulations that bind to Fc__ receptors. Fc__R ligation on DCs leads to efficient uptake, DC maturation and presentation of the antigen to T lymphocytes. Interaction of Ag-Ab complexes with Fc__Rs on DCs provides a link between the humoral and cellular arms of the immune response. This thesis contains an extensive evaluation of Fc__R-mediated antigen delivery to dendritic cells in the context of T lymphocyte-mediated immunotherapy. In addition, it contains a detailed analysis of Fc__R function on DCs and addresses the kinetics of cross-presentation of antigen after Fc__R-mediated uptake. Show less
Parasitic worms of the genus, Schistosoma, infect millions of people mainly in the tropics and can cause serious morbidity. Human schistosoma infection is often associated with strong T helper 2... Show moreParasitic worms of the genus, Schistosoma, infect millions of people mainly in the tropics and can cause serious morbidity. Human schistosoma infection is often associated with strong T helper 2 polarized immune responses as well as immunehyporesponsiveness. Dendritic cells play a central role in sensing of pathogens and generation of appropriate immune responses against these pathogens. This thesis describes that human schistosoma infection suppresses phenotype and T cell polarizing capacity of dendritic cells present in blood of these subjects. Furthermore, in vitro studies identified molecular markers in dendritic cells that can be used to predict whether these cells will induce T helper 1 or 2 responses following exposure to Th1-polarizing bacterial extracts or Th2- skewing lipids derived from schistosoma worms. Finally, the identification of the major Th2-polarizing component secreted by schistosoma eggs and the molecular mechanisms through which this factor instructs dendritic cells to drive this response is described. Taken together, these studies provide new insights in the molecular interplay between dendritic cells and schistosomes and as such in the cellular and molecular mechanisms behind shaping of T helper 2 immune responses and/or immunehyporesponsiveness observed during these parasitic worm infections. Show less
Atherosclerosis is a chronic inflammatory disease of the vasculature in which both a disturbed lipid metabolism and inflammatory immune responses against several self-antigens are involved. In this... Show moreAtherosclerosis is a chronic inflammatory disease of the vasculature in which both a disturbed lipid metabolism and inflammatory immune responses against several self-antigens are involved. In this thesis we have explored the effectiveness of DC-immunotherapy in atherosclerosis. We have used different strategies to target the immune component in different stages of atherosclerosis. First we used DCs as a vaccination strategy to induce a protective antibody response trough the injection of oxLDL-pulsed DCs or to target NKT cells by the injection of OCH-pulsed DCs. Next we assessed the potential of DC-immunotherapy in a model of established atherosclerosis. We also evaluated the effects of a disturbed TGF-_ signaling in DCs and the subsequent effects on atherosclerosis by using ApoE-/- which have a dysfunctional TGF-__ Receptor II under the CD11c promoter. Next, we were interested in the effect of foam-cell formation on the antigen-presenting capacity of DCs and macrophages. Therefore we studied the effect of oxLDL-loading on antigen uptake and antigen presentation by DCs and macrophages. Finally, by depleting or inducing Tregs we investigated the potential role of regulatory T cells in a mouse model for aneurysm formation. Show less
