Julita Gil Cuesta

• 21 December 2020
• Time: 4 PM - 6 PM.
• Online defence
• Supervisors: Em.Prof. R. Colebunders, dr. F. Vogt and dr. R. Van den Bergh

Abstract

Humanitarian crises are unforeseen events causing damage, destruction and human suffering, which overwhelm local capacity. With increasing health crises and interventions growing in magnitude and complexity, strong scientific evidence to guide interventions is crucial. However, the quality of the evidence in humanitarian interventions is often weak. This thesis aims to demonstrate how knowledge can be generated efficiently and applied in different types of humanitarian crises such as measles epidemics, and during a natural disaster in the Philippines.

We demonstrated the added value of household coverage surveys after a measles mass vaccination campaign in Democratic Republic of Congo, compared to administrative coverage surveys. Certain groups of children were never reached by campaigns, while others were repeatedly vaccinated. Improving community engagement by investing sufficient time in less accessible areas and assessing reasons for non-vaccination through qualitative studies is key.

Following a measles mass vaccination campaign in Guinea, we explored the reasons behind the decision to vaccinate or not, by interviewing caregivers and health staff organising the campaign. Caregivers suggested that community engagement can improve vaccination campaigns, specifically through the pivotal role of community health workers, local recruitment of staff, development of their communication skills, attitudes, and knowledge to provide adequate information about vaccination.

Studies conducted after typhoon Haiyan in the Philippines allowed us to determine the disaster impact on hospitalisations and health care workers. We documented a drop in hospital admissions, while gastroenteritis and respiratory admissions increased after Haiyan. Mobile clinics most frequently diagnosed acute respiratory infections, hence their appropriate management should be ensured in future typhoons. Health staff were forced to prioritise between their personal and professional life. Health staff’ performance was affected by accessibility to the hospital, personal and family safety and faith. Improving communication, accessibility through housing health staff and relatives close to the hospital and considering faith and religious practices could improve health staff protection and performance in similar responses.

Three cross-cutting concepts were distilled in this thesis: improving estimates during crises and response can be achieved by integrating pre-existing and crisis-induced data, including pre/post analyses and combining facility-level and community-level data. Second, investigating the experiences of care-givers and health workers through qualitative studies is important for an in-depth understanding of crises and responses. Third, community engagement can improve the knowledge by informing communities, consulting them and involving them. Additional efforts to bridge the gap between generating and using the knowledge during humanitarian crises are needed.

Nolan Herssens

• 16 December 2020
• Time: 5 PM - 7 PM.
• Online defence
• Supervisors: Prof. A. Hallemans, prof. W. Saeys and prof. V. Van Rompaey

Abstract

Walking during daily life requires the ability to appropriately cope with unexpected disturbances. To do so, the different sensory systems (i.e., visual, somatosensory, vestibular system) play an important role. The complex arrangement of sensory systems is crucial in adequately achieving, maintaining, and restoring stability during walking. However, with increasing age a decline of these sensory functions is apparent, influencing stability and potentially increasing the risk of falling. Losing one, or multiple, sensory information sources can be very debilitating. Especially loss of vestibular function can be highly disabling as the vestibular system is both an important sensory and motor system in the control of balance during walking.

The first part of this dissertation aimed to increase our understanding of how walking and stability during walking is adapted with healthy ageing. First, gaps in the current state of the art were identified through a detailed analysis of the literature. This was followed by an instrumented gait analysis in healthy adults between the ages of 20 to 89. Results showed that older people walk slower and take shorter steps to increase their stability. Additionally, an increased variability in foot placement was noted. As a result, older adults have a reduced ability to react to disturbances during walking and will thus be more prone to falls, which should be mitigated during gait rehabilitation training.

The second aim of this dissertation was to gain insights on the influence of a loss of vestibular function on stability during standing and gait. By investigating patients with bilateral vestibulopathy (BVP), strategies to adapt to a reduced balance control were explored. Results indicated that in conditions where adequate visual and somatosensory information is present, patients with BVP can perform on the same level as healthy subjects. However, the underlying balance control strategies used to maintain stability during these conditions may differ. Additionally, an attempt was made to identify discriminative factors between patients with BVP who fell and those who did not. Current evidence illustrated that, although both patients with a history of falls and those without present with an increased risk of falling, we were unable to pinpoint any discriminating factors. Thus, our current understanding of balance performances and gait adaptations in patients with BVP stresses the need to improve assessment protocols to identify the specific balance deficits present in patients with BVP. This would improve the identification of those patients with an increased risk of falling.

Matthias Beyens

• 8 December 2020
• Time: 5 PM - 7 PM.
• Online defence
• Supervisors: prof. M. Peeters and prof. G. Van Camp
  

Abstract

The general aim of this thesis was to further elucidate the genetic drivers in the oncogenesis of pancreatic neuroendocrine tumors and to unravel the molecular mechanisms that confer everolimus resistance in this cancer. To study this aim, we used multiple approaches to unravel the molecular architecture in this cancer type, including next-generation sequencing methods, drug-treatment cell proliferation assays and bioinformatic algorithms.

The genetic basis of pancreatic neuroendocrine tumors has been an evolving field in the last decade. Here, we wanted to investigate the contribution of known pancreatic neuroendocrine oncogenesis driving genes in clinical samples and evaluate whether tumor heterogeneity exists in pancreatic neuroendocrine tumors using a targeted resequencing technique.

Everolimus resistance in pancreatic neuroendocrine tumors is a major limitation on the treatment efficacy of this therapeutic. The aim here was to unravel the underlying mechanism that confer resistance and identify novel therapeutic targets in in vitro models using proliferation assays and next-generation sequencing techniques.

Through the investigation of the oncogenesis of pancreatic neuroendocrine tumors by means of genetic and other molecular techniques in clinical samples and everolimus-resistant cell lines, we aimed to increase the overall knowledge of this cancer type, unravel the important signaling pathways (and players) and unveil clinically relevant therapeutic targets for overcoming everolimus resistance.

​Michel Mandro​

• 2 December 2020
• ​Time: 4:00 PM - 6:00 p.m.
  
• Online defence
• ​Supervisors: Em. Prof. R. Colebunders, dr A. Kuesel and dr. P. Suykerbuyk
  

Abstract

Onchocerciasis is caused by the parasitic worm Onchocerca volvulus, which is transmitted through repeated bites by infected blackflies of the genus Simulium. High prevalence and a wide spectrum of seizure disorders including nodding syndrome, now described as onchocerciasis-associated epilepsy (OAE) have been reported in many onchocerciasis endemic areas in sub-Saharan Africa. OAE is defined as at least two seizures without an obvious other cause, that start in children 3-18 years old in previously healthy children. The potential link between onchocerciasis and epilepsy had previously been suspected. However, the notion that onchocerciasis is able to induce epilepsy was not universally accepted. With this thesis, we aimed to improve our understanding of the association between onchocerciasis and epilepsy.

In a state-of-the-art house to house epilepsy survey in Draju and Kanga in the Logo Health zone in Ituri province, DRC, the epilepsy prevalence was found to be 4.6%, in an area where ivermectin was never distributed. In a case-control study, we confirmed that onchocerciasis is a risk factor for epilepsy, with cases twice more often found to present microfilariae in skin snips and O. volvulus antibodies compared to controls. Moreover among those with positive skin snips, the microfilarial density was ten times higher in cases compared to controls.

In a proof-of-concept randomized clinical trial, we carried out a four-month follow up which was evaluating the added value of ivermectin treatment in persons with OAE treated with anti-epileptic drugs. The results were inconclusive possibly because of the small size of the study. However, in a second randomized trial, with a one year follow up, comparing the added value of twice and thrice annual ivermectin treatment over annual ivermectin in O. volvulus infected PWE treated with phenobarbital, a beneficial effect of multiple-dose ivermectin in reducing the frequency of seizures was demonstrated.

In conclusion, our studies provide evidence that OAE exists in DRC. Moreover, our findings contribute to the growing evidence that an O. volvulus infection is able to cause epilepsy and that ivermectin treatment has an effect in reducing seizures.

​Stef Feijen​

• 1 December 2020
  
• ​Time: 3:30 PM - 5:30 p.m.
  
• Online defence
• Supervisor: Prof. F. Struyf
  
  

Abstract

Shoulder pain is common across the lifespan of the competitive swimmer, often resulting in athletes leaving the sport or being severely restricted in performance. Yet despite the establishment of a high incidence, uncertainty remains regarding the cause of the swimmer’s shoulder pain and there is still significant debate over the factors that contribute to its development. Even more so, epidemiological data going all the way back to the 1980’s does not appear to show any reduction in shoulder injury burden.
The lack of knowledge regarding its etiology and the clinical heterogeneity of the swimmers’ shoulder has reduced the ability to define and devise successful interventions. Knowledge of its risk factors, however, may offer guidance in the development of such strategies but this requires a prospective evaluation of the characteristics that may potentially contribute to shoulder pain. Consequently, the main objective of our research was to identify predictors of swimmers’ shoulder and develop and validate a multivariable prognostic model for the prediction of shoulder pain in swimmers.

To complete this investigation, five concomitant studies were undertaken. The first two studies aimed to evaluate the evidence in the literature for factors associated with the swimmer’s shoulder pain. Based on the findings we selected clinically relevant variables that were well-documented in the literature for inclusion in our prospective research protocol. The third and fourth study aimed to examine the reliability of the measurements for thoracic rotation range of motion and latissimus dorsi muscle flexibility that had yet to be established in a setting appropriate to the swimmer. These studies formed the platform for our main investigation, a longitudinal prospective research for the purposes of identifying predictors of shoulder pain.
Our approach was to recruit 200 competitive swimmers between the ages of 10 and 40 years who trained for an average of at least four hours per week. We recruited swimmers in collaboration with the Flemish Swimming Federation. Swimmers who met the predefined criteria were considered eligible for inclusion in our prospective cohort study, and also recruited for the assessment of measurement reliability. The subjects had a comprehensive physical exam completed by the main investigator to measure demographic, psychosocial, musculoskeletal, training-related and biomechanical characteristics of interest at baseline and again after 6, 12, 18 and 24 months. Swimming volume was prospectively recorded by the swimming coach during the season. Further, a protocol for the measurement of thoracic spine rotation range of motion and latissimus dorsi muscle flexibility using a bubble-filled inclinometer was tested for reliability during baseline assessment.

Excellent intra-rater reliability was found for both measurements conducted on young competitive swimmers (ICC thoracic rotation test 0.91-0.96; ICC latissimus dorsi test 0.91-0.94). Further, our prospective investigation confirmed a significant relationship between shoulder pain and regional level competitive swimming (OR 0.19, 95% CI 0.058-0.629); acute to chronic workload ratio (OR 4.89, 95% CI 1.00-18.54); posterior shoulder muscle endurance (OR .96, 95% CI 0.92-0.99) and hand entry position error (OR .37, 95% CI 0.155-0.906).
Based on the results of our series of investigations we advise against large increases in swim-training volume, especially between successive training levels from the young to the adolescent competitive swimmer. We recommend year-round monitoring of both the swimmer’s internal and external training load as well as implemented regular stroke assessment. Furthermore, dry-land exercises focusing on the endurance capacity of the posterior shoulder muscles appear warranted.
Our prediction model showed good discriminative ability between swimmers at higher risk of shoulder pain and those who are not. It consists of parameters that can easily be measured in a swimming setting and that can aid in informing and facilitate counselling of swimmers at risk. We recommend external validation of our model prior to the development of clinical reasoning and treatment programs.

​Maud De Venter​

• 27 November 2020 
• Time: 4:00 p.m. - 6:00 p.m.
  
• Online defence
  
• Supervisors: Prof F. Van Den Eede and Em. Prof. B. Sabbe

Abstract

The main aim of this doctoral dissertation was to expand our knowledge on the clinical effects of childhood trauma on affective disorders and functional somatic syndromes, based on research questions relevant for science, clinical practice and society in general.

This thesis contains longitudinal research on the long-term impact of childhood trauma. We also focused on possible differential effects of trauma subtypes. In addition, childhood trauma and its association with other, not yet investigated clinical and social outcomes in (specific types of) affective disorders and functional somatic syndromes is a third important domain of research in this dissertation.

More specifically, we elaborated upon the role of childhood trauma on depression 12 and 24 weeks after childbirth and on the course of panic disorder later in life. We also focused on the associations between childhood trauma and work functioning. In addition, we examined the differential effects of childhood trauma subtypes on fatigue and physical functioning in individuals suffering from CFS, as well as the effect of childhood trauma on the response to group cognitive-behavioural therapy (GCBT) at the end of treatment and after one year on fatigue and physical functioning in adults coping with CFS.

The relationships between childhood trauma and affective disorders and functional somatic syndromes are very complex and lack consistency. Although childhood trauma is a well-documented factor in the etiopathogenesis of affective disorders, it does not necessarily mean that its course is equally vulnerable to its impact. Other clinical features appear to be more reliable predictors to consider. We want to emphasize the importance to respect the specificity of the childhood trauma subtypes, as well as the uniqueness of the different possible clinical outcomes in studying their relationship. Affective disorders should not be lumped together when looking at their long-term association with childhood trauma. Also, there are a lot of mediating and moderating factors influencing these associations, which complicates the drawing of general conclusions on this matter.

Frederik Verelst​

• 9 November 2020
  
• Supervisors: Prof. P. Beutels and dr L. Willem 
• Language: English

Abstract

Epidemiological and economic models are used to simulate the impact of interventions on the spread of infectious diseases. Since behavior is an important factor in this, behavioral change models have been developed. Often, it is assumed that a rational individual will exhibit “free-rider” behavior: relying on herd immunity, they will increasingly refuse vaccination as vaccination coverage increases. This hypothesis originates in game theory.

A systematic review of 178 papers showed an increasing trend in published behavioral change models. However, only 15% of these used observed data for parameterization or validation.

This is why we studied the relative importance of six vaccine-specific attributes relevant to decisions about vaccination. We conducted a discrete choice-experiment in Flanders, Belgium, South-Africa, France, the Netherlands and the UK. Effectiveness and accessibility of the vaccine were found to be most important. Contrary to what game-theoretical models assume, social norms dominated free-rider behavior.

Using these results, we simulated the dynamic coverage of vaccination against measles in Flanders – parallel to a dynamic transmission model. We examined the impact of different scenarios regarding behavior on vaccine utility, vaccine coverage and disease dynamics. Exogeneous shocks, such as a “vaccine scare” or suspension of the vaccination program, caused repeated outbreaks.

In the context of an economic analysis on workplace vaccination, we simulated the spread of influenza in Belgium, using a compartmental transmission model. We accounted for both age-specific social contact behavior and reduced contact behavior of symptomatic individuals. Workplace vaccination – funded by the employer – was usually cost-saving, and, furthermore, reduced the burden of disease of influenza, both in the workplace and in the general population.

Vaccine-induced herd immunity should thus be regarded as something positive. Indeed, we did not observe free-rider behavior in any of the study-populations. On the contrary, social norms increased the perceived value of vaccines. Communication should thus emphasize that vaccination is still the norm. Another important factor in vaccination decisions was accessibility. Regarding the latter, there is still much room for improvement for vaccines that target the adult population. In particular, workplace vaccination against influenza can be an alternative to time-consuming visits to both the doctor’s office and the pharmacy.

Finally, given the non-linear relationship between the uptake of prevention measures and disease dynamics, epidemiological and economic models should take behavior change into account. However, to develop behavior change models that are not purely theoretical – as indeed purely game-theoretical models are outdated - more data collection is necessary.

​

Stany Perkisas

• 29 October 2020
• Location: UAntwerp, Stadscampus, Promotiezaal and online
• Supervisors: Em. Prof. M. Vandewoude and Prof. V. Verhoeven
• Language: English​​

Abstract 

​

Elise Braekman

• 23 October 2020
• Supervisor: Prof. G. Van Hal
• ​Language: English​

Abstract

In this dissertation, the effect of online data collection was assessed in the context of the Belgian health interview survey. The following aspects were, amongst others, evaluated:

• What is the effect of using different modes of data collection on the estimates of health indicators?
• What is the effect of applying different modes of data collection on the unit and item response rates?
• What is the difference in costs between different modes of data collection?

This was done by organizing three studies (one in a convenience sample, the others in a random sample drawn from the general population).

By means of this PhD project, the existing knowledge on the use of web and mixed-mode data collection in the framework of health interview surveys expanded. Moreover, the dissertation includes some general recommendations in order to meet the current challenges associated with the organization of health interview surveys.

Stijn Van Hees​

• 22 October 2020
  
• Supervisors: Prof. T. Vanwolleghem, Prof. S. Francque and Prof. K. Laukens
• ​Language: English​
  

Abstract

In a first part of this thesis, we evaluated the consequences of treatment cessation in a subpopulation of chronic hepatitis B patients after long-term medication-induced viral suppression. The first study of this part focused on viral rebound and clinical outcomes of patients who stopped treatment before they achieved functional cure. We found clinically significant viral rebound rates in two-thirds of the patients 6 years after treatment cessation. Additionally, two liver-related deaths were reported among the patients who stopped treatment.  In a second study of part 1 we investigated functional cure rates in patients who stopped treatment. Importantly, we found that all patients with functional cure after treatment cessation showed a sustained suppression of the virus after treatment cessation. These data thus suggest a predominant non-cytolytic clearance of the Hepatitis B Virus.  In a third chapter of part 1 we compared functional cure rates in patients who stopped treatment versus patients who continued treatment. We found Caucasian ethnicity, but not treatment cessation, to be associated with functional cure.

The data presented in the first three chapters of this thesis favor treatment continuation until functional cure is achieved. At the beginning of this PhD the durability of functional cure had, however, not been well investigated. Therefore, in the fourth study of the first part, we investigated the durability of functional cure. We did not observe any clinically significant relapses, indicating that functional cure is a good endpoint.

The long-term outcome of a chronic hepatitis B (CHB) infection largely depends on the clinical phenotype, but little is known on the underlying immunological mechanisms. Therefore, in part 2 of this thesis, we studied B cells during the natural history of a Chronic Hepatitis infection. B cell transcriptomes associated with the clinical phenotype of a CHB infection. In addition, we highlight important differences between peripheral and intrahepatic B cells.

In part 3 of this thesis we focused on Hepatocellular Carcinoma, a common long-term complication of Chronic Hepatitis infections. We first give an overview on circulating diagnostic and predictive biomarkers for Hepatitis B-associated Hepatocellular Carcinoma and then describe the challenges associated with the initiation of a Hepatocellular Carcinoma surveillance program in Uganda.

Jonas Van Audenaerde​

• 21 October 2020
  
• Supervisors: Prof. E. Smits, Prof. M. Peeters and dr G. Roeyen
• Language: English

Abstract

Pancreatic Ductal Adenocarcinoma (PDAC) has the worst 5-year survival of all cancers nowadays and is projected to become the 2^nd leading cause of cancer-related death by the end of this decade. Despite hopeful breakthroughs in new treatment options for other cancer types, no improvement has been made for pancreatic cancer patients. The unique tumour microenvironment (TME) of PDAC is held responsible for the great amount of therapy resistance towards current and novel treatment schemes. More specifically, a profound desmoplastic reaction, orchestrated by activated pancreatic stellate cells (PSC), causes shielding of the tumour and an extremely high intra-tumoural pressure. This leads to a virtually impenetrable tumour resulting in this dismal prognosis for PDAC patients. Therefore, new treatment options targeting not only the tumour but also this particular TME are urgently needed. Hence, this thesis focusses on the development of new combination strategies to address the highly unmet medical need.

Recently, immunotherapy has booked unseen successes in the treatment of patients with malignant melanoma, non-small-cell lung cancer and kidney cancer. More specifically, activating T cells by using so-called immune checkpoint inhibitors like PD-(L)1 and CTLA-4 unlocked an unseen potential for treatment of cancer. The Nobel Prize 2018 for this discovery underlines the significance of this finding. However, despite their success, these checkpoint inhibitors failed to improve survival in PDAC patients. Therefore, I focussed in this thesis on the potential of Natural Killer (NK) cells to attack both tumour and its TME. As professional cancer killing cells, they are prime candidates for battling cancer.

From the plethora of cytokines that could stimulate NK cells, Interleukin(IL)-15 is deemed to be one of the most attractive, evidenced by its third place on the cancer immunotherapy trials network (CITN) priority list of immunotherapy agents. Hence, I sought to investigate the potential of IL-15 stimulated NK cells to kill not only PDAC cancer cells (PCC) but especially also the stromal PSC. Here, I demonstrated that NK cells are capable of killing both cell types and this to a significantly greater extent after IL-15 stimulation. This contact-dependent killing was partially regulated by the NKG2D receptor but the full mechanism still has to be further clarified. I confirmed these results in an ex vivo assay using human tumour-derived PSC and autologous NK cells, underlining the potential of IL-15 for future PDAC treatments.

Next, I investigated the potential of combining IL-15 with a CD40 agonist for the treatment of cancer. The latter has the specific capacity to prime the immune system and has already proven anti-cancer and anti-stromal effects in PDAC. Using two different mouse models of PDAC, I showed that when these agents are combined, they invigorate each other resulting in profound anti-tumour responses and significantly prolonged survival with the majority of mice becoming tumour-free in both models. In-depth research revealed that this combination of immunotherapeutic agents resulted in increased numbers of both NK cells and CD8 T cells and a reduction of regulatory T cells in the tumour.

In summary, this thesis provides evidence for inclusion of NK cell targeting therapies in the treatment of PDAC. In particular, IL-15 shows great potential to accomplish improved treatment outcome. I provided a solid foundation for initiation of an early phase clinical trial investigating IL-15 combined with a CD40 agonist.

​Filip Thiessen

• 12 October 2020
  
• Supervisors: Prof. W. Tjalma, dr W. Steenackers, Prof. G. Hubens and Prof. V. Verhoeven
• Language: Dutch

Abstract

Borstreconstructies met Deep Inferior Epigastric artery Perforator (DIEP)-flappen geven de beste en mooiste resultaten met de minste morbiditeit ter hoogte van de donorplaats. Daarom zijn borstreconstructies met DIEP-flappen de gouden standaard. De selectie van de juiste perforant is de basis van deze techniek, aangezien de flap enkel bevloeid wordt door één enkele perforant. Computed Tomography Arteriography (CTA) is momenteel de standaard techniek om de perforanten aan te duiden, maar de techniek heeft het gebruik van contraststof en röntgen-stralen als nadeel. Uiteraard is niet enkel de selectie van de juiste perforant noodzakelijk om een borstreconstructie met vrije flappen succesvol uit te voeren. Het falen van de DIEP-flap kan een gevolg zijn van: technische problemen tijdens de dissectie van de perforant, problemen met de vaatanastomose of complicaties ten gevolge van compressie of het knikken van de vaatsteel tijdens het vormgeven en inhechten van de flap.

In deze doctoraatsthesis onderzoeken we het gebruik van Dynamic InfraRed Thermography (DIRT) tijdens alle fasen van borstreconstructies met DIEP-flappen. Infrarood (IR) thermografie is een niet-invasieve onderzoeksmethode die de lichaamsoppervlakte temperatuur meet.

Literatuuronderzoek toont aan dat er geen gestandaardiseerde methode bestaat voor het gebruik van DIRT tijdens borstreconstructies. Een nieuwe en gestandaardiseerde meetopstelling voor het gebruik van DIRT tijdens alle fases van borstreconstructies met DIEP-flappen, werd door onze onderzoeksgroep beschreven.

Deze gestandaardiseerde meetset-up werd initieel getest in een preliminaire klinische studie en nadien gebruikt in een grotere klinische studie.

Deze thesis toont aan dat DIRT een alternatieve, niet-invasieve meetmethode is die tijdens alle fases van borstreconstructies met DIEP-flappen kan gebruikt worden.

Jennifer Dhont​

• 8 October 2020
  
• Supervisors: Prof. D. Verellen, Prof. J. Vandemeulebroucke and Prof. J. de Mey
• Language: English

Abstract

The first aim of this thesis was to quantify breathing-induced motion variability, to evaluate the robustness of passive motion management strategies and the reliability of a single pre-treatment measurement. Second, the aim was to develop a markerless tumor tracking framework, applicable on conventional radiotherapy systems, which would enable active motion management, but also real-time monitoring during passive motion management, on a broad scale. The studies performed in this thesis showed that breathing-induced motion variability is large for lesions moving with higher amplitudes, and so passive motion management is only advisable for those tumours moving with smaller amplitudes. Further, a framework for markerless tracking was developed based on three pilars ; the visibility of tumours on real-time images was improved trough the development of dual-energy imaging techniques, a robust tracking algorithm was translated from computer vision to the medical imaging domaine, and a framework was developed to make optimal use of pre-treatment information.

Clemens Heiser​

• 2 October 2020
  
• Prof. O. Vanderveken and Em. Prof. P. Van de Heyning
• Language: English
  

Sara Op de Beeck

• 2 October 2020
  
• Supervisors: Prof. O. Vanderveken, Prof. A. Wellman, Prof. J. Verbraecken and Em. Prof. P. Van de Heyning
• Language: English

Abstract

Pathophysiology of obstructive sleep apnea can be subdivided into 5 endotypic traits: site of upper airway collapse, loop gain, muscle responsiveness and arousal threshold. Each of these traits can be measured using gold standard techniques, however, these are not available in routine measurements.

Currently, only the site of upper airway collapse is assessed in routine clinical practice using drug-induced sleep endoscopy. The 4 other traits are not routinely measured. Recently, however, an algorithm was developed that calculates these traits based on routine clinical polysomnography traits. Our aim was to define these traits using DISE and the algorithm, and to associate them to mandibular advancement device (MAD) and upper airway stimulation (HGNS) treatment outcome.

Our research showed that OSA pathophysiology holds great promise as a patient selection tool for both MAD and HGNS treatment outcome.

MAD efficacy was associated with the site of upper airway collapse, in analogy with HGNS,  and with loop gain, in analogy with upper airway surgery and previous research. Regarding HGNS, the effect of site of collapse is established, yet our research adds that the other 4 endotypic traits, and especially arousal threshold, are also associated with treatment outcome.

Alessandra Quarta

• 24 September 2020
  
• Supervisor: Prof. P. Ponsaerts
• Language: English

Abstract

Neuroinflammation is defined as the development of an inflammatory response in the central nervous system (CNS) upon trauma or disease. The post-insult neuroinflammatory environment is generally colonized by two myeloid cell populations: endogenous parenchymal microglia and blood-derived monocytes that infiltrate the CNS in response to a compromised blood-brain-barrier. Both these cell populations are characterized by multiple functional states and can either display highly pro-inflammatory properties or promote the resolution of inflammation and provide support for tissue regeneration. Steering the activation of microglia and CNS infiltrating monocytes in favour of the latter, hold great promises as a future treatment option for CNS pathologies. Our research group has previously demonstrated that local administration of the immune-modulating cytokine interleukin 13 (IL13) drives microglia and infiltrating monocytes toward the anti-inflammatory phenotype and improves disease outcome in several mouse models of CNS disease. Unfortunately, as the existing cell culture systems to evaluate microglia/monocyte immune properties often overlook the important contribution of CNS environmental signalling to neuroinflammatory processes, a comprehensive in vitro analysis of microglia and monocyte/macrophage behaviour was not possible. The main aim of this PhD research was to establish and validate a novel in vitro platform to investigate similarities and differences in immune reactivity for both microglia and monocytes under pro-inflammatory stimulation, as well as following immunomodulatory treatment with IL13.

In the first part of this doctoral thesis, cellular models of murine induced pluripotent stem cell (iPSC)-derived microglia and iPSC-derived macrophages were generated and characterized. Analysis of their transcriptome profile and evaluation of their phenotypical and functional properties following classical and alternative immune stimulation revealed strong similarities with endogenous microglia and brain-infiltrating monocytes/macrophages, respectively, thus confirming the cellular identity of in vitro differentiated iPSC-microglia and iPSC-macrophages. Furthermore, we provide evidence that a brain-like culture milieu strongly modulates the phenotypic and inflammatory properties of iPSC-microglia and iPSC-macrophages, suggesting that CNS-specific environmental cues play an important role in the restrained immune activation potential of murine microglia as compared to murine monocytes. These findings imply that the development of novel immunomodulating therapeutic approaches will need to (re)consider both cell types independently and in combination within a neural environment.

In the second part of this doctoral thesis, we aimed at unravelling the immune mechanism(s) responsible for the observed in vivo clinical and/or histopathological benefits following IL13-mediated therapeutic intervention. To this end, we explored how pro-inflammatory activation of iPSC-microglia and iPSC-macrophage can be modulated by IL13. Interestingly, our results indicate that IL13 has divergent signalling outcome in microglia as compared to macrophages. While iPSC-macrophages profoundly inhibited the release of pro-inflammatory mediators upon IL13 administration, iPSC-microglia cultures exacerbated inflammation-induced oxidative stress in the presence of IL13. This striking observation was additionally confirmed in vivo following intracerebral delivery of IL13, thus emphasizing that IL13 might operate through multiple and even opposite mechanisms within the inflamed CNS and not simply via a binary activation as previously postulated.

In conclusion, the technological and scientific findings reported in this doctoral thesis reveal the value of iPSC-derived neuro-immune cell culture models as an in vitro tool to unravel the different contribution of microglia and monocytes to the development and resolution of neuroinflammatory responses, as well as to investigate novel therapeutic interventions for inflammation-associated CNS injury or disease.

​Joseph Siewe Fodjo

• 23 September 2020
  
• Supervisors: Em. Prof. R. Colebunders and Prof. A. Njamnshi
• Language: English

Abstract

Epilepsy is a brain disorder characterized by repeated unprovoked seizures, currently affecting over 50 million individuals globally. There is a disproportionate geographical repartition of epilepsy, with 80% of cases living in low- and middle-income countries including sub-Saharan Africa. Among other reasons, infections of the central nervous system are responsible for the substantially greater burden of epilepsy in sub-Saharan Africa. Previous studies have found a high prevalence of epilepsy in areas with a high transmission of Onchocerca volvulus, the parasite that causes onchocerciasis (river blindness), although this has not yet been investigated in detail. Given the limited knowledge regarding the association between epilepsy and onchocerciasis, the NSETHIO research group (University of Antwerp, Belgium) conducted several epilepsy surveys across African villages affected differently by onchocerciasis.

Our studies confirmed that villages with high onchocerciasis transmission also have a high burden of epilepsy. Furthermore, we found that the implementation of interventions to control onchocerciasis resulted in a drastic reduction of epilepsy prevalence and incidence. A wide clinical spectrum of epilepsy was encountered in the surveyed villages, with some patients presenting with generalized seizures, focal seizures, absences, nodding syndrome (head nodding seizures associated with cognitive impairment and stunting), and/or Nakalanga syndrome (severe growth retardation, delayed sexual development, cognitive impairment and sometimes deformities). Persons with epilepsy were most often clustered in villages or households closest to the breeding sites of the blackfly insects which transmit O. volvulus. Our findings lead us to conclude that the different epileptic conditions encountered in the study villages are most likely onchocerciasis-related, and all fall under the umbrella of onchocerciasis-associated epilepsy (OAE). Sadly, OAE cases mostly occurred in remote, poverty-confronted communities with limited access to healthcare.

OAE currently causes a significant disease burden in villages with high onchocerciasis transmission. Fortunately, OAE is preventable by strengthening onchocerciasis elimination programs by ensuring frequent mass drug administration of the drug ivermectin to treat onchocerciasis-infected persons, and/or by destroying blackfly breeding sites to prevent the transmission of the parasite. We recommend that scientists and health decision-makers should urgently enlist OAE on their agenda so as to prioritize research and interventions aimed at treating and preventing OAE in onchocerciasis foci.

​

Tessa De Vrieze​

• 23 September 2020
  
• Supervisors: Prof. N. Devoogdt, Prof. N. Gebruers and Prof. I. Nevelsteen
• Language: English

Zoë Pieters

• 18 September 2020
  
• Supervisors: Prof. N. Hens (UHasselt) and Prof. J. Bilcke
• Language: English

Abstract

Statistical methods are widely used in the medical field to properly assess underlying relations between quantities, or to evaluate the efficacy of pharmaceutical interventions. In this dissertation, we focused on how statistics can be applied throughout the process of conducting a health economic evaluation and how it affects the data analysis of data derived from an antibody-based assay.

When performing a health economic evaluation, the first step is to identify all relevant information, through a systematic search, and combining them using a suitable statistical method. We conducted a meta-analysis using a random intercept logistic regression model, to properly estimate the case fatality risk of enteric fever in Gavi-eligible countries. Another important phase in health economic evaluations is sensitivity analysis in which the effect of varying the values of input parameters, e.g. the case fatality risk mentioned above, on the model outcomes is recorded. A special case of sensitivity analysis is threshold analysis, which is used to determine the threshold value of an input parameter at which a health care strategy becomes cost-effective. Current methods resulted in either incorrect estimates or were time consuming. Therefore, we proposed a statistical method called generalized additive models that overcomes the aforementioned issues. Lastly, we combined existing statistical methods, as well as the one previously described, to perform a health economic evaluation for vaccination against herpes zoster in 50- to 85-year-old Belgian cohorts.

The second part of the dissertation focusses on setting up a general framework for the simulation of data derived from an enzyme-linked immunosorbent assay, also known as ELISA. We generated a standard curve in silico, which describes the relationship between the concentration and the absorbance of interleukin 6, to determine its concentration in an unknown sample. We implemented the current data analysis adopted in a research setting to describe potential variations in the results.

Michael Biggel

• 11 September 2020
  
• Supervisors: Prof. H. Goossens, Prof. S. Van Puyvelde and P. Moons (PhD)
• Language: English

Abstract

Escherichia coli is a usually innocuous member of the human intestinal microbiota but can cause infections when reaching other body sites. In the urinary tract  E. coli is the dominant pathogen and can cause various syndromes ranging from asymptomatic bacteriuria to life-threatening urosepsis. Underlying pathogenesis mechanisms of uropathogenic E. coli (UPEC) are however incompletely understood. In this thesis, we aimed to explore the virulence determinants, population structure, and evolution of UPEC using phylogenomic approaches.

We analyzed 907 whole genome sequences of E. coli isolates associated with invasive urinary tract infections (pyelonephritis, urinary-source bacteremia), non-invasive urinary tract colonization (asymptomatic bacteriuria, cystitis), or isolates from fecal samples. Invasive and non-invasive UPEC isolates were observed to have segregated phylogenetically into distinct lineages, suggesting distinct genetically determined pathogenesis mechanisms. Genome-wide association studies identified the P fimbrial adhesin PapGII as a key virulence determinant of invasive UPEC lineages and the siderophore aerobactin as an important virulence-enhancing determinant. Long-read sequencing in combination with phylogenetic analyses revealed long-term and globally distributed invasive UPEC lineages which emerged after horizontal acquisition of diverse papGII­-containing pathogenicity islands (papGII+ PAIs). Comparative analyses of these papGII+ PAIs identified six major families, which differed in their gene content and preferential chromosomal integration site.

Analyses of isolates belonging to the pandemic lineage ST131 revealed recent horizontal transfer events of papGII+ PAIs in the E. coli population resulting in the formation of additional invasive UPEC lineages. Moreover, papGII+ ST131 isolates harbored a significantly higher AMR-conferring gene content than ST131 isolates lacking papGII. This finding suggests a joint evolution of virulence and AMR phenotypes. Genotype-to-phenotype predictions suggest that the papGII+ ST131 lineages are both highly urovirulent and resistant to commonly used antibiotics, including fluoroquinolones and 3rd-generation cephalosporines.

In summary, the work offers novel insights into the evolution and key virulence determinants of invasive UPEC and provides a framework that contributes to the surveillance of invasive UPEC isolates.

Joke Muys

• 8 September 2020
  
• Supervisors: Prof. Y. Jacquemyn and Prof. B. Blaumeiser
• Language: English

Patrick D'Haese

• 7 September 2020
  
• Supervisors: Em. Prof. P. Van de Heyning, Prof V. Van Rompaey and Em. Prof. M. De Bodt
• Language: English

Abstract

According to the latest data of the World Health Organisation1, over 5% of the world’s population has a disabling hearing loss. This accounts for 466 million people worldwide. The current predictions of WHO estimate that by 2050, this would increase up to 900 million people.

Hearing loss is an important health concern with substantial economic and societal costs. Children and adults with a severe and profound hearing loss are more likely to have a poor academic performance and have an increased likelihood of being unemployed or underemployed. They are more likely to experience difficulties in both their professional and social life and are often stigmatized in society. Without adequate treatment, many adults with severe to profound bilateral hearing loss are not able to perceive everyday environmental noises regardless of how loud or nearby they are. For children and adults with a severe or profound hearing loss, cochlear implants are currently standard of care.

Currently there is a knowledge gap existing on the awareness levels towards hearing loss and its treatment options such as cochlear implants and this with health care providers and with patients. This seems to lead to inequities between the patients receiving such treatment and the patients not receiving such treatment.  More specifically in Europe, many adults who could benefit from a cochlear implant do not have one despite their availability via national health care systems, the proven clinical outcomes and the high clinical impact. 

 The goal of this research project is to determine the knowledge and beliefs of otorhinolaryngologists in a secondary setting in selected economically advanced European countries concerning severe hearing loss and cochlear implants as well as the awareness level of adults in the same set of countries concerning the same factors through a custom-made survey based on the Health Belief Model. 

After defining this baseline data, information was provided through a two-pronged digital campaign in these same countries to the same study groups. After this, the same custom-made survey was administered in the two study groups and a potential effect on the awareness level was measured.  

Based on the results in these two study groups, initial conclusions were made on the knowledge levels, beliefs and insights on severe hearing loss and cochlear implants in the selected countries. In addition, data demonstrates which communication channels should be used, to increase the awareness level on hearing loss and cochlear implants in these two study groups.

Jade Pattyn​

• 21 August 2020
  
• Supervisors: Dr. A. Vorsters, Prof. dr. W. Tjalma and Em. Prof. dr. G. Leven
• Language: English

Abstract

Incidence and mortality of cervical cancer has reduced in countries with well-organized screening and treatment programs, and the use of prophylactic HPV vaccines will further accelerate this decrease. Nonetheless, challenges remain, like non-invasive options for monitoring interventions to control HPV. To date, HPV DNA testing of clinician-obtained cervical cells is the reference for identifying cervical HPV infection(s), while the evaluation of immunogenicity in HPV vaccine trials relies on serology. The use of first-void urine (FVU) could have several advantages over the current more invasive sampling. Moreover, the assessment of both, HPV infection and antibody presence, on such a readily obtained and non-invasive sample, is particularly attractive and could be of great value for the international HPV research community.

With a view towards the use of FVU for the follow-up of preventive and therapeutic interventions, this thesis aimed to investigate and further improve the detection of HPV and HPV-specific antibodies in FVU. Besides, the use of FVU to follow-up HPV vaccination and cervical precancer treatment was examined.

We demonstrated that there is no advantage in HPV detection in FVU collected in the morning vs. later during the day and showed the potential effect of an FVU collection device to detect HPV. Besides, we provided knowledge on the standardized and optimized protocol which has significantly enhanced the sensitivity of urinary HPV detection and make urine a potentially efficacious and accurate alternative to cervical samples. Also, based on a review of the literature, the presence of HPV antibodies at the cervix, using cervicovaginal secretions as a proxy, has been investigated and found feasible. Furthermore, with respect to method optimization, we compared the measurement of HPV antibodies in FV urine using a multiplex VLP-based ELISA (M4ELISA) with previously reported data. Correlations with HPV vaccination status and serum samples were found using those two different HPV immunoassays not yet specifically designed for urine. However, expected better sensitivity for M4ELISA was not observed. At last, preliminary data of two studies are reported that investigated the use of FVU for the follow-up of HPV vaccination and in a test-of-cure setting.

In summary, though further studies are warranted, this dissertation provided information and data indicating that FVU may be a viable non-invasive option for monitoring interventions to control HPV and may therefore become an important tool in cervical cancer elimination plans.

Esther Bartholomeus

• 10 July 2020
• Supervisors: Prof. G. Mortier, dr P. Meysman and Prof. B. Ongunjimi
• Language: English

Abstract

The human immune system is a very complex defense mechanism, consisting of different levels of interacting cells and molecules, to keep out and eliminate pathogens and foreign particles. The immune system can be divided into three main categories: 1) the physical barriers, 2) the innate immune system that creates immediately non-pathogen-specific immune responses, and 3) the adaptive immune system that can activate pathogen-specific immune responses, admittedly after recognition of the pathogenic antigen, differentiation processes and clonal expansion. The adaptive immune system can further be subdivided in the cell-mediated immunity (T-lymphocytes) and the humoral immunity (B-lymphocytes). It is also the key player to build up and maintain protection against a specific pathogen for years, by producing long-lived memory cells and antibodies. A natural infection can be mimicked through vaccination: stimulation of the immune system to build up protection without carrying over the disease itself.

To study the activity of immune cells present in blood and monitor the overall immune responses, we use differential gene expression. Using RNA sequencing, we can determine a gene expression profile which contains all present mRNA transcripts and the amount of each transcript (counts), including all immune-relevant ones. By applying differential gene expression, we study the significant differences in gene expression between 2 conditions. The combination of specific down- or/and upregulated gene transcripts can indicate changes in certain pathways. To confirm the performance and efficiency of this method, three proof of concept studies were designed.

In part I we determined the influence of two vaccines on the immune system of healthy volunteers: A) de novo Engerix-B vaccine dose and B) an additional Priorix vaccine dose To pinpoint differentially expressed genes, we compared each post-vaccination gene expression profile to the pre-vaccination profile at day 0. Significant alterations in gene expression levels could imply that immune-related pathways are activated by the vaccination.

Determination of differentially expressed genes is also applicable in infectious diseases. For part II we applied our method to children, diagnosed with acute meningitis, caused by viruses or bacteria. Differentially expressed genes were studied by comparing the acute gene expression profiles with the profile of the corresponding control sample. Further, we looked into differences in gene expression profiles between bacterial and viral cases to create a predictive model.

To conclude, gene expression profiling can be used to monitor immune responses after vaccination or even during an infection.

Maja Lopez Hartmann

• 8 July 2020
• Supervisors: Prof. R. Remmen, Prof. J. Wens and Prof. S. Anthierens
• Language: Dutch

Abstract

Governments and healthcare authorities acknowledge the increasing role of the informal caregiver in the care for community-dwelling frail elderly, and they are aware of the necessity to support them in their role so as to guarantee a qualitative home care for the frail elderly. In Flanders informal care and support for informal caregivers have been paid more attention to during the last few years by, among others, initiatives like the Flemish informal care plan 2016-2020 of the former minister of welfare, public health and family, mister Jo Vandeurzen [1] and by largescale research projects on informal care and informal care support in Belgium and Europe [2-4].

Several supporting measures and services for informal caregivers are available, such as among others informal care fees, flexible leave systems, respite care and psycho-social support. But nevertheless under-utilization of the available supporting measures and services is a lingering problem with informal caregivers of the community-dwelling frail elderly.
Social support by people close to the informal caregiver, and hence more accessible, is possibly better accepted. International studies on social support for informal caregivers show positive results on psychological effects such as experienced burden. 

In order to be able to understand how informal caregivers experience informal care and social support, it is necessary to do some research into the concept of informal care support starting from the point of view of the informal caregiver himself.  The various studies bundled in this doctoral thesis aim to gain knowledge on how informal caregivers of community-dwelling frail elderly experience the informal care and how they experience social support in this role.

Mattia Palmieri​

• 8 July 2020
• Supervisors: Prof. H. Goossens, Prof. A. van Belkum and P. Moons (PhD)
• Co-supervisor: A. Suls (PhD)
• Language: English

Abstract

While antibiotics still represent the major antibacterial agents for the treatment of bacterial infections, an increasing number of bacteria is becoming (multi-drug) resistant (MDR), complicating the treatment of infections. Carbapenems are highly effective antibiotics commonly used for the treatment of severe bacterial infections of MDR bacteria, which are resistant to first-line antibiotics. Of major concern, carbapenem resistance is on the rise, and in some countries it is so high that other drugs, usually reserved as last options, are widely used. As an example, colistin, an old drug that was essentially unused due to its toxicity, it’s now commonly adopted in some countries, and resistance toward this antibiotic is on the rise.

Of the several pathogens associated with MDR, carbapenem-resistant K. pneumoniae and A. baumannii represent major concerns. Both pathogens frequently cause outbreaks of infections, while strains which are resistant to all available antibiotics are emerging. Concerning K. pneumoniae, a novel kind of superbug has been emerging recently. While MDR K. pneumoniae clones causing hospital outbreaks and hypervirulent, drug susceptible clones causing severe community-acquired infections were two separate concerns, strains that showed convergence of the two traits are emerging. Acquisition of hypervirulence and resistance genes have been observed in MDR and hypervirulent clones, respectively, especially in Asia. Tracking the emergence and evolution of such novel clones, which cause severe infections with limited treatment options, is fundamental.

The decreasing cost of Whole Genome Sequencing (WGS) is allowing its increase implementation in bacterial diagnosis. However, there is still a lack of surveillance investigations for last-line resistance mechanisms and for convergence of resistance and hypervirulence traits. Moreover, while the phenotype prediction from the genomic data showed encouraging results, the understanding of the genetic resistance mechanisms of some drugs, such as colistin, is still limited, and novel in silico tools for the phenotype prediction are needed.

We employed WGS and bioinformatics, together with phenotypic techniques, to address different problems: i) to decipher the colistin resistance mechanisms and the genomic epidemiology of clinical isolates of K. pneumonia and A. baumannii from countries where carbapenem resistance is sky-high, and colistin represent a life-saving agent. ii) to explore the longitudinal population dynamics of K. pneumonia in a major Chinese hospital, focusing on the simultaneous carriage of resistance and hypervirulence genes. iii) to predict the phenotype of K. pneumonia strains from their genomes. iv) to study a novel carbapenemase-encoding gene obtained from environmental bacteria.

Kevin Kuppens

• 3 July 2020
• Supervisors: Prof. N. Roussel, Prof. F. Struyf and Prof. J. Nijs
• Language: Dutch

Abstract

Shoulder pain is a highly prevalent problem in the general population. Studies have shown that up to 66% of all people experience shoulder pain during lifetime, and about half of them develop chronic or recurrent shoulder pain. In a specific population of performers (e.g. overhead athletes and musicians) chronic shoulder pain is prevalent and impactful. The mechanism of central sensitization (CS) provides a possible explanation for the development of this persistent type of shoulder pain. CS is defined as “an amplification of neural signaling within the central nervous system that elicits pain hypersensitivity”. The hypersensitivity of the nervous system leads to increased experience of stimuli and sensations.

Based on our findings we can however summarize that central sensitization is not a characteristic feature in patients with chronic shoulder pain in general, nor in performers suffering chronic performance related shoulder pain. The discrepancy between our results and some of previously reported findings and the high variability between subjects apparent in our results does however suggest the need for future research and clinical cautiousness.

From a cognitive, emotional and behavioral point of view differences between shoulder pain patients and healthy controls are clear. For example, those with chronic shoulder pain report more catastrophic thoughts such as helplessness and they show more signs of tension, depression and anger. These psychosocial factors might negatively influence pain experience. We have found a high diversity in the way patients perceive their shoulder pain problem. 

Training volume and physical activity status is related to mechanical pain sensitivity in healthy people and in patients with chronic shoulder pain. Those who are more physically active show less mechanical pain sensitivity. They are also less characterized by psychosocial factors such as pain catastrophizing known to negatively influence pain experience. The cross-sectional nature of our study designs however limits our ability to specify the directions of these associations.    

The reported studies in this thesis and the body of existing knowledge highlight the complexity and multimodality of chronic musculoskeletal shoulder pain, more specifically in performers. The high variability in obtained study results within patient groups reflects the need for subgroup analysis in research and the importance of an individually tailored biopsychosocial approach in clinical assessment and management.

​Tamaya Van Criekinge

• 2 July 2020
• Supervisors: Prof. S. Truijen and Prof. W. Saeys
• Language: Dutch

Abstract

Approximately 80 percent of all stroke survivors show mobility deficits after their diagnosis and select gait recovery as the primary therapy goal. However, gait is not merely the ability to walk up and down a corridor. People living with stroke need to walk independently, on unstable surfaces, in crowded environments while performing dual tasks. To optimize their walking pattern, we need to understand the underlying impairments. The importance of the trunk during walking is often neglected and still misconceived. The aim of this thesis was to enhance our understanding about the trunk’s involvement during walking after stroke and how the walking pattern recovers by resolving truncal deficits.

Detailed analysis of the literature provided knowledge concerning the state of the art on trunk motion and trunk rehabilitation, whereby gaps were identified and further investigated. First, an instrumented gait analysis was performed on 57 stroke survivors and 105 healthy individuals during a cross-sectional study. The use of the Full Body Plug-In Gait model (Vicon), together with a specified trunk model and electromyography, made comparison of trunk and lower limb kinematics, spatiotemporal step parameters and muscle activity between healthy adults and stroke survivors possible. Second, of the participants with stroke, 39 were included in a randomized controlled trial receiving either trunk or cognitive training.

Findings suggest that important deviations in trunk kinematics during walking were present after stroke. Stroke survivors walked with increased mediolateral/anteroposterior trunk movements, increased thoracic flexion, a neutral position of the pelvis during stance, a pelvic hike during swing, and a backward rotation of the hemiplegic thorax and pelvis resulting in more in-phase coordination. In addition, patients with more severe lower limb impairments had more pronounced deficits in truncal motion, especially in the frontal plane. Second, trunk training was able to improve balance and mobility. These improvements in gait performance were not secondary to changes in lower limb kinematics but due to decreased anteroposterior movements of the thorax and an increase in the fatigue-resistance of trunk muscles.

The results of this thesis showed that trunk impairments are clearly present during walking after a stroke. By giving patients trunk exercises, their walking pattern was optimized which ensures us that trunk exercises should be incorporated in treatment strategies for gait recovery. Results suggest that stroke survivors adopted a more energy efficient walking pattern after trunk training. However, this was not directly investigated in the current trial and necessitates further study.

​Andreu Coello Pelegrin

• 1 July 2020
• Supervisors: Prof. H. Goossens and dr A. van Belkum
• Language: English

Abstract

Pseudomonas aeruginosa is a rod-shaped, gram-negative Gammaproteobacteria common in healthcare-associated infections. It is responsible for a wide range of diseases from local and acute infections to systemic and chronic diseases, some of which can be life-threatening. P. aeruginosa has a “plastic” genome, meaning that its size can vary, and therefore encode a variable number and wide range of genes, including those encoding transporters, metabolic pathways, virulence and antimicrobial resistance genes.

This thesis has an introductory chapter, in which the antimicrobial resistance (AMR) crisis is placed in context and the main clinical aspects of this bacterial species are detailed (Clinical relevance, Host-pathogen interaction, AMR mechanisms, epidemiology and treatment of multi-drug resistant isolates). Additionally, it has a short section on the role of molecular diagnostic tools in infectious diseases. The introduction is followed by four chapters with experimental data.

The first one describes the epidemiology and carbapenem resistance mechanisms from P. aeruginosa in a large intensive care unit in Jakarta, Indonesia, revealing endemic carbapenemase producing strains, which are associated with prolonged ICU stay. Colonisation or infection of patients with carbapenem resistant P. aeruginosa is affecting survival.

The second chapter analyses the same setting to assess the impact of a multifaceted infection control intervention analysed at the microbial genomic level, documenting the usefulness of whole-genome sequencing (WGS) in combination with clinical data to evaluate the impact of an infection control intervention.

The third experimental chapter evaluates multiple whole-genome sequencing-based typing approaches for P. aeruginosa. cgMLST, wgMLST and cgSNP were found to provide the highest level of resolution allowing detailed epidemiological analysis of local outbreaks and international dissemination; MLVA is confirmed to be a suitable alternative for accurate typing of P. aeruginosa, useful in settings where the transition towards WGS is currently not feasible.

The fourth manuscript analyzes the phenotypic and genomic variability of serial peri-lung transplantation P. aeruginosa isolates from cystic fibrosis patients. It is observed that despite lung transplantation and associated clinical and therapeutic measures, all patients remained persistently colonized with similar strains, and that mild variations were observed at isolate level. The study concludes that using a combination of clinical and multi-omics approach could help to devise the appropriate treatment for the patients.

In conclusion, the thesis shows that WGS and downstream bioinformatics allow for detailed epidemiological analyses of collections of P. aeruginosa strains, providing new insights in their local and global dissemination.

Sabrina Kitaka​

• 1 July 2020
• Supervisors: Em. Prof. R. Colebunders, dr C. Nöstlinger and Prof. P. Mukose
• Language: English

Abstract

Advances in early infant diagnosis of HIV infection in HIV exposed children and the increased availability and access to pediatric HIV treatment have reduced the mortality and morbidity of children born with HIV, resulting into more children surviving into adolescence. Eighty percent of all adolescents living with HIV (ALHIV) globally live in sub Saharan Africa. Uganda, like many resource limited countries has made significant strides in the fight against HIV/AIDS. The rapid scale up of anti-retroviral therapy (ART) in this country has decreased the morbidity and mortality of ALHIV. As these ALHIV mature and their life expectancy increases, they face several challenges ranging from adhering to long term ART and negotiating through various situations and relationships to survive into adulthood. While the majority of available studies including ALHIV focus on their medical treatment, this thesis aims to go beyond the treatment response as such. The thesis describes not only the response of ART on the growth and development of perinatally infected adolescents, but puts emphasis on the exploration of the psychosocial challenges ALHIV face as they grow up and their lives become normalized. This includes also describing the sexual and reproductive health needs and sexual activity among ALHIV. This thesis adds a comprehensive description of psychosocial and psychosexual challenges as they manifest in clinical/treatment settings dealing with ALHIV to the available body of knowledge on the needs of ALHIV. Its results therefore are relevant not only from an academic perspective but also for health care providers working in such settings. The findings may contribute to increasing youth-friendly, evidence-based HIV services. 

This thesis includes studies conducted in Uganda and Kenya which are among the high HIV burden countries. Four studies resulting in five articles highlight three intertwined challenges related to disclosure of HIV status, treatment adherence and prevention of HIV transmission. Based on our study findings, strategies to improve the health and wellbeing of ALHIV in resource limited settings are proposed. In the first study, adolescents with predominantly perinatally-acquired HIV infection and significant disease burden showed appropriate virological and immunological response to ART in addition to having clinically significant improvements in growth and some improvement in sexual maturation. In the second study, we examined the perceptions of young people living with HIV in Uganda about current norms around HIV serostatus and treatment disclosure. Our findings reinforce the concept of HIV disclosure as a process, not a one-time event. We studied disclosure processes and outcomes.

Two studies assessed the sexual and reproductive health behaviors of ALHIV: a qualitative study explored the meaning ALHIV attribute to sexuality and their sexual norms in the light of shaping their sexual and social identities. About a quarter of the young participants reported prior or current sexual experience. The quantitative study demonstrated that early sexual activity remains an important risk factor for HIV transmission and potentially results in negative health consequences including onward transmission of sexually transmitted infections.

The two studies revealed knowledge gaps relating to reproductive health, HIV transmission, and contraceptive methods. Motivations for safe preventive sexual behavior included having specific future aspirations, good counseling, and fear of the consequences of sexual activity such as unwanted pregnancies. Barriers to adopting preventive behaviors included personal factors (i.e. alcohol use), interpersonal factors (i.e. ignorance of serostatus of sexual partners, peer pressure), social factors (HIV-related stigma) and poverty as a structural determinant. In addition, desire to have children played an important role for the older ones. Young seropositive people in this setting lacked specific behavioral skills, such as disclosure of HIV status to their sexual partners, which was closely linked to fear of rejection and stigma.

This thesis clearly demonstrates that HIV positive adolescents and young people are able to respond well to ART and that they are able to grow; however, as they grow, they may face specific challenges of disclosure and navigation of their sexual maturation. Interventions in this field need to be age appropriate, and based on the psychosocial developmental stage as well as being tailored to young people’s specific needs. Structural interventions should at the same time address and reduce HIV-related stigma and support the socio-economic needs of young people living with HIV.

Despite the increased attention and commitment to the pediatric and adolescent HIV agenda, further efforts are required to respond to the glaring gaps. The global AIDS response is at a critical point where the successes of antiretroviral therapy provision is now competing with complacency. The ambitious global targets of ending AIDS are not being realized in a timely manner as expected by the UNAIDS. For instance, there are still nearly a million people dying each year from AIDS-related illnesses and only three out of every four persons living with HIV knows their HIV status. These targets are even less achieved for adolescents and young people who contribute to the highest AIDS-related deaths and the new transmissions.

Moreover, there is a limited number of health-care workers specialized in taking care of adolescents and young people. There is also continuing stigma and discrimination and this could result in a prevention crisis. When ALHIV start to engage in sexual activity and are not able to disclose their HIV status to their sexual partners there is an added risk of transmission. This is particularly plausible when they are not adhering well to their treatment and remain virally unsuppressed. For ALHIV, it is critical that the interventions put in place to prevent onward transmission, and maintain their healthy livelihood are geared towards making these interventions reachable to them in an adolescent responsive manner. This can be done through evidence-based interventions and policies that comprehensively address the multiple needs of the ALHIV.

Patrick Soentjens

• 26 June 2020
• Supervisors: Prof. P. Van Damme, Prof. E. Bottieau
• Language: English

Abstract

Shortened and simpler rabies PrEP and PEP ID schedules, using low-dose vaccine volumes can be considered as a good illustration of ‘less can be more’.

The story of a first successful post-exposure treatment against rabies by Josef Meister, who was bitten by a rabid dog, was performed by Louis Pasteur in 1885. This treatment, which comprised 13 injections given over 9 days ended with the injection of a fully virulent virus. Today, the new post-exposure prophylaxis (PEP) recommended by World Health Organization (WHO) can be simplified to a total of six intradermal micro-injections (one dose of 0.1 mL in two separate arms) divided over 3 days in one week (day 0, day 3 and day 7). Our team evaluated shortened combined pre-exposure prophylaxis (PrEP) and PEP schedules over 3 days and 2 days in two randomised clinical trials, of which an adapted version is now promoted by WHO as first-line PrEP and PEP over in total 3 days.

Bringing the rabies prevention schedule 134 years later from nine visits to three or to two assures clinical effectiveness of this regimen with a safer profile, better compliance, and drastically simplifies rabies prevention procedures for the traveller.

Athina Van Gasse

• 26 June 2020
• Supervisors: Prof. D. Ebo, Prof. M. Hagendorens and Prof. V. Sabato
• Language: English

Abstract

Unverified and false “β-lactam allergies”, mainly to the first-line preparations natural penicillin and aminopenicillins, have evolved into a worldwide plague with serious medical and financial consequences. From this thesis it appears that as much as 12% of the individuals attending the outpatients’ clinic of Allergology and Pediatric Allergology of the Antwerp University Hospital claim to have a “penicillin allergy”. However, in 91% of these individuals this claim appears to be false, as they tolerated these antibiotics during a controlled drug challenge. Importantly, as these cases could be safely delabelled, we were able to improve their antibiotic stewardship, mainly by safeguard them against the unnecessary risk for use of suboptimal and expensive second-line treatments.

From the literature and our own experience it is clear that judicious diagnostic work-up by a trained physician is absolutely necessary in every case of both witnessed or self-reported “penicillin allergy”. However, diagnosis of β-lactam hypersensitivity reactions is not always straightforward and optimization of the diagnostic approach of β-lactam hypersensitivities is needed. Therefore, we studied the performance of new or recently introduced diagnostics.

First, in the context of nonimmediate hypersensitivity reactions to amoxicillin and amoxicillin clavulanic acid, we showed that a CD154-based flow cytometric lymphocyte activation test is a safe and quick diagnostic test, especially in cases with mild cutaneous nonimmediate drug hypersensitivity reactions to amoxicillin or amoxicillin clavulanic acid, and that a prolonged drug challenge extending over several consecutive days is of limited use.

In our country cefazolin has evolved to one of the major causes of perioperative anaphylaxis. We explored the performance of a recently developed specific (s)IgE assay to cefazolin. We observed that neither sIgE to cefazolin nor a sIgE/tIgE ratio were of added value in the diagnosis of cefazolin hypersensitivity.

Finally, it is known that cross-reactivity among β-lactam antibiotics is unpredictable but mostly related to the R1-side chain. However, we demonstrated that fine structural differences in the R1-side chain can suffice to explain absence of cross-reactivity and clinical tolerance. Clearly, molecules with a similar, but not identical R1-side chain, should not be precluded or administered using a desensitization protocol, provided they test negative in skin testing.

In conclusion, self-reported “penicillin allergy” has grown into a vast epidemic with unacceptable consequences for the individual patient and the society. Further efforts are required to optimize and harmonize a cost-conscious diagnostic approach of “penicillin allergy” and “β-lactam allergy” in general.

​Thijs Vande Vyvere

• 24 June 2020
• Supervisors: Prof. P. Parizel and Prof. P Pullens
• Language: English

Abstract

Neuroimaging techniques play a pivotal role in the diagnosis and follow-up of patients with Traumatic Brain Injury (TBI). Imaging findings determine patient management and influence the clinical course. Unfortunately, conventional evaluation of imaging studies and free-text radiologic reporting is problematic in patients with TBI, mainly due to the significant differences in content, length, style and language of the generated radiology reports. Moreover, there is substantial inter-observer variation in how pathology is characterised, even between experts.

In order to advance clinical decision-making and research into TBI, a more complete, precise and consistent characterisation of brain pathology was urgently needed. In 2010, a multidisciplinary task force, under the aegis of the National Institute of Health (NIH) and the National Institute of Neurological Disorders and Stroke (NINDS), created a framework for a more structured way of radiologic reporting in clinical trials, by providing a standardised language of "common data elements" (CDEs). Despite the many presumed benefits of this standardised framework, a thorough investigation and validation was still lacking. 

We performed a standardised central radiology review, based on the NIH/NINDS CDEs, on over 4,000 acute non-contrast computed tomography (NCCT) scans, uploaded to a central imaging database for the large pan-European CENTER-TBI study. We explored inter- and intra-observer agreement, compared centralised versus local assessment, and we created regularised logistic regression models to investigate the prognostic relevance of the different NIH/NINDS CDEs. In addition, we also developed and tested machine learning algorithms, intended to objectively quantify relevant imaging characteristics.

Our results indicate that on-site radiologic evaluation and reporting suffers from substantial inconsistencies, which is highly detrimental in multi-centre studies. Conversely, we showed that an independent central radiology review process, using NIH/NINDS CDEs, offers a more consistent way of characterising pathology, with high levels of inter-and intra-observer agreement. We also demonstrated that, on a large scale, this kind of characterisation allows for extensive data mining and the development of strong clinical predictive models. Furthermore, our automated machine learning-based approach achieved good performance for the segmentation of lesion volumes, cisternal volumes, and midline shift measurement.

In conclusion, our work shows that standardised radiologic evaluation and reporting, using the NIH/NINDS CDEs, combined with automation of certain aspects of radiologic evaluation, is very promising and can significantly advance clinical research. Based on our findings, we made recommendations for clinical radiology reporting, and developed an image interpretation checklist, accompanied by a comprehensive and fully illustrated patho-anatomic atlas, with over 200 images from the CENTER-TBI study. Our efforts can help physicians and researchers to reliably and reproducibly interpret NCCT scans of brain-injured patients, thus paving the way towards a more globally accepted standardised evaluation and reporting of acute traumatic brain injuries.

​Judith Derdelinckx

• 22 June 2020
• Supervisors: Prof. P. Cras, Prof. Z. Berneman and Prof. N. Cools
• Language: English

Danique Beijer

• 22 June 2020
• Supervisors: Prof. J. Baets and Em. Prof. P. De Jonghe
• Language: English

Gertrude Namale

• 18 June 2020
• Supervisors: Prof. P. Cras and Prof. L. Yperzeele
• Language: English

Abstract

Background: The trend towards an increasing burden of cardiovascular diseases including stroke in developing countries is of great concern. In sub-Saharan Africa (SSA), there is a significant burden of ischemic stroke and hemorrhagic stroke and yet data on risk factors and outcomes for each stroke type are sparse.  In Uganda, stroke is one of the top five causes of adult death, and it accounts for 3.7% of all admissions in Ugandan hospitals. The overall aim of the thesis was to assess the risk factors and outcomes for both hemorrhagic and ischemic stroke among adults, and to document caregiver burden and experiences in Uganda. These findings will inform policy to plan for the required resources to meet this increasing stroke disease burden in Uganda.

Methods: The thesis describes four sub-studies which were performed between December 2016 and March 2019 at St Francis Hospital Nsambya, Kampala Uganda. The overall study design was a mixed-methods approach. SUB-STUDY I was a systematic review to understand risk factors for haemorrhagic and ischemic stroke in Sub-Saharan Africa. SUB-STUDY II was a prospective hospital - based case control study to assess risk factors for haemorrhagic and ischemic stroke at an urban hospital in Uganda. SUB-STUDY III was a qualitative cross sectional study to document caregiver burden and experiences on caring for a stroke patient. SUB- STUDY IV was a prospective hospital - based cohort study to examine short term outcomes of haemorrhagic and ischemic stroke and associated factors. All study participants were consented and enrolled consecutively.

Results: The findings demonstrated that hypertension, diabetes and HIV were independently associated ischemic stroke and hemorrhagic stroke. Mortality was high during the first 30 days of stroke. Mortality was also higher among hemorrhagic stroke compared to ischemic stroke patients. The caregivers experienced caregiver burden mainly due to high care giving demands, financial difficulties, emotional distress, and grief, yet there was lack of rehabilitation and follow up support services in their communities.

Conclusions: Interventions to reduce modifiable risk factors among populations in Uganda are urgently needed. Given the high mortality during the acute phase, critically ill stroke patients would benefit from interventions established as the post-stroke- standard of care in the country. There is need for interventions to support stroke patients and their caregivers.

​Julia Mwesigwa​

• 12 June 2020
• Supervisors: Prof. JP. Van geertruyden, Prof. U. D'Alessandro and Prof. J. Achan
• Language: English

​Wessel van de Veerdonk​

• 8 June 2020
• Supervisors: Prof. P. Van Hal, Prof. M. Peeters & Prof. S. Hoeck
• Language: English

Abstract​

Colorectal cancer (CRC) has a large impact on our European society through an estimated 500,000 new colorectal cancer cases and 442,000 deaths which occurred in 2018 and accounted for about 1 in 10 cancer cases and deaths. For Belgium (2018), CRC was estimated to occur in 9,346 persons and mortality in 3,224 persons. To slow the growing trend of precursor lesions, CRC incidence and mortality, preventative interventions are an excellent approach, considering that most CRCs develop from precursor lesions over the course of several years without symptoms. The CRC screening approach (secondary prevention) is part of the solution due to the long latent period (time between first neoplasia and symptoms) which enables early detection of CRC. Based on prominent randomised controlled trials (RCTs) and EU guidelines, screening for CRC by the faecal occult blood test (FIT) followed-up by a colonoscopy increased over the past 20 years in the European Union, where Flanders (Belgian region) started with CRC screening in October 2013. Because this start up happened rather recently, naturally, there is lacking scientific knowledge regarding CRC screening in the Flemish population.

This PhD focused on the performance of the Flemish population-based CRC screening programme. Specifically, we investigated whether the FIT results, screening participation, age group to be included and the number of interval cancers were representable for the whole Flemish screening-eligible population. This resulted in fairly clear outcomes, some examples; the odds for detecting CRC in men aged 74, with a FIT result of ≥1000 ng/ml, was higher by a factor of 58.43 than that for women aged 56, with a FIT result of 75 ng/ml. However, nothing was communicated about these differences in the result letter, which has since been partially amended. Another example that we discovered, was that every other nationality (currently and at birth, except Dutch) compared to the Belgian nationality participated significantly less in the CRC screening programme. Likewise, people with a relatively low income participated significantly less.

Would you like to learn more about the examples discussed? Topics such as interval cancers, extension of the target age for the CRC screening programme or more theory about the idea of ​​risk stratification? You can find out during the public defense or read it in the doctoral thesis.

​

​Matilda Berkell​

• 27 May 2020
• Supervisors: Prof. H. Goossens and Prof. S. Malhotra
• Language: English

Abstract

Clostridioides difficile infection (CDI) is the most common form of infectious antibiotic-associated diarrhea (AAD) causing considerable morbidity and mortality in acute-care facilities. Hospitalized patients receiving broad-spectrum antibiotic treatment are particularly susceptible to CDI as a result of antibiotic-induced perturbations in the intestinal microbiota. Thanks to the evolution and increasing accessibility to next-generation sequencing (NGS) technologies, substantial advances have been made toward understanding C. difficile transmission, virulence, and phylogeny. However, much still remains unknown about this opportunistic pathogen.

In this thesis, we aimed to identify early microbial biomarkers predictive of AAD in patients undergoing broad-spectrum antibiotic treatment, with a particular emphasis on CDI. We further aimed at understanding the phylogeny of toxigenic C. difficile strains by assigning a genomic context to their infection potential.

Here, we present a high-resolution, genome-wide characterization of the Leeds-Leiden/ECDC strain collection of primarily toxigenic C. difficile strains (n = 73). This effort constitutes, to our knowledge, the largest chromosome-wide comparative genomics study to date that investigates C. difficile phylogeny. The human intestinal microbiota was mined for predictive microbiota-based biomarkers of CDI in a large, elderly, hospitalized population. This resulted in the development of a predictive algorithm enabling enrichment of patients at high-risk of CDI, which ultimately resulted in the filing of a patent. Longitudinally collected fecal samples from the same study population were further assessed for structural microbial alterations following broad-spectrum antibiotic treatment, which showed antibiotic-specific alterations in microbial composition with a resulting alteration in metabolism.

In conclusion, this thesis provides a comprehensive investigation into genomic and microbiota-based facilitators of CDI by investigating C. difficile phylogeny and genomic features of C. difficile expressed as virulence and transmission traits as well as a thorough investigation into structural changes in the human intestinal microbiota pre and post antibiotic treatment.

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​Housseini Dolo​

• 20 May 2020
• Supervisors: Em. Prof R. Colebunders and Prof M. G. Basáñez
• Language: English

Hanne Verbelen

• 30 April 2020
• Supervisors: Prof. W. Tjalma and Prof. N. Gebruers
• Language: English

Abstract

Het doel van dit doctoraatsproject is om inzicht te krijgen in de morbiditeit na de behandeling van borstkanker. Met de introductie van de sentinelklierprocedure (SLNB) en de borstsparende heelkunde, is borstkankerchirurgie geëvolueerd naar minder invasieve technieken. Nochtans zouden de behandelingsgerelateerde arm-, schouder-, en borstklachten niet mogen worden onderschat. Deze thesis bestaat uit 2 delen: arm- en schouderklachten na SLNB en borstoedeem na borstsparende heelkunde en radiotherapie.

In het eerste deel werden verschillende arm- en schouderklachten na SLNB in de literatuur nagekeken zoals pijn, bewegingsbeperking, krachtsverlies, axillary web syndrome, scapula alata, gevoelsstoornissen en lymfoedeem. Hoewel ze minder vaak voorkomen in vergelijking met een volledige okseluitruiming, mogen ze niet worden miskend. Bovendien werd aangetoond dat een aanzienlijk aandeel patiënten nog steeds last heeft van arm- of schouderklachten, maanden en zelfs jaren na hun kankerbehandeling, wat een impact heeft op de activiteiten van het dagelijks leven.

In het 2^de deel van dit project wilden we graag de aandacht vestigen op een minder gekende klacht na de behandeling van borstkanker, namelijk borstoedeem na borstsparende heelkunde en radiotherapie. In de literatuur werd een incidentie tussen 0% en 90,4% gevonden. Deze grote variatie komt voornamelijk door het gebrek aan een uniforme definitie en gestandaardiseerde meetinstrumenten. Daarom wilden we graag een bruikbaar meetinstrument ontwikkelen om borstoedeem te diagnosticeren, namelijk de Breast Edema Questionnaire (BrEQ), en om de klinimetrische eigenschappen ervan te bepalen. In de BrEQ werden symptomen van borstoedeem gescoord op een schaal van 0 tot 10: pijn, zwaartegevoel, zwelling, gespannen huid, roodheid, pitting, vergrote huidporiën en hardheid van de borst. We kunnen concluderen dat de BrEQ een valide en betrouwbaar meetinstrument is om borstoedeem te meten. Bijkomend werd de BrEQ gebruikt om het longitudinaal verloop van borstoedeem te bepalen na borstsparende heelkunde en radiotherapie. Daaruit is gebleken dat de prevalentie piekt na de beëindiging van de radiotherapie en vervolgens daalt in de daaropvolgende maanden. De bevindingen omtrent risicofactoren van borstoedeem zijn vaak tegenstrijdig met de literatuur, waardoor hun prognostische waarde onzeker blijft.

Dit doctoraatsproject heft bijgedragen tot de kennis over de incidentie, het tijdsverloop, de evaluatie en de prognostische factoren van arm-, schouder- en borstklachten na de behandeling van borstkanker. Inzicht in morbiditeit en het tijdsverloop is essentieel om adequate gezondheidszorg te organiseren.

​

​Diana Huis in 't Veld

• 6 March 2020
• Supervisor: Em. Prof. R. Colebunders
• Language: English
  

Willem De Ridder

• 27 February 2020
• Supervisors: Prof. J. Baets and Em. Prof. P. De Jonghe
• Language: English

Abstract

Primary muscle disorders comprise a large group of inherited and acquired diseases that affect muscle structure, metabolism, or the function of muscle ion channels. Muscle disorders presenting with slowly progressive muscle weakness constitute a group of disorders eminently suited for a multi-level pattern recognition approach, clinically as well as biologically. Given that only very few acquired muscle disorders present with slowly progressive muscular weakness, an inherited muscle disorder (IMD) is typically suspected in case of this clinical presentation. IMD constitute a clinically, genetically and histopathologically very heterogeneous group of rare diseases with more than 160 genetically distinct entities identified, rendering the diagnostic process complex. Sporadic inclusion body myositis (sIBM) constitutes a very relevant, clinically recognizable differential diagnosis in patients over 50 years of age. A few other atypically presenting acquired muscle disorders might also present slowly progressive muscle weakness, particularly idiopathic inflammatory myopathies (IIM) with anti-HMGCR antibodies and the enigmatic, supposedly very rare, putatively immune-mediated acquired myopathy, called sporadic late-onset nemaline myopathy (SLONM).

The ultimate aim of this PhD thesis was to gain insights in pathomechanisms of both inherited and acquired muscle disorders, clinically characterized by slowly progressive muscle weakness and biologically ultimately by muscle degeneration. In this thesis I particularly capitalized on ongoing revolutions in 1) genetics of IMD to identify patients with very rare IMD and to study genotype-phenotype correlations and disease mechanisms of these disorders; 2) proteomic studies of muscle, allowing an unbiased dissection of disease signatures in both acquired and inherited muscle disorders.

This resulted in: 1) the identification of patients with rare IMD due to mutations in TRIM32, BVES, VCP and other (novel) genes, and the further unraveling of pathomechanisms of these disorders; 2) unprecedented insights in the muscle proteome and disease patterns of sIBM and VCP-related myopathy. Furthermore, we highlight the unexpectedly high prevalence of patients with slowly progressing SLONM in whole exome sequencing unsolved suspected IMD patient cohorts.

This PhD thesis nicely illustrates the relevance of studying both inherited and acquired muscle disorders characterized by slowly progressive muscular weakness. We are on the verge of fascinating and exciting times in myology research and clinical myology. Diagnosing patients with rare IMD and dissecting disease mechanisms of muscle disorders will remain highly relevant with regard to rapid translation of therapies to the clinics.

​

Mirjam Schipper

• 26 February 2020
• Supervisors: Prof. J. Verbraecken and Em. Prof. W. De Backer
• Language: English

​Filip Haegdorens​

• 14 February 2020
• Supervisors: Prof. P. Van Bogaert and Prof. K. Monsieurs
• Language: English

Abstract

Deterioration of hospitalised patients is often missed, misinterpreted, and mismanaged and can eventually result in death. Rapid response systems (RRSs) provide a framework to detect and interpret in-hospital clinical deterioration, to enhance communication between clinicians, and to initiate a response in a timely manner. The main goal of RRSs is to prevent progressing patient deterioration and subsequently to reduce preventable serious adverse events improving the quality of care. A considerable body of research exists studying different aspects and types of RRSs. However, the quality of evidence in relation to patient outcomes is poor and there is no consensus on what the most effective strategy is to prevent serious adverse events. The general aim of this doctoral study is to investigate the effect of a rapid response system on patient outcomes using an evidence-based afferent limb strategy while ensuring an adequate and timely medical response by existing hospital resources. Furthermore, we studied the predictive performance of the national early warning score (NEWS), which is a track-and-trigger system to detect patient deterioration using vital signs. Because of the importance of adequate staffing levels for patient surveillance, we additionally investigated which nurse staffing levels are needed to provide safe care and to minimise patient’s unexpected death.

We defined new outcome measures, more sensitive to care processes including nursing practice, to be used in research concerning the deteriorating patient on the general ward. We confirmed an association between higher adherence to a nurse observation protocol and lower patient unexpected death and mortality after cardiopulmonary arrest or unplanned intensive care admission adjusted for patient comorbidity and age. Furthermore, we have shown that an RRS improves nurses’ performance in observing patients without increasing the observation frequency in stable patients. We showed that our intervention increased the mean number of vital signs registered per observation. In an external validation study, we calculated the predictive performance of the NEWS and confirmed that it shows acceptable performance to predict unexpected death, cardiac arrest with CPR and unplanned ICU admission. However, the NEWS had a relatively high proportion of false positive scores. This implies that clinicians should be aware of the limitations of this scoring system to prevent increased workload associated with false positives. Lastly, we found an association between higher nurse staffing levels and lower patient mortality controlling for important confounders. We confirmed the relation between a higher proportion of bachelor’s degree nurses and patient mortality.

​

Ine Wouters​

• 12 February 2020
• Supervisors: Prof. H. Theeten, Prof. P. Van Damme and Prof. P. Beutels
• Language: English

Abstract

Streptococcus pneumoniae usually resides as a commensal in the human nasopharynx. However, asymptomatic carriage may evolve to pneumococcal disease when this micro-organism migrates from the nasopharynx to other mucosal tissues or sterile sites. The consequence may be a mucosal pneumococcal disease such as acute otitis media (AOM) or invasive pneumococcal diseases (IPDs) such as bacteraemia or meningitis. The primary virulence factor of the pneumococcus is its polysaccharide capsule, which also determines the serotype. More than ninety-five serotypes exist and they vary in their capacity to colonise, to invade, and to activate the host immune system.

Currently, a 10-valent (PCV10) and a 13-valent (PCV13) pneumococcal conjugate vaccine are widely implemented in national immunisation programmes to prevent pneumococcal diseases. Belgium implemented PCV13 in its paediatric pneumococcal vaccination programme in 2011, but it was replaced by PCV10 in 2015-2016.

With the current research we aimed to gain insight into the impact of the PCV13-to-PCV10 change in Belgium, since concerns had raised regarding the three serotypes that were no longer covered (3, 6A, 19A). The overall objective is to clearly monitor the carriage of Streptococcus pneumoniae in Belgian children between six and thirty months of age. This was accomplished over a three year period, during and immediately after the change in the vaccination programme (2016-2018). We evaluated carriage prevalence, carriage density, serotype distribution, and antimicrobial susceptibility of Streptococcus pneumoniae. Furthermore, risk factors for pneumococcal carriage were evaluated. Children are the major pneumococcal reservoir and source of transmission. Therefore, the studied population included children, either in day-care centres or visiting their physician for AOM as children in these settings are reported to have a high pneumococcal carriage prevalence.

A significant increase in the carriage prevalence of serotype 19A was identified in the current research as the PCV10-vaccinated population enlarged. Furthermore, the calculated invasive disease potential for this serotype was high. Additionally, the carriage prevalence of serotype 6C increased, indicating the absence of PCV10-induced cross-protection. These results contributed to policy making, since another change in the vaccination programme was established in July-September 2019; from PCV10 back to PCV13. The current carriage monitoring will be continued, and hence this latest vaccination programme change will be evaluated from its implementation onwards. The obtained results will contribute to the concept of large-scale and long-term carriage monitoring and they will be valuable with an eye towards the introduction of the higher-valent PCV15/20.

Abstract in Dutch
Streptococcus pneumoniae is gewoonlijk als commensaal aanwezig in de humane neus-keelholte. Wanneer de pneumokok migreert van de neus-keelholte naar andere mucosale weefsels of steriele sites kan het echter zijn dat asymptomatisch dragerschap overgaat naar pneumokokkenziekte. Deze kan mucosaal zijn, zoals een acute middenoorontsteking, (AMO) maar ook invasief, zoals een bacteriëmie of hersenvliesontsteking. De voornaamste virulentiefactor van de pneumokok is het polysaccharidekapsel, dat ook het serotype bepaalt. Meer dan vijfennegentig serotypes bestaan, met een grote variatie in de mate waarin ze koloniseren, invasief zijn, en het immuunsysteem van de gastheer activeren.

Om pneumokokkenziekten te voorkomen zijn momenteel een 10-valent (PCV10) en een 13-valent (PCV13) geconjugeerd pneumokokkenvaccin wereldwijd geïmplementeerd in nationale immunisatieprogramma’s. België implementeerde PCV13 in 2011, maar in 2015-2016 werd het vervangen door PCV10.

Met het huidige onderzoek willen we inzicht verwerven in de impact van de PCV13-naar-PCV10 wijziging in België, vermits de drie serotypes (3, 6A, 19A) die niet in PCV10 (en wel in PCV13) vervat zijn mogelijks weer zouden opduiken. Het doel van dit onderzoek is het opvolgen van het pneumokokkendragerschap in Belgische kinderen tussen zes en dertig maanden oud. Dit gebeurde tijdens en onmiddellijk na de wijziging in het vaccinatieprogramma, over een periode van drie jaar (2016-2018). We evalueerden dragerschapsprevalentie, dragerschapsdensiteit, serotypedistributie, en antimicrobiële gevoeligheid van Streptococcus pneumoniae. Ook werden risicofactoren van pneumokokkendragerschap bepaald. Kinderen zijn het voornaamste reservoir en de transmissiebron van pneumokokken. De bestudeerde populatie omvat dan ook kinderen, ofwel in kinderdagverblijven ofwel op consultative bij hun arts voor AMO, aangezien deze kindpopulaties frequent pneumokokken dragen.

Een significante stijging in de dragerschapsprevalentie van serotype 19A werd geïdentificeerd naarmate de populatie met PCV10-gevaccineerde kinderen groter werd. Het berekende invasieve ziektepotentieel van dit serotype was hoog. Bovendien nam ook de dragerschapsprevalentie van serotype 6C toe, duidend op de afwezigheid van door PCV10 geïnduceerde kruisbescherming.  Deze resultaten droegen bij aan de beleidsvorming, aangezien opnieuw een wijziging in het vaccinatieprogramma gerealiseerd werd in juli-september 2019; van PCV10 weer naar PCV13. Dankzij de verderzetting van de huidige dragerschapsmonitoring, zal deze meest recente wijziging van bij de implementatie worden opgevolgd. De bekomen resultaten zullen bijdragen aan het concept van langetermijnopvolging en zullen waardevol zijn met het oog op de implementatie van de hoger-valente vaccins PCV15/20.

​

Bert Van den Bogerd​

• 27 January 2020
• Supervisors: Prof. K. Koppen, Prof. S. Ní Dhubhghaill and Prof. N. Zakaria
• Language: English

Abstract

The corneal endothelium is the most inner cell layer of the human cornea, which is the transparent window of the eye. It functions as a leaky barrier to facilitate to exchange of nutrients and water to the avascular cornea. It is a monolayer of hexagonal cells with the foremost task to maintain the cornea’s specific hydration status and thus concomitant transparency. However, they do not possess the proper machinery for tissue regeneration. That is why the absolute number of cells only decreases throughout life. When the process of inevitable cells loss is aggravated by disease or (surgical) trauma, the cornea will inadvertently swell and lose its transparency, which leads to visual impairment and blindness. If left untreated, this results in the formation of epithelial bullae, blisters on the front side of the cornea, which cause excruciating pain for the patient on top of visual impairment.

At this moment, such patients can only be helped through the transplantation of a donor endothelium from a cadaveric cornea. Despite good clinical outcomes, the amount of available donor corneas does not meet the tissue demand. That is why I explored the cultivation of human corneal endothelial cells on different substrates to develop an ex vivo grown corneal endothelium. In this way, the global donor shortage could be alleviated by providing a therapy to multiple patients with one donor cornea.

In this thesis, three different substrates were tested for their propensity to act as a cell scaffold for corneal endothelial culture and transplantation. The first two, the human anterior lens capsule and a collagen fish scale derived scaffold, were biologically derived, but were not appropriate for the proposed application. On the one side, the anterior lens capsule displayed good cytocompatibility, but had a rather limited diameter and was still dependent on a donor supply. On the other side, the fish scale scaffold displayed an extensive surface topography which hampered monolayer formation. That is why we have investigated a third scaffold, namely a synthetic ultrathin scaffold that was developed in collaboration with UGent, composed of a poly-(D,L)-lactic acid base and a gelatin coating. Initial experiments show optimal physicochemical properties and a biological proof-of-concept to grow immortalized and primary corneal endothelial cells. In the future, this novel composite scaffold will further be investigated in an ex vivo model of corneal endothelial transplantation before being tested in a rabbit model of corneal endothelial keratoplasty.

Het corneale endotheel is de binnenste cellaag van het menselijke hoornvlies, ofwel cornea genoemd. Dit is een enkele cellaag met als belangrijkste functie de transparentie van het hoornvlies te garanderen door zijn hydratatiestatus op een specifiek niveau te houden. Corneale endotheelcellen zijn daarom heel belangrijk, maar ironisch genoeg bezitten zij niet de capaciteit om zichzelf te regenereren, zodat het absolute aantal cellen in het hoornvlies alleen maar daalt vanaf de geboorte. Wanneer dit proces wordt versneld door complicaties tijdens oogoperaties of door congenitale aandoeningen, zal het hoornvlies onherroepelijk opzwellen en zijn transparantie verliezen. Dit leidt tot visuele beperking en blindheid op lange termijn. Bovendien zorgt dit oedeem voor het ontstaan van kleine blaren op de voorkant van het hoornvlies die enorm pijnlijk zijn voor de patiënt.

Momenteel kunnen deze patiënten enkel geholpen worden door een nieuw corneaal endotheel te implanteren, afkomstig van een donorhoornvlies van een overleden patiënt. Ondanks dat deze techniek goed werkt, is het aantal donorhoornvliezen wereldwijd te laag om alle patiënten in nood te helpen. Dat is waarom in deze thesis gezocht werd naar nieuwe celdragers om zo meerdere endotheelcellagen te maken en dus meerdere patiënten te kunnen helpen met slechts één donorhoornvlies.

In deze thesis werden drie verschillende kandidaat-celdragers onderzocht of zij geschikt waren voor de kweek en transplantatie van corneale endotheelcellen. De eerste twee exemplaren waren biologische membranen, namelijk het anterieure lenskapsel en een collageen membraan afgeleid van visschubben. Aan de ene kant bleek het lenskapsel, ondanks goede celcompatibiliteit, te klein voor de vertaling naar een klinische toepassing. Aan de andere kant was de oppervlaktestructuur van het collageen membraan afgeleid van visschubben te uitgesproken en verhinderde zo de groei van endotheelcellen. Om deze limieten te overkomen hebben we, in samenwerking met de UGent, een derde membraan ontwikkeld en onderzocht. Deze ultradunne, synthetische celdrager is een combinatie van een polymelkzuur membraan met daarbovenop een gelatine coating. Uit de eerste experimenten kunnen we afleiden dat dit membraan optimale fysicochemische eigenschappen bezit. Verder is het ook aangetoond dat het mogelijk is om hierop geïmmortaliseerde en primaire endotheelcellen te groeien met het correcte fenotype. In de toekomst zal deze celdrager verder getest worden in een ex vivo transplantatiemodel om later getest te worden in een konijnmodel voor corneale endotheliale transplantatie.

​

Leen Van den Steen​

• 22 January 2020
• Supervisors: Prof. M. De Bodt and Prof. G. Van Nuffelen
• Language: English

Livia De Picker

• 14 January 2020
• Supervisors: Prof B. Sabbe and Prof M. Morrens
• Language: English