Farmaceutische, Biomedische en Diergeneeskundige Wetenschappen

Rokaya Abdel-Naiem Ahmad

• 22 april 2026, 10u - 12u
• Promotiezaal, Q.002 (CDE)
• Promotor: Guy Caljon

Abstract (Engels)

Visceral leishmaniasis (VL), caused by Leishmania parasites, is one of the most neglected tropical diseases, endemic in nearly 90 countries worldwide. Control and elimination programs rely mainly on chemotherapeutic agents, as no vaccine is available. Antileishmanial drug discovery has witnessed significant progress over the last two decades, empowered by advanced functional genomic technologies. However, the high attrition rate of compounds toward clinical development and the limited understanding of Leishmania cell biology emphasize the need to explore new target-validated and mechanistically informed antileishmanial leads. To meet the "Know your Target" principle of drug discovery, we engineered Leishmania lines to investigate the mode of action of new antileishmanial compounds. In Leishmania, like any eukaryotic cell, spatiotemporal distribution of molecules across subcellular organelles is coordinated by endosomal trafficking, while the shuttling of molecules between the cytoplasm and nucleus relies on active nucleocytoplasmic transport mechanisms. This central role of intracellular trafficking pathways provides a mechanistic framework to identify and validate druggable processes.

First, through elaborate mode-of-action studies of antileishmanial aminopyrazoles, we discovered that disrupting the assembly of endosomes is a druggable pathway. Mut-Seq and CRISPR-Cas9 gene editing have independently confirmed an association between aminopyrazole resistance and multiple independent heterozygous mutations in LINF_180011100, encoding a putative endosomal FYVE Zn-finger protein. Next, genetic fusion with an N-terminal green fluorescent protein tag and partial colocalization with a C-terminal mCherry-tagged small GTPase Rab5 demonstrated that the functional protein primarily localizes in endocytic vesicles. In situ target engagement assays confirmed a selective effect of aminopyrazoles and its abrogation by introducing a resistance-conferring mutation. Furthermore, a direct interaction between the aminopyrazole lead and the recombinantly produced LINF_180011100 FYVE Zn-finger domain was demonstrated through a biophysical assay.

Our second initiative was to visualize and target nucleocytoplasmic protein transport, which is tightly coordinated by nuclear pore complexes, transport receptors, and the Ran GTPase. We engineered L. infantum to express mCherry fused to a nuclear localization signal, creating a cell-based system to visualize perturbations in nuclear protein transport. Confocal fluorescence microscopy confirmed a nuclear mCherry signal, and a dose-dependent inhibition of nuclear sequestration using the importin-β inhibitor importazole resulting in parasitic cell death. Other lead compounds with different modes of action (MoA) exerted antiparasitic activity independent of nucleocytoplasmic transport impairment, which confirms the assay selectivity.

Collectively, our transgenic lines validate the mode of action of aminopyrazole and importazole and provide valuable tools to study intracellular molecule trafficking in Leishmania and support target-driven drug discovery initiatives.

Leonardo Ricciardi

• 16 maart 2026, 10u30 - 12u30
• Promotiezaal, Q.002 (CDE)
• Promotoren: Marleen Verhoye, Peter Ponsaerts

Abstract (Engels)

Multiple sclerosis (MS) is an autoimmune neurodegenerative disease of the central nervous system (CNS) with complex and heterogeneous pathology. Its pathophysiological mechanisms remain incompletely understood, limiting the development of curative therapies. Current treatments are primarily disease-modifying approaches that target inflammatory and immunomodulatory pathways, but they do not reverse myelin loss or axonal degeneration. Similarly, available preclinical models cannot fully replicate MS complexity. To address these limitations, the PMSMatTrain consortium was established with a particular focus on progressive MS (PMS), aiming to develop and validate a biomaterial-based device for local delivery of selected therapeutics to cortical PMS lesions in rodents.

The first experimental part of the thesis investigates ‘A Proliferation Inducing Ligand, (APRIL) as a potential CNS therapeutic on the well-established cuprizone (CPZ) model of inflammation and demyelination. APRIL, a member of the tumour necrosis factor (TNF) superfamily, has been implicated in immune homeostasis and neuronal survival in the CNS, but its therapeutic potential in acute neuroinflammatory and neurodegenerative settings has only partially explored. Using adeno-associated virus (AAV)-mediated gene delivery, APRIL was expressed in cortical neurons, and its effects were assessed in CPZ-treated mice via in vivo MRI combined with post-mortem immunohistochemistry (IHC), transcriptomics, and proteomics. This work showed that APRIL secretion can counteract microglial recruitment and demyelination, particularly in the corpus callosum. The integrated transcriptome–proteome analysis demonstrated a positive influence in the cortical area as well, and further identified candidate pathways that help clarify APRIL’s mode of action and support its therapeutic potential in acute neuroinflammatory conditions of the CNS.

In the second experimental part, the PMSMatTrain-developed transcranial delivery device was validated in vivo as a minimally invasive approach to deliver small molecules into the cortex. This system, placed subcutaneously in contact with the skull, combines a silicone dome and semipermeable membrane with specific hyaluronic acid-based hydrogels to enable time-controlled administration through the intact skull. Its efficacy was validated in a proof-of-concept study, using manganese chloride (MnCl₂) as the delivery molecule, and Manganese Enhanced MRI (MEMRI) for the non-invasive monitoring of its cerebral distribution, confirming localised and temporally controlled delivery.

Together, these studies evaluate two complementary research directions that, converging towards the same goal, provide a basis for future strategies aimed at targeted, non-invasive treatment of CNS lesions in MS and potentially other disorders such as stroke and spinal cord injury.

Margot Merlot

• 22 januari 2026, 16u - 18u
• Auditorium O1 (CDE)
• Promotoren: Guy Caljon, Louis Maes

Abstract (Engels)

Coccidiosis in chickens and turkeys is caused by various closely related Eimeria species. The infection is transmitted through the fecal-oral route and may lead to large outbreaks that are difficult to mitigate, hence leading to considerable economic losses. The current standard in-feed use of anticoccidials suffers from disadvantages such as increasing drug-resistance, residues in food for human consumption, and legislative pressure to reduce antimicrobial use. The alternative control method is based on the use of multivalent (attenuated) vaccines for which the EU-regulatory authorities require stringent quality criteria for species composition and viability, overall immunogenicity, and vaccine stability. Unfortunately, these data are currently only obtained in expensive and time-consuming in vivo immunization and challenge experiments. In an attempt to overcome the need for these in vivo experiments, this thesis focused on the development of novel in vitro laboratory methodologies by using a combination of flow cytometry and molecular methods for oocyst speciation and viability assessment to better define vaccine composition and batch release characteristics.

To enable quantitation of species-specific viability of oocysts in a multivalent vaccine, permeabilization of the notoriously impermeable oocyst wall was required, which was achieved by developing a detergent-enhanced oocyst viability staining technique. As oocysts of poultry Eimeria species are genetically and morphologically very similar, hereby complicating straightforward species identification, flow cytometric sorting in combination with innovative digital PCR technology using Sequence Characterized Amplified Region (SCAR) primers was implemented. Species quantitation was further refined by applying correction factors that account for DNA extraction efficiency, PCR efficiency and SCAR copy numbers in chicken and turkey Eimeria species. The resulting assay was extensively validated for its intended use as a batch release test and was shown to be applicable across multiple stages of vaccine production, including shelf-life determination and vaccine formulation optimization.

In summary, the PhD thesis describes the development and validation of a novel in vitro laboratory method to quickly determine the species-specific volumetric viability during vaccine development and in the final multivalent coccidiosis vaccine product, providing a novel way to perform batch release testing without the need of animal testing. A provisional patent application of the developed technique has been filed (No. PCT/US2025/032408).

Elizabeth Tabitha Abbew

• 8 januari 2026, 16u - 18u
• Aula Janssens (ITG)
• Promotoren: Leen Rigouts, Lut Lynen, Dorcas Obiry-Yeboah 

Abstract (Engels)

Nontuberculous mycobacteria (NTM) are increasingly detected in tuberculosis (TB)-endemic regions, yet their clinical significance remains poorly defined. In sub-Saharan Africa (SSA), limited diagnostic capacity and absence of guidelines contribute to uncertainty in patient management.

This PhD research combined (i) a systematic scoping review of NTM in SSA, (ii) a retrospective laboratory analysis of 2,492 sputum samples in Ghana (2012–2021), (iii) a retrospective cohort of 380 MDR/RR-TB patients in Ghana (2018–2021), and (iv) three prospective cohort studies involving 9,981 symptomatic individuals in Ghana, Nigeria, and Niger. Standard mycobacterial culture, MPT64 antigen testing, line probe assays, and sequencing were used for species identification. Clinical and radiological data were analysed against international ATS/IDSA/ERS/ESCMID criteria for NTM pulmonary disease (NTM-PD).

The scoping review highlighted major gaps: most SSA studies did not apply international diagnostic criteria, species-level identification was rare, and MPT64 antigen misclassified Mycobacterium tuberculosis complex (MTBc) as NTM.

In Ghana, retrospective laboratory analysis showed 33.7% culture positivity. Initially, 30.6% were presumed NTM, but only 53 isolates (23.6%) were confirmed after molecular speciation, reducing the prevalence to 2%. M. intracellulare (66%) predominated, while 18 MTBc isolates, including M. africanum, were misclassified as NTM by MPT64. Four patients fulfilled NTM-PD criteria, all previously treated as RR-TB.

Among 380 MDR/RR-TB patients, 7.1% had NTM isolated, mainly M. intracellulare and M. fortuitum. Treatment success was 67.9%, higher with all-oral bedaquiline regimens (71.4%) compared to injectable-containing regimens (60.3%). HIV was associated with unfavourable outcomes (aOR 1.80, 95% CI 1.05–3.11), while NTM isolation itself was not. Geographic variation showed higher odds of NTM isolation in Eastern (aOR 15.68) and Brong Ahafo regions (aOR 4.74).

In the prospective cohorts, 99/938 (10.6%) had NTM isolated. Predominant species were M. intracellulare (34.3%), M. fortuitum (16.2%), and M. abscessus (10.1%). Among patients with ≥2 sputum samples, 15 (30.6%) met NTM-PD criteria, with 20% mortality. Unique isolates such as M. palustre were detected only by sequencing, reflecting diagnostic limitations of commercial assays.

This thesis demonstrates that although NTM are frequently isolated among presumed TB patients in West Africa, their presence did not adversely affect MDR/RR-TB treatment outcomes in Ghana, while their clinical significance remains challenging to determine due to limited repeated culture data from SSA. These findings underscore the need to strengthen laboratory capacity for species-level identification, integrate molecular diagnostics into routine algorithms, and develop regional clinical guidelines for the diagnosis and management of NTM-PD, while systematically excluding TB