Angela Sisto

• 3 februari 2025, 16u - 18u
• Promotiezaal, Q.002 (CDE)
• Promotor: Vincent Timmerman

Abstract (Engels)

Autophagy is a vital cellular process that recycles damaged organelles and protein aggregates, maintaining cellular health in peripheral neurons and muscle fibers. Triggered by nutrient deprivation or stress, autophagy relies on molecular chaperones and specialized receptors to identify and transport damaged components (cargo) to autophagosomes. These vesicles then fuse with lysosomes, where the cargo is degraded and recycled. Impairments in this pathway contribute to the pathogenesis of several diseases.

This thesis explores the genetic and molecular mechanisms underlying autophagy dysfunction in inherited peripheral neuropathies and congenital disorders of the skeletal and cardiac muscle. Mutations in small heat shock proteins HSPB1 and HSPB8 are major causes of Charcot-Marie-Tooth neuropathies (CMT type 2) and distal hereditary motor neuropathies (dHMN). These mutations disrupt autophagy, leading to protein aggregation and cellular dysfunction.

In particular, the HSPB1 P182L mutation exerts a toxic gain-of-function on the autophagy receptor SQSTM1/p62, reducing its oligomerization and mobility upon autophagy stimulation. This results in decreased autophagosome formation and contributes to protein stress and neuronal damage in CMT2F models. Similarly, the HSPB8 K141N mutation reduces autophagosome formation, pointing to a common pathogenic mechanism across these mutations.

Using a cellular model carrying the HSPB8 K141N mutation and fluorescent autophagy markers, a phenotypic drug screen identified novel autophagy inducers capable of rescuing autophagy deficits. Validation in patient-derived motor neurons, differentiated from induced pluripotent stem cells carrying HSPB1 and HSPB8 mutations, showed significant improvements in neuronal health upon treatment.

These findings highlight the pathological overlap between motor neuron and muscle diseases and identify key steps in the autophagy pathway disrupted by HSPB mutations. By uncovering novel molecular targets and pharmacological modulators. Furthermore, this work provides a foundation for developing therapies to restore autophagy and mitigate neurodegeneration in CMT and other autophagy-related diseases.

Souleymane Hassane Harouna

• 9 januari 2025, 16u - 18u
• Aula Janssens (ITG)
• Promotoren: Leen Rigouts, Bouke de Jong

Abstract (Engels)

Tuberculosis (TB) is a contagious disease caused by the Mycobacterium tuberculosis complex (MTBc) posing a global health challenge, particularly with drug-resistant TB (DR-TB) detection and treatment. Indeed, despite global efforts, only about 43% of DR-TB cases are diagnosed and treated, with a 68% treatment success rate for the World Health Organization (WHO) 2021 cohort. This thesis aimed to enhance the diagnosis and management of multidrug-resistant TB (MDR-TB) in Guinea by testing novel diagnostic approaches and improving therapeutic strategies. To achieve our objectives, we conducted two diagnostic studies and to therapeutic studies Chapter II explored face mask sampling (FMS) as a minimally invasive method for pulmonary TB diagnosis among symptomatic patients. FMS results, compared to sputum samples analyzed by the Xpert MTB/RIF and Xpert MTB/RIF Ultra (Xpert Classic and Xpert Ultra), showed moderate agreement (kappa value of 0.47), with overall low sensitivity (48.1%) but high specificity (95.7%). While Xpert Ultra yielded higher sensitivity than Xpert Classic (60.2% vs 38.0%), Xpert Classic had superior specificity (100% vs 90.6%).

Following these mitigated results, we explored in Chapter III tongue swabbing (TS) with Xpert Ultra and in-house swab IS6110-qPCR as another minimally invasive diagnostic approach. In a prospective study, single TS showed lower sensitivity (88.5%) than sputum, although pooling swabs improved sensitivity to 93.8%. Furthermore, bacillary load of positive TS samples was not affected by the sampling order, and "MTB low" results were predominant for both single and pooled series of TS. Sample adequacy control via qPCR assay detected human mitochondrial DNA and thus confirmed the oral source of TS samples. In a retrospective analysis, the agreement between the in-house swab IS6110-qPCR and sputum-Xpert was high (k=0.91 for Xpert Classic and k=0.86 for Ultra).

Chapter IV  addressed MDR-TB treatment with a longer regimen (lasting 18-20 months) and a shorter regimen (9-11 months) outcomes in a post-Ebola setting. Results showed that patients on a shorter regimen were more likely to achieve successful treatment outcome (74.0% vs. 58.7%) and less likely to experience adverse events (loss to follow-up, death or treatment failure), with a two-fold increase in risk for those on a longer regimen (aOR: 2.5).

In Chapter V, community supported self-administered TB treatment (CS-SAT) and active TB screening among household contacts were evaluated. CS-SAT achieved a 94.7% favorable outcome, exceeding the national target of 90%. Active household screening enabled the referral of 376 children for isoniazid preventive therapy and the detection of five pulmonary confirmed TB among household contacts.

Our studies contributed to enhancing TB diagnosis and treatment. Findings suggest that further diagnostic studies using the new sampling approches are need for pulmonary TB diagnosis. Children and paucibacillary group patients should be prioritized for such studies. For MDR-TB treatment, shorter regimens should be prioritized. Additionally, enhancing the technical capacity of laboratories and medical services is crucial to ensure improved outcomes. Finally, community-supported TB treatment should be tailored to specific contexts and patient needs, to guarantee the continuity of the patient treatment.