@phdthesis{Reuter2023, author = {Reuter, Christian Steffen}, title = {Development of a tissue-engineered primary human skin infection model to study the pathogenesis of tsetse fly-transmitted African trypanosomes in mammalian skin}, doi = {10.25972/OPUS-25114}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-251147}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Many arthropods such as mosquitoes, ticks, bugs, and flies are vectors for the transmission of pathogenic parasites, bacteria, and viruses. Among these, the unicellular parasite Trypanosoma brucei (T. brucei) causes human and animal African trypanosomiases and is transmitted to the vertebrate host by the tsetse fly. In the fly, the parasite goes through a complex developmental cycle in the alimentary tract and salivary glands ending with the cellular differentiation into the metacyclic life cycle stage. An infection in the mammalian host begins when the fly takes a bloodmeal, thereby depositing the metacyclic form into the dermal skin layer. Within the dermis, the cell cycle-arrested metacyclic forms are activated, re-enter the cell cycle, and differentiate into proliferative trypanosomes, prior to dissemination throughout the host. Although T. brucei has been studied for decades, very little is known about the early events in the skin prior to systemic dissemination. The precise timing and the mechanisms controlling differentiation of the parasite in the skin continue to be elusive, as does the characterization of the proliferative skin-residing trypanosomes. Understanding the first steps of an infection is crucial for developing novel strategies to prevent disease establishment and its progression. A major shortcoming in the study of human African trypanosomiasis is the lack of suitable infection models that authentically mimic disease progression. In addition, the production of infectious metacyclic parasites requires tsetse flies, which are challenging to keep. Thus, although animal models - typically murine - have produced many insights into the pathogenicity of trypanosomes in the mammalian host, they were usually infected by needle injection into the peritoneal cavity or tail vein, bypassing the skin as the first entry point. Furthermore, animal models are not always predictive for the infection outcome in human patients. In addition, the relatively small number of metacyclic parasites deposited by the tsetse flies makes them difficult to trace, isolate, and study in animal hosts. The focus of this thesis was to develop and validate a reconstructed human skin equivalent as an infection model to study the development of naturally-transmitted metacyclic parasites of T. brucei in mammalian skin. The first part of this work describes the development and characterization of a primary human skin equivalent with improved mechanical properties. To achieve this, a computer-assisted compression system was designed and established. This system allowed the improvement of the mechanical stability of twelve collagen-based dermal equivalents in parallel through plastic compression, as evaluated by rheology. The improved dermal equivalents provided the basis for the generation of the skin equivalents and reduced their contraction and weight loss during tissue formation, achieving a high degree of standardization and reproducibility. The skin equivalents were characterized using immunohistochemical and histological techniques and recapitulated key anatomical, cellular, and functional aspects of native human skin. Furthermore, their cellular heterogeneity was examined using single-cell RNA sequencing - an approach which led to the identification of a remarkable repertoire of extracellular matrix-associated genes expressed by different cell subpopulations in the artificial skin. In addition, experimental conditions were established to allow tsetse flies to naturally infect the skin equivalents with trypanosomes. In the second part of the project, the development of the trypanosomes in the artificial skin was investigated in detail. This included the establishment of methods to successfully isolate skin-dwelling trypanosomes to determine their protein synthesis rate, cell cycle and metabolic status, morphology, and transcriptome. Microscopy techniques to study trypanosome motility and migration in the skin were also optimized. Upon deposition in the artificial skin by feeding tsetse, the metacyclic parasites were rapidly activated and established a proliferative population within one day. This process was accompanied by: (I) reactivation of protein synthesis; (II) re-entry into the cell cycle; (III) change in morphology; (IV) increased motility. Furthermore, these observations were linked to potentially underlying developmental mechanisms by applying single-cell parasite RNA sequencing at five different timepoints post-infection. After the initial proliferative phase, the tsetse-transmitted trypanosomes appeared to enter a reversible quiescence program in the skin. These quiescent skin-residing trypanosomes were characterized by very slow replication, a strongly reduced metabolism, and a transcriptome markedly different from that of the deposited metacyclic forms and the early proliferative trypanosomes. By mimicking the migration from the skin to the bloodstream, the quiescent phenotype could be reversed and the parasites returned to an active proliferating state. Given that previous work has identified the skin as an anatomical reservoir for T. brucei during disease, it is reasonable to assume that the quiescence program is an authentic facet of the parasite's behavior in an infected host. In summary, this work demonstrates that primary human skin equivalents offer a new and promising way to study vector-borne parasites under close-to-natural conditions as an alternative to animal experimentation. By choosing the natural transmission route - the bite of an infected tsetse fly - the early events of trypanosome infection have been detailed with unprecedented resolution. In addition, the evidence here for a quiescent, skin-residing trypanosome population may explain the persistence of T. brucei in the skin of aparasitemic and asymptomatic individuals. This could play an important role in maintaining an infection over long time periods.}, subject = {Trypanosoma brucei}, language = {en} } @phdthesis{Middendorf2008, author = {Middendorf, Barbara}, title = {Einfluss von Melarsoprol in der Therapie der afrikanischen Trypanosomiasis auf den Glukosemetabolismus des Menschen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28312}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {Die afrikanische Schlafkrankheit f{\"u}ht unweigerlich zum Tod wenn sie unerkannt und somit unbehandelt bleibt. Zur Therapie stehen nur sehr wenige Medikamente zur Verf{\"u}gung, wovon die meisten bereits seit mehr als 50 Jahren im Einsatz sind. Unter der Therapie treten in ca. 5-10\% der F{\"a}lle Enzephalopathien auf, die in vielen F{\"a}llen t{\"o}dlich verlaufen. Bisher ist nicht sicher, wie der dahinterstehende Pathomechanismus verl{\"a}uft. Zu dieser Frage wurden Untersuchungen des Glukosemetabolismus an Patienten im 2. Stadium der Schlafkrankheit durchgef{\"u}hrt. Es zeigte sich ein signifikanter Anstieg des durchschnittlichen Glukoseniveaus im Verlauf der Therapie. Des weiteren wurden unterschiedliche Verl{\"a}ufe von arzneimittel-induzierter Enzephalopathie klinisch beobachtet und beschrieben.}, subject = {Trypanosomiasis}, language = {de} } @phdthesis{Leyh2009, author = {Leyh, Matthias}, title = {Strukturbiologische Experimente zur Charakterisierung von Rhodesain im Komplex mit Inhibitoren im Rahmen der strukturbasierten Wirkstoffentwicklung gegen den Erreger der Schlafkrankheit}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-47919}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2009}, abstract = {Die akute Form der afrikanischen Schlafkrankheit wird durch den Parasiten Trypanosoma brucei rhodesiense verursacht und f{\"u}hrt unbehandelt zum exitus letalis. Da derzeit nur wenige, zum Teil hoch toxische Substanzen mit zunehmender Resistenzlage klinische Anwendung finden, ist die Entwicklung neuer Medikamente dringend erforderlich. Rhodesain ist eine essenzielle Cysteinprotease des Erregers und wird als potentielles Zielmolek{\"u}l f{\"u}r die intelligente Wirkstoffentwicklung gehandelt. Inhibitoren, welche dieses Molek{\"u}l im niedrigen mikromolaren Bereich inhibieren, konnten bereits vom Institut f{\"u}r Pharmazie der hiesigen Universit{\"a}t synthetisiert werden. Um die Inhibitoren hinsichtlich ihrer Selektivit{\"a}t, Affinit{\"a}t und Toxizit{\"a}t zu optimieren, ist deren r{\"o}ntgenstrukturbiologische Analyse im Komplex mit dem Zielmolek{\"u}l Rhodesain notwendig. Rhodesain wurde in den Hefezellen Pichia pastoris, welche mit dem Vektor pPICZalphaB_RhodesainDeltaCmut transfiziert wurden, exprimiert und mittels Hydrophober-Wechselwirkungs- sowie Gr{\"o}ßenausschlußschromatographie gereinigt. Nadelf{\"o}rmige Kristalle konnten mit einer Reservoirl{\"o}sung aus 1.6 M Ammoniumsulfat, 10\% 1,4-Dioxan und 0.1 M MES pH6.9 sowie bei einer Temperatur von 20°C erhalten werden. Die Kristalle wurden mit dem Inhibitor UM112C getr{\"a}nkt und an der Europ{\"a}ischen Anlage f{\"u}r Synchrotronstrahlung ESRF (Grenoble) vermessen. Das Diffraktionsbild bei einer Wellenl{\"a}nge von 0.97625 {\AA} ergab ein f{\"u}r Proteine typisches Beugungsmuster mit einer Streuung bis 3.04 {\AA}. Zur weiteren Analyse und Optimierung der Kristalle wurde das Projekt von Dipl.-Biol. Uwe Dietz im Rahmen seiner Dissertation und des Sonderforschungsbereichs SFB-630 {\"u}bernommen.}, subject = {Trypanosomiasis}, language = {de} } @phdthesis{Becker2010, author = {Becker, Friederike}, title = {Die afrikanische Schlafkrankheit in der Demokratischen Republik Kongo - Eine Analyse der Strategien ihrer Bek{\"a}mpfung durch Nationale Institutionen, die Weltgesundheitsorganisation und Nichtregierungsorganisationen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55684}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {Die Afrikanische Schlafkrankheit ist eine tropische Infektionskrankheit und geh{\"o}rt zu den vernachl{\"a}ssigten Krankheiten. Am st{\"a}rksten von Schlafkrankheit betroffen ist die Demokratische Republik Kongo. Anfang des 20. Jahrhunderts war ihre Bek{\"a}mpfung von großem Interesse f{\"u}r die Kolonialm{\"a}chte und eine wirkungsvolle Bek{\"a}mpfung konnte erreicht werden. Nach der Unabh{\"a}ngigkeit der afrikanischen Staaten kam es jedoch erneut zu Ausbr{\"u}chen. Diese Arbeit analysiert die historische Entwicklung und den aktuellen Stand der Bek{\"a}mpfung und Kontrolle der Schlafkrankheit in der DR Kongo und untersucht Charakteristiken und Aufgabenbereiche aktueller nationaler und internationaler Organisationen anhand von ver{\"o}ffentlichter Literatur, Site Visits und Experteninterviews vor Ort.}, subject = {Trypanosomiase}, language = {de} }