Thèses sur le sujet « African trypanosomiasi »
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1
Rossi, B. C. « Macrophage function in African trypanosomiasis ». Thesis, Brunel University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373784.
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2
Milligan, Paul. « Population dynamics of African trypanosomiasis ». Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306017.
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3
Bailey, Wendi. « The diagnosis of human African trypanosomiasis ». Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260319.
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4
Hublart-Sinsoillier, Marylène. « Hypogonadisme et trypanosomiase africaine ». Lille 1, 1989. http://www.theses.fr/1989LIL10127.
Texte intégralRésumé :
Parmi les éléments cliniques et biologiques caractérisant la maladie du sommeil, l'apparition d'un hypogonadisme représente un élément de grande fréquence. Notre possibilité de réaliser des explorations, par des dosages radioimmunologiques des hormones sexuelles sur un nombre significatif de malades infectes par trypanosoma brucei gambiense, a permis de mesurer l'importance du dysfonctionnement endocrinien. Par des explorations dynamiques de l'axe gonadotrope, une origine supra ou extra hypophysaire à l'hypogonadisme peut être évoquée. L'adaptation sur le modèle animal, nous a permis d'explorer dans son ensemble l'axe hypothalamo hypophyso gonadotrope du rat infesté par trypanosoma brucei brucei. Parmi les résultats originaux seront soulignés : l'effet in vivo, de l'antigène variable de surface (VSG) qui entraine une hyposécrétion de testostérone accompagnée d'une diminution de synthèse de l'hormone lutéinisante hypophysaire (LH). L'effet in vitro d'extraits parasitaires préparés en présence ou en absence d'antiprotéases qui provoquent une dissociation de la LH en ses deux sous unités libres ou une dégradation plus complète de la gonadostimuline. A la lumière de ces résultats, différentes hypothèses physiopathologéniques de l'hypogonadisme sont présentées. Sans conteste, le rôle des constituants membranaires de surface du trypanosome dans la relation hôte-parasite est mis en évidence.
5
Kashiwazaki, Yoshihito. « A new immunodiagnosis for African trypanosomiases ». Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359033.
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6
Kroubi, Maya. « Développement de formulations colloïdales antiparasitaires pour traiter la trypanosomiase africaine ». Thesis, Lille 2, 2010. http://www.theses.fr/2010LIL2S043/document.
Texte intégralRésumé :
Cette thèse porte sur le développement d’une formulation colloïdale de diminazène (DMZ) à l’aide de nanoparticules polysaccharidiques cationiques (NP+) pour le traitement de la Trypanosomiase Africaine (TA).Nous avons étudié dans un premier temps le procédé de chargement des NP+ en DMZ base. Nous avons constaté que l’ajout de phospholipides dans la matrice des NP+ est nécessaire à l’association de DMZ. La quantité de phospholipide est d’ailleurs le facteur limitant de l’indice de saturation des NP+ en DMZ. Afin de ne pas dégrader le principe actif, lors de son chargement, le procédé choisi est le « post-loading » qui correspond à un mode opératoire en conditions douces : ajout d’une solution de DMZ dans une suspension de NP+ à cœur huileux. Nos résultats montrent que cette formulation reste stable durant 6 mois à 4°C ne libérant pas de DMZ et le protégeant de l’oxydation. Dans un second temps, nous avons évalué l’efficacité thérapeutique du DMZ formulé. Les tests in vitro sur Trypanosoma brucei brucei montrent une amélioration de l’activité trypanocide du DMZ. Les tests réalisés sur un modèle aigu de TA, ont mis en évidence que la dose efficace est équivalente au DMZ libre (3 mg/kg)This thesis focuses on the development of a colloidal formulation of diminazene (DMZ) using cationic polysaccharide nanoparticles (NP+) for the treatment of African Trypanosomiasis. We first studied the process of DMZ loading in NP+. The addition of phospholipids in the matrix of the NP+ appeared to be necessary for the DMZ association. So, the amount of phospholipids is the limiting factor of the saturation index of NP+ with DMZ. To avoid the drug degradation during its formulation, we choose the \\\"post-loading\\\" technique which corresponds to a procedure with mild conditions: adding a DMZ solution in a suspension of NP+ containing an oily core. DMZ loaded into 70DGNP+ was found to be protected against oxidation and was stable for at least 6 months at 4°C. In a second step, we evaluated the therapeutic efficacy of formulated DMZ. In vitro tests on Trypanosoma brucei brucei showed an improvement of the DMZ trypanocidal activity. Tests on an acute model of Trypanosomiasis showed that the effective dose is equivalent to the free DMZ (3 mg / kg)
7
Hoste, Christian. « Elevage et trypanosomiase animale africaine ». Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37605971k.
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8
Matemba, Lucas E. « Epidemiology of human African trypanosomiasis in western Tanzania ». Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/24915.
Texte intégralRésumé :
This thesis started by reviewing the existing sleeping sickness historical records in Tanzania with the aim of exploring the evidence for the existence of Trypanosoma brucei gambiense in Tanzania. Findings from the available historical data did not provide sufficient evidence for the existence of T. b. gambiense sleeping sickness in Tanzania.The thesis further estimated under-reporting of T. b. rhodesiense in endemic areas of Tanzania using an established model. Using data from a 2000-2004 outbreak of T. b. rhodesiense in Urambo, the model predicts 46% underreporting. All unreported cases were assumed to be undetected deaths as sleeping sickness is invariable fatal if left untreated. These underreporting findings were then used to recalibrate the burden of T. b. rhodesiense (using Disability-Adjusted Life Years – DALYs), as a metric. The burden imposed to rural communities by rhodesiense sleeping sickness is high. The costs of hospitalization are very high considering the long duration of hospital stay (26 days mean hospital stay) for sleeping sickness patients. Finally the thesis investigated spatial and behavioural risk factors for T. b. rhodesiense sleeping sickness in Urambo district, through a matched case control study both at the village and within village scales. Statistically significant cluster was observed at the village level (P = 0.001). However there was no significant spatial association in an individual village’s analysis. There was an increased risk of sleeping sickness in homesteads with a previous history of the disease (P < 0.001). Presence of wild animals in the villages (P<0.001) and forest visits (P = 0.001) were also significantly associated with sleeping sickness in the district.
9
Felu, Cécile. « Characterisation of the mechanism of human serum resistance in T.b.gambiense ». Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210844.
Texte intégralRésumé :
The two human pathogenic sub-species T.b.gambiense and T.b.rhodesiense can be distinguished from the morphologically identical T.b.brucei by their ability to infect humans, enabling them to cause sleeping sickness. This is because they are resistant to lysis by the lytic factor (APOL-I) present in normal human serum (NHS). In T.b.rhodesiense resistance to this lytic factor is due to a truncated VSG gene termed SRA which blocks lysis by interacting with APOL-I in the lysosome. SRA does not exist in T.b.gambiense. The search for a similar truncated VSG gene lead to the identification of a T.b.gambiense specific glycoprotein termed TGSGP. TGSGP transfected alone into the sensitive T.b.brucei is unable to confer resistance to this sub-species. This is either due to incorrect processing of this gene is this sub-species or because TGSGP requires a partner to confer resistance.In the search for a partner, the genomic locus of TGSGP was cloned and sequenced. We found that TGSGP is linked to a truncated gene homologous to the S.cerevisiae AUT1 gene, a gene implicated in autophagy and more specifically in membrane expansion. Southern blot hybridization and PCR analysis on genomic DNA from several isolates demonstrated that this feature was a specific to T.b.gambiense. In addition, we observed a correlation between the aut1 allele size and the geographical origin of the isolate.
Since in trypanosomes lysis by NHS is due to an uncontrolled expansion of the lysosome, we speculated that the truncation of the aut1 allele could be implication in the resistance to human serum. We characterized the genomic organisation of the AUT1 locus. T.b.brucei possesses two native AUT1 alleles whilst T.b.gambiense possesses a truncated aut1 allele, as well as a native AUT1 allele. We showed that in the T.b.gambiense LiTAR isolate (aut1/AUT1), despite the presence of a wild-type allele this gene is no longer expressed at the mRNA and protein level. Our complimentary results by run-on transcription assay showed that the AUT1 region is transcribed but that the messenger is unstable. LiTAR is a functional knock-out for AUT1, but Northern blot analysis on several T.b.gambiense isolates showed that this is not a generalised T.b.gambiense characteristic.
We explored the role of AUT1 in trypanosomes by invalidation of the AUT1 gene in T.b.brucei and by the over-expression of the AUT1 and aut1 alleles in T.b.brucei. By functional analysis of AUT1 knocked-down cells we showed that AUT1 is not essential in trypanosomes. By recreating in T.b.brucei the T.b.gambiense AUT1/aut1 genotype we were able to show that the expression of the aut1 UTR down-regulated the expression of the wild-type AUT1 allele. We speculated that this may be due to a natural RNAi mechanism. Par northern blot, using probes covering the potential target region of AUT1, we detected a 50nt small RNA specific to T.b.gambiense. In addition, we showed that in a LiTAR strain in which the RNAi pathway was abolished AUT1 expression is restored.
We continued to investigate TGSGP’s role in the resistance to human serum by invalidation of TGSGP in T.b.gambiense and by expressing TGSGP in the NHS-sensitive T.b.brucei. Because T.b.gambiense cannot be cultured in vitro we established a new in vivo transfection technique and as the knock-out of TGSGP is most probably lethal, we created an inducible RNAi T.b.gambiense cell strain. These indispensable tools will be used to test whether invalidation TGSGP is sufficient to confer resistance to NHS. Many strategies were tested in order to correctly expressing TGSGP in T.b.brucei; in none of these transfectants was TGSGP correctly located in the flagellar pocket as is the case in T.b.gambiense and only partial resistance was ever obtained. In order to identify the factors in human serum that could interacts with TGSGP, we subjected NHS to affinity chromatography using TGSGP as bait. We showed that TGSGP interacts with APOA-I, a major component of HDLs.
Doctorat en sciences, Spécialisation biologie moléculaire
info:eu-repo/semantics/nonPublished
10
au, ngiles@anhb uwa edu, et Natalie Giles. « Exploitation of the Protein Tubulin For Controlling African Trypanosomiasis ». Murdoch University, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060315.191003.
Texte intégralRésumé :
This thesis presents the results of an investigation into the structural protein, tubulin, as a potential target for anti-trypanosomatid drug discovery and vaccine development. Recombinant alpha- and beta- tubulin proteins from Trypanosoma brucei rhodesiense were expressed as soluble fusion proteins in an E. coli expression system. The recombinant alpha- and beta- tubulins were used to determine the nature of binding of novel trifluralin analogues EPL-AJ 1003, 1007, 1008, 1016 and 1017. Native tubulin from rats was used to determine the extent of binding to mammalian tubulin. The results of this study clearly demonstrate two important aspects of the binding of trifluralins to tubulin. Firstly, they have specific affinity for trypanosomal tubulin compared with mammalian regardless of the chemical composition of the trifluralin analogue tested. Secondly, they have a demonstrably stronger affinity for alpha-tubulin compared with beta-tubulin. In addition, compounds 1007, 1008, 1016 and 1017 have strong binding affinities for alpha-tubulin, with limited binding affinity for mammalian tubulin, which indicates that these compounds selectively bind to trypanosomal tubulin.
The morphology of bloodstream forms of T. b. rhodesiense exposed to trifluralin analogues was studied using electron microscopy and immunofluorescence to determine the ultrastructural changes these compounds induce as a result of binding to tubulin. All compounds tested induced severe irreparable damage in T. b. rhodesiense, including perturbation of subpellicular microtubules, extensive cytoplasmic swellings, axoneme and paraflagellar rod malformation, disconfiguration around the flagellar pocket and membrane disintegration. These results suggest that the mechanism of action of these trifluralin analogues is through the disruption of polymerization of tubulin into microtubules as a result of binding to alpha-tubulin.
The potential for recombinant trypanosomal tubulins to be used as vaccine candidates was assessed by monitoring parasitaemia and length of survival of mice immunised with the proteins and challenged with a lethal infection of T. b. rhodesiense. Although all the mice vaccinated with recombinant tubulin developed a patent parasitaemia and did not survive, they were partially protected because their patency period and length of survival were significantly greater than the control groups. Furthermore, plasma collected from mice immunised with recombinant trypanosomal tubulin contained antibodies that recognized tubulin in a soluble extraction from T. b. rhodesiense. The results of this thesis confirm the potential for the structural protein, tubulin, to be used as a target for anti-trypanosomatid drug discovery and vaccine development.
11
Eltayeb, Ragaa Abdelkhalig. « Immunopathology and signalling molecules involved during experimental African trypanosomiasis / ». Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4382-6/.
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12
Giles, Natalie Lydia. « Exploitation of the protein tubulin for controlling African trypanosomiasis / ». Access via Murdoch University Digital Theses Project, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060315.191003.
Texte intégral
13
Acup, Christine Amongi. « Epidemiology and control of human African trypanosomiasis in Uganda ». Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/16246.
Texte intégralRésumé :
Poverty and disease are bound together in rural communities of sub-Saharan Africa (SSA) exacerbated by weak social services and conflict. The infectious disease burden in SSA combines the neglected tropical diseases (NTDs) and the 'big three' (malaria, HIV/AIDS and tuberculosis), so-called because they attract more global attention and hence funding. NTDs include human African trypanosomiasis (HAT or sleeping sickness), first noticed by the outside world during the slave trade era and later in the 2-th century by widespread epidemics of disease across the tsetse fly belt. HAT describes two diseases: i) Gambian HAT caused by Trypanosoma brucei gambiense is characteristically chronic with an infectious period lasting up to three years and ii) Rhodesian HAT caused by T.b. rhodesiense is an acute disease, killing its victim within weeks of infection. The two diseases are frequently considered together as both are transmitted by tsetse flies, the parasites are morphologically indistinguishable and the associated diseases are both fatal if left untreated. However, the two diseases are clinical, epidemiologically and geographical distinct, each requiring different control strategies. Under field conditions, where microscopy is the basic diagnostic tool, differentiation is simply by geographical location of the patient; the Great Rift Valley separates the Gambian disease present in West and Central Africa, from East and southern Africa's Rhodesian disease. Control strategies are also distinct; while the Belgian and French colonial strategies to control the disease were patient-centred, the British colonial powers in East Africa were motivated by the effect of tsetse borne diseases on animal health. Towards the end of the colonial ear, both types of disease were heading for elimination but during the immediate post-colonial era in the 1960s, political instability compromised the rigid HAT control programs that had been put in place. For zoonotic Rhodesian sleeping sickness, complex tsetse control programmes proved difficult to maintain and to justify economically; for Gambian sleeping sickness the generalised breakdown of medical services allowed the disease to return, sometimes to devastating levels. The millennium development goals (MDGs) set out in 2000, highlighted specific challenges and opportunities for national and global development. HAT impacts national health goals of national development plans and MDGs and impedes rural development of SSA. NTDs were not addressed directly by MDGs but the World Health Organization (WHO) has reaffirmed its commitment not only to control of HAT but also to eliminate it as a public health problem by 2020. Currently there are 25 countries reporting HAT to WHO, and while the overall prevalence of HAT across Africa continues to fall, epidemics have been recorded, particularly from central Africa, South Sudan and Uganda. Uganda is uniquely, the only country affected by both T.b. gambiense and T.b. rhodesiense and until the present study, there was no evidence to suggest that the two parasite species co-existed in Uganda. The development of a new control paradigm for T.b. rhodesiese in South East Uganda has lowered the incidence of human infections and, more importantly, halted the northerly spread of this parasite. However, recurring epidemics in several established and new disease foci in central Uganda highlight the difficulties involved in eliminating this disease. The present study assesses past and present HAT control strategies centred on Dokolo, Kaberamaido and Soroti Districts located at the centre of Uganda. These districts are highly endemic for T.b. rodesiense, they represent the region of concern for overlap with T.b. gambiense foci in central Uganda, and are the current focus of the Stamp out Sleeping sickness control initiative. The point prevalence of T. brucei s.1 in cattle reservoir from villages with (out) reported human disease located at specific distances to Otuboi, Chagwere and Ochero cattle markets, was evaluated before and six months after trypanocidal treatment, to assess the transferrable impact of zoonotic T.b. rhodesiense to the human population. Overall, the proportion of T. brucei s.1 in cattle dropped significantly from 22% at baseline to 9% six months after trypanocide treatment (P < 0.05, Chi-square + 17.92, 95% C.I. + 1.71 to 4.49). All villages located in sub-counties that received at least 80% treatment coverage had a drop in T. brucei s.1 prevalence from 30.4% (95%, C.I + 22.8 to 38.0) before treatment was done, to 12.9% (95%, C.I. + 7.4 to 18.4) six months after treatment. More specifically, impact on human infective T.b. rhodesiense was also halved. In fact only three cattle were detected with the parasite six months after treatment compared with six from those sampled as baseline. This study also utilises documented cases between 2009 and 2012 to assess the current HAT reporting system for monitoring and evaluating transmission dynamics of the disease. Using a questionnaire, capacity and preparedness of healthcare professionals to respond to disease epidemics was assessed. The point prevalence of sleeping sickness in the three districts in 2009 was determined by screening volunteers. Microscopic examinations detected trypanosomes in four volunteers (4/5311 or 0.075 %) while PCR detected significantly more infections (24, p < 0.001). Multiplex PCR showed that ten of the Trypanozoon infections were T.b. rhodesiense while nested PCR identified four infections as T.b. gamiense, indicating that the distribution of the two forms of sleeping sickness overlaps in Uganda. Second phase investigations followed up the PCR positive cases; these people were screened again, together with members of their homestead and the inhabitants of three neighbouring homes. Besides microscopy and PCR, study subjects were examined clinically for sleeping sickness and completed a questionnaire to assess community recognition of the disease. This extended screen revealed no new cases underlining the importance of stringent early screening that PCR techniques can provide. At local healthcare centres, 54% of reported sleeping sickness cases were diagnosed only at the late stage, indicating a weakness in early diagnosis and hence early reporting. Interviews with local health workers also revealed weaknesses in recognition of clinical signs and a gap in diagnostic capacity. While records at treating hospitals remain a useful indicator for targeting active foci of infection, improvement in capacity to diagnose HAT at an early stage should contribute both to rural health and disease control strategies and also towards WHO's 2020 target of elimination of HAT.
14
Giles, Natalie. « Exploitation of the protein tubulin for controlling African trypanosomiasis ». Thesis, Giles, Natalie (2005) Exploitation of the protein tubulin for controlling African trypanosomiasis. PhD thesis, Murdoch University, 2005. https://researchrepository.murdoch.edu.au/id/eprint/40/.
Texte intégralRésumé :
This thesis presents the results of an investigation into the structural protein, tubulin, as a potential target for anti-trypanosomatid drug discovery and vaccine development. Recombinant alpha- and beta- tubulin proteins from Trypanosoma brucei rhodesiense were expressed as soluble fusion proteins in an E. coli expression system. The recombinant alpha- and beta- tubulins were used to determine the nature of binding of novel trifluralin analogues EPL-AJ 1003, 1007, 1008, 1016 and 1017. Native tubulin from rats was used to determine the extent of binding to mammalian tubulin. The results of this study clearly demonstrate two important aspects of the binding of trifluralins to tubulin. Firstly, they have specific affinity for trypanosomal tubulin compared with mammalian regardless of the chemical composition of the trifluralin analogue tested. Secondly, they have a demonstrably stronger affinity for alpha-tubulin compared with beta-tubulin. In addition, compounds 1007, 1008, 1016 and 1017 have strong binding affinities for alpha-tubulin, with limited binding affinity for mammalian tubulin, which indicates that these compounds selectively bind to trypanosomal tubulin.
The morphology of bloodstream forms of T. b. rhodesiense exposed to trifluralin analogues was studied using electron microscopy and immunofluorescence to determine the ultrastructural changes these compounds induce as a result of binding to tubulin. All compounds tested induced severe irreparable damage in T. b. rhodesiense, including perturbation of subpellicular microtubules, extensive cytoplasmic swellings, axoneme and paraflagellar rod malformation, disconfiguration around the flagellar pocket and membrane disintegration. These results suggest that the mechanism of action of these trifluralin analogues is through the disruption of polymerization of tubulin into microtubules as a result of binding to alpha-tubulin.
The potential for recombinant trypanosomal tubulins to be used as vaccine candidates was assessed by monitoring parasitaemia and length of survival of mice immunised with the proteins and challenged with a lethal infection of T. b. rhodesiense. Although all the mice vaccinated with recombinant tubulin developed a patent parasitaemia and did not survive, they were partially protected because their patency period and length of survival were significantly greater than the control groups. Furthermore, plasma collected from mice immunised with recombinant trypanosomal tubulin contained antibodies that recognized tubulin in a soluble extraction from T. b. rhodesiense. The results of this thesis confirm the potential for the structural protein, tubulin, to be used as a target for anti-trypanosomatid drug discovery and vaccine development.
15
Giles, Natalie. « Exploitation of the protein tubulin for controlling African trypanosomiasis ». Giles, Natalie (2005) Exploitation of the protein tubulin for controlling African trypanosomiasis. PhD thesis, Murdoch University, 2005. http://researchrepository.murdoch.edu.au/40/.
Texte intégralRésumé :
This thesis presents the results of an investigation into the structural protein, tubulin, as a potential target for anti-trypanosomatid drug discovery and vaccine development. Recombinant alpha- and beta- tubulin proteins from Trypanosoma brucei rhodesiense were expressed as soluble fusion proteins in an E. coli expression system. The recombinant alpha- and beta- tubulins were used to determine the nature of binding of novel trifluralin analogues EPL-AJ 1003, 1007, 1008, 1016 and 1017. Native tubulin from rats was used to determine the extent of binding to mammalian tubulin. The results of this study clearly demonstrate two important aspects of the binding of trifluralins to tubulin. Firstly, they have specific affinity for trypanosomal tubulin compared with mammalian regardless of the chemical composition of the trifluralin analogue tested. Secondly, they have a demonstrably stronger affinity for alpha-tubulin compared with beta-tubulin. In addition, compounds 1007, 1008, 1016 and 1017 have strong binding affinities for alpha-tubulin, with limited binding affinity for mammalian tubulin, which indicates that these compounds selectively bind to trypanosomal tubulin.
The morphology of bloodstream forms of T. b. rhodesiense exposed to trifluralin analogues was studied using electron microscopy and immunofluorescence to determine the ultrastructural changes these compounds induce as a result of binding to tubulin. All compounds tested induced severe irreparable damage in T. b. rhodesiense, including perturbation of subpellicular microtubules, extensive cytoplasmic swellings, axoneme and paraflagellar rod malformation, disconfiguration around the flagellar pocket and membrane disintegration. These results suggest that the mechanism of action of these trifluralin analogues is through the disruption of polymerization of tubulin into microtubules as a result of binding to alpha-tubulin.
The potential for recombinant trypanosomal tubulins to be used as vaccine candidates was assessed by monitoring parasitaemia and length of survival of mice immunised with the proteins and challenged with a lethal infection of T. b. rhodesiense. Although all the mice vaccinated with recombinant tubulin developed a patent parasitaemia and did not survive, they were partially protected because their patency period and length of survival were significantly greater than the control groups. Furthermore, plasma collected from mice immunised with recombinant trypanosomal tubulin contained antibodies that recognized tubulin in a soluble extraction from T. b. rhodesiense. The results of this thesis confirm the potential for the structural protein, tubulin, to be used as a target for anti-trypanosomatid drug discovery and vaccine development.
16
Cecchi, Giuliano. « Biogeographical patterns of African trypanosomoses for improved planning and implementation of field interventions ». Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209787.
Texte intégralRésumé :
Spatially-explicit information is essential for planning and implementing interventions against vector-borne diseases. This is also true for African trypanosomoses, a group of diseases of both humans and animals caused by protozoa of the Genus Trypanosoma, and transmitted by tsetse flies (Genus Glossina).In this thesis the knowledge gaps and the requirements for an evidence-based decision making in the field of tsetse and trypanosomoses are identified, with a focus on georeferenced data and Geographic Information Systems (GIS). Datasets, tools and analyses are presented that aim to fill some of the identified knowledge gaps.
For the human form of the disease, also known as sleeping sickness, case detection and treatment are the mainstay of control, so that accurate knowledge of the geographic distribution of infections is paramount. In this study, an Atlas was developed that provides village-level information on the reported occurrence of sleeping sickness. The geodatabase underpinning the Atlas also includes the results of active screening activities, even when no cases were detected. The Atlas enables epidemiological maps to be generated at a range of scales, from local to global, thus providing evidence for strategic and technical decision making.
In the field of animal trypanosomosis control, also known as nagana, much emphasis has recently been placed on the vector. Accurate delineation of tsetse habitat appears as an essential component of ongoing and upcoming interventions against tsetse. The present study focused on land cover datasets and tsetse habitat. The suitability for tsetse of standardized land cover classes was explored at continental, regional and national level, using a combination of inductive and deductive approaches. The land cover classes most suitable for tsetse were identified and described, and tailored datasets were derived.
The suite of datasets, methodologies and tools presented in this thesis provides evidence for informed planning and implementation of interventions against African trypanosomoses at a range of spatial scales.
Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished
17
Pedron, Julien. « Synthèse et étude de l'activité anti-kinétoplastidés de nouvelles 8-nitroquinoléin-2(1H))-ones bioactivées par les nitroréductases de type 1 ». Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30190/document.
Texte intégralRésumé :
Les kinétoplastidés sont des protozoaires flagellés responsables de maladies tropicales négligées mortelles telles que la leishmaniose viscérale (L. donovani et L. infantum) ou la trypanosomiase humaine africaine (T. brucei), pour lesquelles les traitements disponibles sont très limités. Depuis quelques années, on observe un regain d'intérêt pour le développement de nitrohétérocycles aromatiques anti-infectieux tels que le delamanide et le féxinidazole. De récentes études indiquent que l'activité anti-kinétoplastidés de ces dérivés repose sur leur bioactivation sélective par des nitroréductases parasitaires, conduisant à la formation de métabolites réduits électrophiles, fortement cytotoxiques. Suite à des études préliminaires réalisées dans notre équipe en série 8-nitroquinoléin-2(1H)-one, ces travaux de thèse portent sur la synthèse et l'étude in vitro de l'activité antiparasitaire de 80 dérivés notamment fonctionnalisés en positions 3 et 6 du pharmacophore par divers motifs, notamment via la mise au point de réactions d'halogénation sélective et de couplages pallado-catalysés. Ainsi, 5 nouvelles molécules hits (4 anti-kinétoplastidés et 1 sélective de T. brucei) ont été identifiées (0,01 µM ≤ CI50 ≤ 7 µM et 13 < IS < 1500), trois d'entre-elles étant des substrats sélectifs des nitroréductases parasitaires de type I. Afin de préciser les relations structure-activité, une étude des potentiels de réduction a également été menée. Des études physico-chimiques (solubilité, test de perméabilité PAMPA) et pharmacocinétiques in vitro (stabilité microsomale et fixation à l'albumine humaine) sont venues compléter ce travail. Enfin, des évaluations de la mutagénicité et de la génotoxicité de ces hits sur des cellules procaryotes et humaines ont été conduites, dans le but de statuer sur leur potentiel pharmaceutique antiparasitaire humain et vétérinaireKinetoplastids are flagellated protozoan parasites responsible for lethal neglected tropical diseases, such as visceral leishmaniasis (L. donovani and L. infantum) or sleeping sickness (T. brucei brucei), for which very few drugs are available. Nowadays, nitroheterocyclic compounds present a renewed interest as anti-infective agents, as illustrated by the development of fexinidazole and delamanid. Some recent studies demonstrated that the antikinetoplastid activity of these derivatives involves their selective bioactivation by parasitic nitroreductases, leading to the formation of electrophilic reduced metabolites, highly cytotoxic. Based on preliminary studies conducted in our team in 8-nitroquinolin-2(1H)-one series, this PhD work is about the synthesis and in vitro antiparasitic study of 80 derivatives mainly functionalized at positions 3 and 6 of the pharmacophore by various substituents, especially via the optimization of selective halogenation and pallado-catalyzed cross coupling reactions. Thereby, 5 new hit compounds (4 antikinetoplastid and 1 selective of T. brucei) were identified (0.01 µM ≤ IC50 ≤ 7 µM and 13 < SI < 1500), three of them being selective substrates of type I parasitic nitroreductases. In order to refine the structure-activity relationship studies, an analysis of reduction potentials was also conducted. In vitro physicochemical (solubility, PAMPA permeability assay) and pharmacokinetic (microsomal stability and human albumin binding) experiments completed this work. Finally, the mutagenicity and genotoxicity evaluations of these new hit compounds toward prokaryotic and human cells were realized, in order to assess their human and veterinary antiparasitic pharmaceutical potential
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Kaushik, Radhey Shyam. « Macrophage cytokines as correlate of differential resistance to African trypanosomiasis ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0014/NQ37893.pdf.
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Gould, Matthew K. « Putative phosphodiesterase inhibitors as potential new chemotherapies against African Trypanosomiasis ». Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/1410/.
Texte intégralRésumé :
African trypanosomiasis is a disease caused by the Kinetoplastida parasites Trypanosoma brucei rhodesiense and T. b. gambiense. The distribution of the disease is split geographically with T. b. rhodesiense found in eastern sub-Saharan Africa and T. b. gambiense in the west of the continent. Current treatment for this fatal disease is wholly unsatisfactory with problems such as extreme toxicity, affordability and the emergence of resistance. The case for the generation of new potential chemotherapies is compelling and urgent. Phosphodiesterase (PDE) enzymes degrade the secondary signalling molecule cyclic adenosine monophosphate (cAMP) to AMP by hydrolysis, thereby modulating and regulating the signal transduction to the effector proteins. The phosphodiesterase enzymes in the PDEB family in T. brucei were shown to be essential to the host-infective bloodstream forms and validated as good drug targets using RNA-interference (Zoraghi, R. and Seebeck, T., 2002; Oberholzer, M., 2007). Prompted by these findings, two series of putative trypanosomal PDE inhibitors, from different sources, were thoroughly assessed in this project for their anti-trypanosomal activity and their intracellular effects on the trypanosome. The whole-cell in vitro efficacy for each compound, against T. brucei wildtype and the drug-resistant strain TbAT1 knockout, was established by the standard resazurin reduction assay. 25 compounds from Series 1 had EC50 values below 0.5 µM, with 7 under 100 nM and the most active having an EC50 value of 5.8 ± 3.4 nM. For the much smaller Series 2 (GJS Compounds), the most active compound was GJS-128 with an EC50 value of 79.4 ± 10.3 nM. This demonstrates that a number of compounds from both series have potent in vitro activity against trypanosomes that is better than or equal to the current chemotherapeutic compound diminazene, and some Series 1 compounds are on a par with pentamidine and melarsoprol. No major cross-resistance was displayed by the TbAT1 knockout strain to either Series 1 or the GJS series. Similarly, a panel of Series 1 compounds tested against the B48 strain (resistant to pentamidine and melaminophenyl arsenical drugs), and also against Trypanosoma equiperdum wildtype and diminazene resistant (PBR) strains, showed no major cross-resistance displayed by the other resistant strains. This suggests that there would also be little or no cross-resistance from refractory strains in the field, and also that the compounds are active against multiple Trypanosoma species. A small panel of Series 1 compounds were also tested for efficacy against trypanosomes in infected mice. 4 daily doses of 20 mg/kg bodyweight of Compound 48 significantly reduced parasitaemia by approximately 60% compared to untreated controls, however higher concentrations were not tolerated by the mice so a cure could not be demonstrated. A high-throughput method for monitoring the speed of action of test compounds on trypanosomes in real time was developed, based on the fluorescence of propidium iodide when bound with DNA. Optimisation of the protocol to 96-well plates and low cell densities provided higher resolution and accurate traces of the lysis of trypanosomes in a cell suspension compared to previously used methods, as well as a greatly increased capacity. The propidium iodide assay could also be converted to provide end-point EC50 values that were directly comparable to those established by the standard resazurin reduction assay. The majority of Series 1 compounds did not increase the intracellular concentration of cAMP on incubation with bloodstream form trypanosomes; those that did only induced a minor elevation of the intracellular concentration of the signalling molecule. Since genetic disruption to phosphodiesterase enzymes resulted in large increases in cAMP levels (Oberholzer, M. et al, 2007; Zoraghi, R. and Seebeck, T., 2002), the lack of increase in cAMP by the Series 1 compounds strongly suggest that they do not sufficiently inhibit the PDEs in live trypanosomes and kill the cells via an alternative pathway. In contrast, incubation with the GJS compounds did result in significant increases in intracellular cAMP concentration with the most active being GJS-128 recording an approximately 3-fold increase in cAMP over 3 hours at just 30 nM. The concentrations that begin to increase cAMP level are consistent with the EC50 values for trypanosomes cultured in vitro (this study), and is also in line with inhibition data of recombinant TbrPDEB enzymes (work conducted by Dr. Herrmann Tenor, ALTANA Pharma, and Prof. Thomas Seebeck, University of Bern). This gives a clear and consistent link between the cause of cAMP rise (inhibition of PDEB by GJS compounds) and the effect of that concentration increase on bloodstream form trypanosomes (cell death), demonstrating that the GJS series are inhibitors of trypanosomal PDEs and chemically validate PDEs as drug targets for potential new chemotherapies against African trypanosomiasis. The effect of PDE inhibition on the physiology of the bloodstream form trypanosomes was also investigated. Flow cytometry analysis and the assessment of DNA configuration by fluorescence microscopy after DAPI staining determined that PDE inhibition by GJS-128 resulted in a precise block of the cell cycle in cytokinesis. The replicating trypanosome synthesized and segregated its DNA into two nuclei and kinetoplasts as normal and proceeded to initiate the physical separation of mother and daughter cells. The cleavage furrow between the old and new flagella progressed normally until the point of abscission, at which point division was halted with only a small section of plasma membrane connecting the two almost separated cells. Both cells appeared viable and underwent subsequent rounds of DNA replication, segregation and attempted physical separation that was always blocked near completion. This indicates cAMP signalling plays an important role in the correct physical separation of the replicating bloodstream form trypanosomes. A trypanosome cell line resistant to GJS-128 was developed by chemical mutagenesis and continuous culture with gradually increasing, but sub-lethal concentrations of the PDE inhibitor. This cell line, termed R0.8, was >15-fold less sensitive to GJS-128 and displayed significant cross-resistance to the other GJS compounds, as well as to stable, membrane permeable cAMP analogues. The mode of resistance was investigated by comparing the cAMP profile of the R0.8 and parental wildtype strains on incubation with GJS-128. No major differences were observed suggesting that both the adenylyl cyclase and phosphodiesterase activities remained unchanged in the PDE inhibitor-resistant strain. In support of this, the sequencing of TbrPDEB1 and TbrPDEB2 in both strains, while uncovering the loss of heterozygosity in the R0.8 line, revealed no mutations that would impact on enzyme function or inhibitor binding in the resistant cell line. These data strongly suggest that the adaptation resulting in resistance to PDE inhibitors is located in the effector proteins downstream of the PDEs and adenylyl cyclases in the cAMP signalling pathway. Identifying a compound that inhibits phosphodiesterases in trypanosomes and elevates cAMP concentrations, along with the generation of a PDE inhibitor-resistant cell line will allow more detailed examination of all aspects of the cAMP signalling pathway in T. brucei and across the Kinetoplastida. Phosphodiesterases have also been demonstrated to be chemically inhibitable in trypanosomes and could prove to be the target of a new generation of chemotherapies against African trypanosomiasis.
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Giordani, Federica. « New approaches to fluorescence-based diagnostics for human African trypanosomiasis ». Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2454/.
Texte intégralRésumé :
In the absence of any vaccine, prophylactic drug and effective vector control, the fight against human African trypanosomiais (HAT) is based on the the combination of active case-finding and consequent drug treatment of identified positive cases. Unfortunately, low sensitivity and specificity of current diagnostic techniques often result in misdiagnosis, leaving infected patients without cure or exposing them to inappropriate chemotherapy protocols, which use dangerous and expensive drugs. The development of more efficient, simple, cheap and field-robust diagnostic tests is, therefore, urgently needed. In the field, direct observation by light microscopy of trypanosomes in human fluids (blood, lymph node aspirate, cerebrospinal fluid) is considered the ideal way of confirming HAT infection. However, in practice this approach is problematic, especially for the Gambian form of the disease, where patients may present with very low parasitaemia. Detection limits of parasitological techniques can be improved by adding a preliminary step of sample concentration, although this further increases the laboriousness of HAT diagnostic algorithm. Recent advances in fluorescence microscopy could be exploited to facilitate trypanosome detection. The introduction and implementation of fluorescence microscopy in HAT endemic countries would offer the advantages of an increased overall sensitivity of microscopical examination and a more rapid screening of the specimen. In contrast to traditional, expensive and fragile fluorescence microscopes, new LED-illuminated instruments are relatively cheap, very efficient and portable, lending themselves to utilisation in poorly equipped rural settings. In order to design a new diagnostic tool that exploits LED technology, however, selective and reliable fluorescent markers to label trypanosomes in human fluids are needed. The development of new tools to assist in the diagnosis of African trypanosomiasis by use of LED fluorescence microscopy was the overall objective of this project. The work was mainly focused on testing various fluorescent compounds for their ability to selectively stain trypanosomes. Fluorophores were otained from commercial and academic sources, or else directly synthesised during the project. An important requirement evaluated was the compounds’ compatibility with the currently available SMR LED Cytoscience fluorescence microscope, developed and kindly provided by our collaborator Prof. D. Jones (Philipps University, Marburg). The utility of a UV LED-driven microscope in performing the arsenical drug resistance test was also assessed. This assay, developed in our laboratory to detect trypanosome strains resistant to arsenical and diamidine compounds, could represent a useful tool for chemotherapeutic decision making in the field, where resistance to arsenical drugs is a rising problem.
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Gichuki, Charity Wangui. « The role of astrocytes in the neuropathogenesis of African trypanosomiasis ». Thesis, University of Glasgow, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294595.
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Sullivan, Lauren. « Discovery and development of diagnostic biomarkers for human African trypanosomiasis ». Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/e6c3197a-849b-4148-8326-58a2b13f5072.
Texte intégralRésumé :
Human African Trypanosomiasis (HAT) or African Sleeping Sickness is a disease prevalent in many parts of Sub-Saharan Africa. HAT is a parasitic infection caused by two species, Trypanosoma brucei gambiense and T. b. rhodesiense. Clinical diagnosis is not sufficient as symptoms from other endemic diseases, such as Malaria, are similar. Currently the diagnosis of T. b. gambiense infection mainly relies on the Card Agglutination Test for Trypanosomiasis (CATT), which has severe limitations. Other diagnostic tests for T. b. gambiense and T. b. rhodesiense infections require lab based equipment, trained personnel and have varying degrees of sensitivity and specificity. New approaches are needed, firstly to identify new diagnostic biomarkers, and secondly to find a more suitable platform for the test. Our aim was to develop a lateral flow test based on trypanosome antigens. We used sera from T. b. gambiense infected and non-infected patients to identify infection specific diagnostic trypanosome proteins. The trypanosome proteins identified were then cloned into E. coli for recombinant expression and purification. The recombinant proteins were then screened by ELISA against 145 patients’ sera from the WHO HAT specimen bank. Invariant Surface Glycoprotein (ISG) 65 and a soluble Variant Surface Glycoprotein (VSG) were selected for development into a lateral flow format and 80 randomised patients’ sera were used to evaluate these prototypes. Here we describe the results showing that un-optimised proto-type lateral flow tests match the reported CATT sensitivity and specificity scores.
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Park, Suh Yeong. « Modeling Tsetse Fly Host Preference and African Trypanosomiasis in Cameroon ». The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306862287.
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Mabbott, Neil A. « Nitric oxide : host-protective or host-destructive during African trypanosomiasis ». Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU543723.
Texte intégralRésumé :
The aims of the research presented in this thesis were concerned with investigating the effect of inducible nitric oxide (NO) synthase expression during Trypanosoma brucei infections on both host and parasite. NO was shown to exhibit a potent cytostatic effect on parasite proliferation. Oxyhaemoglobin is a potent scavenger of NO. The cytostatic effects of NO on the trypanosomes were completely prevented through the addition of erythrocytes to the cultures. This implies that in the host blood-stream, NO is unlikely to be involved in the eradication of the parasites. Through the adoptive transfer of suppressor macrophages from T.brucei-infected donor mice to naive recipients, it was demonstrated that NO mediates a suppressive effect on host lymphocyte responses in vivo. Furthermore, suppressor macrophages were shown to have a finite life-span and undergo NO-mediated apoptosis. Evidence also suggested that elevated NO production in the bone marrow of T.brucei -infected mice is likely to play a significant role in the anaemia resulting from T.brucei infection. Experiments demonstrated that a soluble lysate prepared from freeze-thawed blood-stream form T.brucei, activated interferon (IFN)-gamma primed macrophages to express high levels of NO synthase. Experiments also demonstrated that viable blood-stream forms, but not procyclic form trypanosomes, released a soluble factor which in combination with IFN-gamma induced NO synthase. The absolute requirement of IFN-gamma priming for NO synthase activation by T.brucei was studied using macrophages from mutant mice lacking functional IFN-gamma receptors (IFN-gamma R -/- mutant mice). In comparison to macrophages from wild-type mice, cells from IFN-gamma-R-/- mutant mice were unable to produce NO following stimulation in vitro or infection in vivo. Finally, utilising mice with specific immunodeficiencies it was demonstrated that natural killer cells and a/b T-lymphocytes were important sources of IFN-gamma during murine T.brucei infections.
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Stebeck, Caroline Elizabeth. « The identification and characterization of two unique membrane-associated molecules of African trypanosomes ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21950.pdf.
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Ammar, Zeinab. « Caractérisation de l' interaction entre les trypanosomes africains et les cellules endothéliales : activation, inflammation et rôle des trans-sialidases ». Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22057/document.
Texte intégralRésumé :
La trypanosomose est la maladie parasitaire la plus dévastatrice en Afrique, et affecte à la fois les hommes et le bétail. Vu l’inefficacité des stratégies de contrôle actuelles, une stratégie alternative dite “anti-maladie” a été proposée dans le cadre de la trypanosomose animale. Elle vise à neutraliser les effets de la maladie plutôt qu’à éliminer le parasite. Une telle stratégie nécessite une meilleure compréhension du développement de la pathologie ainsi qu’une caractérisation détaillée des facteurs de virulence impliqués. Dans ce contexte, nous nous sommes intéressés à l’étude de l’interaction hôte/pathogène entre les trypanosomes Africains et l’endothélium de l’hôte mammifère. En comparant quatre espèces différentes de trypanosomes Africains, nous avons montré que leurs capacités d’activation des cellules endothéliales étaient distinctes. Nous avons clairement démontré que T. congolense, T. vivax et T. b. gambiense activent les cellules endothéliales via la voie de NF-ƘB, alors que T. b. brucei est incapable d’activer cette voie. Cette activation a induit une résponse pro-inflammatoire in vitro et in vivo, ce qui souligne l’importance de ce mécanisme dans le développement de la maladie. Pour la première fois, nous avons identifié une activité sialidase chez le parasite de l’homme T. brucei gambiense, et nous avons démontré que les trans-sialidases trypanosomales sont les médiateurs de cette activation endothéliale et de la réponse inflammatoire consécutive, et ceci à la fois chez les trypanosomes africains d’homme et d’animaux. De plus, nous avons montré que l’activation endothéliale implique l’activité lectin-like des trans-sialidases et non pas l’activité catalytique, ainsi que des récepteurs sialylés sur la surface endothéliale. En conclusion, ce travail a apporté des avancées considérables dans la compréhension de la relation hôte/pathogène et a permis de désigner les sialidases comme un facteur de virulence central dans le dialogue intermoléculaire durant les trypanosomoses, en faisant une cible de choix pour le vaccin « anti-maladie »Trypanosomiasis remains by far the most devastating parasitic disease in Africa affecting both humans and livestock. The current control strategies being not efficient, an alternative “anti-disease” strategy aiming to neutralize the pathological effects of the parasite rather than to eliminate it, was proposed. Therefore, it is essential to understand the development of pathogenesis and characterize the involved pathogenic factors. In this context, we wanted to elucidate the host-pathogen interaction between the African trypanosomes and the mammalian host endothelium. By comparing four different trypanosomes species, we showed that they displayed distinct capacities for activation of endothelial cells. We clearly demonstrated that T. congolense, T. vivax and T. b. gambiense activate the endothelial cells via the NF-ƘB pathway, but not T. b. brucei. This activation caused a pro-inflammatory response in vitro and in vivo, showing the importance of this mechanism in the development of pathogenesis. For the first time, we identified sialidase activity in the human parasite T. brucei gambiense, and demonstrated that the trypanosomal trans-sialidases are the mediators of this endothelial activation and its consequent inflammatory response, for both human and animal trypanosomes. Additionnally, we showed that endothelial cell activation is mediated by the lectin-like domain of the trans-sialidase rather than the catalytic site, and involves sialylated receptors of the endothelial cell surface. In conclusion, our study brings considerable insights into the host-pathogen relationship and designates sialidases as a central virulence factor in the molecular crosstalk during trypanosomiasis, which makes it a perfect target for the anti-disease strategy
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Akiode, Olukemi Adejoke. « Examination and management of human African Trypanosomiasis propagation using geospatial techniques ». Thesis, Abertay University, 2014. https://rke.abertay.ac.uk/en/studentTheses/9419b401-6604-4530-9938-57ab03234e67.
Texte intégralRésumé :
Human African Trypanosomiasis (HAT) is a vector-borne disease transmitted by the bite of the tsetse fly that results in high human morbidity and mortality. The propagation of the disease has been linked to environmental factors, and understanding the vector’s habitat is vital to its control. There is no HAT vaccine, but biological control of the vector has been successful in reducing HAT incidence. However, in recent years the disease has re-emerged and spread. Due to insufficient knowledge of HAT endemic foci, the disease management remains challenging. To achieve effective deployment of control strategies, accurate knowledge of the spatial distribution of the HAT vector is vital. The current study is based in Nigeria, and looks at part of Delta State, and a part of Jigawa State, in which HAT has been identified. The work utilizes remote sensing satellite imaging and fuzzy logic to develop a HAT vector habitat classification scheme, to explore the dynamics of HAT propagation. The goal was to develop a surveillance methodology to identify factors that influence HAT epidemiology. Land cover and ancillary data were integrated to classify HAT vector habitat using geospatial-fuzzy multicriteria analysis. The work highlights the significance of geospatial techniques where epidemiological data are limited, for improving understanding of HAT. This study helped distinguish HAT vector habitat into different zones (breed, feed and rest), which allowed the direction and magnitude of HAT, a n d factors influencing propagation to be determined. This helped identify ‘HAT priority intervention areas’. The study findings suggested propagation of HAT resulted from suitability of water bodies, shrub and less-dense forest for the HAT vector, and continued exposure of human populations to these land cover classes. Overlapping of HAT vector habitat zones within built-up areas was also a cause. The study also found that HAT propagation was multidirectional, and that this may have been influenced by landscape characteristics. This novel approach can also be used in other part of Nigeria as well as adapted to investigate other diseases. In conclusion, the HAT vector habitat classification scheme is a transparent tool for policy makers for identifying vulnerable and at risk areas.
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Hamadien, Maha. « Parasite signalling and host responses in experimental and human African trypanosomiasis / ». Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-266-3.
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Jones, Amy. « Melarsoprol cyclodextrin inclusion complexes for the treatment of human African trypanosomiasis ». Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2713/.
Texte intégralRésumé :
Human African trypanosomiasis (HAT) is a parasitic disease caused by the protozoan parasites T. b. rhodesiense and T. b. gambiense. The disease is currently endemic in 36 sub-Saharan countries with an estimated 60 million people at risk from the infection. The disease progresses through two stages; an early or haemolymphatic stage where the parasites are confined to the peripheral compartment and a late or encephalitic stage where the parasites penetrate the blood-brain barrier (BBB) and invade the CNS. Without treatment the disease is invariably fatal but at present chemotherapy is reliant on a small handful of drugs. Pentamidine and suramin are available for the treatment of the early stage of the disease while the CNS stage of the disease is treated with a combination of nifurtimox and eflornithine known as NECT therapy or melarsoprol. NECT therapy is only effective in the treatment of T. b. gambiense infections meaning treatment of T. b. rhodesiense infections is completely dependant on the trivalent arsenical melarsoprol. Melarsoprol is an extremely toxic compound, the administration of which is very painful and associated with numerous adverse reactions. The most series of which is a post treatment reactive encephalopy (PTRE). The PTRE occurs in up to 10% of all patients given melarsoprol of which 50% die as a result of the complication. This gives melarsoprol an overall fatality rate of 5% which is unacceptably high. There is therefore an urgent need for new trypanocides, which are safe and easily administrable. To improve the physiochemical and pharmacokinetic properties of melarsoprol the drug was complexed with two cyclodextrin molecules, hydroxypropyl-cyclodextrin (HPCD) and randomly methylated-cyclodextrin (RAMCD) to produce; mel/HPCD and mel/RAMCD. Cyclodextrins are cyclic oligosaccharides, widely used within the pharmaceutical industry to improve the solubility and oral bioavailability of poorly soluble lipophilic drugs. In this study, the trypanocidal activity of the melarsoprol cyclodextrin complexes was investigated in-vitro and in an in-vivo CNS stage model of T. b. brucei infection. The trypanocidal activity of melarsoprol is retained following its complexation with HPCD and RAMCD. The in-vitro trypanocidal activity of the melarsoprol cyclodextrin complexes against bloodstream T. b. brucei trypanosomes was comparable to that of contemporary melarsoprol. Furthermore, in an in-vivo murine model of CNS stage T. b. brucei the melarsoprol cyclodextrin complexes, mel/HPCD and mel/RAMCD produced 100% cure rates when administered orally at a dose of 0.05mmol/kg, daily, for seven consecutive days. Contemporary melarsoprol when administered by the same route and schedule only cured 33.3% of the animals. The cyclodextrins HPCD and RAMCD thus increase the oral bioavailability of melarsoprol whilst retaining the compounds trypanocidal activity. An oral administrable, water soluble formulation of melarsoprol instantly eliminates the problems associated with the intravenous administration of conventional melarsoprol. Furthermore, an orally available formulation would be of great benefit in the resource poor, isolated settings in which HAT occurs, as patients would not require hospitalisation during treatment thus alleviating the pressure on local hospitals. In the current investigation quantitative taqman PCR was utilised to investigate the rate of parasite clearance from the CNS during complexed melarsoprol treatment. Both mel/HPCD and mel/RAMCD were rapidly trypanocidal. Twenty-four hours after administration of one dose the number of trypanosomes within the brain was reduced by greater than 80% and all trypanosomes were eliminated from the brain by twenty-four hours after administration of four doses of mel/HPCD and five doses of mel/RAMCD. The elimination of all trypanosomes from the CNS following four doses of mel/HPCD and five doses of mel/RAMCD, indicates that it may be possible to reduce the dosage schedule from seven daily doses to four daily doses of mel/HPCD and five doses of mel/RAMCD. A short, simple, easily administrable treatment protocol is an essential requirement of any new trypanocide as if the treatment schedule is prolonged and complicated patients are unlikely to comply. CNS stage trypanosome infection is associated with a breakdown of the blood-brain barrier (BBB). Ideally following successful chemotherapy BBB function should be restored. In this investigation the effect of curative mel/HPCD treatment on the BBB was investigated in a murine model of CNS T. b. brucei infection using small bore MRI analysis. Mel/HPCD treatment results in a rapid restoration of BBB function as by twenty-four hours after the completion of mel/HPCD therapy the integrity of the BBB was fully restored. However, a very mild neuroinflammatory reaction persisted in the brain for up to fifteen days after completion of chemotherapy. This suggests that the BBB damage observed in trypanosome infection may be due to either the parasites directly or their secretory products and not as a result of the ongoing neuroinflammatory reaction. Despite melarsoprol being in use for over 60 years its pharmacokinetics are poorly understood and a sensitive assay by which to quantify the concentration of arsenic reaching tissues following administration of the compound is not available. In this study a gas chromatography mass spectrometry (GC-MS) technique was developed to quantify the concentration of arsenic reaching the plasma and brain following oral and intravenous administration of the melarsoprol cyclodextrin complexes, mel/HPCD and mel/RAMCD. The GC-MS assay had a limit of detection of 5ng/ml and a precision (expressed as the inter-day coefficient of variation) of 13.2%. The concentration of arsenic within the brain following the oral and intravenous administration of mel/HPCD was below the limit of quantification of the assay. The pharmacokinetics of mel/HPCD and mel/RAMCD could therefore not be determined in the present study. This study demonstrates that the melarsoprol cyclodextrin complexes mel/HPCD and mel/RAMCD are highly trypanocidal with no overt signs of toxicity and more importantly orally available. Following the oral administration of mel/HPCD or mel/RAMCD the melarsoprol is slowly released over a prolonged period of time from the cyclodextrin cavity. Patients are therefore not exposed to a ‘bolus’ of the drug as is the case in the intravenous administration of contemporary melarsoprol. The slow and sustained release of melarsoprol from the cyclodextrins should result in less adverse reactions and a decreased incidence of the PTRE. Furthermore, the complexed melarsoprol treatment protocol is shorter than the currently used 10 day concise melarsoprol treatment schedule therefore the total amount of melarsoprol administered to patients will be reduced. Patients should therefore experience fewer adverse reactions. In conclusion the results from this study demonstrate that the melarsoprol cyclodextrin complexes mel/HPCD and mel/RAMCD are promising oral candidates for the treatment of HAT.
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Ebiloma, Godwin Unekwuojo. « Identification of new lead compounds for the treatment of African trypanosomiasis ». Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8340/.
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Cullen, Danica Renae. « Development of tetrahydroisoquinoline analogues : Towards a treatment for Human African Trypanosomiasis ». Thesis, Curtin University, 2016. http://hdl.handle.net/20.500.11937/52988.
Texte intégralRésumé :
This research describes the exploration of a new scaffold with the potential to be developed in to a new drug for the treatment of Human African Trypanosomiasis (HAT), a neglected disease endemic in sub-Saharan Africa. Derivatives of an isoquinoline scaffold were synthesised and evaluated for their in vitro activity against T.b.rhodesiense, the causative agent of HAT. Five derivatives were identified with inhibition of T.b.rhodesiense in the sub-micromolar range with good selectivity over mammalian cells.
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Liu, Yajuan. « A role of sympathetic nervous system in immunomodulation of early experimental African trypanosomiasis / ». Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-113-X/.
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Jacquot, Laurence. « Les traitements de la trypanosomose africaine humaine : les données actuelles de la thérapeutique ». Paris 5, 1990. http://www.theses.fr/1990PA05P124.
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Whitecavage, Kellie Ann. « The characterization of a novel and essential trypanosome protein ». Click here for download, 2008. http://proquest.umi.com/pqdweb?did=1490081941&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.
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Silva, Achani Madushika. « Energetic basis of inappetence in an experimental murine infection of African Trypanosomiasis ». Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230060.
Texte intégralRésumé :
Trypanosoma brucei is the vector of African trypanosomiasis in both domestic animals (nagana) and sleeping sickness in humans (Human African Trypanosomiasis). These protozoan parasites are transmitted by the bite of infected tsetse flies (Glossina sp.). African trypanosome infections cause parasite-induced anorexia (PIA) and cachexia in livestock, experimental animals and in humans, and are of economic, veterinary and medical importance in sub-Saharan Africa. The overall aim of this project was to characterise the phenomenon of inappetence in relation to overall energy budget in African trypanosome infection and to then identify potential causal factors and mechanisms. A mouse model of T.b. brucei infection was established with a reproducible time course for the development of inappetence and bodyweight loss. Following an initial parasitaemic peak on day 6 post-infection, a profound period of inappetence was observed from days 7 to 11, accompanied by a 10% loss of body mass. Metabolisable energy intake was reduced, while assimilation efficiency increased significantly but not enough to compensate for the severe reduction in food intake. During the course of T.b. brucei infection, both total energy expenditure and physical activity were reduced. Although physical activity was markedly declined in both light and dark phases, trypanosome infected mice maintained their circadian rhythm albeit at a lower amplitude, with most of the activity occurring at the start of the dark phase. Resting metabolic rate was unchanged in infection. Plasma concentrations of the inflammatory cytokines, IL-6 and TNF-α were increased in infected mice and were associated with inappetence. Reductions of leptin and insulin concentration corresponded to a loss in fat mass. The hypothalamic control of appetite appeared to be normal with increases in appetite stimulating AgRP, decreases in the appetite inhibiting POMC and MC4R. There has been no previous data published on the control of appetite and energy expenditure in African trypanosome infections thus the data presented here provides a novel insight into the pathophysiology of this serious disease, and may lead to new therapies to manage the clinical and veterinary consequences of trypanosome infection.
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Barrett, John Charles. « Economic issues in trypanosomiasis control : case studies from Southern Africa ». Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385554.
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Baker, Nicola Louise. « Screening for new natural drugs and drug resistance determinants in African trypanosomiasis ». Thesis, London School of Hygiene and Tropical Medicine (University of London), 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590629.
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Sharafeldin, Ahmed. « Immunological studies in the brain and signaling pathways in experimental African trypanosomiasis / ». Stockholm : [Karolinska institutets bibl.], 2001. http://diss.kib.ki.se/2001/91-7349-072-5/.
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Cox, Andrew Paul. « Epidemiological analysis of host populations with widespread sub-patent infections : African trypanosomiasis ». Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/1560.
Texte intégralRésumé :
The epidemiological study of pathogens largely depends on three technologies, serology, microscopy and the polymerase chain reaction (PCR). Serological methods are unable to differentiate between current and past infections. Microscopy has historically been the mainstay of epidemiological study. In recent times the use of microscopy has been in decline, as it has been shown to have an inherent lack of sensitivity and specificity and produces many false negative results. PCR is now the method of choice for screening samples for the presence or absence of pathogens. Although PCR is widely regarded as an extremely sensitive technique, the fact that it assays a very small volume of sample is often overlooked. If the target pathogen is not present in the tiny aliquot of sample from an infected host, then a false negative results will occur. In endemic situations were the pathogen is present at low infection intensities, then the potential for false negatives results of this type is high. This intensity related false negative effect can lead to serious underestimation of diagnosed prevalence and incidence with consequent misinterpretation of the resulting data. This phenomenon has been reported in the literature for a range of pathogens and especially for epidemiological study of schistosomiasis. The extensive occurrence of false negatives during study of schistosomiasis samples was such an obstacle to epidemiological study it prompted the world health organisation to repeatedly call for quantitative methods to be employed to combat the problem. The main objectives of this thesis are to rationalise and simplify the methods of diagnosing African trypanosomes in epidemiological studies and to investigate the consequences of, and methods of dealing with infection intensity related false negative results that occur as a result of widespread sub-patent infections in the study population A new PCR assay was developed that was capable of analysing whole blood placed onto treated filter paper. The PCR assay was capable of differentiating between all the important African trypanosome species, producing a unique size of amplicon for each species of trypanosome. Initial results from repeated screening of human and cattle samples known to be parasitologically positive indicated that many false negative results occur. A more extensive analysis of thirty five bovine blood samples randomly chosen from a collection of field samples revealed that false negative results occurred regularly. The prevalence of infection after a single screening was 14.3% whereas the cumulative prevalence after over 100 repeated screenings rose to 85.7%. This showed that a severe underestimation of prevalence occurs from a single screening of the samples. In order to investigate the consequences of, and develop methods of dealing with this problem, computer based simulations were used to model the dynamics of screening samples with sub-patent infections. In order to construct the model the data obtained from repeat screening of the thirty-five bovine blood samples was fitted to a number of mathematical distributions. A negative binomial distribution best described the distribution of trypanosomes across the hosts. Exploration of the phenomenon with the resulting model showed the extensive underestimation of true prevalence that is possible. The simulations also showed that it is possible for populations with very different patterns of infection and true prevalence to all have the same diagnosed prevalence from a single screening per sample. Statistical comparison of these very different populations by diagnosed prevalence alone would conclude there was no significant difference between the populations. It was therefore concluded that the diagnosed prevalence from a single (or even multiple) screenings is an inadequate and potentially misleading measure of both infected hosts and parasite numbers. In order to deal with these problems new methods were evaluated for use in epidemiological studies. A simple method of producing quantitative measures of infection was advocated. The insensitivity of existing screening methods in detecting significant difference between populations was highlighted and a greatly improved methodology was shown. Finally, a method for inferring the true population prevalence from the data obtained from repeat screening of samples was suggested. Although some of these new methodologies have limitations, they represent a great improvement on the use of a single diagnostic test for each host. The work presented in this thesis highlights a serious potential limitation to our understanding of the epidemiology of pathogens that exist at sub-patent levels, and develops some possible methods of overcoming these limitations.
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Checci, Francesca. « Gambiense human African trypanosomiasis transmission dynamics and the impact of disease detection ». Thesis, London School of Hygiene and Tropical Medicine (University of London), 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536845.
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Palmer, Jennifer Jacqueline. « Utilisation of human African trypanosomiasis passive screening services in post-conflict Sudan ». Thesis, London School of Hygiene and Tropical Medicine (University of London), 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557286.
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Ngo, Nonga Sylvie. « Une nouvelle thérapeutique de la trypanosomose africaine humaine : l'éflornithine ». Paris 5, 1993. http://www.theses.fr/1993PA05P053.
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Ayed, Zoulikha. « Trypanosome humaine africaine : détection d'autoanticorps anti-neurofilaments et anti-tubulines : essai d'immunisation contre la trypanosomose expérimentale ». Limoges, 1999. http://www.theses.fr/1999LIMO117G.
Texte intégralRésumé :
La Trypanosomose Humaine Africaine (THA)à T. B. Gambiense est caractérisée par une atteinte du système nerveux central (phase II) dont la pathogénie, encore indéterminée, pourrait relever de phénomènes auto-immuns. L'étude du répertoire immunitaire de patients atteints de THA en phase lymphatico-sanguine (phase I) et en phase II, nous a permis de mettre en évidence dans le sérum et dans le LCR de ces patients la présence conjointe d'autoanticorps dirigés contre deux protéines du cytosquelette cellulaire. Il s'agit d'anticorps dirigés contre des protéines de filaments intermédiaires spécifiques des neurones, les sous-unités de 160 et 200 kDa de neurofilaments (NF). Ces anticorps étaient associés à d'autres qui reconnaissaient des protéines ubiquitaires appartenant aux microtubules, les tubulines α et ß. Ces deux types d'autoanticorps étaient significativement associés à la phase II. Chez les patients en phase I et chez les malades en phase II, ces anticorps (anti-NF et anti-tubulines) appartenaient essentiellement à la classe des IgM, alors qu'une proportion équivalente d'IgG et d'IgM de ces anticorps (anti-NF et anti-tubulines) a été observée dans le sérum des sujets témoins. Ils étaient par ailleurs, indétectables dans le LCR des sujets en phase I et dans celui des sujets témoins et pourraient de ce fait contribuer au diagnostic de la phase II. Nous avons montré que ces anticorps anti-NF et anti-tubulines sont induits par des antigènes stables et accessibles du trypanosomes (mimétisme moléculaire). En effet, la sous-unité 160 kDa de NF partage des épitopes avec des antigènes flagellaires de trypanosomes. Utilisant cette protéine de NF (160 kDa) et secondairement des protéines flagellaires de T. B brucei et de T. B. Gambiense, dans des conditions immunisantes, nous avons induit chez des souris swiss, des anticorps anti-NF et anti-flagelles (T. Brucei) qui ont été protecteurs contre l'infection provoquée par des formes de culture de T. B. Brucei AnTat 1-9 et T. B. Brucei AnTat 1-1E chez ces souris
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Force-Barge, Pierre. « La trypanosomiase humaine au Congo en 1990 ». Montpellier 1, 1991. http://www.theses.fr/1991MON11075.
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NGAHANG, KAMTE LANDRY STEPHANE. « Searching for effective natural products against Human African Trypanosomiasis (HAT) with special reference to African natural resources ». Doctoral thesis, Università degli Studi di Camerino, 2019. http://hdl.handle.net/11581/428679.
Texte intégralRésumé :
For centuries, African natives have been facing various infectious tropical illnesses, among which African trypanosomiases are some of the most frequent relevant parasitic diseases. African trypanosomiases, commonly called sleeping sickness in humans (HAT; Human African Trypanosomiasis) and Nagana in domestic livestock, affect a huge number of people living in poverty in 36 sub-Saharan countries, resulting in a key socioeconomic impact. After a century of outbreaks, due to political instability and lack of funding, around 70 million people and 50 million cattle are still at risk of exposure in Africa. Trypanosomiasis is transmitted by the bite of insects from the Glossina spp (Glossinidae) and is fatal in humans, if untreated. While taking a blood meal, infected Glossina flies can spread extracellular protozoans from the species Trypanosoma brucei. There are three morphologically indistinguishable subspecies of T. brucei. The subspecies T. b. gambiense is responsible for a chronic form of the human disease, while T. b. rhodesiense causes an acute form, which more rapidly leads to death. Both subspecies are infective to humans, whereas T. b. brucei is only infective to animals. During the early stage of the disease or hemolymphatic phase, the parasite is restricted to the blood and lymph and after months or years it invades the central nervous system resulting in various neurological symptoms including sleeping disturbance. As for other neglected tropical diseases, the chemotherapeutical arsenal against HAT is based on limited, expensive and often toxic medicines that are administered parentally in a context of poverty and lack of qualified personnell in healthcare centers. The few drugs that are available are pentamidine and suramin for the early stage disease and eflornithine (also in combination with nifurtimox) and melarsoprol for the late stage when the parasite infects the brain. Overall, the situation described above highlights the critical nature of this phenomena and the urgent need to explore new sources of potentially effective and safe compounds for therapy. In this scenario the naturally-occurring products may play a crucial role as source of bioactive drug candidates.
With this vision in mind, in Chapter 2 I performed a complete phytochemical analysis on both polar and volatile compounds of T. diversifolia collected from a geographically isolated population living in Dschang, Cameroon and I assessed their biological activities (antitrypanosomal and amtimicrobial activities). The main secondary metabolites occurring in the T. diversifolia methanolic extract were isolated by column chromatography and structurally elucidated by MS and NMR techniques. Tagitinins C emerged as the most active compound against T. brucei (TC221) with an IC50 value of 0.0042 μg/mL. This activity was 4.5 times better than that of the reference drug suramin. Then I analysed the chemical composition and the antimicrobial effects of the essential oil (EO) hydrodistilled from inflorescences of T. diversifolia. Results showed that T. diversifolia EO was mostly active against Staphylococcus aureus and selectively inhibited in vitro the NAD biosynthetic enzyme NadD from S. aureus (IC50 of ∼60 g/mL). Besides its extensive utilizations in the traditional medicine, the plant is believed to have a great potential in agriculture. For this reason, I decided to evaluate the T. diversifolia polar extracts against the two-spotted spider mite Tetranychus urticae (Tetranychidae), which is one of the most economically important arthropod pests worldwide. The ethyl acetate extract resulted as the most active oviposition inhibitor, with an ED50 value of 44.3 µg.cm-3 and an ED90 of 121.5 µg.cm-3.
In Chapter 3, I investigated a lipophilic extract of Onosma visianii roots containing 12% of shikonin derivatives. The phytochemical investigation of the lipophilic extract resulted in the isolation of 12 naphtoquinone derivatives which were evaluated against Trypanosoma brucei. Isobutylshikonin and isovalerylshikonin emerged as the most active naphtoquinone derivatives, showing an IC50 of 3.3 and 2.7 g/mL, respectively. Furthermore, isovalerylshikonin provided an inhibition of Glossina palpalis acetylcholinesterase (gpAChE) (IC50 = 7.1 μg/mL), stronger than isobutyrylshikonin (IC50 = 91.3 μg/mL), with a significant tse-tse fly versus human selectivity (SI = 7.2).
In Chapter 4, I oriented my attention to the Apiaceae family, which is a class of aromatic plants rich of EOs. Four out of nine Apiaceae EOs resulted active against T. brucei showing an IC50 in the range 2.7-10.7 g/mL. Terpinolene, one the major isolated component of these oils, was particularly active with an IC50 value of 0.035 g/mL (0.26 µM) and a selectivity index (SI) of 180. As part of the extended family of naturally-occurring products, sesquiterpenes hold promising inhibitory effects against the bloodstream forms of T. brucei. For this reason, in Chapter 5, I decided to explore the potential of Smyrnium olusatrum EOs obtained and its main oxygenated sesquiterpenes, namely germacrone, isofuranodiene, and β-acetoxyfuranoeudesm-4(15)-ene, as potential inhibitors of T. brucei. The EOs obtained efficiently inhibited the growth of parasite with IC50 ranging from 1.9 to 4.0 g/mL. Among the isolated main EOs components, isofuranodiene exhibited a significant and selective inhibitory activity against T. brucei (IC50 = 0.6 g/mL, SI = 30).
In Chapter 6, I finally selected six medicinal and aromatic plants traditionally used in Cameroon to treat several disorders, including infections and parasitic diseases. Then I evaluated the activity of their EOs against T. brucei TC221 and their selectivity against Balb/3T3 cells, used as counter-screen for cytotoxicity. The most relevant outcomes showed that the EOs from A. indica, A. daniellii and E. giganteus were the most active ones, with IC50 values of 15.21, 7.65 and 10.50 g/mL, respectively. Overall, the results of my PhD thesis provided new insights into the potential of naturallyoccurring compounds as valuable sources for the development of innovative trypanocidal drugs or botanical insecticides.
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Lane-Serff, Harriet. « Structural insights into innate immunity against African trypanosomes ». Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:3a1415e6-3df4-42dd-827b-d05edb2137be.
Texte intégralRésumé :
The haptoglobin-haemoglobin receptor (HpHbR) is expressed by the African try- panosome, T. brucei, whilst in the bloodstream of the mammalian host. This allows ac- quisition of haem, but also results in uptake of trypanolytic factor 1, a mediator of in- nate immunity against non-human African trypanosomes. Here, the structure of HpHbR in complex with its ligand, haptoglobin-haemoglobin (HpHb), is presented, revealing an elongated binding site along the membrane-distal half of the receptor. A ~50° kink allows the simultaneous binding of two receptors to one dimeric HpHb, increasing the efficiency of ligand uptake whilst also increasing binding site exposure within the densely packed cell surface. The possibility of targeting this receptor with antibody-drug conjugates is ex- plored. The characterisation of the unexpected interaction between T. congolense HpHbR and its previously unknown ligand, haemoglobin, is also presented. This receptor is iden- tified as an epimastigote-specific protein expressed whilst the trypanosome occupies the mouthparts of the tsetse fly vector. An evolutionary pathway of the receptor is proposed, describing how the receptor has changed to adapt to a role as a bloodstream form-specific protein in T. brucei. Apolipoprotein L1 (ApoL1) is the pore-forming component of the trypanolytic factors. An expression and purification protocol for ApoL1 is presented here, and the functionality of the protein established. Initial attempts to characterise the pores and structure of ApoL1 are described.
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Steketee, Pieter Christiaan. « Investigating the mode of action of AN5568, a novel therapeutic against African trypanosomiasis ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7478/.
Texte intégralRésumé :
The protozoan parasite Trypanosoma brucei is the causative agent of Human African Trypanosomiasis (HAT) and Nagana disease in mammals. These diseases present a major socioeconomic burden to large areas of sub-Saharan Africa. Current therapeutics involve complex and toxic regimens which can lead to fatal side-effects. In addition, there is evidence for drug resistance emerging in the field. Hence, there is a desperate need for novel therapies. Benzoxaboroles are a novel class of boron-containing compounds under development for use against a wide spectrum of diseases. AN5568 is a lead compound for the treatment of HAT, which has demonstrated effective clearance of both early- and late-stage trypanosomiasis in a murine model, and is currently undergoing clinical trials. However, the mechanism by which AN5568 kills T. brucei is elusive. In this study we sought to use 'omics'-based techniques to investigate the mode of action of AN5568 in a laboratory strain of Trypanosoma brucei brucei. Cells treated with the benzoxaborole showed significant perturbations in methionine metabolism. In particular, there were increases in S-adenosyl-L-methionine, an essential methyl group donor involved in methyltransferase reactions. These changes were similar to those elicited by the nonspecific methyltransferase inhibitor sinefungin. Changes were also observed in lipid metabolism, sugar nucleotide metabolism and glycophosphatidylinositol biosynthesis. Further analyses were carried out to investigate the effect of AN5568 on cellular stress responses and cell morphology. To further probe the mechanics of AN5568-treatment, a drug-resistant cell line was generated. This cell line showed cross-resistance with sinefungin, further supporting similar modes of action for these two drugs. Interestingly, the AN5568-resistant cell line exhibited upregulation of procyclic form-specific genes, as well as downregulation of blood-stream form-specific genes, which led to the hypothesis that the cell line had undergone a differentiation event. However, microscopy analysis showed that overall morphology of the cells still resembled those of bloodstream forms, despite them having acquired a procyclic-like metabolic physiology. A secondary aim of this project was to elucidate the metabolic changes that lead to increased growth rates in T. brucei cells undergoing loss-of-heterozygosity on chromosome 10. This phenomenon, whereby a significant portion of the chromosome is lost, has been observed independently on multiple occasions in lab adapted T. brucei strains, yet how this alteration affects intracellular metabolism was hitherto unknown. Using two procyclic T. brucei cell lines, this study was able to show that the increased growth rates are glucose-dependent with a potential intracellular alteration in succinate and acetate production. These data have important implications for the field, where LOH has been observed in the clonally expanding T.b. gambiense type I.
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Nalunkuma, Kazibwe Anne J. « Factors influencing the spread and selection of drug resistance in Human African Trypanosomiasis ». Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/381/.
Texte intégralRésumé :
A growing problem with drug resistance in Human African Trypanosomiasis has necessitated the implementation of screening programmes to monitor for its spread. This thesis describes the study of several factors that can influence the selection and propagation of drug resistance in T. brucei. Human African Trypanosomiasis (HAT) is caused by T. brucei gambiense and T. brucei rhodesiense. The few drugs used for the treatment of the disease are either toxic, cause severe side effects or suffer from parasite resistance. The T. brucei P2 transporter, which is encoded by the gene TbAT1, mediates uptake of melaminophenyl arsenicals and diamidines. Reduced P2 uptake is associated with drug resistance. A number of point mutations found in a laboratory derived melarsoprol resistant T. brucei stock (STIB 777R) allowed development of a PCR/RFLP based molecular method to identify resistance alleles. By 1999, 20-30% of patients treated in Omugo, NW Uganda were failing to respond to melarsoprol. PCR/RFLP analysis indicated that mutant alleles accounted for 58.5% of those in circulation. Melarsoprol was withdrawn in 2001 and by 2003 mutant TbAT1 alleles accounted for only 14% of those in circulation in NW Uganda. The current study aimed to determine the incidence of the PCR/Sfa NI TbAT1 mutant alleles in 2006, some five years after melarsoprol had been withdrawn as first-line treatment. Successful molecular analysis of 91 of 132 (68.9%) T. b. gambiense field isolates from Omugo and Moyo in NW Uganda indicated the presence of only TbAT1 wild type alleles. Mutant alleles thus appear to have disappeared. This may be the result of parasite fitness cost following the withdrawal of melarsoprol as a stage II first-line drug from Omugo health centre, Arua, since 2001. This apparent instability of TbAT1 mutants in the field may be exploited for rational or alternating use of melarsoprol and eflornithine (DFMO) to ensure a longer life for eflornithine, delaying the onset of resistance. Insight into the overall population structure of the T. b. gambiense from Omugo, Arua (N=54) and Moyo (N=17) was obtained using mini/microsatellite marker analysis. Genetic diversity was observed to be more intra than inter regional. Multilocus genotype data analysis revealed the Omugo, Arua, population was genetically distinct from the Moyo population (Nei’s genetic distance=0.176). The evidence indicated surprisingly little genetic exchange with an excess in homozygosity (Fis >0) and alleles in linkage disequilibrium (P<0.05) within the Omugo, trypanosome population. This excess in homozygosity may be due to population sub-structuring, trypanosome inbreeding, or migration of patients. The latter is likely occurring from the neighbouring T. b. gambiense endemic disease focus in Southern Sudan. The findings suggested that the T. b. gambiense from Arua is not panmictic, clonal or epidemic but there is some level of genetic exchange. The possibility that T. b. gambiense can infect animals raises the prospect that wild or domestic animals may act as a reservoir and that a veterinary link to gambiense Human African Trypanosomiasis exists. Treatment of animals for babesiosis and trypanosomes with diminazene, uptake of which is mediated through TbAT1/P2 could select for P2-defective drug resistant trypanosomes, thereby threatening control of the human disease as well. Species detection by PCR for animal and human trypanosomes in dog isolates (N=190) from the tsetse fly endemic Jos Plataeu, Nigeria did not reveal T. b. gambiense, but multiple infections with T. brucei (95%), T. vivax (89%), and subspecies T. congolense forest (54%) and savannah (50%) were detected. The dogs were also infected with other parasites, including Babesia canis (22%) and Hepatozoon canis (16%). Multiple infections can make correct diagnosis difficult and the infections are likely to be missed by the less sensitive microscopy method. The trypanocidal action of the diamidine group of trypanocides, diminazene, pentamidine and furamidine (DB75) are principally mediated through the TbAT1/P2. In addition, pentamidine is taken up by two additional T. brucei transporters called High Affinity Pentamidine Transporter (HAPT1) and the Low Affinity Pentamidine Transporter (LAPT1). DB75 also has a secondary unknown route. Loss of TbAT1/P2 leads to significant resistance to DB75 and diminazene but not pentamidine. Identification of other markers of resistance is necessary to determine if other routes of drug entry do exist apart from P2 and whether these can be exploited for the delivery of new trypanocides into the trypanosomes. Adaptation of the T. brucei tbat1 knock-out cell line to higher concentrations of diminazene by in vitro selection for resistance led to loss of HAPT1. The resultant phenotype was similar to the previously characterised pentamidine resistant clone B48, but more resistant to diminazene and DB75. The adapted line was still capable of accumulating 1 µM radiolabelled diminazene suggesting both HAPT1 and LAPT1 as possible routes for diminazene uptake. Adaptation of the T. brucei tbat1 knock-out cell line to a high concentration of DB75 over the same 6 months period did not lead to increased resistance. Overall the project has confirmed an important role for tbat1/P2 in development of resistance to melarsoprol in the field. Importantly, it appears that removal of the selection pressure of melarsoprol leads to a loss of tbat1 alleles associated with resistance in a population of trypanosomes capable of genetic exchange in NW Uganda. Although evidence for a dog reservoir for T. b. gambiense in Nigeria was lacking in this study, a risk of selecting resistance in animals must remain high on any list of consideration. I have further shown that the diamidine drug, diminazene, used in veterinary medicine also appears to enter T. brucei via the HAPT1 transporter, as well as the P2 transporter. Loss of HAPT1 through selection with diminazene leads to high level pentamidine resistance, which could indicate a further risk in selection of human infectious trypanosomes also resistant to drugs like pentamidine.
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O'Doherty, Oran Gilliland. « Synthesis of novel trypanosome alternative oxidase inhibitors for the treatment of African trypanosomiasis ». Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/64718/.
Texte intégralRésumé :
African trypanosomiasis is a protozoan infection affecting tens of thousands of people and millions of livestock animals across sub-Saharan Africa. In humans the disease is fatal without chemotherapeutic intervention and in animals it causes a severe anaemia that greatly impairs productivity. Available drug compounds are difficult to administer and unacceptably toxic. A natural product, ascofuranone, inhibits a key trypanosome specific respiratory enzyme, trypanosome alternative oxidase, and was shown over a decade ago to be trypanocidal using both in vitro and in vivo experiments. The compound suffers from rapid metabolism and contains several functionalities undesirable in a drug compound. Despite the promising activity the lack of applicable synthetic methods available hampered the development of chemotherapeutics from ascofuranone. In this work, novel synthetic routes were completed to explore the lead compound. New synthetic methods were successfully developed using palladium catalysed Suzuki couplings and Lewis acid catalysed rearrangements. Ortho-lithiation approaches also afforded potent novel inhibitors. Of particular note is a benzisoxazole, which is expected to alleviate many of the metabolic issues associated with ascofuranone. Alternate heterocycle analogues were explored and an interesting indazole analogue obtained. Finally, chemical methods were developed towards the benzisoxazole and indazole motifs with carboxylic acids, amenable to diversification by amide coupling. A preliminary range of novel amide containing 5, 6-heterocycles were synthesized to begin SAR exploration of these structures.
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TEMPORÃO, Adriana Beatriz Oliveira. « Different models of DNA immunization as strategy for vaccine development against African Trypanosomiasis ». Master's thesis, Instituto de Higiene e Medicina Tropical, 2016. http://hdl.handle.net/10362/19048.
Texte intégralRésumé :
A tripanosomose Africana, também conhecida como Doença do Sono, causada pelo protozoário Trypanosoma brucei, é uma doença tropical negligenciada. Esta doença pode ser controlada, tal como foi provado no passado; no entanto, o crescente número de pessoas afectadas e em risco torna o desenvolvimento de uma vacina uma prioridade. T. brucei é capaz de evadir constantemente o sistema imunitário do
hospedeiro, devido ao seu extraordinário mecanismo de defesa, que lhe proporciona uma grande variação antigénica. Devido a este mecanismo de defesa tem sido muito difícil de desenvolver uma vacina eficaz. Contudo, têm sido procuradas novas técnicas, entre elas, uma estratégia de vacinação com DNA plasmídico que têm revelado
resultados promissores. Tendo em conta estes resultados, este trabalho tem como objectivo o uso de três estratégias de imunização: a primeira, recorrendo a vacinas de DNA, usando dois plasmídeos que codificam candidatos antigénicos de Trypanosoma brucei; a segunda, usando estes candidatos antigénicos conjugados com uma anoformulação; e a terceira, usando VLPs (Vírus-Like Particles). Os três modelos usados no desenvolvimento de vacinas de DNA contra T. brucei recorreram ao uso de duas importantes proteínas do parasita: a MSP (Major Surface Protease) e a PLC (Phospholipase C). A MSP é uma metaloprotease de zinco de superfície, que se acredita ser responsável pela libertação de um fragmento de VSG (Variable Surface
Glycoprotein). A PLC é uma fosfolipase, ancorada a um resíduo de GPI
(Glycosylphosphatidylinositol), que cliva integralmente uma proteína de VSG da
superfície da célula. Como se pode ver, ambas as proteínas são responsáveis pela libertação das VSG, pela normal diferenciação da forma procíclica para a forma de corrente, e participam de forma sinérgica para a perda de VSG durante a diferenciação.
Após a imunização com as duas primeiras estratégias, apesar de em baixos níveis, os murganhos produziram anticorpos anti-Trypanosoma brucei brucei. Os que apresentaram melhor resposta imunológica foram os imunizados com a mistura de plasmídeos conjugados com a nano-formulação. Em relação ao terceiro modelo de imunização, o desenho das VLPs foi efectuado, e o próximo passo é a avaliação biológica das mesmas.African Trypanosomiasis, also known as sleeping sickness, caused by the protozoan Trypanosoma brucei, is a neglected tropical disease. This disease can be successfully controlled, as has been proven in the past; nevertheless, the growing number of people affected and at risk makes the development of a vaccine a priority. T. brucei is capable of constantly evading the host immune system, due to a remarkable mechanism of defense, which provides a great antigenic variation. Due to this mechanism it has been very difficult to develop an effective vaccine. However, new approaches have been pursued, one of which, the vaccination strategy with plasmid DNA has revealed some promising results. Based on this, this work aims to use three immunization strategies: the first one, DNA vaccination, using two plasmids DNA, encoding antigenic candidates from Trypanosoma brucei; the second one, using these antigenic candidates together with a nanoformulation; and the third one, using VLPs (Virus-Like Particles). The three models used in the development of DNA vaccines against T. brucei use two important proteins of the parasite: MSP (Major Surface Protease) and PLC (Phospholipase C). MSP is a surface zinc metalloprotease that is believed to be responsible by the release of a VSG (Variable Surface Glycoprotein) fragment. PLC is a phospholipase anchored to a GPI (Glycosylphosphatidylinositol) residue that cleaves a full-length VSG protein from the cell surface. As we can see, both proteins are responsible by the VSG release, by the normal differentiation from bloodstream to procyclic form, and they participate synergistically in VSG loss during differentiation. After immunization with the first two strategies, although the titres were low, mice produced antibodies anti-Trypanosoma brucei brucei. The animals that presented a better immune response were the ones immunized with the mix of plasmids together with the nanoformulation. Regarding the third model of immunization, the design of the VLPs was made, and the next step is evaluating them biologically.