Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis--Université de Bordeaux, 1936. / Includes bibliographical references (p. [125]-143).

No description available.

The heat shock protein-70 (Hsp70) family of molecular chaperones are ubiquitous highly conserved proteins that are critical for the viability of cellular homeostasis. The ATPase activity of Hsp70 proteins is critical to their function as the affinity of a given Hsp70 for non-native substrate is modulated by ATP binding and hydrolysis. When bound to ATP, Hsp70s possess a low affinity for a given substrate protein, while the hydrolysis of ATP to ADP causes a conformational change that results in a high affinity for substrate proteins. The basal ATPase activity of Hsp70s is too low to facilitate their function in vivo, and co-chaperones are essential to modulate the efficient protein folding by Hsp70. Heat shock protein-40 (Hsp40) heat shock proteins are essential for the in vivo function of Hsp70s by stimulating the ATPase activity of these proteins and facilitating transfer of substrates. The Type III class of Hsp40 proteins have not been well characterised due to their poor levels of conservation at the primary sequence level. This is due to the fact that Type III Hsp40s only contain a J-domain and a poorly conserved C-terminal region. The newly identified Type IV class of Hsp40s, contain an abrogated HPD tripeptide motif in the J-domain and have also not been extensively studied. Trypanosoma brucei (T. brucei) is a unicellular flagellated protozoan parasite. It is the causative agent of Human African Trypansomiasis (HAT) which results in thousands of deaths and devastating agricultural losses in many parts of Africa. T. brucei undergoes a complex lifecycle that is characterised by the transition from an insect vector to a mammalian host in markedly different conditions of temperature, pH, nutrient availability and respiratory requirements. It has been proposed that molecular chaperones may enhance the survival of these parasites due to their cytoprotective effect in combating cellular stress. Due to the fact that T. brucei infection is invariably fatal if left untreated, and that no novel treatment regimens have been developed recently, the identification of potential novel drug targets among proteins essential to the parasite’s survival in the host organism is an attractive aspect of T. brucei research. Because Type III Hsp40s are poorly conserved with respect to Hsp40s found in the human host, the identification of any of these proteins found to be essential to T. brucei survival in humans could potentially make attractive novel drug targets. An in depth in silico investigation into the Type III Hsp40 complement as well as partner Hsp70 proteins in T.brucei was performed. T. brucei possesses 65 Hsp40 proteins, of which 47 were classed as Type III and 6 of which were identified as being putative Type IV Hsp40s. A small but significant number (5) of Type III TbHsp40s contained tetratricopeptide (TPR) domains in addition to the J-domain. The J-domains of the Type III TbHsp40 complement were found to be conserved with respect to those of canonical Hsp40 proteins, although the mutation of certain residues that play a key role in Hsp40-Hsp70 interaction was noted. Potential partnerships of these proteins in the parasite was also investigated. The coding regions of three previously uncharacterised TbHsp40s were successfully amplified from T. brucei TREU927 genomic DNA and cloned into an expression vector. Tbj1, a Tcj1 ortholog, was selected for further study and successfully expressed and biochemically characterised. Tbj1 expressed in E. coli was found to be insoluble, but large amounts were recovered with the aid of a denaturing purification followed by refolding elution strategies, and the bulk of the protein recovered was in compact monomeric form as determined by size-exclusion chromatography fast protein liquid chromatography (SEC-FPLC). The addition of Tbj1 to a thermally aggregated substrate resulted in increased levels of aggregation, although Tbj1 was able to assist two Hsp70 proteins in the suppression of aggregation. Tbj1 proved unable to stimulate the ATPase activity of these same Hsp70s, and could not rescue temperature sensitive cells when replacing E.coli DnaJ and CbpA. It was concluded that Tbj1 does not possess independent chaperone activity, but could display Hsp40 co-chaperone properties under certain circumstances. This could allude to a specialised function in the T. brucei parasite. The lack of human orthologues to Tbj1 could result in the attractiveness of this protein as a novel drug target.

Over the past two decades movement of cattle towards the north of Uganda has enabled the Trypanosoma brucei rhodesiense focus in south-eastern Uganda to spread into previously unaffected districts. This thesis brings together important epidemiological data regarding the impact of mass cattle drug treatment on the point prevalence of several different species of trypanosome in a newly endemic area of human sleeping sickness. Crucially the findings illustrate mass drug treatment is effective in reducing the prevalence of T. b. rhodesiense in cattle, thus minimising the reservoir potential of these animals in the epidemiology of human disease. During 2006 a control programme was launched to halt the northward spread of this zoonotic parasite. This programme, entitled ‘Stamping Out Sleeping Sickness’ (SOS) proposed to reduce the prevalence of Human African Trypanosomiasis (HAT) in the newly affected districts by reducing the prevalence of this parasite in the main animal reservoir of infection – domestic cattle. Cattle were mass treated using trypanocides to clear infections. Previous work demonstrated the prevalence of T. brucei s. l. and T. b. rhodesiense in cattle was higher in the districts of Dokolo and Kaberamaido than in the other SOS intervention districts (Selby 2011). To determine whether animals in these areas were also exposed to pathogenic cattle trypanosomes samples were screened for the presence of T. vivax and T. congolense savannah using PCR. Chapter three of this thesis determined the prevalence of these trypanosomes in cattle in these districts. Before treatment had taken place the prevalence of T. vivax was 2% (4/200, 95% CI 3.57 – 0.12%) in Dokolo and 7.3% (21/310, 95% CI 10.17 - 4.24 %) in Kaberamaido. The prevalence of T. congolense savannah at baseline was 3.5% (7/200, 95% CI 7.08–1.42 %) in Dokolo and 9.1% (21/230, 95% CI13.6–5.7 %) in Kaberamaido. Monitoring was conducted three, nine and 18 months post treatment and both pathogens were detected at all time points. The impact the treatment had on point prevalence varied by trypanosome species and between the two districts. Several clusters of villages in Dokolo and Kaberamaido continued to report cases of HAT after the initial SOS intervention due in part to their proximity to livestock markets (Batchelor et al., 2009). In 2008 re-treatment of these ‘high risk’ areas was undertaken. Monitoring was performed before and six months after treatment. Cattle blood samples were collected at 20 village sites from ten ‘case-positive villages’ (from which human sleeping sickness cases had been reported six months prior to June 2007) and from ten ‘case-negative villages’ (no reported human sleeping sickness cases six months prior to June 2007). These samples were screened for all of the aforementioned trypanosomes using species specific PCR protocols. Chapter five details the results of this screening, and assessed whether re-treatment in Dokolo and Kaberamaido was effective in reducing the prevalence of trypanosomiasis. The re-treatment had a dramatic effect, significantly reducing the point prevalence of overall trypanosomiasis in the 20 villages screened from 38.1% (95% CI = 40.5 – 35.79%) at baseline to 26.9% (95% CI 28.96 – 24.97, p < 0.0001) at six months. Looking at each species separately, point prevalence of three out of four detected species of trypanosome fell significantly, including T. b. rhodesiense, which was reduced to 25% of its baseline prevalence. Finally the two SOS treatment cycles were compared both statistically and spatially with emphasis on trends at village level and the occurrence of mixed infections.

La maladie du sommeil ou Trypanosomose Humaine Africaine (THA) est une parasitose vectorielle due à un protozoaire flagellé sanguicole du genre Trypanosoma et d'espèce brucei. Deux sous-espèces de ce parasite sont pathogènes pour l'Homme : T. b. gambiense et T. b. rhodesiense ; transmis par les mouches Tsé-Tsé présentes en Afrique subsaharienne. Cette maladie évolue classiquement en deux stades : le stade hémolyphatique qui est marqué par la présence du parasite dans le sang et la lymphe et le stade nerveux caractérisé par la présence du trypanosome dans le Système Nerveux Centrale. En l’absence de traitement cette maladie est mortelle. Actuellement les traitements accessibles à la population sont stades-dépendants. Pour contrôler un jour cette pathologie, la recherche et l’amélioration des outils de diagnostic de la maladie et le diagnostic de stade sont essentielles. C’est dans ce but que nous avons exploité une biobanque d’échantillons composée de patients infectés par T. b. gambiense et d’individus non-infectés pour : 1) Évaluer l’efficacité de biomarqueurs de stade déjà existants -Néoptérine et CXCL-13- et nous avons évalué leur potentiel sur les échantillons recueillis lors du suivi des patients post-traitements. 2) Rechercher de nouveaux biomarqueurs protéiques par spectrométrie de masse LCMS/MS. Notre étude a permis d’identifier, grâce à l’établissement d’un nouveau catalogue protéomique un grand nombre de biomarqueurs potentiels dans le liquide céphalo-rachidien, l’urine et la salive de patients. Certaines de ces protéines pourraient améliorer la prise en charge et le suivi des patients à l’avenir. / Sleeping sickness, or Human African Trypanosomiasis (HAT), is a parasitic disease caused by a flagellar protozoan of the genus Trypanosoma and brucei species. Two subspecies of this parasite are pathogenic for humans: T. b. gambiense and T. b. rhodesiense; transmitted by Tsé-Tse flies present in sub-Saharan Africa. This disease classically evolves in two stages: the hemolymphatic stage which is define by the presence of the parasite in the blood and lymph and the nervous stage characterized by the presence of trypanosome in the central nervous system. Without treatment, this disease is lethal. Currently the available treatments for patients are stage-dependent. In order to control this pathology one day, research and improvement of tools for the diagnosis of the disease and the staging is fundamental. In this context, we have exploited a samples biobank composed of T. b. gambiense-infected patients and uninfected controles to: 1) evaluate the efficacy of existing stage biomarkers -Neopterin and CXCL-13- and we assessed their potential on the samples collected during post-treatment followup of patients. 2) determine new protein biomarkers using LC-MS/MS mass spectrometry. Our study identified a large number of potential biomarkers in cerebrospinal fluid, urine and saliva through the establishment of a new proteomic catalogue. Taking into account some of these proteins may improve patient management and follow-up in the future.

The objective of this thesis was to study whether heterocyclic dicationic compounds that are minor groove binders have the ability to inhibit the digestive properties of type II restriction enzymes which bind to the major groove of the DNA. If these compounds do possess the ability to inhibit restriction enzymes, then what factors influence their ability to inhibit the restriction enzymes? The methods used to study the interactions of DNA, compounds, and enzymes are gel electrophoresis, DNA thermal melting, and circular dichroism. The results from this project reveal that the minor grove binding compounds are able to inhibition type II restriction enzymes. The inhibition is heavily influenced by compound structure and the DNA binding sequence of the enzyme.

Mitochondrial gene expression in trypanosomatid pathogens requires extensive post transcriptional modification called RNA editing. This unique molecular mechanism, catalyzed by a multiprotein complex (the editosome), generates translatable transcripts for essential components of parasite respiratory complex. How editosome proteins are assembled and perform RNA editing is not fully understood. Moreover, previous studies have shown that editosome proteins are essential for parasite survival, which makes editosome as a suitable target for drug discovery. Currently, researchers use radio-labeled based assays to monitor RNA editing process. However, these assays are not suitable for high throughput screening of editosome inhibitors, have low detection limits, and cannot monitor RNA editing in real time. / Therefore, to develop a sensitive high throughput RNA editing assay, we have designed a sensitive hammerhead ribozyme-based fluorescence assay. Ribozyme structure was remodeled by adding or removing uridylate in its conserved catalytic core to make an inactive ribozyme. In the presence of the editosome, inactive ribozyme is edited to an active ribozyme. Consequently, hammerhead ribozyme activity can be measured by cleaving its fluorescently labeled substrate. We have shown that higher sensitivity is achieved using fluorescent based assay than conventional radio-labeled assay. Moreover, we can use this assay for rapid identification and characterization of the editosome inhibitors against RNA editing activities in trypanosomatids.

The protozoan parasite Trypanosoma congolense is one of the aetiological agents of African animal trypanosomiasis that is transmitted by the tsetse fly. The parasite causes nagana in animals and affects livestock throughout sub-Saharan Africa. The toxicity of available drugs and the emergence of drug resistant parasites have affected the treatment of trypanosomiasis. Control of the disease has also been difficult due to ineffective vector control and the potential of trypanosomes to express hundreds of antigenetically distinct proteins on their surface. Vaccination against trypanosomiasis has been thought to be a possible control method. Since a vaccine based on variable surface proteins of the parasite is unlikely, research has been directed towards the identification of invariant pathogenic factors of the parasite as potential targets for therapy. Congopain, the major cysteine protease of T. congolense has been implicated in the pathology of the disease. Antibodies against congopain are known to contribute to the mechanisms of natural resistance to trypanosomiasis known as trypanotolerance by neutralising the pathogenic effects of the enzyme. Oligopeptidase B (OpdB), a trypanosomal serine protease has also been associated as a pathogenic factor of the disease. It is released into the host’s circulation by dead or dying parasites and retains its catalytic activity since it is insensitive to host serum inhibitors. In the present study, the catalytic domain of congopain (C2) and the use of alpha-2-macroglobulin (α2M) as an adjuvant were investigated for their potential use in an anti-disease vaccine. α2-Macroglobulin has been used to varying degrees to target different antigens to cells of the immune system and enhance their immunogenicity. A previous study showed that antibodies raised in rabbits against C2 complexed to α2M gave a higher percentage inhibition than antibodies made using C2 mixed with Freund’s adjuvant. In the present study, goats were immunised with C2 complexed with α2M to confirm the enhanced immunogenicity of C2 and the production of anti-C2 antibodies with superior inhibitory properties. Following immunisation, goats were challenged with T. congolense (strain IL 1180) and showed sustained antibody production during the two month infection period. Goat antibodies made using C2 in complex with α2M inhibited the hydrolysis of hide powder azure by C2 by 96%. Maximum inhibition of the hydrolysis of azocasein was observed to be 63% and hydrolysis of Z-Phe-Arg-AMC by C2 was inhibited by 73%. In order to determine the vaccine potential of OpdB, protein was recombinantly expressed as a glutathione-S-transferase fusion protein in the pGEX expression system and purified by glutathione agarose affinity chromatography and molecular exclusion chromatography. Since a small yield of protein necessitated several rounds of expression and extensive purification, OpdB was subsequently expressed as a His-tagged fusion protein in the pET bacterial expression system. Recombinant protein was easily purified using nickel chelate affinity chromatography. Purified OpdB was used with alum for the immmunisation of mice to produce antibodies capable of inhibiting enzyme activity. Following immunisation, mice were challenged with T. congolense (strain IL 1180) and also showed sustained antibody production following two months infection. Since all mice died, the administration of OpdB conferred no protection; however, anti-OpdB mouse antibodies inhibited 86% of OpdB activity against the substrate Z-Arg-Arg-AMC. In addition immunised mice were observed to survive 40% longer than control mice as they had previously been immunised with OpdB and were able to mount a rapid immune response against this pathogenic factor during infection. In general it could be concluded that immunisation of goats with C2 in complex with α2M produced antibodies with superior inhibitory properties. The immunisation of mice with OpdB and alum also produced inhibitory antibodies and previous administration of OpdB enabled mice to mount a rapid immune response against OpdB during infection. Antibody mediated enzyme inhibition demonstrates the potential use of C2 and OpdB as vaccines that may contribute to the development of an effective anti-disease vaccine. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Lipid metabolism in Trypanosoma brucei, the causative agent of African sleeping sickness, differs from its human host, allowing a plethora of novel drug targets to be discovered and validated. Cytidine diphosphate diacylglycerol (CDP-DAG) is a central lipid intermediate produced by the enzyme CDP-DAG synthase (CDS), but nothing was known about CDS in T. brucei. Only one gene encodes CDS in Trypanosoma brucei (Tb927.7.220) and this was shown to encode a functional CDS by overexpression in E. coli and complementation of a yeast CDS null, which was created during this study. Expression and activity of TbCDS was confirmed in T. brucei, and was shown to be essential in both life cycle stages. Disruption of TbCDS altered the lipid profile of T. brucei, confirming a central role for CDP-DAG in phospholipid synthesis. Biochemical and morphological characterisation of mutants in TbCDS expression elucidated at least two separately localised and regulated pools of CDP-DAG and phosphatidylinositol in T. brucei. In bloodstream form these pools are localised to the Golgi and the ER, however in procyclics it is possible that both of these pools are localised to the Golgi, since no phosphatidylinositol synthase protein was detected in the ER of procyclics. Reduction in TbCDS was shown to affect cell cycle regulation and Golgi segregation possibly due to a depletion of phosphorylated phosphatidylinositols (PIPs). These studies also indicate that phosphatidylglycerol may be synthesised by the phosphatidylglycerol-phosphate synthase which may be capable of using phosphatidylserine as a substrate in a headgroup swapping reaction. TbCDS has now been genetically validated as a drug target, and has highlighted novel aspects of lipid biosynthesis in T. brucei. Collectively, these findings highlight the central role played by TbCDS and the new knowledge gained here may lead to the discovery and validation of other novel drug targets against African sleeping sickness.