University, Diss.--Basel, 1994.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2009. / Härtill 4 uppsatser.

Face à la stagnation voire à la réduction des ressources allouées à la lutte contre le paludisme, des études sur une connaissance approfondie de la micro-épidémiologie et le développement de vaccins antipaludiques s’imposent comme une alternative pour une utilisation rationnelle des fonds. Nos résultats montrent que l’hétérogénéité du risque de paludisme à l’intérieur du même village était perceptible pendant la saison sèche. L’analyse de séries chronologiques a montré un décalage de 3 mois entre le pic de la pluie et le pic des cas de paludisme. L’hétérogénéité était associée soit à la prévalence du portage asymptomatique du parasite, soit à la forte densité anophélienne ou aux deux facteurs simultanément. Des mesures de lutte ciblant les maisons ou les zones de forte transmission auront un impact très limité à l’échelle infra-villages, lorsque ceux-ci sont de faible dimension (<1km2) et que l’incidence clinique est forte. La prise en compte des facteurs hydrométéorologiques de risque dans l’implémentation des stratégies de lutte contre le paludisme est nécessaire. L’essai clinique de phase 2 a montré un effet protecteur de MSP3 dans la zone de transmission saisonnière comparée à celle de transmission continue. La protection était associée aux fortes réponses anti-MSP3 cytophiliques, un résultat clé pour sélectionner et améliorer les formulations pour les futurs essais de terrain. L’essai clinique de phase 1b a montré que PfSPZ était bien toléré et protégeait significativement contre les infections naturelles dues à P. falciparum pendant toute la saison de transmission. La poursuite de la recherche sur ces candidats vaccins mérite dès lors une attention particulière. / Faced with the stagnation or even the reduction of resources allocated to fight against malaria, studies focusing on a thorough knowledge of micro-epidemiology and the development of malaria vaccines are increasingly becoming an alternative for rational use of funds. Our results show that the heterogeneity of malaria risk within the same village was perceptible during the dry season. Time series analysis showed a 3-month lag between the peak of rain and the peak of malaria cases. The heterogeneity was associated either with the prevalence of asymptomatic parasite carriage, or with the high anopheles density or with both parameters. Thus, control measures targeting houses or areas of high transmission will have a very limited impact at village scale (<1km2). The consideration of hydrometeorological risk factors in the implementation of malaria control strategies is necessary. The Phase 2 clinical trial showed a protective effect of MSP3 in the seasonal transmission zone compared to the continuous transmission zone. Protection was associated with strong anti-MSP3 cytophilic responses, a key outcome for selecting and improving formulations for future field trials. The Phase 1b clinical trial showed that the PfSPZ vaccine was well tolerated and significantly protected against natural P. falciparum infections throughout the transmission season. Further research into these vaccine candidates deserves special attention.

Made available in DSpace on 2012-05-07T15:26:24Z (GMT). No. of bitstreams: 2 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) 000018.pdf: 1794665 bytes, checksum: d80d7e7bbb820f44c121888af65efd06 (MD5) Previous issue date: 2007 / A resistência do Plasmodium falciparum aos principais antimaláricos ainda é o principalproblema no controle da malária humana. [...] Parasitos da malária transfectadoscom a Proteína de Fluorescência Verde (GFP) têm sido produzidos em sistema detransformação estável. Isso permite utilizar a fluorescência como um marcador paraidentificar os parasitos. Assim, buscou-se neste estudo determinar o uso potencial deparasitas da malária murina (P. berghei) e da malária humana (P.falciparum)transfectados com a GFP para os ensaios de quimioterapia experimental. Para osexperimentos in vivo, utilizou-se a cepa GFP-P. berghei que apresenta um geneexógeno de fluorescência verde e resistência à pirimetamina (Sultan et al. 1999).Camundongos suíço-albinos ou BALB/c foram infectados com a cepa GFP-P. bergheiou a cepa não transformada (NK65), por via intraperitoneal. Excluindo as drogas commecanismo de ação similar ao da pirimetamina, os resultados iniciais demonstraram quea susceptibilidade a diferentes classes de antimaláricos foi semelhante entre a cepa GFPP.berghei e a cepa P. berghei NK65. Demonstrou-se ainda que a virulência in vivo dacepa GFP-P. berghei foi similar a da cepa não transformada. A próxima etapa foivalidar a cepa GFP-P. berghei em um ensaio fluorimétrico para avaliar drogasantimaláricas. Para tal, os animais foram infectados com a cepa GFP-P. berghei,tratados com antimaláricos convencionais, e as parasitemias avaliadas pela citometria defluxo ou pelo método convencional de microscopia óptica. A parasitemia determinadapela citometria de fluxo se correlacionou com aquela determinada pela microscopiaóptica. Assim, os resultados permitiram concluir que a cepa GFP-P. berghei foiadequada para a triagem de drogas in vivo podendo substituir a técnica convencional demicroscopia óptica. [...] A cepa GFP-P.falciparum foi mantida emcultivo contínuo e as parasitemias das culturas foram analisadas, em paralelo, porcitometria de fluxo e microscopia óptica. Os resultados obtidos in vitro tambémdemonstraram que a quantificação da parasitemia obtida por citometria de fluxo eraespecífica. Finalmente, em ensaios quimioterápicos in vitro, utilizando antimaláricosconvencionais, o método fluorimétrico foi similar ao da hipoxantina tritiada. [...] O modelo descrito neste trabalho podefuncionar como uma importante ferramenta para acelerar o processo dedesenvolvimento de novas drogas para o tratamento da malária

Made available in DSpace on 2012-09-05T18:24:06Z (GMT). No. of bitstreams: 2 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) 182.pdf: 7820871 bytes, checksum: 32a3aac521ae52c995a41beff916fb40 (MD5) Previous issue date: 2003 / Introdução: A malária é uma doença parasitária provocada por protozoários do gênero Plasmodium. (...) Baseado na importância da malária em Roraima (...) o objetivo deste trabalho foi analisar uma base de dados secundária para tentar contribuir com o estudo da problemática da transmissão da malária nesse Estado. Metodologia: Fez-se a análise histórica de uma base de dados de malária e outra de precipitação pluviométrica para o período de 1985 a 1996. Foram calculados os índices parasitários anuais e mensais (IPA e IPM, respectivamente). Utilizou-se os dados das leituras diárias da precipitação de 20 estações pluviométricas.Foram utilizados vários programas para a realização das análises: Surfer para gerar dados interpolados para a variável precipitação, com uso do método kriging; Arcview para elaboração de mapas; Spring para a realização da análise espacial e obtenção do índice de Moran; e, SAS para a análise estatística utilizando PROC GLM e as médias foram obtidas por LSMEANS. Resultados e conclusões: Em Roraima, a malária se apresenta com valores médios a altos no Estado de Roraima durante todo o período de estudo. A análise dos dados antes e depois da divisão municipal sugere que a malária possui transmissão focal e que os dados sobre essa doença devem ser obtidos, de preferência, por localidade. Dessa forma, os planejamentos de controle não se dispersariam em uma grande área e sim sobre as áreas que realmente tem relevância e assim diminuir a incidência e a prevalência da doença.A observação de que o uso de uma defasagem de um a dois meses é a ideal para verificar os possíveis períodos de transmissão da malária associados com a precipitação (=0,0001), sugerindo que essa análise provavelmente deva ser feita utilizando-se de períodos de tempo menores como semanas e até mesmo dias para determinar com maior precisão qual é a defasagem real entre a precipitação e a transmissão da doença em Roraima. Com relação aos dados de precipitação, pode-se afirmar que o uso do interpolador para inferir dados de chuva das estações pluviométricas para todo o município é possível de ser efetuado, visto que os valores originais de cada estação coincidem com a sua localização no mapa interpolado. De acordo com isso, estudos futuros que visem a elaboração de modelos explicativos para o mecanismo de transmissão da malária em Roraima, devem levar em consideração os outros fatores de risco para a transmissão da doença e não unicamente a precipitação pluviométrica.

The purpose of this study was to investigate the effects of cerebral malaria on the neuropsychological functioning of non-immune Ghanaian children. Twenty hospital-referred children between ages 7 and 16 years who met the World Health Organization (W.H.O., 1986) research criteria for the diagnosis of cerebral malaria, and who had no known history of other neurological disease were recruited for this study. Twenty matched control healthy children without a history of malaria or other neurological disease were also assessed. Each subject was administered a battery of neuropsychological tests judged to be highly sensitive to brain injury and relatively impervious to linguistic or other cultural factors. These results (from comparisons using the general linear model) are the first to provide evidence of subacute neurobehavioural sequelae of cerebral malaria in children. Subjects demonstrated deficits in such functional domains as accuracy of visual scanning, immediate and delayed visual memory, bimanual tactile discrimination, perceptual abstraction and rule learning skills, right ear auditory information processing, and dominant hand motor speed. A strong negative association between coma duration and bimanual tactile discrimination performance was also found. Contrary to expectations, no evidence for emotional dysfunction resulting directly from cerebral malaria emerged from this study. Nonverbal reasoning, visuospatial processing, auditory attention and sequencing, verbal fluency, and fine motor dexterity were found to be intact. The pattern of neuropsychological test performance in this study was judged to be consistent with a small-vessel cerebrovasculitis secondary to infection with plasmodium falciparum. Implications and limitations of this investigation, as well as directions for future research were discussed in the context of malaria endemicity. / Graduate

Le paludisme (ou malaria) est la parasitose la plus répandue à travers le monde (WHO, 2011).La moitié de la population mondiale est exposée à cette maladie causée par le protozoairePlasmodium. La résistance aux traitements qui se développe chez le parasite représente un véritableobstacle à la mise en place de programmes de lutte globale. Le développement de nouveauxprotocoles thérapeutiques plus efficaces ciblant les apicomplexes Plasmodium passe par uneamélioration de nos connaissances concernant la biologie fondamentale des parasites. Par ce biais,nous pourrons identifier de nouvelles cibles originales visant des mécanismes essentiels etspécifiques au développement du pathogène. Chez Plasmodium falciparum (l’espèce responsable dela forme la plus mortelle de malaria), la phase érythrocytaire qui se déroule chez son hôte humain estrelativement courte (48 heures). Le parasite y subit un grand nombre de changementsmorphologiques nécessitant une différentiation précise, spécifique et régulée au cours du temps.Parmi les éléments pouvant contrôler ces mécanismes, les phénomènes de phosphorylationréversibles semblent être des candidats de choix.Nous avons, dans un premier temps, entrepris la caractérisation de PfI2. Ce travail a permisd’identifier cette protéine comme étant un régulateur négatif de PfPP1 localisé au niveaunucléocytoplasmique et indispensable au développement érythrocytaire du parasite. Des étudesd’interaction in vitro et in vivo ont permis d’identifier un certain nombre de résidus impliqués dans lafixation et la fonction de PfI2. En nous basant sur ces résultats, nous avons entrepris une explorationplus précise des relations structure/fonction du complexe PfI2/PfPP1.Concernant l’identification de PfI3, nous avons récemment publiée dans le Journal ofBiological Chemistry (Frèville A. 2012) un travail montrant que chez le parasite, l’inhibiteur 3 estlocalisé au niveau nucléaire et est essentiel au développement asexuel du pathogène. Desexpériences d’interaction in vitro ont permis de montrer que PfI3 est capable de se fixer in vitro àPfPP1 et ce principalement via le motif primaire RVxF. Chez des levures déplétées de leur inhibiteur3, l’expression épisomique de PfI3 n’a pas permis de restaurer la croissance des cellules. Desexpériences in vitro d’activités phosphatase révèlent une action positive de PfI3 sur PfPP1. Cerésultat, inverse de celui que l’on observe chez ses homologues chez la levure ou l’humain met enévidence une fonction différente et spécifique de PfI3 et font de cette protéine un régulateurnucléaire potentiel de PfPP1 chez Plasmodium falciparum.L’ensemble de ce travail de thèse à permis d’identifier et de caractériser chez Plasmodiumfalciparum deux régulateurs potentiels de la phosphatase de type 1 mais également de mettre enévidence un certain nombre d’éléments spécifiques au fonctionnement et au développement duparasite faisant de ces protéines des cibles thérapeutiques intéressantes. / X

Late-stage gametocytes of P. falciparum parasites are responsible for the ongoing human-to-mosquito transmission of malaria disease. To block transmission, novel gametocytocidal compounds are required. It is thus important to determine ex vivo efficacy against diverse, contemporary clinical isolates as an early filter to provide confirmation of novel gametocytocidal activity in the field. This study hypothesizes that differences in drug responses in late-stage gametocytes of clinical isolates can be correlated with the extent of genetic diversity of clinical isolates. Previously, potent phosphatidylinositol 4-kinase (PI4K) inhibitors indicated differential drug response, which was observed in transmissible stages of ex vivo southern African P. falciparum clinical isolates. These differential drug responses were not only limited to kinase inhibitors, but also seen with endoperoxide and ATP4 inhibitors that were used in the current study. Microsatellite (MS) and single nucleotide polymorphism (SNP) markers determined the allelic variation of clinical isolates, and therefore genetic complexity can clarify differential drug response in isolates. Here we confirm that isolates from the high transmission areas are characterised by a high multiplicity of infection (MOI) and isolates exhibit many unique alleles. This study also shows that there is a relationship between gametocyte production and isolates that are genetically diverse. Furthermore, the study presents SNP barcoding as a more sensitive and robust genotyping technique, as it was able to correlate differential drug response to genetic complexity of clinical isolates. / Dissertation (MSc (Biochemistry))--University of Pretoria, 2020. / National Research Foundation-Grant holder linked bursary / Biochemistry / MSc (Biochemistry) / Unrestricted

Recent data indicates that the challenge to overcome malaria still continues, regardless of all the significant efforts and advances in drug and medical technologies. The rise of drug resistance, particularly in the virulent parasitic plasmodia strains in many malaria prone regions is the principal contributor to this trend. The on-going task that researchers are faced with is to design new strategies to develop novel drugs which may fare better than the existing antimalarial drugs or improve their efficacy. In response to this challenge, we have explored the plasmodia inhibitory potential of dihydropyrimidinone (DHPM) analogues based on their known marked abilities to reverse resistance in malaria in combination with chloroquine (CQ)-like moieties in a single entity and hence act as reversal agents (RAs). In this research we embarked upon a hybrid-drug approach by taking advantage of the multi-functionalised reaction sites on the DHPM scaffold and covalently linking them through amide bond formation or triazole linker to quinoline and chalcone-based moieties. The targeted highly functionalized DHPM hybrids also presented the opportunity for structure-activity relationship (SAR) studies to be conducted and their crystalline nature paved the way for further crystallography studies. Four series of compounds were evaluated for their antiplasmodial activities. In the first set of compounds the in vitro antiplasmodial activity of DHPMs and DHPM-quinoline-based hybrids was assessed against K1 CQ-resistant (CQR) strain at 1 and 5 µM to determine the inhibition (%) using CQ as the reference drug (Figure 3.16, Table 3.3). The DHPMs used as the RAs, displayed minimal activity against the K1 strain of P. falciparum. In the first set of compounds the plasmodia inhibitory data indicated that generally all the DHPM-4-aminoquinoline hybrids revealed excellent to good activity against the K1 CQR strain, including hybrids 3.11d-f with a % inhibition ranging from 97.6-103.1 displaying markedly a greater potency than CQ at 1 µM and the hybrids 3.11a,d,e with a % inhibition ranging from 97.5 -105.3 exhibiting a more superior activity than CQ at 5 µM. Overall, the remaining hybrids displayed comparable activity to CQ with hybrid 3.11i having the least % inhibition of 71 and 66% at 1 µM and 5 µM respectively. From the antiplasmodial study, we were able to show that all the hybrid compounds containing a benzoyl group at position 5 of the DHPM displayed good antiplasmodial activity against the K1 CQR strain of P. falciparum. This finding further supports the need for the presence of two separate aromatic rings to exhibit a notable increase in the antiplasmodial activity and could be used as potential RAs. In the second series of compounds the in vitro antiplasmodial activity of DHPMs azide-based intermediates 4.5e-h, DHPM-quinoline-triazole hybrids 4.13a-h and DHPM-mefloquine-triazole hybrids 4.14a-h was evaluated against NF54 CQ-sensitive (CQS) strain at 1 and 5 µM to determine the growth inhibitory activity (%) using CQ as the reference drug (Figure 4.14, Table 4.3). The DHPM-4-aminoquinoline-triazole hybrids 4.13a-d with % inhibitions ranging from 97.0 to 99.0 displayed the best inhibitions comparable to CQ at both 1 and 5 µM a against NF54 CQS strain. The most potent compounds, the DHPM-quinoline-triazoles hybrids 4.13a-d were further evaluated for the in vitro antiplasmodial activity to determine the IC50 against NF54 CQS and K1 CQ-resistant (CQR) strains while the moderately potent compounds, the DHPM-mefloquine-triazoles 4.14c, 4.14e and 4.14g were subjected to in vitro IC50 determination against K1 strain. Compounds 4.13a-d with 4-aminoquinoline functionality displayed the highest inhibitions comparable to CQ at both 1 and 5 µM while the remaining compounds in this library, compounds 4.13e-f with the 4-oxyquinoline moiety revealed minimal inhibitions at both concentrations, though higher at 5 µM. Compounds 4.14a-h with the mefloquine moiety showed lower antiplasmodial activity than CQ and the quinoline-derived hybrids 4.13a-h. Amongst the tested hybrids for the IC50 determination, Table 4.4, compounds 4.13a-d displayed good antiplasmodial activity against the CQR K1 strain between 421-567 nM and showed higher activity between 138-245 nM against the NF54 CQS strain while compounds 4.14c, 4.14e and 4.14g have IC50 values greater than 5 µM. Hybrids 4.13a-d also showed reduced Resistance Indices (RI) factor between 2.3-3.6 as compared to CQ with RI factor of 8.5, suggesting that the addition of the DHPM to the quinoline scaffold was able to change the sensitivity of the K1 strain observed. This implies that the hybrids 4.13a-d showed no cross-resistance and are able to reverse resistance in CQR K1 strain of P. falciparum. Thus, compounds 4.13a-d with a triazole linker were able to reverse resistance in P. falciparum as seen from their resistance indices, although with higher IC50 values than CQ. The third series of hybrids, comprising chalcone hybrids 4.21a-h and their 1,3-diarylpropane analogues 4.24a-d, were screened for antiplasmodial activity at 1 and 5 μM with intermediates 4.5e-h, 4.19a,b and 4.22 while CQ was used as control drug. Chalcone was also successfully linked to DHPM via a triazole linker. This was done to investigate the antiplasmodial activity of chalcones and the effects of the DHPM on their hybrids. DHPM-chalcone hybrids generally displayed lower antiplasmodial activities than DHPM-CQ hybrids. Largely, all the 1,3-diarylpropane hybrids showed lower activity than their chalcone-based analogues except for compound 4.24a which showed a better activity than 4.21a at both 1 and 5 µM. In the final series, the in vitro inhibitory activity of the quinoline hybrids 4.33a-c, 4.34, 4.35 and their control analogue 4.30 without the quinoline ring was evaluated against K1 CQ-resistant (CQR) strain of P. falciparum at 1 and 5 µM, using CQ as the reference drug (Figure 4.30 and Table 4.6). The control analogue 4.30 lacking the quinoline moiety showed no inhibition at both 1 and 5 µM. Remarkably, the most active hybrids 4.33a-c were those containing the amide linker between the DHPM and the quinoline ring. This significant difference between their antiplasmodial activities suggests a greater activity in hybrids with the amide linker than those containing the triazole linker (4.34 and 4.35). Also, evident is the reversal ability of the DHPM which is significantly dependent on the aromatic ring of the DHPM. Notably, between the triazole containing compounds 4.34 and 4.35, 4.35 with the 4-amino functionality showed better activity at both concentrations than 4.34 lacking a 4-amino functionality. / Thesis (PhD (Chemistry))--University of Pretoria, 2020. / University of Pretoria / Chemistry / PhD (Chemistry) / Restricted