A Research Report Submitted to the School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the Degree of Master of Science in Medicine in Tropical Diseases (Epidemiology and Biostatistics Option). Johannesburg, January 2001 / Background: increasing spread of drug resistance among Plasmodium falciparum poses a serious threat to malaria treatment. The situation is complicated not only because new drugs are expensive and slow in development but also because they must be effective, preferably have a novel method of action, with an acceptable level of adverse effects, and be deployed in such a way as to prolong their use. / IT2018

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Selon les estimations de l'OMS, le bilan mondial du paludisme a atteint 212 millions de cas et 429 000 décèsen 2015 (OMS, 2016). Cette gravité est principalement due à Plasmodium falciparum. A l’heure actuelle, P. falciparum présente des résistances à tous les antipaludiques donnés en monothérapie.Par conséquent, pour réduire le risque d’échec thérapeutique, l'OMS a recommandé depuis 2001 l’utilisation de bithérapie, notamment d'Artemisinin Combination Therapy (ACT), comme traitement de première intention.Les ACT sont composés essentiellement d’un dérivé d’artéminisine, à demi-vie courte et un autre antipaludique à demi-vie longue, connu en monothérapie.Le parasite a également montré des signes de résistance aux ACT, principalement en Asie du Sud-est, menaçant les programmes d’éradications contre le paludisme.La découverte de nouveaux composés à activité antipaludique ou de nouvelles procédures de traitement sont urgentes.La valorisation d’anciennes molécules est également au cœur des études afin d’améliorer notamment leur biodisponibilité et réverser les mécanismes de résistance du parasite. Ainsi, des études prouvent l’intérêt de l’utilisation de nanotechnologies pour l’amélioration de l’efficacité d’antipaludiques. L’atovaquone en est un exemple, cette modification a notamment permis d’améliorer sa biodisponibilité. Notre étude a porté sur une de ces formulations, de l’atovaquone encapsulée dans une nanoémulsion cationique (NE) appelée ATQ. Une deuxième génération a ensuite été testée par association d’oligonucléotides antisens anti-ARNm de topoisomérase II(AST) de P. falciparum. En effet, des stratégies antisens thérapeutiques font leur preuve en santé humaine et présentent un intérêt croissant en parasitologie. Les NE/AST ont montré une activité anti-palustre spécifique contre P. falciparum in vitro. Leur spécificité a permis d’aboutir à l’arrêt du cycle cellulaire et une forte diminution du taux d’ARNm de la topoisomérase II. Ce phénomène a montré être dépendant de l’action de la RNase H. Un effet synergique de ces NE/AST a également été montré en association avec la chloroquine, l’atovaquone et la dihydroartémisinine sur une souche sensible de P. falciparum et des souches résistantes aux antipaludiques précédemment cités.L’ATQ a également montré une forte efficacité sur une souche résistante à l’atovaquone d’un facteur 5. En présence d’ATQ, la mitochondrie a rapidement été altérée conduisant à une mort précoce du parasite. Un traitement à l’ATQ a abouti à la guérison de souris Swiss infectée par P. berghei après deux injections en i.v. en 5 jours. Enfin, l’ATQ/AST a montré une efficacité in vitro contre P. falciparum et P. berghei in vivo. Un test de cytoadhérance des hématies parasitées a des cellules endothéliales a révélé un fort pourvoir d’inhibition de la cytoadhérance de l’ATQ/AST.Un résultat prometteur dans le cadre de traitement du neuropaludisme. / According to the estimations of theWHO, in 2015, 212million cases ofmalariahave been reported(WHO,2016). These figuresmakemalariathe most deadlyparasitic diseasein the world, with429.000deaths per year. Some treatments against Plasmodium falciparum exist. However, no really good treatment option can be found in monotherapy due to the resistance emergency. Therefore To reduce the risk of resistance, WHO has recommended since 2001 combination therapies, which is basically an Artemisinin Combined Therapy (ACT), as first-line treatment. The main problem of commercialized bi-therapy is that they are composed of two molecules with individual resistance which leaded to the emergence of resistance to the latest ACTs such as a dihydroartemisinin /piperaquine combinationmainly in South-East Asia.Thus the use of new therapeutic combination strategy that can bypass the parasites' mechanisms of resistance is urgent to effectively treat malaria. As the pathway from drug discovery to drug commercialization is both long and very expensive, it is essential to develop ways to improve existing antimalarial treatments. In the first place it’s necessary to find a new antimalarial formulation based on an already commercialized drug to modify its biodisponibility and its mechanism of action in order to revert the resistance. In the second place its necessary to associate this formulation with a novel none commercialized antimalarial strategy such as the antisens oligonucleotides already usedinhumanhealth. In our lab we have developed nanoemulsions containing atovaquone and antisense oligonucleotides anti topoisomerase II against P. falciparum.Nanoemulsionsvectoringantisens oligonucleotidesandused againstP. falciparum topoisomerase II(NE/AST) showed encouraging anti-parasite killing results.Additionalresultshave showna synergistic in vitro effectwithantimalarial drugs(chloroquine, dihydroartemisinin and atovaquone) in sensitive and resistances strains. Moreover NE/ASTrestricted Topoisomerase II gene expression and blocked the cell cycle in G2/M phase leading to parasite’s death by mitophagy.As Drug delivery systemscan improve the efficacy ofcommon antimalarial drugs by delivering the drug to its target, while protecting it from degradation in biological environment and increasing its biodisponibility, our nanoemulsions containing atovaquone (ATQ) leaded to reversion of atovaquone resistance with 5 fold decrease in its IC50. Observations made with confocal microscopy have shown mitochondrial alteration after ATQ treatment.Our novel and original bi-therapy is focused on the association ofATQ with NE/AST (ATQ/AST).We obtained an IC50 8-fold lower than atovaquone’s IC50with total inhibition of parasites’ capacity to reinfect new red blood cells. A cytoadherence test of parasitized erythrocytes to endothelial cells revealed a strong capacity of cytoadherence inhibition of ATQ / AST, a promising result in the treatment of cerebral malaria.

In order to reduce malaria prevalence worldwide, a better understanding of parasite transmission and the effect of drug resistance is needed. The effect of drug resistance on malaria transmission has been examined for some drugs, but not for mitochondrial inhibitors such as atovaquone and the current basis of malaria therapy, artemisinin. Therefore, the goal of this study was to produce gametocytes, the life cycle stage that transmits from mosquito to human, in several different drug resistant patient isolates as well as to determine the effect of drug resistance on gametocyte development and transmission. Previous studies have shown that the mutation that confers resistance to atovaquone, a common antimalarial, occurs de novo after treatment and transmission of this resistance is not seen in the field. Therefore, to determine whether or not the resistance mutation can be transmitted, mosquito-feeding experiments were conducted using atovaquone resistant parasites and resulting oocyst DNA was analyzed. In addition to these atovaquone studies, artemisinin resistant gametocytes were also grown in vitro and drug pressure was added to determine if resistance mechanisms affect gametocyte development. This study is the first examine gametocyte development in these resistant strains and the first to report that transmission of the atovaquone resistant mutation may be possible. However, data is currently inconclusive on the effect of artemisinin resistance on gametocyte development.

The malaria parasite Plasmodium falciparum is responsible for about 500,000 deaths a year and is evolving resistance to the front-line treatment of artemisinin-based combination therapy. Resistance is currently confined to South East Asia, however millions of lives will be at risk if resistance spreads to Africa. Understanding the mechanism of resistance to artemisinins would aid containment strategies to prevent the spread of artemisinin resistance. There is also an urgent need to accelerate drug discovery since drug resistance has already been documented to all existing antimalarials. Here, I report on our efforts to understand the function of the gene k13, the gene with the strongest association with artemisinin resistance, and the potential genetic mechanisms associated with resistance to atovaquone, another widely used antimalarial. To precisely study the transcriptome characteristics of an isogenic k13 dysregulation mutant and wild type strain, I developed a new computational algorithm called Dephasing Identifier (DI) that is capable of identifying the genes dysregulated in cell cycle shifts. DI is designed to solve the problem of pinpointing important patterns in complex genomics data with temporal sequences that cannot be resolved by standard pair-wise comparison methods, by using an innovative method that leverages external reference data for systematic comparisons. In the k13 study, I demonstrated that the algorithm identifies co- regulated gene sets that have consistent annotated functions. The DI algorithm successfully identified aberrantly early DNA replication as the driving process of transcriptome changes in the mutant. To understand genome-wide changes that occurred in a set of atovaquone resistance stains, I analyzed whole genome sequencing data previously generated for a P. falciparum strain that underwent in vitro atovaquone selection to create atovaquone resistant strains. I systematically analyzed the genomes of these strains to search for significant genetic changes associated with atovaquone resistance; and used stringent criteria to identify genes involved in regulating transcription and protein modifications as acquiring non- synonymous mutations. Additionally, copy number variations in plasmepsin genes, a family known to be involved in resistance, were found in the resistant strains. In summary, genomics and transcriptomics technologies can be used to rapidly identify resistance mechanisms allowing for faster adjustment of current containment strategies. Future research on the critical targets identified in this study can aid new drug discovery efforts and novel control strategies.

STAT3 is a critical oncogenic transcription factor, but how it becomes aberrantly activated in cancer is unclear. We have discovered a new pathway whose loss is associated with persistent STAT3 activation in human cancer. We found that the tumor suppressor miR-146b is a direct STAT3 target gene in normal breast epithelial cells. However, STAT regulation of miR-146b is subverted in tumor cells and is suppressed by promoter methylation, which is increased in primary breast cancers. Moreover, we show that miR-146b inhibits NF-κB-dependent IL-6 production, IL-6-dependent STAT3 activation, and IL-6/STAT3-driven functional phenotypes, thereby establishing a negative feedback loop. In addition, miR-146b expression appears to be deregulated in tumors with the highest levels of activated STAT3, and is positively correlated with patient survival. Our results indicate a new mechanism of crosstalk between STAT3 and NF-κB relevant to constitutive STAT3 activation in malignancy and the role of inflammation in oncogenesis.

A malária é um problema de saúde mundial. Esta doença é causada pela infecção dos eritrócitos com o protozoário do gênero Plasmodium. A atovaquona (ATQ) é um análogo estrutural da coenzima Q, usado como monoterapia ou em combinação com proguanil no tratamento da malária. A incorporação de fármacos de reduzida hidrossolubilidade, como a ATQ, em veículos tradicionais, é frequentemente limitada devido a razões de solubilidade. Neste contexto, nanoemulsões oferecem uma alternativa promissora devido a sua efetividade na solubilização de fármacos, aumentando a eficácia, e reduzindo os efeitos adversos. Assim, o objetivo deste trabalho foi desenvolver nanoemulsões catiônicas contendo ATQ para administração intravenosa. Nanoemulsões compostas de ATQ, triglicerídeos de cadeia média, lecitina de gema de ovo, 1,2-dioleoil-3-trimetil amônio propano (DOTAP), glicerol, polissorbato 80 e água foram obtidas pelo método de emulsificação espontânea. Este método levou à obtenção de nanoemulsões monodispersas com um diâmetro médio de aproximadamente 200 nm, como confirmado pela microscopia eletrônica de transmissão. O potencial  das nanoemulsões foi positivo (> 30 mV em pH 5). Um método isocrático de cromatografia líquida de fase reversa foi validado para quantificar ATQ. O método foi específico, linear, preciso e exato para a quantificação de ATQ. O teor de fármaco para todas as formulações foi próximo a 95%. A ATQ liberada a partir das nanoemulsões foi avaliada em dois meios diferentes (RPMI-1640 + 0,5% albumina ou PBS + 0,5% polissorbato 80) após a separação de ATQ livre através das membranas de ultrafiltração (poro de 0,1m). Independente do meio utilizado, ATQ foi progressivamente liberada a partir das formulações em função do fator de diluição e permaneceu constante em função do tempo. A maior liberação de ATQ foi observada para nanoemulsões contendo polissorbato 80 e no meio contendo este tensoativo não iônico em condições sink. O diâmetro das nanoemulsões permaneceu inalterado nas condições de liberação para nanoemsulões contendo polissorbato 80 enquanto uma inversão do - potencial de valores positivos para negativos foi detectado. Tais formulações mostraram uma inibição do crescimento do parasita in vitro frente a cepas de P. falciparum resistentes à ATQ. / Malaria is a global public health problem. This disease is caused by infection of red blood cells with protozoan parasites of the genus Plasmodium. Atovaquone (ATQ) is a structural analogue of coenzyme Q used as monotherapy or in combination with proguanil in malaria treatment. The incorporation of poorly-water soluble drugs such as ATQ in well-accepted vehicles is frequently limited due to solubility reasons. In this context, nanoemulsions offer an appealing alternative due to their effectiveness in drug solubilization, improved efficacy, and reduced side effects. The main purpose of this study was to develop cationic nanoemulsions containing ATQ for intravenous administration. Nanoemulsions composed of ATQ, medium chain triglycerides, egg lecithin, dioleoyl trimethylammonium propane (DOTAP), glycerol, polysorbate 80 and water were obtained by means of spontaneous emulsification. This procedure led to obtaining monodisperse nanoemulsions with mean droplet size of approximately 200 nm, as attested by transmission electron microscopy. - potential of nanoemulsions was positive (> 30mV at pH 5). An isocratic reversed – phase liquid chromatography method was validated for ATQ quantification. The method was specific, linear, precise, and accurate for ATQ quantification. The drug content in all formulations was close 95%. The ATQ release from nanoemulsions was evaluated in two different media (RPMI-1640 + 0.5% albumin or PBS + 0.5% polysorbate 80) after separation of free ATQ on ultrafiltration membranes (cut off 0.1μm). Whatever the media used, ATQ was progressively released from formulations upon the dilution ratio and remained constant over time. A higher release of ATQ was observed for nanoemulsions containing polysorbate 80 and in the media containing this non-ionic surfactant in sink conditions. The droplet size of nanoemulsions remained unchanged in the release conditions for nanoemulsions containing polysorbate 80 whereas an inversion of the -potential from positive to negative values was detected. Such formulations showed in vitro an inhibition of parasite growth against an ATQ-resistant P. falciparum strain.

L'apparition récurrente de Plasmodium falciparum résistant aux antipaludiques est un obstacle majeur au contrôle du paludisme. Introduite en 2000, une nouvelle association très bien tolérée, l'atovaquone-proguanil est rapidement devenue le traitement de choix des accès palustres simples dans certains hôpitaux français. Ce travail de recherche avait pour objectif d'approfondir les connaissances sur la résistance à cette association. Nous n'avons détecté aucune résistance naturelle à l'atovaquone-proguanil en Afrique de l'Ouest et dans l'Océan Indien parmi 477 isolats. La majorité des rechutes précoces sont liées à une malabsorption des principes actifs alors que les échecs tardifs sont liés à la présence de parasites hautement résistants in vitro présentant, au moment de la rechute, une mutation au niveau du codon 268 du cytochrome b (Y268S ou Y268C) sans augmentation du nombre de copies de ce gène, évalué par PCR en temps réel à 16 ± 9 copies par parasite. Le séquençage du génome mitochondrial et l'analyse de marqueurs microsatellites chromosomiques des parasites isolés avant et après la rechute parasitaire montrent que la mutation associée à cette résistance est apparue indépendamment chez chacun des six patients en échec étudiés. L'atovaquone-proguanil est efficace pour le traitement des voyageurs avec moins de 0,1% de résistance. Le risque actuel de dispersion des résistances est négligeable puisqu'elles émergent chez des patients traités hors de zone de transmission. Par contre, si cette association devait être déployée en zone d'endémie, il serait indispensable de la combiner avec d'autres molécules.

A malária é um problema de saúde mundial. Esta doença é causada pela infecção dos eritrócitos com o protozoário do gênero Plasmodium. A atovaquona (ATQ) é um análogo estrutural da coenzima Q, usado como monoterapia ou em combinação com proguanil no tratamento da malária. A incorporação de fármacos de reduzida hidrossolubilidade, como a ATQ, em veículos tradicionais, é frequentemente limitada devido a razões de solubilidade. Neste contexto, nanoemulsões oferecem uma alternativa promissora devido a sua efetividade na solubilização de fármacos, aumentando a eficácia, e reduzindo os efeitos adversos. Assim, o objetivo deste trabalho foi desenvolver nanoemulsões catiônicas contendo ATQ para administração intravenosa. Nanoemulsões compostas de ATQ, triglicerídeos de cadeia média, lecitina de gema de ovo, 1,2-dioleoil-3-trimetil amônio propano (DOTAP), glicerol, polissorbato 80 e água foram obtidas pelo método de emulsificação espontânea. Este método levou à obtenção de nanoemulsões monodispersas com um diâmetro médio de aproximadamente 200 nm, como confirmado pela microscopia eletrônica de transmissão. O potencial  das nanoemulsões foi positivo (> 30 mV em pH 5). Um método isocrático de cromatografia líquida de fase reversa foi validado para quantificar ATQ. O método foi específico, linear, preciso e exato para a quantificação de ATQ. O teor de fármaco para todas as formulações foi próximo a 95%. A ATQ liberada a partir das nanoemulsões foi avaliada em dois meios diferentes (RPMI-1640 + 0,5% albumina ou PBS + 0,5% polissorbato 80) após a separação de ATQ livre através das membranas de ultrafiltração (poro de 0,1m). Independente do meio utilizado, ATQ foi progressivamente liberada a partir das formulações em função do fator de diluição e permaneceu constante em função do tempo. A maior liberação de ATQ foi observada para nanoemulsões contendo polissorbato 80 e no meio contendo este tensoativo não iônico em condições sink. O diâmetro das nanoemulsões permaneceu inalterado nas condições de liberação para nanoemsulões contendo polissorbato 80 enquanto uma inversão do - potencial de valores positivos para negativos foi detectado. Tais formulações mostraram uma inibição do crescimento do parasita in vitro frente a cepas de P. falciparum resistentes à ATQ. / Malaria is a global public health problem. This disease is caused by infection of red blood cells with protozoan parasites of the genus Plasmodium. Atovaquone (ATQ) is a structural analogue of coenzyme Q used as monotherapy or in combination with proguanil in malaria treatment. The incorporation of poorly-water soluble drugs such as ATQ in well-accepted vehicles is frequently limited due to solubility reasons. In this context, nanoemulsions offer an appealing alternative due to their effectiveness in drug solubilization, improved efficacy, and reduced side effects. The main purpose of this study was to develop cationic nanoemulsions containing ATQ for intravenous administration. Nanoemulsions composed of ATQ, medium chain triglycerides, egg lecithin, dioleoyl trimethylammonium propane (DOTAP), glycerol, polysorbate 80 and water were obtained by means of spontaneous emulsification. This procedure led to obtaining monodisperse nanoemulsions with mean droplet size of approximately 200 nm, as attested by transmission electron microscopy. - potential of nanoemulsions was positive (> 30mV at pH 5). An isocratic reversed – phase liquid chromatography method was validated for ATQ quantification. The method was specific, linear, precise, and accurate for ATQ quantification. The drug content in all formulations was close 95%. The ATQ release from nanoemulsions was evaluated in two different media (RPMI-1640 + 0.5% albumin or PBS + 0.5% polysorbate 80) after separation of free ATQ on ultrafiltration membranes (cut off 0.1μm). Whatever the media used, ATQ was progressively released from formulations upon the dilution ratio and remained constant over time. A higher release of ATQ was observed for nanoemulsions containing polysorbate 80 and in the media containing this non-ionic surfactant in sink conditions. The droplet size of nanoemulsions remained unchanged in the release conditions for nanoemulsions containing polysorbate 80 whereas an inversion of the -potential from positive to negative values was detected. Such formulations showed in vitro an inhibition of parasite growth against an ATQ-resistant P. falciparum strain.

A malária é um problema de saúde mundial. Esta doença é causada pela infecção dos eritrócitos com o protozoário do gênero Plasmodium. A atovaquona (ATQ) é um análogo estrutural da coenzima Q, usado como monoterapia ou em combinação com proguanil no tratamento da malária. A incorporação de fármacos de reduzida hidrossolubilidade, como a ATQ, em veículos tradicionais, é frequentemente limitada devido a razões de solubilidade. Neste contexto, nanoemulsões oferecem uma alternativa promissora devido a sua efetividade na solubilização de fármacos, aumentando a eficácia, e reduzindo os efeitos adversos. Assim, o objetivo deste trabalho foi desenvolver nanoemulsões catiônicas contendo ATQ para administração intravenosa. Nanoemulsões compostas de ATQ, triglicerídeos de cadeia média, lecitina de gema de ovo, 1,2-dioleoil-3-trimetil amônio propano (DOTAP), glicerol, polissorbato 80 e água foram obtidas pelo método de emulsificação espontânea. Este método levou à obtenção de nanoemulsões monodispersas com um diâmetro médio de aproximadamente 200 nm, como confirmado pela microscopia eletrônica de transmissão. O potencial  das nanoemulsões foi positivo (> 30 mV em pH 5). Um método isocrático de cromatografia líquida de fase reversa foi validado para quantificar ATQ. O método foi específico, linear, preciso e exato para a quantificação de ATQ. O teor de fármaco para todas as formulações foi próximo a 95%. A ATQ liberada a partir das nanoemulsões foi avaliada em dois meios diferentes (RPMI-1640 + 0,5% albumina ou PBS + 0,5% polissorbato 80) após a separação de ATQ livre através das membranas de ultrafiltração (poro de 0,1m). Independente do meio utilizado, ATQ foi progressivamente liberada a partir das formulações em função do fator de diluição e permaneceu constante em função do tempo. A maior liberação de ATQ foi observada para nanoemulsões contendo polissorbato 80 e no meio contendo este tensoativo não iônico em condições sink. O diâmetro das nanoemulsões permaneceu inalterado nas condições de liberação para nanoemsulões contendo polissorbato 80 enquanto uma inversão do - potencial de valores positivos para negativos foi detectado. Tais formulações mostraram uma inibição do crescimento do parasita in vitro frente a cepas de P. falciparum resistentes à ATQ. / Malaria is a global public health problem. This disease is caused by infection of red blood cells with protozoan parasites of the genus Plasmodium. Atovaquone (ATQ) is a structural analogue of coenzyme Q used as monotherapy or in combination with proguanil in malaria treatment. The incorporation of poorly-water soluble drugs such as ATQ in well-accepted vehicles is frequently limited due to solubility reasons. In this context, nanoemulsions offer an appealing alternative due to their effectiveness in drug solubilization, improved efficacy, and reduced side effects. The main purpose of this study was to develop cationic nanoemulsions containing ATQ for intravenous administration. Nanoemulsions composed of ATQ, medium chain triglycerides, egg lecithin, dioleoyl trimethylammonium propane (DOTAP), glycerol, polysorbate 80 and water were obtained by means of spontaneous emulsification. This procedure led to obtaining monodisperse nanoemulsions with mean droplet size of approximately 200 nm, as attested by transmission electron microscopy. - potential of nanoemulsions was positive (> 30mV at pH 5). An isocratic reversed – phase liquid chromatography method was validated for ATQ quantification. The method was specific, linear, precise, and accurate for ATQ quantification. The drug content in all formulations was close 95%. The ATQ release from nanoemulsions was evaluated in two different media (RPMI-1640 + 0.5% albumin or PBS + 0.5% polysorbate 80) after separation of free ATQ on ultrafiltration membranes (cut off 0.1μm). Whatever the media used, ATQ was progressively released from formulations upon the dilution ratio and remained constant over time. A higher release of ATQ was observed for nanoemulsions containing polysorbate 80 and in the media containing this non-ionic surfactant in sink conditions. The droplet size of nanoemulsions remained unchanged in the release conditions for nanoemulsions containing polysorbate 80 whereas an inversion of the -potential from positive to negative values was detected. Such formulations showed in vitro an inhibition of parasite growth against an ATQ-resistant P. falciparum strain.