Download or read book Characterization of Plasmodium Falciparum Resistance to Novel Drugs written by Sonia Edayé and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Plasmodium falciparum is the deadly protozoan parasite responsible for malaria. Malaria is one of the most important infectious diseases that has been raging for millennia and affecting almost half of the world's population. The treatment regimen that was based on quinoline drugs such as chloroquine (CQ), was efficient for decades. Nowadays, the use of this class of drugs is doomed to failure due to the emergence of quinoline-resistant parasites. Today, artemisinin-based combination therapies (ACTs) are the first-line drugs for uncomplicated falciparum malaria treatment. ACTs improve the cure rate of malaria and thus are seen as efficient treatment against uncomplicated forms of the disease. Despite their efficiency, these drugs are currently facing the development of resistance. PfCRT and PfMDR1, which are membrane transporters, have been shown to be involved in malaria parasites drug resistance. To tackle the inefficiency of existing drugs in regard to the development of resistance, alternative therapies must be discovered. In this thesis, antimalarial activity of novel potential drugs against P. falciparum is assessed and the interaction of these drugs with PfCRT and PfMDR1 is determined. Furthermore, because many ABC transporter genes play a key role in drug resistance, the characterization of an ABC transporter member of the ABCG family in Plasmodium is addressed and its role in drug resistance investigated.In the first part of this thesis, MK571 (a quinoline analogue) activity against P. falciparum parasites is investigated. MK571 is found to be more toxic to most of the CQ-resistant strains than to the CQ-sensitive strains. In addition, we determine that MK571 is not a substrate of PfCRT as are other quinoline drugs, but is instead a substrate of PfMDR1. Therefore, it can be a good complement to existing quinoline drugs in the treatment of uncomplicated malaria. In the second part, novel compound analogues of chloroquine are tested for their antimalarial activity against CQ-sensitive and -resistant parasites. Although chloroquine analogues tested possess the quinoline ring structure of chloroquine, they are less efficient than chloroquine and are not substrates of PfCRT. One of the analogues (3-ICQ) reverses the resistance of CQ-resistant strains to chloroquine and therefore, could be used in combination with chloroquine in cases of CQ-resistant malaria. In the third part of the thesis we conduct the characterization of PfABCG, the sole member of the P. falciparum ABCG family. The characterization study demonstrates that PfABCG is localized on the parasite plasma membrane and is expressed throughout the asexual life cycle of the parasite. In addition, PfABCG is differentially expressed in various Plasmodium strains. This expression does not correlate with the resistance to chloroquine but to the sensitivity of the parasite to an antihistaminic drug named ketotifen. Overall, this thesis sheds light on challenges and understanding of the complex resistance machinery deployed by the P. falciparum parasite from novel drug discovery to characterization of proteins. " --

Download or read book Identification and Characterization of Novel Drug Resistance Loci in Plasmodium Falciparum written by Daria Natalie Van Tyne and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Malaria has plagued mankind for millennia. Antimalarial drug use over the last century has generated highly drug-resistant parasites, which amplify the burden of this disease and pose a serious obstacle to control efforts. This dissertation is motivated by the simple fact that malaria parasites have become resistant to nearly every antimalarial drug that has ever been used, yet the precise genetic mechanisms of parasite drug resistance remain largely unknown. Our work pairs genomics-age technologies with molecular biology, genetics and molecular epidemiology in order to identify and characterize novel genes that contribute to drug resistance in P. falciparum.

Download or read book Characterization and Analysis of Novel Antimalarial Drug Targets Plasmodium Falciparum Phosphatidylinositol Kinases written by Anna Rose Sternberg and published by . This book was released on 2020 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Artemisinin-based combination therapy (ACT) is the first-line treatment recommended for uncomplicated Plasmodium falciparum infections by the World Health Organization (WHO). ACTs are composed of an artemisinin (ART) drug and a longer lasting partner drug, typically with a mechanism of action (MOA) different from ARTs. With the exception of ARTs, there is widespread resistance to all antimalarial drug classes previously recommended for use against P. falciparum. However, the appearance of delayed clearance phenotype (DCP) infections due to reduced ACT efficacy in Southeast Asia [Noedl et al., 2008] threatens our ability to successfully treat multi-drug resistant P. falciparum malaria with ACTs. This also indicates the era of ARTs as leading antimalarial drugs may be reaching an end, so there is desperate need for the development of novel and potent antimalarials for use in next generation therapies.

Download or read book Characterization of Drug resistant Isolates of Plasmodium Falciparum written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Drug resistant Isolates of Plasmodium Falciparum written by and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Saving Lives Buying Time written by Institute of Medicine and published by National Academies Press. This book was released on 2004-09-09 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: For more than 50 years, low-cost antimalarial drugs silently saved millions of lives and cured billions of debilitating infections. Today, however, these drugs no longer work against the deadliest form of malaria that exists throughout the world. Malaria deaths in sub-Saharan Africaâ€"currently just over one million per yearâ€"are rising because of increased resistance to the old, inexpensive drugs. Although effective new drugs called "artemisinins" are available, they are unaffordable for the majority of the affected population, even at a cost of one dollar per course. Saving Lives, Buying Time: Economics of Malaria Drugs in an Age of Resistance examines the history of malaria treatments, provides an overview of the current drug crisis, and offers recommendations on maximizing access to and effectiveness of antimalarial drugs. The book finds that most people in endemic countries will not have access to currently effective combination treatments, which should include an artemisinin, without financing from the global community. Without funding for effective treatment, malaria mortality could double over the next 10 to 20 years and transmission will intensify.

Download or read book Multi drug Resistance in Malaria written by Pritha Sen and published by . This book was released on 2001 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of Drug Resistance Mechanisms in Intact Plasmodium Falciparum infected Red Blood Cells written by Sarah Reiling and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Malaria is a major global health concern, with half of the world's population being at risk of infection. Among the Plasmodium species that infect humans, P. falciparum causes most fatalities. Chloroquine (CQ) was the drug of choice for decades and considered safe, affordable and easy-to-use until resistance emerged. However, the exact mechanism of CQ resistance is not known. CQ is suggested to accumulate in the parasite's digestive vacuole due to its weak base properties, where it exerts its antimalarial action. Several transporters are involved in intracellular distribution of antimalarial drugs. Among them are the P. falciparum chloroquine resistance transporter (PfCRT) and the P. falciparum multidrug resistance 1 transporter (PfMDR1). Both are located in the digestive vacuolar membrane but transport substrates in opposing directions. While PfCRT transports substrates out of the digestive vacuole (DV), PfMDR1 transports substrates into the DV. PfMDR1 contains five polymorphisms that are suggested to be involved in altered drug transport, although the exact role of each amino acid mutation remains unknown. To gain more insight into the transport functions of PfMDR1, variants with different mutation patterns were analyzed using the fluorescent substrate Fluo-4. We found a crucial role for asparagine (N) at residue 1042 in Fluo-4 transport, while substitution with aspartic acid (D) abolished all transport. In addition, we showed an association of the PfMDR1 N1042D mutation with increased mefloquine but decreased quinine sensitivity. Furthermore, competition studies of Fluo-4 with the antimalarial drugs chloroquine, mefloquine and quinine showed distinct transport inhibition patterns for parasites of different genetic background. This can be used as a tool to evaluate parasite susceptibility to antimalarial drugs.Next, we investigated the mechanism of resistance to CQ in more detail. We showed that parasite survival is higher in CQ-resistant strains compared to CQ-sensitive strains in the initial 10 hours after exposure to equally lethal CQ concentrations. Moreover, dark cytosolic structures appeared in CQ-sensitive strains that were later confirmed as hemozoin-containing compartments surrounded by a membrane bilayer. Leakage of hemozoin crystals out of the DV was ruled out since lysis of the digestive vacuolar membrane did not occur during that time frame. These data suggest that CQ resistance is not linked to reduced drug concentrations in the DV alone, and additional regulatory mechanisms in the parasite must play a crucial role during CQ exposure.To pursue these findings, a commercially available fluorescent tagged CQ analogue, LynxTagTM-CQ-GREEN (CQ-GREEN), was examined for its suitability in studying CQ transport and intracellular drug accumulation. While CQ-GREEN was half as effective in parasite killing of CQ-sensitive strains compared to unmodified CQ, no significant changes in parasite killing were observed in CQ-resistant strains. However, live cell imaging showed that CQ-GREEN accumulated in the parasite cytosol and not the DV. These results show for the first time a potential target for a CQ analogue outside the digestive vacuole. Moreover, intracellular CQGREEN uptake rates were reduced in CQ-resistant strains compared to CQ-sensitive strains. This, too, suggests that CQ-resistant strains must have evolved a regulatory mechanism to decrease intracellular CQ accumulation.The results presented in this thesis expand our understanding of substrate transport by PfMDR1. Furthermore, a novel phenotype was described for CQ-sensitive strains upon drug exposure that was not seen in CQ-resistant strains. These data suggest that altered regulatory mechanisms play a role in CQ resistance and are likely located in the parasite cytosol." --

Download or read book Characterization of Various Effects of Crisis Form Induction on Plasmodium Falciparum in Vitro written by Joseph M. Carlin and published by . This book was released on 1985 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Discovery and Characterization of a Novel Class of Metabolic Regulators in the Malaria Parasite Plasmodium Falciparum written by Ann M. Guggisberg and published by . This book was released on 2016 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: The malaria parasite, Plasmodium falciparum, infects hundreds of millions of people per year and causes hundreds of thousands of deaths. Within the host red blood cell, the parasite relies on glycolysis for energy and synthesis of essential biomolecules. One such anabolic fate of glucose is the synthesis of isoprenoids, a broad and essential class of compounds that participate in a variety of cellular functions. In the face of ever-evolving drug resistance, new inhibitors and better understanding of parasite metabolism are required. The antibiotic fosmidomycin (FSM) targets the methylerythritol phosphate pathway for isoprenoid synthesis and is a well-validated inhibitor of P. falciparum growth. A forward selection for FSM resistance generated a number of parasite strains with increased drug tolerance. We identify mutations in two members of the haloacid dehalogenase-like hydrolase (HAD) superfamily, PfHAD1 and PfHAD2, as causal for resistance. Enzymatic characterization and metabolic profiling reveal that these mutations are deleterious and confirm the role of PfHAD1 and PfHAD2 as novel negative regulators of glucose and isoprenoid metabolism. Despite their homology and shared role in FSM resistance, PfHAD1, a sugar phosphatase, and PfHAD2, a purine nucleotidase, appear to mediate FSM resistance via distinct enzymatic mechanisms. To further understand the role of PfHADs as metabolic regulators, we harness a growth defect in FSM-resistant PfHAD2 mutants to select for suppressors of FSM resistance. We identify suppressor mutations in the key glycolytic enzyme phosphofructokinase (PfPFK9) and describe the effect of these mutations on enzyme function and parasite metabolism. Given its safety in humans and its specificity as a MEP pathway inhibitor, FSM is a strong candidate for clinical development and is currently being evaluated in clinical trials as part of an antimalarial combination therapy. Unfortunately, previous studies have observed high rates of recrudescence following FSM treatment when paired with the antibiotic clindamycin (CLN). To understand whether any genetic changes correlate with recrudescence, we performed whole genome sequencing on patient parasite populations before and after recrudescence. We demonstrate the use of a selective amplification method to amplify and sequence parasite genomes from blood spots. Our genotyping does not reveal any genetic changes responsible for recrudescence, but rather support the hypothesis that FSM-CLN treatment failure is due to formulation or partner drug selection. We encourage further development of FSM and other MEP pathway inhibitors as antimalarial therapies.

Download or read book Mechanisms of Drug Resistance in Plasmodium Falciparum written by and published by . This book was released on 1994 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: Malaria continues as a major health threat throughout the tropical world and potential demand for antimalarials is higher than for any other medication yet the world faces a crisis--drug resistance is emerging and spreading faster than drugs are being developed and the flow in the pipeline of new drugs has all but stopped. This represents a particular threat to the US military. In a short time there may be parts of the world where no effective antimalarial drug is available. The recent emergence of multidrug resistant malaria parasites has intensified this problem. The goal of this work is to use a molecular genetic approach in the investigation of mechanisms of drug resistance and subsequently to use this information in the identification and development of new antimalarial drugs. These studies were initiated based on the observation that one mechanism of drug resistance in P. falciparum may be similar to multidrug resistance in cancer. During this work, we identified and fully characterized two mdr-like genes in P. falciparum, pfmdrl and pfmdr2 and have found an association with the amplification and over expression of one of these genes, pfmdrl with mefloquine resistance and multidrug resistant parasites both in laboratory derived and field isolated strains of Plasmodium falciparum. As a next step in this work, we have initiated the development methods of functional analysis which are critical both to developing and testing new chemotherapeutic interventions. Malaria, Drug resistance, Recombinant DNA, Tropical disease, Infectious disease.

Download or read book Functional Characterization of Cytochrome B5 Reductase and Its Electron Acceptor Cytochrome B5 in Plasmodium Falciparum written by Lucio Malvisi and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Malaria is a disease of major public health importance, killing approximately one million people and causing about 250 million cases of fever annually. It mostly affects children under the age of five and pregnant women in many developing countries, making it a prominent issue in international health and maternal and child health. The most aggressive form of malaria is caused by the parasite Plasmodium falciparum which is responsible for 80% of infections and 90% of deaths from malaria, and is most prevalent in sub-Saharan Africa. Public Health interventions include the implementation of prevention programs, health education, and chemotherapy. The latter has experienced multiple problems in the past years whereby resistance of the parasite to the available drugs has emerged, rendering the majority of them ineffective. Furthermore, the high cost of those drugs represents a major obstacle to their dispensation in areas of the world where the affected people are often the less fortunate. The enzyme Cytochrome b5 Reductase (cb5r) and its electron acceptor Cytochrome b5 (cb5) play a role in fatty acid elongation, cholesterol biosynthesis, and cytochrome P450-mediated detoxification of xenobiotics. Therefore, these proteins are suitable as potential novel drug targets for malaria. These two proteins have been thoroughly studied in mammals but have to be characterized in microorganisms such as fungi and parasites, including Plasmodium falciparum. It is important to note that plant cb5r has been identified as a novel herbicidal target. Considering the close phylogenetic relationship between plant cb5r and Plasmodium falciparum cb5r, we conclude that these plant inhibitors may also serve as promising candidates for a new class of antimalarial drugs against the parasite. In this project, we want to obtain the biochemical and enzymatic characterization of cb5r and cb5 in order to establish whether these two proteins represent potential novel drug targets in Plasmodium falciparum malaria. This initial work may lead to the development of novel drugs which will consequently affect the field of public health with respect to drug delivery, drug resistance, and drug chemotherapy.

Download or read book Economic Analysis of Malaria Control in Sub Saharan Africa written by Catherine Cavallaro Goodman and published by . This book was released on 2000 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Antimalarial Drug Resistance in Southern Mozambique written by and published by . This book was released on 2004 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Identification and Characterization of Novel Inhibitors of Plasmodium Falciparum Hemozoin Formation written by Margaret Andrews Rush and published by . This book was released on 2009 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: We've conducted a series of experiments to determine if the seventeen CFHCS hits inhibit P. falciparum growth by inhibiting heme crystallization, including heme binding assays, structure activity relationship studies, investigations of drug sensitivity in multidrug resistant parasites and experiments to determine if hemoglobin protease inhibitors antagonize the activity of the CFHCS hits. Additionally, we conducted phenotypic studies to determine if these compounds changed parasite morphology, especially the morphology of the hemozoin crystal and parasite food vacuole. Each of these assays has been previously described to support the mechanism of action of the quinoline antimalarials. Through these experiments we were able to rule out BCM as the mechanism of action of at least one compound and provide strong evidence to support this mechanism for nine compounds. Our finding also have interesting implications for the development of drugs which act by inhibiting BCM, one of the most important drug targets in the malaria parasite.

Download or read book Biochemical and Structural Characterization of Novel Drug Targets Regulating Polyamine Biosynthesis in the Human Malaria Parasite Plasmodium Falciparum written by Marni Williams and published by . This book was released on 2011 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Drug Resistance of Plasmodium Falciparum Malaria written by Denise Patricia Mawili-Mboumba and published by . This book was released on 2003 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: