Download or read book Structural Investigation of Plasmodium Falciparum Chloroquine Resistance Transporter in the Context of Anti Malarial Drug Resistance written by Jonathan Young Kim and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: All CQ resistance-conferring PfCRT isoforms share the K76T mutation, which is widely used as a molecular marker for CQ resistance. Despite the significance in the impact of drug-resistant malaria, a detailed understanding of PfCRT physiological function and the molecular basis of PfCRT-mediated drug resistance have been hampered by a lack of high-resolution structural information. This dissertation describes the first structure of PfCRT and reveals the interaction of drugs with the purified and reconstituted protein. We determined the structure of the 49-kDa PfCRT 7G8, a clinically relevant CQ-resistant isoform found in South America, to 3.2 Å resolution by single-particle cryo-electron microscopy (cryo-EM), in complex with a specific antigen-binding fragment (Fab) to overcome current size limitations in cryo-EM. Our PfCRT structure displays an inward-open conformation, consists of 10 transmembrane (TM) helices with an inverted topology, and has unique elements including two juxtamembrane helices and a highly conserved cysteine-rich loop between TM helix 7 and 8.
Download or read book Investigating Mutability and the Plasmodium Falciparum Chloroquine Resistance Transporter in Drug Resistant Malaria Parasites written by Andrew Hojin Lee and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Malaria persists today as a significant burden for a large part of the world. However, over the past few decades, a concerted effort by governments, non-governmental organizations, researchers, and community health workers worldwide has yielded progress in reducing the deadly impact of this disease. Today, some of these gains are threatened by the rise of antimalarial drug resistance, a recurring problem that has impeded global malaria reduction efforts before. Research on Plasmodium falciprum resistance to the numerous antimalarial compounds used today and in the past has made significant progress on determining which specific mutations modulate drug susceptibility and to what degree they do so. To gain a comprehensive understanding of drug resistance, we need to elucidate how and why it arises. Therefore, it is important to elucidate whether some malaria parasites acquire resistance-conferring mutations faster than others and why the native function of the genetic factors involved lend themselves to modulating drug resistance.
Download or read book The Synthesis and Development of Novel Inhibitors of the Plasmodium Falciparum Chloroquine Resistance Transporter written by Karen Joy Deane and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work detailed in this thesis has been directed towards the synthesis of inhibitors of the Plasmodium falciparum chloroquine resistance transporter (PfCRT). Mutations in this protein are responsible for resistance of the malaria parasite to the antimalarial drug, chloroquine. Inhibitors of PfCRT are known as resistance reversers, and include the antihistamine chlorpheniramine, which has been used as the basis of all the structures that have been developed in this work. Chapter 1 provides an introduction to the disease malaria, caused by Plasmodium parasites. A brief review of antimalarial drugs is presented, with a focus on the most successful of these, chloroquine, and the development of resistance to this drug. Chapter 2 reports the synthetic route to the synthesis of 30 analogues of chlorpheniramine, which includes the preparation and characterisation of 29 previously unreported compounds. Analogues were assayed for and showed the ability to inhibit chloroquine transport by PfCRT, which was correlated to the ability to lower the IC50 of chloroquine in resistant strains of Plasmodium falciparum. The development and synthesis of 10 novel reversed chloroquines is presented in Chapter 3. The targeted structures were analogues of a hybrid structure based on chloroquine and chlorpheniramine, and possessed potent antimalarial activity in addition to their strong activity as inhibitors of PfCRT. 32 new compounds were prepared and characterised. A second generation approach is detailed in the synthesis of 10 reversed sontochins in Chapter 4. The sontochin/chlorpheniramine hybrids showed enhanced activity as inhibitors of PfCRT compared to the previous series. 25 new compounds were synthesised and characterised en route. Chapter 5 describes the synthesis of two chlorpheniramine analogues that have been adapted for inclusion in a reversed tetraoxane. These structures showed no improvement to the activity of chlorpheniramine at inhibiting PfCRT, but possess features for incorporation into an endoperoxide antimalarial. The preparation and characterisation of 20 new compounds is reported.
Download or read book Global Technical Strategy for Malaria 2016 2030 written by World Health Organization and published by World Health Organization. This book was released on 2015-11-04 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: The World Health Organization's Global Technical Strategy for Malaria 2016- 2030 has been developed with the aim to help countries to reduce the human suffering caused by the world's deadliest mosquito-borne disease. Adopted by the World Health Assembly in May 2015 it provides comprehensive technical guidance to countries and development partners for the next 15 years emphasizing the importance of scaling up malaria responses and moving towards elimination. It also highlights the urgent need to increase investments across all interventions - including preventive measures diagnostic testing treatment and disease surveillance- as well as in harnessing innovation and expanding research. By adopting this strategy WHO Member States have endorsed the bold vision of a world free of malaria and set the ambitious new target of reducing the global malaria burden by 90% by 2030. They also agreed to strengthen health systems address emerging multi-drug and insecticide resistance and intensify national cross-border and regional efforts to scale up malaria responses to protect everyone at risk.
Download or read book Treatment and Prevention of Malaria written by Henry M. Staines and published by Springer Science & Business Media. This book was released on 2012-01-06 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Malaria has defeated previous efforts at eradication and remains a massive global public health problem despite being readily preventable and treatable. It is a devastating disease that also extracts huge economic costs from the poorest countries in endemic regions. Starting with an overview of the disease and its current political, financial and technical context, this Milestones in Drug Therapy volume describes the history, chemistry, mechanisms of action and resistance, preclinical and clinical use, pharmacokinetics and safety and tolerability of the current range of antimalarial drugs. There is particular emphasis on artemisinins and related peroxides, as these drugs have now become the frontline treatment for malaria. Next generation antimalarials, molecular markers for detecting resistance, the importance of diagnostics and disease prevention are also covered in detail.
Download or read book Assessment of Long Term Health Effects of Antimalarial Drugs When Used for Prophylaxis written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2020-04-24 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the many who serve in the United States Armed Forces and who are deployed to distant locations around the world, myriad health threats are encountered. In addition to those associated with the disruption of their home life and potential for combat, they may face distinctive disease threats that are specific to the locations to which they are deployed. U.S. forces have been deployed many times over the years to areas in which malaria is endemic, including in parts of Afghanistan and Iraq. Department of Defense (DoD) policy requires that antimalarial drugs be issued and regimens adhered to for deployments to malaria-endemic areas. Policies directing which should be used as first and as second-line agents have evolved over time based on new data regarding adverse events or precautions for specific underlying health conditions, areas of deployment, and other operational factors At the request of the Veterans Administration, Assessment of Long-Term Health Effects of Antimalarial Drugs When Used for Prophylaxis assesses the scientific evidence regarding the potential for long-term health effects resulting from the use of antimalarial drugs that were approved by FDA or used by U.S. service members for malaria prophylaxis, with a focus on mefloquine, tafenoquine, and other antimalarial drugs that have been used by DoD in the past 25 years. This report offers conclusions based on available evidence regarding associations of persistent or latent adverse events.
Download or read book Structure and Functional Differentiation of PfCRT Mutation in Chloroquine Resistance CQR in Plasmodium Falciparum Malaria written by Pratap Parida and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately one million deaths are attributed to malaria every year. Latest reports of multi-drug treatment failure of falciparum malaria underscore the desideratum to understand the molecular substratum of drug resistance. The mutations in the digestive vacuole transmembrane protein Plasmodium falciparum chloroquine resistance transporter (PfCRT) are mainly responsible for chloroquine resistance (CQR) in Plasmodium falciparum. Multiple mutations in the PfCRT are concerned in chloroquine resistance, but the evolution of intricate haplotypes is not yet well understood. P. falciparum resistance to chloroquine is the standard antimalarial drug and is mediated primarily by mutant forms of the PfCRT. In this chapter, we present the mechanism of action of the chloroquine, the structural changes of the gene after the mutations as well as different haplotypes of the PfCRT.
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 Malaria written by Institute of Medicine and published by National Academies Press. This book was released on 1991-02-01 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: Malaria is making a dramatic comeback in the world. The disease is the foremost health challenge in Africa south of the Sahara, and people traveling to malarious areas are at increased risk of malaria-related sickness and death. This book examines the prospects for bringing malaria under control, with specific recommendations for U.S. policy, directions for research and program funding, and appropriate roles for federal and international agencies and the medical and public health communities. The volume reports on the current status of malaria research, prevention, and control efforts worldwide. The authors present study results and commentary on the: Nature, clinical manifestations, diagnosis, and epidemiology of malaria. Biology of the malaria parasite and its vector. Prospects for developing malaria vaccines and improved treatments. Economic, social, and behavioral factors in malaria control.
Download or read book Biochemical Characterisation of the Plasmodium Falciparum Chloroquine Resistance Transporter written by Fadi Baakdah and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The emergence of resistance to commonly used antimalarials significantly hindered global efforts in eliminating malaria and cost the human race losses of lives in millions. Plasmodium falciparum parasites are the most accountable for morbidity and mortality compared to the other species that infect humans. At the present time, artemisinin combination therapies is the approach used in the field to treat malaria infected people and has shown tremendous success. However, resistance to these combinations recently emerged and the pattern of progression and spreading is alarming. Chloroquine once was the first-line drug for treatment of malaria infected people, however, it became in-effective due to the spread of chloroquine resistant strains. Many attributes of chloroquine, at the time when it was effective, were desired and as such the field took on different approaches to revive it. Some people took an approach to withdraw the use of chloroquine for a significant period of time resulting in the emergence of chloroquine sensitive strains. Others looked into modifying the structure of chloroquine in order to make derivatives that would be an improvement on the original. Additionally, others went on to investigate the molecular mechanism by which the parasite confers resistance to chloroquine. Presently, it is well known that mutations in the chloroquine resistance transporter (PfCRT), expressed on the membrane of a lysosome-like organelle in the parasite, the digestive vacuole (DV), are the primary determinants of chloroquine resistance. The physiological role and normal substrates are still matters of speculation but the protein seems to be important for the parasite survival because knockout-PfCRT clones could not be established. The crystal structure was resolved showing the spatial arrangement of the polypeptide chain relative to the juxtaposition of the transmembrane domains forming the central cavity where drugs would interact with PfCRT. Given PfCRT’s role in chloroquine resistance, we thought if chloroquine was slightly modified it would bypass PfCRT resistance mechanism. The first experimental manuscript thesis, we examined the antimalarial activity of 16 novel chloroquine derivatives against chloroquine-sensitive and -resistant Plasmodium falciparum strains. Only two compounds (e.g., AQ-13 and AQ-129) showed effects that surpassed chloroquine’s effect on chloroquine resistant strains that were examined previously but not to the extent of their relationship with PfCRT. Our results demonstrate that AQ-13 and AQ-129 are poor substrates of PfCRT and thus more effective against chloroquine resistant parasites. In the 2nd manuscript, we describe the high resolution characterisation of an antiserum raised against the full-length C-terminal domain of PfCRT. An IgG pool that recognises a de-phosphorylated Ser411 epitope was extracted and used as a tool to monitor the phosphorylation status of residue Ser411. This pool of IgG`s identified the presence of an Ser411 de-phosphorylated homodimer form of PfCRT that does not localise to the DV membrane as does the monomer PfCRT. We also show that PfCRT monomer in chloroquine-sensitive strain (3D7) is significantly more phosphorylated than in chloroquine-resistant strain (Dd2-H) at Ser411, suggesting a possible functional role for this residue in drug resistance. In the last manuscript, we describe the adoption of mammalian HEK-293F cells as a heterologous system to study PfCRT function. Using HEK-293F cells stably expressing PfCRT wild-type and mutants, we show mutant-PfCRT to cause a significant acidification of the lysosomes, relative to wild-type PfCRT. We also provide direct evidence that acidification was mediated through mutant-PfCRT, since using a proline-165-modified mutant-PfCRT clone restored the acidification of lysosomes to wild-type PfCRT levels. Thus, results of this study show for the first time the role of Pro165 in mutant-PfCRT function"--
Download or read book Antimalarial Drug II written by and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 529 pages. Available in PDF, EPUB and Kindle. Book excerpt: The construction of this volume has been guided by two personal convictions. Experience in the field of experimental chemotherapy, both in the pharmaceutical industry and academia, has convinced us that recent quantum technological advances in biochemistry, molecular biology, and immunology will permit and, indeed, necessitate an increasingly greater use of rational drug development in the future than has been the custom up to now. In Part l, therefore, we asked our contributors to provide detailed reviews covering the biology of the malaria parasites and their relation with their hosts, the experimental procedures including culture techniques that are necessary to take a drug from primary screening to clinical trial, and an account of antimalarial drug resistance. Our second conviction is that many research workers are all too loath to learn from the lessons of the past. For this reason we asked the contributors to Part 2 of this volume to review very thoroughly the widely scattered but voluminous literature on those few chemical groups that have provided the antimalarial drugs in clinical use at the present time. Much can be learned from the history of their development and the problems that have arisen with them in man. Some indeed may still have much to offer if they can be deployed in better ways than they are at present. This question has been taken up by several authors.
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 Structure function Analysis of Plasmodium Falciparum Chloroquine Resistance Transporter in Chloroquine Resistance written by Kit-ying Choy and published by . This book was released on 2007 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 World Malaria Report 2018 written by World Health Organization and published by World Health Organization. This book was released on 2019-02-12 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: This year s report shows that after an unprecedented period of success in global malaria control progress has stalled. Data from 2015?2017 highlight that no significant progress in reducing global malaria cases was made in this period. There were an estimated 219 million cases and 435 000 related deaths in 2017. The World malaria report 2018 draws on data from 90 countries and areas with ongoing malaria transmission. The information is supplemented by data from national household surveys and databases held by other organizations.
Download or read book The Malaria Parasite s Chloroquine Resistance Transporter written by Robert Leon Summers and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The malaria parasite's chloroquine resistance transporter: An exploration of its interactions with drugs and of its evolution as a drug transporter Abstract: Initially identified as the primary determinant of chloroquine resistance in the malaria parasite Plasmodium falciparum, mutations in the 'chloroquine resistance transporter' (PfCRT) can influence the parasite's susceptibility to diverse molecules. The ability of PfCRT to affect the activity of so many compounds is likely to be a product of its location at the membrane of the parasite's digestive vacuole - an acidic compartment in which many types of drugs accumulate, act, and/or are activated. The Xenopus laevis oocyte system enables the functional expression of PfCRT and has been used to demonstrate that a mutant isoform of PfCRT mediates the efflux of chloroquine from the vacuole (i.e., away from its site of action), whereas the wild-type protein lacks this activity. However, the evolution of chloroquine transport activity by PfCRT has yet to be explored, and little is known of how PfCRT interacts with diverse compounds. The overarching aim of this study was to understand how mutations in PfCRT confer chloroquine transport activity and alter the parasite's susceptibility to diverse pharmacons. A kinetic analysis of the inhibition of PfCRT-mediated chloroquine transport by verapamil, a compound which partially restores the activity of chloroquine against drug-resistant parasites, was undertaken in the oocyte system. The findings of this work revealed verapamil to be a partial-mixed-type inhibitor of the transporter, and suggested that the mutations required for chloroquine transport introduce multiple substrate-binding sites into PfCRT. A series of complementary assays were then applied to examine the interactions of PfCRT with a range of compounds to identify, and distinguish between, PfCRT substrates and inhibitors. Using the oocyte system, two new classes of compounds were identified as potent inhibitors of the PfCRT-mediated transport of chloroquine. Transgenic parasite lines that are isogenic except for their pfcrt allele were employed, in conjunction with an assay that indirectly detects the transport of drugs out of the parasite's digestive vacuole, to further characterise these compounds. The resulting data revealed that most of these molecules are not substrates of the mutant transporter. Furthermore, parasite proliferation assays demonstrated that the compounds possessed enhanced activities against parasites harbouring mutant PfCRT. Structure-activity relationships were consistent with these compounds binding to multiple points of attachment within PfCRT via lipophilic and electrostatic interactions. Measurements of chloroquine transport via diverse isoforms of PfCRT (as well as by a series of chimeric proteins) were also undertaken in the oocyte system. These analyses revealed that multiple mutational pathways lead to saturable chloroquine transport via PfCRT. The finding that diverse PfCRT variants are all limited in their capacity to transport chloroquine suggests that resistance could be overcome by re-optimising the chloroquine dosage. Moreover, the results of this study indicated that the remodelling of PfCRT for chloroquine transport required a complex reorganisation of interacting residues. These studies support the idea that, in addition to being a mediator of multidrug resistance, PfCRT is itself a viable drug target. Antimalarial therapies could be formulated to exert opposing selection forces upon PfCRT, thereby exploiting a key resistance mechanism and prolonging drug efficacy against this important human pathogen.
Download or read book Drug Targets for Plasmodium Falciparum Historic to Future Perspectives written by Mohammed Tarique and published by Springer Nature. This book was released on with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt:
