Genetically Determined Response to Artemisinin Treatment in Western Kenyan Plasmodium falciparum Parasites.
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ABSTRACT:
SUBMITTER: Chebon LJ
PROVIDER: S-EPMC5017781 | biostudies-literature | 2016
REPOSITORIES: biostudies-literature
Publications
Genetically Determined Response to Artemisinin Treatment in Western Kenyan Plasmodium falciparum Parasites.
Chebon Lorna J LJ Ngalah Bidii S BS Ingasia Luicer A LA Juma Dennis W DW Muiruri Peninah P Cheruiyot Jelagat J Opot Benjamin B Mbuba Emmanuel E Imbuga Mabel M Akala Hoseah M HM Bulimo Wallace W Andagalu Ben B Kamau Edwin E
PloS one 20160909 9
Genetically determined artemisinin resistance in Plasmodium falciparum has been described in Southeast Asia. The relevance of recently described Kelch 13-propeller mutations for artemisinin resistance in Sub-Saharan Africa parasites is still unknown. Southeast Asia parasites have low genetic diversity compared to Sub-Saharan Africa, where parasites are highly genetically diverse. This study attempted to elucidate whether genetics provides a basis for discovering molecular markers in response to ...[more]
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Project description:BackgroundStudies in Southeast Asia reported a strong relationship between polymorphisms at the propeller domain of the Kelch 13 (K13) protein encoded by the Plasmodium falciparum k13 (pfk13) gene and delayed parasite clearance after artemisinin treatment. In Africa, P. falciparum remains susceptible and combination therapy regimens which include an artemisinin component display good efficacy. Using quantitative real-time PCR (qPCR), sub-microscopic persistence of P. falciparum has previously been reported in one-third of children treated with artemisinin combination therapy (ACT) in western Kenya. In this study, further investigation was made to evaluate whether these sub-microscopic residual parasites also harbour mutations at the propeller region of pfk13 and whether the mutations, if any, affect treatment outcome.MethodsThe pfk13 propeller domain was genotyped in DNA samples obtained in 2009 from Kenyan children treated with artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP). Paired samples at pre-treatment (day 0) and day of treatment failure (day 28 or 42) for 32 patients with documented recurrent parasitaemia were available for genotyping. Additional day 3 DNA samples were available for 10 patients.ResultsNo mutation associated with artemisinin resistance in Southeast Asia was observed. Only one DP-treated patient harboured a non-synonymous mutation at codon 578 (A578S) of pfk13-propeller gene in the day 0 sample, but this allele was replaced by the wild-type (A578) form on day 3 and on the day of recurrent parasitaemia. The mutation at amino acid codon 578 showed no association with any phenotype. Polymorphisms in pfk13 were not responsible for parasite persistence and gametocyte carriage in the children treated with ACT.ConclusionThis study contributes to the ongoing surveillance of suspected artemisinin resistance parasites in Africa by providing baseline prevalence of k13-propeller mutations in western Kenya with samples collected from a longitudinal study. Clinical Trials Registration NCT00868465.
| S-EPMC4722670 | biostudies-literature
Project description:Malaria represents a major public health problem in Africa [1]. In the East African highlands, even in high-altitude areas previously considered too cold to support vector population and parasite transmission [2], frequent malaria epidemics have been reported since the 1980’s [3]. Plasmodium falciparum infections have been detected in areas as high as 1,600-2,400m above sea level in Africa [4], albeit there is a marked gradient of parasite prevalence along the altitude transect [5-7]. Both the historical absence of malaria in the African highlands and now the intensive malaria control efforts put in place after the recent outbreaks have reduced malaria prevalence and incidence [8], rendering the East African highlands particularly prone to epidemic malaria due to the lack of the protective immunity, and causing significant human mortality amongst all age groups [9]. Therefore, malaria transmission monitoring in the East African highlands becomes a particularly important public health issue.Despite the overall lower immunity of the population in these historically malaria-free areas, the many successive outbreaks since the 1980’s may have generated some level of immunity against P. falciparum amongst highland residents. The antibody response to Plasmodium is cumulative and long lasting, developing after repeated exposures to the parasite and persisting for months or years after infection was resolved. The antibody response to Plasmodium varies amongst individuals of different age groups (i.e. toddlers, children and adults) as well as amongst individuals of same age groups from areas of different parasite prevalence [10]. The repertoire of targets of the antibody response also expands after multiple infections, with the number of recognized antigens being correlated to parasite prevalence, age and immunity to clinical malaria [11,12]. Serological studies bring forth indirect evidence of human exposure to the parasite, and can reliably assess its prevalence and transmission intensity in an endemic area [13-15]. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasite’s antigens. The work we present here is an expansion of the study published by Badu et al. [16], in which the antibody response to the 19kDa fragment of merozoite surface protein 1 (MSP-119) was examined in populations from two endemic areas in the western Kenyan highlands. There, the tremendous variations of malaria transmission intensity in a small spatial scale are caused by substantial differences in altitude, topography and other environmental conditions [6,7,17,18]. We now expand our antibody profiling survey to include 854 P. falciparum proteins by using high-throughput proteomic microarray technology. Protein microarrays have been used to explore the humoral response to P. falciparum in other African settings [19-24], but this is the broadest characterization of the antibody responses of the population of western Kenyan highlands to date. In the present study we: i) determined the serological reactivity against P. falciparum (Pf) in subjects residing in a low transmission area, and detected hotspots of transmission; ii) examined the dynamics of antibody response to hundreds of Pf proteins generated by sera from toddlers, older children and adults residing in two endemic areas differing in transmission intensities, during two distinct malaria seasons, and compared the intensity, breadth and antigenic targets of these responses; and iii) identified candidate Pf antigenic markers that could provide more sensitive serological surveillance to detect micro-geographic variations in malaria transmission levels and differentiate hotspots of infection in low endemic areas. (references provided in the 'readme.txt')
2013-06-20 | GSE48089 | GEO
Project description:Malaria represents a major public health problem in Africa [1]. In the East African highlands, even in high-altitude areas previously considered too cold to support vector population and parasite transmission [2], frequent malaria epidemics have been reported since the 1980M-bM-^@M-^Ys [3]. Plasmodium falciparum infections have been detected in areas as high as 1,600-2,400m above sea level in Africa [4], albeit there is a marked gradient of parasite prevalence along the altitude transect [5-7]. Both the historical absence of malaria in the African highlands and now the intensive malaria control efforts put in place after the recent outbreaks have reduced malaria prevalence and incidence [8], rendering the East African highlands particularly prone to epidemic malaria due to the lack of the protective immunity, and causing significant human mortality amongst all age groups [9]. Therefore, malaria transmission monitoring in the East African highlands becomes a particularly important public health issue.Despite the overall lower immunity of the population in these historically malaria-free areas, the many successive outbreaks since the 1980M-bM-^@M-^Ys may have generated some level of immunity against P. falciparum amongst highland residents. The antibody response to Plasmodium is cumulative and long lasting, developing after repeated exposures to the parasite and persisting for months or years after infection was resolved. The antibody response to Plasmodium varies amongst individuals of different age groups (i.e. toddlers, children and adults) as well as amongst individuals of same age groups from areas of different parasite prevalence [10]. The repertoire of targets of the antibody response also expands after multiple infections, with the number of recognized antigens being correlated to parasite prevalence, age and immunity to clinical malaria [11,12]. Serological studies bring forth indirect evidence of human exposure to the parasite, and can reliably assess its prevalence and transmission intensity in an endemic area [13-15]. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasiteM-bM-^@M-^Ys antigens. The work we present here is an expansion of the study published by Badu et al. [16], in which the antibody response to the 19kDa fragment of merozoite surface protein 1 (MSP-119) was examined in populations from two endemic areas in the western Kenyan highlands. There, the tremendous variations of malaria transmission intensity in a small spatial scale are caused by substantial differences in altitude, topography and other environmental conditions [6,7,17,18]. We now expand our antibody profiling survey to include 854 P. falciparum proteins by using high-throughput proteomic microarray technology. Protein microarrays have been used to explore the humoral response to P. falciparum in other African settings [19-24], but this is the broadest characterization of the antibody responses of the population of western Kenyan highlands to date. In the present study we: i) determined the serological reactivity against P. falciparum (Pf) in subjects residing in a low transmission area, and detected hotspots of transmission; ii) examined the dynamics of antibody response to hundreds of Pf proteins generated by sera from toddlers, older children and adults residing in two endemic areas differing in transmission intensities, during two distinct malaria seasons, and compared the intensity, breadth and antigenic targets of these responses; and iii) identified candidate Pf antigenic markers that could provide more sensitive serological surveillance to detect micro-geographic variations in malaria transmission levels and differentiate hotspots of infection in low endemic areas. (references provided in the 'readme.txt') Antibody profiling was performed on sera from residents of western Kenyan highlands against Plasmodium falciparum. One-hundred and ten age-stratified serum samples collected during the dry and the wet seasons, from residents of two locations with differing parasite transmission levels (uphill and valley bottom), and 10 unexposed USA controls were probed on a protein microarray displaying 854 unique proteins of P. falciparum.
2013-06-20 | E-GEOD-48089 | biostudies-arrayexpress
Project description:The declining efficacy of artemisinin derivatives against Plasmodium falciparum in western Cambodia is a major concern. The knowledge gap in the understanding of the mechanisms involved hampers designing monitoring tools. Here, we culture-adapted 20 isolates from Pailin and Ratanakiri (areas of artemisinin resistance and susceptibility in western and eastern Cambodia, respectively) and studied their in vitro response to dihydroartemisinin. No significant difference between the two sets of isolates was observed in the classical isotopic test. However, a 6-h pulse exposure to 700 nM dihydroartemisinin (ring-stage survival assay -RSA]) revealed a clear-cut geographic dichotomy. The survival rate of exposed ring-stage parasites (ring stages) was 17-fold higher in isolates from Pailin (median, 13.5%) than in those from Ratanakiri (median, 0.8%), while exposed mature stages were equally and highly susceptible (0.6% and 0.7%, respectively). Ring stages survived drug exposure by cell cycle arrest and resumed growth upon drug withdrawal. The reduced susceptibility to artemisinin in Pailin appears to be associated with an altered in vitro phenotype of ring stages from Pailin in the RSA.
| S-EPMC3553720 | biostudies-literature
Project description:Artemisinin derivatives are used in combination with other antimalarial drugs for treatment of multidrug-resistant malaria worldwide. Clinical resistance to artemisinin recently emerged in southeast Asia, yet in vitro phenotypes for discerning mechanism(s) of resistance remain elusive. Here, we describe novel phenotypic resistance traits expressed by artemisinin-resistant Plasmodium falciparum. The resistant parasites exhibit altered patterns of development that result in reduced exposure to drug at the most susceptible stage of development in erythrocytes (trophozoites) and increased exposure in the most resistant stage (rings). In addition, a novel in vitro delayed clearance assay (DCA) that assesses drug effects on asexual stages was found to correlate with parasite clearance half-life in vivo as well as with mutations in the Kelch domain gene associated with resistance (Pf3D7_1343700). Importantly, all of the resistance phenotypes were stable in cloned parasites for more than 2 years without drug pressure. The results demonstrate artemisinin-resistant P. falciparum has evolved a novel mechanism of phenotypic resistance to artemisinin drugs linked to abnormal cell cycle regulation. These results offer insights into a novel mechanism of drug resistance in P. falciparum and new tools for monitoring the spread of artemisinin resistance.
| S-EPMC4432152 | biostudies-literature
Project description:The emergence of artemisinin-resistant P. falciparum malaria in South-East Asia highlights the need for continued global surveillance of the efficacy of artemisinin-based combination therapies.On the Kenyan coast we studied the treatment responses in 474 children 6-59 months old with uncomplicated P. falciparum malaria in a randomized controlled trial of dihydroartemisinin-piperaquine vs. artemether-lumefantrine from 2005 to 2008. (ISRCTN88705995).The proportion of patients with residual parasitemia on day 1 rose from 55% in 2005-2006 to 87% in 2007-2008 (odds ratio, 5.4, 95%CI, 2.7-11.1; P<0.001) and from 81% to 95% (OR, 4.1, 95%CI, 1.7-9.9; P?=?0.002) in the DHA-PPQ and AM-LM groups, respectively. In parallel, Kaplan-Meier estimated risks of apparent recrudescent infection by day 84 increased from 7% to 14% (P?=?0.1) and from 6% to 15% (P?=?0.05) with DHA-PPQ and AM-LM, respectively. Coinciding with decreasing transmission in the study area, clinical tolerance to parasitemia (defined as absence of fever) declined between 2005-2006 and 2007-2008 (OR body temperature >37.5°C, 2.8, 1.9-4.1; P<0.001). Neither in vitro sensitivity of parasites to DHA nor levels of antibodies against parasite extract accounted for parasite clearance rates or changes thereof.The significant, albeit small, decline through time of parasitological response rates to treatment with ACTs may be due to the emergence of parasites with reduced drug sensitivity, to the coincident reduction in population-level clinical immunity, or both. Maintaining the efficacy of artemisinin-based therapy in Africa would benefit from a better understanding of the mechanisms underlying reduced parasite clearance rates.Controlled-Trials.com ISRCTN88705995.
| S-EPMC3213089 | biostudies-literature
Project description:For more than five decades, Southeast Asia (SEA) has been fertile ground for the emergence of drug-resistant Plasmodium falciparum malaria. After generating parasites resistant to chloroquine, sulfadoxine, pyrimethamine, quinine, and mefloquine, this region has now spawned parasites resistant to artemisinins, the world's most potent antimalarial drugs. In areas where artemisinin resistance is prevalent, artemisinin combination therapies (ACTs)-the first-line treatments for malaria-are failing fast. This worrisome development threatens to make malaria practically untreatable in SEA, and threatens to compromise global endeavors to eliminate this disease. A recent series of clinical, in vitro, genomics, and transcriptomics studies in SEA have defined in vivo and in vitro phenotypes of artemisinin resistance, identified its causal genetic determinant, explored its molecular mechanism, and assessed its clinical impact. Specifically, these studies have established that artemisinin resistance manifests as slow parasite clearance in patients and increased survival of early-ring-stage parasites in vitro; is caused by single nucleotide polymorphisms in the parasite's K13 gene, is associated with an upregulated "unfolded protein response" pathway that may antagonize the pro-oxidant activity of artemisinins, and selects for partner drug resistance that rapidly leads to ACT failures. In SEA, clinical studies are urgently needed to monitor ACT efficacy where K13 mutations are prevalent, test whether new combinations of currently available drugs cure ACT failures, and advance new antimalarial compounds through preclinical pipelines and into clinical trials. Intensifying these efforts should help to forestall the spread of artemisinin and partner drug resistance from SEA to sub-Saharan Africa, where the world's malaria transmission, morbidity, and mortality rates are highest.
| S-EPMC4992992 | biostudies-literature
Project description:Malaria is the deadliest parasitic disease affecting over 200 million people worldwide. The increasing number of treatment failures due to multi-drug-resistant parasites in South-East Asia hinders the efforts for elimination. It is thus urgent to develop new antimalarials to contain these resistant parasites. Based on a previous report showing the presence of DNA methylation in Plasmodium, we generated new types of DNA methylation inhibitors against malaria parasites. The quinoline-quinazoline-based inhibitors kill parasites, including artemisinin-resistant field isolates adapted to culture, in the low nanomolar range. The compounds target all stages of the asexual cycle, including early rings, during a 6 h treatment period; they reduce DNA methylation in the parasite and show in vivo activity at 10 mg/kg. These potent inhibitors are a new starting point to develop fast-acting antimalarials that could be used in combination with artemisinins.
| S-EPMC6978834 | biostudies-literature
Project description:BackgroundArtemisinin-resistant Plasmodium falciparum has been reported in Pailin, western Cambodia, detected as a slow parasite clearance rate in vivo. Emergence of this phenotype in western Thailand and possibly elsewhere threatens to compromise the effectiveness of all artemisinin-based combination therapies. Parasite genetics is associated with parasite clearance rate but does not account for all variation. We investigated contributions of both parasite genetics and host factors to the artemisinin-resistance phenotype in Pursat, western Cambodia.MethodsBetween June 19 and Nov 28, 2009, and June 26 and Dec 6, 2010, we enrolled patients aged 10 years or older with uncomplicated falciparum malaria, a density of asexual parasites of at least 10,000 per μL of whole blood, no symptoms or signs of severe malaria, no other cause of febrile illness, and no chronic illness. We gave participants 4 mg/kg artesunate at 0, 24, and 48 h, 15 mg/kg mefloquine at 72 h, and 10 mg/kg mefloquine at 96 h. We assessed parasite density on thick blood films every 6 h until undetectable. The parasite clearance half-life was calculated from the parasite clearance curve. We genotyped parasites with 18 microsatellite markers and patients for haemoglobin E, α-thalassaemia, and a mutation of G6PD, which encodes glucose-6-phosphate dehydrogenase. To account for the possible effects of acquired immunity on half-life, we used three surrogates for increased likelihood of exposure to P falciparum: age, sex, and place of residence. This study is registered with ClinicalTrials.gov, number NCT00341003.FindingsWe assessed 3504 individuals from all six districts of Pursat province seeking treatment for malaria symptoms. We enrolled 168 patients with falciparum malaria who met inclusion criteria. The geometric mean half-life was 5·85 h (95% CI 5·54-6·18) in Pursat, similar to that reported in Pailin (p=0·109). We identified two genetically different parasite clone groups: parasite group 1 (PG1) and parasite group 2 (PG2). Non-significant increases in parasite clearance half-life were seen in patients with haemoglobin E (0·55 h; p=0·078), those of male sex (0·96 h; p=0·064), and in 2010 (0·68 h; p=0·068); PG1 was associated with a significant increase (0·79 h; p=0·033). The mean parasite heritability of half-life was 0·40 (SD 0·17).InterpretationHeritable artemisinin resistance is established in a second Cambodian province. To accurately identify parasites that are intrinsically susceptible or resistant to artemisinins, future studies should explore the effect of erythrocyte polymorphisms and specific immune responses on half-life variation.FundingDivision of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.
| S-EPMC3786328 | biostudies-literature
Project description:BackgroundArtemisinin-based combination therapies are the recommended first-line treatments of falciparum malaria in all countries with endemic disease. There are recent concerns that the efficacy of such therapies has declined on the Thai-Cambodian border, historically a site of emerging antimalarial-drug resistance.MethodsIn two open-label, randomized trials, we compared the efficacies of two treatments for uncomplicated falciparum malaria in Pailin, western Cambodia, and Wang Pha, northwestern Thailand: oral artesunate given at a dose of 2 mg per kilogram of body weight per day, for 7 days, and artesunate given at a dose of 4 mg per kilogram per day, for 3 days, followed by mefloquine at two doses totaling 25 mg per kilogram. We assessed in vitro and in vivo Plasmodium falciparum susceptibility, artesunate pharmacokinetics, and molecular markers of resistance.ResultsWe studied 40 patients in each of the two locations. The overall median parasite clearance times were 84 hours (interquartile range, 60 to 96) in Pailin and 48 hours (interquartile range, 36 to 66) in Wang Pha (P<0.001). Recrudescence confirmed by means of polymerase-chain-reaction assay occurred in 6 of 20 patients (30%) receiving artesunate monotherapy and 1 of 20 (5%) receiving artesunate-mefloquine therapy in Pailin, as compared with 2 of 20 (10%) and 1 of 20 (5%), respectively, in Wang Pha (P=0.31). These markedly different parasitologic responses were not explained by differences in age, artesunate or dihydroartemisinin pharmacokinetics, results of isotopic in vitro sensitivity tests, or putative molecular correlates of P. falciparum drug resistance (mutations or amplifications of the gene encoding a multidrug resistance protein [PfMDR1] or mutations in the gene encoding sarco-endoplasmic reticulum calcium ATPase6 [PfSERCA]). Adverse events were mild and did not differ significantly between the two treatment groups.ConclusionsP. falciparum has reduced in vivo susceptibility to artesunate in western Cambodia as compared with northwestern Thailand. Resistance is characterized by slow parasite clearance in vivo without corresponding reductions on conventional in vitro susceptibility testing. Containment measures are urgently needed. (ClinicalTrials.gov number, NCT00493363, and Current Controlled Trials number, ISRCTN64835265.)
| S-EPMC3495232 | biostudies-literature