scholarly journals Limited Polymorphism of the Kelch Propeller Domain in Plasmodium malariae and P. ovale Isolates from Thailand

2016 ◽  
Vol 60 (7) ◽  
pp. 4055-4062 ◽  
Author(s):  
Supatchara Nakeesathit ◽  
Naowarat Saralamba ◽  
Sasithon Pukrittayakamee ◽  
Arjen Dondorp ◽  
Francois Nosten ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Southeast Asia ◽  
Severe Malaria ◽  
Malaria Control ◽  
Artemisinin Resistance ◽  
Plasmodium Malariae ◽  
The Other ◽  
Content Type ◽  
Functional Consequences ◽  
First Time

ABSTRACTArtemisinin resistance inPlasmodium falciparum, the agent of severe malaria, is currently a major obstacle to malaria control in Southeast Asia. A gene named “kelch13” has been associated with artemisinin resistance inP. falciparum. The orthologue of thekelchgene inP. vivaxwas identified and a small number of mutations were found in previous studies. Thekelchorthologues in the other two human malaria parasites,P. malariaeandP. ovale, have not yet been studied. Therefore, in this study, the orthologouskelchgenes ofP. malariae,P. ovale wallikeri, andP. ovale curtisiwere isolated and analyzed for the first time. The homologies of thekelchgenes ofP. malariaeandP. ovalewere 84.8% and 82.7%, respectively, compared to the gene inP. falciparum.kelchpolymorphisms were studied in 13P. malariaeand 5P. ovaleisolates from Thailand. There were 2 nonsynonymous mutations found in these samples. One mutation was P533L, which was found in 1 of 13P. malariaeisolates, and the other was K137R, found in 1 isolate ofP. ovale wallikeri(n= 4). This result needs to be considered in the context of widespread artemisinin used within the region; their functional consequences for artemisinin sensitivity inP. malariaeandP. ovalewill need to be elucidated.

scholarly journals The Diversity of the Plasmodium falciparum K13 Propeller Domain Did Not Increase after Implementation of Artemisinin-Based Combination Therapy in Uganda

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Melissa D. Conrad ◽  
Sam L. Nsobya ◽  
Philip J. Rosenthal
Keyword(s):  
Plasmodium Falciparum ◽  
Southeast Asia ◽  
Artemisinin Resistance ◽  
Standard Of Care ◽  
Parasite Clearance ◽  
Sub Saharan Africa ◽  
Clinical Isolates ◽  
Nucleotide Polymorphisms ◽  
Content Type ◽  
Sub Saharan

ABSTRACT Artemisinin-based combination therapies (ACTs) are the standard of care to treat uncomplicated falciparum malaria. However, resistance to artemisinins, defined as delayed parasite clearance after therapy, has emerged in Southeast Asia, and the spread of resistance to sub-Saharan Africa could have devastating consequences. Artemisinin resistance has been associated in Southeast Asia with multiple nonsynonymous single nucleotide polymorphisms (NS-SNPs) in the propeller domain of the gene encoding the Plasmodium falciparum K13 protein (K13PD). Some K13PD NS-SNPs have been seen in Africa, but the relevance of these mutations is unclear. To assess whether ACT use has selected for specific K13PD mutations, we compared the K13PD genetic diversity in clinical isolates collected before and after the implementation of ACT use from seven sites across Uganda. We detected K13PD NS-SNPs in 16 of 683 (2.3%) clinical isolates collected between 1999 and 2004 and in 26 of 716 (3.6%) isolates collected between 2012 and 2016 (P = 0.16), representing a total of 29 different polymorphisms at 27 codons. Individual NS-SNPs were usually detected only once, and none were found in more than 0.7% of the isolates. Three SNPs (C469F, P574L, and A675V) associated with delayed clearance in Southeast Asia were seen in samples collected between 2012 and 2016, each in a single isolate. No differences in diversity following implementation of ACT use were found at any of the seven sites, nor was there evidence of selective pressures acting on the locus. Our results suggest that selection by ACTs is not impacting on K13PD diversity in Uganda.

scholarly journals Predictors of treatment failures of plasmodium falciparum malaria in Vietnam: a 4-year single‐centre retrospective study

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Minh Cuong Duong ◽  
Oanh Kieu Nguyet Pham ◽  
Phong Thanh Nguyen ◽  
Van Vinh Chau Nguyen ◽  
Phu Hoan Nguyen
Keyword(s):  
Plasmodium Falciparum ◽  
Treatment Failure ◽  
Severe Malaria ◽  
Falciparum Malaria ◽  
Control Strategies ◽  
Artemisinin Resistance ◽  
Plasmodium Falciparum Malaria ◽  
Molecular Technique ◽  
Drug Resistant ◽  
Public Health Burden

Abstract Background Drug-resistant falciparum malaria is an increasing public health burden. This study examined the magnitude of Plasmodium falciparum infection and the patterns and predictors of treatment failure in Vietnam. Methods Medical records of all 443 patients with malaria infection admitted to the Hospital for Tropical Diseases between January 2015 and December 2018 were used to extract information on demographics, risk factors, symptoms, laboratory tests, treatment, and outcome. Results More than half (59.8%, 265/443, CI 55.1–64.4%) of patients acquired Plasmodium falciparum infection of whom 21.9% (58/265, CI 17.1–27.4%) had severe malaria, while 7.2% (19/265, CI 4.6–10.9%) and 19.2% (51/265, CI 14.7–24.5%) developed early treatment failure (ETF) and late treatment failure (LTF) respectively. Among 58 patients with severe malaria, 14 (24.1%) acquired infection in regions where artemisinin resistance has been documented including Binh Phuoc (11 patients), Dak Nong (2 patients) and Gia Lai (1 patient). Under treatment with intravenous artesunate, the median (IQR) parasite half-life of 11 patients coming from Binh Phuoc was 3 h (2.3 to 8.3 h), two patients coming from Dak Nong was 2.8 and 5.7 h, and a patient coming from Gia Lai was 6.5 h. Most patients (98.5%, 261/265) recovered completely. Four patients with severe malaria died. Severe malaria was statistically associated with receiving treatment at previous hospitals (P < 0.001), hepatomegaly (P < 0.001) and number of inpatient days (P < 0.001). Having severe malaria was a predictor of ETF (AOR 6.96, CI 2.55–19.02, P < 0.001). No predictor of LTF was identified. Conclusions Plasmodium falciparum remains the prevalent malaria parasite. Despite low mortality rate, severe malaria is not rare and is a significant predictor of ETF. To reduce the risk for ETF, studies are needed to examine the effectiveness of combination therapy including parenteral artesunate and a parenteral partner drug for severe malaria. The study alerts the possibility of drug-resistant malaria in Africa and other areas in Vietnam, which are known as non-endemic areas of anti-malarial drug resistance. A more comprehensive study using molecular technique in these regions is required to completely understand the magnitude of drug-resistant malaria and to design appropriate control strategies.

scholarly journals Emergence and Spread of kelch13 Mutations Associated with Artemisinin Resistance in Plasmodium falciparum Parasites in 12 Thai Provinces from 2007 to 2016

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Theerayot Kobasa ◽  
Eldin Talundzic ◽  
Rungniran Sug-aram ◽  
Patcharida Boondat ◽  
Ira F. Goldman ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Gene Mutations ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Resistance Mutations ◽  
Content Type ◽  
Artemisinin Derivatives ◽  
Reduced Ring ◽  
Control And Prevention ◽  
Greater Mekong Subregion

ABSTRACT Artemisinin-based combination therapy (ACT) is the most effective and widely used treatment for uncomplicated Plasmodium falciparum malaria and is a cornerstone for malaria control and prevention globally. Resistance to artemisinin derivatives has been confirmed in the Greater Mekong Subregion (GMS) and manifests as slow parasite clearance in patients and reduced ring stage susceptibility to artemisinins in survival assays. The P. falciparum kelch13 gene mutations associated with artemisinin-resistant parasites are now widespread in the GMS. We genotyped 277 samples collected during an observational study from 2012 to 2016 from eight provinces in Thailand to identify P. falciparum kelch13 mutations. The results were combined with previously reported genotyping results from Thailand to construct a map illustrating the evolution of P. falciparum kelch13 mutations from 2007 to 2016 in that country. Different mutant alleles were found in strains with different geographical origins. The artemisinin resistance-conferring Y493H and R539T mutations were detected mainly in eastern Thailand (bordering Cambodia), while P574L was found only in western Thailand and R561H only in northwestern Thailand. The C580Y mutation was found across the entire country and was nearing fixation along the Thai-Cambodia border. Overall, the prevalence of artemisinin resistance mutations increased over the last 10 years across Thailand, especially along the Thai-Cambodia border. Molecular surveillance and therapeutic efficacy monitoring should be intensified in the region to further assess the extent and spread of artemisinin resistance.

scholarly journals Expansion of a Specific Plasmodium falciparum PfMDR1 Haplotype in Southeast Asia with Increased Substrate Transport

mBio ◽  
2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Carla Calçada ◽  
Miguel Silva ◽  
Vitória Baptista ◽  
Vandana Thathy ◽  
Rita Silva-Pedrosa ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Multidrug Resistance ◽  
Southeast Asia ◽  
Gene Copy ◽  
Multidrug Resistance Protein ◽  
Combination Therapies ◽  
Transport Capacity ◽  
Multidrug Resistance Protein 1 ◽  
Content Type ◽  
Resistance Protein

ABSTRACT Artemisinin-based combination therapies (ACTs) have been vital in reducing malaria mortality rates since the 2000s. Their efficacy, however, is threatened by the emergence and spread of artemisinin resistance in Southeast Asia. The Plasmodium falciparum multidrug resistance protein 1 (PfMDR1) transporter plays a central role in parasite resistance to ACT partner drugs through gene copy number variations (CNV) and/or single nucleotide polymorphisms (SNPs). Using genomic epidemiology, we show that multiple pfmdr1 copies encoding the N86 and 184F haplotype are prevalent across Southeast Asia. Applying genome editing tools on the Southeast Asian Dd2 strain and using a surrogate assay to measure transporter activity in infected red blood cells, we demonstrate that parasites harboring multicopy N86/184F PfMDR1 have a higher Fluo-4 transport capacity compared with those expressing the wild-type N86/Y184 haplotype. Multicopy N86/184F PfMDR1 is also associated with decreased parasite susceptibility to lumefantrine. These findings provide evidence of the geographic selection and expansion of specific multicopy PfMDR1 haplotypes associated with multidrug resistance in Southeast Asia. IMPORTANCE Global efforts to eliminate malaria depend on the continued success of artemisinin-based combination therapies (ACTs) that target Plasmodium asexual blood-stage parasites. Resistance to ACTs, however, has emerged, creating the need to define the underlying mechanisms. Mutations in the P. falciparum multidrug resistance protein 1 (PfMDR1) transporter constitute an important determinant of resistance. Applying gene editing tools combined with an analysis of a public database containing thousands of parasite genomes, we show geographic selection and expansion of a pfmdr1 gene amplification encoding the N86/184F haplotype in Southeast Asia. Parasites expressing this PfMDR1 variant possess a higher transport capacity that modulates their responses to antimalarials. These data could help tailor and optimize antimalarial drug usage in different regions where malaria is endemic by taking into account the regional prevalence of pfmdr1 polymorphisms.

scholarly journals Artemisone and Artemiside Are Potent Panreactive Antimalarial Agents That Also Synergize Redox Imbalance in Plasmodium falciparum Transmissible Gametocyte Stages

2018 ◽  
Vol 62 (8) ◽  
Author(s):  
Dina Coertzen ◽  
Janette Reader ◽  
Mariëtte van der Watt ◽  
Sindisiwe H. Nondaba ◽  
Liezl Gibhard ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Control ◽  
Malaria Parasite ◽  
Redox Homeostasis ◽  
New Drugs ◽  
Content Type ◽  
Artemisinin Derivatives ◽  
Antimalarial Agents ◽  
Redox Partner ◽  
Emergence Of Resistance

ABSTRACT The emergence of resistance toward artemisinin combination therapies (ACTs) by the malaria parasite Plasmodium falciparum has the potential to severely compromise malaria control. Therefore, the development of new artemisinins in combination with new drugs that impart activities toward both intraerythrocytic proliferative asexual and transmissible gametocyte stages, in particular, those of resistant parasites, is urgently required. We define artemisinins as oxidant drugs through their ability to oxidize reduced flavin cofactors of flavin disulfide reductases critical for maintaining redox homeostasis in the malaria parasite. Here we compare the activities of 10-amino artemisinin derivatives toward the asexual and gametocyte stages of P. falciparum parasites. Of these, artemisone and artemiside inhibited asexual and gametocyte stages, particularly stage V gametocytes, in the low-nanomolar range. Further, treatment of both early and late gametocyte stages with artemisone or artemiside combined with the pro-oxidant redox partner methylene blue displayed notable synergism. These data suggest that modulation of redox homeostasis is likely an important druggable process, particularly in gametocytes, and this finding thereby enhances the prospect of using combinations of oxidant and redox drugs for malaria control.

scholarly journals A Novel Tool for the Generation of Conditional Knockouts To Study Gene Function across the Plasmodium falciparum Life Cycle

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Marta Tibúrcio ◽  
Annie S. P. Yang ◽  
Kazuhide Yahata ◽  
Pablo Suárez-Cortés ◽  
Hugo Belda ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Life Cycle ◽  
Genetic Modification ◽  
Gene Deletion ◽  
Genetically Modify ◽  
Complex Life Cycle ◽  
Mosquito Vector ◽  
Parasite Line ◽  
Content Type ◽  
First Time

ABSTRACT Plasmodium falciparum has a complex life cycle that involves interaction with multiple tissues inside the human and mosquito hosts. Identification of essential genes at all different stages of the P. falciparum life cycle is urgently required for clinical development of tools for malaria control and eradication. However, the study of P. falciparum is limited by the inability to genetically modify the parasite throughout its life cycle with the currently available genetic tools. Here, we describe the detailed characterization of a new marker-free P. falciparum parasite line that expresses rapamycin-inducible Cre recombinase across the full life cycle. Using this parasite line, we were able to conditionally delete the essential invasion ligand AMA1 in three different developmental stages for the first time. We further confirm efficient gene deletion by targeting the nonessential kinase FIKK7.1. IMPORTANCE One of the major limitations in studying P. falciparum is that so far only asexual stages are amenable to rapid conditional genetic modification. The most promising drug targets and vaccine candidates, however, have been refractory to genetic modification because they are essential during the blood stage or for transmission in the mosquito vector. This leaves a major gap in our understanding of parasite proteins in most life cycle stages and hinders genetic validation of drug and vaccine targets. Here, we describe a method that supports conditional gene deletion across the P. falciparum life cycle for the first time. We demonstrate its potential by deleting essential and nonessential genes at different parasite stages, which opens up completely new avenues for the study of malaria and drug development. It may also allow the realization of novel vaccination strategies using attenuated parasites.

scholarly journals Delayed Parasite Clearance after Treatment with Dihydroartemisinin-Piperaquine in Plasmodium falciparum Malaria Patients in Central Vietnam

2014 ◽  
Vol 58 (12) ◽  
pp. 7049-7055 ◽  
Author(s):  
Kamala Thriemer ◽  
Nguyen Van Hong ◽  
Anna Rosanas-Urgell ◽  
Bui Quang Phuc ◽  
Do Manh Ha ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Clearance Rate ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Clearance Time ◽  
Sensitivity Testing ◽  
Content Type ◽  
Parasite Clearance Time ◽  
Central Vietnam

ABSTRACTReduced susceptibility ofPlasmodium falciparumtoward artemisinin derivatives has been reported from the Thai-Cambodian and Thai-Myanmar borders. Following increasing reports from central Vietnam of delayed parasite clearance after treatment with dihydroartemisinin-piperaquine (DHA-PPQ), the current first-line treatment, we carried out a study on the efficacy of this treatment. Between September 2012 and February 2013, we conducted a 42-dayin vivoandin vitroefficacy study in Quang Nam Province. Treatment was directly observed, and blood samples were collected twice daily until parasite clearance. In addition, genotyping, quantitative PCR (qPCR), andin vitrosensitivity testing of isolates was performed. The primary endpoints were parasite clearance rate and time. The secondary endpoints included PCR-corrected and uncorrected cure rates, qPCR clearance profiles,in vitrosensitivity results (for chloroquine, dihydroartemisinin, and piperaquine), and genotyping for mutations in the Kelch 13 propeller domain. Out of 672 screened patients, 95 were recruited and 89 available for primary endpoint analyses. The median parasite clearance time (PCT) was 61.7 h (interquartile range [IQR], 47.6 to 83.2 h), and the median parasite clearance rate had a slope half-life of 6.2 h (IQR, 4.4 to 7.5 h). The PCR-corrected efficacy rates were estimated at 100% at day 28 and 97.7% (95% confidence interval, 91.2% to 99.4%) at day 42. At day 3, theP. falciparumprevalence by qPCR was 2.5 times higher than that by microscopy. The 50% inhibitory concentrations (IC50s) of isolates with delayed clearance times (≥72 h) were significantly higher than those with normal clearance times for all three drugs. Delayed parasite clearance (PCT, ≥72 h) was significantly higher among day 0 samples carrying the 543 mutant allele (47.8%) than those carrying the wild-type allele (1.8%;P= 0.048). In central Vietnam, the efficacy of DHA-PPQ is still satisfactory, but the parasite clearance time and rate are indicative of emerging artemisinin resistance. (This study has been registered at ClinicalTrials.gov under registration no. NCT01775592.)

scholarly journals Antibodies to Peptides in Semiconserved Domains of RIFINs and STEVORs Correlate with Malaria Exposure

mSphere ◽  
2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Albert E. Zhou ◽  
Andrea A. Berry ◽  
Jason A. Bailey ◽  
Andrew Pike ◽  
Antoine Dara ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Severe Malaria ◽  
Surface Antigen ◽  
Immune Evasion ◽  
Clinical Malaria ◽  
Malaria Episode ◽  
Natural Immunity ◽  
Content Type ◽  
Variant Surface Antigen ◽  
Malaria Exposure

ABSTRACT The repetitive interspersed family (RIFIN) and the subtelomeric variable open reading frame (STEVOR) family represent two of three major Plasmodium falciparum variant surface antigen families involved in malaria pathogenesis and immune evasion and are potential targets in the development of natural immunity. Protein and peptide microarrays populated with RIFINs and STEVORs associated with severe malaria vulnerability in Malian children were probed with adult and pediatric sera to identify epitopes that reflect malaria exposure. Adult sera recognized and reacted with greater intensity to all STEVOR proteins than pediatric sera did. Serorecognition of and seroreactivity to peptides within the semiconserved domain of STEVORs increased with age and seasonal malaria exposure, while serorecognition and seroreactivity increased for the semiconserved and second hypervariable domains of RIFINs only with age. Serologic responses to RIFIN and STEVOR peptides within the semiconserved domains may play a role in natural immunity to severe malaria. IMPORTANCE Malaria, an infectious disease caused by the parasite Plasmodium falciparum, causes nearly 435,000 deaths annually worldwide. RIFINs and STEVORs are two variant surface antigen families that are involved in malaria pathogenesis and immune evasion. Recent work has shown that a lack of humoral immunity to these proteins is associated with severe malaria vulnerability in Malian children. This is the first study to have compared serologic responses of children and adults to RIFINs and STEVORs in settings of malaria endemicity and to examine such serologic responses before and after a clinical malaria episode. Using microarrays, we determined that the semiconserved domains in these two parasite variant surface antigen families harbor peptides whose seroreactivity reflects malaria exposure. A similar approach has the potential to illuminate the role of variant surface antigens in the development of natural immunity to clinical malaria. Potential vaccines for severe malaria should include consideration of peptides within the semiconserved domains of RIFINs and STEVORs.

scholarly journals Distinctive Origin and Spread Route of Pyrimethamine-Resistant Plasmodium falciparum in Southern China

2013 ◽  
Vol 58 (1) ◽  
pp. 237-246 ◽  
Author(s):  
Yilong Zhang ◽  
He Yan ◽  
Guiying Wei ◽  
Shitong Han ◽  
Yufu Huang ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Southeast Asia ◽  
Southern China ◽  
Hainan Island ◽  
Epidemiological Studies ◽  
Single Nucleotide ◽  
Evolutionary Pathway ◽  
Content Type ◽  
Genetic Linkages ◽  
High Level

ABSTRACTSoutheast Asia (the Thailand-Cambodia border) has been considered the primal epicenter for most antimalarial drug resistance; however, numerous molecular epidemiological studies have successively reported multiple independent origins of sulfadoxine-pyrimethamine (SP) resistance-associatedPlasmodium falciparumdhfr(pfdhfr) andpfdhpsalleles in other areas. To better understand the origin and evolutionary pathway of the SP resistance in Southeast Asia, a total of 374P. falciparumfield isolates from the Yunnan-Burma border and Hainan Island in southern China have been collected for comprehensive investigations on the mutation patterns of thepfdhfr/pfdhpsgenes as well as their microsatellite haplotypes. By comparative analysis of single-nucleotide polymorphism (SNP) genotyping and flanking microsatellite haplotypes, we reveal a unique origin of pyrimethamine-resistant mutations inPfdhfrgene in Hainan Island and an oriented spread route of the pyrimethamine resistance from the Thailand-Cambodia border into the Hainan area, which reflects the geographical traits and SP administration histories in the two geographically independent areas. Moreover, genetic linkages between the high-level SP resistance-conferringpfdhfr/pfdhpsalleles have been established in the isolates from the Yunnan-Burma border, raising the concern of a genetic basis in adopting combination chemotherapies against falciparum malaria.

scholarly journals Surveillance of Artemisinin Resistance in Plasmodium falciparum in India Using the kelch13 Molecular Marker

2015 ◽  
Vol 59 (5) ◽  
pp. 2548-2553 ◽  
Author(s):  
Neelima Mishra ◽  
Surendra Kumar Prajapati ◽  
Kamlesh Kaitholia ◽  
Ram Suresh Bharti ◽  
Bina Srivastava ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Molecular Marker ◽  
Association Studies ◽  
Point Mutations ◽  
Artemisinin Resistance ◽  
Content Type ◽  
Combination Treatments ◽  
The Status ◽  
Genome Association ◽  
Efficacy Studies

ABSTRACTMalaria treatment in Southeast Asia is threatened with the emergence of artemisinin-resistantPlasmodium falciparum. Genome association studies have strongly linked a locus onP. falciparumchromosome 13 to artemisinin resistance, and recently, mutations in the kelch13 propeller region (Pfk-13) were strongly linked to resistance. To date, this information has not been shown in Indian samples.Pfk-13mutations were assessed in samples from efficacy studies of artemisinin combination treatments in India. Samples were PCR amplified and sequenced from codon 427 to 727. Out of 384 samples, nonsynonymous mutations in the propeller region were found in four patients from the northeastern states, but their presence did not correlate with ACT treatment failures. This is the first report ofPfk-13point mutations from India. Further phenotyping and genotyping studies are required to assess the status of artemisinin resistance in this region.

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