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Antimicrobial Agents and Chemotherapy Jul 2023The increasing burden and spread of resistant malaria parasites remains an immense burden to public health. These factors have driven the demand to search for a new...
The increasing burden and spread of resistant malaria parasites remains an immense burden to public health. These factors have driven the demand to search for a new therapeutic agent. From our screening, phebestin stood out with nanomolar efficacy against Plasmodium falciparum 3D7. Phebestin was initially identified as an aminopeptidase N inhibitor. Phebestin inhibited the multiplication of the P. falciparum 3D7 (chloroquine-sensitive) and K1 (chloroquine-resistant) strains at IC values of 157.90 ± 6.26 nM and 268.17 ± 67.59 nM, respectively. Furthermore, phebestin exhibited no cytotoxic against human foreskin fibroblast cells at 2.5 mM. In the stage-specific assay, phebestin inhibited all parasite stages at 100 and 10-fold its IC concentration. Using 72-h exposure of phebestin at concentrations of 1 μM on P. falciparum 3D7 distorted the parasite morphology, showed dying signs, shrank, and prevented reinvasion of RBCs, even after the compound was washed from the culture. An study found that phebestin binds to P. falciparum M1 alanyl aminopeptidase (PfM1AAP) and M17 leucyl aminopeptidase (PfM17LAP), as observed for bestatin. evaluation using P. yoelii 17XNL-infected mice with administrations of 20 mg/kg phebestin, once daily for 7 days, resulted in significantly lower parasitemia peaks in the phebestin-treated group (19.53%) than in the untreated group (29.55%). At the same dose and treatment, P. berghei ANKA-infected mice showed reduced parasitemia levels and improved survival compared to untreated mice. These results indicate that phebestin is a promising candidate for development as a potential therapeutic agent against malaria.
Topics: Humans; Animals; Mice; Antimalarials; Aminopeptidases; Parasitemia; Chloroquine; Malaria; Malaria, Falciparum; Plasmodium falciparum; Plasmodium berghei
PubMed: 37314349
DOI: 10.1128/aac.01606-22 -
PLoS Pathogens Jun 2024Plasmodium parasites, the causal agents of malaria, are eukaryotic organisms that obligately undergo sexual recombination within mosquitoes. In low transmission...
Plasmodium parasites, the causal agents of malaria, are eukaryotic organisms that obligately undergo sexual recombination within mosquitoes. In low transmission settings, parasites recombine with themselves, and the clonal lineage is propagated rather than broken up by outcrossing. We investigated whether stochastic/neutral factors drive the persistence and abundance of Plasmodium falciparum clonal lineages in Guyana, a country with relatively low malaria transmission, but the only setting in the Americas in which an important artemisinin resistance mutation (pfk13 C580Y) has been observed. We performed whole genome sequencing on 1,727 Plasmodium falciparum samples collected from infected patients across a five-year period (2016-2021). We characterized the relatedness between each pair of monoclonal infections (n = 1,409) through estimation of identity-by-descent (IBD) and also typed each sample for known or candidate drug resistance mutations. A total of 160 multi-isolate clones (mean IBD ≥ 0.90) were circulating in Guyana during the study period, comprising 13 highly related clusters (mean IBD ≥ 0.40). In the five-year study period, we observed a decrease in frequency of a mutation associated with artemisinin partner drug (piperaquine) resistance (pfcrt C350R) and limited co-occurence of pfcrt C350R with duplications of plasmepsin 2/3, an epistatic interaction associated with piperaquine resistance. We additionally observed 61 nonsynonymous substitutions that increased markedly in frequency over the study period as well as a novel pfk13 mutation (G718S). However, P. falciparum clonal dynamics in Guyana appear to be largely driven by stochastic factors, in contrast to other geographic regions, given that clones carrying drug resistance polymorphisms do not demonstrate enhanced persistence or higher abundance than clones carrying polymorphisms of comparable frequency that are unrelated to resistance. The use of multiple artemisinin combination therapies in Guyana may have contributed to the disappearance of the pfk13 C580Y mutation.
Topics: Plasmodium falciparum; Guyana; Malaria, Falciparum; Humans; Antimalarials; Drug Resistance; Artemisinins; Mutation; Protozoan Proteins
PubMed: 38870266
DOI: 10.1371/journal.ppat.1012013 -
Nature Medicine Nov 2023Artemisinin combination therapies (ACTs) are highly effective at treating uncomplicated Plasmodium falciparum malaria, but the emergence of the new pfkelch13 R561H...
Artemisinin combination therapies (ACTs) are highly effective at treating uncomplicated Plasmodium falciparum malaria, but the emergence of the new pfkelch13 R561H mutation in Rwanda, associated with delayed parasite clearance, suggests that interventions are needed to slow its spread. Using a Rwanda-specific spatial calibration of an individual-based malaria model, we evaluate 26 strategies aimed at minimizing treatment failures and delaying the spread of R561H after 3, 5 and 10 years. Lengthening ACT courses and deploying multiple first-line therapies (MFTs) reduced treatment failures after 5 years when compared to the current approach of a 3-d course of artemether-lumefantrine. The best among these options (an MFT policy) resulted in median treatment failure counts that were 49% lower and a median R561H allele frequency that was 0.15 lower than under baseline. New approaches to resistance management, such as triple ACTs or sequential courses of two different ACTs, were projected to have a larger impact than longer ACT courses or MFT; these were associated with median treatment failure counts in 5 years that were 81-92% lower than the current approach. A policy response to currently circulating artemisinin-resistant genotypes in Africa is urgently needed to prevent a population-wide rise in treatment failures.
Topics: Humans; Antimalarials; Artemisinins; Plasmodium falciparum; Rwanda; Artemether; Drug Resistance; Artemether, Lumefantrine Drug Combination; Malaria, Falciparum; Mutation
PubMed: 37735560
DOI: 10.1038/s41591-023-02551-w -
MBio Oct 2023Malaria is a devastating disease caused by parasites. The evolution of parasite drug resistance continues to hamper progress toward malaria elimination, and despite...
Malaria is a devastating disease caused by parasites. The evolution of parasite drug resistance continues to hamper progress toward malaria elimination, and despite extensive efforts to control malaria, it remains a leading cause of death in Mozambique and other countries in the region. The development of successful vaccines and identification of molecular markers to track drug efficacy are essential for managing the disease burden. We present an analysis of the parasite genome in Mozambique, a country with one of the highest malaria burdens globally and limited available genomic data, revealing current selection pressure. We contribute additional evidence to limited prior studies supporting the effectiveness of SWGA in producing reliable genomic data from complex clinical samples. Our results provide the identity of genomic loci that may be associated with current antimalarial drug use, including artemisinin and lumefantrine, and reveal selection pressure predicted to compromise the efficacy of current vaccine candidates.
Topics: Animals; Humans; Plasmodium falciparum; Mozambique; Antimalarials; Malaria; Parasites; Genomics; Drug Resistance; Malaria, Falciparum
PubMed: 37750720
DOI: 10.1128/mbio.01768-23 -
Diagnostics (Basel, Switzerland) Oct 2023Due to the difficulty of obtaining blood samples, which is the invasive method that is currently used for the detection of spp., alternative diagnostic sampling methods...
Due to the difficulty of obtaining blood samples, which is the invasive method that is currently used for the detection of spp., alternative diagnostic sampling methods that are effective and non-invasive are needed, particularly for long-term studies. Saliva and stool samples from malaria-infected individuals contain trace amounts of DNA and therefore could be used as alternatives. Malaria was screened using rapid diagnosis tests and confirmed via microscopy. Nested PCR tests targeting the -specific gene were performed for blood, saliva and stool samples that were positive for malaria. Three hundred sixty-seven (367) children were enrolled and eighty (22.22%) were confirmed to be positive for malaria. Matched blood, saliva and stool samples were available for 35 children. By using blood smears as the gold standard for the diagnosis of malaria, our study indicates that DNA was more detectable in blood (100%) than in saliva (22.86%) and stools (14.29%). Applying qPCR to the gene to detect DNA in saliva and stool samples cannot be considered as an alternative to the current malaria detection processes using blood specimens.
PubMed: 37892092
DOI: 10.3390/diagnostics13203271 -
Malaria Journal Sep 2023Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has revolutionized identification of bacteria and is becoming available in an...
Detection and quantification of Plasmodium falciparum in human blood by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a proof of concept study.
BACKGROUND
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has revolutionized identification of bacteria and is becoming available in an increasing number of laboratories in malaria-endemic countries. The purpose of this proof-of-concept study was to explore the potential of MALDI-TOF as a diagnostic tool for direct detection and quantification of Plasmodium falciparum in human blood.
METHODS
Three different P. falciparum strains (3D7, HB3 and IT4) were cultured and synchronized following standard protocols. Ring-stages were diluted in fresh blood group 0 blood drawn in EDTA from healthy subjects to mimic clinical samples. Samples were treated with saponin and washed in PBS to concentrate protein material. Samples were analysed using a Microflex LT MALDI-TOF and resulting mass spectra were compared using FlexAnalysis software.
RESULTS
More than 10 peaks specific for P. falciparum were identified. The identified peaks were consistent among the three genetically unrelated strains. Identification was possible in clinically relevant concentrations of 0.1% infected red blood cells, and a close relationship between peak intensity and the percentage of infected red blood cells was seen.
CONCLUSION
The findings indicate that the method has the potential to detect and quantify P. falciparum at clinically relevant infection intensities and provides proof-of-concept for MALDI-TOF-based diagnosis of human malaria. Further research is needed to include other Plasmodium spp., wildtype parasite isolates and to increase sensitivity. MALDI-TOF may be a useful tool for mass-screening purposes and for diagnosis of malaria in settings where it is readily available.
Topics: Humans; Plasmodium falciparum; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Proof of Concept Study; Malaria, Falciparum; Lasers
PubMed: 37752504
DOI: 10.1186/s12936-023-04719-8 -
Clinical Infectious Diseases : An... Sep 2023The northwestern border of Thailand is an area of low seasonal malaria transmission. Until recent successful malaria elimination activities, malaria was a major cause of...
BACKGROUND
The northwestern border of Thailand is an area of low seasonal malaria transmission. Until recent successful malaria elimination activities, malaria was a major cause of disease and death. Historically the incidences of symptomatic Plasmodium falciparum and Plasmodium vivax malaria were approximately similar.
METHODS
All malaria cases managed in the Shoklo Malaria Research Unit along the Thailand-Myanmar border between 2000 and 2016 were reviewed.
RESULTS
There were 80 841 consultations for symptomatic P. vivax and 94 467 for symptomatic P. falciparum malaria. Overall, 4844 (5.1%) patients with P. falciparum malaria were admitted to field hospitals, of whom 66 died, compared with 278 (0.34%) with P. vivax malaria, of whom 4 died (3 had diagnoses of sepsis, so the contribution of malaria to their fatal outcomes is uncertain). Applying the 2015 World Health Organization severe malaria criteria, 68 of 80 841 P. vivax admissions (0.08%) and 1482 of 94 467 P. falciparum admissions (1.6%) were classified as severe. Overall, patients with P. falciparum malaria were 15 (95% confidence interval, 13.2-16.8) times more likely than those with P. vivax malaria to require hospital admission, 19 (14.6-23.8) times more likely to develop severe malaria, and ≥14 (5.1-38.7) times more likely to die.
CONCLUSIONS
In this area, both P. falciparum and P. vivax infections were important causes of hospitalization, but life-threatening P. vivax illness was rare.
Topics: Humans; Malaria; Malaria, Falciparum; Malaria, Vivax; Myanmar; Plasmodium falciparum; Plasmodium vivax; Thailand
PubMed: 37144342
DOI: 10.1093/cid/ciad262 -
Parasites & Vectors Aug 2023Malaria caused by Plasmodium species is a prominent public health concern worldwide, and the infection of a malarial parasite is transmitted to humans through the saliva...
BACKGROUND
Malaria caused by Plasmodium species is a prominent public health concern worldwide, and the infection of a malarial parasite is transmitted to humans through the saliva of female Anopheles mosquitoes. Plasmodium invasion is a rapid and complex process. A critical step in the blood-stage infection of malarial parasites is the adhesion of merozoites to red blood cells (RBCs), which involves interactions between parasite ligands and receptors. The present study aimed to investigate a previously uncharacterized protein, PbMAP1 (encoded by PBANKA_1425900), which facilitates Plasmodium berghei ANKA (PbANKA) merozoite attachment and invasion via the heparan sulfate receptor.
METHODS
PbMAP1 protein expression was investigated at the asexual blood stage, and its specific binding activity to both heparan sulfate and RBCs was analyzed using western blotting, immunofluorescence, and flow cytometry. Furthermore, a PbMAP1-knockout parasitic strain was established using the double-crossover method to investigate its pathogenicity in mice.
RESULTS
The PbMAP1 protein, primarily localized to the P. berghei membrane at the merozoite stage, is involved in binding to heparan sulfate-like receptor on RBC surface of during merozoite invasion. Furthermore, mice immunized with the PbMAP1 protein or passively immunized with sera from PbMAP1-immunized mice exhibited increased immunity against lethal challenge. The PbMAP1-knockout parasite exhibited reduced pathogenicity.
CONCLUSIONS
PbMAP1 is involved in the binding of P. berghei to heparan sulfate-like receptors on RBC surface during merozoite invasion.
Topics: Humans; Female; Animals; Mice; Plasmodium berghei; Merozoites; Protozoan Proteins; Erythrocytes; Carrier Proteins; Plasmodium falciparum
PubMed: 37563696
DOI: 10.1186/s13071-023-05896-w -
Nature Communications Feb 2024Mutations in a Plasmodium de-ubiquitinase UBP1 have been linked to antimalarial drug resistance. However, the UBP1-mediated drug-resistant mechanism remains unknown....
Mutations in a Plasmodium de-ubiquitinase UBP1 have been linked to antimalarial drug resistance. However, the UBP1-mediated drug-resistant mechanism remains unknown. Through drug selection, genetic mapping, allelic exchange, and functional characterization, here we show that simultaneous mutations of two amino acids (I1560N and P2874T) in the Plasmodium yoelii UBP1 can mediate high-level resistance to mefloquine, lumefantrine, and piperaquine. Mechanistically, the double mutations are shown to impair UBP1 cytoplasmic aggregation and de-ubiquitinating activity, leading to increased ubiquitination levels and altered protein localization, from the parasite digestive vacuole to the plasma membrane, of the P. yoelii multidrug resistance transporter 1 (MDR1). The MDR1 on the plasma membrane enhances the efflux of substrates/drugs out of the parasite cytoplasm to confer multidrug resistance, which can be reversed by inhibition of MDR1 transport. This study reveals a previously unknown drug-resistant mechanism mediated by UBP1 through altered MDR1 localization and substrate transport direction in a mouse model, providing a new malaria treatment strategy.
Topics: Animals; Mice; Plasmodium yoelii; Malaria, Falciparum; Plasmodium falciparum; Antimalarials; Drug Resistance, Multiple; Drug Resistance; Endopeptidases
PubMed: 38413566
DOI: 10.1038/s41467-024-46006-3 -
Malaria Journal Jul 2023Understanding temporal and spatial dynamics of malaria transmission will help to inform effective interventions and strategies in regions approaching elimination....
BACKGROUND
Understanding temporal and spatial dynamics of malaria transmission will help to inform effective interventions and strategies in regions approaching elimination. Parasite genomics are increasingly used to monitor epidemiologic trends, including assessing residual transmission across seasons and importation of malaria into these regions.
METHODS
In a low and seasonal transmission setting of southern Zambia, a total of 441 Plasmodium falciparum samples collected from 8 neighbouring health centres between 2012 and 2018 were genotyped using molecular inversion probes (MIPs n = 1793) targeting a total of 1832 neutral and geographically informative SNPs distributed across the parasite genome. After filtering for quality and missingness, 302 samples and 1410 SNPs were retained and used for downstream population genomic analyses.
RESULTS
The analyses revealed most (67%, n = 202) infections harboured one clone (monogenomic) with some variation at local level suggesting low, but heterogenous malaria transmission. Relatedness identity-by-descent (IBD) analysis revealed variable distribution of IBD segments across the genome and 6% of pairs were highly-related (IBD ≥ 0.25). Some of the highly-related parasite populations persisted across multiple seasons, suggesting that persistence of malaria in this low-transmission region is fueled by parasites "seeding" across the dry season. For recent years, clusters of clonal parasites were identified that were dissimilar to the general parasite population, suggesting parasite populations were increasingly fragmented at small spatial scales due to intensified control efforts. Clustering analysis using PCA and t-SNE showed a lack of substantial parasite population structure.
CONCLUSION
Leveraging both genomic and epidemiological data provided comprehensive picture of fluctuations in parasite populations in this pre-elimination setting of southern Zambia over 7 years.
Topics: Animals; Humans; Plasmodium falciparum; Parasites; Malaria, Falciparum; Zambia; Malaria; Spatial Analysis; Genomics
PubMed: 37420265
DOI: 10.1186/s12936-023-04637-9