Artemisinin-based Combination Therapy Research Articles

Anti-malarial drug use, appropriateness and associated factors among children under-five with febrile illnesses presenting to a tertiary health facility: a cross sectional study

BackgroundMalaria is endemic in 95% of Uganda and constitutes the country’s most significant public health problem—being the leading cause of morbidity and mortality, especially among children under five years of age. The current national malaria treatment policy is to use artemisinin-based combination therapy (ACT) as first-line treatment, and recommends parasitological confirmation of malaria before therapy. Adherence to this policy, however, remains suboptimal, with the self-initiated home-based therapy being common—posing undue exposures to, and pressure on the current artemisinin-based combinations, with the danger of emergence of drug resistance. The study evaluated the anti-malarial use and its appropriateness among febrile children under five presenting to a tertiary health facility in northern Uganda in light of the current malaria treatment policy.MethodsThis was a cross-sectional study in a tertiary health facility in northern Uganda between March and September 2021. Children aged 6–59 months with fever were selected using systematic random sampling. A pretested interviewer-administered questionnaire was used to collect clinical data from the caregivers. Data were analysed using SPSS version 23. Descriptive statistics and multiple logistic regression models were applied. P-value < 0.05 was considered for statistical significance.ResultsSeventy-two (34.3%) of the 210 children with fever in this study used anti-malarials prior to the hospital visit, 29.2% (21/72) of which were on a self-medication basis, 22.2% (16/72) were empiric prescriptions—all of which inappropriate, and only 48.6% (35/72) were prescribed based on a parasitological diagnosis of malaria. The most commonly used anti-malarials were artemether-lumefantrine 60/72 (88.3%), while a lesser proportion of quinine 7/72 (9.7%), artesunate 3/72 (4.2%) and dihydroartemisinin-piperaquine 2/72 (2.8%) were used. The factors independently associated with anti-malarial use among the children with febrile illnesses were duration of fever (p = 0.001); level of the nearest facility (p = 0.027), distance from the nearest health facility (p = 0.025), and caregivers’ age (p = 0.038).ConclusionsInappropriate use of anti-malarials for childhood febrile illnesses is prevalent in the study setting, facilitated by the ease of over-the-counter access, empiric prescription and use of leftover anti-malarials. This calls for a need to address communities’ health-seeking behaviour and the health providers’ practice alike.

Molecular Markers of Sulfadoxine-Pyrimethamine Resistance in Samples from Children with Uncomplicated Plasmodium falciparum at Three Sites in Angola in 2019.

Sulfadoxine-pyrimethamine (SP) is used for prevention of malaria in pregnant women in Angola. We sequenced the Plasmodium falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) genes, implicated in SP resistance, in samples collected during a 2019 study of artemisinin-based combination therapy efficacy in Benguela, Lunda Sul, and Zaire provinces. A total of 90 day 0 and day of failure samples were individually sequenced, while 508 day 0 samples from participants without recurrent parasitemia were pooled after DNA extraction into 61 pools. The N51I, C59R, and S108N pfdhfr mutations and A437G pfdhps mutations were present at high proportions in all provinces (weighted allele frequencies, 62% to 100%). The K540E pfdhps mutation was present at lower proportions (10% to 14%). The A581G pfdhps mutation was only observed in Zaire, at a 4.6% estimated prevalence. The I431V and A613S mutations were also only observed in Zaire, at a prevalence of 2.8% to 2.9%. The most common (27% to 66%) reconstructed haplotype in all three provinces was the canonical quadruple pfdhfr pfdhps mutant. The canonical quintuple mutant was absent in Lunda Sul and Benguela and present in 7.9% of samples in Zaire. A single canonical sextuple (2.6%) mutant was observed in Zaire Province. Proportions of the pfdhps K540E and A581G mutations were well below the World Health Organization thresholds for meaningful SP resistance (prevalence of 95% for K540E and 10% for A581G). Samples from therapeutic efficacy studies represent a convenient source of samples for monitoring SP resistance markers.

Identification of new oxospiro chromane quinoline-carboxylate antimalarials that arrest parasite growth at ring stage

Malaria still threatens half the globe population despite successful Artemisinin-based combination therapy. One of the reasons for our inability to eradicate malaria is the emergence of resistance to current antimalarials. Thus, there is a need to develop new antimalarials targeting Plasmodium proteins. The present study reported the design and synthesis of 4, 6 and 7-substituted quinoline-3-carboxylates 9(a–o) and carboxylic acids 10(a–b) for the inhibition of Plasmodium N-Myristoyltransferases (NMTs) using computational biology tools followed by chemical synthesis and functional analysis. The designed compounds exhibited a glide score of −9.241 to −6.960 kcal/mol for PvNMT and −7.538 kcal/mol for PfNMT model proteins. Development of the synthesized compounds was established via NMR, HRMS and single crystal X-ray diffraction study. The synthesized compounds were evaluated for their in vitro antimalarial efficacy against CQ-sensitive Pf3D7 and CQ-resistant PfINDO lines followed by cell toxicity evaluation. In silico results highlighted the compound ethyl 6-methyl-4-(naphthalen-2-yloxy)quinoline-3-carboxylate (9a) as a promising inhibitor with a glide score of −9.084 kcal/mol for PvNMT and −6.975 kcal/mol for PfNMT with IC50 values of 6.58 µM for Pf3D7 line. Furthermore, compounds 9n and 9o exhibited excellent anti-plasmodial activity (Pf3D7 IC50 = 3.96, 6.71 µM, and PfINDO IC50 = 6.38, 2.8 µM, respectively). The conformational stability of 9a with the active site of the target protein was analyzed through MD simulation and was found concordance with in vitro results. Thus, our study provides scaffolds for the development of potent antimalarials targeting both Plasmodium vivax and Plasmodium falciparum. Communicated by Ramaswamy H. Sarma

Novel Plasmodium falciparum k13 gene polymorphisms from Kisii County, Kenya during an era of artemisinin-based combination therapy deployment

BackgroundCurrently, chemotherapy stands out as the major malaria intervention strategy, however, anti-malarial resistance may hamper global elimination programs. Artemisinin-based combination therapy (ACT) stands as the drug of choice for the treatment of Plasmodium falciparum malaria. Plasmodium falciparum kelch13 gene mutations are associated with artemisinin resistance. Thus, this study was aimed at evaluating the circulation of P. falciparum k13 gene polymorphisms from Kisii County, Kenya during an era of ACT deployment.MethodsParticipants suspected to have malaria were recruited. Plasmodium falciparum was confirmed using the microscopy method. Malaria-positive patients were treated with artemether-lumefantrine (AL). Blood from participants who tested positive for parasites after day 3 was kept on filter papers. DNA was extracted using chelex-suspension method. A nested polymerase chain reaction (PCR) was conducted and the second-round products were sequenced using the Sanger method. Sequenced products were analysed using DNAsp 5.10.01 software and then blasted on the NCBI for k13 propeller gene sequence identity using the Basic Local Alignment Search Tool (BLAST). To assess the selection pressure in P. falciparum parasite population, Tajima’ D statistic and Fu & Li’s D test in DnaSP software 5.10.01 was used.ResultsOut of 275 enrolled participants, 231 completed the follow-up schedule. 13 (5.6%) had parasites on day 28 hence characterized for recrudescence. Out of the 13 samples suspected of recrudescence, 5 (38%) samples were positively amplified as P. falciparum, with polymorphisms in the k13-propeller gene detected. Polymorphisms detected in this study includes R539T, N458T, R561H, N431S and A671V, respectively. The sequences have been deposited in NCBI with bio-project number PRJNA885380 and accession numbers SAMN31087434, SAMN31087433, SAMN31087432, SAMN31087431 and SAMN31087430 respectively.ConclusionsWHO validated polymorphisms in the k13-propeller gene previously reported to be associated with ACT resistance were not detected in the P. falciparum isolates from Kisii County, Kenya. However, some previously reported un-validated k13 resistant single nucleotide polymorphisms were reported in this study but with limited occurrences. The study has also reported new SNPs. More studies need to be carried out in the entire country to understand the association of reported mutations if any, with ACT resistance.

Lumefantrine pressure selects nonsynonymous mutation in cysteine desulfurase IscS gene in the rodent malaria parasite Plasmodium berghei ANKA

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ) are the essential long-acting partner drugs in the artemisinin-based combination therapies (ACTs) treatment regimens globally. The recent report on the emergence of artemisinin-resistant parasites portends an imminent failure of the partner drug in clearing the high residual parasite densities. Understanding the resistance mechanisms to partner drugs remains critical for tracking resistant parasites. Cysteine desulfurase IscS (nfs1), one of the proteins involved in the iron-sulfur (FeS) biogenesis pathway, has been implicated in mediating malaria parasite drug resistance. Methods: Using the rodent malaria parasites Plasmodium berghei ANKA in mice, we assessed whether the nfs1 gene is associated with LM, PQ, and AQ resistance. We first verified the stability of the LM, PQ, and AQ-resistant parasites in the standard 4-Day Suppressive Test. By means of PCR and sequencing analysis, we probed for single nucleotide polymorphisms (SNPs) in the nfs1 gene. Using qPCR, we then measured the expression of the nfs1 gene in resistant parasites relative to the drug-sensitive parent parasites. Results: Our analyses of nfs1 reveal a non-synonymous Gln142Arg mutation in the LM and PQ-resistant parasites. This mutation was not detected in the AQ-resistant parasites. The mRNA quantification of the nfs1 gene reveals differential expression in both LM and PQ-resistant parasites. Conversely, nfs1 expression remained unchanged in the AQ-resistant parasites. Conclusion: Our data suggest that LM and PQ selection pressure induces nonsynonymous mutation and differential expression of the nfs1 gene in Plasmodium berghei. Collectively, these findings provide a premise for investigating LM and PQ resistance mechanisms in both P. berghei and P. falciparum.

Amodiaquine drug pressure selects nonsynonymous mutations in pantothenate kinase 1, diacylglycerol kinase, and phosphatidylinositol-4 kinase in Plasmodium berghei ANKA

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ), the long-acting components of the artemisinin-based combination therapies (ACTs), are a cornerstone of malaria treatment in Africa. Studies have shown that PQ, AQ, and LM resistance may arise independently of predicted modes of action. Protein kinases have emerged as mediators of drug action and efficacy in malaria parasites; however, the link between top druggable Plasmodium kinases with LM, PQ, and AQ resistance remains unclear. Using LM, PQ, or AQ-resistant Plasmodium berghei parasites, we have evaluated the association of choline kinase (CK), pantothenate kinase 1 (PANK1), diacylglycerol kinase (DAGK), and phosphatidylinositol-4 kinase (PI4Kβ), and calcium-dependent protein kinase 1 (CDPK1) with LM, PQ, and AQ resistance in Plasmodium berghei ANKA. Methods: We used in silico bioinformatics tools to identify ligand-binding motifs, active sites, and sequence conservation across the different parasites. We then used PCR and sequencing analysis to probe for single nucleotide polymorphisms (SNPs) within the predicted functional motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1. Using qPCR analysis, we finally measured the mRNA amount of PANK1, DAGK, and PI4Kβ at trophozoites and schizonts stages. Results: We reveal sequence conservation and unique ligand-binding motifs in the CK, PANK1, DAGK, PI4Kβ, and CDPK1 across malaria species. DAGK, PANK1, and PI4Kβ possessed nonsynonymous mutations; surprisingly, the mutations only occurred in the AQr parasites. PANK1 acquired Asn394His, while DAGK contained K270R and K292R mutations. PI4Kβ had Asp366Asn, Ser1367Arg, Tyr1394Asn and Asp1423Asn. We show downregulation of PANK1, DAGK, and PI4Kβ in the trophozoites but upregulation at the schizonts stages in the AQr parasites. Conclusions: The selective acquisition of the mutations and the differential gene expression in AQ-resistant parasites may signify proteins under AQ pressure. The role of the mutations in the resistant parasites and the impact on drug responses require further investigations in malaria parasites.

Application of Minimal Physiologically-Based Pharmacokinetic Model to Simulate Lung and Trachea Exposure of Pyronaridine and Artesunate in Hamsters.

A fixed-dose combination of pyronaridine and artesunate, one of the artemisinin-based combination therapies, has been used as a potent antimalarial treatment regimen. Recently, several studies have reported the antiviral effects of both drugs against severe acute respiratory syndrome coronavirus two (SARS-CoV-2). However, there are limited data on the pharmacokinetics (PKs), lung, and trachea exposures that could be correlated with the antiviral effects of pyronaridine and artesunate. The purpose of this study was to evaluate the pharmacokinetics, lung, and trachea distribution of pyronaridine, artesunate, and dihydroartemisinin (an active metabolite of artesunate) using a minimal physiologically-based pharmacokinetic (PBPK) model. The major target tissues for evaluating dose metrics are blood, lung, and trachea, and the nontarget tissues were lumped together into the rest of the body. The predictive performance of the minimal PBPK model was evaluated using visual inspection between observations and model predictions, (average) fold error, and sensitivity analysis. The developed PBPK models were applied for the multiple-dosing simulation of daily oral pyronaridine and artesunate. A steady state was reached about three to four days after the first dosing of pyronaridine and an accumulation ratio was calculated to be 1.8. However, the accumulation ratio of artesunate and dihydroartemisinin could not be calculated since the steady state of both compounds was not achieved by daily multiple dosing. The elimination half-life of pyronaridine and artesunate was estimated to be 19.8 and 0.4 h, respectively. Pyronaridine was extensively distributed to the lung and trachea with the lung-to-blood and trachea-to-blood concentration ratios (=Cavg,tissue/Cavg,blood) of 25.83 and 12.41 at the steady state, respectively. Also, the lung-to-blood and trachea-to-blood AUC ratios for artesunate (dihydroartemisinin) were calculated to be 3.34 (1.51) and 0.34 (0.15). The results of this study could provide a scientific basis for interpreting the dose-exposure-response relationship of pyronaridine and artesunate for COVID-19 drug repurposing.

Phytofabrication and characterization of Alchornea cordifolia silver nanoparticles and evaluation of antiplasmodial, hemocompatibility and larvicidal potential.

Purpose: The recent emergence of Plasmodium falciparum (Pf) parasites resistant to current artemisinin-based combination therapies in Africa justifies the need to develop new strategies for successful malaria control. We synthesized, characterized and evaluated medical applications of optimized silver nanoparticles using Alchornea cordifolia (AC-AgNPs), a plant largely used in African and Asian traditional medicine. Methods: Fresh leaves of A. cordifolia were used to prepare aqueous crude extract, which was mixed with silver nitrate for AC-AgNPs synthesis and optimization. The optimized AC-AgNPs were characterized using several techniques including ultraviolet-visible spectrophotometry (UV-Vis), scanning/transmission electron microscopy (SEM/TEM), powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), Fourier transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS) and Zeta potential. Thereafter, AC-AgNPs were evaluated for their hemocompatibility and antiplasmodial activity against Pf malaria strains 3D7 and RKL9. Finally, lethal activity of AC-AgNPs was assessed against mosquito larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti which are vectors of neglected diseases such as dengue, filariasis and chikungunya. Results: The AC-AgNPs were mostly spheroidal, polycrystalline (84.13%), stable and polydispersed with size of 11.77 ± 5.57nm. FTIR revealed the presence of several peaks corresponding to functional chemical groups characteristics of alkanoids, terpenoids, flavonoids, phenols, steroids, anthraquonones and saponins. The AC-AgNPs had a high antiplasmodial activity, with IC50 of 8.05μg/mL and 10.31μg/mL against 3D7 and RKL9 Plasmodium falciparum strains. Likewise, high larvicidal activity of AC-AgNPs was found after 24h- and 48h-exposure: LC50 = 18.41μg/mL and 8.97μg/mL (Culex quinquefasciatus), LC50 = 16.71μg/mL and 7.52μg/mL (Aedes aegypti) and LC50 = 10.67μg/mL and 5.85μg/mL (Anopheles stephensi). The AC-AgNPs were highly hemocompatible (HC50 > 500μg/mL). Conclusion: In worrying context of resistance of parasite and mosquitoes, green nanotechnologies using plants could be a cutting-edge alternative for drug/insecticide discovery and development.

What is the role of autoantibodies in post-artesunate delayed hemolysis?

We read with great interest the recent publication by Kurth et al.1 that highlights an interesting aspect of post-artesunate delayed hemolysis (PADH) among uncomplicated malaria patients treated with oral artemisinin-based combination therapy (ACT). Post-treatment delayed hemolysis has increasingly been observed, especially among travellers from non-endemic areas.2 Besides the well-known ‘pitting’ mechanism, the article discussed that ACT might produce drug-autoantibodies that contribute to post-treatment hemolysis. We would like to discuss the possible role of autoantibodies against red blood cells (RBC) as a pathophysiologic mechanism of PADH and the clinical implication of corticosteroid therapy for patients with PADH. Camprubí et al. (2019) reported a case of PADH in a splenectomized patient with a positive direct antiglobulin test (DAT); this raised a critical discussion as the ‘pitting’ mechanism cannot explain the hemolysis in this patient.3 The phenomenon may be explained by three hypotheses involving drug-induced immune hemolytic anaemia. First, the drug, acting as a hapten, attaches to the RBC membrane and induces autoantibody reactions. Second, the immune complex mechanism involves anti-drug antibodies produced during artesunate treatment in previous infections. Once artesunate is administered in subsequent infections, a drug-anti-drug immune complex is formed and randomly binds to the RBC surface, which activates complement fixation and opsonization, leading to cell lysis. Lastly, it assumes that the drug may act as a coating for the RBCs. If IgG antibodies against the drug are present, the reaction to the drug-coated RBCs can cause hemolysis. The immune complex mechanism may explain the high levels of autoantibodies found among ‘semi-immune’ patients of African descent who developed PADH in the recent study by Kurth et al.

Quantification of parasite clearance in Plasmodium knowlesi infections

BackgroundThe incidence of zoonotic Plasmodium knowlesi infections in humans is rising in Southeast Asia, leading to clinical studies to monitor the efficacy of anti-malarial treatments for knowlesi malaria. One of the key outcomes of anti-malarial drug efficacy is parasite clearance. For Plasmodium falciparum, parasite clearance is typically estimated using a two-stage method, that involves estimating parasite clearance for individual patients followed by pooling of individual estimates to derive population estimates. An alternative approach is Bayesian hierarchical modelling which simultaneously analyses all parasite-time patient profiles to determine parasite clearance. This study compared these methods for estimating parasite clearance in P. knowlesi treatment efficacy studies, with typically fewer parasite measurements per patient due to high susceptibility to anti-malarials.MethodsUsing parasite clearance data from 714 patients with knowlesi malaria and enrolled in three trials, the Worldwide Antimalarial Resistance Network (WWARN) Parasite Clearance Estimator (PCE) standard two-stage approach and Bayesian hierarchical modelling were compared. Both methods estimate the parasite clearance rate from a model that incorporates a lag phase, slope, and tail phase for the parasitaemia profiles.ResultsThe standard two-stage approach successfully estimated the parasite clearance rate for 678 patients, with 36 (5%) patients excluded due to an insufficient number of available parasitaemia measurements. The Bayesian hierarchical estimation method was applied to the parasitaemia data of all 714 patients. Overall, the Bayesian method estimated a faster population mean parasite clearance (0.36/h, 95% credible interval [0.18, 0.65]) compared to the standard two-stage method (0.26/h, 95% confidence interval [0.11, 0.46]), with better model fits (compared visually). Artemisinin-based combination therapy (ACT) is more effective in treating P. knowlesi than chloroquine, as confirmed by both methods, with a mean estimated parasite clearance half-life of 2.5 and 3.6 h, respectively using the standard two-stage method, and 1.8 and 2.9 h using the Bayesian method.ConclusionFor clinical studies of P. knowlesi with frequent parasite measurements, the standard two-stage approach (WWARN’s PCE) is recommended as this method is straightforward to implement. For studies with fewer parasite measurements per patient, the Bayesian approach should be considered. Regardless of method used, ACT is more efficacious than chloroquine, confirming the findings of the original trials.

Structure-Based Optimization of Protease-Inhibitor Interactions to Enhance Specificity of Human Stefin-A against Falcipain-2 from the Plasmodium falciparum 3D7 Strain.

The emergence of resistance in Plasmodium falciparum to frontline artemisinin-based combination therapies has raised global concerns and emphasized the identification of new drug targets for malaria. Cysteine protease falcipain-2 (FP2), involved in host hemoglobin degradation and instrumental in parasite survival, has long been proposed as a promising malarial drug target. However, designing active-site-targeted small-molecule inhibitors of FP2 becomes challenging due to their off-target specificity toward highly homologous human cysteine cathepsins. The use of proteinaceous inhibitors, which have nonconserved exosite interactions and larger interface area, can effectively circumvent this problem. In this study, we report for the first time that human stefin-A (STFA) efficiently inhibits FP2 with Ki values in the nanomolar range. The FP2-STFA complex crystal structure, determined in this study, and sequence analyses identify a unique nonconserved exosite interaction, compared to human cathepsins. Designing a mutation Lys68 > Arg in STFA amplifies its selectivity garnering a 3.3-fold lower Ki value against FP2, and the crystal structure of the FP2-STFAK68R complex shows stronger electrostatic interaction between side-chains of Arg68 (STFAK68R) and Asp109 (FP2). Comparative structural analyses and molecular dynamics (MD) simulation studies of the complexes further confirm higher buried surface areas, better interaction energies for FP2-STFAK68R, and consistency of the newly developed electrostatic interaction (STFA-R68-FP2-D109) in the MD trajectory. The STFA-K68R mutant also shows higher Ki values against human cathepsin-L and stefin, a step toward eliminating off-target specificity. Hence, this work underlines the design of host-based proteinaceous inhibitors against FP2, with further optimization to render them more potent and selective.

Malaria in Children: Updates on Management and Prevention.

Malaria in Children: Updates on Management and Prevention.

Neurobehavioral and biochemical responses to artemisinin-based drug and aflatoxin B1 co-exposure in rats.

Populations in malaria endemic areas are frequently exposed to mycotoxin-contaminated diets. The possible toxicological outcome of co-exposure to dietary aflatoxin B1 (AFB1) and artemisinin-based combination therapy warrants investigation to ascertain amplification or attenuation of cellular injury. Here, we investigated the neurobehavioral and biochemical responses associated with co-exposure to anti-malarial drug coartem, an artemether-lumefantrine combination (5mg/kg body weight, twice a day and 3days per week) and AFB1 (35 and 70µg/kg body weight) in rats. Motor deficits, locomotor incompetence, and anxiogenic-like behavior induced by low AFB1 dose were significantly (p < 0.05) assuaged by coartem but failed to rescue these behavioral abnormalities in high AFB1-dosed group. Coartem administration did not alter exploratory deficits typified by reduced track plot densities and greater heat map intensity in high AFB1-dosed animals. Furthermore, the reduction in cerebral and cerebellar acetylcholinesterase activity, anti-oxidant enzyme activities, and glutathione and thiol levels were markedly assuaged by coartem administration in low AFB1 group but not in high AFB1-dosed animals. The significant attenuation of cerebral and cerebellar oxidative stress indices namely reactive oxygen and nitrogen species, xanthine oxidase activity, and lipid peroxidation by coartem administration was evident in low AFB1 group but not high AFB1 dose. Although coartem administration abated nitric oxide level, activities of myeloperoxidase, caspase-9, and caspase-3 in animals exposed to both doses of AFB1, these indices were significantly higher than the control. Coartem administration ameliorated histopathological and mophometrical changes due to low AFB1 exposure but not in high AFB1 exposure. In conclusion, contrary to AFB1 alone, behavioral and biochemical responses were not altered in animals singly exposed to coartem. Co-exposure to coartem and AFB1 elicited no additional risk but partially lessened neurotoxicity associated with AFB1 exposure.

Short tandem repeat polymorphism in the promoter region of cyclophilin 19B drives its transcriptional upregulation and contributes to drug resistance in the malaria parasite Plasmodium falciparum.

Resistance of the human malaria parasites, Plasmodium falciparum, to artemisinins is now fully established in Southeast Asia and is gradually emerging in Sub-Saharan Africa. Although nonsynonymous SNPs in the pfk13 Kelch-repeat propeller (KREP) domain are clearly associated with artemisinin resistance, their functional relevance requires cooperation with other genetic factors/alterations of the P. falciparum genome, collectively referred to as genetic background. Here we provide experimental evidence that P. falciparum cyclophilin 19B (PfCYP19B) may represent one putative factor in this genetic background, contributing to artemisinin resistance via its increased expression. We show that overexpression of PfCYP19B in vitro drives limited but significant resistance to not only artemisinin but also piperaquine, an important partner drug in artemisinin-based combination therapies. We showed that PfCYP19B acts as a negative regulator of the integrated stress response (ISR) pathway by modulating levels of phosphorylated eIF2α (eIF2α-P). Curiously, artemisinin and piperaquine affect eIF2α-P in an inverse direction that in both cases can be modulated by PfCYP19B towards resistance. Here we also provide evidence that the upregulation of PfCYP19B in the drug-resistant parasites appears to be maintained by a short tandem repeat (SRT) sequence polymorphism in the gene's promoter region. These results support a model that artemisinin (and other drugs) resistance mechanisms are complex genetic traits being contributed to by altered expression of multiple genes driven by genetic polymorphism at their promoter regions.

Synergistic antimalarial treatment of Plasmodium berghei infection in mice with dihydroartemisinin and Gymnema inodorum leaf extract

BackgroundChemotherapy is crucial in the fight against malaria. The rise of resistance to most antimalarial medicines has been a serious hurdle to effective treatment. Artemisinin-based combination therapies (ACTs) are currently the most effective antimalarial medication. Malaria parasites are growing more resistant to ACTs, particularly in Southeast Asia. As a result, effective alternative antimalarials are in high demand. The leaf extract of Gymnema inodorum (GIE) has previously shown promise as an effective antimalarial. Therefore, this study evaluated the antimalarial potential of combination dihydroartemisinin (DHA) and GIE therapy against Plasmodium berghei in a mouse model.MethodsThe medications were evaluated using the standard 4-day test for determining the 50% effective dosage (ED50) of DHA and GIE on P. berghei ANKA (PbANKA). DHA and GIE were combined using a fixed-ratio approach, with DHA/GIE ED50s of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100, respectively.ResultsThe ED50 against PbANKA was determined to be 2 mg/kg of DHA and 100 mg/kg of GIE. The 60/40 (DHA/GIE) ratio demonstrated significantly higher antimalarial activity than the other ratios (p < 0.001) against PbANKA, with 88.95% inhibition, suggesting synergistic efficacy (combination index (CI) = 0.68695). Furthermore, this ratio protected PbANKA-infected mice against loss of body weight and packed cell volume decline, leading to a longer survival time over 30 days.ConclusionOur results suggest that GIE could be an effective adjuvant to DHA that can enhance the antimalarial effects in the treatment of PbANKA-infected mice.

Revealing the artemisinin and piperaquine treatment failure: a systematic review

Background: Artemisinin-based combination therapy (ACT) consists of a potent artemisinin component. Since the dihydroartemisinin performance effectiveness depends on piperaquine interaction still challenging, further research needs to establish the current status of artemisinin resistance relative to its geography and recognize any drug resistance interaction between dihydroartemisinin and piperaquine. Aim: This systematic review was aimed to find out the effect of dihydroartemisinin and piperaquine interaction concerning resistance, recurrence, parasitological failure, clinical failure, parasite clearance time, parasite reduction ratio, cure rate, which may affect treatment failure of patients with uncomplicated P. falciparum. Method: The article was not limited to year and country. This study analyzed any effect of interaction. Pubmed and Scopus were used as electronic databases, and MeSH terms and keywords were used to find specific studies. A total of 2131 studies were initially identified; however, 20 were eligible for qualitative synthesis. Result: The dihydroartemisinin piperaquine cure rate reported in Asia and Africa was above 98%. Eight RCTs, eleven prospective cohort studies, and one retrospective and prospective cohort study were included in this review. Design studies did not compare the same anti-malarial drug pattern, so it was difficult to do a pooled analysis. Even though this drug combination did not show a clear description of piperaquine resistance can affect artemisinin resistance, the adequate clinical and parasitological failure (ACPR) from this research reached above 93%, and for early treatment failure (ETF), late clinical failure (LCF), and late parasitological failure (LPF), were almost 0 %. Conclusion: The dihydroartemisinin-piperaquine combination still has highly efficacious therapy to fight malaria in some areas based on these multiple factors and reviews.

-Pharmacokinetics of antimalarial drugs used to treat uncomplicated malaria in breastfeeding mother-infant pairs: An observational pharmacokinetic study.

Background: Data surrounding the exposure of the breastfed infant to drugs and any associated risks are sparse. Drugs usually are transferred to milk in small quantities, and many have been used without obviously noticeable infant toxicity for many years - this lack of a 'safety signal' has further reduced the interest in studying mother-to-infant transfer of the drugs. In sub-Saharan Africa, pregnant women are at risk of Plasmodium falciparuminfection, and one in four women have evidence of placental infection at the time of delivery. Artemisinin-based combination therapies (ACTs), primarily artemether-lumefantrine (AL), are the current first-line treatment for uncomplicated Plasmodium falciparum malaria, with the same dosing recommendations in breastfeeding women as those in the adult population. Dihydroartemisinin-piperaquine (DP) is routinely used as an alternative to AL in Uganda. However, lactation pharmacokinetics (PK) of ACTs are unknown. Pharmacokinetic characterization of anti-malarial transfer to breast milk and breastfed infants is crucial in understanding the potential consequences to the infant, in terms of therapeutic- and prophylactic effects as well as potential toxicity. Methods: This observational study will enroll 30 mother-infant pairs, and aims to characterize the breastmilk transfer of antimalarial medications (AL and DP) to infants when these ACTs are administered to mothers as part of treatment for uncomplicated malaria. In addition, we will assess the mental health of the breastfeeding mothers enrolled as well as the well-being of their children. PK samples of maternal blood, breastmilk and breastfeeding infant's blood will be obtained at specific times points. Pharmacokinetic data will be analyzed using a population pharmacokinetic approach. Conclusions: We anticipate that findings from this research will guide to develop a PK model describing lumefantrine and piperaquine disposition and will provide a framework to foster other lactation pharmacokinetic studies in different disease areas.

Parasitology and Covid-19: epidemiological, immunological, pathological, and therapeutic aspects

&lt;abstract&gt; &lt;p&gt;Studies suggest that there is a complex interaction between parasitic infections, human microbiota, and host immunity. Reports have shown that there is the prevalence of viral diseases have inverse correlations with their severities (as is the case for Covid-19), their resulting mortalities, and helminth infections in endemic areas. This review study was conducted to discover the possible association between parasitic infections and Covid-19 epidemics from immunological, pathological, and therapeutic aspects. Our studies were conducted by reviewing texts, reports, and articles on reputable websites such as PubMed, Science Direct, medRxvi, Google Scholar, and bioRxiv published by 2022 07 April for keywords such as a parasite, helminth, radioactive, COVID-19 or SARS-CoV-2. In particular, reports of co-infection with helminths with complications and severity of Covid-19 in endemic areas were considered. The findings indicate that parasitic helminths can regulate host immune responses associated with a viral infection. For example, intestinal parasitic infections may be effective in reducing the symptoms of SARS-CoV-2 and the complications of Covid-19. Infected hosts can induce an innate and Th2-compatible immune response to CD4&lt;sup&gt;+&lt;/sup&gt; T cells, eosinophils, and interleukins (IL-4, IL-5, and IL-10). Chronic helminth infections prevent strong immune responses by altering the host response to T helper 2 (Th2). Interestingly, some antimalarial drugs, such as Artemisinin-based combination therapies (ACTs), may inhibit SARS-CoV-2-induced severe acute respiratory syndrome (SARS). Parasitic infections may alter the host's immune response to SARS-CoV-2 with potentially beneficial or detrimental effects. However, more large-scale epidemiological studies are needed to uncover the links between parasitic infections and COVID-19 and to clarify existing ambiguities.&lt;/p&gt; &lt;/abstract&gt;

Development, Optimization, and Validation of a Novel HPLC Method for Simultaneous Quantification of Artesunate and Amodiaquine in Tablet Formulations

Artemisinin-based combination therapy (ACTs) has become the primary first-line treatment for mild falciparum malaria in the majority of African countries. A fixed-dose combination of amodiaquine and artesunate is commonly employed to enhance treatment compliance and achieve successful malaria outcomes. In this study, a specific, accurate, linear, precise, and repeatable method was optimized, verified, and applied for the simultaneous estimation of artesunate and amodiaquine HCl in a commercially available artesunate-amodiaquine tablet with a dosage of 100 mg/270 mg. The optimization process involved two steps. Firstly, the top three were carefully selected out of seven characteristics influencing the separation. These key elements required fine-tuning, namely the column type, ion pair, and the residual amount of acetonitrile (ACN) remaining after elution. In the second step, a Box-Behnken experimental design, coupled with Derrenguer's desirability approach, was utilized to identify the ideal target conditions. The optimized method demonstrated excellent specificity, accuracy, linearity, precision, and repeatability, allowing for the reliable simultaneous estimation of artesunate and amodiaquine HCl in the artesunate-amodiaquine tablet. This method offers a valuable tool for quality control and dosage determination in the pharmaceutical industry. By employing advanced experimental techniques and focusing on critical parameters, the study contributes to analytical methodologies in malaria treatment.

Investigation of new ferrocenyl-artesunate derivatives as antiparasitics.

Artesunate (Ars) is a semisynthetic antimalarial drug and is a part of the artemisinin-based combination therapy arsenal employed for malaria treatment. The drug functions mainly by activation of its endoperoxide bridge leading to increased oxidative stress in malaria parasites. The purpose of this study was to ascertain the antiparasitic effects of combining ferrocene and Arsvia short or long chain ester or amide linkages (C1-C4). The compounds were evaluated for growth inhibition activity on the apicomplexan parasites, Plasmodium falciparum (P. falciparum) and Toxoplasma gondii (T. gondii). All the complexes demonstrated good activity against T. gondii with IC50 values in the low micromolar range (0.28-1.2 μM) and good to excellent antimalarial activity against a chloroquine sensitive strain of P. falciparum (NF54). Further investigations on T. gondii revealed that the likely mode of action (MoA) is through the generation of reactive oxygen species. Additionally, immunofluorescence microscopy suggested a novel change in the morphology of the parasite by complex C3, an artesunate-ferrocenyl ethyl amide complex. The complexes were not cytotoxic or showed low cytotoxicity to two normal cell lines tested.