Drug-resistant Malaria Research Articles

Delving into artemisinin’s shadow: Insights from a unique case of artesunate – resistant complicated falciparum malaria

The emergence of drug-resistant malaria poses a formidable health challenge in emerging nations such as India. The ineffectiveness of the medicine artemisinin, which is essential for treating malaria, will quickly undermine the treatment and outlook for malaria patients. If, following a complete course of therapy with Artesunate Combination Therapy and without any instances of vomiting or diarrhoea, there is no clinical or parasitological improvement in the patient within 72 hours, resistance may be considered. Reports of artemisinin-resistant Plasmodium falciparum malaria are rare in the southern regions of India. This article details a case of rare Artesunate-resistant complex falciparum malaria.

Detection of drug-resistant malaria in resource-limited settings: efficient and high-throughput surveillance of artemisinin and partner drug resistance.

Artemisinin-resistant Plasmodium falciparum malaria is currently spreading globally, including in Africa. Artemisinin resistance also leads to resistance to partner drugs used in artemisinin-based combination therapies. Sequencing of kelch13, which is associated with artemisinin resistance, culture-based partner drug susceptibility tests, and ELISA-based growth measurement are conventionally used to monitor resistance; however, their application is challenging in resource-limited settings. An experimental package for field studies with minimum human/material requirements was developed. First, qPCR-based SNP assay was applied in artemisinin resistance screening, which can detect mutations within 1 h and facilitate sample selection for subsequent processes. It had 100% sensitivity and specificity compared with DNA sequencing in the detection of the two common artemisinin resistance mutations in Uganda, C469Y and A675V. Moreover, in the partner drug susceptibility test, the cultured samples were dry-preserved on a 96-well filter paper plate and shipped to the central laboratory. Parasite growth was measured by ELISA using redissolved samples. It well reproduced the results of direct ELISA, reducing significant workload in the field (Pearson correlation coefficient: 0.984; 95% CI: 0.975-0.990). Large-scale and sustainable monitoring is required urgently to track rapidly spreading drug-resistant malaria. In malaria-endemic areas, where research resources are often limited, simplicity and feasibility of the procedure is especially important. Our approach combines a qPCR-based rapid test, which is also applicable to point-of-care diagnosis of artemisinin resistance and centralized analysis of ex vivo culture. The approach could improve efficiency of field experiments and accelerate global drug resistance surveillance.

Global Health Priority Box: Discovering Flucofuron as a Promising Antikinetoplastid Compound.

Leishmaniasis, produced by Leishmania spp., and Chagas disease, produced by Trypanosoma cruzi, affect millions of people around the world. The treatments for these pathologies are not entirely effective and produce some side effects. For these reasons, it is necessary to develop new therapies that are more active and less toxic for patients. Some initiatives, such as the one carried out by the Medicines for Malaria Venture, allow for the screening of a large number of compounds of different origins to find alternatives to the lack of trypanocide treatments. In this work, 240 compounds were tested from the Global Health Priority Box (80 compounds with confirmed activity against drug-resistant malaria, 80 compounds for screening against neglected and zoonotic diseases and diseases at risk of drug resistance, and 80 compounds with activity against various vector species) against Trypanosoma cruzi and Leishmania amazonensis. Flucofuron, a compound with activity against vectors and with previous activity reported against Staphylococcus spp. and Schistosoma spp., demonstrates activity against L. amazonensis and T. cruzi and produces programmed cell death in the parasites. Flucofuron seems to be a good candidate for continuing study and proving its use as a trypanocidal agent.

Evaluation of the antiplasmodial efficacy of synthetic 2,5-diphenyloxazole analogs of compounds naturally derived from Oxytropis lanata

The persistent prevalence and dissemination of drug-resistant malaria parasites continue to challenge the progress of malaria eradication efforts. As a result, there is an urgent need to search for and develop innovative therapies. In this study, we screened synthetic 2,5-diphenyloxazole analogs from Oxytropis lanata. Among 48 compounds, 14 potently inhibited the proliferation of P. falciparum strains 3D7 (chloroquine-sensitive) and K1 (multidrug-resistant) in vitro, exhibited IC50 values from 3.38 to 12.65 μM and 1.27–6.19 μM, respectively, and were toxic to human foreskin fibroblasts at 39.53–336.35 μM. Notably, Compounds 31 (2-(2′,3′-dimethoxyphenyl)-5-(2″-hydroxyphenyl)oxazole) and 32 (2-(2′,3′-dimethoxyphenyl)-5-(2″-benzyloxyphenyl)oxazole) exhibited the highest selectivity indices (SIs) against both P. falciparum strains (3D7/K1), with values > 40.20/>126.58 and > 41.27/> 59.06, respectively. In the IC50 speed and stage-specific assays, Compounds 31 and 32 showed slow action, along with distinct effects on the ring and trophozoite stages. Microscopy observations further revealed that both compounds impact the development and delay the progression of the trophozoite and schizont stages in P. falciparum 3D7, especially at concentrations 100 times their IC50 values. In a 72-h in vitro exposure experiment at their respective IC80 in P. falciparum 3D7, significant alterations in parasitemia levels were observed compared to the untreated group. In Compound 31-treated cultures, parasites shrank and were unable to reinvade red blood cells (RBCs) during an extended 144-h incubation period, even after compound removal from the culture. In vivo assessments were conducted on P. yoelii 17XNL-infected mice treated with Compounds 31 and 32 at 20 mg/kg administered once daily for ten days. The treated groups showed statistically significant lower peaks of parasitemia (Compound 31-treated: trial 1 12.7%, trial 2 15.8%; Compound 32-treated: trial 1 12.7%, trial 2 14.0%) compared to the untreated group (trial 1 21.7%, trial 2 28.3%). These results emphasize the potential of further developing 2,5-diphenyloxazoles as promising antimalarial agents.

Antimalarial potential of Kerala Ayurvedic Water "Pathimugam".

The persistent threat of drug resistant malaria demands new cures. Low prevalence of malaria in the Indian state of Kerala compared with other proximal states led us to explore if there is any traditional practice in Kerala which may confer protection against malaria. In this context, our attention was drawn to "Pathimugam" i.e., Ceasalpinia sappan whose heartwood is used to prepare a red aqueous extract which is a uniquely popular drink all over Kerala. Aqueous and methanolic extracts of various organs of C. sappan were prepared and tested against Plasmodium falciparum grown in vitro culture using SYBR Green-I assay. The cytotoxicity of active extracts/fractions was studied using mammalian HeLa cell line. In vivo efficacy was determined using Plasmodium berghei ANKA infected mice. The highest antiplasmodial activities in the alcoholic and aqueous extracts were observed in leaf methanolic extract (IC 2 μg/ml) and heartwood aqueous extract (IC 12.5 μg/ml). C. sappan extracts were equipotent against both chloroquine sensitive Pf3D7 and resistant Pf INDO strains and showed suppression of % parasitemia in P. berghei infected mice. Activity guided chromatographic fractionation of aqueous wood extract led to the fortification of antiplasmodial activity (IC 5 μg/ml). Our results establish the antiplasmodial potential of C. sappan and suggest that its regular use might have prophylactic or curative actions that may assist in keeping check on malaria in the Indian state of Kerala.

Evaluation of antiplasmodial effects of black seeds, fenugreek and coriander seeds in albino mice infected with <i>Plasmodium berghei.</i>

Malaria remains a disease of public concern according to reports by the World Health Organization which recommends diverse therapeutic approach including the use of plant derived products to combat drug resistance in malaria treated individuals. This study therefore, evaluates the antiplasmodial effects of black seeds (Nigella sativa), fenugreek (Trigonella foenum-graecum) and coriander seeds (Coriandrum sativum) and their effects on packed cell volume and weight of experimental mice. Phytochemical analysis of the extract was conducted using Gas Chromatography-Mass Spectrometry analysis to establish the presence of antimalarial constituents. The plant extracts were screened for curative activities at dosages of 50mg/kg, 100mg/kg and 200mg/kg, in mice inoculated with Plasmodium berghei from donor mice. Chloroquine (6mg/kg body weight) was used as standard control drug. A 4-day curative assay was used to evaluate the antimalarial potentials of the plant extracts. Comparison between treated samples were analyzed using single factor analysis of variance at 95% confidence interval and 5% significance level (P<0.05). The results obtained from this study revealed significant suppression rate at 50mg/kg for Nigella sativa (67.0%), 200mg/kg for Trigonella foenum-graecum (68.3%), and 200mg/kg for Coriandrum sativum (66.7%). Chloroquine (6mg/kg) showed a higher inhibitory performance at 86.6% on day 7 post treatment compared to the plant extracts. The packed cell volume increased in groups treated with chloroquine compared to the extract treated group while the weight of mice increased in all extract groups significantly compared to the chloroquine treated group. The results of the study were statistically significant at P<0.05.

Isoliquiritigenin from licorice root: A multi-stage anti-malarial with synergistic impact on multidrug-resistant P. falciparum

IntroductionMalaria control is hindered by drug-resistant parasites, leading to a shortage of effective drugs. There is a need to find new, better antimalarial drug. Traditional Chinese Medicine (TCM) are more accessible and cheaper alternative for combating resistance in the treatment of malaria, therefore the anti-malarial efficacy of root extracts and isolated phytomolecules from Glycyrrhiza glabra L was assessed. MethodsThe anti-plasmodial potential of root extracts and isolated phytomolecules from Glycyrrhiza glabra L. was assessed using the Giemsa staining method. In- vivo, antimalarial efficacy was evaluated by conducting a four-day suppression test in a mouse model. The mechanistic studies of ISL were carried out using caspase-like activity, mitochondrial membrane potential, and reactive oxygen species (ROS) assay. Further, proteomics analysis was carried out by LC-MS/MS. The interaction of the combinations was evaluated using the fixed ratio method by calculating the fractional inhibitory concentration (FIC). ResultsExtracts of G. glabra contain Phytomolecule(s) with moderate anti-plasmodial activity against multidrug-resistant strain (K1) of P. falciparum. Isoliquiritigenin (ISL) exhibited a significant reduction in parasitemia, resulting in an enhancement of the mean survival time in Plasmodium yoelii nigeriensis infected mice. ISL showed potent activity with no cytotoxic effect and increased caspase-3 activity, leading increasing reactive oxygen species (ROS) and loss of mitochondrial potential. ISL also displayed synergy with chloroquine, glabridin and liquiritigenin against multi-drug-resistant P. falciparum. DiscussionThe present study found ISL to be a potential phytomolecule of G. glabra. The study explored the mechanism of action of ISL and suggested its suitability for further study in managing drug-resistant malaria.

Repurposing FDA-approved drugs to target malaria through inhibition of dihydrofolate reductase in the folate biosynthesis pathway: A prospective approach.

Dihydrofolate reductase (DHFR) is a ubiquitous enzyme that regulates the biosynthesis of tetrahydrofolate among various species of Plasmodium parasite. It is a validated target of the antifolate drug pyrimethamine (Pyr) in Plasmodium falciparum (Pf), but its clinical efficacy has been hampered due to the emergence of drug resistance. This has made the attempt to screen Food & Drug Administration-approved drugs against wild- and mutantPfDHFR by employing an in-silico pipeline to identify potent candidates. The current study has followed a virtual screening approach for identifying potential DHFR inhibitors from DrugBank database, based on a structure similarity search of candidates, followed by absorption, distribution, metabolism, and excretion estimation. The screened drugs were subjected to various parameters like docking, molecular mechanics with generalized born and surface area solvation calculations, and molecular simulations. We have thus identified twopotential drug candidates, duloxetine and guanethidine, which can be repurposed to be tested for their efficacy against wild type and drug resistant falciparum malaria.

Epidemiological behaviour and interventions of malaria in Niger, 2010–2019: a time-series analysis of national surveillance data

BackgroundMalaria remains a significant public health concern in Niger, with the number of cases increasing from 592,334 in 2000 to 3,138,696 in 2010. In response, a concerted campaign against the disease has been initiated. However, the implementation of these malaria interventions and their association with epidemiological behaviour remains unclear.MethodsA time-series study was conducted in Niger from 2010 to 2019. Multiple data sources concerning malaria were integrated, encompassing national surveillance data, Statistic Yearbook, targeted malaria control interventions, and meteorological data. Incidence rate, mortality rate, and case fatality ratio (CFR) by different regions and age groups were analysed. Joinpoint regression models were used to estimate annual changes in malaria. The changes in coverage of malaria interventions were evaluated.ResultsBetween 2010 to 2019, the incidence rate of malaria decreased from 249.43 to 187.00 cases per 1,000 population in Niger. Niamey had a high annual mean incidence rate and the lowest CFR, while Agadez was on the contrary. Joinpoint regression analysis revealed a declining trend in malaria incidence for all age groups except the 10–24 years group, and the mortality rate and the CFR initially decreased followed by an increase in all age groups. Niger has implemented a series of malaria interventions, with the major ones being scaled up to larger populations during the study period.ConclusionsThe scale-up of multi-interventions in Niger has significantly reduced malaria incidence, but the rise in mortality rate and CFR addresses the challenges in malaria control and elimination. Malaria endemic countries should enhance surveillance of malaria cases and drug resistance in Plasmodium, improve diagnosis and treatment, expand the population coverage of insecticide-treated bed nets and seasonal malaria chemoprevention, and strengthen the management of severe malaria cases.

Sulfonamide based pyrimidine derivatives combating Plasmodium parasite by inhibiting falcipains-2 and falcipains-3 as antimalarial agents.

In this report, we present the design and synthesis of a novel series of pyrimidine-tethered spirochromane-based sulfonamide derivatives aimed at combating drug resistance in malaria. The antimalarial effectiveness of these compounds was assessed in vitro. Structural validation of the synthesized compounds was conducted using mass spectrometry and NMR spectroscopy. Strong antimalarial activity against CQ-sensitive (3D7) and CQ-resistant (W2) strains of Plasmodium falciparum was demonstrated by the majority of the compounds. Notably, compounds SZ14 and SZ9 demonstrated particularly potent effects, with compound SZ14 showing IC50 values of 2.84 μM and SZ9 3.22 μM, indicating single-digit micromolar activity. The compounds exhibiting strong antimalarial activity were assessed through enzymatic tests against the cysteine protease enzymes of P. falciparum, falcipain-2 and falcipain-3. The results indicated that SZ14 and SZ9 inhibited PfFP-2 (IC50 values: 4.1 and 5.4 μM, respectively), and PfFP-3 (IC50 values: 4.9 and 6.3 μM, respectively). To confirm the compounds' specificity towards the parasite, we investigated their cytotoxicity against Vero cell lines, revealing strong selectivity indices and no significant cytotoxic effects. Additionally, in vitro hemolysis testing showed these compounds to be non-toxic to normal human blood cells. Moreover, predicted in silico ADME parameters and physiochemical characteristics demonstrated the drug-likeness of the synthetic compounds. These collective findings suggest that sulfonamide derivatives based on pyrimidine-tethered oxospirochromane could serve as templates for the future development of potential antimalarial drugs.

Haematological Profile and Antibiotic Resistance of Bacteria Responsible for Enteric Infections Isolated From Patients Suffering From Malaria and Enteric Infections on Consultation at the Dschang Regional Hospital.

Malarial and bacterial coinfections in low-income countries are a serious cause of morbidity and mortality, necessitating coadministration of antibiotics and antimalarials. This study investigated the relationship between malaria infection and bacterial drug resistance in malaria and nonmalaria patients on consultation at the Dschang Regional Hospital. A follow-up study was carried out from October 2020 to December 2021 on 127 malaria and 174 nonmalaria patients having enteric infections. Clinical and haematological parameters were measured using standard methods. CD4 and CD8 cells were determined using flow cytometry. Enteric bacteria pathogens were isolated from stool, and antimicrobial and antimalarial profiles were determined using agar diffusion and microdilution methods, respectively. Significant reduction of RBCs, WBCs, CD4, CD8, granulocytes, monocytes and platelets was seen in coinfected patients compared to monoinfected participants (p ≤ 0.0491). E. coli was the main pathogenic bacteria isolated from the digestive tract of coinfected patients (40.63%) and monoinfected patients (59.37%). E. coli showed a high level of resistance to AMX (57.69%) and CDA (61.54%) in coinfected patients compared to 55.26% and 41.67%, respectively, in monoinfected patients. Quinine (53[50.00%]; 6[42.86%]) presented a minimal inhibitory concentration (MIC) of 32 μg/mL on the bacteria isolates from coinfected and monoinfected patients, respectively, while Artemether 89 (83.96%), Maloxine 5 (3.94%) and Surquina 250 (39.37%) presented a MIC of 64 μg/mL on bacterial isolates of coinfected and monoinfected patients. E. coli showed high resistance against AKI (45.93%), AMX (43.75%) and ERY (59.37%) in malaria patients who were under antimalarial drugs compared to malaria patients who were not under malaria drugs (29.68%, 34.37% and 32.81%, respectively). This study highlights that antimalarial drugs might certainly have an influence on the acquisition and emergence of bacterial resistance in the case of malaria bacterial coinfection, and therefore, adequate management and planning effective control programmes might certainly go a long way to reduce the rate of morbidity and mortality.

Antimalarial Drug Resistance in Africa: Current Status and Future Prospects

Malaria remains a significant public health concern in Africa, with millions of cases reported annually. However, the effectiveness of antimalarial drugs, a cornerstone of malaria control efforts, is threatened by the emergence and spread of drug-resistant strains of the Plasmodium parasite. This article provides a comprehensive overview of the current status of antimalarial drug resistance in Africa and explores prospects for combatting this critical issue. In recent years, various regions across the continent have witnessed the rise of drug-resistant malaria strains, posing formidable challenges to malaria treatment and control programs. We delve into the underlying genetic and molecular mechanisms driving drug resistance, shedding light on the role of mutations and the evolutionary forces at play. Despite these challenges, ongoing research and global collaborations offer hope for the future. Combination therapies, innovative drug development, and vector control measures are discussed as strategies to mitigate drug resistance. We also explore the potential of genomics and molecular studies in understanding and countering resistance. However, significant barriers persist, including limited funding, resource disparities, and access to healthcare in remote areas. Socioeconomic factors further complicate the landscape of malaria control. In conclusion, this article underscores the urgency of addressing antimalarial drug resistance in Africa as a public health priority. By staying informed about the current status, supporting research initiatives, and promoting effective policies and interventions, we can strive for a future where malaria treatment remains effective and accessible to all, ultimately working toward the goal of malaria eradication on the African continent.

Development and Characterization of Novel Chitosan-Coated Curcumin Nanophytosomes for Treating Drug-Resistant Malaria.

This study aimed at enhancing the efficacy of curcumin (CR) by formulating and coating it with chitosan. In silico molecular docking studies revealed that CR exhibited almost similar and low binding energies when compared to artemisinin, indicating high stability at the target site. It can be confirmed that CR is effective in treating and reducing Plasmodium falciparum parasites. Fourier transform infrared studies confirmed that there was a shift and disappearance of some drug peaks in the formulation which revealed complexation with phospholipids. The F2EXT3-developed formulation exhibited greater solubility (24.31 ± 3.47 μg/mL) when compared to pure CR (7.99 ± 1.95 μg/mL). Proton nuclear magnetic resonance studies confirmed the formation of Curcumin-phospholipid hydrogen bonding in F2EXT3. The in vitro drug release studies revealed that the developed formulation F2EXT3 exhibited better drug release at 71.98% at 48 h; this might be due to the effective entrapment efficiency of the drug inside the phospholipid, presence of polyethylene glycol 4000 and chitosan further assisted in sustained release of the drug. Scanning electron microscopy studies revealed that optimized F2EXT3 CR nanophytosomes were nearly spherical with narrow size distribution and smooth surface. The zeta potential of the F2EXT3 showed -3.5 mV. Stability studies revealed that the formulation remained stable even after 6 months. It was observed from the hemin assay that CR and F2EXT3 exhibited (50 μg/mL curcumin) exhibited IC50 values of 47 ± 2.45 and 22 ± 1.58 μM, respectively. Further in vivo antimalarial activity on resistant and sensitive strains needs to be performed to evaluate the efficacy of the developed formulation.

Evolutionary modelling indicates that mosquito metabolism shapes the life-history strategies of Plasmodium parasites

Within-host survival and between-host transmission are key life-history traits of single-celled malaria parasites. Understanding the evolutionary forces that shape these traits is crucial to predict malaria epidemiology, drug resistance, and virulence. However, very little is known about how Plasmodium parasites adapt to their mosquito vectors. Here, we examine the evolution of the time Plasmodium parasites require to develop within the vector (extrinsic incubation period) with an individual-based model of malaria transmission that includes mosquito metabolism. Specifically, we model the metabolic cascade of resource allocation induced by blood-feeding, as well as the influence of multiple blood meals on parasite development. Our model predicts that successful vector-to-human transmission events are rare, and are caused by long-lived mosquitoes. Importantly, our results show that the life-history strategies of malaria parasites depend on the mosquito’s metabolic status. In our model, additional resources provided by multiple blood meals lead to selection for parasites with slow or intermediate developmental time. These results challenge the current assumption that evolution favors fast developing parasites to maximize their chances to complete their within-mosquito life cycle. We propose that the long sporogonic cycle observed for Plasmodium is not a constraint but rather an adaptation to increase transmission potential.

Prevalence of multi drug resistance malaria among patients aged 0 – 14 years attending murtala muhammad specialist hospital Kano State, Nigeria

The Plasmodium falciparum multidrug resistance gene 1 (pfmdr1) is a molecular marker of parasite susceptibility to anti-malarial drugs. This study aimed to evaluate multidrug resistance resistance gene 1 (MDR1) mutation in 0-14years old malaria patients attending Murtala Muhammad Specialist Hospital, Kano, Nigeria. Samples from 100 children with malaria were examined to confirm the malaria parasite density and further genotyped via BigDye (v3.1) terminator cycle sequencing for the presence of two SNPs in pfmdr1on samples with high and moderate parasite densities. All data were analyzed using Pearson Chi square and Fisher’s exact (FE) tests. Of the 100 patients, 57% had low (+) malaria parasite density, 28% had moderate (++) and 15% had high (+++) malaria parasite densities of the 100 samples, 31 samples were successfully amplified and analyzed for the pfmdr1 gene located at codon 86 with amplicon size of 534bp while only 7 samples were successfully amplified for the pfmdr1 gene located at codon 1246.Pfmdr1-N86Y mutation was detected in 1 (3.2%) sample. In addition, only 1 (3.2%) sample with allelic change at 1246Y was detected in mutant pfmdr1gene. The result also showed that sex had no significant association (P = 0.4237) with pfmdr1SNP mutation. However, significant association (P = 0.0043) between the age groups (1 month to 14 years) represented in the study and pfmdr1mutation. The present study suggests that strains of P. falciparum with reduced sensitivity to the artemisinin component of artemisinin-based combination therapy (ACT) exist in Kano state, northern Nigeria. Methods: sample Collection Finger prick filter paper blood samples were collected from patients below the age of 5 years. However, 2 mL of venous blood was drawn using sterile syringe and needle from children aged 6 and 14 years. Safety procedures were adopted in the collection of blood samples by swabbing the area to be sampled with disinfectant and allowing it to dry before collection.

Structure-Activity Relationship Analysis of Novel Compounds Against Drug-Resistant Plasmodium Falciparum Strains

The escalating issue of drug-resistant Plasmodium falciparum strains poses a significant challenge to malaria treatment. This research paper presents a comprehensive analysis of the Structure-Activity Relationship (SAR) of innovative compounds designed to combat drug-resistant malaria. Through systematic examination of the chemical structures and their biological activity, we aim to identify potential drug candidates that can effectively address this global health concern. Our study contributes to the ongoing efforts in antimalarial drug development, offering insights into the design of novel compounds that may prove instrumental in countering drug resistance among Plasmodium falciparum strains and improving the efficacy of malaria treatment strategies. Keywords: Plasmodium falciparum, Antimalarial Compounds, Drug Resistance, Chemical Structure Analysis, Novel Compounds

Evaluation of 4-Aminoquinoline Hydrazone Analogues as Potential Leads for Drug-Resistant Malaria.

The emergence of resistance to first-line antimalarial drugs calls for the development of new therapies for drug-resistant malaria. The efficacy of quinoline-based antimalarial drugs has prompted the development of novel quinolines. A panel of 4-aminoquinoline hydrazone analogues were tested on the multidrug-resistant K1 strain of Plasmodium falciparum: IC50 values after a 48 h cycle ranged from 0.60 to 49 µM, while the 72 h cycle ranged from 0.026 to 0.219 μM. Time-course assays were carried out to define the activity of the lead compounds, which inhibited over 50% growth in 24 h and 90% growth in 72 h. Cytotoxicity assays with HepG2 cells showed IC50 values of 0.87-11.1 μM, whereas in MDBK cells, IC50 values ranged from 1.66 to 11.7 μM. High selectivity indices were observed for the lead compounds screened at 72 h on P. falciparum. Analyses of stage specificity revealed that the ring stages of the parasite life cycle were most affected. Based on antimalarial efficacy and in vitro safety profiles, lead compound 4-(2-benzylidenehydrazinyl)-6-methoxy-2-methylquinoline 2 was progressed to drug combination studies for the detection of synergism, with a combinatory index of 0.599 at IC90 for the combination with artemether, indicating a synergistic antimalarial activity. Compound 2 was screened on different strains of P. falciparum (3D7, Dd2), which maintained similar activity to K1, suggesting no cross-resistance between multidrug resistance and sensitive parasite strains. In vivo analysis with 2 showed the suppression of parasitaemia with P. yoelii NL (non-lethal)-treated mice (20 mg/kg and 5 mg/kg).

Molecular markers associated with drug resistance in Plasmodium falciparum parasites in central Africa between 2016 and 2021.

The widespread occurrence of anti-malarial drug resistance threatens the current efforts to control malaria in African regions. Molecular marker surveillance helps to track the emergence and spread of drug-resistant malaria cases. A total of 237 Plasmodium falciparum infections imported from central Africa to Zhejiang Province, China, between 2016 and 2021, were investigated. Genomic DNA was extracted from blood samples of each patient and nested PCRs was used to detect molecular markers in k13, Pfcrt, and Pfmdr1 genes. The spatial and temporal distributions of the molecular markers were analyzed. A limited polymorphism of k13 was observed, including two nonsynonymous (D464E and K503E) and five synonymous mutations. Wild-type CVMNK of Pfcrt predominated (78.5%), whereas 19.5% of the samples harbored the mutant haplotype, CVIET. The point mutation Y184F and the single mutant haplotype NF of Pfmdr1 were the most frequently observed. The geographical distributions of the Pfcrt and Pfmdr1 haplotypes displayed distinct patterns, with the mutant haplotype of Pfcrt more common in Gabon (53.9%) and Congo (50.0%), and wild haplotypes of Pfmdr1 more frequently found in Cameroon, Angola, and Congo. The prevalence of wild-type CVMNK of Pfcrt increased from 68.5-74.6% in 2016-2017 to 81.8-87.5% in 2018-2021. The proportion of wild-type Pfmdr1 also increased from 27.1% in 2016 to 38.5% in 2019. The geographical and temporal distribution of k13, Pfcrt, and Pfmdr1 polymorphisms in P. falciparum parasites imported from central Africa between 2016 and 2021 are demonstrated. Our data provide updated evidence that can be used to adjust anti-malarial drug policies in central Africa and China.

Malaria vaccines to moderate the impact of antibiotic resistance in endemic countries.

Swift and widespread deployment of an efficient malaria vaccine in Pakistan, together with basic control and preventive measures, could significantly decrease the economic and healthcare burden caused by drug-resistant malaria. Moreover, the RTS,S/AS01 vaccine has provided a much needed breakthrough after decades of growth, as an innovative vaccine for malaria in phase 3 clinical trials and currently undergoing implementation studies. Vaccination is a potentially critical component of efforts to arrest the development and dissemination of antimicrobial resistance, although little is known about the impact vaccination may have within low- and-middle-income countries.

Development of a technique for analyzing the lengths of restriction fragments to assess the mefloquine resistance of plasmodium falciparum based on the identification of single-nucleotide polymorphisms (A958146T, A961013G, G961625T) of the PFMDR1 gene

ABSTRACT. A method for identifying single nucleotide polymorphisms of the PfMDR1 gene (A958146T, A961013G, G961625T) based on the analysis of the lengths of restriction fragments using polymerase chain reaction technology with specific primers is presented. To identify the polymorphism A958146T (amino acid substitution N86Y), it was proposed to amplify a fragment of parasitic deoxyribonucleic acid with a length of 417 bp, including the 86th codon of the PfMDR1 gene, followed by treatment of the amplicon with ApoI endonuclease, the restriction site of which includes the sequence of the analyzed mutation. With the Plasmodium falciparum genotype unchanged, the isolated deoxyribonucleic acid site is divided into two fragments of size 239 and 179 bp. In the case of an altered genotype containing a single nucleotide missense mutation A T, the original fragment 417 bp will be preserved. When designing the system to detect the amino acid substitution N1042D caused by the A961013G mutation, a pair of specific primers were selected that limit the 404 bp-long section of parasitic deoxyribonucleic acid. For restriction analysis, the most optimal was the use of AseI endonuclease, which in the case of an unchanged Plasmodium falciparum genotype divides the initial amplicon into 4 fragments (132, 116, 99 and 25 bp), and in the presence of A G mutation into 3 (248, 99, 25 bp). It was found that a fragment of the PfMDR1 gene, including the G961625T mutation leading to the amino acid substitution D1246Y, contains 1 site corresponding to the restriction site of endonuclease BglII. Therefore, in the case of the wild genotype of Plasmodium falciparum, the initial fragment of deoxyribonucleic acid is cut into 2 short sections (300 and 269 bp). With the D1246 mutation, the replacement of the nucleotide G T leads to the disappearance of the restriction site, so only one source fragment (509 bp) will be recorded on the electrophoregram. Based on the analysis of the data obtained, criteria for evaluating the drug resistance of Plasmodium falciparum have been developed. The decrease in sensitivity to mefloquine and its derivatives of pathogens of tropical malaria can be evidenced by positive results obtained using the developed methods for detecting haplotypes A T (N86Y (band 417 bp)), A G (N1042D (bands 248, 99 and 25 bp)), G T (D1246Y (509 bp)). The developed methods can be used to analyze the spread of drug-resistant tropical malaria.