SnapShot: Antimalarial Drugs.

Malaria is a prominent vector-borne illness caused by Plasmodium parasites. Therapeutic intervention remains a critical component for disease eradication efforts but is complicated by the emergence of drug resistance. This SnapShot summarizes the human-relevant stages of the P. falciparum life cycle and describes how licensed antimalarials, clinical candidates, and newly emerging compounds target each stage to prevent, treat, or block transmission of malaria. To view this SnapShot, open or download the PDF.

Transcriptome dynamics of CD4+ T cells during malaria maps gradual transit from effector to memory.

The dynamics of CD4+ T cell memory development remain to be examined at genome scale. In malaria-endemic regions, antimalarial chemoprevention protects long after its cessation and associates with effects on CD4+ T cells. We applied single-cell RNA sequencing and computational modelling to track memory development during Plasmodium infection and treatment. In the absence of central memory precursors, two trajectories developed as T helper 1 (TH1) and follicular helper T (TFH) transcriptomes contracted and partially coalesced over three weeks. Progeny of single clones populated TH1 and TFH trajectories, and fate-mapping suggested that there was minimal lineage plasticity. Relationships between TFH and central memory were revealed, with antimalarials modulating these responses and boosting TH1 recall. Finally, single-cell epigenomics confirmed that heterogeneity among effectors was partially reset in memory. Thus, the effector-to-memory transition in CD4+ T cells is gradual during malaria and is modulated by antiparasitic drugs. Graphical user interfaces are presented for examining gene-expression dynamics and gene-gene correlations ( http://haquelab.mdhs.unimelb.edu.au/cd4_memory/ ).

Supergenomic network compression and the discovery of EXP1 as a glutathione transferase inhibited by artesunate.

A central problem in biology is to identify gene function. One approach is to infer function in large supergenomic networks of interactions and ancestral relationships among genes; however, their analysis can be computationally prohibitive. We show here that these biological networks are compressible. They can be shrunk dramatically by eliminating redundant evolutionary relationships, and this process is efficient because in these networks the number of compressible elements rises linearly rather than exponentially as in other complex networks. Compression enables global network analysis to computationally harness hundreds of interconnected genomes and to produce functional predictions. As a demonstration, we show that the essential, but functionally uncharacterized Plasmodium falciparum antigen EXP1 is a membrane glutathione S-transferase. EXP1 efficiently degrades cytotoxic hematin, is potently inhibited by artesunate, and is associated with artesunate metabolism and susceptibility in drug-pressured malaria parasites. These data implicate EXP1 in the mode of action of a frontline antimalarial drug.

Targeting Aminoacyl tRNA Synthetases for Antimalarial Drug Development.

Infections caused by malaria parasites place an enormous burden on the world's poorest communities. Breakthrough drugs with novel mechanisms of action are urgently needed. As an organism that undergoes rapid growth and division, the malaria parasite Plasmodium falciparum is highly reliant on protein synthesis, which in turn requires aminoacyl-tRNA synthetases (aaRSs) to charge tRNAs with their corresponding amino acid. Protein translation is required at all stages of the parasite life cycle; thus, aaRS inhibitors have the potential for whole-of-life-cycle antimalarial activity. This review focuses on efforts to identify potent plasmodium-specific aaRS inhibitors using phenotypic screening, target validation, and structure-guided drug design. Recent work reveals that aaRSs are susceptible targets for a class of AMP-mimicking nucleoside sulfamates that target the enzymes via a novel reaction hijacking mechanism. This finding opens up the possibility of generating bespoke inhibitors of different aaRSs, providing new drug leads.

Advances and opportunities in malaria population genomics.

Almost 20 years have passed since the first reference genome assemblies were published for Plasmodium falciparum, the deadliest malaria parasite, and Anopheles gambiae, the most important mosquito vector of malaria in sub-Saharan Africa. Reference genomes now exist for all human malaria parasites and nearly half of the ~40 important vectors around the world. As a foundation for genetic diversity studies, these reference genomes have helped advance our understanding of basic disease biology and drug and insecticide resistance, and have informed vaccine development efforts. Population genomic data are increasingly being used to guide our understanding of malaria epidemiology, for example by assessing connectivity between populations and the efficacy of parasite and vector interventions. The potential value of these applications to malaria control strategies, together with the increasing diversity of genomic data types and contexts in which data are being generated, raise both opportunities and challenges in the field. This Review discusses advances in malaria genomics and explores how population genomic data could be harnessed to further support global disease control efforts.

Targeting the Plasmodium falciparum UCHL3 ubiquitin hydrolase using chemically constrained peptides.

The ubiquitin-proteasome system is essential to all eukaryotes and has been shown to be critical to parasite survival as well, including Plasmodium falciparum, the causative agent of the deadliest form of malarial disease. Despite the central role of the ubiquitin-proteasome pathway to parasite viability across its entire life-cycle, specific inhibitors targeting the individual enzymes mediating ubiquitin attachment and removal do not currently exist. The ability to disrupt P. falciparum growth at multiple developmental stages is particularly attractive as this could potentially prevent both disease pathology, caused by asexually dividing parasites, as well as transmission which is mediated by sexually differentiated parasites. The deubiquitinating enzyme PfUCHL3 is an essential protein, transcribed across both human and mosquito developmental stages. PfUCHL3 is considered hard to drug by conventional methods given the high level of homology of its active site to human UCHL3 as well as to other UCH domain enzymes. Here, we apply the RaPID mRNA display technology and identify constrained peptides capable of binding to PfUCHL3 with nanomolar affinities. The two lead peptides were found to selectively inhibit the deubiquitinase activity of PfUCHL3 versus HsUCHL3. NMR spectroscopy revealed that the peptides do not act by binding to the active site but instead block binding of the ubiquitin substrate. We demonstrate that this approach can be used to target essential protein-protein interactions within the Plasmodium ubiquitin pathway, enabling the application of chemically constrained peptides as a novel class of antimalarial therapeutics.

Increasing Prevalence of Artemisinin-Resistant HRP2-Negative Malaria in Eritrea.

BACKGROUND: Although the clinical efficacy of antimalarial artemisinin-based combination therapies in Africa remains high, the recent emergence of partial resistance to artemisinin in Plasmodium falciparum on the continent is troubling, given the lack of alternative treatments. METHODS: In this study, we used data from drug-efficacy studies conducted between 2016 and 2019 that evaluated 3-day courses of artemisinin-based combination therapy (artesunate-amodiaquine or artemether-lumefantrine) for uncomplicated malaria in Eritrea to estimate the percentage of patients with day-3 positivity (i.e., persistent P. falciparum parasitemia 3 days after the initiation of therapy). We also assayed parasites for mutations in Pfkelch13 as predictive markers of partial resistance to artemisinin and screened for deletions in hrp2 and hrp3 that result in variable performance of histidine rich protein 2 (HRP2)-based rapid diagnostic tests for malaria. RESULTS: We noted an increase in the percentage of patients with day-3 positivity from 0.4% (1 of 273) in 2016 to 1.9% (4 of 209) in 2017 and 4.2% (15 of 359) in 2019. An increase was also noted in the prevalence of the Pfkelch13 R622I mutation, which was detected in 109 of 818 isolates before treatment, from 8.6% (24 of 278) in 2016 to 21.0% (69 of 329) in 2019. The odds of day-3 positivity increased by a factor of 6.2 (95% confidence interval, 2.5 to 15.5) among the patients with Pfkelch13 622I variant parasites. Partial resistance to artemisinin, as defined by the World Health Organization, was observed in Eritrea. More than 5% of the patients younger than 15 years of age with day-3 positivity also had parasites that carried Pfkelch13 R622I. In vitro, the R622I mutation conferred a low level of resistance to artemisinin when edited into NF54 and Dd2 parasite lines. Deletions in both hrp2 and hrp3 were identified in 16.9% of the parasites that carried the Pfkelch13 R622I mutation, which made them potentially undetectable by HRP2-based rapid diagnostic tests. CONCLUSIONS: The emergence and spread of P. falciparum lineages with both Pfkelch13-mediated partial resistance to artemisinin and deletions in hrp2 and hrp3 in Eritrea threaten to compromise regional malaria control and elimination campaigns. (Funded by the Bill and Melinda Gates Foundation and others; Australian New Zealand Clinical Trials Registry numbers, ACTRN12618001223224, ACTRN12618000353291, and ACTRN12619000859189.).

Role of riboflavin deficiency in malaria pathophysiology.

The emergence of resistance against antimalarials and insecticides poses a significant threat to malaria elimination strategies. It is crucial to explore potential risk factors for malaria to identify new targets and alternative therapies. Malnutrition is a well-established risk factor for malaria. Deficiencies of micronutrients such as vitamin A, zinc, iron, folic acid, and phenotypic measures of malnutrition, such as stunting and wasting, have been studied extensively in the context of malaria. Vitamin B2, also known as riboflavin, is a micronutrient involved in maintaining cellular homeostasis. Riboflavin deficiency has been shown to have an inverse correlation with malarial parasitaemia. This article reviews the role of riboflavin in maintaining redox homeostasis and probes how riboflavin deficiency could alter malaria pathogenesis by disrupting the balance between oxidants and antioxidants. Though riboflavin analogues have been explored as antimalarials, new in vivo and patient-based research is required to target riboflavin-associated pathways for antimalarial therapy.

Temporal and spatial dynamics of Plasmodium falciparum clonal lineages in Guyana.

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.

Single cell RNA sequencing reveals endothelial cell killing and resolution pathways in experimental malaria-associated acute respiratory distress syndrome.

Plasmodium parasites cause malaria, a global health disease that is responsible for more than 200 million clinical cases and 600 000 deaths each year. Most deaths are caused by various complications, including malaria-associated acute respiratory distress syndrome (MA-ARDS). Despite the very rapid and efficient killing of parasites with antimalarial drugs, 15% of patients with complicated malaria succumb. This stresses the importance of investigating resolution mechanisms that are involved in the recovery from these complications once the parasite is killed. To study the resolution of MA-ARDS, P. berghei NK65-infected C57BL/6 mice were treated with antimalarial drugs after onset of symptoms, resulting in 80% survival. Micro-computed tomography revealed alterations of the lungs upon infection, with an increase in total and non-aerated lung volume due to edema. Whole body plethysmography confirmed a drastically altered lung ventilation, which was restored during resolution. Single-cell RNA sequencing indicated an increased inflammatory state in the lungs upon infection, which was accompanied by a drastic decrease in endothelial cells, consistent with CD8+ T cell-mediated killing. During resolution, anti-inflammatory pathways were upregulated and proliferation of endothelial cells was observed. MultiNicheNet interactome analysis identified important changes in the ligand-receptor interactions during disease resolution that warrant further exploration in order to develop new therapeutic strategies. In conclusion, our study provides insights in pro-resolving pathways that limit inflammation and promote endothelial cell proliferation in experimental MA-ARDS. This information may be useful for the design of adjunctive treatments to enhance resolution after Plasmodium parasite killing by antimalarial drugs.

Sulfonylpiperazine compounds prevent Plasmodium falciparum invasion of red blood cells through interference with actin-1/profilin dynamics.

With emerging resistance to frontline treatments, it is vital that new antimalarial drugs are identified to target Plasmodium falciparum. We have recently described a compound, MMV020291, as a specific inhibitor of red blood cell (RBC) invasion, and have generated analogues with improved potency. Here, we generated resistance to MMV020291 and performed whole genome sequencing of 3 MMV020291-resistant populations. This revealed 3 nonsynonymous single nucleotide polymorphisms in 2 genes; 2 in profilin (N154Y, K124N) and a third one in actin-1 (M356L). Using CRISPR-Cas9, we engineered these mutations into wild-type parasites, which rendered them resistant to MMV020291. We demonstrate that MMV020291 reduces actin polymerisation that is required by the merozoite stage parasites to invade RBCs. Additionally, the series inhibits the actin-1-dependent process of apicoplast segregation, leading to a delayed death phenotype. In vitro cosedimentation experiments using recombinant P. falciparum proteins indicate that potent MMV020291 analogues disrupt the formation of filamentous actin in the presence of profilin. Altogether, this study identifies the first compound series interfering with the actin-1/profilin interaction in P. falciparum and paves the way for future antimalarial development against the highly dynamic process of actin polymerisation.

The role of Plasmodium V-ATPase in vacuolar physiology and antimalarial drug uptake.

To ensure their survival in the human bloodstream, malaria parasites degrade up to 80% of the host erythrocyte hemoglobin in an acidified digestive vacuole. Here, we combine conditional reverse genetics and quantitative imaging approaches to demonstrate that the human malaria pathogen Plasmodium falciparum employs a heteromultimeric V-ATPase complex to acidify the digestive vacuole matrix, which is essential for intravacuolar hemoglobin release, heme detoxification, and parasite survival. We reveal an additional function of the membrane-embedded V-ATPase subunits in regulating morphogenesis of the digestive vacuole independent of proton translocation. We further show that intravacuolar accumulation of antimalarial chemotherapeutics is surprisingly resilient to severe deacidification of the vacuole and that modulation of V-ATPase activity does not affect parasite sensitivity toward these drugs.

Autocatalytic activation of a malarial egress protease is druggable and requires a protein cofactor.

Malaria parasite egress from host erythrocytes (RBCs) is regulated by discharge of a parasite serine protease called SUB1 into the parasitophorous vacuole (PV). There, SUB1 activates a PV-resident cysteine protease called SERA6, enabling host RBC rupture through SERA6-mediated degradation of the RBC cytoskeleton protein ß-spectrin. Here, we show that the activation of Plasmodium falciparum SERA6 involves a second, autocatalytic step that is triggered by SUB1 cleavage. Unexpectedly, autoproteolytic maturation of SERA6 requires interaction in multimolecular complexes with a distinct PV-located protein cofactor, MSA180, that is itself a SUB1 substrate. Genetic ablation of MSA180 mimics SERA6 disruption, producing a fatal block in ß-spectrin cleavage and RBC rupture. Drug-like inhibitors of SERA6 autoprocessing similarly prevent ß-spectrin cleavage and egress in both P. falciparum and the emerging zoonotic pathogen P. knowlesi. Our results elucidate the egress pathway and identify SERA6 as a target for a new class of antimalarial drugs designed to prevent disease progression.

Machine learning-based phenotypic imaging to characterise the targetable biology of Plasmodium falciparum male gametocytes for the development of transmission-blocking antimalarials.

Preventing parasite transmission from humans to mosquitoes is recognised to be critical for achieving elimination and eradication of malaria. Consequently developing new antimalarial drugs with transmission-blocking properties is a priority. Large screening campaigns have identified many new transmission-blocking molecules, however little is known about how they target the mosquito-transmissible Plasmodium falciparum stage V gametocytes, or how they affect their underlying cell biology. To respond to this knowledge gap, we have developed a machine learning image analysis pipeline to characterise and compare the cellular phenotypes generated by transmission-blocking molecules during male gametogenesis. Using this approach, we studied 40 molecules, categorising their activity based upon timing of action and visual effects on the organisation of tubulin and DNA within the cell. Our data both proposes new modes of action and corroborates existing modes of action of identified transmission-blocking molecules. Furthermore, the characterised molecules provide a new armoury of tool compounds to probe gametocyte cell biology and the generated imaging dataset provides a new reference for researchers to correlate molecular target or gene deletion to specific cellular phenotype. Our analysis pipeline is not optimised for a specific organism and could be applied to any fluorescence microscopy dataset containing cells delineated by bounding boxes, and so is potentially extendible to any disease model.

The Kelch13 compartment contains highly divergent vesicle trafficking proteins in malaria parasites.

Single amino acid changes in the parasite protein Kelch13 (K13) result in reduced susceptibility of P. falciparum parasites to artemisinin and its derivatives (ART). Recent work indicated that K13 and other proteins co-localising with K13 (K13 compartment proteins) are involved in the endocytic uptake of host cell cytosol (HCCU) and that a reduction in HCCU results in reduced susceptibility to ART. HCCU is critical for parasite survival but is poorly understood, with the K13 compartment proteins among the few proteins so far functionally linked to this process. Here we further defined the composition of the K13 compartment by analysing more hits from a previous BioID, showing that MyoF and MCA2 as well as Kelch13 interaction candidate (KIC) 11 and 12 are found at this site. Functional analyses, tests for ART susceptibility as well as comparisons of structural similarities using AlphaFold2 predictions of these and previously identified proteins showed that vesicle trafficking and endocytosis domains were frequent in proteins involved in resistance or endocytosis (or both), comprising one group of K13 compartment proteins. While this strengthened the link of the K13 compartment to endocytosis, many proteins of this group showed unusual domain combinations and large parasite-specific regions, indicating a high level of taxon-specific adaptation of this process. Another group of K13 compartment proteins did not influence endocytosis or ART susceptibility and lacked detectable vesicle trafficking domains. We here identified the first protein of this group that is important for asexual blood stage development and showed that it likely is involved in invasion. Overall, this work identified novel proteins functioning in endocytosis and at the K13 compartment. Together with comparisons of structural predictions it provides a repertoire of functional domains at the K13 compartment that indicate a high level of adaption of endocytosis in malaria parasites.

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.

Molecular Mechanisms of Drug Resistance in Plasmodium falciparum Malaria.

Understanding and controlling the spread of antimalarial resistance, particularly to artemisinin and its partner drugs, is a top priority. Plasmodium falciparum parasites resistant to chloroquine, amodiaquine, or piperaquine harbor mutations in the P. falciparum chloroquine resistance transporter (PfCRT), a transporter resident on the digestive vacuole membrane that in its variant forms can transport these weak-base 4-aminoquinoline drugs out of this acidic organelle, thus preventing these drugs from binding heme and inhibiting its detoxification. The structure of PfCRT, solved by cryogenic electron microscopy, shows mutations surrounding an electronegative central drug-binding cavity where they presumably interact with drugs and natural substrates to control transport. P. falciparum susceptibility to heme-binding antimalarials is also modulated by overexpression or mutations in the digestive vacuole membrane-bound ABC transporter PfMDR1 (P. falciparum multidrug resistance 1 transporter). Artemisinin resistance is primarily mediated by mutations in P. falciparum Kelch13 protein (K13), a protein involved in multiple intracellular processes including endocytosis of hemoglobin, which is required for parasite growth and artemisinin activation. Combating drug-resistant malaria urgently requires the development of new antimalarial drugs with novel modes of action.

Mechanistic basis for multidrug resistance and collateral drug sensitivity conferred to the malaria parasite by polymorphisms in PfMDR1 and PfCRT.

Polymorphisms in the Plasmodium falciparum multidrug resistance protein 1 (pfmdr1) gene and the Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene alter the malaria parasite's susceptibility to most of the current antimalarial drugs. However, the precise mechanisms by which PfMDR1 contributes to multidrug resistance have not yet been fully elucidated, nor is it understood why polymorphisms in pfmdr1 and pfcrt that cause chloroquine resistance simultaneously increase the parasite's susceptibility to lumefantrine and mefloquine-a phenomenon known as collateral drug sensitivity. Here, we present a robust expression system for PfMDR1 in Xenopus oocytes that enables direct and high-resolution biochemical characterizations of the protein. We show that wild-type PfMDR1 transports diverse pharmacons, including lumefantrine, mefloquine, dihydroartemisinin, piperaquine, amodiaquine, methylene blue, and chloroquine (but not the antiviral drug amantadine). Field-derived mutant isoforms of PfMDR1 differ from the wild-type protein, and each other, in their capacities to transport these drugs, indicating that PfMDR1-induced changes in the distribution of drugs between the parasite's digestive vacuole (DV) and the cytosol are a key driver of both antimalarial resistance and the variability between multidrug resistance phenotypes. Of note, the PfMDR1 isoforms prevalent in chloroquine-resistant isolates exhibit reduced capacities for chloroquine, lumefantrine, and mefloquine transport. We observe the opposite relationship between chloroquine resistance-conferring mutations in PfCRT and drug transport activity. Using our established assays for characterizing PfCRT in the Xenopus oocyte system and in live parasite assays, we demonstrate that these PfCRT isoforms transport all 3 drugs, whereas wild-type PfCRT does not. We present a mechanistic model for collateral drug sensitivity in which mutant isoforms of PfMDR1 and PfCRT cause chloroquine, lumefantrine, and mefloquine to remain in the cytosol instead of sequestering within the DV. This change in drug distribution increases the access of lumefantrine and mefloquine to their primary targets (thought to be located outside of the DV), while simultaneously decreasing chloroquine's access to its target within the DV. The mechanistic insights presented here provide a basis for developing approaches that extend the useful life span of antimalarials by exploiting the opposing selection forces they exert upon PfCRT and PfMDR1.

Spatio-temporal spread of artemisinin resistance in Southeast Asia.

Current malaria elimination targets must withstand a colossal challenge-resistance to the current gold standard antimalarial drug, namely artemisinin derivatives. If artemisinin resistance significantly expands to Africa or India, cases and malaria-related deaths are set to increase substantially. Spatial information on the changing levels of artemisinin resistance in Southeast Asia is therefore critical for health organisations to prioritise malaria control measures, but available data on artemisinin resistance are sparse. We use a comprehensive database from the WorldWide Antimalarial Resistance Network on the prevalence of non-synonymous mutations in the Kelch 13 (K13) gene, which are known to be associated with artemisinin resistance, and a Bayesian geostatistical model to produce spatio-temporal predictions of artemisinin resistance. Our maps of estimated prevalence show an expansion of the K13 mutation across the Greater Mekong Subregion from 2000 to 2022. Moreover, the period between 2010 and 2015 demonstrated the most spatial change across the region. Our model and maps provide important insights into the spatial and temporal trends of artemisinin resistance in a way that is not possible using data alone, thereby enabling improved spatial decision support systems on an unprecedented fine-scale spatial resolution. By predicting for the first time spatio-temporal patterns and extents of artemisinin resistance at the subcontinent level, this study provides critical information for supporting malaria elimination goals in Southeast Asia.

Exposing Anopheles mosquitoes to antimalarials blocks Plasmodium parasite transmission.

Bites of Anopheles mosquitoes transmit Plasmodium falciparum parasites that cause malaria, which kills hundreds of thousands of people every year. Since the turn of this century, efforts to prevent the transmission of these parasites via the mass distribution of insecticide-treated bed nets have been extremely successful, and have led to an unprecedented reduction in deaths from malaria1. However, resistance to insecticides has become widespread in Anopheles populations2-4, which has led to the threat of a global resurgence of malaria and makes the generation of effective tools for controlling this disease an urgent public health priority. Here we show that the development of P. falciparum can be rapidly and completely blocked when female Anopheles gambiae mosquitoes take up low concentrations of specific antimalarials from treated surfaces-conditions that simulate contact with a bed net. Mosquito exposure to atovaquone before, or shortly after, P. falciparum infection causes full parasite arrest in the midgut, and prevents transmission of infection. Similar transmission-blocking effects are achieved using other cytochrome b inhibitors, which demonstrates that parasite mitochondrial function is a suitable target for killing parasites. Incorporating these effects into a model of malaria transmission dynamics predicts that impregnating mosquito nets with Plasmodium inhibitors would substantially mitigate the global health effects of insecticide resistance. This study identifies a powerful strategy for blocking Plasmodium transmission by female Anopheles mosquitoes, which has promising implications for efforts to eradicate malaria.