Streamlined and robust stage-specific profiling of gametocytocidal compounds against Plasmodium falciparum

Malaria elimination is dependent on the ability to target both the pathogenic and transmissible stages of the human malaria parasite, Plasmodium falciparum. These forms of the parasite are differentiated by unique developmental stages, each with their own biological mechanisms and processes. These individual stages therefore also respond differently to inhibitory compounds, and this complicates the discovery of multistage active antimalarial agents. The search for compounds with transmission-blocking activity has focused on screening for activity on mature gametocytes, with only limited descriptions available for the activity of such compounds on immature stage gametocytes. This therefore poses a gap in the profiling of antimalarial agents for pan-reactive, multistage activity to antimalarial leads. Here, we optimized an effective and robust strategy for the simple and cost-effective description of the stage-specific action of gametocytocidal antimalarial compounds.The South African Medical Research Council Strategic Health Innovation Partnership and the Department of Science and Innovation South African Research Chairs Initiative, administered through the South African National Research Foundation; a BMGF Grand Challenges Africa grant; the Medicines for Malaria Venture as Global Test center for stage-specific gametocytocidal assays.http://www.frontiersin.org/Cellular_and_Infection_Microbiologyhj2022BiochemistryGeneticsMicrobiology and Plant PathologyUP Centre for Sustainable Malaria Control (UP CSMC

Adapt or die : targeting unique transmission-stage biology for malaria elimination

Plasmodium parasites have a complex life cycle that includes development in the human host as well as the Anopheles vector. Successful transmission of the parasite between its host and vector therefore requires the parasite to balance its investments in asexual replication and sexual reproduction, varying the frequency of sexual commitment to persist within the human host and generate future opportunities for transmission. The transmission window is extended further by the ability of stage V gametocytes to circulate in peripheral blood for weeks, whereas immature stage I to IV gametocytes sequester in the bone marrow and spleen until final maturation. Due to the low gametocyte numbers in blood circulation and with the ease of targeting such life cycle bottlenecks, transmission represents an efficient target for therapeutic intervention. The biological process of Plasmodium transmission is a multistage, multifaceted process and the past decade has seen a much deeper understanding of the molecular mechanisms and regulators involved. Clearly, specific and divergent processes are used during transmission compared to asexual proliferation, which both poses challenges but also opportunities for discovery of transmission-blocking antimalarials. This review therefore presents an update of our molecular understanding of gametocyte and gamete biology as well as the status of transmission-blocking activities of current antimalarials and lead development compounds. By defining the biological components associated with transmission, considerations for the development of new transmission-blocking drugs to target such untapped but unique biology is suggested as an important, main driver for transmissionblocking drug discovery.https://www.frontiersin.org/journals/cellular-and-infection-microbiologydm2022BiochemistryGeneticsMicrobiology and Plant PathologySchool of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC

The ecdysone receptor regulates several key physiological factors in Anopheles funestus

BACKGROUND : Malaria is a devastating disease, transmitted by female Anopheles mosquitoes infected with Plasmodium parasites. Current insecticide-based strategies exist to control the spread of malaria by targeting vectors. However, the increase in insecticide resistance in vector populations hinder the efficacy of these methods. It is, therefore, essential to develop novel vector control methods that efficiently target transmission reducing factors such as vector density and competence. A possible vector control candidate gene, the ecdysone receptor, regulates longevity, reproduction, immunity and other physiological processes in several insects, including malaria vectors. Anopheles funestus is a prominent vector in sub-Saharan Africa, however, the function of the ecdysone receptor in this mosquito has not previously been studied. This study aimed to determine if the ecdysone receptor depletion impacts An. funestus longevity, reproduction and susceptibility to Plasmodium falciparum infection. METHODS : RNA interference was used to reduce ecdysone receptor expression levels in An. funestus females and investigate how the above-mentioned phenotypes are influenced. Additionally, the expression levels of the ecdysone receptor, and reproduction genes lipophorin and vitellogenin receptor as well as the immune gene, leucine rich immune molecule 9 were determined in ecdysone receptor-depleted mosquitoes using quantitative polymerase chain reaction. RESULTS : Ecdysone receptor-depleted mosquitoes had a shorter lifespan, impaired oogenesis, were less fertile, and had reduced P. falciparum infection intensity. CONCLUSIONS : Overall, this study provides the first experimental evidence that supports ecdysone receptor as a potential target in the development of vector control measures targeting An. funestus.Additional file 1: Figure S1. Relative EcR expression levels in dsEcR injected An. funestus females compared to dsGFP injected An. funestus females. The EcR gene was knocked down in dsEcR injected An. funestus females as EcR expression levels were drastically reduced compared to the GFP control. Statistically significant knockdown was evident in dsEcR injected An. funestus females 24, 48 and 72 h after injection as EcR expression in dsEcR injected An. funestus females was 0.11 ± 0.006 (p < 0.05), 0.01 ± 0.001 (p < 0.01) and 0.2 ± 0.06 (p < 0.05) respectively when compared to the GFP injected control of 1. This data confirmed EcR knockdown in An. funestus females injected with dsEcR. Data is representative of 2 biological replicates and normalised using an average of RPS7 and RPL19 reference genes. Expression levels calculated using relative quantification method (∆∆Ct). At each time point statistical significance was assessed with the unpaired student’s t-test. *p < 0.05, **p < 0.01. Error bars represent standard deviation.Additional file 2: Figure S2. The highest mating success rate was achieved when An. funestus males and females are combined for 12 days after which no further increases are observed. The percentage mating success rate increased progressively until it reached its highest value of 62.2% after 12 days of mating. After this point, the mating success rate reached a plateau until day 20. Statistical significance was calculated using one-way ANOVA with Tukey’s post hoc analysis to correct for multiple comparison. Data represents the means of 3 biological replicates. Error bars represent standard deviation of means. ns = not statistically significant p > 0.05; ** = p < 0.01; *** = p < 0.001; **** = p < 0.0001. (n) = number of females per time point across 3 biological replicates.Additional file 3: Figure S3. Blood feeding rates did not differ between treatment groups. Insignificant differences amongst treatment groups confirmed that the blood feeding rates did not influence any changes observed in the phenotypes of dsEcR treated An. funestus females (p > 0.05). Statistical significance calculated using an unpaired student’s t-test. Error bars represent standard deviation. ns = not statistically significant p > 0.05.Additional file 4: Table S1. Statistical significance between dsGFP and uninjected controls from the various biological assays conducted.The Department of Science and Innovation (DSI); the National Research Foundation (NRF) South African Research Chairs Initiative; the NRF Communities of Practice and the South African Medical Research Council Strategic Health Innovation Partnerships (SHIP) with funds from DSI.https://malariajournal.biomedcentral.comhj2022BiochemistryGeneticsMicrobiology and Plant PathologyUP Centre for Sustainable Malaria Control (UP CSMC

A dynamic and combinatorial histone code drives malaria parasite asexual and sexual development

Histone posttranslational modifications (PTMs) frequently co-occur on the same chromatin domains or even in the same molecule. It is now established that these “histone codes” are the result of cross talk between enzymes that catalyze multiple PTMs with univocal readout as compared with these PTMs in isolation. Here, we performed a comprehensive identification and quantification of histone codes of the malaria parasite, Plasmodium falciparum. We used advanced quantitative middle-down proteomics to identify combinations of PTMs in both the proliferative, asexual stages and transmissible, sexual gametocyte stages of P. falciparum. We provide an updated, high-resolution compendium of 77 PTMs on H3 and H3.3, of which 34 are newly identified in P. falciparum. Coexisting PTMs with unique stage distinctions were identified, indicating that many of these combinatorial PTMs are associated with specific stages of the parasite life cycle. We focused on the code H3R17me2K18acK23ac for its unique presence in mature gametocytes; chromatin proteomics identified a gametocyte-specific SAGA-like effector complex including the transcription factor AP2-G2, which we tied to this specific histone code, as involved in regulating gene expression in mature gametocytes. Ultimately, this study unveils previously undiscovered histone PTMs and their functional relationship with coexisting partners. These results highlight that investigating chromatin regulation in the parasite using single histone PTM assays might overlook higher-order gene regulation for distinct proliferation and differentiation processes.The South African Research Chairs Initiative of the Department of Science and Innovation, administered through the South African National Research Foundation; the Leukemia Research Foundation; AFAR; Deerfield and the National Institutes of Health.https://www.asbmb.org/journals-news/molecular-cellular-proteomicshj2022BiochemistryGeneticsMicrobiology and Plant PathologyUP Centre for Sustainable Malaria Control (UP CSMC

In vitro dual activity of Aloe marlothii roots and its chemical constituents against Plasmodium falciparum asexual and sexual stage parasites

Please abstract in the article.The Department of Science and Innovation (DSI) of South Africa; the South African Research Chairs Initiative of the DSI, administered through the South African National Research Foundation; the South African Medical Research Council; the University of Pretoria Postgraduate Research Support Bursary, South Africa and the L’Oréal-UNESCO for Woman in Science grant.https://www.elsevier.com/locate/jethpharm2023-07-19hj2023BiochemistryChemistryGeneticsMicrobiology and Plant PathologySchool of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC

Adsorption to the surface of hemozoin crystals: structure-based design and synthesis of amino-phenoxazine beta-hematin inhibitors

Please read abstract in the article.Department of Chemistry and Polymer Science, Stellenbosch University; National Institute of Allergy and Infectious Diseases of the National Institutes of Health (NIH); National Research Foundation (NRF) of South Africa.https://onlinelibrary.wiley.com/journal/18607187hj2022BiochemistryGeneticsMicrobiology and Plant PathologyUP Centre for Sustainable Malaria Control (UP CSMC

The Artemiside-Artemisox-Artemisone-M1 Tetrad: Efficacies against Blood Stage P. falciparum Parasites, DMPK Properties, and the Case for Artemiside

Because of the need to replace the current clinical artemisinins in artemisinin combination therapies, we are evaluating fitness of amino-artemisinins for this purpose. These include the thiomorpholine derivative artemiside obtained in one scalable synthetic step from dihydroartemisinin (DHA) and the derived sulfone artemisone. We have recently shown that artemiside undergoes facile metabolism via the sulfoxide artemisox into artemisone and thence into the unsaturated metabolite M1; DHA is not a metabolite. Artemisox and M1 are now found to be approximately equipotent with artemiside and artemisone in vitro against asexual P. falciparum (Pf) blood stage parasites (IC50 1.5–2.6 nM). Against Pf NF54 blood stage gametocytes, artemisox is potently active (IC50 18.9 nM early-stage, 2.7 nM late-stage), although against the late-stage gametocytes, activity is expressed, like other amino-artemisinins, at a prolonged incubation time of 72 h. Comparative drug metabolism and pharmacokinetic (DMPK) properties were assessed via po and iv administration of artemiside, artemisox, and artemisone in a murine model. Following oral administration, the composite Cmax value of artemiside plus its metabolites artemisox and artemisone formed in vivo is some 2.6-fold higher than that attained following administration of artemisone alone. Given that efficacy of short half-life rapidly-acting antimalarial drugs such as the artemisinins is associated with Cmax, it is apparent that artemiside will be more active than artemisone in vivo, due to additive effects of the metabolites. As is evident from earlier data, artemiside indeed possesses appreciably greater efficacy in vivo against murine malaria. Overall, the higher exposure levels of active drug following administration of artemiside coupled with its synthetic accessibility indicate it is much the preferred drug for incorporation into rational new artemisinin combination therapies

The artemiside-artemisox-artemisone-m1 tetrad : efficacies against blood stage p. falciparum parasites, dmpk properties, and the case for artemiside

Because of the need to replace the current clinical artemisinins in artemisinin combination therapies, we are evaluating fitness of amino-artemisinins for this purpose. These include the thiomorpholine derivative artemiside obtained in one scalable synthetic step from dihydroartemisinin (DHA) and the derived sulfone artemisone. We have recently shown that artemiside undergoes facile metabolism via the sulfoxide artemisox into artemisone and thence into the unsaturated metabolite M1; DHA is not a metabolite. Artemisox and M1 are now found to be approximately equipotent with artemiside and artemisone in vitro against asexual P. falciparum (Pf ) blood stage parasites (IC50 1.5–2.6 nM). Against Pf NF54 blood stage gametocytes, artemisox is potently active (IC50 18.9 nM early-stage, 2.7 nM late-stage), although against the late-stage gametocytes, activity is expressed, like other amino-artemisinins, at a prolonged incubation time of 72 h. Comparative drug metabolism and pharmacokinetic (DMPK) properties were assessed via po and iv administration of artemiside, artemisox, and artemisone in a murine model. Following oral administration, the composite Cmax value of artemiside plus its metabolites artemisox and artemisone formed in vivo is some 2.6-fold higher than that attained following administration of artemisone alone. Given that efficacy of short half-life rapidly-acting antimalarial drugs such as the artemisinins is associated with Cmax, it is apparent that artemiside will be more active than artemisone in vivo, due to additive effects of the metabolites. As is evident from earlier data, artemiside indeed possesses appreciably greater efficacy in vivo against murine malaria. Overall, the higher exposure levels of active drug following administration of artemiside coupled with its synthetic accessibility indicate it is much the preferred drug for incorporation into rational new artemisinin combination therapies.Supplementary Material 1: S1 Efficacy of artemisox, dose response curves against asexual, and gametocyte blood stage parasites: Figure S1a–e; S2 Efficacy of M1, dose response curves against asexual, and gametocyte blood stage parasites: Figure S2a–d; S3 Pharmacokinetics and metabolism, circulating concentrations of artemiside, artemisox, and artemisone: Table S3a–f, LC-MS/MS chromatograms of M1 Figure S3a–c; S4 In vitro efficacy data— previously published data for artemiside, artemisone, M1: Table S4a–c; S5 In vivo efficacy data— previously published data for artemiside, artemisone: Table S5; S6 Neurotoxicity data–previously published neurotoxicity data for DHA, artesunate, artemiside, artemisone: Table S6.Supplementary Material 2: PDF copy of reference [37].The South African Medical Research Council (MRC) Flagship Project MALTB-Redox with funds from the National Treasury under its Economic Competitiveness and Support Package, a South African National Research Foundation (SA NRF) grant, and by a South African MRC Strategic Health Innovation Partnership (SHIP) grant, a South African MRC Collaborative Centre for Malaria Research grant and the Department of Science and Innovation and SA NRF South African Research Chairs Initiative (SARChI) Grant.https://www.mdpi.com/journal/pharmaceuticsam2022BiochemistryGeneticsMicrobiology and Plant PathologyUP Centre for Sustainable Malaria Control (UP CSMC

Anthracene-polyamine conjugates inhibit in vitro proliferation of intraerythrocytic Plasmodium falciparum parasites

Anthracene-polyamine conjugates inhibit the in vitro proliferation of the intraerythrocytic human malaria parasite, Plasmodium falciparum, with IC50 values in the nM-μM range. The compounds are taken up into the intraerythrocytic parasite where they arrest the parasite cell-cycle. Both the anthracene and polyamine components of the conjugates play a role in their antiplasmodial effect.JN was supported by the Carl and Emily Fuchs foundation, AusAID, the Ernst and Ethel Eriksen Trust, UP Mentorship Programme and the Claude Leon Foundation. This work was supported by the South African Medical Research Council, the South African National Research Foundation KISC programme (UID 67444), and the Australian National Health and Medical Research Council [Grant no. 525428 to KK].http://aac.asm.orghb201