Inner membrane complex proteomics reveals a palmitoylation regulation critical for intraerythrocytic development of malaria parasite.

Malaria is caused by infection of the erythrocytes by the parasites Plasmodium. Inside the erythrocytes, the parasites multiply via schizogony, an unconventional cell division mode. The inner membrane complex (IMC), an organelle located beneath the parasite plasma membrane, serving as the platform for protein anchorage, is essential for schizogony. So far, the complete repertoire of IMC proteins and their localization determinants remain unclear. Here we used biotin ligase (TurboID)-based proximity labeling to compile the proteome of the schizont IMC of the rodent malaria parasite Plasmodium yoelii. In total, 300 TurboID-interacting proteins were identified. 18 of 21 selected candidates were confirmed to localize in the IMC, indicating good reliability. In light of the existing palmitome of Plasmodium falciparum, 83 proteins of the P. yoelii IMC proteome are potentially palmitoylated. We further identified DHHC2 as the major resident palmitoyl-acyl-transferase of the IMC. Depletion of DHHC2 led to defective schizont segmentation and growth arrest both in vitro and in vivo. DHHC2 was found to palmitoylate two critical IMC proteins CDPK1 and GAP45 for their IMC localization. In summary, this study reports an inventory of new IMC proteins and demonstrates a central role of DHHC2 in governing the IMC localization of proteins during the schizont development.

Chemoprotective antimalarials identified through quantitative high-throughput screening of Plasmodium blood and liver stage parasites.

The spread of Plasmodium falciparum parasites resistant to most first-line antimalarials creates an imperative to enrich the drug discovery pipeline, preferably with curative compounds that can also act prophylactically. We report a phenotypic quantitative high-throughput screen (qHTS), based on concentration-response curves, which was designed to identify compounds active against Plasmodium liver and asexual blood stage parasites. Our qHTS screened over 450,000 compounds, tested across a range of 5 to 11 concentrations, for activity against Plasmodium falciparum asexual blood stages. Active compounds were then filtered for unique structures and drug-like properties and subsequently screened in a P. berghei liver stage assay to identify novel dual-active antiplasmodial chemotypes. Hits from thiadiazine and pyrimidine azepine chemotypes were subsequently prioritized for resistance selection studies, yielding distinct mutations in P. falciparum cytochrome b, a validated antimalarial drug target. The thiadiazine chemotype was subjected to an initial medicinal chemistry campaign, yielding a metabolically stable analog with sub-micromolar potency. Our qHTS methodology and resulting dataset provides a large-scale resource to investigate Plasmodium liver and asexual blood stage parasite biology and inform further research to develop novel chemotypes as causal prophylactic antimalarials.

In vitro reduction of Plasmodium falciparum gametocytes: Artemisia spp. tea infusions vs. artemisinin.

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia annua has a long history of use in Southeast Asia where it was used to treat "fever", and A. afra has a similar history in southern Africa. Since their discovery, A. annua use, in particular, has expanded globally with millions of people using the plant in therapeutic tea infusions, mainly to treat malaria. AIM OF THE STUDY: In this study, we used in vitro studies to query if and how A. annua and A. afra tea infusions being used across the globe affect asexual Plasmodium falciparum parasites, and their sexual gametocytes. MATERIALS AND METHODS: P. falciparumstrain NF54 was grown in vitro, synchronized, and induced to form gametocytes using N-acetylglucosamine. Cultures during asexual, early, and late stage gametocytogenesis were treated with artemisinin, methylene blue, and A. annua and A. afra tea infusions (5 g DW/L) using cultivars that contained 0-283 µM artemisinin. Asexual parasitemia and gametocytemia were analyzed microscopically. Gametocyte morphology also was scored. Markers of early (PfGEXP5) and late stage (Pfs25) gametocyte gene expression also were measured using RT-qPCR. RESULTS: Both A. annua and A. afra tea infusions reduced gametocytemia in vitro, and the effect was mainly artemisinin dependent. Expression levels of both marker genes were reduced and also occurred with the effect mainly attributed to artemisinin content of four tested Artemisia cultivars. Tea infusions of both species also inhibited asexual parasitemia and although mainly artemisinin dependent, there was a weak antiparasitic effect from artemisinin-deficient A. afra. CONCLUSIONS: These results showed that A. annua and to a lesser extent, A. afra, inhibited parasitemia and gametocytemia in vitro.

Specialized antiplasmodial secondary metabolites from Aspergillus niger 58, an endophytic fungus from Terminalia catappa.

ETHNOPHARMACOLOGICAL RELEVANCE: Terminalia catappa L. (West Indian-Almond) is a medicinal plant used in traditional medicine for the treatment of infectious diseases. Moreover, various organic extracts prepared from this plant have been reported to exhibit antiplasmodial activity. AIM OF THE STUDY: The need for new antimalarials is still an urgency driven by the alarmingly high burden of malaria in endemic regions, with multitude of people dying annually. We have previously identified an endophytic fungus Aspergillus niger 58 harboured by T. catappa as having promising specialized secondary metabolites against the malaria parasites. In the present study, we report the antiplasmodial activity-guided chromatographic isolation of some metabolites secreted by this endophytic fungus. MATERIALS AND METHODS: The SYBR Green I-based fluorescence microtiter plate assay was used to monitor the growth of Plasmodium falciparum parasites in culture in the presence and absence of inhibitors and results were validated by microscopic analysis of Giemsa-stained culture smears. Giemsa-stain microscopy was also used to study the cell cycle stage-specific action of selected fractions. RESULTS: The results revealed that the multidimensional purification of the crude extract (IC50: 4.03 µg/mL) provided RPHPLC F17 (IC50: 0.09 µg/mL) and RPHPLC F18 (IC50: 0.1 µg/mL) with activity against P. falciparum 3D7 (Pf3D7) strain. Moreover, both fractions at IC99 (0.5 µg/mL) exhibited multi-stages action by targeting all the three stages of the life cycle of blood-stage Pf3D7. Two compounds, flavasperone (1) and aurasperone A (2) were isolated, of which aurasperone A exhibited good potency against Pf3D7 (IC50: 4.17 µM) and P. falciparum INDO (PfINDO) (IC50: 3.08 µM). CONCLUSION: Our study adds credence to the notion that endophytic extracts are potential storehouses for potent specialized secondary metabolites that can be harnessed to fight the malaria parasite and reduce the burden of this disease worldwide. An endophyte that can be cultured in laboratory with ability to secrete promising metabolites of medicinal value holds the promise of conserving Nature from the threat of annihilation of flora for medicinal purposes.

Antimicrobial investigation of ethnobotanically selected guinean plant species.

ETHNOPHARMACOLOGICAL RELEVANCE: In Guinea, medicinal plants play an important role in the management of infectious diseases including urinary disorders, skin diseases and oral diseases. This study was carried out to collect medicinal plant species employed for the treatment of these diseases and to investigate their antimicrobial potential. MATERIALS AND METHODS: Based on an ethnobotanical investigation carried out in three Guinean regions, 74 traditional healers and 28 herbalists were interviewed and medicinal plants were collected. The most quoted plant species were evaluated for their antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, and in addition against Plasmodium falciparum. RESULTS: A total of 112 plant species belonging to 102 genera distributed over 42 botanical families were inventoried. Among the selected plant species, promising activities against C. albicans were obtained for the methanolic extracts of the stem bark of Terminalia albida (IC50 1.2 µg/ml), the leaves of Tetracera alnifolia (IC50 1.6 µg/ml) and the root bark of Swartzia madagascariensis (IC50 7.8 µg/ml). The highest activity against S. aureus was obtained for the dichloromethane extracts of the leaves of Pavetta crassipes (IC50 8.5 µg/ml) and the root of Swartzia madagascariensis (IC50 12.8 µg/ml). Twenty one extracts, obtained from twelve plant species, were strongly active against Plasmodium falciparum, including the dichloromethane extracts of the root and stem bark of Terminalia albida root (IC50 0.6 and 0.8 µg/ml), the leaves of Landolphia heudelotii (IC50 0.5 µg/ml), the stem bark of Combretum paniculatum (IC50 0.4 µg/ml) and the leaves of Gardenia ternifolia (IC50 1.3 µg/ml). CONCLUSION: The present study provides a comprehensive overview of medicinal plants employed by Guinean traditional healers for the treatment of various microbial diseases, including urinary disorders, skin diseases and oral diseases. Some of the studied plant species showed promising antimicrobial activity and could be considered as a potential source for the development of new antifungal and/or antimalarial agents.

Chemical profiling and quantification of potential active constituents responsible for the antiplasmodial activity of Cissampelos pareira.

ETHNOPHARMACOLOGICAL RELEVANCE: Cissampelos pareira is used traditionally in India as a remedy for the treatment of various diseases including malaria but the active ingredients responsible for antiplasmodial activity have not yet been investigated. AIM OF THE STUDY: The identification and quantification of compounds responsible for antiplasmodial activity in different parts (leaf, stem and root) of C. pareira is the target of current study. MATERIAL AND METHODS: The hydro ethanolic parent extracts of different parts of C. pareira and fractions prepared from these extracts were evaluated against Pf3D7 (chloroquine sensitive) and PfINDO (chloroquine resistance) strains in culture to quantify the IC50 for extracts and fractions. Promising fractions of root part of plant were subjected to silica gel column chromatography to obtain pure compounds and their structures were elucidated by detailed spectroscopic analysis. Pure compounds were also tested against Pf3D7 and PfINDO strains. A rapid and simple UPLC-DAD method was developed for the identification and quantification of pharmaceutically important metabolites of C. pareira. RESULTS: Among different extracts, the hydro ethanolic extract of root part of C. pareira was found most active with IC50 values (µg/ml) of 1.42 and 1.15 against Pf 3D7 and Pf INDO, respectively. Tested against Pf 3D7 the most potent fractions were root ethyl acetate fraction (IC50 4.0 µg/ml), stem water fraction (IC50 4.4 µg/ml), and root water fraction (IC50 8.5 µg/ml). Further, phytochemical investigation of active fractions of root part led to the isolation and characterization of a new isoquinoline alkaloid, namely pareirarine (8), along with five known compounds magnoflorine (5), magnocurarine (10), salutaridine (11), cissamine (13) and hayatinine (15). Hayatinine (15), a bisbenzylisoquinoline alkaloid, isolated from root ethyl acetate fraction was most promising compound with IC50 of 0.41 µM (Pf INDO) and 0.509 µM (Pf 3D7). Magnocurarine (10) and cissamine (13) were also found active with IC50 values of 12.51 and 47.34 µM against Pf INDO and 12.54 and 8.76 µM against Pf 3D7, respectively. A total of thirty compounds were detected in studied extracts and fractions, structures were assigned to 15 of these and five of these biologically important compounds were quantified. Isolation of saluteridine (11) from C. pareira and the evaluation of antiplasmodial activity of pure compound from C. pariera is disclosed for the first time. CONCLUSION: This study concludes that the antimalarial potential of C. pareira may be attributed to isoquinoline type alkaloids present in this plant and also provides the scientific evidence for the traditional use of this plant in treatment of malaria.

In silico, in vitro and in vivo evaluation of natural Bignoniaceous naphthoquinones in comparison with atovaquone targeting the selection of potential antimalarial candidates.

The natural naphthoquinones lapachol, α- and ß-lapachone are found in Bignoniaceous Brazilian plant species of the Tabebuia genus (synonym Handroanthus) and are recognized for diverse bioactivities, including as antimalarial. The aim of the present work was to perform in silico, in vitro and in vivo studies to evaluating the antimalarial potential of these three naphthoquinones in comparison with atovaquone, a synthetic antimalarial. The ADMET properties of these compounds were predicted in silico by the preADMET program. The in vitro toxicity assays were experimentally determined in immortalized and tumoral cells from different organs. In vivo acute oral toxicity was also evaluated for lapachol. Several favorable pharmacokinetics data were predicted although, as expected, high cytotoxicity was experimentally determined for ß-lapachone. Lapachol was not cytotoxic or showed low cytotoxicity to all of the cells assayed (HepG2, A549, Neuro 2A, LLC-PK1, MRC-5), it was nontoxic in the acute oral test and disclosed the best parasite selectivity index in the in vitro assays against chloroquine resistant Plasmodium falciparum W2 strain. On the other hand, α- and ß-lapachone were more potent than lapachol in the antiplasmodial assays but with low parasite selectivity due to their cytotoxicity. The diversity of data here reported disclosed lapachol as a promising candidate to antimalarial drug development.

Effect of Dihydroartemisinin on Plasmodium NADH-Dependent Glutamate Synthase: The Implication in Malaria Management.

Artemisinin and its analogues (ARTs) are currently the most effective anti-malarial drugs, but the precise mechanism of action is still highly controversial. Effects of ARTs on Plasmodium genes expression are studied in our Lab. The overexpression of an interesting amidotransferase, NADH-dependent glutamate synthase (NADH-GltS) was found in treated by dihydroartemisinin (DHA). The increased expression occurred not only from global transcriptomics analysis on the human malaria parasite Plasmodium falciparum (P. falciparum) 3D7 and gene expression screening on all of iron-sulphur cluster proteins from P.f. 3D7 in vitro but also from Plasmodium berghei (P. berghei) ANKA in mice. Influence of DHA on NADH-GltS was specifically at trophozoite stage of P. falciparum and in a dose-dependent manner below the effective doses. L-glutamine (Gln) and L-glutamate (Glu) are the substrate and product of NADH-GltS respectively. Azaserine (Aza) is specific inhibitor for NADH-GltS. Experimental data showed that Glu levels were significantly decreasing with DHA dose increasing but NADH-GltS enzyme activities were still remained at higher levels in parasites, and appropriate amount of exogenous Glu could significantly reduce anti-malarial action of DHA but excessive amount lost the above effect. Aza alone could inhibit proliferation of P. falciparum and had an additive effect in combination with DHA. Those results could suggest that: Glutamate depletion is one of the anti-malarial actions of DHA; overexpression of NADH-GltS would be a feedback pattern of parasite itself due to glutamate depletion, but not a direct action of DHA; the "feedback pattern" is one of protective strategies of Plasmodium to interfere with the anti-malarial actions of DHA; and specific inhibitor for NADH-GltS as a new type of anti-malarial agents or new partner in ACT might provide a potential.

In vitro and in vivo studies on anti-malarial activity of Commiphora africana and Dichrostachys cinerea used by the Maasai in Arusha region, Tanzania.

BACKGROUND: Traditional medicinal plants are one of the potential sources of anti-malarial drugs and there is an increasing interest in the use and development of traditional herbal remedies for the treatment of malaria and other ailments. This study was carried out with the aim to investigate the phytochemical screening, cytotoxic effect and antiplasmodial activities of Dichrostachys cinerea and Commiphora africana. Both plants are used by the Maasai in Tanzania in suspected malaria and other diseases. No previous work appears to have investigated the potential anti-malarial activity of the two plants. METHODS: This study aimed to investigate the in vitro anti-malarial activity of methanol and dichloromethane extracts of the two plants against chloroquine sensitive (D6) and chloroquine resistant (Dd2) strains of Plasmodium falciparum. The anti-malarial property was assessed by the lactate dehydrogenase method (pLDH). The in vivo anti-malarial study was carried out using the Peters' 4-day suppressive test in Plasmodium berghei in Balb/c mice. Cytotoxic tests were carried out using monkey kidney epithelial cell line in [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay. Qualitative phytochemical screening was carried out using standard methods of analysis. RESULTS: The phytochemical screening of plant extracts revealed the presence of alkaloids, flavonoids, tannins, steroids, triterpenoids, glycosides and saponins. However, alkaloids were absent in most plant extracts. The dichloromethane extracts of C. africana (stem bark); D. cinerea (stem bark) and methanol extracts of D. cinerea (whole stem) all showed promising in vitro anti-malarial activities. All other extracts did not show any significant anti-malarial activity. The two most promising extracts based on in vitro studies, DCM extracts of C. africana (stem bark) and D. cinerea (stems bark), equally exhibited very significant anti-malarial activities in the mouse model. They exhibited parasite suppression rates of 64.24 and 53.12%, respectively, and considerable improvement in weight and survival rate. Most plant extracts were not cytotoxic except for DCM extract of D. cinerea (whole stem) CC50 (29.44 µg/mL). CONCLUSION: The findings of this study provide scientific evidence supporting the traditional use of the plants in the treatment of malaria by the Maasai in Arusha region, Tanzania. Consequently, further work including bioassay-guided fractionation and advanced toxicity testing may yield new anti-malarial drug candidates from the two plants.

Short-term metabolic adjustments in Plasmodium falciparum counter hypoxanthine deprivation at the expense of long-term viability.

BACKGROUND: The malarial parasite Plasmodium falciparum is an auxotroph for purines, which are required for nucleic acid synthesis during the intra-erythrocytic developmental cycle (IDC) of the parasite. The capabilities of the parasite and extent to which it can use compensatory mechanisms to adapt to purine deprivation were studied by examining changes in its metabolism under sub-optimal concentrations of hypoxanthine, the primary precursor utilized by the parasite for purine-based nucleic acid synthesis. METHODS: The concentration of hypoxanthine that caused a moderate growth defect over the course of one IDC was determined. At this concentration of hypoxanthine (0.5 µM), transcriptomic and metabolomic data were collected during one IDC at multiple time points. These data were integrated with a metabolic network model of the parasite embedded in a red blood cell (RBC) to interpret the metabolic adaptation of P. falciparum to hypoxanthine deprivation. RESULTS: At a hypoxanthine concentration of 0.5 µM, vacuole-like structures in the cytosol of many P. falciparum parasites were observed after the 24-h midpoint of the IDC. Parasites grown under these conditions experienced a slowdown in the progression of the IDC. After 72 h of deprivation, the parasite growth could not be recovered despite supplementation with 90 µM hypoxanthine. Simulations of P. falciparum metabolism suggested that alterations in ubiquinone, isoprenoid, shikimate, and mitochondrial metabolism occurred before the appearance of these vacuole-like structures. Alterations were found in metabolic reactions associated with fatty acid synthesis, the pentose phosphate pathway, methionine metabolism, and coenzyme A synthesis in the latter half of the IDC. Furthermore, gene set enrichment analysis revealed that P. falciparum activated genes associated with rosette formation, Maurer's cleft and protein export under two different nutrient-deprivation conditions (hypoxanthine and isoleucine). CONCLUSIONS: The metabolic network analysis presented here suggests that P. falciparum invokes specific purine-recycling pathways to compensate for hypoxanthine deprivation and maintains a hypoxanthine pool for purine-based nucleic acid synthesis. However, this compensatory mechanism is not sufficient to maintain long-term viability of the parasite. Although P. falciparum can complete a full IDC in low hypoxanthine conditions, subsequent cycles are disrupted.

The impact of early life exposure to Plasmodium falciparum on the development of naturally acquired immunity to malaria in young Malawian children.

BACKGROUND: Antibodies targeting malaria blood-stage antigens are important targets of naturally acquired immunity, and may act as valuable biomarkers of malaria exposure. METHODS: Six-hundred and one young Malawian children from a randomized trial of prenatal nutrient supplementation with iron and folic acid or pre- and postnatal multiple micronutrients or lipid-based nutrient supplements were followed up weekly at home and febrile episodes were investigated for malaria from birth to 18 months of age. Antibodies were measured for 601 children against merozoite surface proteins (MSP1 19kD, MSP2), erythrocyte binding antigen 175 (EBA175), reticulocyte binding protein homologue 2 (Rh2A9), schizont extract and variant surface antigens expressed by Plasmodium falciparum-infected erythrocytes (IE) at 18 months of age. The antibody measurement data was related to concurrent malaria infection and to documented episodes of clinical malaria. RESULTS: At 18 months of age, antibodies were significantly higher among parasitaemic than aparasitaemic children. Antibody levels against MSP1 19kD, MSP2, schizont extract, and IE variant surface antigens were significantly higher in children who had documented episodes of malaria than in children who did not. Antibody levels did not differ between children with single or multiple malaria episodes before 18 months, nor between children who had malaria before 6 months of age or between 6 and 18 months. CONCLUSIONS: Antibodies to merozoite and IE surface antigens increased following infection in early childhood, but neither age at first infection nor number of malaria episodes substantially affected antibody acquisition. These findings have implications for malaria surveillance during early childhood in the context of elimination. Trials registration Clinical Trials Registration: NCT01239693 (Date of registration: 11-10-2010). URL: http://www.ilins.org.

Antimalarial Pyrido[1,2- a]benzimidazole Derivatives with Mannich Base Side Chains: Synthesis, Pharmacological Evaluation, and Reactive Metabolite Trapping Studies.

A novel series of pyrido[1,2- a]benzimidazoles bearing Mannich base side chains and their metabolites were synthesized and evaluated for in vitro antiplasmodium activity, microsomal metabolic stability, reactive metabolite (RM) formation, and in vivo antimalarial efficacy in a mouse model. Oral administration of one of the derivatives at 4 × 50 mg/kg reduced parasitemia by 95% in Plasmodium berghei-infected mice, with a mean survival period of 16 days post-treatment. The in vivo efficacy of these derivatives is likely a consequence of their active metabolites, two of which showed potent in vitro antiplasmodium activity against chloroquine-sensitive and multidrug-resistant Plasmodium falciparum ( P. falciparum) strains. Rapid metabolism was observed for all the analogues with <40% of parent compound remaining after 30 min of incubation in liver microsomes. RM trapping studies detected glutathione adducts only in derivatives bearing 4-aminophenol moiety, with fragmentation signatures showing that this conjugation occurred on the phenyl ring of the Mannich base side chain. As with amodiaquine (AQ), interchanging the positions of the 4-hydroxyl and Mannich base side group or substituting the 4-hydroxyl with fluorine appeared to block bioactivation of the AQ-like derivatives though at the expense of antiplasmodium activity, which was significantly lowered.

Comparative demography elucidates the longevity of parasitic and symbiotic relationships.

Parasitic and symbiotic relationships govern vast nutrient and energy flows, yet controversy surrounds their longevity. Enduring relationships may engender parallel phylogenies among hosts and parasites, but so may ephemeral relationships when parasites colonize related hosts. An understanding of whether symbiont and host populations have grown and contracted in concert would be useful when considering the temporal durability of these relationships. Here, we devised methods to compare demographic histories derived from genomic data. We compared the historical growth of the agent of severe human malaria, Plasmodium falciparum, and its mosquito vector, Anopheles gambiae, to human and primate histories, thereby discerning long-term parallels and anthropogenic population explosions. The growth history of Trichinella spiralis, a zoonotic parasite disseminated by swine, proved regionally specific, paralleling distinctive growth histories for wild boar in Asia and Europe. Parallel histories were inferred for an anemone and its algal symbiont (Exaiptasia pallida and Symbiodinium minutum). Concerted growth in potatoes and the agent of potato blight (Solanum tuberosum and Phytophthora infestans) did not commence until the age of potato domestication. Through these examples, we illustrate the utility of comparative historical demography as a new exploratory tool by which to interrogate the origins and durability of myriad ecological relationships. To facilitate future use of this approach, we introduce a tool called C-PSMC to align and evaluate the similarity of demographic history curves.

Intermittent screening and treatment with artemether-lumefantrine versus intermittent preventive treatment with sulfadoxine-pyrimethamine for malaria in pregnancy: a facility-based, open-label, non-inferiority trial in Nigeria.

BACKGROUND: The spread of SP resistance may compromise the effectiveness of intermittent preventive treatment of malaria in pregnancy (MiP) with sulfadoxine-pyrimethamine (IPTp-SP) across Africa. However, there is no recommended alternative medicine for IPTp or alternative strategy for prevention of MiP. This poses problems for the prevention of MiP. This study investigated, whether screening with a rapid diagnostic test for malaria at routine antenatal clinic attendances and treatment of only those who are positive (intermittent screening and treatment) with artemether-lumefantrine is as effective and safe as IPTp-SP in pregnant women. METHODS: During antenatal clinic sessions at the General Hospital Calabar, Nigeria, held between October 2013 and November 2014, 459 pregnant women were randomized into either the current standard IPTp-SP or intermittent screening and treatment with artemether-lumefantrine (ISTp-AL). All women received a long-lasting insecticide-treated net at enrolment. Study women had a maximum of four scheduled visits following enrolment. Haemoglobin concentration and peripheral parasitaemia were assessed in the third trimester (36-40 weeks of gestation). Birth weight was documented at delivery or within a week for babies delivered at home. RESULTS: In the third trimester, the overall prevalence of severe anaemia (Hb < 8 g/dl) and moderate (8-10.9 g/dl) anaemia was 0.8 and 27.7%, respectively, and was similar in both treatment groups (p = 0.204). The risk of third-trimester severe anaemia did not differ significantly between both treatment arms (risk difference - 1.75% [95% CI - 4.16 to 0.66]) although the sample was underpowered for this outcome due to several participants being unavailable to give a blood sample. The risk of third-trimester maternal parasitaemia was significantly lower in the ISTp-AL arm (RD - 3.96% [95% CI - 7.76 to - 0.16]). The risk of low birthweight was significantly lower in the ISTp-AL arm after controlling for maternal age, gravidity and baseline parasitaemia (risk difference - 1.53% [95% CI - 1.54 to - 1.15]). Women in the ISTp-AL arm complained of fever more frequently compared to women in the IPTp-SP arm (p = 0.022). CONCLUSIONS: The trial results suggest that in an area of high malaria transmission with moderate sulfadoxine-pyrimethamine resistance, ISTp with artemether-lumefantrine may be an effective strategy for controlling malaria in pregnancy. Trial registration PACTR, PACTR201308000543272. Registered 29 April 2013, http://www.pactr.org/ATMWeb/appmanager/atm/atmregistry?dar=true&tNo=PACTR201308000543272.

HSQC-TOCSY Fingerprinting-Directed Discovery of Antiplasmodial Polyketides from the Marine Ascidian-Derived Streptomyces sp. (USC-16018).

Chemical investigations on the fermentation extract obtained from an ascidian-derived Streptomyces sp. (USC-16018) yielded a new ansamycin polyketide, herbimycin G (1), as well as a known macrocyclic polyketide, elaiophylin (2), and four known diketopiperazines (3⁻6). The structures of the compounds were elucidated based on 1D/2D NMR and MS data. The absolute configuration of 1 was established by comparison of experimental and predicted electronic circular dichroism (ECD) data. Antiplasmodial activities were tested for the natural products against chloroquine sensitive (3D7) and chloroquine resistant (Dd2) Plasmodium falciparum strains; the two polyketides (1⁻2) demonstrated an inhibition of >75% against both parasite strains and while 2 was highly cytotoxic, herbimycin G (1) showed no cytotoxicity and good predicted water solubility.

Increased Ca++ uptake by erythrocytes infected with malaria parasites: Evidence for exported proteins and novel inhibitors.

Malaria parasites export many proteins into their host erythrocytes and increase membrane permeability to diverse solutes. Although most solutes use a broad-selectivity channel known as the plasmodial surface anion channel, increased Ca++ uptake is mediated by a distinct, poorly characterised mechanism that appears to be essential for the intracellular parasite. Here, we examined infected cell Ca++ uptake with a kinetic fluorescence assay and the virulent human pathogen, Plasmodium falciparum. Cell surface labelling with N-hydroxysulfosuccinimide esters revealed differing effects on transport into infected and uninfected cells, indicating that Ca++ uptake at the infected cell surface is mediated by new or altered proteins at the host membrane. Conditional knockdown of PTEX, a translocon for export of parasite proteins into the host cell, significantly reduced infected cell Ca++ permeability, suggesting involvement of parasite-encoded proteins trafficked to the host membrane. A high-throughput chemical screen identified the first Ca++ transport inhibitors active against Plasmodium-infected cells. These novel chemical scaffolds inhibit both uptake and parasite growth; improved in vitro potency at reduced free [Ca++ ] is consistent with parasite killing specifically via action on one or more Ca++ transporters. These inhibitors should provide mechanistic insights into malaria parasite Ca++ transport and may be starting points for new antimalarial drugs.

Effect of nutrient supplementation on the acquisition of humoral immunity to Plasmodium falciparum in young Malawian children.

BACKGROUND: There is evidence that suggests that undernutrition has a detrimental effect on malarial immunity in children. The aim of the study was to discover whether nutrient supplementation improved development of malarial antibody immunity in children up to 18 months of age. METHODS: The study was conducted with a subset of 432 Malawian children from a randomized controlled trial of nutritional supplements. The arms included pre- and postnatal small-quantity lipid-based nutrient supplements for both mother and child; prenatal supplementation with iron and folic acid; and pre- and postnatal supplementation with multiple micronutrients. Paired plasma samples were collected at 6 and 18 months of age. The levels of antibodies against merozoite surface protein 1 (MSP1 19kD) and MSP2, erythrocyte binding antigen 175 (EBA175), reticulocyte binding protein homologue 2A (Rh2A9), schizont extract and variant antigens expressed on the surface of infected erythrocytes were measured. RESULTS: At 18 months of age, 5.4% of children were parasitaemic by microscopy and 49.1% were anaemic. Antibodies to the tested merozoite antigens and schizont extract increased between 6 and 18 months and this increase was statistically significant for MSP1, MSP2 and EBA175 (p < 0.0001) whereas IgG to variant surface antigens decreased with increasing age (p < 0.0001). However, the supplementation type did not have any impact on the prevalence or levels of antibodies at either 6 or 18 months of age to any of the tested malaria antigens in either univariate analysis or multivariate analysis after adjusting for covariates. CONCLUSIONS: Pre- and postnatal lipid-based nutrient supplementation did not alter malaria antibody acquisition during infancy, compared to prenatal supplementation with iron and folic acid or pre- and postnatal supplementation with multiple micronutrients. Trail registeration Clinicaltrials.gov registration number NCT01239693.

FABRICATION AND EVALUATION OF SMART NANOCRYSTALS OF ARTEMISININ FOR ANTIMALARIAL AND ANTIBACTERIAL EFFICACY.

BACKGROUND: Nanocrystals have the potential to substantially increase dissolution rate, solubility with subsequent enhanced bioavailability via the oral route of a range of poor water soluble drugs. Regardless of other issues, scale up of the batch size is the main issue associated with bottom up approach. MATERIAL AND METHODS: Smart nanocrystals of artemisinin (ARM) was produced relatively at large batch sizes (100, 200, 300 and 400ml) compared to our previously reported study by (Shah, et al., 2016). ARM nanosuspensions/nanocrystals were characterised using zeta sizer, SEM, TEM, DSC, PXRD and RP-HPLC. The nanosuspensions were finally subjected to in vitro antimalarial and antimicrobial activity. RESULTS: The average particle size (PS) for 400 ml batches was 126.5 ±1.02 nm, and the polydispersity index (PI) was 0.194 ± 0.04. The saturation solubility of the ARM nanocrystals was substantially increased to (725.4± 2.0 µg/ml) compared to the raw ARM in water 177.4± 1.3 µg/ml and stabilizer solution (385.3± 2.0 µg/ml). The IC50 value of ARM nanosuspension against P. vivax was 65 and 21 folds lower than micronized 19.5 ng/mL and unprocessed drug (6.4 ng/mL) respectively. The ARM nanosuspension was found highly effective compared to unprocessed drug against all the tested microorganism except E. coli, Shigella and C. albican. CONCLUSION: The simple precipitation-ultrasonication approach was efficiently employed for fabrication of ARM nanosuspension to scale up the batch size. Similarly, the solubility, antimalarial potential and antimicrobial efficacy of ARM in the form of nanosuspension were significantly enhanced. Findings from this study can persuade research interest for further comprehensive studies using animals model.

Bioenergetics-based modeling of Plasmodium falciparum metabolism reveals its essential genes, nutritional requirements, and thermodynamic bottlenecks.

Novel antimalarial therapies are urgently needed for the fight against drug-resistant parasites. The metabolism of malaria parasites in infected cells is an attractive source of drug targets but is rather complex. Computational methods can handle this complexity and allow integrative analyses of cell metabolism. In this study, we present a genome-scale metabolic model (iPfa) of the deadliest malaria parasite, Plasmodium falciparum, and its thermodynamics-based flux analysis (TFA). Using previous absolute concentration data of the intraerythrocytic parasite, we applied TFA to iPfa and predicted up to 63 essential genes and 26 essential pairs of genes. Of the 63 genes, 35 have been experimentally validated and reported in the literature, and 28 have not been experimentally tested and include previously hypothesized or novel predictions of essential metabolic capabilities. Without metabolomics data, four of the genes would have been incorrectly predicted to be non-essential. TFA also indicated that substrate channeling should exist in two metabolic pathways to ensure the thermodynamic feasibility of the flux. Finally, analysis of the metabolic capabilities of P. falciparum led to the identification of both the minimal nutritional requirements and the genes that can become indispensable upon substrate inaccessibility. This model provides novel insight into the metabolic needs and capabilities of the malaria parasite and highlights metabolites and pathways that should be measured and characterized to identify potential thermodynamic bottlenecks and substrate channeling. The hypotheses presented seek to guide experimental studies to facilitate a better understanding of the parasite metabolism and the identification of targets for more efficient intervention.

Anti-plasmodial activity of Norcaesalpin D and extracts of four medicinal plants used traditionally for treatment of malaria.

BACKGROUND: Malaria is an old life-threatening parasitic disease that is still affecting many people, mainly children living in sub-Saharan Africa. Availability of effective antimalarial drugs played a significant role in the treatment and control of malaria. However, recent information on the emergence of P. falciparum parasites resistant to one of the artemisinin-based combination therapies suggests the need for discovery of new drug molecules. Therefore, this study aimed to evaluate the antiplasmodial activity of extracts, fractions and isolated compound from medicinal plants traditionally used in the treatment of malaria in Tanzania. METHODS: Dry powdered plant materials were extracted by cold macerations using different solvents. Norcaesalpin D was isolated by column chromatography from dichloromethane root extract of Caesalpinia bonducella and its structure was assigned based on the spectral data. Crude extracts, fractions and isolated compound were evaluated for antiplasmodial activity against chloroquine-sensitive P. falciparum (3D7), chloroquine-resistant P. falciparum (Dd2, K1) and artemisinin-resistant P. falciparum (IPC 5202 Battambang, IPC 4912 Mondolkiri) strains using the parasite lactate dehydrogenase assay. RESULTS: The results indicated that extracts of Erythrina schliebenii, Holarrhena pubescens, Dissotis melleri and C. bonducella exhibited antiplasmodial activity against Dd2 parasites. Ethanolic root extract of E. schliebenii had an IC50 of 1.87 µg/mL while methanolic and ethanolic root extracts of H. pubescens exhibited an IC50 = 2.05 µg/mL and IC50 = 2.43 µg/mL, respectively. Fractions from H. pubescens and C. bonducella roots were found to be highly active against K1, Dd2 and artemisinin-resistant parasites. Norcaesalpin D from C. bonducella root extract was active with IC50 of 0.98, 1.85 and 2.13 µg/mL against 3D7, Dd2 and IPC 4912-Mondolkiri parasites, respectively. CONCLUSIONS: Antiplasmodial activity of norcaesalpin D and extracts of E. schliebenii, H. pubescens, D. melleri and C. bonducella reported in this study requires further attention for the discovery of antimalarial lead compounds for future drug development.