scholarly journals Infectivity of Plasmodium falciparum in Malaria-Naive Individuals Is Related to Knob Expression and Cytoadherence of the Parasite

2016 ◽  
Vol 84 (9) ◽  
pp. 2689-2696 ◽  
Author(s):  
Danielle I. Stanisic ◽  
John Gerrard ◽  
James Fink ◽  
Paul M. Griffin ◽  
Xue Q. Liu ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Ex Vivo ◽  
Cell Bank ◽  
Human Environment ◽  
Content Type ◽  
Antibody Recognition ◽  
Cell Banks ◽  
Study Participants

Plasmodium falciparumis the most virulent human malaria parasite because of its ability to cytoadhere in the microvasculature. Nonhuman primate studies demonstrated relationships among knob expression, cytoadherence, and infectivity. This has not been examined in humans. Cultured clinical-gradeP. falciparumparasites (NF54, 7G8, and 3D7B) andex vivo-derived cell banks were characterized. Knob and knob-associated histidine-rich protein expression, CD36 adhesion, and antibody recognition of parasitized erythrocytes (PEs) were evaluated. Parasites from the cell banks were administered to malaria-naive human volunteers to explore infectivity. For the NF54 and 3D7B cell banks, blood was collected from the study participants forin vitrocharacterization. All parasites were infectivein vivo. However, infectivity of NF54 was dramatically reduced.In vitrocharacterization revealed that unlike other cell bank parasites, NF54 PEs lacked knobs and did not cytoadhere. Recognition of NF54 PEs by immune sera was observed, suggestingP. falciparumerythrocyte membrane protein 1 expression. Subsequent recovery of knob expression and CD36-mediated adhesion were observed in PEs derived from participants infected with NF54. Knobless cell bank parasites have a dramatic reduction in infectivity and the ability to adhere to CD36. Subsequent infection of malaria-naive volunteers restored knob expression and CD36-mediated cytoadherence, thereby showing that the human environment can modulate virulence.

scholarly journals Ex VivoMaturation Assay for Testing Antimalarial Sensitivity of Rodent Malaria Parasites

2016 ◽  
Vol 60 (11) ◽  
pp. 6859-6866 ◽  
Author(s):  
Zi Wei Chang ◽  
Benoit Malleret ◽  
Bruce Russell ◽  
Laurent Rénia ◽  
Carla Claser
Keyword(s):  
Ex Vivo ◽  
Single Step ◽  
Parasite Development ◽  
Ring Stage ◽  
Malaria Parasites ◽  
Rodent Malaria ◽  
Content Type ◽  
Parasite Biology

ABSTRACTEx vivoassay systems provide a powerful approach to studying human malaria parasite biology and to testing antimalarials. For rodent malaria parasites, short-termin vitroculture andex vivoantimalarial susceptibility assays are relatively cumbersome, relying onin vivopassage for synchronization, since ring-stage parasites are an essential starting material. Here, we describe a new approach based on the enrichment of ring-stagePlasmodium berghei,P. yoelii, andP. vinckei vinckeiusing a single-step Percoll gradient. Importantly, we demonstrate that the enriched ring-stage parasites develop synchronously regardless of the parasite strain or species used. Using a flow cytometry assay with Hoechst and ethidium or MitoTracker dye, we show that parasite development is easily and rapidly monitored. Finally, we demonstrate that this approach can be used to screen antimalarial drugs.

scholarly journals Intestinal IgA Regulates Expression of a Fructan Polysaccharide Utilization Locus in Colonizing Gut Commensal Bacteroides thetaiotaomicron

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Payal Joglekar ◽  
Hua Ding ◽  
Pablo Canales-Herrerias ◽  
Pankaj Jay Pasricha ◽  
Justin L. Sonnenburg ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Ex Vivo ◽  
Microbial Colonization ◽  
Bacteroides Thetaiotaomicron ◽  
Content Type ◽  
Microbial Utilization ◽  
Polysaccharide Utilization Locus ◽  
The Impact

ABSTRACT Gut-derived immunoglobulin A (IgA) is the most abundant antibody secreted in the gut that shapes gut microbiota composition and functionality. However, most of the microbial antigens targeted by gut IgA remain unknown, and the functional effects of IgA targeting these antigens are currently understudied. This study provides a framework for identifying and characterizing gut microbiota antigens targeted by gut IgA. We developed a small intestinal ex vivo culture assay to harvest lamina propria IgA from gnotobiotic mice, with the aim of identifying antigenic targets in a model human gut commensal, Bacteroides thetaiotaomicron VPI-5482. Colonization by B. thetaiotaomicron induced a microbe-specific IgA response that was reactive against diverse antigens, including capsular polysaccharides, lipopolysaccharides, and proteins. IgA against microbial protein antigens targeted membrane and secreted proteins with diverse functionalities, including an IgA specific against proteins of the polysaccharide utilization locus (PUL) that are necessary for utilization of fructan, which is an important dietary polysaccharide. Further analyses demonstrated that the presence of dietary fructan increased the production of fructan PUL-specific IgA, which then downregulated the expression of fructan PUL in B. thetaiotaomicron, both in vivo and in vitro. Since the expression of fructan PUL has been associated with the ability of B. thetaiotaomicron to colonize the gut in the presence of dietary fructans, our work suggests a novel role for gut IgA in regulating microbial colonization by modulating their metabolism. IMPORTANCE Given the significant impact that gut microbes have on our health, it is essential to identify key host and environmental factors that shape this diverse community. While many studies have highlighted the impact of diet on gut microbiota, little is known about how the host regulates this critical diet-microbiota interaction. In our present study, we discovered that gut IgA targeted a protein complex involved in the utilization of an important dietary polysaccharide: fructan. While the presence of dietary fructans was previously thought to allow unrestricted growth of fructan-utilizing bacteria, our work shows that gut IgA, by targeting proteins responsible for fructan utilization, provides the host with tools that can restrict the microbial utilization of such polysaccharides, thereby controlling their growth.

scholarly journals Computational Chemogenomics Drug Repositioning Strategy Enables the Discovery of Epirubicin as a New Repurposed Hit for Plasmodium falciparum and P. vivax

2020 ◽  
Vol 64 (9) ◽  
Author(s):  
Letícia Tiburcio Ferreira ◽  
Juliana Rodrigues ◽  
Gustavo Capatti Cassiano ◽  
Tatyana Almeida Tavella ◽  
Kaira Cristina Peralis Tomaz ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
In Silico ◽  
Antimalarial Activity ◽  
Drug Repositioning ◽  
Dna Gyrase ◽  
Plasmodium Yoelii ◽  
Computer Assisted ◽  
Content Type

ABSTRACT Widespread resistance against antimalarial drugs thwarts current efforts for controlling the disease and urges the discovery of new effective treatments. Drug repositioning is increasingly becoming an attractive strategy since it can reduce costs, risks, and time-to-market. Herein, we have used this strategy to identify novel antimalarial hits. We used a comparative in silico chemogenomics approach to select Plasmodium falciparum and Plasmodium vivax proteins as potential drug targets and analyzed them using a computer-assisted drug repositioning pipeline to identify approved drugs with potential antimalarial activity. Among the seven drugs identified as promising antimalarial candidates, the anthracycline epirubicin was selected for further experimental validation. Epirubicin was shown to be potent in vitro against sensitive and multidrug-resistant P. falciparum strains and P. vivax field isolates in the nanomolar range, as well as being effective against an in vivo murine model of Plasmodium yoelii. Transmission-blocking activity was observed for epirubicin in vitro and in vivo. Finally, using yeast-based haploinsufficiency chemical genomic profiling, we aimed to get insights into the mechanism of action of epirubicin. Beyond the target predicted in silico (a DNA gyrase in the apicoplast), functional assays suggested a GlcNac-1-P-transferase (GPT) enzyme as a potential target. Docking calculations predicted the binding mode of epirubicin with DNA gyrase and GPT proteins. Epirubicin is originally an antitumoral agent and presents associated toxicity. However, its antiplasmodial activity against not only P. falciparum but also P. vivax in different stages of the parasite life cycle supports the use of this drug as a scaffold for hit-to-lead optimization in malaria drug discovery.

scholarly journals Ex VivoDrug Susceptibility of Ferroquine against Chloroquine-Resistant Isolates of Plasmodium falciparum and P. vivax

2011 ◽  
Vol 55 (9) ◽  
pp. 4461-4464 ◽  
Author(s):  
Jutta Marfurt ◽  
Ferryanto Chalfein ◽  
Pak Prayoga ◽  
Frans Wabiser ◽  
Enny Kenangalem ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Combination Therapy ◽  
Drug Class ◽  
Ex Vivo ◽  
Multidrug Resistant ◽  
Drug Action ◽  
Drug Uptake ◽  
Content Type ◽  
Excellent Activity

ABSTRACTFerroquine (FQ; SSR97193), a ferrocene-containing 4-aminoquinoline derivate, has potentin vitroefficacy against chloroquine (CQ)-resistantPlasmodium falciparumand CQ-sensitiveP. vivax. In the current study,ex vivoFQ activity was tested in multidrug-resistantP. falciparumandP. vivaxfield isolates using a schizont maturation assay. Although FQ showed excellent activity against CQ-sensitive and -resistantP. falciparumandP. vivax(median 50% inhibitory concentrations [IC50s], 9.6 nM and 18.8 nM, respectively), there was significant cross-susceptibility with the quinoline-based drugs chloroquine, amodiaquine, and piperaquine (forP. falciparum,r= 0.546 to 0.700,P< 0.001; forP. vivax,r= 0.677 to 0.821,P< 0.001). The observedex vivocross-susceptibility is likely to reflect similar mechanisms of drug uptake/efflux and modes of drug action of this drug class. However, the potent activity of FQ against resistant isolates of bothP. falciparumandP. vivaxhighlights a promising role for FQ as a lead antimalarial against CQ-resistantPlasmodiumand a useful partner drug for artemisinin-based combination therapy.

scholarly journals Listeria monocytogenes MenI Encodes a DHNA-CoA Thioesterase Necessary for Menaquinone Biosynthesis, Cytosolic Survival, and Virulence

2021 ◽  
Vol 89 (5) ◽  
Author(s):  
Hans B. Smith ◽  
Tin Lok Li ◽  
Man Kit Liao ◽  
Grischa Y. Chen ◽  
Zhihong Guo ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Ex Vivo ◽  
Strong Activity ◽  
Content Type ◽  
Transport Chain ◽  
Intermediate Metabolites ◽  
Bacterial Replication ◽  
Functional Analyses

ABSTRACT Listeria monocytogenes is a Gram-positive, intracellular pathogen that is highly adapted to invade and replicate in the cytosol of eukaryotic cells. Intermediate metabolites in the menaquinone biosynthesis pathway are essential for the cytosolic survival and virulence of L. monocytogenes, independent of the production of menaquinone (MK) and aerobic respiration. Determining which specific intermediate metabolite(s) are essential for cytosolic survival and virulence has been hindered by the lack of an identified 1,4-dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) thioesterase essential for converting DHNA-CoA to DHNA in the MK synthesis pathway. Using the recently identified Escherichia coli DHNA-CoA thioesterase as a query, homology sequence analysis revealed a single homolog in L. monocytogenes, LMRG_02730. Genetic deletion of LMRG_02730 resulted in an ablated membrane potential, indicative of a nonfunctional electron transport chain (ETC) and an inability to aerobically respire. Biochemical kinetic analysis of LMRG_02730 revealed strong activity toward DHNA-CoA, similar to its E. coli homolog, further demonstrating that LMRG_02730 is a DHNA-CoA thioesterase. Functional analyses in vitro, ex vivo, and in vivo using mutants directly downstream and upstream of LMRG_02730 revealed that DHNA-CoA is sufficient to facilitate in vitro growth in minimal medium, intracellular replication, and plaque formation in fibroblasts. In contrast, protection against bacteriolysis in the cytosol of macrophages and tissue-specific virulence in vivo requires the production of 1,4-dihydroxy-2-naphthoate (DHNA). Taken together, these data implicate LMRG_02730 (renamed MenI) as a DHNA-CoA thioesterase and suggest that while DHNA, or an unknown downstream product of DHNA, protects the bacteria from killing in the macrophage cytosol, DHNA-CoA is necessary for intracellular bacterial replication.

scholarly journals The Mu Subunit of Plasmodium falciparum Clathrin-Associated Adaptor Protein 2 ModulatesIn VitroParasite Response to Artemisinin and Quinine

2015 ◽  
Vol 59 (5) ◽  
pp. 2540-2547 ◽  
Author(s):  
Gisela Henriques ◽  
Donelly A. van Schalkwyk ◽  
Rebekah Burrow ◽  
David C. Warhurst ◽  
Eloise Thompson ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Adaptor Protein ◽  
Content Type ◽  
Artemisinin Derivatives ◽  
Combination Treatments ◽  
Antimalarial Resistance ◽  
Transgenic Parasites ◽  
Multiple Drugs

ABSTRACTThe emergence of drug-resistant parasites is a serious threat faced by malaria control programs. Understanding the genetic basis of resistance is critical to the success of treatment and intervention strategies. A novel locus associated with antimalarial resistance,ap2-mu(encoding the mu chain of the adaptor protein 2 [AP2] complex), was recently identified in studies on the rodent malaria parasitePlasmodium chabaudi(pcap2-mu). Furthermore, analysis in Kenyan malaria patients of polymorphisms in thePlasmodium falciparumap2-muhomologue,pfap2-mu, found evidence that differences in the amino acid encoded by codon 160 are associated with enhanced parasite survivalin vivofollowing combination treatments which included artemisinin derivatives. Here, we characterize the role ofpfap2-muin mediating thein vitroantimalarial drug response ofP. falciparumby generating transgenic parasites constitutively expressing codon 160 encoding either the wild-type Ser (Ser160) or the Asn mutant (160Asn) form ofpfap2-mu. Transgenic parasites carrying thepfap2-mu160Asn allele were significantly less sensitive to dihydroartemisinin using a standard 48-hin vitrotest, providing direct evidence of an altered parasite response to artemisinin. Our data also provide evidence thatpfap2-muvariants can modulate parasite sensitivity to quinine. No evidence was found thatpfap2-muvariants contribute to the slow-clearance phenotype exhibited byP. falciparumin Cambodian patients treated with artesunate monotherapy. These findings provide compelling evidence thatpfap2-mucan modulateP. falciparumresponses to multiple drugs. We propose that this gene should be evaluated further as a potential molecular marker of antimalarial resistance.

scholarly journals In VitroandIn VivoAntimalarial Activities of T-2307, a Novel Arylamidine

2012 ◽  
Vol 56 (4) ◽  
pp. 2191-2193 ◽  
Author(s):  
Akiko Kimura ◽  
Hiroshi Nishikawa ◽  
Nobuhiko Nomura ◽  
Junichi Mitsuyama ◽  
Shinya Fukumoto ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Body Weight ◽  
Broad Spectrum ◽  
Antimalarial Activity ◽  
Liver Stage ◽  
Rodent Malaria ◽  
Content Type ◽  
Clinically Significant

ABSTRACTT-2307, a novel arylamidine, has been shown to exhibit broad-spectrum antifungal activities against clinically significant pathogens. Here, we evaluated thein vitroandin vivoantimalarial activity of T-2307. The 50% inhibitory concentrations (IC50s) of T-2307 againstPlasmodium falciparumFCR-3 and K-1 strains were 0.47 and 0.17 μM, respectively. T-2307 at 2.5 to 10 mg/kg of body weight/day exhibited activity against blood stage and liver stage parasites in rodent malaria models. In conclusion, T-2307 exhibitedin vitroandin vivoantimalarial activity.

Applications of monoclonal antibodies in the diagnosis and treatment of primary brain tumors

1985 ◽  
Vol 63 (1) ◽  
pp. 2-16 ◽  
Author(s):  
Dennis E. Bullard ◽  
Darell D. Bigner
Keyword(s):  
Monoclonal Antibodies ◽  
Ex Vivo ◽  
Neuroectodermal Tumor ◽  
Diagnosis And Treatment ◽  
Early Application ◽  
Content Type ◽  
Tumor Associated Antigens ◽  
Neuroectodermal Tumors

✓ The development of monoclonal antibodies has resulted in marked expansion in understanding the central nervous system (CNS). This has been especially true in the study of human neuroectodermal tumors where monoclonal antibodies have been used as physiological probes to define and characterize human neuroectodermal tumor-associated antigens. Utilizing monoclonal antibodies, neuroectodermal tumor-associated antigens have been described in four broad categories; biochemically defined markers, shared nervous systemlymphoid cell markers, shared neuroectodermal-oncofetal markers, and putative restricted tumor markers. Preliminary data have demonstrated the ability to localize animal and human tumors in vitro, ex vivo, and in vivo. Early application of monoclonal antibody technology to neuroimmunology and neuro-oncology has resulted in a new awareness of the complex relationships that exist within the CNS. Their specificity and reproducibility may provide the means to qualitatively and quantitatively define the phenotypic heterogeneity of human neuroectodermal tumors. Potentially, monoclonal antibodies, alone or as carriers of radionuclides, drugs, or toxins, may allow successful diagnosis and treatment of human neuroectodermal tumors.

scholarly journals In Vitro, Ex Vivo, and In Vivo Activities of Diamidines against Trypanosoma congolense and Trypanosoma vivax

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Kirsten Gillingwater ◽  
Christina Kunz ◽  
Christiane Braghiroli ◽  
David W. Boykin ◽  
Richard R. Tidwell ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Trypanosoma Congolense ◽  
Tsetse Fly ◽  
Sub Saharan Africa ◽  
Content Type ◽  
Lead Compounds ◽  
Single Bolus Dose ◽  
Sub Saharan

ABSTRACT African animal trypanosomosis (AAT) is caused by the tsetse fly-transmitted protozoans Trypanosoma congolense and T. vivax and leads to huge agricultural losses throughout sub-Saharan Africa. Three drugs are available to treat nagana in cattle (diminazene diaceturate, homidium chloride, and isometamidium chloride). With increasing reports of drug-resistant populations, new molecules should be investigated as potential candidates to combat nagana. Dicationic compounds have been demonstrated to have excellent efficacy against different kinetoplastid parasites. This study therefore evaluated the activities of 37 diamidines, using in vitro and ex vivo drug sensitivity assays. The 50% inhibitory concentrations obtained ranged from 0.007 to 0.562 μg/ml for T. congolense and from 0.019 to 0.607 μg/ml for T. vivax. On the basis of these promising results, 33 of these diamidines were further examined using in vivo mouse models of infection. Minimal curative doses of 1.25 mg/kg of body weight for both T. congolense- and T. vivax-infected mice were seen when the diamidines were administered intraperitoneally (i.p.) over 4 consecutive days. From these observations, 15 of these 33 diamidines were then further tested in vivo, using a single bolus dose for administration. The total cure of mice infected with T. congolense and T. vivax was seen with single i.p. doses of 5 and 2.5 mg/kg, respectively. This study identified a selection of diamidines which could be considered lead compounds for the treatment of nagana.

scholarly journals Aminoindoles, a Novel Scaffold with Potent Activity against Plasmodium falciparum

2011 ◽  
Vol 55 (6) ◽  
pp. 2612-2622 ◽  
Author(s):  
Robert H. Barker ◽  
Sameer Urgaonkar ◽  
Ralph Mazitschek ◽  
Cassandra Celatka ◽  
Renato Skerlj ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Parent Compound ◽  
Therapeutic Index ◽  
Preclinical Development ◽  
Drug Pressure ◽  
Content Type ◽  
Novel Scaffold ◽  
Trough Levels

ABSTRACTThis study characterizes aminoindole molecules that are analogs of Genz-644442. Genz-644442 was identified as a hit in a screen of ∼70,000 compounds in the Broad Institute's small-molecule library and the ICCB-L compound collection at Harvard Medical School. Genz-644442 is a potent inhibitor ofPlasmodium falciparum in vitro(50% inhibitory concentrations [IC50s], 200 to 285 nM) and inhibitsP. berghei in vivowith an efficacy of >99% in an adapted version of Peters' 4-day suppressive test (W. Peters, Ann. Trop. Med. Parasitol. 69:155–171, 1975). Genz-644442 became the focus of medicinal chemistry optimization; 321 analogs were synthesized and were tested forin vitropotency againstP. falciparumand forin vitroabsorption, distribution, metabolism, and excretion (ADME) properties. This yielded compounds with IC50s of approximately 30 nM. The lead compound, Genz-668764, has been characterized in more detail. It is a single enantiomer with IC50s of 28 to 65 nM againstP. falciparum in vitro. In the 4-dayP. bergheimodel, when it was dosed at 100 mg/kg of body weight/day, no parasites were detected on day 4 postinfection. However, parasites recrudesced by day 9. Dosing at 200 mg/kg/day twice a day resulted in cures of 3/5 animals. The compound had comparable activity againstP. falciparumblood stages in a human-engrafted NOD-scidmouse model. Genz-668764 had a terminal half-life of 2.8 h and plasma trough levels of 41 ng/ml when it was dosed twice a day orally at 55 mg/kg/day. Seven-day rat safety studies showed a no-observable-adverse-effect level (NOAEL) at 200 mg/kg/day; the compound was not mutagenic in Ames tests, did not inhibit the hERG channel, and did not have potent activity against a broad panel of receptors and enzymes. Employing allometric scaling and usingin vitroADME data, the predicted human minimum efficacious dose of Genz-668764 in a 3-day once-daily dosing regimen was 421 mg/day/70 kg, which would maintain plasma trough levels above the IC90againstP. falciparumfor at least 96 h after the last dose. The predicted human therapeutic index was approximately 3, on the basis of the exposure in rats at the NOAEL. We were unable to select for parasites with >2-fold decreased sensitivity to the parent compound, Genz-644442, over 270 days ofin vitroculture under drug pressure. These characteristics make Genz-668764 a good candidate for preclinical development.

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