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The Journal of Infectious Diseases Nov 2009Gametocytes are the sexual stage of the malaria parasite and are essential for transmission to the mosquito. Antimalarial drugs have been reported to affect gametocyte...
Gametocytes are the sexual stage of the malaria parasite and are essential for transmission to the mosquito. Antimalarial drugs have been reported to affect gametocyte production in vivo, which leads to a potential increase in transmission. We used transgenic Plasmodium falciparum parasites expressing a green fluorescent protein tag in a fluorescence-activated cell sorting-based assay to measure the effect of 8 antimalarial drugs on gametocyte production in vitro. Exposure to antimalarial drugs resulted in an increase in the number of gametocytes in test cultures. Although a dose-dependent reduction in late-stage gametocyte viability was observed, none of the drugs tested statistically significantly reduced gametocyte numbers.
Topics: Animals; Animals, Genetically Modified; Antimalarials; Female; Male; Parasitic Sensitivity Tests; Plasmodium falciparum
PubMed: 19848586
DOI: 10.1086/644645 -
Zhongguo Ji Sheng Chong Xue Yu Ji Sheng... 2001
Review
Topics: Animals; Antigenic Variation; Genes, Protozoan; Plasmodium falciparum; Protozoan Proteins
PubMed: 12571976
DOI: No ID Found -
Experimental Parasitology Dec 1978
Topics: Cells, Cultured; Chloroquine; Erythrocyte Membrane; Erythrocytes; Humans; Plasmodium falciparum
PubMed: 365561
DOI: 10.1016/0014-4894(78)90136-4 -
PloS One 2013Among key potential drug target proteolytic systems in the malaria parasite Plasmodium falciparum are falcipains, a family of hemoglobin-degrading cysteine proteases,...
Among key potential drug target proteolytic systems in the malaria parasite Plasmodium falciparum are falcipains, a family of hemoglobin-degrading cysteine proteases, and the ubiquitin proteasomal system (UPS), which has fundamental importance in cellular protein turnover. Inhibition of falcipains blocks parasite development, primarily due to inhibition of hemoglobin degradation that serves as a source of amino acids for parasite growth. Falcipains prefer P2 leucine in substrates and peptides, and their peptidyl inhibitors with leucine at the P2 position show potent antimalarial activity. The peptidyl inhibitor MG132 (Z-Leu-Leu-Leu-CHO) is a widely used proteasome inhibitor, which also has P2 leucine, and has also been shown to inhibit parasite development. However, the antimalarial targets of MG132 are unclear. We investigated whether MG132 blocks malaria parasite development by inhibiting hemoglobin degradation and/or by targeting the UPS. P. falciparum was cultured with inhibitors of the UPS (MG132, epoxomicin, and lactacystin) or falcipains (E64), and parasites were assessed for morphologies, extent of hemoglobin degradation, and accumulation of ubiquitinated proteins. MG132, like E64 and unlike epoxomicin or lactacystin, blocked parasite development, with enlargement of the food vacuole and accumulation of undegraded hemoglobin, indicating inhibition of hemoglobin degradation by MG132, most likely due to inhibition of hemoglobin-degrading falcipain cysteine proteases. Parasites cultured with epoxomicin or MG132 accumulated ubiquitinated proteins to a significantly greater extent than untreated or E64-treated parasites, indicating that MG132 inhibits the parasite UPS as well. Consistent with these findings, MG132 inhibited both cysteine protease and UPS activities present in soluble parasite extracts, and it strongly inhibited recombinant falcipains. MG132 was highly selective for inhibition of P. falciparum (IC50 0.0476 µM) compared to human peripheral blood mononuclear cells (IC50 10.8 µM). Thus, MG132 inhibits two distinct proteolytic systems in P. falciparum, and it may serve as a lead molecule for development of dual-target inhibitors of malaria parasites.
Topics: Cysteine Endopeptidases; Drug Synergism; Erythrocytes; Hemoglobins; Humans; Leupeptins; Plasmodium falciparum; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteolysis; Ubiquitin
PubMed: 24023882
DOI: 10.1371/journal.pone.0073530 -
International Journal For Parasitology May 2012Mosquito infections with natural isolates of Plasmodium falciparum are notoriously variable and pose a problem for reliable evaluation of efficiency of...
Mosquito infections with natural isolates of Plasmodium falciparum are notoriously variable and pose a problem for reliable evaluation of efficiency of transmission-blocking agents for malaria control interventions. Here, we show that monoclonal P. falciparum isolates produce higher parasite loads than mixed ones. Induction of the mosquito immune responses by wounding efficiently decreases Plasmodium numbers in monoclonal infections but fails to do so in infections with two or more parasite genotypes. Our results point to the parasites genetic complexity as a potentially crucial component of mosquito-parasite interactions.
Topics: Animals; Anopheles; Female; Genetic Variation; Plasmodium falciparum
PubMed: 22554991
DOI: 10.1016/j.ijpara.2012.03.008 -
The American Journal of Tropical... Oct 1998Cultivated Plasmodium falciparum gametocytes reach maturity in vitro in approximately 14-16 days, during which they pass through five morphologically distinct...
Cultivated Plasmodium falciparum gametocytes reach maturity in vitro in approximately 14-16 days, during which they pass through five morphologically distinct developmental stages. Purification of the earlier developmental stages has not been previously reported. We have modified the standard discontinuous Percoll gradient method for the separation of stage IV and V gametocytes to obtain enriched preparations of those and the earlier P. falciparum gametocyte stages. In contrast to the stages II, III, and IV, the mature stage V gametocytes from our gradient readily transformed into gametes. Such preparations may be useful in research studies on the mechanisms that underlie gametocytogenesis.
Topics: Animals; Centrifugation, Density Gradient; Plasmodium falciparum
PubMed: 9790418
DOI: 10.4269/ajtmh.1998.59.505 -
Malaria Journal May 2018In Thailand, artemisinin-based combination therapy (ACT) has been used to treat uncomplicated falciparum malaria since 1995. Unfortunately, artemisinin resistance has...
BACKGROUND
In Thailand, artemisinin-based combination therapy (ACT) has been used to treat uncomplicated falciparum malaria since 1995. Unfortunately, artemisinin resistance has been reported from Thailand and other Southeast Asian countries since 2003. Malarone, a combination of atovaquone-proguanil (ATQ-PG), has been used to cease artemisinin pressure in some areas along Thai-Cambodia border, as part of an artemisinin resistance containment project since 2009. This study aimed to determine genotypes and phenotypes of Plasmodium falciparum isolates collected from the Thai-Cambodia border after the artemisinin resistance containment project compared with those collected before.
RESULTS
One hundred and nine of P. falciparum isolates collected from Thai-Cambodia border from Chanthaburi and Trat provinces during 1988-2016 were used in this study. Of these, 58 isolates were collected after the containment. These parasite isolates were characterized for in vitro antimalarial sensitivities including chloroquine (CQ), quinine (QN), mefloquine (MQ), piperaquine (PPQ), artesunate (AS), dihydroartemisinin (DHA), ATQ and PG and genetic markers for drug resistance including the Kelch13 (k13), Plasmodium falciparum chloroquine resistance transporter (pfcrt), P. falciparum multidrug resistance 1 (pfmdr1) and cytochrome b (cytb) genes. Mean CQ, QN, MQ, PPQ and AS ICs of the parasite isolates collected from 2009 to 2016 exhibited significantly higher than those of parasites collected before 2009. Approximately 57% exhibited in vitro MQ resistance. Approximately 94% of the isolates collected from 2009 to 2016 contained the pfmdr1 184F allele. Mutations of the k13 gene were detected in approximately 90% of the parasites collected from 2009 to 2016 which were significantly higher than the parasite isolates collected before. No ATQ-resistant genotype and phenotype of P. falciparum were found among the isolates collected after the containment project.
CONCLUSIONS
Although the containment project had been implemented in this area, the expansion of artemisinin-resistant parasites did not decline. In addition, reduced sensitivity of the partner drugs of ACT including MQ and PPQ were identified.
Topics: Antimalarials; Artemisinins; Drug Resistance; Genotype; Phenotype; Plasmodium falciparum; Thailand
PubMed: 29764451
DOI: 10.1186/s12936-018-2347-9 -
MBio Apr 2019The global spread of chloroquine resistance transporter (PfCRT) variant haplotypes earlier caused the widespread loss of chloroquine (CQ) efficacy. In Asia, novel PfCRT...
The global spread of chloroquine resistance transporter (PfCRT) variant haplotypes earlier caused the widespread loss of chloroquine (CQ) efficacy. In Asia, novel PfCRT mutations that emerged on the Dd2 allelic background have recently been implicated in high-level resistance to piperaquine, and N326S and I356T have been associated with genetic backgrounds in which resistance emerged to artemisinin derivatives. By analyzing large-scale genome sequencing data, we report that the predominant Asian CQ-resistant Dd2 haplotype is undetectable in Africa. Instead, the GB4 and previously unexplored Cam783 haplotypes predominate, along with wild-type, drug-sensitive PfCRT that has reemerged as the major haplotype. To interrogate how these alleles impact drug susceptibility, we generated -modified isogenic parasite lines spanning the mutational interval between GB4 and Dd2, which includes Cam783 and involves amino acid substitutions at residues 326 and 356. Relative to Dd2, the GB4 and Cam783 alleles were observed to mediate lower degrees of resistance to CQ and the first-line drug amodiaquine, while resulting in higher growth rates. These findings suggest that differences in growth rates, a surrogate of parasite fitness, influence selection in the context of African infections that are frequently characterized by high transmission rates, mixed infections, increased immunity, and less recourse to treatment. We also observe that the Asian Dd2 allele affords partial protection against piperaquine yet does not directly impact artemisinin efficacy. Our results can help inform the regional recommendations of antimalarials, whose activity is influenced by and, in certain cases, enhanced against select PfCRT variant haplotypes. Our study defines the allelic distribution of , an important mediator of multidrug resistance in , in Africa and Asia. We leveraged whole-genome sequence analysis and gene editing to demonstrate how current drug combinations can select different allelic variants of this gene and shape region-specific parasite population structures. We document the ability of PfCRT mutations to modulate parasite susceptibility to current antimalarials in dissimilar, allele-specific ways. This study underscores the importance of actively monitoring genotypes to identify emerging patterns of multidrug resistance and help guide region-specific treatment options.
Topics: Africa; Asia; Drug Resistance, Multiple; Gene Frequency; Genetic Fitness; Genetics, Population; Genotype; Malaria, Falciparum; Membrane Transport Proteins; Mutant Proteins; Plasmodium falciparum; Protozoan Proteins
PubMed: 31040246
DOI: 10.1128/mBio.02731-18 -
Journal of Vector Borne Diseases 2017Malaria is a life-threatening disease caused by Plasmodium parasites. The life-cycle of Plasmodium species involves several stages both in mosquito and the vertebrate...
BACKGROUND & OBJECTIVES
Malaria is a life-threatening disease caused by Plasmodium parasites. The life-cycle of Plasmodium species involves several stages both in mosquito and the vertebrate host. In the erythrocytic stage, Plasmodium resides inside the red blood cells (RBCs), where it meets most of its nutritional requirement by degrad- ing host's haemoglobin. L-arginine is required for growth and division of cells. The present study was aimed to demonstrate the effect of supplementation of different concentrations of L-arginine and L-citrulline on the growth of parasite, and effect of the culture supernatant on the host's peripheral blood mononuclear cells (PBMCs).
METHODS
To examine the effect of supplementation of L-arginine and L-citrulline, Plasmodium falciparum (3D7 strain) was cultured in RPMI 1640, L-arginine deficient RPMI 1640, and in different concentrations of L-arginine, and L-citrulline supplemented in arginine deficient RPMI 1640 medium. To have a holistic view of in vivo cell activation, the PBMCs isolated from healthy human host were cultured in the supernatant collected from P. falciparum culture.
RESULTS
Growth of the parasite was greatly enhanced in L-arginine supplemented media and was found to be concentration dependent. However, parasite growth was compromised in L-citrulline supplemented and L-arginine deficient media. The supernatant collected from L-arginine supplemented parasite media (sArg) showed increased FOXP3 and interleukin-10 (IL-10) expression as compared to the supernatant collected from L-citrulline supple- mented parasite media (sCit).
INTERPRETATION & CONCLUSION
The in vitro culture results showed, decreased parasite growth, and decreased expression of programmed cell death-1 (PD-1) (a coinhibitory molecule) and IL-10 in the L-citrulline supplemented media as compared to L-arginine supplemented media. Hence, it was concluded that L-citrulline supplementation would be a better alternative than L-arginine to inhibit the parasite growth.
Topics: Arginine; Cells, Cultured; Citrulline; Culture Media, Conditioned; Humans; Leukocytes, Mononuclear; Plasmodium falciparum
PubMed: 28748834
DOI: No ID Found -
PloS One 2016The development of resistance to insecticides by the vector of malaria and the increasingly faster appearance of resistance to antimalarial drugs by the parasite can...
The development of resistance to insecticides by the vector of malaria and the increasingly faster appearance of resistance to antimalarial drugs by the parasite can dangerously hamper efforts to control and eradicate the disease. Alternative ways to treat this disease are urgently needed. Here we evaluate the in vitro effect of direct current (DC) capacitive coupling electrical stimulation on the biology and viability of Plasmodium falciparum. We designed a system that exposes infected erythrocytes to different capacitively coupled electric fields in order to evaluate their effect on P. falciparum. The effect on growth of the parasite, replication of DNA, mitochondrial membrane potential and level of reactive oxygen species after exposure to electric fields demonstrate that the parasite is biologically able to respond to stimuli from DC electric fields involving calcium signaling pathways.
Topics: Calcium Signaling; DNA Replication; Electric Stimulation; Electricity; Flow Cytometry; Membrane Potential, Mitochondrial; Plasmodium falciparum; Reactive Oxygen Species
PubMed: 27537497
DOI: 10.1371/journal.pone.0161207