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International Journal of Molecular... May 2022The sole currently approved malaria vaccine targets the circumsporozoite protein-the protein that densely coats the surface of sporozoites, the parasite stage deposited...
The sole currently approved malaria vaccine targets the circumsporozoite protein-the protein that densely coats the surface of sporozoites, the parasite stage deposited in the skin of the mammalian host by infected mosquitoes. However, this vaccine only confers moderate protection against clinical diseases in children, impelling a continuous search for novel candidates. In this work, we studied the importance of the membrane-associated erythrocyte binding-like protein (MAEBL) for infection by sporozoites. Using transgenic parasites and live imaging in mice, we show that the absence of MAEBL reduces hemolymph sporozoite infectivity to mice. Moreover, we found that knockout (-) sporozoites display reduced adhesion, including to cultured hepatocytes, which could contribute to the defects in multiple biological processes, such as in gliding motility, hepatocyte wounding, and invasion. The - defective phenotypes in mosquito salivary gland and liver infection were reverted by genetic complementation. Using a parasite line expressing a C-terminal myc-tagged MAEBL, we found that MAEBL levels peak in midgut and hemolymph parasites but drop after sporozoite entry into the salivary glands, where the labeling was found to be heterogeneous among sporozoites. MAEBL was found associated, not only with micronemes, but also with the surface of mature sporozoites. Overall, our data provide further insight into the role of MAEBL in sporozoite infectivity and may contribute to the design of future immune interventions.
Topics: Animals; Culicidae; Erythrocytes; Membrane Proteins; Mice; Plasmodium berghei; Protozoan Proteins; Receptors, Cell Surface; Sporozoites
PubMed: 35628522
DOI: 10.3390/ijms23105711 -
Cell Host & Microbe Sep 2023Malaria remains one of the most devastating infectious diseases. Reverse genetic screens offer a powerful approach to identify genes and molecular processes governing...
Malaria remains one of the most devastating infectious diseases. Reverse genetic screens offer a powerful approach to identify genes and molecular processes governing malaria parasite biology. However, the complex regulation of gene expression and genotype-phenotype associations in the mosquito vector, along with sexual reproduction, have hindered the development of screens in this critical part of the parasite life cycle. To address this, we developed a genetic approach in the rodent parasite Plasmodium berghei that, in combination with barcode sequencing, circumvents the fertilization roadblock and enables screening for gametocyte-expressed genes required for parasite infection of the mosquito Anopheles coluzzii. Our results confirm previous findings, validating our approach for scaling up, and identify genes necessary for mosquito midgut infection, oocyst development, and salivary gland infection. These findings can aid efforts to study malaria transmission biology and to develop interventions for controlling disease transmission.
Topics: Animals; Sporozoites; Mosquito Vectors; Plasmodium berghei; Anopheles
PubMed: 37708854
DOI: 10.1016/j.chom.2023.08.010 -
Parasitology International Dec 2022Rodent malaria parasites have been widely used in all aspects of malaria research to study parasite development within rodent and insect hosts, drug resistance, disease... (Review)
Review
Rodent malaria parasites have been widely used in all aspects of malaria research to study parasite development within rodent and insect hosts, drug resistance, disease pathogenesis, host immune response, and vaccine efficacy. Rodent malaria parasites were isolated from African thicket rats and initially characterized by scientists at the University of Edinburgh, UK, particularly by Drs. Richard Carter, David Walliker, and colleagues. Through their efforts and elegant work, many rodent malaria parasite species, subspecies, and strains are now available. Because of the ease of maintaining these parasites in laboratory mice, genetic crosses can be performed to map the parasite and host genes contributing to parasite growth and disease severity. Recombinant DNA technologies are now available to manipulate the parasite genomes and to study gene functions efficiently. In this chapter, we provide a brief history of the isolation and species identification of rodent malaria parasites. We also discuss some recent studies to further characterize the different developing stages of the parasites including parasite genomes and chromosomes. Although there are differences between rodent and human malaria parasite infections, the knowledge gained from studies of rodent malaria parasites has contributed greatly to our understanding of and the fight against human malaria.
Topics: Animals; Humans; Malaria; Mice; Parasites; Plasmodium; Plasmodium berghei; Plasmodium yoelii; Rats; Rodentia
PubMed: 35926694
DOI: 10.1016/j.parint.2022.102636 -
European Journal of Medicinal Chemistry Oct 2023A novel family of 4-aminoacridine derivatives was obtained by linking this heteroaromatic core to different trans-cinnamic acids. The 4-(N-cinnamoylbutyl)aminoacridines...
A novel family of 4-aminoacridine derivatives was obtained by linking this heteroaromatic core to different trans-cinnamic acids. The 4-(N-cinnamoylbutyl)aminoacridines obtained exhibited in vitro activity in the low- or sub-micromolar range against (i) hepatic stages of Plasmodium berghei, (ii) erythrocytic forms of Plasmodium falciparum, and (iii) early and mature gametocytes of Plasmodium falciparum. The most active compound, having a meta-fluorocinnamoyl group linked to the acridine core, was 20- and 120-fold more potent, respectively, against the hepatic and gametocyte stages of Plasmodium infection than the reference drug, primaquine. Moreover, no cytotoxicity towards mammalian and red blood cells at the concentrations tested was observed for any of the compounds under investigation. These novel conjugates represent promising leads for the development of new multi-target antiplasmodials.
Topics: Animals; Aminacrine; Aminoacridines; Antimalarials; Mammals; Plasmodium berghei; Plasmodium falciparum; Primaquine
PubMed: 37390511
DOI: 10.1016/j.ejmech.2023.115575 -
International Journal For Parasitology.... Apr 2017The incidence and global distribution of chloroquine resistant (CR) Plasmodium vivax infection has increased since emerging in 1989. The mechanism of resistance in CR...
The incidence and global distribution of chloroquine resistant (CR) Plasmodium vivax infection has increased since emerging in 1989. The mechanism of resistance in CR P. vivax has not been defined. The resistance likely relates to the formation and disposition of hemozoin as chloroquine's primary mechanism of action involves disruption of hemozoin formation. CR P. berghei strains, like CR P. vivax strains, are confined to reticulocyte host cells and reportedly they do not accumulate appreciable intraerythrocytic hemozoin. Reports comparing hemozoin production between P. vivax strains and CR to chloroquine sensitive (CS) P. berghei are absent. Here we compare in vivo patterns of hemozoin formation and distribution in blood, spleen and liver tissue of male Swiss mice infected with CS or CR P. berghei not treated with chloroquine and CR P. berghei also treated with chloroquine. Light microscopy, laser desorption mass spectrometry and a colorimetric hemozoin assay detect trace hemozoin in the blood of CR P. berghei infected mice but significant hemozoin accumulation in liver and spleen tissue. Field emission in lens scanning electron microscopy reveals CR P. berghei hemozoin crystals are morphologically smaller but similar to those formed by CS parasites. CR P. berghei produces approximately five-fold less total hemozoin than CS strain. Lipid analysis of CS and CR P. berghei sucrose gradient purified bloodstage hemozoin indicates a similar lipid environment around the isolated hemozoin, predominately monopalmitic glycerol and monostearic glycerol. In contrast to CR and CS P. berghei, colorimetric hemozoin analysis of P. vivax strains indicates similar amounts of hemozoin are produced despite differing chloroquine sensitivities. These results suggest CR P. berghei forms significant hemozoin which accumulates in liver and spleen tissues and that the P. vivax chloroquine resistance mechanism differs from P. berghei.
Topics: Animals; Antimalarials; Chloroquine; Drug Resistance; Hemeproteins; Liver; Malaria; Malaria, Vivax; Mice; Parasitemia; Plasmodium berghei; Plasmodium falciparum; Plasmodium vivax; Spleen
PubMed: 28279945
DOI: 10.1016/j.ijpddr.2017.02.001 -
Nature Communications Feb 2017In search of antiparasitic agents, we here identify arylmethylamino steroids as potent compounds and characterize more than 60 derivatives. The lead compound 1o is fast...
In search of antiparasitic agents, we here identify arylmethylamino steroids as potent compounds and characterize more than 60 derivatives. The lead compound 1o is fast acting and highly active against intraerythrocytic stages of chloroquine-sensitive and resistant Plasmodium falciparum parasites (IC 1-5 nM) as well as against gametocytes. In P. berghei-infected mice, oral administration of 1o drastically reduces parasitaemia and cures the animals. Furthermore, 1o efficiently blocks parasite transmission from mice to mosquitoes. The steroid compounds show low cytotoxicity in mammalian cells and do not induce acute toxicity symptoms in mice. Moreover, 1o has a remarkable activity against the blood-feeding trematode parasite Schistosoma mansoni. The steroid and the hydroxyarylmethylamino moieties are essential for antimalarial activity supporting a chelate-based quinone methide mechanism involving metal or haem bioactivation. This study identifies chemical scaffolds that are rapidly internalized into blood-feeding parasites.
Topics: Amines; Animals; Anopheles; Anti-Infective Agents; Antiparasitic Agents; Cell Death; Cell Proliferation; Female; Germ Cells; Inhibitory Concentration 50; Life Cycle Stages; Malaria; Mice; Models, Biological; Parasites; Plasmodium berghei; Plasmodium falciparum; Schistosoma mansoni; Steroids; Toxicity Tests, Acute
PubMed: 28211535
DOI: 10.1038/ncomms14478 -
EMBO Reports Jul 2023Eukaryotic cell adhesion and migration rely on surface adhesins connecting extracellular ligands to the intracellular actin cytoskeleton. Plasmodium sporozoites are...
Eukaryotic cell adhesion and migration rely on surface adhesins connecting extracellular ligands to the intracellular actin cytoskeleton. Plasmodium sporozoites are transmitted by mosquitoes and rely on adhesion and gliding motility to colonize the salivary glands and to reach the liver after transmission. During gliding, the essential sporozoite adhesin TRAP engages actin filaments in the cytoplasm of the parasite, while binding ligands on the substrate through its inserted (I) domain. Crystal structures of TRAP from different Plasmodium species reveal the I domain in closed and open conformations. Here, we probe the importance of these two conformational states by generating parasites expressing versions of TRAP with the I domain stabilized in either the open or closed state with disulfide bonds. Strikingly, both mutations impact sporozoite gliding, mosquito salivary gland entry, and transmission. Absence of gliding in sporozoites expressing the open TRAP I domain can be partially rescued by adding a reducing agent. This suggests that dynamic conformational change is required for ligand binding, gliding motility, and organ invasion and hence sporozoite transmission from mosquito to mammal.
Topics: Animals; Sporozoites; Ligands; Plasmodium; Culicidae; Liver; Protozoan Proteins; Plasmodium berghei; Mammals
PubMed: 37306042
DOI: 10.15252/embr.202357064 -
Proceedings of the National Academy of... Oct 2023Malaria remains a devastating disease and, with current measures failing to control its transmission, there is a need for novel interventions. A family of proteins that...
Malaria remains a devastating disease and, with current measures failing to control its transmission, there is a need for novel interventions. A family of proteins that have long been pursued as potential intervention targets are aquaporins, which are channels facilitating the movement of water and other solutes across membranes. We identify an aquaporin in malaria parasites and demonstrate that it is important for completion of development in the mosquito vector. Disruption of AQP2 in the human parasite and the rodent parasite blocks sporozoite production inside oocysts established on mosquito midguts, greatly limiting parasite infection of salivary glands and transmission to a new host. In vivo epitope tagging of AQP2 in , combined with immunofluorescence assays, reveals that the protein is localized in vesicle-like organelles found in the cytoplasm of gametocytes, ookinetes, and sporozoites. The number of these organelles varies between individual parasites and lifecycle stages suggesting that they are likely part of a dynamic endomembrane system. Phylogenetic analysis confirms that AQP2 is unique to malaria and closely related parasites and most closely resembles intracellular aquaporins. Structure prediction analyses identify several unusual features, including a large accessory extracellular loop and an arginine-to-phenylalanine substitution in the selectivity filter principally determining pore function, a unique feature among known aquaporins. This in conjunction with the importance of AQP2 for malaria transmission suggests that AQP2 may be a fruitful target of antimalarial interventions.
Topics: Animals; Aquaporin 2; Malaria; Mosquito Vectors; Phylogeny; Plasmodium berghei; Protozoan Proteins; Sporozoites
PubMed: 37883438
DOI: 10.1073/pnas.2304339120 -
Frontiers in Cellular and Infection... 2022Malaria-associated acute respiratory distress syndrome (MA-ARDS) is increasingly gaining recognition as a severe malaria complication because of poor prognostic... (Review)
Review
Malaria-associated acute respiratory distress syndrome (MA-ARDS) is increasingly gaining recognition as a severe malaria complication because of poor prognostic outcomes, high lethality rate, and limited therapeutic interventions. Unfortunately, invasive clinical studies are challenging to conduct and yields insufficient mechanistic insights. These limitations have led to the development of suitable MA-ARDS experimental mouse models. In patients and mice, MA-ARDS is characterized by edematous lung, along with marked infiltration of inflammatory cells and damage of the alveolar-capillary barriers. Although, the pathogenic pathways have yet to be fully understood, the use of different experimental mouse models is fundamental in the identification of mediators of pulmonary vascular damage. In this review, we discuss the current knowledge on endothelial activation, leukocyte recruitment, leukocyte induced-endothelial dysfunction, and other important findings, to better understand the pathogenesis pathways leading to endothelial pulmonary barrier lesions and increased vascular permeability. We also discuss how the advances in imaging techniques can contribute to a better understanding of the lung lesions induced during MA-ARDS, and how it could aid to monitor MA-ARDS severity.
Topics: Animals; Disease Models, Animal; Humans; Lung; Malaria; Mice; Mice, Inbred C57BL; Plasmodium berghei; Respiratory Distress Syndrome
PubMed: 35677654
DOI: 10.3389/fcimb.2022.899581 -
The FEBS Journal Jan 2021The Apicomplexa phylum groups important human and animal pathogens that cause severe diseases, encompassing malaria, toxoplasmosis, and cryptosporidiosis. In common with... (Review)
Review
The Apicomplexa phylum groups important human and animal pathogens that cause severe diseases, encompassing malaria, toxoplasmosis, and cryptosporidiosis. In common with most organisms, apicomplexans rely on heme as cofactor for several enzymes, including cytochromes of the electron transport chain. This heme derives from de novo synthesis and/or the development of uptake mechanisms to scavenge heme from their host. Recent studies have revealed that heme synthesis is essential for Toxoplasma gondii tachyzoites, as well as for the mosquito and liver stages of Plasmodium spp. In contrast, the erythrocytic stages of the malaria parasites rely on scavenging heme from the host red blood cell. The unusual heme synthesis pathway in Apicomplexa spans three cellular compartments and comprises enzymes of distinct ancestral origin, providing promising drug targets. Remarkably given the requirement for heme, T. gondii can tolerate the loss of several heme synthesis enzymes at a high fitness cost, while the ferrochelatase is essential for survival. These findings indicate that T. gondii is capable of salvaging heme precursors from its host. Furthermore, heme is implicated in the activation of the key antimalarial drug artemisinin. Recent findings established that a reduction in heme availability corresponds to decreased sensitivity to artemisinin in T. gondii and Plasmodium falciparum, providing insights into the possible development of combination therapies to tackle apicomplexan parasites. This review describes the microeconomics of heme in Apicomplexa, from supply, either from de novo synthesis or scavenging, to demand by metabolic pathways, including the electron transport chain.
Topics: Animals; Anti-Infective Agents; Artemisinins; Cryptosporidium; Cytochromes; Erythrocytes; Ferrochelatase; Gene Expression; Heme; Host-Pathogen Interactions; Humans; Life Cycle Stages; Metabolic Networks and Pathways; Plasmodium berghei; Plasmodium falciparum; Protozoan Proteins; Toxoplasma
PubMed: 32530125
DOI: 10.1111/febs.15445