scholarly journals The NTP generating activity of pyruvate kinase II is critical for apicoplast maintenance in Plasmodium falciparum

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Russell P Swift ◽  
Krithika Rajaram ◽  
Cyrianne Keutcha ◽  
Hans B Liu ◽  
Bobby Kwan ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Pyruvate Kinase ◽  
Reducing Power ◽  
Enzymatic Characterization ◽  
Parasite Survival ◽  
Nucleotide Triphosphates ◽  
Bypass Line ◽  
Stage Parasite ◽  
Blood Stage Parasite

The apicoplast of Plasmodium falciparum parasites is believed to rely on the import of three-carbon phosphate compounds for use in organelle anabolic pathways, in addition to the generation of energy and reducing power within the organelle. We generated a series of genetic deletions in an apicoplast metabolic bypass line to determine which genes involved in apicoplast carbon metabolism are required for blood-stage parasite survival and organelle maintenance. We found that pyruvate kinase II (PyrKII) is essential for organelle maintenance, but that production of pyruvate by PyrKII is not responsible for this phenomenon. Enzymatic characterization of PyrKII revealed activity against all NDPs and dNDPs tested, suggesting that it may be capable of generating a broad range of nucleotide triphosphates. Conditional mislocalization of PyrKII resulted in decreased transcript levels within the apicoplast that preceded organelle disruption, suggesting that PyrKII is required for organelle maintenance due to its role in nucleotide triphosphate generation.

scholarly journals Genetic and enzymatic characterization of 3-O-sulfotransferase SNPs associated with Plasmodium falciparum parasitaemia

Glycobiology ◽  
2018 ◽  
Vol 28 (7) ◽  
pp. 534-541 ◽  
Author(s):  
Ngoc Thy Nguyen ◽  
Romain R Vivès ◽  
Magali Torres ◽  
Vincent Delauzun ◽  
Els Saesen ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Enzymatic Characterization

scholarly journals Distinct patterns of blood-stage parasite antigens detected by plasma IgG subclasses from individuals with different level of exposure to Plasmodium falciparum infections

2010 ◽  
Vol 9 (1) ◽  
pp. 296 ◽  
Author(s):  
Cathrine Olesen ◽  
Karima Brahimi ◽  
Brian Vandahl ◽  
Susana Lousada-Dietrich ◽  
Prajakta S Jogdand ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Igg Subclasses ◽  
Blood Stage ◽  
Stage Parasite ◽  
Blood Stage Parasite

scholarly journals Chemoprophylaxis Vaccination: Phase I Study to Explore Stage-specific Immunity to Plasmodium falciparum in US Adults

2019 ◽  
Vol 71 (6) ◽  
pp. 1481-1490
Author(s):  
Sara A Healy ◽  
Sean C Murphy ◽  
Jen C C Hume ◽  
Lisa Shelton ◽  
Steve Kuntz ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Phase I ◽  
Malaria Infection ◽  
Blood Smear ◽  
Blood Stage ◽  
Controlled Human Malaria Infection ◽  
Smear Negative ◽  
Parasite Exposure ◽  
Stage Parasite ◽  
Blood Stage Parasite

Abstract Background Chemoprophylaxis vaccination with sporozoites (CVac) with chloroquine induces protection against a homologous Plasmodium falciparum sporozoite (PfSPZ) challenge, but whether blood-stage parasite exposure is required for protection remains unclear. Chloroquine suppresses and clears blood-stage parasitemia, while other antimalarial drugs, such as primaquine, act against liver-stage parasites. Here, we evaluated CVac regimens using primaquine and/or chloroquine as the partner drug to discern whether blood-stage parasite exposure impacts protection against homologous controlled human malaria infection. Methods In a Phase I, randomized, partial double-blind, placebo-controlled study of 36 malaria-naive adults, all CVac subjects received chloroquine prophylaxis and bites from 12–15 P. falciparum–infected mosquitoes (CVac-chloroquine arm) at 3 monthly iterations, and some received postexposure primaquine (CVac-primaquine/chloroquine arm). Drug control subjects received primaquine, chloroquine, and uninfected mosquito bites. After a chloroquine washout, subjects, including treatment-naive infectivity controls, underwent homologous, PfSPZ controlled human malaria infection and were monitored for parasitemia for 21 days. Results No serious adverse events occurred. During CVac, all but 1 subject in the study remained blood-smear negative, while only 1 subject (primaquine/chloroquine arm) remained polymerase chain reaction–negative. Upon challenge, compared to infectivity controls, 3/3 chloroquine arm subjects displayed delayed patent parasitemia (P = .01) but not sterile protection, while 3/11 primaquine/chloroquine subjects remained blood-smear negative. Conclusions CVac-primaquine/chloroquine is safe and induces sterile immunity to P. falciparum in some recipients, but a single 45 mg dose of primaquine postexposure does not completely prevent blood-stage parasitemia. Unlike previous studies, CVac-chloroquine did not produce sterile immunity. Clinical Trials Registration NCT01500980.

scholarly journals Identification of the asymptomatic Plasmodium falciparum and Plasmodium vivax gametocyte reservoir under different transmission intensities

2021 ◽  
Vol 15 (8) ◽  
pp. e0009672
Author(s):  
Cristian Koepfli ◽  
Wang Nguitragool ◽  
Anne Cristine Gomes de Almeida ◽  
Andrea Kuehn ◽  
Andreea Waltmann ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Light Microscopy ◽  
Papua New Guinea ◽  
Parasite Density ◽  
Solomon Islands ◽  
Age Groups ◽  
Blood Stage ◽  
Cross Sectional ◽  
Stage Parasite ◽  
Blood Stage Parasite

Background Understanding epidemiological variables affecting gametocyte carriage and density is essential to design interventions that most effectively reduce malaria human-to-mosquito transmission. Methodology/Principal findings Plasmodium falciparum and P. vivax parasites and gametocytes were quantified by qPCR and RT-qPCR assays using the same methodologies in 5 cross-sectional surveys involving 16,493 individuals in Brazil, Thailand, Papua New Guinea, and Solomon Islands. The proportion of infections with detectable gametocytes per survey ranged from 44–94% for P. falciparum and from 23–72% for P. vivax. Blood-stage parasite density was the most important predictor of the probability to detect gametocytes. In moderate transmission settings (prevalence by qPCR>5%), parasite density decreased with age and the majority of gametocyte carriers were children. In low transmission settings (prevalence<5%), >65% of gametocyte carriers were adults. Per survey, 37–100% of all individuals positive for gametocytes by RT-qPCR were positive by light microscopy for asexual stages or gametocytes (overall: P. falciparum 178/348, P. vivax 235/398). Conclusions/Significance Interventions to reduce human-to-mosquito malaria transmission in moderate-high endemicity settings will have the greatest impact when children are targeted. In contrast, all age groups need to be included in control activities in low endemicity settings to achieve elimination. Detection of infections by light microscopy is a valuable tool to identify asymptomatic blood stage infections that likely contribute most to ongoing transmission at the time of sampling.

scholarly journals Evidence for a Common Role for the Serine-Type Plasmodium falciparum Serine Repeat Antigen Proteases: Implications for Vaccine and Drug Design

2007 ◽  
Vol 75 (12) ◽  
pp. 5565-5574 ◽  
Author(s):  
Joanne E. McCoubrie ◽  
Susanne K. Miller ◽  
Tobias Sargeant ◽  
Robert T. Good ◽  
Anthony N. Hodder ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Functional Redundancy ◽  
Blood Stage ◽  
Parasite Development ◽  
Serine Residue ◽  
Human Malaria Parasite ◽  
Knock Out ◽  
Genetic Deletion ◽  
Stage Parasite ◽  
Blood Stage Parasite

ABSTRACT Serine repeat antigens (SERAs) are a family of secreted “cysteine-like” proteases of Plasmodium parasites. Several SERAs possess an atypical active-site serine residue in place of the canonical cysteine. The human malaria parasite Plasmodium falciparum possesses six “serine-type” (SERA1 to SERA5 and SERA9) and three “cysteine-type” (SERA6 to SERA8) SERAs. Here, we investigate the importance of the serine-type SERAs to blood-stage parasite development and examine the extent of functional redundancy among this group. We attempted to knock out the four P. falciparum serine-type SERA genes that have not been disrupted previously. SERA1, SERA4, and SERA9 knockout lines were generated, while only SERA5, the most strongly expressed member of the SERA family, remained refractory to genetic deletion. Interestingly, we discovered that while SERA4-null parasites completed the blood-stage cycle normally, they exhibited a twofold increase in the level of SERA5 mRNA. The inability to disrupt SERA5 and the apparent compensatory increase in SERA5 expression in response to the deletion of SERA4 provides evidence for an important blood-stage function for the serine-type SERAs and supports the notion of functional redundancy among this group. Such redundancy is consistent with our phylogenetic analysis, which reveals a monophyletic grouping of the serine-type SERAs across the genus Plasmodium and a predominance of postspeciation expansion. While SERA5 is to some extent further validated as a target for vaccine and drug development, our data suggest that the expression level of other serine-type SERAs is the only barrier to escape from anti-SERA5-specific interventions.

scholarly journals Cholesterol bound Plasmodium falciparum co-chaperone ‘PFA0660w’ complexes with major virulence factor ‘PfEMP1’ via chaperone ‘PfHsp70-x’

2018 ◽  
Author(s):  
Ankita Behl ◽  
Vikash Kumar ◽  
Anjali Bisht ◽  
Jiban J. Panda ◽  
Rachna Hora ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Direct Interaction ◽  
Lipid Binding ◽  
The Novel ◽  
The Past ◽  
Biochemical Assays ◽  
Erythrocyte Surface ◽  
Parasite Survival

AbstractLethality of Plasmodium falciparum (Pf) caused malaria results from ‘cytoadherence’, which is effected by exported Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family. Several exported Pf proteins (exportome) including chaperones alongside cholesterol rich microdomains are crucial for PfEMP1 translocation to infected erythrocyte surface. An exported Hsp40 (heat shock protein 40) ‘PFA0660w’ functions as a co-chaperone of ‘PfHsp70-x’, and these co-localize to specialized intracellular mobile structures termed J-dots. Our studies attempt to understand the function of PFA0660w-PfHsp70-x chaperone pair using recombinant proteins. Biochemical assays reveal that N and C-terminal domains of PFA0660w and PfHsp70-x respectively are critical for their activity. We show the novel direct interaction of PfHsp70-x with the cytoplasmic tail of PfEMP1, and binding of PFA0660w with cholesterol. PFA0660w operates both as a chaperone and lipid binding molecule via its separate substrate and cholesterol binding sites. PfHsp70-x binds cholesterol linked PFA0660w and PfEMP1 simultaneously in vitro to form a complex. Collectively, our results and the past literature support the hypothesis that PFA0660w-PfHsp70-x chaperone pair assists PfEMP1 transport across the host erythrocyte through cholesterol containing ‘J-dots’. Since PFA0660w seems essential for parasite survival, characterization of its interaction with PfHsp70-x and J-dots may form the basis for development of future antimalarials.

scholarly journals Sulfur Mobilization for Fe-S Cluster Assembly by the Essential SUF Pathway in the Plasmodium falciparum Apicoplast and Its Inhibition

2014 ◽  
Vol 58 (6) ◽  
pp. 3389-3398 ◽  
Author(s):  
Manish Charan ◽  
Nidhi Singh ◽  
Bijay Kumar ◽  
Kumkum Srivastava ◽  
Mohammad Imran Siddiqi ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Pyridoxal Phosphate ◽  
Inhibitory Concentration ◽  
Cluster Assembly ◽  
Cysteine Desulfurase ◽  
Content Type ◽  
Biochemical Investigation ◽  
Parasite Survival

ABSTRACTThe plastid of the malaria parasite, the apicoplast, is essential for parasite survival. It houses several pathways of bacterial origin that are considered attractive sites for drug intervention. Among these is the sulfur mobilization (SUF) pathway of Fe-S cluster biogenesis. Although the SUF pathway is essential for apicoplast maintenance and parasite survival, there has been limited biochemical investigation of its components and inhibitors ofPlasmodiumSUFs have not been identified. We report the characterization of two proteins,Plasmodium falciparumSufS (PfSufS) andPfSufE, that mobilize sulfur in the first step of Fe-S cluster assembly and confirm their exclusive localization to the apicoplast. The cysteine desulfurase activity ofPfSufS is greatly enhanced byPfSufE, and thePfSufS-PfSufE complex is detectedin vivo. Structural modeling of the complex reveals proximal positioning of conserved cysteine residues of the two proteins that would allow sulfide transfer from the PLP (pyridoxal phosphate) cofactor-bound active site ofPfSufS. Sulfide release from thel-cysteine substrate catalyzed byPfSufS is inhibited by the PLP inhibitord-cycloserine, which forms an adduct withPfSufS-bound PLP.d-Cycloserine is also inimical to parasite growth, with a 50% inhibitory concentration close to that reported forMycobacterium tuberculosis, against which the drug is in clinical use. Our results establish the function of two proteins that mediate sulfur mobilization, the first step in the apicoplast SUF pathway, and provide a rationale for drug design based on inactivation of the PLP cofactor ofPfSufS.

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