Plasmodium falciparum increased time in circulation underlies persistent asymptomatic infection in the dry season
Ontology highlight
ABSTRACT:
ORGANISM(S): Human Homo Sapiens
TISSUE(S): Blood
DISEASE(S): Malaria
SUBMITTER: 
Manuel Llinas
PROVIDER: ST001384 | MetabolomicsWorkbench | Mon May 25 00:00:00 BST 2020
REPOSITORIES: MetabolomicsWorkbench
Similar Datasets
Project description:The dry season is a major challenge for Plasmodium falciparum parasites in many malaria endemic regions, where water availability limits mosquitoes to only part of the year. How P. falciparum bridges two transmission seasons months apart, without being cleared by the host or compromising host survival is poorly understood. Here we show that low levels of P. falciparum parasites persist in the blood of asymptomatic Malian individuals during the 5- to 6-month dry season, rarely causing symptoms and minimally affecting the host immune response. Parasites isolated during the dry season are transcriptionally distinct from those of subjects with febrile malaria in the transmission season, reflecting longer circulation within each replicative cycle, of parasitized erythrocytes without adhering to the vascular endothelium. Low parasite levels during the dry season are not due to impaired replication, but rather increased efficiency of splenic clearance of longer-circulating infected erythrocytes. We propose that P. falciparum virulence in areas of seasonal malaria transmission is regulated so that the parasite decreases its endothelial binding capacity, allowing increased splenic clearance and enabling several months of subclinical parasite persistence.
2020-08-20 | GSE148125 | GEO
Project description:Cerebral malaria is the most deadly manifestation of infection with Plasmodium falciparum. The pathology of cerebral malaria is characterised by the accumulation of infected erythrocytes in the microvasculature of the brain, due to parasite adhesins on the surface of infected erythrocytes binding to human receptors on microvascular endothelial cells. The parasite and host molecules involved in this interaction are unknown. We used the Human Brain Endothelial Cell line HBEC-5i to identify the malaria parasite ligands responsible for binding to human brain endothelial cells. Three P. falciparum strains (HB3, 3D7 and IT/FCR3) were selected for binding to HBEC5i and the whole transcriptome of selected and unselected parasites was analysed using a variant surface antigen-supplemented microarray chip. After selection, the only highly upregulated genes were a subset of group A-like var genes (HB3var3, 3D7_PFD0020c, ITvar7 and ITvar19), that showed 11 to >100-fold higher transcription levels in selected parasites. These genes are highly diverse in sequence, but do however show strong similarities in PfEMP1 architecture. Antibodies raised to the HB3var3 variant recognized the surface of infected erythrocytes and abolished the binding of infected erythrocytes to brain endothelial cells. The subset of Group A PfEMP1 variants identified here provides a new target for interventions to treat or prevent cerebral malaria.
2011-11-01 | GSE32211 | GEO
Project description:Cerebral malaria is the most deadly manifestation of infection with Plasmodium falciparum. The pathology of cerebral malaria is characterised by the accumulation of infected erythrocytes in the microvasculature of the brain, due to parasite adhesins on the surface of infected erythrocytes binding to human receptors on microvascular endothelial cells. The parasite and host molecules involved in this interaction are unknown. We used the Human Brain Endothelial Cell line HBEC-5i to identify the malaria parasite ligands responsible for binding to human brain endothelial cells. Three P. falciparum strains (HB3, 3D7 and IT/FCR3) were selected for binding to HBEC5i and the whole transcriptome of selected and unselected parasites was analysed using a variant surface antigen-supplemented microarray chip. After selection, the only highly upregulated genes were a subset of group A-like var genes (HB3var3, 3D7_PFD0020c, ITvar7 and ITvar19), that showed 11 to >100-fold higher transcription levels in selected parasites. These genes are highly diverse in sequence, but do however show strong similarities in PfEMP1 architecture. Antibodies raised to the HB3var3 variant recognized the surface of infected erythrocytes and abolished the binding of infected erythrocytes to brain endothelial cells. The subset of Group A PfEMP1 variants identified here provides a new target for interventions to treat or prevent cerebral malaria. Unselected Plasmodium falciparum parasites (Uns) only poorly cytoadhere to human brain endothelial cells (HBEC-5i). Plasmodium falciparum HB3, 3D7 and IT/FCR3 strains were selected for binding to HBEC-5i (HB3-HBEC1, HB3-HBEC2, HB3-HBEC-TNF, 3D7-HBEC and IT-HBEC). HBEC-selected and unselected cultures were tightly synchronised before a timecourse experiment was performed. 6 samples, named time points 1 to 6, were taken every 8 hours. 12μg of RNA from the unselected parasites (HB3-Uns, 3D7-Uns or IT-Uns) at each of the 6 time points was combined together to form the reference pool. The pool and 12μg of each individual time point sample from both selected and unselectedparasites were then used for cDNA synthesis. For HB3-HBEC1 (pilot experiment), each HB3-HBEC1 time point (pilot experiment) was hybridised directly with HB3-Uns1 time points. For microarray hybridizations, each cDNA sample was coupled to Cy5 (red dye) while Cy3 (green dye) was added to the pool. Cy5-labelled time point samples were mixed with the same amount of Cy3-labelled pool sample. The solution was loaded on a microarray slide and hybridized for 14–16 h.
2011-11-01 | E-GEOD-32211 | biostudies-arrayexpress
Project description:Background: Host iron deficiency is protective against severe malaria as the human malaria parasite Plasmodium falciparum depends on free iron from its host to proliferate. Due to the absence of transferrin, ferritin, ferroportin, and a functional heme oxygenase, the parasite’s essential pathways of iron acquisition, storage, export, and detoxification differ from those in humans and may thus be excellent targets for therapeutic development. However, the proteins involved in these processes in P. falciparum remain largely unknown. Experimental design: To identify iron-regulated mechanisms and putative iron transporters in the human malaria parasite Plasmodium falciparum 3D7, we carried out whole-transcriptome profiling using bulk RNA-sequencing. The parasites were cultured either using erythrocytes from a donors with high, medium (healthy) or low iron status (experiment 1); or with red blood cells from another healthy donor in the presence or absence of 0.7 µM hepcidin, a specific ferroportin inhibitor and iron-regulatory hormone (experiment 2). This concentration of hepcidin was reported to reduce binding of ferrous iron to ferroportin by 50% in vitro (39). Samples from three biological replicates each were harvested at the ring and trophozoite stage (6 – 9 and 26 – 29 hours post invasion, hpi) during the second intra-erythrocytic developmental cycle under the conditions specified.
2024-04-08 | E-MTAB-13411 | biostudies-arrayexpress
Project description:Central to the pathology of malaria disease are the repeated cycles of parasite invasion and destruction of human erythrocytes. In Plasmodium falciparum, the most virulent species causing malaria, erythrocyte invasion involves several specific receptor–ligand interactions that direct the pathway used to invade the host cell, with parasites varying in their dependency on these different pathways. Gene disruption of a key invasion ligand in the 3D7 parasite strain, the P. falciparum reticulocyte binding-like homolog 2b (PfRh2b), resulted in the parasite invading via a novel pathway. Here, we show results that suggest the molecular basis for this novel pathway is not due to a molecular switch but is instead mediated by the redeployment of machinery already present in the parent parasite but masked by the dominant role of PfRh2b. This would suggest that interactions directing invasion are organized hierarchically, where silencing of dominant invasion ligands reveal underlying alternative pathways. This provides wild parasites with the ability to adapt to immune-mediated selection or polymorphism in erythrocyte receptors and has implications for the use of invasion-related molecules in candidate vaccines. Keywords: genetic modification
2005-12-21 | GSE3877 | GEO
Project description:The asexual forms of the malaria parasite Plasmodium falciparum are uniquely adapted for chronic persistence in human red blood cells, continuously evading the immune system using an epigenetically regulated process. However, parasite survival on a population level also requires transmission of sexual parasite forms to subsequent human hosts. Here, we reveal that the essential nuclear gene, P. falciparum histone deacetylase 2 (PfHda2), silences specific subsets of genes involved in antigenic variation or conversion to sexual stages. Two parallel timecourses resulting in a total of 22 samples (11 wildtype, 11 PfHda2 knockdown) were hybridized against a Cy3-labeled reference pool of 3D7 mixed stage parasites on a two-color array.
2014-02-11 | E-GEOD-54806 | biostudies-arrayexpress
Project description:Malaria represents a major public health problem in Africa [1]. In the East African highlands, even in high-altitude areas previously considered too cold to support vector population and parasite transmission [2], frequent malaria epidemics have been reported since the 1980M-bM-^@M-^Ys [3]. Plasmodium falciparum infections have been detected in areas as high as 1,600-2,400m above sea level in Africa [4], albeit there is a marked gradient of parasite prevalence along the altitude transect [5-7]. Both the historical absence of malaria in the African highlands and now the intensive malaria control efforts put in place after the recent outbreaks have reduced malaria prevalence and incidence [8], rendering the East African highlands particularly prone to epidemic malaria due to the lack of the protective immunity, and causing significant human mortality amongst all age groups [9]. Therefore, malaria transmission monitoring in the East African highlands becomes a particularly important public health issue.Despite the overall lower immunity of the population in these historically malaria-free areas, the many successive outbreaks since the 1980M-bM-^@M-^Ys may have generated some level of immunity against P. falciparum amongst highland residents. The antibody response to Plasmodium is cumulative and long lasting, developing after repeated exposures to the parasite and persisting for months or years after infection was resolved. The antibody response to Plasmodium varies amongst individuals of different age groups (i.e. toddlers, children and adults) as well as amongst individuals of same age groups from areas of different parasite prevalence [10]. The repertoire of targets of the antibody response also expands after multiple infections, with the number of recognized antigens being correlated to parasite prevalence, age and immunity to clinical malaria [11,12]. Serological studies bring forth indirect evidence of human exposure to the parasite, and can reliably assess its prevalence and transmission intensity in an endemic area [13-15]. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasiteM-bM-^@M-^Ys antigens. The work we present here is an expansion of the study published by Badu et al. [16], in which the antibody response to the 19kDa fragment of merozoite surface protein 1 (MSP-119) was examined in populations from two endemic areas in the western Kenyan highlands. There, the tremendous variations of malaria transmission intensity in a small spatial scale are caused by substantial differences in altitude, topography and other environmental conditions [6,7,17,18]. We now expand our antibody profiling survey to include 854 P. falciparum proteins by using high-throughput proteomic microarray technology. Protein microarrays have been used to explore the humoral response to P. falciparum in other African settings [19-24], but this is the broadest characterization of the antibody responses of the population of western Kenyan highlands to date. In the present study we: i) determined the serological reactivity against P. falciparum (Pf) in subjects residing in a low transmission area, and detected hotspots of transmission; ii) examined the dynamics of antibody response to hundreds of Pf proteins generated by sera from toddlers, older children and adults residing in two endemic areas differing in transmission intensities, during two distinct malaria seasons, and compared the intensity, breadth and antigenic targets of these responses; and iii) identified candidate Pf antigenic markers that could provide more sensitive serological surveillance to detect micro-geographic variations in malaria transmission levels and differentiate hotspots of infection in low endemic areas. (references provided in the 'readme.txt') Antibody profiling was performed on sera from residents of western Kenyan highlands against Plasmodium falciparum. One-hundred and ten age-stratified serum samples collected during the dry and the wet seasons, from residents of two locations with differing parasite transmission levels (uphill and valley bottom), and 10 unexposed USA controls were probed on a protein microarray displaying 854 unique proteins of P. falciparum.
2013-06-20 | E-GEOD-48089 | biostudies-arrayexpress
Project description:Investigation of overall expression level in Plasmodium falciparum male and female mature gametocytes, and detection of any transcriptional differences between male and female gametocytes. The Plasmodium falciparum parasite with green fluorescent protein (GFP) expression under the control of alpha tubulin II promoter facilitated the separation of male and female gametocyte. This engineered parasite strain in this study are further described in Miao J, Fan Q, Parker D, Li X, Li J, et al. (2013) Puf Mediates Translation Repression of Transmission-Blocking Vaccine Candidates in Malaria Parasites. PLoS Pathog 9(4): e1003268. doi: 10.1371/journal.ppat.1003268
2016-01-30 | GSE77398 | GEO
Project description:The pathogenesis of severe malaria is complex and involves several pathways that influence host inflammation and endothelial function. The human malaria parasite Plasmodium falciparum is responsible for the majority of mortality and morbidity caused by malaria infection and differs from other human malaria species in the degree of accumulation of parasite-infected red blood cells in the microvasculature, known as cytoadherence or sequestration. In P. falciparum, cytoadherence is mediated by a protein called PfEMP1 which, due to its exposure to the host immune system, undergoes antigenic variation resulting in the expression of different PfEMP1 variants on the infected erythrocyte membrane. These PfEMP1s contain various combinations of adhesive domains, which allow for the differential engagement of a repertoire of endothelial receptors on the host microvasculature, with specific receptor usage associated with severe disease. Cytoadherence results in perturbation of the micro-circulation as well as direct effects on endothelial cells promoted by receptor-mediated signalling. We used a co-culture model of cytoadherence incubating human brain microvascular endothelial cells with erythrocytes infected with two parasite lines expressing different PfEMP1s; IT4var14 (long-form; ups B) that binds strongly to human brain microvascular endothelial cells mainly via ICAM-1, and IT4var 37 (short-form; ups C) that does not bind brain endothelium but shows high levels of binding to human dermal microvascular endothelial cells via CD36. We determined the transcriptional profile of the endothelial cells following different incubation periods with infected erythrocytes, identifying different transcriptional profiles of pathways involved in the pathology of severe malaria, such as inflammation, apoptosis and barrier integrity, induced by the two PfEMP1 variants.
2023-11-01 | E-MTAB-12730 | biostudies-arrayexpress
Project description:Cumulative malaria parasite exposure in endemic regions often results in the acquisition of partial immunity and asymptomatic infections. There is limited information on how host-parasite interactions mediate maintenance of chronic symptomless infections that sustain malaria transmission. Here, we have determined the gene expression profiles of the parasite population and the corresponding host peripheral blood mononuclear cells (PBMCs) from 21 children (<15 years). We compared children who were defined as uninfected, asymptomatic and those with febrile malaria. Children with asymptomatic infections had a parasite transcriptional profile characterized by a bias toward trophozoite stage (~12 hours-post invasion) parasites and low parasite levels, while earlier ring stage parasites were characteristic of febrile malaria. The host response of asymptomatic children was characterized by downregulated transcription of genes associated with inflammatory responses, compared with children with febrile malaria, which may lead to less cytoadherence of more mature parasite stages. Interestingly, the host responses during febrile infections that followed an asymptomatic infection featured stronger inflammatory responses, whereas the febrile host responses from previously uninfected children featured increased humoral immune responses. The priming effect of prior asymptomatic infection may explain the blunted acquisition of antibody responses seen to malaria antigens following natural exposure or vaccination in malaria endemic areas.
2024-02-14 | GSE240643 | GEO