Plasmodium Falciparum-infected Human Erythrocytes Research Articles

Erythrocytic Antioxidant Enzymes, Plasma Malondialdehyde and Haemoglobin Levels in Plasmodium Falciparum Infected Malaria Patients in Lagos, Nigeria

This study investigated the effect of malaria parasitaemia on Plasmodium falciparum infected human erythrocytes oxidative stress biomarkers and haemoglobin levels. Seventy (70) human subjects of fifty (50) P. falciparum positive and twenty (20) control subjects between the ages of 10-60 years were selected for this study. Rapid Diagnostic Test (RDT) and microscopy were used to identify P. falciparum. The samples were matched based on age, sex and level of parasitaemia. Samples of blood were collected for the determination of P. falciparum, level of parasitaemia, anti-oxidant assay and haemoglobin levels; to assess the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), malondialdehyde (MDA), total protein (PRO), reduced glutathione (GSH), haemoglobin and Parasite density. Haemoglobin level was determined using a Coulter A-T Pierce haematology analyzer (Beckman Coulter, Inc. Fullerton, CA, USA). This study showed that the mean level of PRO, CAT, MDA and SOD was significantly higher among the P. falciparum positive patients to those in the control while GPx level was lower, also, the mean level of HGB was significantly lower in the P. falciparum positive patients to those in the control. MDA, SOD, GSH and PRO level were higher among age group (10-20) in the P. falciparum infected patients and lower in the control subjects when compared to other age groups. MDA, SOD and PRO level were higher in the males than the females in both the malaria positive and controls. This study indicates that high parasitaemic patients are at greater risk of anaemia and oxidative stress compared to low parasitaemic ones.

Comparing infrared spectroscopic methods for the characterization of Plasmodium falciparum-infected human erythrocytes

Malaria, caused by parasites of the species Plasmodium, is among the major life-threatening diseases to afflict humanity. The infectious cycle of Plasmodium is very complex involving distinct life stages and transitions characterized by cellular and molecular alterations. Therefore, novel single-cell technologies are warranted to extract details pertinent to Plasmodium-host cell interactions and underpinning biological transformations. Herein, we tested two emerging spectroscopic approaches: (a) Optical Photothermal Infrared spectroscopy and (b) Atomic Force Microscopy combined with infrared spectroscopy in contrast to (c) Fourier Transform InfraRed microspectroscopy, to investigate Plasmodium-infected erythrocytes. Chemical spatial distributions of selected bands and spectra captured using the three modalities for major macromolecules together with advantages and limitations of each method is presented here. These results indicate that O-PTIR and AFM-IR techniques can be explored for extracting sub-micron resolution molecular signatures within heterogeneous and dynamic samples such as Plasmodium-infected human RBCs.

Molecular Imaging of a Zirconium-89 Labeled Antibody Targeting Plasmodium falciparum-Infected Human Erythrocytes.

Nuclear imaging is an important preclinical research tool to study infectious diseases in vivo and could be extended to investigate complex aspects of malaria infections. As such, we report for the first time successful radiolabeling of a novel antibody specific to Plasmodium-infected erythrocytes (IIIB6), its in vitro assessment and molecular imaging in nude mice. In vitro confocal microscopy was used to determine the stage-specificity of Plasmodium-infected erythrocytes recognised by IIIB6. To enable micro-positron emission tomography (PET)/X-ray computed tomography (CT) imaging, IIIB6 was conjugated to Bz-DFO-NCS and subsequently radiolabeled with zirconium-89. Healthy nude mice were injected with [89Zr]IIIB6, and pharmacokinetics and organ uptake were monitored over 24h. This was followed by post-mortem animal dissection to determine the biodistribution of [89Zr]IIIB6. IIIB6 recognised all the relevant stages of Plasmodium falciparum-infected erythrocytes (trophozoites, schizonts and gametocytes) that are responsible for severe malaria pathology. [89Zr]IIIB6-radiolabeling yields were efficient at 84-89%. Blood pool imaging analysis indicated a pharmacological half-life of 9.6 ± 2.5h for [89Zr]IIIB6. The highest standard uptake values were determined at 2-6h in the liver followed by the spleen, kidneys, heart, stomach and lung, respectively. Minimal activity was present in muscle and bone tissues. In vitro characterization of IIIB6 and pharmacokinetic characterization of [89Zr]IIIB6 revealed that this antibody has potential for future use in Plasmodium-infected mouse models to study malaria in a preclinical in vivo setting with PET/CT imaging.

The Malaria Parasite Progressively Dismantles the Host Erythrocyte Cytoskeleton for Efficient Egress

Plasmodium falciparum is an obligate intracellular pathogen responsible for worldwide morbidity and mortality. This parasite establishes a parasitophorous vacuole within infected red blood cells wherein it differentiates into multiple daughter cells that must rupture their host cells to continue another infectious cycle. Using atomic force microscopy, we establish that progressive macrostructural changes occur to the host cell cytoskeleton during the last 15 h of the erythrocytic life cycle. We used a comparative proteomics approach to determine changes in the membrane proteome of infected red blood cells during the final steps of parasite development that lead to egress. Mass spectrometry-based analysis comparing the red blood cell membrane proteome in uninfected red blood cells to that of infected red blood cells and postrupture vesicles highlighted two temporally distinct events; (Hay, S. I., et al. (2009). A world malaria map: Plasmodium falciparum endemicity in 2007. PLoS Med. 6, e1000048) the striking loss of cytoskeletal adaptor proteins that are part of the junctional complex, including α/β-adducin and tropomyosin, correlating temporally with the emergence of large holes in the cytoskeleton seen by AFM as early ~35 h postinvasion, and (Maier, A. G., et al. (2008) Exported proteins required for virulence and rigidity of Plasmodium falciparum-infected human erythrocytes. Cell 134, 48-61) large-scale proteolysis of the cytoskeleton during rupture ~48 h postinvasion, mediated by host calpain-1. We thus propose a sequential mechanism whereby parasites first remove a selected set of cytoskeletal adaptor proteins to weaken the host membrane and then use host calpain-1 to dismantle the remaining cytoskeleton, leading to red blood cell membrane collapse and parasite release.

Uptake of purines in Plasmodium falciparum-infected human erythrocytes is mostly mediated by the human Equilibrative Nucleoside Transporter and the human Facilitative Nucleobase Transporter

Uptake of purines in Plasmodium falciparum-infected human erythrocytes is mostly mediated by the human Equilibrative Nucleoside Transporter and the human Facilitative Nucleobase Transporter

Uptake of purines in Plasmodium falciparum-infected human erythrocytes is mostly mediated by the human equilibrative nucleoside transporter and the human facilitative nucleobase transporter.

BackgroundPlasmodium parasites are unable to synthesize purines de novo and have to salvage them from the host. Due to this limitation in the parasite, purine transporters have been an area of focus in the search for anti-malarial drugs. Although the uptake of purines through the human equilibrative nucleoside transporter (hENT1), the human facilitative nucleobase transporter (hFNT1) and the parasite-induced new permeation pathway (NPP) has been studied, no information appears to exist on the relative contribution of these three transporters to the uptake of adenosine and hypoxanthine. Using the appropriate transporter inhibitors, the role of each of these salvage pathways to the overall purine transport in intraerythrocytic Plasmodium falciparum was systematically investigated.MethodsThe transport of adenosine, hypoxanthine and adenine into uninfected and P. falciparum-infected human erythrocytes was investigated in the presence or absence of classical inhibitors of the hFNT1, hENT1 and NPP. The effective inhibition of the various transporters by the classical inhibitors was verified using appropriate known substrates. The ability of high concentration of unlabelled substrates to saturate these transporters was also studied.ResultsTransport of exogenous purine into infected or uninfected erythrocytes occurred primarily through saturable transporters rather than through the NPP. Hypoxanthine and adenine appeared to enter erythrocytes mainly through the hFNT1 nucleobase transporter whereas adenosine entered predominantly through the hENT1 nucleoside transporter. The rate of purine uptake was approximately doubled in infected cells compared to uninfected erythrocytes. In addition, it was found that the rate of adenosine uptake was considerably higher than the rate of hypoxanthine uptake in infected human red blood cells (RBC). It was also demonstrated that furosemide inhibited the transport of purine bases through hFNT1.ConclusionCollectively, the data obtained in this study clearly show that the endogenous host erythrocyte transporters hENT1 and hFNT1, rather than the NPP, are the major route of entry of purine into parasitized RBC. Inhibitors of hENT1 and hFNT1, as well as the NPP, should be considered in the development of anti-malarials targeted to purine transport.

Influence of Paclitaxel on Parasitemia and Survival of Plasmodium berghei Infected Mice

Paclitaxel triggers suicidal erythrocyte death or eryptosis, characterized by exposure of phosphatidylserine at the erythrocyte surface and cell shrinkage. Eryptosis of infected erythrocytes may delay development of parasitemia and thus favourably influence the course of malaria. The present study explored whether paclitaxel influences in vitro parasite growth and eryptosis of Plasmodium falciparum infected human erythrocytes and in vivo parasitemia and survival of Plasmodium berghei infected mice. Phosphatidylserine exposing erythrocytes were identified utilizing annexin V binding and erythrocyte volume was estimated from forward scatter in FACS analysis. In vitro infection of human erythrocytes with P. falciparum increased annexin binding and decreased forward scatter, effects augmented in the presence of paclitaxel (≥0.01 μM). Paclitaxel (≥0.01 μM) significantly decreased intraerythrocytic DNA/RNA content and in vitro parasitemia. In Plasmodium berghei infected mice parasitemia was significantly decreased (from 55.8% to 28.6% of circulating erythrocytes 20 days after infection) and mouse survival significantly enhanced (from 0% to 69.23% 25 days after infection) by administration of 8.5 mg/kg.b.w. of paclitaxel intraperitoneally from the eighth day of infection. In conclusion, paclitaxel decreases parasitemia and enhances survival of P. berghei infected mice, an effect, which may be due to stimulation of eryptosis and/or a direct toxic effect on the parasite.

Exported Proteins Required for Virulence and Rigidity of Plasmodium falciparum-Infected Human Erythrocytes

SummaryA major part of virulence for Plasmodium falciparum malaria infection, the most lethal parasitic disease of humans, results from increased rigidity and adhesiveness of infected host red cells. These changes are caused by parasite proteins exported to the erythrocyte using novel trafficking machinery assembled in the host cell. To understand these unique modifications, we used a large-scale gene knockout strategy combined with functional screens to identify proteins exported into parasite-infected erythrocytes and involved in remodeling these cells. Eight genes were identified encoding proteins required for export of the parasite adhesin PfEMP1 and assembly of knobs that function as physical platforms to anchor the adhesin. Additionally, we show that multiple proteins play a role in generating increased rigidity of infected erythrocytes. Collectively these proteins function as a pathogen secretion system, similar to bacteria and may provide targets for antivirulence based therapies to a disease responsible for millions of deaths annually.

Influence of NO Synthase Inhibitor L-NAME on Parasitemia and Survival of Plasmodium berghei Infected Mice

Accelerated suicidal death or eryptosis of infected erythrocytes may delay development of parasitemia in malaria. Eryptosis is inhibited by nitric oxide (NO). The present study has been performed to explore, whether inhibition of NO synthase by L-NAME modifies the course of malaria. We show here that L-NAME (>10 µM) increased phosphatidylserine exposure of Plasmodium falciparum infected human erythrocytes, an effect significantly more marked than in noninfected human erythrocytes. We further show that parasitemia in Plasmodium berghei infected mice was significantly decreased (from 50% to 18% of circulating erythrocytes 20 days after infection) by addition of 1 mg/ml L-NAME to the drinking water. According to CFSE labelling L-NAME treatment accelerated the clearance of both, noninfected and infected, erythrocytes from circulating blood, but did not significantly extend the life span of infected animals. In conclusion, treatment with L-NAME shortens the life span of circulating erythrocytes and thus delays development of parasitemia during malaria.

Influence of Chlorpromazine on Eryptosis, Parasitemia and Survival of Plasmodium berghei Infected Mice

Chlorpromazine has previously been shown to trigger suicidal erythrocyte death or eryptosis, which is characterized by exposure of phosphatidylserine at the erythrocyte surface and cell shrinkage. Premature suicidal death of infected erythrocytes is in turn considered to delay development of parasitemia and thus favourably influence the clinical course of malaria. The present experiments have been performed to explore whether chlorpromazine influences in vitro parasite growth and eryptosis of Plasmodium falciparum infected human erythrocytes and in vivo parasitemia and survival of P. berghei infected mice. Phosphatidylserine was estimated from annexin V binding and cell volume from forward scatter in FACS analysis. In vitro infection of human erythrocytes increased annexin binding and decreased forward scatter, effects augmented in the presence of chlorpromazine (≧10 µM). Chlorpromazine did not significantly alter intraerythrocytic DNA/RNA content but significantly (≧1 µM) decreased in vitro parasitemia. In chlorpromazine treated mice erythrocytes were more rapidly cleared from circulating blood than in nontreated mice. Parasitemia in P. berghei infected mice was significantly decreased (from 50 % to 28 % of circulating erythrocytes 22 days after infection) and mouse survival significantly enhanced (from 0 % to 80 % 30 days after infection) by addition of 1 mM chlorpromazine to the drinking water from the first day of infection. In conclusion, chlorpromazine favourably influences the course of malaria, an effect at least partially due to stimulation of suicidal erythrocyte death.

Influence of Amitriptyline on Eryptosis, Parasitemia and Survival of Plasmodium Berghei-Infected Mice

Plasmodia express a sphingomyelinase, which is apparently required for their development. On the other hand, the sphingomyelinase product ceramide has previously been shown to delay parasite development. Moreover, ceramide triggers suicidal erythrocyte death or eryptosis, characterized by exposure of phosphatidylserine at the erythrocyte surface and cell shrinkage. Accelerated eryptosis of infected erythrocytes is considered to clear infected erythrocytes from circulating blood and, thus, to favourably influence the clinical course of malaria. The present experiments explored whether the sphingomyelinase inhibitor amitriptyline or genetic knockout of host acid sphingomyelinase influence in vitro parasite growth, eryptosis of Plasmodium falciparum-infected human erythrocytes, in vivo parasitemia and survival of P. berghei-infected mice. Phosphatidylserine exposure was determined by annexin V-binding and cell volume by forward scatter in FACS analysis. In vitro infection of human erythrocytes increased annexin- binding, an effect blunted in the presence of amitriptyline (≥50 μM). Amitriptyline did not significantly alter intraerythrocytic parasite development but significantly (≥ 1 μM) delayed the increase in parasitemia in vitro. Most importantly, amitriptyline treatment (1 mM in drinking water) resulted in a significant delay of parasitemia and death of infected mice. However, upon infection, ceramide formation was stimulated in both, acid sphingomyelinase knockout mice (Smpd1^-/-) and their wild type littermates (Smpd1^+/+). Parasitemia following P. berghei infection was significantly lower in Smpd1^-/- than in Smpd1^+/+ mice but did not significantly extend the life span of infected animals. In conclusion, mammalian and parasite sphingomyelinase contribute to ceramide formation during malaria, whereby the parasite sphingomyelinase ultimately determines the course of the infection. Amitriptyline presumably blocks both sphingomyelinases and, thus, its use might be a novel strategy to treat malaria.

Lead decreases parasitemia and enhances survival of Plasmodium berghei-infected mice

Malaria, a disease accounting for more than one million deaths per year, is caused by intraerythrocytic growth of Plasmodia. Parasitemia may be blunted by suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine exposure. Triggers of eryptosis include lead nitrate (Pb(NO 3) 2). As shown here, Pb(NO 3) 2 (⩾10 μM) increased phosphatidylserine exposure of Plasmodium falciparum-infected human erythrocytes, an effect significantly more marked than in noninfected cells. Pb(NO 3) 2 treatment accelerated the clearance of erythrocytes from circulating blood. Parasitemia in Plasmodium berghei-infected mice was significantly decreased and mouse survival significantly enhanced by 100 μM Pb(NO 3) 2 (20 ppm) in drinking water. The treatment significantly increased reticulocyte number but did not significantly decrease erythrocyte number in noninfected mice and in infected animals mainly triggered the disappearance of P. berghei harbouring erythrocytes. In conclusion, Pb(NO 3) 2 accelerates eryptosis and subsequent clearance of infected erythrocytes and thus favourably influences the course of malaria.

Iron deficiency influences the course of malaria in Plasmodium berghei infected mice

Iron deficiency accelerates suicidal erythrocyte death, which is evident from phosphatidylserine exposure. The present study explored whether iron deficiency compromises intraerythrocytic growth of Plasmodium and enhances death of infected erythrocytes thus influencing the course of malaria. As a result, phosphatidylserine exposure is increased in Plasmodium falciparum infected human erythrocytes, an effect significantly more marked in iron deficiency. Moreover, iron deficiency impairs in vitro intraerythrocytic growth and infection of erythrocytes. In mice, iron-deficient erythrocytes are more rapidly cleared from circulating blood, an effect increased by infection with Plasmodium berghei. Parasitemia in P. berghei infected mice was significantly decreased (from 54% to 33% of circulating erythrocytes 20 days after infection) and mouse survival significantly enhanced (from 0% to 20% 30 days after infection) in iron-deficient mice. In conclusion, iron deficiency favourably influences the course of malaria, an effect partially due to accelerated suicidal death and subsequent clearance of infected erythrocytes.

Artemisinin inhibits cation currents in malaria-infected human erythrocytes

Background Previous patch-clamp studies have demonstrated inwardly and outwardly rectifying anion currents, ClC-2 Cl – currents, and nonselective Ca ++-permeable cation currents in Plasmodium falciparum–infected human erythrocytes. Methods The current work studied the effect of the potent antimalarial drug artemisinin on the P falciparum infection–induced whole cell currents in human erythrocyte. Results Artemisinin had no significant effect on the outwardly rectifying anion currents but inhibited the cation-selective currents with an apparent half-maximal inhibitory concentration of ≤10 μmol/L. Conclusion Because artemisinin reportedly inhibits the asexual parasite amplification with much higher potency, the antimalarial action of the drug cannot be attributed to the artemisinin effect on the cation currents. However, artemisinin may be used as a pharmacologic tool to dissect different current fractions in P falciparum–infected erythrocytes.

Two Distinct Domains Mediate Self-Assembly of Knob Protein in Plasmodium Falciparum-Infected Human Erythrocytes.

Plasmodium falciparum associated mortality is believed to originate from the adhesion of infected erythrocytes to the endothelial cells. The adhesion of mature parasite infected erythrocytes is mediated by the surface protrusions called knobs. A dominant constituent of knobs is the parasite derived knob-associated histidine-rich protein termed KAHRP or knob protein. Gene deletion experiments have shown that the knob protein is essential in malaria pathogenesis. Without the knob protein (KAHRP), adherence of malaria-infected erythrocytes is not established under physiological shear stress. The adhesive properties of infected erythrocytes are propagated by the direct interaction of KAHRP, a peripheral membrane protein, with the cytoplasmic domain of the P. falciparum erythrocyte membrane protein-1 (PfEMP1). Unlike the highly polymorphic extracellular domain, the cytoplasmic domain of PfEMP1 is conserved across species, hence the interest in delineating the mechanism of its interaction with KAHRP and components of the erythrocyte membrane. Our studies have observed recombinant KAHRP to self-associate into large aggregates in vitro. Under transmission electron microscopy, both knobs isolated from malaria-infected erythrocytes and self-assembled recombinant KAHRP in vitro have revealed a unique spiral shaped morphology. Based on these observations, we hypothesized that the unique knob spiral is formed by the self-assembly of KAHRP monomers and therefore must be encoded by distinct sequence elements within KAHRP. To investigate this speculation, we devised a solution binding assay and engineered a series of GST (glutathione S-transferase) and Trx (thioredoxin) fusion peptides to encompass the entire length of KAHRP. Binding measurements using heterologous combination of defined fusion peptides reveal a core histidine-rich amino terminal segment associating with a lysine-rich segment located within the carboxyl half of KAHRP. These findings suggest a novel head-to-tail interaction strategy employed by the intracellular parasite to assemble the spiral-shaped scaffold of KAHRP under the surface of electron dense knobs. Significantly, our results identify a novel self-interaction site within KAHRP that could be amenable to therapeutic intervention against cerebral malaria.

Targeting ion channels of Plasmodium falciparum-infected human erythrocytes for antimalarial development.

Aside from its profound clinical importance, the human malaria parasite, P. falciparum, is intrinsically fascinating to the cell biologist because it resides within the mature red blood cell (RBC). Because the inert RBC cannot otherwise provide sufficient amounts of key substrates to fuel the vigorous parasite metabolism, the parasite must have specialized adaptations for getting these solutes into the RBC and scavenging them from RBC cytosol. Two unusual ion channels have recently been identified within the infected RBC complex; these channels likely function in a sequential diffusive pathway of nutrient acquisition by the intracellular parasite. If so, they present novel opportunities for identification of ion channel inhibitors that may be useful antimalarial compounds.

Furosemide analogues as potent inhibitors of the new permeability pathways of Plasmodium falciparum-infected human erythrocytes.

Furosemide analogues as potent inhibitors of the new permeability pathways of Plasmodium falciparum-infected human erythrocytes.

Caught on camera: a snapshot of proteins moving through malaria-infected erythrocytes

The intracellular development of malaria parasites and the transport of molecules to the cytoplasm and surface of red blood cells (RBCs) presents the biophysical challenge of crossing three membranes. This complicated export of parasite-encoded proteins to the RBC surface is important for the pathogenicity of the malaria parasite, as the development of knob-like structures is known to facilitate cytoadhesion and sequestration and, ultimately, evasion of parasite killing by the spleen.To better understand this process, Wickham et al.1xTrafficking and assembly of the cytoadherence complex in Plasmodium falciparum-infected human erythrocytes. Wickham, M.E. et al. EMBO J. 2001; 20: 5636–5649Crossref | PubMed | Scopus (211)See all References1 fused a protein known to be targeted to the RBC surface – knob-associated histidine-rich protein (KAHRP) – to green fluorescent protein (GFP), and followed its pathway of transport using fluorescence microscopy and fluorescent recovery after photobleaching (FRAP). These techniques allowed them to study the movement of molecules in cells in real time.As the first step, they determined the peptide sequences required to target KAHRP to the RBC surface by using two different GFP-fusion constructs, one containing the first 60 amino acids of KAHRP fused to GFP, and another containing the first 123 amino acids of KAHRP fused to GFP. In transfected malaria parasites, the first construct demonstrated a ‘necklace of beads’ around the parasite, suggesting that the fusion protein was being accumulated in the parasitophorous space. This observation suggests that the first 60 amino acids were sufficient to allow (1) entry into the secretory pathway and targeting to the parasite plasma membrane; and (2) secretion from the parasite into the parasitophorous vacuolar space, but insufficient for targeting of the protein across the parasitophorous vacuole membrane and into the RBC cytoplasm. The GFP-fusion containing the first 123 amino acids, which encompasses the histidine-rich domain of KAHRP, was successfully targeted to the RBC cytoplasm, indicating that the following 63 amino acids were sufficient for targeting to the host cell membrane. The trafficking of these GFP-fusion proteins was also sensitive to Brefeldin A, which indicated that the proteins were moving through the endoplasmic reticulum (ER). Moreover, this finding suggests the involvement of a classical vesicle-mediated pathway rather than an alternative pathway, as previously suggested.The most striking observation in this study was the finding that GFP-fused KAHRP associated with structures in the RBC cytoplasm called Maurer's clefts. The function of these structures has been unclear and it has also been a mystery from where they are derived. In addition to the GFP-fusion proteins, two other knob-associated proteins, as well as an ER-resident protein known to be involved in ER-to-Golgi budding (SAR1p), co-localized to these Maurer's clefts. The association of the GFP-fusion proteins with these structures strongly suggests that the Maurer's clefts are derived from the parasite and, by some elaborate mechanism, they are relocated out of the parasite and into the host cell cytoplasm. This type of elaboration of the secretory system of an intracellular pathogen is the first example of its kind in eukaryotic cell biology.

Trafficking and assembly of the cytoadherence complex in Plasmodium falciparum-infected human erythrocytes.

After invading human erythrocytes, the malarial parasite Plasmodium falciparum, initiates a remarkable process of secreting proteins into the surrounding erythrocyte cytoplasm and plasma membrane. One of these exported proteins, the knob-associated histidine-rich protein (KAHRP), is essential for microvascular sequestration, a strategy whereby infected red cells adhere via knob structures to capillary walls and thus avoid being eliminated by the spleen. This cytoadherence is an important factor in many of the deaths caused by malaria. Green fluorescent protein fusions and fluorescence recovery after photobleaching were used to follow the pathway of KAHRP deployment from the parasite endomembrane system into an intermediate depot between parasite and host, then onwards to the erythrocyte cytoplasm and eventually into knobs. Sequence elements essential to individual steps in the pathway are defined and we show that parasite-derived structures, known as Maurer's clefts, are an elaboration of the canonical secretory pathway that is transposed outside the parasite into the host cell, the first example of its kind in eukaryotic biology.

Uptake of an antiplasmodial protease inhibitor into Plasmodium falciparum-infected human erythrocytes via a parasite-induced pathway

Uptake of an antiplasmodial protease inhibitor into Plasmodium falciparum-infected human erythrocytes via a parasite-induced pathway