1
|
Lenz T, Zhang X, Chakraborty A, Ardakany AR, Prudhomme J, Ay F, Deitsch K, Le Roch KG. Chromatin structure and var2csa - a tango in regulation of var gene expression in the human malaria parasite, Plasmodium falciparum? BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.13.580059. [PMID: 38405848 PMCID: PMC10888805 DOI: 10.1101/2024.02.13.580059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Over the last few decades, novel methods have been developed to study how chromosome positioning within the nucleus may play a role in gene regulation. Adaptation of these methods in the human malaria parasite, Plasmodium falciparum, has recently led to the discovery that the three-dimensional structure of chromatin within the nucleus may be critical in controlling expression of virulence genes (var genes). Recent work has implicated an unusual, highly conserved var gene called var2csa in contributing to coordinated transcriptional switching, however how this gene functions in this capacity is unknown. To further understand how var2csa influences var gene switching, targeted DNA double-strand breaks (DSBs) within the sub-telomeric region of chromosome 12 were used to delete the gene and the surrounding chromosomal region. To characterize the changes in chromatin architecture stemming from this deletion and how these changes could affect var gene expression, we used a combination of RNA-seq, Chip-seq and Hi-C to pinpoint epigenetic and chromatin structural modifications in regions of differential gene expression. We observed a net gain of interactions in sub-telomeric regions and internal var gene regions following var2csa knockout, indicating an increase of tightly controlled heterochromatin structures. Our results suggest that disruption of var2csa results not only in changes in var gene transcriptional regulation but also a significant tightening of heterochromatin clusters thereby disrupting coordinated activation of var genes throughout the genome. Altogether our result confirms a strong link between the var2csa locus, chromatin structure and var gene expression.
Collapse
Affiliation(s)
- Todd Lenz
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Abhijit Chakraborty
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | | | - Jacques Prudhomme
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Ferhat Ay
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Kirk Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Karine G. Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| |
Collapse
|
2
|
Andradi-Brown C, Wichers-Misterek JS, von Thien H, Höppner YD, Scholz JAM, Hansson H, Filtenborg Hocke E, Gilberger TW, Duffy MF, Lavstsen T, Baum J, Otto TD, Cunnington AJ, Bachmann A. A novel computational pipeline for var gene expression augments the discovery of changes in the Plasmodium falciparum transcriptome during transition from in vivo to short-term in vitro culture. eLife 2024; 12:RP87726. [PMID: 38270586 PMCID: PMC10945709 DOI: 10.7554/elife.87726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024] Open
Abstract
The pathogenesis of severe Plasmodium falciparum malaria involves cytoadhesive microvascular sequestration of infected erythrocytes, mediated by P. falciparum erythrocyte membrane protein 1 (PfEMP1). PfEMP1 variants are encoded by the highly polymorphic family of var genes, the sequences of which are largely unknown in clinical samples. Previously, we published new approaches for var gene profiling and classification of predicted binding phenotypes in clinical P. falciparum isolates (Wichers et al., 2021), which represented a major technical advance. Building on this, we report here a novel method for var gene assembly and multidimensional quantification from RNA-sequencing that outperforms the earlier approach of Wichers et al., 2021, on both laboratory and clinical isolates across a combination of metrics. Importantly, the tool can interrogate the var transcriptome in context with the rest of the transcriptome and can be applied to enhance our understanding of the role of var genes in malaria pathogenesis. We applied this new method to investigate changes in var gene expression through early transition of parasite isolates to in vitro culture, using paired sets of ex vivo samples from our previous study, cultured for up to three generations. In parallel, changes in non-polymorphic core gene expression were investigated. Modest but unpredictable var gene switching and convergence towards var2csa were observed in culture, along with differential expression of 19% of the core transcriptome between paired ex vivo and generation 1 samples. Our results cast doubt on the validity of the common practice of using short-term cultured parasites to make inferences about in vivo phenotype and behaviour.
Collapse
Affiliation(s)
- Clare Andradi-Brown
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College LondonLondonUnited Kingdom
- Department of Life Sciences, Imperial College London, South KensingtonLondonUnited Kingdom
- Centre for Paediatrics and Child Health, Imperial College LondonLondonUnited Kingdom
| | - Jan Stephan Wichers-Misterek
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Heidrun von Thien
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Yannick D Höppner
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Judith AM Scholz
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
| | - Helle Hansson
- Center for Medical Parasitology, Department of Immunology and Microbiology, University of CopenhagenCopenhagenDenmark
- Department of Infectious Diseases, Copenhagen University HospitalCopenhagenDenmark
| | - Emma Filtenborg Hocke
- Center for Medical Parasitology, Department of Immunology and Microbiology, University of CopenhagenCopenhagenDenmark
- Department of Infectious Diseases, Copenhagen University HospitalCopenhagenDenmark
| | - Tim Wolf Gilberger
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Michael F Duffy
- Department of Microbiology and Immunology, University of MelbourneMelbourneAustralia
| | - Thomas Lavstsen
- Center for Medical Parasitology, Department of Immunology and Microbiology, University of CopenhagenCopenhagenDenmark
- Department of Infectious Diseases, Copenhagen University HospitalCopenhagenDenmark
| | - Jake Baum
- Department of Life Sciences, Imperial College London, South KensingtonLondonUnited Kingdom
- School of Biomedical Sciences, Faculty of Medicine & Health, UNSW, KensingtonSydneyUnited Kingdom
| | - Thomas D Otto
- School of Infection & Immunity, MVLS, University of GlasgowGlasgowUnited Kingdom
| | - Aubrey J Cunnington
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College LondonLondonUnited Kingdom
- Centre for Paediatrics and Child Health, Imperial College LondonLondonUnited Kingdom
| | - Anna Bachmann
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-StrasseHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-RiemsHamburgGermany
| |
Collapse
|
3
|
Fikadu M, Ashenafi E. Malaria: An Overview. Infect Drug Resist 2023; 16:3339-3347. [PMID: 37274361 PMCID: PMC10237628 DOI: 10.2147/idr.s405668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 05/18/2023] [Indexed: 06/06/2023] Open
Abstract
Malaria is a global public health burden with an estimated 229 million cases reported worldwide in 2019. About 94% of the reported cases were recorded in the African region. About 200 different species of protozoa have been identified so far and among them, at least 13 species are known to be pathogenic to humans. The life cycle of the malaria parasite is a complex process comprising an Anopheles mosquito and a vertebrate host. Its pathophysiology is characterized by fever secondary to the rupture of erythrocytes, macrophage ingestion of merozoites, and/or the presence of antigen-presenting trophozoites in the circulation or spleen which mediates the release of tumor necrosis factor α (TNF-α). Malaria can be diagnosed through clinical observation of the signs and symptoms of the disease. Other diagnostic techniques used to diagnose malaria are the microscopic detection of parasites from blood smears and antigen-based rapid diagnostic tests. The management of malaria involves preventive and/or curative approaches. Since untreated uncomplicated malaria can progress to severe malaria. To prevent or delay the spread of antimalarial drug resistance, WHO recommends the use of combination therapy for all episodes of malaria with at least two effective antimalarial agents having a different mechanism of action. The Centers for Disease Control (CDC) emphasizes that there is no prophylactic agent that can prevent malaria 100%. Therefore, prophylaxis shall be augmented with the use of personal protective measures.
Collapse
Affiliation(s)
- Muluemebet Fikadu
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Ephrem Ashenafi
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| |
Collapse
|
4
|
Schneider V, Visone J, Harris C, Florini F, Hadjimichael E, Zhang X, Gross M, Rhee K, Ben Mamoun C, Kafsack B, Deitsch K. The human malaria parasite Plasmodium falciparum can sense environmental changes and respond by antigenic switching. Proc Natl Acad Sci U S A 2023; 120:e2302152120. [PMID: 37068249 PMCID: PMC10151525 DOI: 10.1073/pnas.2302152120] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 03/20/2023] [Indexed: 04/19/2023] Open
Abstract
The primary antigenic and virulence determinant of the human malaria parasite Plasmodium falciparum is a variant surface protein called PfEMP1. Different forms of PfEMP1 are encoded by a multicopy gene family called var, and switching between active genes enables the parasites to evade the antibody response of their human hosts. var gene switching is key for the maintenance of chronic infections; however, what controls switching is unknown, although it has been suggested to occur at a constant frequency with little or no environmental influence. var gene transcription is controlled epigenetically through the activity of histone methyltransferases (HMTs). Studies in model systems have shown that metabolism and epigenetic control of gene expression are linked through the availability of intracellular S-adenosylmethionine (SAM), the principal methyl donor in biological methylation modifications, which can fluctuate based on nutrient availability. To determine whether environmental conditions and changes in metabolism can influence var gene expression, P. falciparum was cultured in media with altered concentrations of nutrients involved in SAM metabolism. We found that conditions that influence lipid metabolism induce var gene switching, indicating that parasites can respond to changes in their environment by altering var gene expression patterns. Genetic modifications that directly modified expression of the enzymes that control SAM levels similarly led to profound changes in var gene expression, confirming that changes in SAM availability modulate var gene switching. These observations directly challenge the paradigm that antigenic variation in P. falciparum follows an intrinsic, programed switching rate, which operates independently of any external stimuli.
Collapse
Affiliation(s)
- Victoria M. Schneider
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
- Laboratory of Chemical Biology and Microbial Pathogenesis, Rockefeller University, New York, NY 10065
| | - Joseph E. Visone
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Chantal T. Harris
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Francesca Florini
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Evi Hadjimichael
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Mackensie R. Gross
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Kyu Y. Rhee
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Choukri Ben Mamoun
- Section of Infectious Disease, Department of Microbial Pathogenesis, Yale School of Medicine, Yale University New Haven, CT 06510
| | - Björn F. C. Kafsack
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| |
Collapse
|
5
|
Abstract
"The Primate Malarias" book has been a uniquely important resource for multiple generations of scientists, since its debut in 1971, and remains pertinent to the present day. Indeed, nonhuman primates (NHPs) have been instrumental for major breakthroughs in basic and pre-clinical research on malaria for over 50 years. Research involving NHPs have provided critical insights and data that have been essential for malaria research on many parasite species, drugs, vaccines, pathogenesis, and transmission, leading to improved clinical care and advancing research goals for malaria control, elimination, and eradication. Whilst most malaria scientists over the decades have been studying Plasmodium falciparum, with NHP infections, in clinical studies with humans, or using in vitro culture or rodent model systems, others have been dedicated to advancing research on Plasmodium vivax, as well as on phylogenetically related simian species, including Plasmodium cynomolgi, Plasmodium coatneyi, and Plasmodium knowlesi. In-depth study of these four phylogenetically related species over the years has spawned the design of NHP longitudinal infection strategies for gathering information about ongoing infections, which can be related to human infections. These Plasmodium-NHP infection model systems are reviewed here, with emphasis on modern systems biological approaches to studying longitudinal infections, pathogenesis, immunity, and vaccines. Recent discoveries capitalizing on NHP longitudinal infections include an advanced understanding of chronic infections, relapses, anaemia, and immune memory. With quickly emerging new technological advances, more in-depth research and mechanistic discoveries can be anticipated on these and additional critical topics, including hypnozoite biology, antigenic variation, gametocyte transmission, bone marrow dysfunction, and loss of uninfected RBCs. New strategies and insights published by the Malaria Host-Pathogen Interaction Center (MaHPIC) are recapped here along with a vision that stresses the importance of educating future experts well trained in utilizing NHP infection model systems for the pursuit of innovative, effective interventions against malaria.
Collapse
Affiliation(s)
- Mary R Galinski
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA.
- Emory Vaccine Center, Emory University, Atlanta, GA, USA.
- Emory National Primate Research Center (Yerkes National Primate Research Center), Emory University, Atlanta, GA, USA.
| |
Collapse
|
6
|
Abstract
Quantitative real-time PCR (qPCR) is a simple and sensitive method for determining the amount of a specific target DNA sequence present in a sample. Compared to RNA-seq, reverse transcription qPCR (RT-qPCR) is fast, requires only low input material and is easy to analyze. Therefore, qPCR is widely used to analyze gene expression in P. falciparum, including analyses of the multicopy gene families encoding variant surface antigens (VSAs), whose expression is clonally variant and prone to changes over time. In the recent years, several P. falciparum genomes of culture-adapted strains have been sequenced, providing the knowledge to design variable gene family-specific qPCR primers for each P. falciparum genetic background. Here, we describe the required materials, methods and key factors to perform RT-qPCR experiments to determine VSA transcript abundances in the P. falciparum clones 3D7/NF54, IT4, HB3, and 7G8.
Collapse
Affiliation(s)
- Anna Bachmann
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
- Centre for Structural Systems Biology, Hamburg, Germany.
- Biology Department, University of Hamburg, Hamburg, Germany.
- German Center for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck-Riems, Hamburg, Germany.
| | - Thomas Lavstsen
- Centre for Medical Parasitology at Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
- Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
| |
Collapse
|
7
|
Expression Patterns of Plasmodium falciparum Clonally Variant Genes at the Onset of a Blood Infection in Malaria-Naive Humans. mBio 2021; 12:e0163621. [PMID: 34340541 PMCID: PMC8406225 DOI: 10.1128/mbio.01636-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clonally variant genes (CVGs) play fundamental roles in the adaptation of Plasmodium falciparum to fluctuating conditions of the human host. However, their expression patterns under the natural conditions of the blood circulation have been characterized in detail for only a few specific gene families. Here, we provide a detailed characterization of the complete P. falciparum transcriptome across the full intraerythrocytic development cycle (IDC) at the onset of a blood infection in malaria-naive human volunteers. We found that the vast majority of transcriptional differences between parasites obtained from the volunteers and the parental parasite line maintained in culture occurred in CVGs. In particular, we observed a major increase in the transcript levels of most genes of the pfmc-2tm and gbp families and of specific genes of other families, such as phist, hyp10, rif, or stevor, in addition to previously reported changes in var and clag3 gene expression. Increased transcript levels of individual pfmc-2tm, rif, and stevor genes involved activation in small subsets of parasites. Large transcriptional differences correlated with changes in the distribution of heterochromatin, confirming their epigenetic nature. Furthermore, the similar expression of several CVGs between parasites collected at different time points along the blood infection suggests that the epigenetic memory for multiple CVG families is lost during transmission stages, resulting in a reset of their transcriptional state. Finally, the CVG expression patterns observed in a volunteer likely infected by a single sporozoite suggest that new epigenetic patterns are established during liver stages.
Collapse
|
8
|
Camponovo F, Lee TE, Russell JR, Burgert L, Gerardin J, Penny MA. Mechanistic within-host models of the asexual Plasmodium falciparum infection: a review and analytical assessment. Malar J 2021; 20:309. [PMID: 34246274 PMCID: PMC8272282 DOI: 10.1186/s12936-021-03813-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 06/11/2021] [Indexed: 12/03/2022] Open
Abstract
Background Malaria blood-stage infection length and intensity are important drivers of disease and transmission; however, the underlying mechanisms of parasite growth and the host’s immune response during infection remain largely unknown. Over the last 30 years, several mechanistic mathematical models of malaria parasite within-host dynamics have been published and used in malaria transmission models. Methods Mechanistic within-host models of parasite dynamics were identified through a review of published literature. For a subset of these, model code was reproduced and descriptive statistics compared between the models using fitted data. Through simulation and model analysis, key features of the models were compared, including assumptions on growth, immune response components, variant switching mechanisms, and inter-individual variability. Results The assessed within-host malaria models generally replicate infection dynamics in malaria-naïve individuals. However, there are substantial differences between the model dynamics after disease onset, and models do not always reproduce late infection parasitaemia data used for calibration of the within host infections. Models have attempted to capture the considerable variability in parasite dynamics between individuals by including stochastic parasite multiplication rates; variant switching dynamics leading to immune escape; variable effects of the host immune responses; or via probabilistic events. For models that capture realistic length of infections, model representations of innate immunity explain early peaks in infection density that cause clinical symptoms, and model representations of antibody immune responses control the length of infection. Models differed in their assumptions concerning variant switching dynamics, reflecting uncertainty in the underlying mechanisms of variant switching revealed by recent clinical data during early infection. Overall, given the scarce availability of the biological evidence there is limited support for complex models. Conclusions This study suggests that much of the inter-individual variability observed in clinical malaria infections has traditionally been attributed in models to random variability, rather than mechanistic disease dynamics. Thus, it is proposed that newly developed models should assume simple immune dynamics that minimally capture mechanistic understandings and avoid over-parameterization and large stochasticity which inaccurately represent unknown disease mechanisms. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03813-z.
Collapse
Affiliation(s)
- Flavia Camponovo
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, 02115, USA
| | - Tamsin E Lee
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jonathan R Russell
- Institute of Disease Modeling, Bill & Melinda Gates Foundation, 500 5th Ave N, Seattle, WA, 98109, USA
| | - Lydia Burgert
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jaline Gerardin
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| |
Collapse
|
9
|
Gross MR, Hsu R, Deitsch KW. Evolution of transcriptional control of antigenic variation and virulence in human and ape malaria parasites. BMC Ecol Evol 2021; 21:139. [PMID: 34238209 PMCID: PMC8265125 DOI: 10.1186/s12862-021-01872-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/02/2021] [Indexed: 11/13/2022] Open
Abstract
Background The most severe form of human malaria is caused by the protozoan parasite Plasmodium falciparum. This unicellular organism is a member of a subgenus of Plasmodium called the Laverania that infects apes, with P. falciparum being the only member that infects humans. The exceptional virulence of this species to humans can be largely attributed to a family of variant surface antigens placed by the parasites onto the surface of infected red blood cells that mediate adherence to the vascular endothelium. These proteins are encoded by a large, multicopy gene family called var, with each var gene encoding a different form of the protein. By changing which var gene is expressed, parasites avoid immune recognition, a process called antigenic variation that underlies the chronic nature of malaria infections. Results Here we show that the common ancestor of the branch of the Laverania lineage that includes the human parasite underwent a remarkable change in the organization and structure of elements linked to the complex transcriptional regulation displayed by the var gene family. Unlike the other members of the Laverania, the clade that gave rise to P. falciparum evolved distinct subsets of var genes distinguishable by different upstream transcriptional regulatory regions that have been associated with different expression profiles and virulence properties. In addition, two uniquely conserved var genes that have been proposed to play a role in coordinating transcriptional switching similarly arose uniquely within this clade. We hypothesize that these changes originated at a time of dramatic climatic change on the African continent that is predicted to have led to significant changes in transmission dynamics, thus selecting for patterns of antigenic variation that enabled lengthier, more chronic infections. Conclusions These observations suggest that changes in transmission dynamics selected for significant alterations in the transcriptional regulatory mechanisms that mediate antigenic variation in the parasite lineage that includes P. falciparum. These changes likely underlie the chronic nature of these infections as well as their exceptional virulence. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-021-01872-z.
Collapse
Affiliation(s)
- Mackensie R Gross
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA
| | - Rosie Hsu
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA
| | - Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA.
| |
Collapse
|
10
|
Cubillos EFG, Prata IO, Fotoran WL, Ranford-Cartwright L, Wunderlich G. The Transcription Factor PfAP2-O Influences Virulence Gene Transcription and Sexual Development in Plasmodium falciparum. Front Cell Infect Microbiol 2021; 11:669088. [PMID: 34268135 PMCID: PMC8275450 DOI: 10.3389/fcimb.2021.669088] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/23/2021] [Indexed: 12/02/2022] Open
Abstract
The human malaria parasite Plasmodium falciparum expresses variant PfEMP1 proteins on the infected erythrocyte, which function as ligands for endothelial receptors in capillary vessels, leading to erythrocyte sequestration and severe malaria. The factors that orchestrate the mono-allelic expression of the 45–90 PfEMP1-encoding var genes within each parasite genome are still not fully identified. Here, we show that the transcription factor PfAP2-O influences the transcription of var genes. The temporary knockdown of PfAP2-O leads to a complete loss of var transcriptional memory and a decrease in cytoadherence in CD36 adherent parasites. AP2-O-knocked-down parasites exhibited also significant reductions in transmission through Anopheles mosquitoes. We propose that PfAP2-O is, beside its role in transmission stages, also one of the virulence gene transcriptional regulators and may therefore be exploited as an important target to disrupt severe malaria and block parasite transmission.
Collapse
Affiliation(s)
- Eliana F G Cubillos
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Isadora Oliveira Prata
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Wesley Luzetti Fotoran
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Lisa Ranford-Cartwright
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, United Kingdom
| | - Gerhard Wunderlich
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| |
Collapse
|
11
|
Milne K, Ivens A, Reid AJ, Lotkowska ME, O'Toole A, Sankaranarayanan G, Munoz Sandoval D, Nahrendorf W, Regnault C, Edwards NJ, Silk SE, Payne RO, Minassian AM, Venkatraman N, Sanders MJ, Hill AVS, Barrett M, Berriman M, Draper SJ, Rowe JA, Spence PJ. Mapping immune variation and var gene switching in naive hosts infected with Plasmodium falciparum. eLife 2021; 10:e62800. [PMID: 33648633 PMCID: PMC7924948 DOI: 10.7554/elife.62800] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/09/2021] [Indexed: 02/06/2023] Open
Abstract
Falciparum malaria is clinically heterogeneous and the relative contribution of parasite and host in shaping disease severity remains unclear. We explored the interaction between inflammation and parasite variant surface antigen (VSA) expression, asking whether this relationship underpins the variation observed in controlled human malaria infection (CHMI). We uncovered marked heterogeneity in the host response to blood challenge; some volunteers remained quiescent, others triggered interferon-stimulated inflammation and some showed transcriptional evidence of myeloid cell suppression. Significantly, only inflammatory volunteers experienced hallmark symptoms of malaria. When we tracked temporal changes in parasite VSA expression to ask whether variants associated with severe disease rapidly expand in naive hosts, we found no transcriptional evidence to support this hypothesis. These data indicate that parasite variants that dominate severe malaria do not have an intrinsic growth or survival advantage; instead, they presumably rely upon infection-induced changes in their within-host environment for selection.
Collapse
Affiliation(s)
- Kathryn Milne
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
| | - Alasdair Ivens
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
| | - Adam J Reid
- Wellcome Sanger InstituteCambridgeUnited Kingdom
| | | | - Aine O'Toole
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
- Institute of Evolutionary Biology, University of EdinburghEdinburghUnited Kingdom
| | | | - Diana Munoz Sandoval
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Instituto de Microbiologia, Universidad San Francisco de QuitoQuitoEcuador
| | - Wiebke Nahrendorf
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
| | - Clement Regnault
- Wellcome Centre for Integrative Parasitology, University of GlasgowGlasgowUnited Kingdom
- Glasgow Polyomics, University of GlasgowGlasgowUnited Kingdom
| | - Nick J Edwards
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Sarah E Silk
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Ruth O Payne
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | | | | | | | - Adrian VS Hill
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Michael Barrett
- Wellcome Centre for Integrative Parasitology, University of GlasgowGlasgowUnited Kingdom
- Glasgow Polyomics, University of GlasgowGlasgowUnited Kingdom
| | | | - Simon J Draper
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - J Alexandra Rowe
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
| | - Philip J Spence
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
| |
Collapse
|
12
|
Bhandari S, Krishna S, Patel PP, Singh MP, Singh N, Sharma A, Bharti PK. Diversity and expression of Plasmodium falciparum var gene in severe and mild malaria cases from Central India. Int J Infect Dis 2020; 103:552-559. [PMID: 33326872 DOI: 10.1016/j.ijid.2020.12.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/09/2020] [Accepted: 12/10/2020] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Plasmodium falciparum erythrocyte membrane protein is encoded by a highly variable multicopy var gene family known to play a key role in malaria pathogenicity. Therefore, we investigated sequence variation, expression profile and immune response of the Duffy binding-like domain (DBLα) region of the var gene. METHODS Blood samples were collected from patients with cerebral, severe and mild malaria in Chhattisgarh, India, a region with endemic malaria. Polymerase chain reaction amplicons were cloned and sequenced to determine sequence variation. The expression level was analyzed targeting the upstream region of var gene using the Delta-Delta-Ct method. Immunoglobulin G (IgG) level was determined against the 6 synthetic peptides of the DBLα region. RESULTS The study identified that group 1 and group 5 sequences (cysteine/position of limited variability (cys/PoLV) classification) along with cys2/cys4 and MFK*/REY motifs and short amino acid length were significantly associated with malaria severity. The specific PoLV (MFKS, LREA, PTNL) were restricted to cerebral malaria. The expression level of var group A was higher than var groups B and C, demonstrating its prognostic characteristic. All peptides showed high-quality IgG response, while VAR P5 appeared to be a good marker for severity. CONCLUSIONS The present study illustrates the presence of specific sequences of DBLα tags involved in severe malaria that could be targeted in future interventions for malaria control and elimination.
Collapse
Affiliation(s)
- Sneha Bhandari
- ICMR-National Institute of Research in Tribal Health, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| | - Sri Krishna
- ICMR-National Institute of Research in Tribal Health, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| | - Priyanka P Patel
- ICMR-National Institute of Research in Tribal Health, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| | - Mrigendra P Singh
- ICMR-National Institute of Malaria Research, Field Unit, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| | - Neeru Singh
- ICMR-National Institute of Research in Tribal Health, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| | - Anjana Sharma
- Department of Post Graduate Studies and Research in Biological Sciences, Rani Durgavati Vishwavidyalaya, Jabalpur, Madhya Pradesh, India.
| | - Praveen K Bharti
- ICMR-National Institute of Research in Tribal Health, Nagpur Road, Garha, Jabalpur, 482003, Madhya Pradesh, India.
| |
Collapse
|
13
|
Llorà-Batlle O, Tintó-Font E, Cortés A. Transcriptional variation in malaria parasites: why and how. Brief Funct Genomics 2020; 18:329-341. [PMID: 31114839 DOI: 10.1093/bfgp/elz009] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 02/04/2019] [Accepted: 04/10/2019] [Indexed: 12/24/2022] Open
Abstract
Transcriptional differences enable the generation of alternative phenotypes from the same genome. In malaria parasites, transcriptional plasticity plays a major role in the process of adaptation to fluctuations in the environment. Multiple studies with culture-adapted parasites and field isolates are starting to unravel the different transcriptional alternatives available to Plasmodium falciparum and the underlying molecular mechanisms. Here we discuss how epigenetic variation, directed transcriptional responses and also genetic changes that affect transcript levels can all contribute to transcriptional variation and, ultimately, parasite survival. Some transcriptional changes are driven by stochastic events. These changes can occur spontaneously, resulting in heterogeneity within parasite populations that provides the grounds for adaptation by dynamic natural selection. However, transcriptional changes can also occur in response to external cues. A better understanding of the mechanisms that the parasite has evolved to alter its transcriptome may ultimately contribute to the design of strategies to combat malaria to which the parasite cannot adapt.
Collapse
Affiliation(s)
- Oriol Llorà-Batlle
- ISGlobal, Hospital Clínic - Universitat de Barcelona, 08036 Barcelona, Catalonia, Spain
| | - Elisabet Tintó-Font
- ISGlobal, Hospital Clínic - Universitat de Barcelona, 08036 Barcelona, Catalonia, Spain
| | | |
Collapse
|
14
|
Odedra A, McCarthy JS. Safety Considerations for Malaria Volunteer Infection Studies: A Mini-Review. Am J Trop Med Hyg 2020; 102:934-939. [PMID: 32189610 DOI: 10.4269/ajtmh.19-0351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Malaria clinical studies entailing the experimental infection of healthy volunteers with Plasmodium parasites by bites from infected mosquitos, injection of cryopreserved sporozoites, or injection of blood-stage parasites provide valuable information for vaccine and drug development. Success of these studies depends on maintaining safety. In this mini-review, we discuss the safety risks and associated mitigation strategies of these three types of experimental malaria infection. We aimed to inform researchers and regulators who are currently involved in or are planning to establish experimental malaria infection studies in endemic or non-endemic settings.
Collapse
Affiliation(s)
- Anand Odedra
- QIMR Berghofer Medical Research Institute, Herston, Australia.,Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - James S McCarthy
- The University of Queensland, St Lucia, Australia.,QIMR Berghofer Medical Research Institute, Herston, Australia
| |
Collapse
|
15
|
Quintana MDP, Smith-Togobo C, Moormann A, Hviid L. Endemic Burkitt lymphoma - an aggressive childhood cancer linked to Plasmodium falciparum exposure, but not to exposure to other malaria parasites. APMIS 2020; 128:129-135. [PMID: 32133709 DOI: 10.1111/apm.13018] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 12/02/2019] [Indexed: 12/12/2022]
Abstract
Burkitt lymphoma (BL) is an aggressive non-Hodgkin lymphoma. The prevalence of BL is ten-fold higher in areas with stable transmission of Plasmodium falciparum malaria, where it is the most common childhood cancer, and is referred to as endemic BL (eBL). In addition to its association with exposure to P. falciparum infection, eBL is strongly associated with Epstein-Barr virus (EBV) infection (>90%). This is in contrast to BL as it occurs outside P. falciparum-endemic areas (sporadic BL), where only a minority of the tumours are EBV-positive. Although the striking geographical overlap in the distribution of eBL and P. falciparum was noted shortly after the first detailed description of eBL in 1958, the molecular details of the interaction between malaria and eBL remain unresolved. It is furthermore unexplained why exposure to P. falciparum appears to be essentially a prerequisite to the development of eBL, whereas other types of malaria parasites that infect humans have no impact. In this brief review, we summarize how malaria exposure may precipitate the malignant transformation of a B-cell clone that leads to eBL, and propose an explanation for why P. falciparum uniquely has this capacity.
Collapse
Affiliation(s)
- Maria Del Pilar Quintana
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Cecilia Smith-Togobo
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Biochemistry, Cell and Molecular Biology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Ann Moormann
- Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Lars Hviid
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark
| |
Collapse
|
16
|
Hoo R, Bruske E, Dimonte S, Zhu L, Mordmüller B, Sim BKL, Kremsner PG, Hoffman SL, Bozdech Z, Frank M, Preiser PR. Transcriptome profiling reveals functional variation in Plasmodium falciparum parasites from controlled human malaria infection studies. EBioMedicine 2019; 48:442-452. [PMID: 31521613 PMCID: PMC6838377 DOI: 10.1016/j.ebiom.2019.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/29/2019] [Accepted: 09/01/2019] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND The transcriptome of Plasmodium falciparum clinical isolates varies according to strain, mosquito bites, disease severity and clinical history. Therefore, it remains a challenge to directly interpret the parasite's transcriptomic information into a more general biological signature in a natural human malaria infection. These confounding variations can be potentially overcome with parasites derived from controlled-human malaria infection (CHMI) studies. METHODS We performed CHMI studies in healthy and immunologically naïve volunteers receiving the same P. falciparum strain ((Sanaria® PfSPZ Challenge (NF54)), but with different sporozoite dosage and route of infection. Parasites isolated from these volunteers at the day of patency were subjected to in vitro culture for several generations and synchronized ring-stage parasites were subjected to transcriptome profiling. FINDINGS We observed clear deviations between CHMI-derived parasites from volunteer groups receiving different PfSPZ dose and route. CHMI-derived parasites and the pre-mosquito strain used for PfSPZ generation showed significant transcriptional variability for gene clusters associated with malaria pathogenesis, immune evasion and transmission. These transcriptional variation signature clusters were also observed in the transcriptome of P. falciparum isolates from acute clinical infections. INTERPRETATION Our work identifies a previously unrecognized transcriptional pattern in malaria infections in a non-immune background. Significant transcriptome heterogeneity exits between parasites derived from human infections and the pre-mosquito strain, implying that the malaria parasites undergo a change in functional state to adapt to its host environment. Our work also highlights the potential use of transcriptomics data from CHMI study advance our understanding of malaria parasite adaptation and transmission in humans. FUND: This work is supported by German Israeli Foundation, German ministry for education and research, MOE Tier 1 from the Singapore Ministry of Education Academic Research Fund, Singapore Ministry of Health's National Medical Research Council, National Institute of Allergy and Infectious Diseases, National Institutes of Health, USA and the German Centre for Infection Research (Deutsches Zentrum für Infektionsforschung-DZIF).
Collapse
Affiliation(s)
- Regina Hoo
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Ellen Bruske
- Institute of Tropical Medicine, Wilhelmstr. 27, University of Tübingen, 72074 Tübingen, Germany
| | - Sandra Dimonte
- Institute of Tropical Medicine, Wilhelmstr. 27, University of Tübingen, 72074 Tübingen, Germany
| | - Lei Zhu
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, Wilhelmstr. 27, University of Tübingen, 72074 Tübingen, Germany; German Center for Infection Research, partner site Tübingen, Germany
| | - B Kim Lee Sim
- Sanaria Inc, 9800 Medical Center Dr A209, Rockville, MD 20850, USA
| | - Peter G Kremsner
- Institute of Tropical Medicine, Wilhelmstr. 27, University of Tübingen, 72074 Tübingen, Germany; Centre de Recherches Médicales de Lambaréné, BP 242 Lambaréné, Gabon
| | | | - Zbynek Bozdech
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Matthias Frank
- Institute of Tropical Medicine, Wilhelmstr. 27, University of Tübingen, 72074 Tübingen, Germany.
| | - Peter R Preiser
- School of Biological Sciences, Nanyang Technological University, Singapore.
| |
Collapse
|
17
|
Olsen RW, Ecklu-Mensah G, Bengtsson A, Ofori MF, Kusi KA, Koram KA, Hviid L, Adams Y, Jensen ATR. Acquisition of IgG to ICAM-1-Binding DBLβ Domains in the Plasmodium falciparum Erythrocyte Membrane Protein 1 Antigen Family Varies between Groups A, B, and C. Infect Immun 2019; 87:e00224-19. [PMID: 31308082 PMCID: PMC6759304 DOI: 10.1128/iai.00224-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 07/03/2019] [Indexed: 12/31/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is an important malaria virulence factor. The protein family can be divided into clinically relevant subfamilies. ICAM-1-binding group A PfEMP1 proteins also bind endothelial protein C receptor and have been associated with cerebral malaria in children. IgG to these PfEMP1 proteins is acquired later in life than that to group A PfEMP1 not binding ICAM-1. The kinetics of acquisition of IgG to group B and C PfEMP1 proteins binding ICAM-1 is unclear and was studied here. Gene sequences encoding group B and C PfEMP1 with DBLβ domains known to bind ICAM-1 were used to identify additional binders. Levels of IgG specific for DBLβ domains from group A, B, and C PfEMP1 binding or not binding ICAM-1 were measured in plasma from Ghanaian children with or without malaria. Seven new ICAM-1-binding DBLβ domains from group B and C PfEMP1 were identified. Healthy children had higher levels of IgG specific for ICAM-1-binding DBLβ domains from group A than from groups B and C. However, the opposite pattern was found in children with malaria, particularly among young patients. Acquisition of IgG specific for DBLβ domains binding ICAM-1 differs between PfEMP1 groups.
Collapse
MESH Headings
- Antibodies, Protozoan/biosynthesis
- Child
- Child, Preschool
- Erythrocytes/immunology
- Erythrocytes/parasitology
- Female
- Gene Expression
- Ghana
- Humans
- Immunoglobulin G/biosynthesis
- Infant
- Intercellular Adhesion Molecule-1/genetics
- Intercellular Adhesion Molecule-1/immunology
- Malaria, Cerebral/genetics
- Malaria, Cerebral/immunology
- Malaria, Cerebral/parasitology
- Malaria, Cerebral/pathology
- Malaria, Falciparum/genetics
- Malaria, Falciparum/immunology
- Malaria, Falciparum/parasitology
- Malaria, Falciparum/pathology
- Male
- Plasmodium falciparum/immunology
- Plasmodium falciparum/pathogenicity
- Polymorphism, Genetic
- Protein Binding
- Protein Domains
- Protozoan Proteins/classification
- Protozoan Proteins/genetics
- Protozoan Proteins/immunology
- Seasons
- Severity of Illness Index
Collapse
Affiliation(s)
- Rebecca W Olsen
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Gertrude Ecklu-Mensah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Anja Bengtsson
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael F Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Kwadwo A Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Kwadwo A Koram
- Department of Epidemiology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Lars Hviid
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Yvonne Adams
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anja T R Jensen
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
18
|
Bennink S, Pradel G. The molecular machinery of translational control in malaria parasites. Mol Microbiol 2019; 112:1658-1673. [PMID: 31531994 DOI: 10.1111/mmi.14388] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2019] [Indexed: 12/30/2022]
Abstract
Translational control regulates the levels of protein synthesized from its transcript and is key for the rapid adjustment of gene expression in response to environmental stimuli. The regulation of translation is of special importance for malaria parasites, which pass through a complex life cycle that includes various replication phases in the different organs of the human and mosquito hosts and a sexual reproduction phase in the mosquito midgut. In particular, the quiescent transmission stages rely on translational control to rapidly adapt to the new environment, once they switch over from the human to the mosquito and vice versa. Three control mechanisms are currently proposed in Plasmodium, (1) global regulation that acts on the translation initiation complex; (2) mRNA-specific regulation, involving cis control elements, mRNA-binding proteins and translational repressors; and (3) induced mRNA decay by the Ccr4-Not and the RNA exosome complex. The main molecules controlling translation are highly conserved in malaria parasites and an increasing number of studies shed light on the interwoven pathways leading to the up or downregulation of protein synthesis in the diverse plasmodial stages. We here highlight recent findings on translational control during life cycle progression of Plasmodium and discuss the molecules involved in regulating protein synthesis.
Collapse
Affiliation(s)
- Sandra Bennink
- Division of Cellular and Applied Infection Biology, Institute of Zoology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Gabriele Pradel
- Division of Cellular and Applied Infection Biology, Institute of Zoology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| |
Collapse
|
19
|
Bachmann A, Bruske E, Krumkamp R, Turner L, Wichers JS, Petter M, Held J, Duffy MF, Sim BKL, Hoffman SL, Kremsner PG, Lell B, Lavstsen T, Frank M, Mordmüller B, Tannich E. Controlled human malaria infection with Plasmodium falciparum demonstrates impact of naturally acquired immunity on virulence gene expression. PLoS Pathog 2019; 15:e1007906. [PMID: 31295334 PMCID: PMC6650087 DOI: 10.1371/journal.ppat.1007906] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 07/23/2019] [Accepted: 06/10/2019] [Indexed: 12/14/2022] Open
Abstract
The pathogenesis of Plasmodium falciparum malaria is linked to the variant surface antigen PfEMP1, which mediates tethering of infected erythrocytes to the host endothelium and is encoded by approximately 60 var genes per parasite genome. Repeated episodes of malaria infection result in the gradual acquisition of protective antibodies against PfEMP1 variants. The antibody repertoire is believed to provide a selective pressure driving the clonal expansion of parasites expressing unrecognized PfEMP1 variants, however, due to the lack of experimental in vivo models there is only limited experimental evidence in support of this concept. To get insight into the impact of naturally acquired immunity on the expressed var gene repertoire early during infection we performed controlled human malaria infections of 20 adult African volunteers with life-long malaria exposure using aseptic, purified, cryopreserved P. falciparum sporozoites (Sanaria PfSPZ Challenge) and correlated serological data with var gene expression patterns from ex vivo parasites. Among the 10 African volunteers who developed patent infections, individuals with low antibody levels showed a steep rise in parasitemia accompanied by broad activation of multiple, predominantly subtelomeric var genes, similar to what we previously observed in naïve volunteers. In contrast, individuals with intermediate antibody levels developed asymptomatic infections and the ex vivo parasite populations expressed only few var gene variants, indicative of clonal selection. Importantly, in contrast to parasites from naïve volunteers, expression of var genes coding for endothelial protein C receptor (EPCR)-binding PfEMP1 that are associated with severe childhood malaria was rarely detected in semi-immune adult African volunteers. Moreover, we followed var gene expression for up to six parasite replication cycles and demonstrated for the first time in vivo a shift in the dominant var gene variant. In conclusion, our data suggest that P. falciparum activates multiple subtelomeric var genes at the onset of blood stage infection facilitating rapid expansion of parasite clones which express PfEMP1 variants unrecognized by the host's immune system, thus promoting overall parasite survival in the face of host immunity.
Collapse
Affiliation(s)
- Anna Bachmann
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
| | - Ellen Bruske
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Ralf Krumkamp
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
- Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Louise Turner
- Centre for Medical Parasitology, University of Copenhagen, Copenhagen K, Denmark
| | - J. Stephan Wichers
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Michaela Petter
- Mikrobiologisches Institut–Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany
- School of BioSciences, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Jana Held
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Michael F. Duffy
- School of BioSciences, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | | | | | - Peter G. Kremsner
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Bertrand Lell
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon
- German Center for Infection Research (DZIF), African partner institution, CERMEL, Gabon
| | - Thomas Lavstsen
- Centre for Medical Parasitology, University of Copenhagen, Copenhagen K, Denmark
| | - Matthias Frank
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Egbert Tannich
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
| |
Collapse
|
20
|
Quintana MDP, Ecklu-Mensah G, Tcherniuk SO, Ditlev SB, Oleinikov AV, Hviid L, Lopez-Perez M. Comprehensive analysis of Fc-mediated IgM binding to the Plasmodium falciparum erythrocyte membrane protein 1 family in three parasite clones. Sci Rep 2019; 9:6050. [PMID: 30988351 PMCID: PMC6465264 DOI: 10.1038/s41598-019-42585-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/03/2019] [Indexed: 12/14/2022] Open
Abstract
PfEMP1 is a family of adhesive proteins expressed on the surface of Plasmodium falciparum-infected erythrocytes (IEs), where they mediate adhesion of IEs to a range of host receptors. Efficient PfEMP1-dependent IE sequestration often depends on soluble serum proteins, including IgM. Here, we report a comprehensive investigation of which of the about 60 var gene-encoded PfEMP1 variants per parasite genome can bind IgM via the Fc part of the antibody molecule, and which of the constituent domains of those PfEMP1 are involved. We erased the epigenetic memory of var gene expression in three distinct P. falciparum clones, 3D7, HB3, and IT4/FCR3 by promoter titration, and then isolated individual IEs binding IgM from malaria-unexposed individuals by fluorescence-activated single-cell sorting. The var gene transcription profiles of sub-clones measured by real-time qPCR were used to identify potential IgM-binding PfEMP1 variants. Recombinant DBL and CIDR domains corresponding to those variants were tested by ELISA and protein arrays to confirm their IgM-binding capacity. Selected DBL domains were used to raise specific rat anti-sera to select IEs with uniform expression of candidate PfEMP1 proteins. Our data document that IgM-binding PfEMP1 proteins are common in each of the three clones studied, and that the binding epitopes are mainly found in DBLε and DBLζ domains near the C-terminus.
Collapse
Affiliation(s)
- Maria Del Pilar Quintana
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Gertrude Ecklu-Mensah
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Sergey O Tcherniuk
- Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, USA
| | - Sisse Bolm Ditlev
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Andrew V Oleinikov
- Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL, USA
| | - Lars Hviid
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. .,Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark.
| | - Mary Lopez-Perez
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
21
|
Galinski MR, Lapp SA, Peterson MS, Ay F, Joyner CJ, LE Roch KG, Fonseca LL, Voit EO. Plasmodium knowlesi: a superb in vivo nonhuman primate model of antigenic variation in malaria. Parasitology 2018; 145:85-100. [PMID: 28712361 PMCID: PMC5798396 DOI: 10.1017/s0031182017001135] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/03/2017] [Accepted: 06/06/2017] [Indexed: 02/08/2023]
Abstract
Antigenic variation in malaria was discovered in Plasmodium knowlesi studies involving longitudinal infections of rhesus macaques (M. mulatta). The variant proteins, known as the P. knowlesi Schizont Infected Cell Agglutination (SICA) antigens and the P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) antigens, expressed by the SICAvar and var multigene families, respectively, have been studied for over 30 years. Expression of the SICA antigens in P. knowlesi requires a splenic component, and specific antibodies are necessary for variant antigen switch events in vivo. Outstanding questions revolve around the role of the spleen and the mechanisms by which the expression of these variant antigen families are regulated. Importantly, the longitudinal dynamics and molecular mechanisms that govern variant antigen expression can be studied with P. knowlesi infection of its mammalian and vector hosts. Synchronous infections can be initiated with established clones and studied at multi-omic levels, with the benefit of computational tools from systems biology that permit the integration of datasets and the design of explanatory, predictive mathematical models. Here we provide an historical account of this topic, while highlighting the potential for maximizing the use of P. knowlesi - macaque model systems and summarizing exciting new progress in this area of research.
Collapse
Affiliation(s)
- M R Galinski
- Emory Vaccine Center,Yerkes National Primate Research Center,Emory University,Atlanta,GA,USA
| | - S A Lapp
- Emory Vaccine Center,Yerkes National Primate Research Center,Emory University,Atlanta,GA,USA
| | - M S Peterson
- Emory Vaccine Center,Yerkes National Primate Research Center,Emory University,Atlanta,GA,USA
| | - F Ay
- La Jolla Institute for Allergy and Immunology,La Jolla,CA 92037,USA
| | - C J Joyner
- Emory Vaccine Center,Yerkes National Primate Research Center,Emory University,Atlanta,GA,USA
| | - K G LE Roch
- Department of Cell Biology & Neuroscience,Center for Disease and Vector Research,Institute for Integrative Genome Biology,University of California Riverside,CA 92521,USA
| | - L L Fonseca
- The Wallace H. Coulter Department of Biomedical Engineering,Georgia Institute of Technology and Emory University,Atlanta,Georgia,30332-2000,USA
| | - E O Voit
- The Wallace H. Coulter Department of Biomedical Engineering,Georgia Institute of Technology and Emory University,Atlanta,Georgia,30332-2000,USA
| |
Collapse
|
22
|
Towards an anti-disease malaria vaccine. Emerg Top Life Sci 2017; 1:539-545. [PMID: 33525843 PMCID: PMC7289038 DOI: 10.1042/etls20170091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Revised: 11/01/2017] [Accepted: 11/03/2017] [Indexed: 11/24/2022]
Abstract
Human infective parasites, such as those that cause malaria, are highly adapted to evade clearance by the immune system. In situations where they must maintain prolonged interactions with molecules of their host, they often use parasite surface protein families. These families are highly diverse to prevent immune recognition, and yet, to promote parasite survival, their members must retain the ability to interact with specific human receptors. One of the best understood of the parasite surface protein families is the PfEMP1 proteins of Plasmodium falciparum. These molecules cause infected erythrocytes to adhere to human receptors found on blood vessel and tissue surfaces. This protects the parasite within from clearance by the spleen and also causes symptoms of severe malaria. The PfEMP1 are exposed to the immune system during infection and are therefore excellent vaccine candidates for use in an approach to prevent severe disease. A key question, however, is whether their extensive diversity precludes them from forming components of the malaria vaccines of the future?
Collapse
|
23
|
Abstract
Controlled human malaria infection (CHMI) entails deliberate infection with malaria parasites either by mosquito bite or by direct injection of sporozoites or parasitized erythrocytes. When required, the resulting blood-stage infection is curtailed by the administration of antimalarial drugs. Inducing a malaria infection via inoculation with infected blood was first used as a treatment (malariotherapy) for neurosyphilis in Europe and the United States in the early 1900s. More recently, CHMI has been applied to the fields of malaria vaccine and drug development, where it is used to evaluate products in well-controlled early-phase proof-of-concept clinical studies, thus facilitating progression of only the most promising candidates for further evaluation in areas where malaria is endemic. Controlled infections have also been used to immunize against malaria infection. Historically, CHMI studies have been restricted by the need for access to insectaries housing infected mosquitoes or suitable malaria-infected individuals. Evaluation of vaccine and drug candidates has been constrained in these studies by the availability of a limited number of Plasmodium falciparum isolates. Recent advances have included cryopreservation of sporozoites, the manufacture of well-characterized and genetically distinct cultured malaria cell banks for blood-stage infection, and the availability of Plasmodium vivax-specific reagents. These advances will help to accelerate malaria vaccine and drug development by making the reagents for CHMI more widely accessible and also enabling a more rigorous evaluation with multiple parasite strains and species. Here we discuss the different applications of CHMI, recent advances in the use of CHMI, and ongoing challenges for consideration.
Collapse
|
24
|
Chan JA, Stanisic DI, Duffy MF, Robinson LJ, Lin E, Kazura JW, King CL, Siba PM, Fowkes FJ, Mueller I, Beeson JG. Patterns of protective associations differ for antibodies to P. falciparum-infected erythrocytes and merozoites in immunity against malaria in children. Eur J Immunol 2017; 47:2124-2136. [PMID: 28833064 DOI: 10.1002/eji.201747032] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/09/2017] [Accepted: 08/16/2017] [Indexed: 11/10/2022]
Abstract
Acquired antibodies play an important role in immunity to P. falciparum malaria and are typically directed towards surface antigens expressed by merozoites and infected erythrocytes (IEs). The importance of specific IE surface antigens as immune targets remains unclear. We evaluated antibodies and protective associations in two cohorts of children in Papua New Guinea. We used genetically-modified P. falciparum to evaluate the importance of PfEMP1 and a P. falciparum isolate with a virulent phenotype. Our findings suggested that PfEMP1 was the dominant target of antibodies to the IE surface, including functional antibodies that promoted opsonic phagocytosis by monocytes. Antibodies were associated with increasing age and concurrent parasitemia, and were higher among children exposed to a higher force-of-infection as determined using molecular detection. Antibodies to IE surface antigens were consistently associated with reduced risk of malaria in both younger and older children. However, protective associations for antibodies to merozoite surface antigens were only observed in older children. This suggests that antibodies to IE surface antigens, particularly PfEMP1, play an earlier role in acquired immunity to malaria, whereas greater exposure is required for protective antibodies to merozoite antigens. These findings have implications for vaccine design and serosurveillance of malaria transmission and immunity.
Collapse
Affiliation(s)
- Jo-Anne Chan
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Danielle I Stanisic
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Michael F Duffy
- Department of Medicine and Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia
| | - Leanne J Robinson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Enmoore Lin
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - James W Kazura
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
| | - Christopher L King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
| | - Peter M Siba
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Freya Ji Fowkes
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Epidemiology and Preventive Medicine and Department of Infectious Diseases, Monash University, Melbourne, Victoria, Australia
| | - Ivo Mueller
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - James G Beeson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Department of Medicine and Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Microbiology, Monash University, Melbourne, Victoria, Australia
| |
Collapse
|
25
|
Knockdown of the Plasmodium falciparum SURFIN4.1 antigen leads to an increase of its cognate transcript. PLoS One 2017; 12:e0183129. [PMID: 28800640 PMCID: PMC5553854 DOI: 10.1371/journal.pone.0183129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/31/2017] [Indexed: 11/24/2022] Open
Abstract
The genome of the malaria parasite Plasmodium falciparum contains the surf gene family which encodes large transmembrane proteins of unknown function. While some surf alleles appear to be expressed in sexual stages, others occur in asexual blood stage forms and may be associated to virulence-associated processes and undergo transcriptional switching. We accessed the transcription of surf genes along multiple invasions by real time PCR. Based on the observation of persistent expression of gene surf4.1, we created a parasite line which expresses a conditionally destabilized SURFIN4.1 protein. Upon destabilization of the protein, no interference of parasite growth or morphological changes were detected. However, we observed a strong increase in the transcript quantities of surf4.1 and sometimes of other surf genes in knocked-down parasites. While this effect was reversible when SURFIN4.1 was stabilized again after a few days of destabilization, longer destabilization periods resulted in a transcriptional switch away from surf4.1. When we tested if a longer transcript half-life was responsible for increased transcript detection in SURFIN4.1 knocked-down parasites, no alteration was found compared to control parasite lines. This suggests a specific feedback of the expressed SURFIN protein to its transcript pointing to a novel type of regulation, inedited in Plasmodium.
Collapse
|
26
|
CRISPR/Cas9 Genome Editing Reveals That the Intron Is Not Essential for var2csa Gene Activation or Silencing in Plasmodium falciparum. mBio 2017; 8:mBio.00729-17. [PMID: 28698275 PMCID: PMC5513710 DOI: 10.1128/mbio.00729-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasmodium falciparum relies on monoallelic expression of 1 of 60 var virulence genes for antigenic variation and host immune evasion. Each var gene contains a conserved intron which has been implicated in previous studies in both activation and repression of transcription via several epigenetic mechanisms, including interaction with the var promoter, production of long noncoding RNAs (lncRNAs), and localization to repressive perinuclear sites. However, functional studies have relied primarily on artificial expression constructs. Using the recently developed P. falciparum clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, we directly deleted the var2csa P. falciparum 3D7_1200600 (Pf3D7_1200600) endogenous intron, resulting in an intronless var gene in a natural, marker-free chromosomal context. Deletion of the var2csa intron resulted in an upregulation of transcription of the var2csa gene in ring-stage parasites and subsequent expression of the PfEMP1 protein in late-stage parasites. Intron deletion did not affect the normal temporal regulation and subsequent transcriptional silencing of the var gene in trophozoites but did result in increased rates of var gene switching in some mutant clones. Transcriptional repression of the intronless var2csa gene could be achieved via long-term culture or panning with the CD36 receptor, after which reactivation was possible with chondroitin sulfate A (CSA) panning. These data suggest that the var2csa intron is not required for silencing or activation in ring-stage parasites but point to a subtle role in regulation of switching within the var gene family.IMPORTANCEPlasmodium falciparum is the most virulent species of malaria parasite, causing high rates of morbidity and mortality in those infected. Chronic infection depends on an immune evasion mechanism termed antigenic variation, which in turn relies on monoallelic expression of 1 of ~60 var genes. Understanding antigenic variation and the transcriptional regulation of monoallelic expression is important for developing drugs and/or vaccines. The var gene family encodes the antigenic surface proteins that decorate infected erythrocytes. Until recently, studying the underlying genetic elements that regulate monoallelic expression in P. falciparum was difficult, and most studies relied on artificial systems such as episomal reporter genes. Our study was the first to use CRISPR/Cas9 genome editing for the functional study of an important, conserved genetic element of var genes-the intron-in an endogenous, episome-free manner. Our findings shed light on the role of the var gene intron in transcriptional regulation of monoallelic expression.
Collapse
|
27
|
Bruske EI, Dimonte S, Enderes C, Tschan S, Flötenmeyer M, Koch I, Berger J, Kremsner P, Frank M. In Vitro Variant Surface Antigen Expression in Plasmodium falciparum Parasites from a Semi-Immune Individual Is Not Correlated with Var Gene Transcription. PLoS One 2016; 11:e0166135. [PMID: 27907004 PMCID: PMC5132323 DOI: 10.1371/journal.pone.0166135] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 10/24/2016] [Indexed: 12/17/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is considered to be the main variant surface antigen (VSA) of Plasmodium falciparum and is mainly localized on electron-dense knobs in the membrane of the infected erythrocyte. Switches in PfEMP1 expression provide the basis for antigenic variation and are thought to be critical for parasite persistence during chronic infections. Recently, strain transcending anti-PfEMP1 immunity has been shown to develop early in life, challenging the role of PfEMP1 in antigenic variation during chronic infections. In this work we investigate how P. falciparum achieves persistence during a chronic asymptomatic infection. The infected individual (MOA) was parasitemic for 42 days and multilocus var gene genotyping showed persistence of the same parasite population throughout the infection. Parasites from the beginning of the infection were adapted to tissue culture and cloned by limiting dilution. Flow cytometry using convalescent serum detected a variable surface recognition signal on isogenic clonal parasites. Quantitative real-time PCR with a field isolate specific var gene primer set showed that the surface recognition signal was not correlated with transcription of individual var genes. Strain transcending anti-PfEMP1 immunity of the convalescent serum was demonstrated with CD36 selected and PfEMP1 knock-down NF54 clones. In contrast, knock-down of PfEMP1 did not have an effect on the antibody recognition signal in MOA clones. Trypsinisation of the membrane surface proteins abolished the surface recognition signal and immune electron microscopy revealed that antibodies from the convalescent serum bound to membrane areas without knobs and with knobs. Together the data indicate that PfEMP1 is not the main variable surface antigen during a chronic infection and suggest a role for trypsin sensitive non-PfEMP1 VSAs for parasite persistence in chronic infections.
Collapse
Affiliation(s)
- Ellen Inga Bruske
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Sandra Dimonte
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Corinna Enderes
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Serena Tschan
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Peter Kremsner
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
| | - Matthias Frank
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
- * E-mail:
| |
Collapse
|
28
|
Immune activation and induction of memory: lessons learned from controlled human malaria infection with Plasmodium falciparum. Parasitology 2016; 143:224-35. [PMID: 26864135 DOI: 10.1017/s0031182015000761] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Controlled human malaria infections (CHMIs) are a powerful tool to assess the efficacy of drugs and/or vaccine candidates, but also to study anti-malarial immune responses at well-defined time points after infection. In this review, we discuss the insights that CHMI trials have provided into early immune activation and regulation during acute infection, and the capacity to induce and maintain immunological memory. Importantly, these studies show that a single infection is sufficient to induce long-lasting parasite-specific T- and B-cell memory responses, and suggest that blood-stage induced regulatory responses can limit inflammation both in ongoing and potentially future infections. As future perspective of investigation in CHMIs, we discuss the role of innate cell subsets, the interplay between innate and adaptive immune activation and the potential modulation of these responses after natural pre-exposure.
Collapse
|
29
|
Jackson AP. Gene family phylogeny and the evolution of parasite cell surfaces. Mol Biochem Parasitol 2016; 209:64-75. [DOI: 10.1016/j.molbiopara.2016.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/18/2016] [Accepted: 03/19/2016] [Indexed: 11/30/2022]
|
30
|
Dimonte S, Bruske EI, Hass J, Supan C, Salazar CL, Held J, Tschan S, Esen M, Flötenmeyer M, Koch I, Berger J, Bachmann A, Sim BKL, Hoffman SL, Kremsner PG, Mordmüller B, Frank M. Sporozoite Route of Infection Influences In Vitro var Gene Transcription of Plasmodium falciparum Parasites From Controlled Human Infections. J Infect Dis 2016; 214:884-94. [PMID: 27279526 DOI: 10.1093/infdis/jiw225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/19/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Antigenic variation in Plasmodium falciparum is mediated by the multicopy var gene family. Each parasite possesses about 60 var genes, and switching between active var loci results in antigenic variation. In the current study, the effect of mosquito and host passage on in vitro var gene transcription was investigated. METHODS Thirty malaria-naive individuals were inoculated by intradermal or intravenous injection with cryopreserved, isogenic NF54 P. falciparum sporozoites (PfSPZ) generated from 1 premosquito culture. Microscopic parasitemia developed in 22 individuals, and 21 in vitro cultures were established. The var gene transcript levels were determined in early and late postpatient cultures and in the premosquito culture. RESULTS At the early time point, all cultures preferentially transcribed 8 subtelomeric var genes. Intradermal infections had higher var gene transcript levels than intravenous infections and a significantly longer intrahost replication time (P = .03). At the late time point, 9 subtelomeric and 8 central var genes were transcribed at the same levels in almost all cultures. Premosquito and late postpatient cultures transcribed the same subtelomeric and central var genes, except for var2csa CONCLUSIONS The duration of intrahost replication influences in vitro var gene transcript patterns. Differences between premosquito and postpatient cultures decrease with prolonged in vitro growth.
Collapse
Affiliation(s)
- Sandra Dimonte
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Ellen I Bruske
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Johanna Hass
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Christian Supan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Carmen L Salazar
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Jana Held
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Serena Tschan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Meral Esen
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tübingen
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tübingen
| | - Anna Bachmann
- Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | | | | | - Peter G Kremsner
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen Centre de Recherches Médicales de Lambaréné (CERMEL), Fondation Internationale de l'Hôpital Albert Schweitzer, Lambaréné, Gabon
| | - Benjamin Mordmüller
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Matthias Frank
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| |
Collapse
|
31
|
Duffy MF, Noviyanti R, Tsuboi T, Feng ZP, Trianty L, Sebayang BF, Takashima E, Sumardy F, Lampah DA, Turner L, Lavstsen T, Fowkes FJI, Siba P, Rogerson SJ, Theander TG, Marfurt J, Price RN, Anstey NM, Brown GV, Papenfuss AT. Differences in PfEMP1s recognized by antibodies from patients with uncomplicated or severe malaria. Malar J 2016; 15:258. [PMID: 27149991 PMCID: PMC4858840 DOI: 10.1186/s12936-016-1296-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 04/15/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variants are encoded by var genes and mediate pathogenic cytoadhesion and antigenic variation in malaria. PfEMP1s can be broadly divided into three principal groups (A, B and C) and they contain conserved arrangements of functional domains called domain cassettes. Despite their tremendous diversity there is compelling evidence that a restricted subset of PfEMP1s is expressed in severe disease. In this study antibodies from patients with severe and uncomplicated malaria were compared for differences in reactivity with a range of PfEMP1s to determine whether antibodies to particular PfEMP1 domains were associated with severe or uncomplicated malaria. METHODS Parts of expressed var genes in a severe malaria patient were identified by RNAseq and several of these partial PfEMP1 domains were expressed together with others from laboratory isolates. Antibodies from Papuan patients to these parts of multiple PfEMP1 proteins were measured. RESULTS Patients with uncomplicated malaria were more likely to have antibodies that recognized PfEMP1 of Group C type and recognized a broader repertoire of group A and B PfEMP1s than patients with severe malaria. CONCLUSION These data suggest that exposure to a broad range of group A and B PfEMP1s is associated with protection from severe disease in Papua, Indonesia.
Collapse
Affiliation(s)
- Michael F. Duffy
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Rintis Noviyanti
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Takafumi Tsuboi
- />Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Ehime Japan
| | - Zhi-Ping Feng
- />Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- />Department of Medical Biology, University of Melbourne, Parkville, Victoria Australia
| | - Leily Trianty
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Boni F. Sebayang
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Eizo Takashima
- />Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Ehime Japan
| | - Fransisca Sumardy
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Daniel A. Lampah
- />Timika Malaria Research Program, Papuan Health and Community Development Foundation, Timika, Papua Indonesia
| | - Louise Turner
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Lavstsen
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | | | - Peter Siba
- />The Papua New Guinea Institute for Medical Research, Madang, Papua New Guinea
| | - Stephen J. Rogerson
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Thor G. Theander
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | - Jutta Marfurt
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
| | - Ric N. Price
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Nicholas M. Anstey
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
| | - Graham V. Brown
- />The Nossal Institute for Global Health, The University of Melbourne, Parkville, Victoria Australia
| | - Anthony T. Papenfuss
- />Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- />Department of Medical Biology, University of Melbourne, Parkville, Victoria Australia
- />Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- />Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria Australia
| |
Collapse
|
32
|
Arnot DE, Jensen ATR. Antigenic Variation and the Genetics and Epigenetics of the PfEMP1 Erythrocyte Surface Antigens in Plasmodium falciparum Malaria. ADVANCES IN APPLIED MICROBIOLOGY 2016; 74:77-96. [PMID: 21459194 DOI: 10.1016/b978-0-12-387022-3.00007-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
How immunity to malaria develops remains one of the great unresolved issues in bio-medicine and resolution of its various paradoxes is likely to be the key to developing effective malaria vaccines. The basic epidemiological observations are; under conditions of intense natural transmission, humans do become immune to P. falciparum malaria, but this is a slow process requiring multiple disease episodes which many, particularly young children, do not survive. Adult survivors are immune to the symptoms of malaria, and unless pregnant, can control the growth of most or all new inoculations. Sterile immunity is not achieved and chronic parasitization of apparently healthy adults is the norm. In this article, we analyse the best understood malaria "antigenic variation" system, that based on Plasmodium falciparum's PfEMP1-type cytoadhesion antigens, and critically review recent literature on the function and control of this multi-gene family of parasite variable surface antigens.
Collapse
Affiliation(s)
- David E Arnot
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, CSS Oester Farimagsgade 5, Copenhagen K, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), CSS Oester Farimagsgade 5, Copenhagen K, Denmark; Institute of Immunology and Infection Research, School of Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | | |
Collapse
|
33
|
Mosquito Passage Dramatically Changes var Gene Expression in Controlled Human Plasmodium falciparum Infections. PLoS Pathog 2016; 12:e1005538. [PMID: 27070311 PMCID: PMC4829248 DOI: 10.1371/journal.ppat.1005538] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/10/2016] [Indexed: 11/19/2022] Open
Abstract
Virulence of the most deadly malaria parasite Plasmodium falciparum is linked to the variant surface antigen PfEMP1, which is encoded by about 60 var genes per parasite genome. Although the expression of particular variants has been associated with different clinical outcomes, little is known about var gene expression at the onset of infection. By analyzing controlled human malaria infections via quantitative real-time PCR, we show that parasite populations from 18 volunteers expressed virtually identical transcript patterns that were dominated by the subtelomeric var gene group B and, to a lesser extent, group A. Furthermore, major changes in composition and frequency of var gene transcripts were detected between the parental parasite culture that was used to infect mosquitoes and Plasmodia recovered from infected volunteers, suggesting that P. falciparum resets its var gene expression during mosquito passage and starts with the broad expression of a specific subset of var genes when entering the human blood phase.
Collapse
|
34
|
Childs LM, Buckee CO. Dissecting the determinants of malaria chronicity: why within-host models struggle to reproduce infection dynamics. J R Soc Interface 2015; 12:20141379. [PMID: 25673299 PMCID: PMC4345506 DOI: 10.1098/rsif.2014.1379] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The duration of infection is fundamental to the epidemiological behaviour of any infectious disease, but remains one of the most poorly understood aspects of malaria. In endemic areas, the malaria parasite Plasmodium falciparum can cause both acute, severe infections and asymptomatic, chronic infections through its interaction with the host immune system. Frequent superinfection and massive parasite genetic diversity make it extremely difficult to accurately measure the distribution of infection lengths, complicating the estimation of basic epidemiological parameters and the prediction of the impact of interventions. Mathematical models have qualitatively reproduced parasite dynamics early during infection, but reproducing long-lived chronic infections remains much more challenging. Here, we construct a model of infection dynamics to examine the consequences of common biological assumptions for the generation of chronicity and the impact of co-infection. We find that although a combination of host and parasite heterogeneities are capable of generating chronic infections, they do so only under restricted parameter choices. Furthermore, under biologically plausible assumptions, co-infection of parasite genotypes can alter the course of infection of both the resident and co-infecting strain in complex non-intuitive ways. We outline the most important puzzles for within-host models of malaria arising from our analysis, and their implications for malaria epidemiology and control.
Collapse
Affiliation(s)
- Lauren M Childs
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| | - Caroline O Buckee
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| |
Collapse
|
35
|
Ukaegbu UE, Zhang X, Heinberg AR, Wele M, Chen Q, Deitsch KW. A Unique Virulence Gene Occupies a Principal Position in Immune Evasion by the Malaria Parasite Plasmodium falciparum. PLoS Genet 2015; 11:e1005234. [PMID: 25993442 PMCID: PMC4437904 DOI: 10.1371/journal.pgen.1005234] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 04/21/2015] [Indexed: 12/13/2022] Open
Abstract
Mutually exclusive gene expression, whereby only one member of a multi-gene family is selected for activation, is used by the malaria parasite Plasmodium falciparum to escape the human immune system and perpetuate long-term, chronic infections. A family of genes called var encodes the chief antigenic and virulence determinant of P. falciparum malaria. var genes are transcribed in a mutually exclusive manner, with switching between active genes resulting in antigenic variation. While recent work has shed considerable light on the epigenetic basis for var gene activation and silencing, how switching is controlled remains a mystery. In particular, switching seems not to be random, but instead appears to be coordinated to result in timely activation of individual genes leading to sequential waves of antigenically distinct parasite populations. The molecular basis for this apparent coordination is unknown. Here we show that var2csa, an unusual and highly conserved var gene, occupies a unique position within the var gene switching hierarchy. Induction of switching through the destabilization of var specific chromatin using both genetic and chemical methods repeatedly led to the rapid and exclusive activation of var2csa. Additional experiments demonstrated that these represent "true" switching events and not simply de-silencing of the var2csa promoter, and that activation is limited to the unique locus on chromosome 12. Combined with translational repression of var2csa transcripts, frequent "default" switching to this locus and detection of var2csa untranslated transcripts in non-pregnant individuals, these data suggest that var2csa could play a central role in coordinating switching, fulfilling a prediction made by mathematical models derived from population switching patterns. These studies provide the first insights into the mechanisms by which var gene switching is coordinated as well as an example of how a pharmacological agent can disrupt antigenic variation in Plasmodium falciparum.
Collapse
Affiliation(s)
- Uchechi E. Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Adina R. Heinberg
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Mamadou Wele
- University of Sciences Techniques and Technologies of Bamako, Bamako, Mali
| | - Qijun Chen
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| |
Collapse
|
36
|
Hviid L, Jensen ATR. PfEMP1 - A Parasite Protein Family of Key Importance in Plasmodium falciparum Malaria Immunity and Pathogenesis. ADVANCES IN PARASITOLOGY 2015; 88:51-84. [PMID: 25911365 DOI: 10.1016/bs.apar.2015.02.004] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Plasmodium falciparum causes the most severe form of malaria and is responsible for essentially all malaria-related deaths. The accumulation in various tissues of erythrocytes infected by mature P. falciparum parasites can lead to circulatory disturbances and inflammation, and is thought to be a central element in the pathogenesis of the disease. It is mediated by the interaction of parasite ligands on the erythrocyte surface and a range of host receptor molecules in many organs and tissues. Among several proteins and protein families implicated in this process, the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of high-molecular weight and highly variable antigens appears to be the most prominent. In this chapter, we aim to provide a systematic overview of the current knowledge about these proteins, their structure, their function, how they are presented on the erythrocyte surface, and how the var genes encoding them are regulated. The role of PfEMP1 in the pathogenesis of malaria, PfEMP1-specific immune responses, and the prospect of PfEMP1-specific vaccination against malaria are also covered briefly.
Collapse
Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Anja T R Jensen
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| |
Collapse
|
37
|
Hviid L, Barfod L, Fowkes FJI. Trying to remember: immunological B cell memory to malaria. Trends Parasitol 2015; 31:89-94. [PMID: 25596801 DOI: 10.1016/j.pt.2014.12.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/16/2014] [Accepted: 12/17/2014] [Indexed: 11/17/2022]
Abstract
In areas with stable transmission of Plasmodium falciparum parasites, even partially-protective immunity to malaria is acquired only after years of exposure and several infections. It has long been speculated that malaria parasites are directly able to undermine the establishment and maintenance of immunological memory, and that the often transient antibody responses to this parasite are evidence of such a dysfunction. We propose that long-lived antibody responses may not always be a prerequisite for protection, and that antibody longevity varies in an exposure- and age-dependent manner.
Collapse
Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology at Institute for Medical Microbiology and Immunology, University of Copenhagen and Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark.
| | - Lea Barfod
- Centre for Medical Parasitology at Institute for Medical Microbiology and Immunology, University of Copenhagen and Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Freya J I Fowkes
- Macfarlane Burnet Institute of Medical Research, Melbourne, Victoria, Australia; Centre for Epidemiology and Biostatistics, University of Melbourne, Australia; Department of Epidemiology and Preventive Medicine and Department of Infectious Diseases, Monash University, Melbourne, Australia
| |
Collapse
|
38
|
Fratus ASB, Cabral FJ, Fotoran WL, Medeiros MM, Carlos BC, Martha RD, da Silva LHP, Lopes SCP, Costa FTM, Wunderlich G. Antibody recognition of Plasmodium falciparum infected red blood cells by symptomatic and asymptomatic individuals in the Brazilian Amazon. Mem Inst Oswaldo Cruz 2014; 109:598-601. [PMID: 25099336 PMCID: PMC4156453 DOI: 10.1590/0074-0276140027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 05/12/2014] [Indexed: 12/31/2022] Open
Abstract
In the Amazon Region, there is a virtual absence of severe malaria and few fatal cases of naturally occurring Plasmodium falciparum infections; this presents an intriguing and underexplored area of research. In addition to the rapid access of infected persons to effective treatment, one cause of this phenomenon might be the recognition of cytoadherent variant proteins on the infected red blood cell (IRBC) surface, including the var gene encoded P. falciparum erythrocyte membrane protein 1. In order to establish a link between cytoadherence, IRBC surface antibody recognition and the presence or absence of malaria symptoms, we phenotype-selected four Amazonian P. falciparum isolates and the laboratory strain 3D7 for their cytoadherence to CD36 and ICAM1 expressed on CHO cells. We then mapped the dominantly expressed var transcripts and tested whether antibodies from symptomatic or asymptomatic infections showed a differential recognition of the IRBC surface. As controls, the 3D7 lineages expressing severe disease-associated phenotypes were used. We showed that there was no profound difference between the frequency and intensity of antibody recognition of the IRBC-exposed P. falciparum proteins in symptomatic vs. asymptomatic infections. The 3D7 lineages, which expressed severe malaria-associated phenotypes, were strongly recognised by most, but not all plasmas, meaning that the recognition of these phenotypes is frequent in asymptomatic carriers, but is not necessarily a prerequisite to staying free of symptoms.
Collapse
Affiliation(s)
| | - Fernanda Janku Cabral
- Departamento de Parasitologia, Instituto de Ciências Biomédicas,
Universidade de São Paulo, São Paulo, SP, Brasil
| | - Wesley Luzetti Fotoran
- Departamento de Parasitologia, Instituto de Ciências Biomédicas,
Universidade de São Paulo, São Paulo, SP, Brasil
| | - Márcia Melo Medeiros
- Departamento de Parasitologia, Instituto de Ciências Biomédicas,
Universidade de São Paulo, São Paulo, SP, Brasil
| | - Bianca Cechetto Carlos
- Departamento de Parasitologia, Instituto de Ciências Biomédicas,
Universidade de São Paulo, São Paulo, SP, Brasil
| | | | | | - Stefanie Costa Pinto Lopes
- Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia,
Universidade Estadual de Campinas, Campinas, SP, Brasil
| | - Fabio Trindade Maranhão Costa
- Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia,
Universidade Estadual de Campinas, Campinas, SP, Brasil
| | - Gerhard Wunderlich
- Departamento de Parasitologia, Instituto de Ciências Biomédicas,
Universidade de São Paulo, São Paulo, SP, Brasil
| |
Collapse
|
39
|
B-cell responses to pregnancy-restricted and -unrestricted Plasmodium falciparum erythrocyte membrane protein 1 antigens in Ghanaian women naturally exposed to malaria parasites. Infect Immun 2014; 82:1860-71. [PMID: 24566620 DOI: 10.1128/iai.01514-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Protective immunity to Plasmodium falciparum malaria acquired after natural exposure is largely antibody mediated. IgG-specific P. falciparum EMP1 (PfEMP1) proteins on the infected erythrocyte surface are particularly important. The transient antibody responses and the slowly acquired protective immunity probably reflect the clonal antigenic variation and allelic polymorphism of PfEMP1. However, it is likely that other immune-evasive mechanisms are also involved, such as interference with formation and maintenance of immunological memory. We measured PfEMP1-specific antibody levels by enzyme-linked immunosorbent assay (ELISA) and memory B-cell frequencies by enzyme-linked immunosorbent spot (ELISPOT) assay in a cohort of P. falciparum-exposed nonpregnant Ghanaian women. The antigens used were a VAR2CSA-type PfEMP1 (IT4VAR04) with expression restricted to parasites infecting the placenta, as well as two commonly recognized PfEMP1 proteins (HB3VAR06 and IT4VAR60) implicated in rosetting and not pregnancy restricted. This enabled, for the first time, a direct comparison in the same individuals of immune responses specific for a clinically important parasite antigen expressed only during well-defined periods (pregnancy) to responses specific for comparable antigens expressed independent of pregnancy. Our data indicate that PfEMP1-specific B-cell memory is adequately acquired even when antigen exposure is infrequent (e.g., VAR2CSA-type PfEMP1). Furthermore, immunological memory specific for VAR2CSA-type PfEMP1 can be maintained for many years without antigen reexposure and after circulating antigen-specific IgG has disappeared. The study provides evidence that natural exposure to P. falciparum leads to formation of durable B-cell immunity to clinically important PfEMP1 antigens. This has encouraging implications for current efforts to develop PfEMP1-based vaccines.
Collapse
|
40
|
Gitau EN, Tuju J, Karanja H, Stevenson L, Requena P, Kimani E, Olotu A, Kimani D, Marsh K, Bull P, Urban BC. CD4+ T cell responses to the Plasmodium falciparum erythrocyte membrane protein 1 in children with mild malaria. THE JOURNAL OF IMMUNOLOGY 2014; 192:1753-61. [PMID: 24453249 PMCID: PMC3918862 DOI: 10.4049/jimmunol.1200547] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The immune response against the variant surface Ag Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a key component of clinical immunity against malaria. We have investigated the development and maintenance of CD4+ T cell responses to a small semiconserved area of the Duffy binding–like domain (DBL)α–domain of PfEMP1, the DBLα-tag. Young children were followed up longitudinally, and parasites and PBMCs were isolated from 35 patients presenting with an acute case of uncomplicated malaria. The DBLα-tag from the PfEMP1 dominantly expressed by the homologous parasite isolate was cloned and expressed as recombinant protein. The recombinant DBLα-tag was used to activate PBMCs collected from each acute episode and from an annual cross-sectional survey performed after the acute malaria episode. In this article, we report that CD4+ T cell responses to the homologous DBLα-tag were induced in 75% of the children at the time of the acute episode and in 62% of the children at the following cross-sectional survey on average 235 d later. Furthermore, children who had induced DBLα-tag–specific CD4+IL-4+ T cells at the acute episode remained episode free for longer than children who induced other types of CD4+ T cell responses. These results suggest that a wide range of DBLα-tag–specific CD4+ T cell responses were induced in children with mild malaria and, in the case of CD4+IL-4+ T cell responses, were associated with protection from clinical episodes.
Collapse
Affiliation(s)
- Evelyn N Gitau
- KEMRI-Wellcome Trust Collaborative Programme, Centre for Geographic Medicine Coast, 80108 Kilifi, Kenya
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Noble R, Christodoulou Z, Kyes S, Pinches R, Newbold CI, Recker M. The antigenic switching network of Plasmodium falciparum and its implications for the immuno-epidemiology of malaria. eLife 2013; 2:e01074. [PMID: 24062941 PMCID: PMC3778436 DOI: 10.7554/elife.01074] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 08/19/2013] [Indexed: 12/23/2022] Open
Abstract
Antigenic variation in the human malaria parasite Plasmodium falciparum involves sequential and mutually exclusive expression of members of the var multi-gene family and appears to follow a non-random pattern. In this study, using a detailed in vitro gene transcription analysis of the culture-adapted HB3 strain of P. falciparum, we show that antigenic switching is governed by a global activation hierarchy favouring short and highly diverse genes in central chromosomal location. Longer and more conserved genes, which have previously been associated with severe infection in immunologically naive hosts, are rarely activated, however, implying an in vivo fitness advantage possibly through adhesion-dependent survival rates. We further show that a gene’s activation rate is positively associated sequence diversity, which could offer important new insights into the evolution and maintenance of antigenic diversity in P. falciparum malaria. DOI:http://dx.doi.org/10.7554/eLife.01074.001 Our ability to acquire immunity to a disease depends on our immune system learning to recognise foreign molecules—called antigens—that are specific to the disease-causing virus, bacterium or parasite. However, some pathogens, such as the malaria-causing parasite Plasmodium falciparum, get around this defence through a process called antigenic variation. This involves the parasite switching between different antigens over the course of an infection, preventing the host immune system from learning to recognise them and leading to infections that last many weeks or even months. The main antigen in P. falciparum is a protein called PfEMP1, which is encoded by a family of genes called var (‘variable’). Var genes have evolved to be highly diverse, and different parasites have different repertoires of around 50–60 var genes. This ensures that there are a huge number of distinct variants of the PfEMP1 antigen available within the population, allowing the malaria parasite to maintain long-lasting infections and also to infect the same individuals again and again. Previous work has shown that the expression of var genes is not random, but it is not clear what determines which genes are expressed at any given time. Now, Noble et al. have performed a detailed investigation of antigenic switching in P. falciparum. Using clonal parasites, they closely monitored the expression of the entire var gene repertoire during many generations of parasite culture. They observed that although different cultures initially expressed distinct var genes, most of them ended up expressing two particular genes—var27 and var29—at high levels, indicating a hard-wired gene ‘activation hierarchy’. Noble et al. found that whenever the parasites switched antigens, var genes that were centrally located on chromosomes—such as var27 and var29—were more likely to be activated than those at the ends of chromosomes. Moreover, var genes that were highly diverse were more likely to be activated than more conserved genes: this is the first evidence linking var gene evolution with gene activation probabilities. Together, these factors gave rise to the proposed activation hierarchy, which favours genes optimised for immune evasion and aids their continued evolution and diversification. Further work is now needed to identify the molecular mechanisms that control antigenic switching and to determine whether these could represent new therapeutic targets for malaria. DOI:http://dx.doi.org/10.7554/eLife.01074.002
Collapse
Affiliation(s)
- Robert Noble
- Department of Zoology , University of Oxford , Oxford , United Kingdom
| | | | | | | | | | | |
Collapse
|
42
|
Bancells C, Deitsch KW. A molecular switch in the efficiency of translation reinitiation controls expression of var2csa, a gene implicated in pregnancy-associated malaria. Mol Microbiol 2013; 90:472-88. [PMID: 23980802 DOI: 10.1111/mmi.12379] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2013] [Indexed: 12/16/2022]
Abstract
Plasmodium falciparum malaria parasites export the protein PfEMP1 to the surface of infected erythrocytes, enabling them to adhere to receptors in the microvasculature and thereby avoid clearance by the spleen. The gene var2csa encodes the form of PfEMP1 that binds specifically within the placenta, causing pregnancy-associated malaria, and appears to not be expressed in the absence of a placenta. We previously described an upstream open reading frame (uORF) that is responsible for repression of translation of the downstream ORF (dORF) that encodes VAR2CSA, thus keeping the gene silent when parasites infect non-pregnant individuals. To elucidate the molecular mechanism by which this repression is overcome during pregnancy, we stably transformed parasites with reporter gene constructs designed to detect switches in the efficiency of dORF translation. We found that proper regulation of switching relies on two separate components, (i) active translation of the uORF and (ii) sequence-specific characteristics of the surrounding transcript, which together control the ability of the ribosome complex to reinitiate a second round of translation and thus express VAR2CSA. These results provide the first details of a molecular switch that allows parasites take advantage of the unique niche provided by the placenta.
Collapse
Affiliation(s)
- Cristina Bancells
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, USA
| | | |
Collapse
|
43
|
Laurens MB, Billingsley P, Richman A, Eappen AG, Adams M, Li T, Chakravarty S, Gunasekera A, Jacob CG, Sim BKL, Edelman R, Plowe CV, Hoffman SL, Lyke KE. Successful human infection with P. falciparum using three aseptic Anopheles stephensi mosquitoes: a new model for controlled human malaria infection. PLoS One 2013; 8:e68969. [PMID: 23874828 PMCID: PMC3712927 DOI: 10.1371/journal.pone.0068969] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 05/31/2013] [Indexed: 11/18/2022] Open
Abstract
UNLABELLED Controlled human malaria infection (CHMI) is a powerful method for assessing the efficacy of anti-malaria vaccines and drugs targeting pre-erythrocytic and erythrocytic stages of the parasite. CHMI has heretofore required the bites of 5 Plasmodium falciparum (Pf) sporozoite (SPZ)-infected mosquitoes to reliably induce Pf malaria. We reported that CHMI using the bites of 3 PfSPZ-infected mosquitoes reared aseptically in compliance with current good manufacturing practices (cGMP) was successful in 6 participants. Here, we report results from a subsequent CHMI study using 3 PfSPZ-infected mosquitoes reared aseptically to validate the initial clinical trial. We also compare results of safety, tolerability, and transmission dynamics in participants undergoing CHMI using 3 PfSPZ-infected mosquitoes reared aseptically to published studies of CHMI using 5 mosquitoes. Nineteen adults aged 18-40 years were bitten by 3 Anopheles stephensi mosquitoes infected with the chloroquine-sensitive NF54 strain of Pf. All 19 participants developed malaria (100%); 12 of 19 (63%) on Day 11. The mean pre-patent period was 258.3 hours (range 210.5-333.8). The geometric mean parasitemia at first diagnosis by microscopy was 9.5 parasites/µL (range 2-44). Quantitative polymerase chain reaction (qPCR) detected parasites an average of 79.8 hours (range 43.8-116.7) before microscopy. The mosquitoes had a geometric mean of 37,894 PfSPZ/mosquito (range 3,500-152,200). Exposure to the bites of 3 aseptically-raised, PfSPZ-infected mosquitoes is a safe, effective procedure for CHMI in malaria-naïve adults. The aseptic model should be considered as a new standard for CHMI trials in non-endemic areas. Microscopy is the gold standard used for the diagnosis of Pf malaria after CHMI, but qPCR identifies parasites earlier. If qPCR continues to be shown to be highly specific, and can be made to be practical, rapid, and standardized, it should be considered as an alternative for diagnosis. TRIAL REGISTRATION ClinicalTrials.gov NCT00744133 NCT00744133.
Collapse
Affiliation(s)
- Matthew B Laurens
- Howard Hughes Medical Institute/Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Berger SS, Turner L, Wang CW, Petersen JEV, Kraft M, Lusingu JPA, Mmbando B, Marquard AM, Bengtsson DBAC, Hviid L, Nielsen MA, Theander TG, Lavstsen T. Plasmodium falciparum expressing domain cassette 5 type PfEMP1 (DC5-PfEMP1) bind PECAM1. PLoS One 2013; 8:e69117. [PMID: 23874884 PMCID: PMC3706608 DOI: 10.1371/journal.pone.0069117] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 06/07/2013] [Indexed: 11/18/2022] Open
Abstract
Members of the Plasmodium falciparum Erythrocyte Membrane protein 1 (PfEMP1) family expressed on the surface of malaria-infected erythrocytes mediate binding of the parasite to different receptors on the vascular lining. This process drives pathologies, and severe childhood malaria has been associated with the expression of particular subsets of PfEMP1 molecules. PfEMP1 are grouped into subtypes based on upstream sequences and the presence of semi-conserved PfEMP1 domain compositions named domain cassettes (DCs). Earlier studies have indicated that DC5-containing PfEMP1 (DC5-PfEMP1) are more likely to be expressed in children with severe malaria disease than in children with uncomplicated malaria, but these PfEMP1 subtypes only dominate in a relatively small proportion of the children with severe disease. In this study, we have characterised the genomic sequence characteristic for DC5, and show that two genetically different parasite lines expressing DC5-PfEMP1 bind PECAM1, and that anti-DC5-specific antibodies inhibit binding of DC5-PfEMP1-expressing parasites to transformed human bone marrow endothelial cells (TrHBMEC). We also show that antibodies against each of the four domains characteristic for DC5 react with native PfEMP1 expressed on the surface of infected erythrocytes, and that some of these antibodies are cross-reactive between the two DC5-containing PfEMP1 molecules tested. Finally, we confirm that anti-DC5 antibodies are acquired early in life by individuals living in malaria endemic areas, that individuals having high levels of these antibodies are less likely to develop febrile malaria episodes and that the antibody levels correlate positively with hemoglobin levels.
Collapse
Affiliation(s)
- Sanne S. Berger
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
- * E-mail: (SB); (TL)
| | - Louise Turner
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Christian W. Wang
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Jens E. V. Petersen
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Maria Kraft
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - John P. A. Lusingu
- National Institute for Medical Research (NIMR), Tanga Medical Research Centre, Tanga, Tanzania
| | - Bruno Mmbando
- National Institute for Medical Research (NIMR), Tanga Medical Research Centre, Tanga, Tanzania
| | - Andrea M. Marquard
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Dominique B. A. C. Bengtsson
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Lars Hviid
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Morten A. Nielsen
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Thor G. Theander
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
| | - Thomas Lavstsen
- Centre for Medical Parasitology at Department of International Health, Immunology and Microbiology, Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
- * E-mail: (SB); (TL)
| |
Collapse
|
45
|
Johnston GL, Smith DL, Fidock DA. Malaria's missing number: calculating the human component of R0 by a within-host mechanistic model of Plasmodium falciparum infection and transmission. PLoS Comput Biol 2013; 9:e1003025. [PMID: 23637586 PMCID: PMC3630126 DOI: 10.1371/journal.pcbi.1003025] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 02/25/2013] [Indexed: 11/18/2022] Open
Abstract
Human infection by malarial parasites of the genus Plasmodium begins with the bite of an infected Anopheles mosquito. Current estimates place malaria mortality at over 650,000 individuals each year, mostly in African children. Efforts to reduce disease burden can benefit from the development of mathematical models of disease transmission. To date, however, comprehensive modeling of the parameters defining human infectivity to mosquitoes has remained elusive. Here, we describe a mechanistic within-host model of Plasmodium falciparum infection in humans and pathogen transmission to the mosquito vector. Our model incorporates the entire parasite lifecycle, including the intra-erythrocytic asexual forms responsible for disease, the onset of symptoms, the development and maturation of intra-erythrocytic gametocytes that are transmissible to Anopheles mosquitoes, and human-to-mosquito infectivity. These model components were parameterized from malaria therapy data and other studies to simulate individual infections, and the ensemble of outputs was found to reproduce the full range of patient responses to infection. Using this model, we assessed human infectivity over the course of untreated infections and examined the effects in relation to transmission intensity, expressed by the basic reproduction number R0 (defined as the number of secondary cases produced by a single typical infection in a completely susceptible population). Our studies predict that net human-to-mosquito infectivity from a single non-immune individual is on average equal to 32 fully infectious days. This estimate of mean infectivity is equivalent to calculating the human component of malarial R0. We also predict that mean daily infectivity exceeds five percent for approximately 138 days. The mechanistic framework described herein, made available as stand-alone software, will enable investigators to conduct detailed studies into theories of malaria control, including the effects of drug treatment and drug resistance on transmission. We report a new mathematical model of the progression, within a human host, of a malaria infection caused by the parasite Plasmodium falciparum. This model incorporates probability distributions for the key parameters of infection and transmission so that model outputs match the entire range of observed responses in patients, without the requirement for fitting individual data. Further, we simulate the daily densities of both the disease-causing and transmissible forms of the parasite within an individual, as well as the onset of fever and the probability of parasite transmission to mosquitoes. This model allows us to reproduce aspects of infection that are critical for malaria control modeling. As a first application, we calculate the net infectiousness of humans to mosquitoes and predict that net human infectivity from a single infection is on average equal to approximately 32 fully infectious days. This value has been used to help map the worldwide intensity of malaria transmission. We also predict that mean daily infectivity is greater than five percent for approximately 138 days. Our modeling framework, available as downloadable software, will allow researchers to probe the effects of treatment and drug resistance on malaria transmission in unprecedented detail, helping to improve malaria control efforts.
Collapse
Affiliation(s)
- Geoffrey L. Johnston
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- School of International and Public Affairs, Columbia University, New York, New York, United States of America
- Bloomberg School of Public Health, John Hopkins University, Baltimore, Maryland, United States of America
| | - David L. Smith
- Bloomberg School of Public Health, John Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (DLS); (DAF)
| | - David A. Fidock
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- Division of Infectious Diseases, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- * E-mail: (DLS); (DAF)
| |
Collapse
|
46
|
Tibúrcio M, Silvestrini F, Bertuccini L, Sander AF, Turner L, Lavstsen T, Alano P. Early gametocytes of the malaria parasite Plasmodium falciparum specifically remodel the adhesive properties of infected erythrocyte surface. Cell Microbiol 2012; 15:647-59. [PMID: 23114006 DOI: 10.1111/cmi.12062] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 10/11/2012] [Accepted: 10/24/2012] [Indexed: 11/27/2022]
Abstract
In Plasmodium falciparum infections the parasite transmission stages, the gametocytes, mature in 10 days sequestered in internal organs. Recent studies suggest that cell mechanical properties rather than adhesive interactions play a role in sequestration during gametocyte maturation. It remains instead obscure how sequestration is established, and how the earliest sexual stages, morphologically similar to asexual trophozoites, modify the infected erythrocytes and their cytoadhesive properties at the onset of gametocytogenesis. Here, purified P. falciparum early gametocytes were used to ultrastructurally and biochemically analyse parasite-induced modifications on the red blood cell surface and to measure their functional consequences on adhesion to human endothelial cells. This work revealed that stage I gametocytes are able to deform the infected erythrocytes like asexual parasites, but do not modify its surface with adhesive 'knob' structures and associated proteins. Reduced levels of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesins are exposed on the red blood cell surface by these parasites, and the expression of the var gene family, which encodes 50-60 variants of PfEMP1, is dramatically downregulated in the transition from asexual development to gametocytogenesis. Cytoadhesion assays show that such gene expression changes and host cell surface modifications functionally result in the inability of stage I gametocytes to bind the host ligands used by the asexual parasite to bind endothelial cells. In conclusion, these results identify specific differences in molecular and cellular mechanisms of host cell remodelling and in adhesive properties, leading to clearly distinct host parasite interplays in the establishment of sequestration of stage I gametocytes and of asexual trophozoites.
Collapse
Affiliation(s)
- Marta Tibúrcio
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, viale Regina Elena 299, 00161, Rome, Italy
| | | | | | | | | | | | | |
Collapse
|
47
|
Mugasa J, Qi W, Rusch S, Rottmann M, Beck HP. Genetic diversity of expressed Plasmodium falciparum var genes from Tanzanian children with severe malaria. Malar J 2012; 11:230. [PMID: 22799500 PMCID: PMC3488018 DOI: 10.1186/1475-2875-11-230] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 07/02/2012] [Indexed: 11/17/2022] Open
Abstract
Background Severe malaria has been attributed to the expression of a restricted subset of the var multi-gene family, which encodes for Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). PfEMP1 mediates cytoadherence and sequestration of infected erythrocytes into the post-capillary venules of vital organs such as the brain, lung or placenta. var genes are highly diverse and can be classified in three major groups (ups A, B and C) and two intermediate groups (B/A and B/C) based on the genomic location, gene orientation and upstream sequences. The genetic diversity of expressed var genes in relation to severity of disease in Tanzanian children was analysed. Methods Children with defined severe (SM) and asymptomatic malaria (AM) were recruited. Full-length var mRNA was isolated and reversed transcribed into var cDNA. Subsequently, the DBL and N-terminal domains, and up-stream sequences were PCR amplified, cloned and sequenced. Sequences derived from SM and AM isolates were compared and analysed. Results The analysis confirmed that the var family is highly diverse in natural Plasmodium falciparum populations. Sequence diversity of amplified var DBL-1α and upstream regions showed minimal overlap among isolates, implying that the var gene repertoire is vast and most probably indefinite in endemic areas. var DBL-1α sequences from AM isolates were more diverse with more singletons found (p<0.05) than those from SM infections. Furthermore, few var DBL-1α sequences from SM patients were rare and restricted suggesting that certain PfEMP1 variants might induce severe disease. Conclusions The genetic sequence diversity of var genes of P. falciparum isolates from Tanzanian children is large and its relationship to disease severity has been studied. Observed differences suggest that different var genes might have fundamentally different roles in the host-parasite interaction. Further research is required to examine clear disease-associations of var gene subsets in different geographical settings. The importance of very strict clinical definitions and appropriate large control groups needs to be emphasized for future studies on disease associations of PfEMP1.
Collapse
|
48
|
Fastman Y, Noble R, Recker M, Dzikowski R. Erasing the epigenetic memory and beginning to switch--the onset of antigenic switching of var genes in Plasmodium falciparum. PLoS One 2012; 7:e34168. [PMID: 22461905 PMCID: PMC3312910 DOI: 10.1371/journal.pone.0034168] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 02/23/2012] [Indexed: 11/19/2022] Open
Abstract
Antigenic variation in Plasmodium falciparum is regulated by transcriptional switches among members of the var gene family, each expressed in a mutually exclusive manner and encoding a different variant of the surface antigens collectively named PfEMP1. Antigenic switching starts when the first merozoites egress from the liver and begin their asexual proliferation within red blood cells. By erasing the epigenetic memory we created parasites with no var background, similar to merozoites that egress from the liver where no var gene is expressed. Creating a null-var background enabled us to investigate the onset of antigenic switches at the early phase of infection. At the onset of switching, var transcription pattern is heterogeneous with numerous genes transcribed at low levels including upsA vars, a subtype that was implicated in severe malaria, which are rarely activated in growing cultures. Analysis of subsequent in vitro switches shows that the probability of a gene to turn on or off is not associated with its chromosomal position or promoter type per se but on intrinsic properties of each gene. We concluded that var switching is determined by gene specific associated switch rates rather than general promoter type or locus associated switch rates. In addition, we show that fine tuned reduction in var transcription increases their switch rate, indicating that transcriptional perturbation can alter antigenic switching.
Collapse
Affiliation(s)
- Yair Fastman
- Department of Microbiology & Molecular Genetics, The Kuvin Center for the Study of Infectious and Tropical Diseases, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Robert Noble
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Mario Recker
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Ron Dzikowski
- Department of Microbiology & Molecular Genetics, The Kuvin Center for the Study of Infectious and Tropical Diseases, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
- * E-mail:
| |
Collapse
|
49
|
Milner DA, Vareta J, Valim C, Montgomery J, Daniels RF, Volkman SK, Neafsey DE, Park DJ, Schaffner SF, Mahesh NC, Barnes KG, Rosen DM, Lukens AK, Van-Tyne D, Wiegand RC, Sabeti PC, Seydel KB, Glover SJ, Kamiza S, Molyneux ME, Taylor TE, Wirth DF. Human cerebral malaria and Plasmodium falciparum genotypes in Malawi. Malar J 2012; 11:35. [PMID: 22314206 PMCID: PMC3295736 DOI: 10.1186/1475-2875-11-35] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 02/07/2012] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Cerebral malaria, a severe form of Plasmodium falciparum infection, is an important cause of mortality in sub-Saharan African children. A Taqman 24 Single Nucleotide Polymorphisms (SNP) molecular barcode assay was developed for use in laboratory parasites which estimates genotype number and identifies the predominant genotype. METHODS The 24 SNP assay was used to determine predominant genotypes in blood and tissues from autopsy and clinical patients with cerebral malaria. RESULTS Single genotypes were shared between the peripheral blood, the brain, and other tissues of cerebral malaria patients, while malaria-infected patients who died of non-malarial causes had mixed genetic signatures in tissues examined. Children with retinopathy-positive cerebral malaria had significantly less complex infections than those without retinopathy (OR = 3.7, 95% CI [1.51-9.10]).The complexity of infections significantly decreased over the malaria season in retinopathy-positive patients compared to retinopathy-negative patients. CONCLUSIONS Cerebral malaria patients harbour a single or small set of predominant parasites; patients with incidental parasitaemia sustain infections involving diverse genotypes. Limited diversity in the peripheral blood of cerebral malaria patients and correlation with tissues supports peripheral blood samples as appropriate for genome-wide association studies of parasite determinants of pathogenicity.
Collapse
Affiliation(s)
- Danny A Milner
- Department of Pathology, Brigham and Women's Hospital, 75 Francis Street, Amory 3, Boston, MA 02115, USA
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Jimmy Vareta
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
| | - Clarissa Valim
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Jacqui Montgomery
- College of Medicine, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Liverpool School of Tropical Medicine, University of Liverpool, Liverpool, UK
| | - Rachel F Daniels
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
| | - Sarah K Volkman
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Department of Nursing, School for Health Sciences, Simmons College, Boston, MA 02115, USA
| | | | | | | | - Nira C Mahesh
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Kayla G Barnes
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - David M Rosen
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Amanda K Lukens
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | - Daria Van-Tyne
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
| | | | - Pardis C Sabeti
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
- Center for Systems Biology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Karl B Seydel
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48824, USA
| | - Simon J Glover
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Steve Kamiza
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Malcolm E Molyneux
- College of Medicine, Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Liverpool School of Tropical Medicine, University of Liverpool, Liverpool, UK
- College of Medicine, University of Malawi, Blantyre, Malawi
| | - Terrie E Taylor
- The Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi
- College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48824, USA
| | - Dyann F Wirth
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, MA 02115, USA
- Broad Institute, Cambridge, MA 02142, USA
| |
Collapse
|
50
|
Fatih FA, Siner A, Ahmed A, Woon LC, Craig AG, Singh B, Krishna S, Cox-Singh J. Cytoadherence and virulence - the case of Plasmodium knowlesi malaria. Malar J 2012; 11:33. [PMID: 22305466 PMCID: PMC3330018 DOI: 10.1186/1475-2875-11-33] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 02/03/2012] [Indexed: 12/02/2022] Open
Abstract
Background Cytoadherence of infected red blood cells to brain endothelium is causally implicated in malarial coma, one of the severe manifestations of falciparum malaria. Cytoadherence is mediated by specific binding of variant parasite antigens, expressed on the surface of infected erythrocytes, to endothelial receptors including, ICAM-1, VCAM and CD36. In fatal cases of severe falciparum malaria with coma, blood vessels in the brain are characteristically congested with infected erythrocytes. Brain sections from a fatal case of knowlesi malaria, but without coma, were similarly congested with infected erythrocytes. The objective of this study was to determine the binding phenotype of Plasmodium knowlesi infected human erythrocytes to recombinant human ICAM-1, VCAM and CD36. Methods Five patients with PCR-confirmed P. knowlesi malaria were recruited into the study with consent between April and August 2010. Pre-treatment venous blood was washed and cultured ex vivo to increase the proportion of schizont-infected erythrocytes. Cultured blood was seeded into Petri dishes with triplicate areas coated with ICAM-1, VCAM and CD36. Following incubation at 37°C for one hour the dishes were washed and the number of infected erythrocytes bound/mm2 to PBS control areas and to recombinant human ICAM-1 VCAM and CD36 coated areas were recorded. Each assay was performed in duplicate. Assay performance was monitored with the Plasmodium falciparum clone HB3. Results Blood samples were cultured ex vivo for up to 14.5 h (mean 11.3 ± 1.9 h) to increase the relative proportion of mature trophozoite and schizont-infected red blood cells to at least 50% (mean 65.8 ± 17.51%). Three (60%) isolates bound significantly to ICAM-1 and VCAM, one (20%) isolate bound to VCAM and none of the five bound significantly to CD36. Conclusions Plasmodium knowlesi infected erythrocytes from human subjects bind in a specific but variable manner to the inducible endothelial receptors ICAM-1 and VCAM. Binding to the constitutively-expressed endothelial receptor CD36 was not detected. Further work will be required to define the pathological consequences of these interactions.
Collapse
Affiliation(s)
- Farrah A Fatih
- Centre for Infection and Immunity, St George's University of London, London SW17 0RE, UK
| | | | | | | | | | | | | | | |
Collapse
|