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Freville A, Stewart LB, Tetteh KKA, Treeck M, Cortes A, Voss TS, Tarr SJ, Baker DA, Conway DJ. Expression of the MSPDBL2 antigen in a discrete subset of Plasmodium falciparum schizonts is regulated by GDV1 but may not be linked to sexual commitment. mBio 2024; 15:e0314023. [PMID: 38530030 PMCID: PMC11077968 DOI: 10.1128/mbio.03140-23] [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] [Received: 11/21/2023] [Accepted: 03/04/2024] [Indexed: 03/27/2024] Open
Abstract
The Plasmodium falciparum merozoite surface protein MSPDBL2 is a polymorphic antigen targeted by acquired immune responses, and normally expressed in only a minority of mature schizonts. The potential relationship of MSPDBL2 to sexual commitment is examined, as variable mspdbl2 transcript levels and proportions of MSPDBL2-positive mature schizonts in clinical isolates have previously correlated with levels of many sexual stage parasite gene transcripts, although not with the master regulator ap2-g. It is demonstrated that conditional overexpression of the gametocyte development protein GDV1, which promotes sexual commitment, also substantially increases the proportion of MSPDBL2-positive schizonts in culture. Conversely, truncation of the gdv1 gene is shown to prevent any expression of MSPDBL2. However, across diverse P. falciparum cultured lines, the variable proportions of MSPDBL2 positivity in schizonts do not correlate significantly with variable gametocyte conversion rates, indicating it is not involved in sexual commitment. Confirming this, examining a line with endogenous hemagglutinin-tagged AP2-G showed that the individual schizonts expressing MSPDBL2 are mostly different from those expressing AP2-G. Using a selection-linked integration system, modified P. falciparum lines were engineered to express an intact or disrupted version of MSPDBL2, showing the protein is not required for sexual commitment or early gametocyte development. Asexual parasite multiplication rates were also not affected by expression of either intact or disrupted MSPDBL2 in a majority of schizonts. Occurring alongside sexual commitment, the role of the discrete MSPDBL2-positive schizont subpopulation requires further investigation in natural infections where it is under immune selection. IMPORTANCE Malaria parasites in the blood are remarkably variable, able to switch antigenic targets so they may survive within humans who have already developed specific immune responses. This is one of the challenges in developing vaccines against malaria. MSPDBL2 is a target of naturally acquired immunity expressed in minority proportions of schizonts, the end stages of each 2-day replication cycle in red blood cells which contain merozoites prepared to invade new red blood cells. Results show that the proportion of schizonts expressing MSPDBL2 is positively controlled by the expression of the regulatory gametocyte development protein GDV1. It was previously known that expression of GDV1 leads to increased expression of AP2-G which causes parasites to switch to sexual development, so a surprising finding here is that MSPDBL2-positive parasites are mostly distinct from those that express AP2-G. This discrete antigenic subpopulation of mostly asexual parasites is regulated alongside sexually committed parasites, potentially enabling survival under stress conditions.
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Affiliation(s)
- Aline Freville
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Lindsay B. Stewart
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Kevin K. A. Tetteh
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Alfred Cortes
- ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Catalonia, Spain
- ICREA, Barcelona, Catalonia, Spain
| | - Till S. Voss
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Sarah J. Tarr
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - David A. Baker
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - David J. Conway
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
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Fola AA, He Q, Xie S, Thimmapuram J, Bhide KP, Dorman J, Ciubotariu II, Mwenda MC, Mambwe B, Mulube C, Hawela M, Norris DE, Moss WJ, Bridges DJ, Carpi G. Genomics reveals heterogeneous Plasmodium falciparum transmission and selection signals in Zambia. COMMUNICATIONS MEDICINE 2024; 4:67. [PMID: 38582941 PMCID: PMC10998850 DOI: 10.1038/s43856-024-00498-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 03/28/2024] [Indexed: 04/08/2024] Open
Abstract
BACKGROUND Genomic surveillance is crucial for monitoring malaria transmission and understanding parasite adaptation to interventions. Zambia lacks prior nationwide efforts in malaria genomic surveillance among African countries. METHODS We conducted genomic surveillance of Plasmodium falciparum parasites from the 2018 Malaria Indicator Survey in Zambia, a nationally representative household survey of children under five years of age. We whole-genome sequenced and analyzed 241 P. falciparum genomes from regions with varying levels of malaria transmission across Zambia and estimated genetic metrics that are informative about transmission intensity, genetic relatedness between parasites, and selection. RESULTS We provide genomic evidence of widespread within-host polygenomic infections, regardless of epidemiological characteristics, underscoring the extensive and ongoing endemic malaria transmission in Zambia. Our analysis reveals country-level clustering of parasites from Zambia and neighboring regions, with distinct separation in West Africa. Within Zambia, identity by descent (IBD) relatedness analysis uncovers local spatial clustering and rare cases of long-distance sharing of closely related parasite pairs. Genomic regions with large shared IBD segments and strong positive selection signatures implicate genes involved in sulfadoxine-pyrimethamine and artemisinin combination therapies drug resistance, but no signature related to chloroquine resistance. Furthermore, differences in selection signatures, including drug resistance loci, are observed between eastern and western Zambian parasite populations, suggesting variable transmission intensity and ongoing drug pressure. CONCLUSIONS Our findings enhance our understanding of nationwide P. falciparum transmission in Zambia, establishing a baseline for analyzing parasite genetic metrics as they vary over time and space. These insights highlight the urgency of strengthening malaria control programs and surveillance of antimalarial drug resistance.
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Affiliation(s)
- Abebe A Fola
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA
| | - Qixin He
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Shaojun Xie
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Jyothi Thimmapuram
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Ketaki P Bhide
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Jack Dorman
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Ilinca I Ciubotariu
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Mulenga C Mwenda
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Brenda Mambwe
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Conceptor Mulube
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Moonga Hawela
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Douglas E Norris
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - William J Moss
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - Giovanna Carpi
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
- Purdue Institute for Inflammation, Immunology, & Infectious Disease, Purdue University, West Lafayette, IN, USA.
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3
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Fola AA, He Q, Xie S, Thimmapuram J, Bhide KP, Dorman J, Ciubotariu II, Mwenda MC, Mambwe B, Mulube C, Hawela M, Norris DE, Moss WJ, Bridges DJ, Carpi G. Genomics reveals heterogeneous Plasmodium falciparum transmission and population differentiation in Zambia and bordering countries. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.02.09.24302570. [PMID: 38370674 PMCID: PMC10871455 DOI: 10.1101/2024.02.09.24302570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Genomic surveillance plays a critical role in monitoring malaria transmission and understanding how the parasite adapts in response to interventions. We conducted genomic surveillance of malaria by sequencing 241 Plasmodium falciparum genomes from regions with varying levels of malaria transmission across Zambia. We found genomic evidence of high levels of within-host polygenomic infections, regardless of epidemiological characteristics, underscoring the extensive and ongoing endemic malaria transmission in the country. We identified country-level clustering of parasites from Zambia and neighboring countries, and distinct clustering of parasites from West Africa. Within Zambia, our identity by descent (IBD) relatedness analysis uncovered spatial clustering of closely related parasite pairs at the local level and rare cases of long-distance sharing. Genomic regions with large shared IBD segments and strong positive selection signatures identified genes involved in sulfadoxine-pyrimethamine and artemisinin combination therapies drug resistance, but no signature related to chloroquine resistance. Together, our findings enhance our understanding of P. falciparum transmission nationwide in Zambia and highlight the urgency of strengthening malaria control programs and surveillance of antimalarial drug resistance.
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Affiliation(s)
- Abebe A. Fola
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Qixin He
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Shaojun Xie
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Jyothi Thimmapuram
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Ketaki P. Bhide
- Bioinformatics Core, Purdue University, Purdue University, West Lafayette, IN, USA
| | - Jack Dorman
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | | | | | - Brenda Mambwe
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Conceptor Mulube
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Moonga Hawela
- PATH-MACEPA, National Malaria Elimination Centre, Lusaka, Zambia
| | - Douglas E. Norris
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - William J. Moss
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - Giovanna Carpi
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
- The Johns Hopkins Malaria Research Institute, W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Purdue Institute for Inflammation, Immunology, & Infectious Disease, Purdue University, West Lafayette, IN, USA
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Amambua-Ngwa A, Button-Simons KA, Li X, Kumar S, Brenneman KV, Ferrari M, Checkley LA, Haile MT, Shoue DA, McDew-White M, Tindall SM, Reyes A, Delgado E, Dalhoff H, Larbalestier JK, Amato R, Pearson RD, Taylor AB, Nosten FH, D'Alessandro U, Kwiatkowski D, Cheeseman IH, Kappe SHI, Avery SV, Conway DJ, Vaughan AM, Ferdig MT, Anderson TJC. Chloroquine resistance evolution in Plasmodium falciparum is mediated by the putative amino acid transporter AAT1. Nat Microbiol 2023; 8:1213-1226. [PMID: 37169919 PMCID: PMC10322710 DOI: 10.1038/s41564-023-01377-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 03/29/2023] [Indexed: 05/13/2023]
Abstract
Malaria parasites break down host haemoglobin into peptides and amino acids in the digestive vacuole for export to the parasite cytoplasm for growth: interrupting this process is central to the mode of action of several antimalarial drugs. Mutations in the chloroquine (CQ) resistance transporter, pfcrt, located in the digestive vacuole membrane, confer CQ resistance in Plasmodium falciparum, and typically also affect parasite fitness. However, the role of other parasite loci in the evolution of CQ resistance is unclear. Here we use a combination of population genomics, genetic crosses and gene editing to demonstrate that a second vacuolar transporter plays a key role in both resistance and compensatory evolution. Longitudinal genomic analyses of the Gambian parasites revealed temporal signatures of selection on a putative amino acid transporter (pfaat1) variant S258L, which increased from 0% to 97% in frequency between 1984 and 2014 in parallel with the pfcrt1 K76T variant. Parasite genetic crosses then identified a chromosome 6 quantitative trait locus containing pfaat1 that is selected by CQ treatment. Gene editing demonstrated that pfaat1 S258L potentiates CQ resistance but at a cost of reduced fitness, while pfaat1 F313S, a common southeast Asian polymorphism, reduces CQ resistance while restoring fitness. Our analyses reveal hidden complexity in CQ resistance evolution, suggesting that pfaat1 may underlie regional differences in the dynamics of resistance evolution, and modulate parasite resistance or fitness by manipulating the balance between both amino acid and drug transport.
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Affiliation(s)
- Alfred Amambua-Ngwa
- MRC Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Katrina A Button-Simons
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Xue Li
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Sudhir Kumar
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Katelyn Vendrely Brenneman
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Marco Ferrari
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Lisa A Checkley
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Meseret T Haile
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Douglas A Shoue
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Marina McDew-White
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Sarah M Tindall
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Ann Reyes
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Elizabeth Delgado
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Haley Dalhoff
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - James K Larbalestier
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | | | | | - Alexander B Taylor
- Department of Biochemistry & Structural Biology, University of Texas Health Science Center at San Antonio, Antonio, TX, USA
| | - François H Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Umberto D'Alessandro
- MRC Unit The Gambia at London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | | | - Ian H Cheeseman
- Host Pathogen Interactions Program, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Stefan H I Kappe
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, USA
- Department of Pediatrics, University of Washington, Seattle, WA, USA
- Department of Global Health, University of Washington, Seattle, WA, USA
| | - Simon V Avery
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - David J Conway
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Ashley M Vaughan
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA, USA.
- Department of Pediatrics, University of Washington, Seattle, WA, USA.
| | - Michael T Ferdig
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
| | - Timothy J C Anderson
- Disease Intervention and Prevention Program, Texas Biomedical Research Institute, San Antonio, TX, USA.
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5
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Mbye H, Mane K, Diop MF, Demba MA, Bojang F, Mohammed NI, Jeffries D, Quashie NB, D'Alessandro U, Amambua-Ngwa A. Plasmodium falciparum merozoite invasion ligands, linked antimalarial resistance loci and ex vivo responses to antimalarials in The Gambia. J Antimicrob Chemother 2022; 77:2946-2955. [PMID: 35904009 PMCID: PMC9616547 DOI: 10.1093/jac/dkac244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 06/23/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Artemether/lumefantrine is the most commonly used artemisinin-based combination treatment (ACT) for malaria in sub-Saharan Africa. Drug resistance to ACT components is a major threat to malaria elimination efforts. Therefore, rigorous monitoring of drug efficacy is required for adequate management of malaria and to sustain the effectiveness of ACTs. OBJECTIVES This study identified and described genomic loci that correlate with differences in ex vivo responses of natural Plasmodium falciparum isolates from The Gambia to antimalarial drugs. METHODS Natural P. falciparum isolates from The Gambia were assayed for IC50 responses to four antimalarial drugs (artemether, dihydroartemisinin, amodiaquine and lumefantrine). Genome-wide SNPs from 56 of these P. falciparum isolates were applied to mixed-model regression and network analyses to determine linked loci correlating with drug responses. Genomic regions of shared haplotypes and positive selection within and between Gambian and Cambodian P. falciparum isolates were mapped by identity-by-descent (IBD) analysis of 209 genomes. RESULTS SNPs in 71 genes, mostly involved in stress and drug resistance mechanisms correlated with drug responses. Additionally, erythrocyte invasion and permeability loci, including merozoite surface proteins (Pfdblmsp, Pfsurfin), and high-molecular-weight rhoptry protein 2 (Pfrhops2) were correlated with responses to multiple drugs. Haplotypes of pfdblmsp2 and known drug resistance loci (pfaat1, pfcrt and pfdhfr) from The Gambia showed high IBD with those from Cambodia, indicating co-ancestry, with significant linkage disequilibrium between their alleles. CONCLUSIONS Multiple linked genic loci correlating with drug response phenotypes suggest a genomic backbone may be under selection by antimalarials. This calls for further analysis of molecular pathways to drug resistance in African P. falciparum.
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Affiliation(s)
- Haddijatou Mbye
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Karim Mane
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Mouhamadou Fadel Diop
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Martha Anita Demba
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Fatoumata Bojang
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | | | - David Jeffries
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | | | - Umberto D'Alessandro
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Alfred Amambua-Ngwa
- Medical Research Council at London School of Hygiene and Tropical Medicine, Fajara, The Gambia
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Highly Variable Expression of Merozoite Surface Protein MSPDBL2 in Diverse Plasmodium falciparum Clinical Isolates and Transcriptome Scans for Correlating Genes. mBio 2022; 13:e0194822. [PMID: 35950755 PMCID: PMC9426457 DOI: 10.1128/mbio.01948-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The merozoite surface protein MSPDBL2 of Plasmodium falciparum is under strong balancing selection and is a target of naturally acquired antibodies. Remarkably, MSPDBL2 is expressed in only a minority of mature schizonts of any cultured parasite line, and mspdbl2 gene transcription increases in response to overexpression of the gametocyte development inducer GDV1, so it is important to understand its natural expression. Here, MSPDBL2 in mature schizonts was analyzed in the first ex vivo culture cycle of 96 clinical isolates from 4 populations with various levels of infection endemicity in different West African countries, by immunofluorescence microscopy with antibodies against a conserved region of the protein. In most isolates, less than 1% of mature schizonts were positive for MSPDBL2, but the frequency distribution was highly skewed, as nine isolates had more than 3% schizonts positive and one had 73% positive. To investigate whether the expression of other gene loci correlated with MSPDBL2 expression, whole-transcriptome sequencing was performed on schizont-enriched material from 17 of the isolates with a wide range of proportions of schizonts positive. Transcripts of particular genes were highly significantly positively correlated with MSPDBL2 positivity in schizonts as well as with mspdbl2 gene transcript levels, showing overrepresentation of genes implicated previously as involved in gametocytogenesis but not including the gametocytogenesis master regulator ap2-g. Single-cell transcriptome analysis of a laboratory-adapted clone showed that most individual parasites expressing mspdbl2 did not express ap2-g, consistent with MSPDBL2 marking a developmental subpopulation that is distinct but likely to co-occur alongside sexual commitment. IMPORTANCE These findings contribute to understanding malaria parasite antigenic and developmental variation, focusing on the merozoite surface protein encoded by the single locus under strongest balancing selection. Analyzing the initial ex vivo generation of parasites grown from a wide sample of clinical infections, we show a unique and highly skewed pattern of natural expression frequencies of MSPDBL2, distinct from that of any other antigen. Bulk transcriptome analysis of a range of clinical isolates showed significant overrepresentation of sexual development genes among those positively correlated with MSPDBL2 protein and mspdbl2 gene expression, indicating the MSPDBL2-positive subpopulation to be often coincident with parasites developing sexually in preparation for transmission. Single-cell transcriptome data confirm the absence of a direct correlation with the ap2-g master regulator of sexual development, indicating that the MSPDBL2-positive subpopulation has a separate function in asexual survival and replication under conditions that promote terminal sexual differentiation.
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Abstract
Although the last two decades have seen a substantial decline in malaria incidence and mortality due to the use of insecticide-treated bed nets and artemisinin combination therapy, the threat of drug resistance is a constant obstacle to sustainable malaria control. Given that patients can die quickly from this disease, public health officials and doctors need to understand whether drug resistance exists in the parasite population, as well as how prevalent it is so they can make informed decisions about treatment. As testing for drug efficacy before providing treatment to malaria patients is impractical, researchers need molecular markers of resistance that can be more readily tracked in parasite populations. To this end, much work has been done to unravel the genetic underpinnings of drug resistance in Plasmodium falciparum. The aim of this review is to provide a broad overview of common genomic approaches that have been used to discover the alleles that drive drug response phenotypes in the most lethal human malaria parasite.
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Affiliation(s)
- Frances Rocamora
- Department of Pediatrics, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
| | - Elizabeth A Winzeler
- Department of Pediatrics, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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Plasmodium Genomics and Genetics: New Insights into Malaria Pathogenesis, Drug Resistance, Epidemiology, and Evolution. Clin Microbiol Rev 2019; 32:32/4/e00019-19. [PMID: 31366610 DOI: 10.1128/cmr.00019-19] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Protozoan Plasmodium parasites are the causative agents of malaria, a deadly disease that continues to afflict hundreds of millions of people every year. Infections with malaria parasites can be asymptomatic, with mild or severe symptoms, or fatal, depending on many factors such as parasite virulence and host immune status. Malaria can be treated with various drugs, with artemisinin-based combination therapies (ACTs) being the first-line choice. Recent advances in genetics and genomics of malaria parasites have contributed greatly to our understanding of parasite population dynamics, transmission, drug responses, and pathogenesis. However, knowledge gaps in parasite biology and host-parasite interactions still remain. Parasites resistant to multiple antimalarial drugs have emerged, while advanced clinical trials have shown partial efficacy for one available vaccine. Here we discuss genetic and genomic studies of Plasmodium biology, host-parasite interactions, population structures, mosquito infectivity, antigenic variation, and targets for treatment and immunization. Knowledge from these studies will advance our understanding of malaria pathogenesis, epidemiology, and evolution and will support work to discover and develop new medicines and vaccines.
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Abstract
Eukaryotic pathogens must survive in different hosts, respond to changing environments, and exploit specialized niches to propagate. Plasmodium parasites cause human malaria during bloodstream infections, where they must persist long enough to be transmitted. Parasites have evolved diverse strategies of variant gene expression that control critical biological processes of blood-stage infections, including antigenic variation, erythrocyte invasion, innate immune evasion, and nutrient acquisition, as well as life-cycle transitions. Epigenetic mechanisms within the parasite are being elucidated, with discovery of epigenomic marks associated with gene silencing and activation, and the identification of epigenetic regulators and chromatin proteins that are required for the switching and maintenance of gene expression. Here, we review the key epigenetic processes that facilitate transition through the parasite life cycle and epigenetic regulatory mechanisms utilized by Plasmodium parasites to survive changing environments and consider epigenetic switching in the context of the outcome of human infections.
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Affiliation(s)
- Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA; ,
| | - Kristen M Skillman
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA; ,
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10
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Identity-by-descent analyses for measuring population dynamics and selection in recombining pathogens. PLoS Genet 2018; 14:e1007279. [PMID: 29791438 PMCID: PMC5988311 DOI: 10.1371/journal.pgen.1007279] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 06/05/2018] [Accepted: 02/26/2018] [Indexed: 12/30/2022] Open
Abstract
Identification of genomic regions that are identical by descent (IBD) has proven useful for human genetic studies where analyses have led to the discovery of familial relatedness and fine-mapping of disease critical regions. Unfortunately however, IBD analyses have been underutilized in analysis of other organisms, including human pathogens. This is in part due to the lack of statistical methodologies for non-diploid genomes in addition to the added complexity of multiclonal infections. As such, we have developed an IBD methodology, called isoRelate, for analysis of haploid recombining microorganisms in the presence of multiclonal infections. Using the inferred IBD status at genomic locations, we have also developed a novel statistic for identifying loci under positive selection and propose relatedness networks as a means of exploring shared haplotypes within populations. We evaluate the performance of our methodologies for detecting IBD and selection, including comparisons with existing tools, then perform an exploratory analysis of whole genome sequencing data from a global Plasmodium falciparum dataset of more than 2500 genomes. This analysis identifies Southeast Asia as having many highly related isolates, possibly as a result of both reduced transmission from intensified control efforts and population bottlenecks following the emergence of antimalarial drug resistance. Many signals of selection are also identified, most of which overlap genes that are known to be associated with drug resistance, in addition to two novel signals observed in multiple countries that have yet to be explored in detail. Additionally, we investigate relatedness networks over the selected loci and determine that one of these sweeps has spread between continents while the other has arisen independently in different countries. IBD analysis of microorganisms using isoRelate can be used for exploring population structure, positive selection and haplotype distributions, and will be a valuable tool for monitoring disease control and elimination efforts of many diseases. There are growing concerns over the emergence of antimicrobial drug resistance, which threatens the efficacy of treatments for infectious diseases such as malaria. As such, it is important to understand the dynamics of resistance by investigating population structure, natural selection and disease transmission in microorganisms. The study of disease dynamics has been hampered by the lack of suitable statistical models for analysis of isolates containing multiple infections. We introduce a statistical model that uses population genomic data to identify genomic regions (loci) that are inherited from a common ancestor, in the presence of multiple infections. We demonstrate its potential for biological discovery using a global Plasmodium falciparum dataset. We identify low genetic diversity in isolates from Southeast Asia, possibly from clonal expansion following intensified control efforts after the emergence of artemisinin resistance. We also identify loci under positive selection, most of which contain genes that have been associated with antimalarial drug resistance. We discover two loci under strong selection in multiple countries throughout Southeast Asia and Africa where the selection pressure is currently unknown. We find that the selection pressure at one of these loci has originated from gene flow, while the other loci has originated from multiple independent events.
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Bei AK, Ahouidi AD, Dvorin JD, Miura K, Diouf A, Ndiaye D, Premji Z, Diakite M, Mboup S, Long CA, Duraisingh MT. Functional Analysis Reveals Geographical Variation in Inhibitory Immune Responses Against a Polymorphic Malaria Antigen. J Infect Dis 2017; 216:267-275. [PMID: 28605544 PMCID: PMC5853457 DOI: 10.1093/infdis/jix280] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Accepted: 06/08/2017] [Indexed: 12/28/2022] Open
Abstract
Background Plasmodium falciparum reticulocyte-binding protein homologue 2b (PfRh2b) is an invasion ligand that is a potential blood-stage vaccine candidate antigen; however, a naturally occurring deletion within an immunogenic domain is present at high frequencies in Africa and has been associated with alternative invasion pathway usage. Standardized tools that provide antigenic specificity in in vitro assays are needed to functionally assess the neutralizing potential of humoral responses against malaria vaccine candidate antigens. Methods Transgenic parasite lines were generated to express the PfRh2b deletion. Total immunoglobulin G (IgG) from individuals residing in malaria-endemic regions in Tanzania, Senegal, and Mali were used in growth inhibition assays with transgenic parasite lines. Results While the PfRh2b deletion transgenic line showed no change in invasion pathway utilization compared to the wild-type in the absence of specific antibodies, it outgrew wild-type controls in competitive growth experiments. Inhibition differences with total IgG were observed in the different endemic sites, ranging from allele-specific inhibition to allele-independent inhibitory immune responses. Conclusions The PfRh2b deletion may allow the parasite to escape neutralizing antibody responses in some regions. This difference in geographical inhibition was revealed using transgenic methodologies, which provide valuable tools for functionally assessing neutralizing antibodies against vaccine-candidate antigens in regions with varying malaria endemicity.
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Affiliation(s)
- Amy K Bei
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
- Laboratory of Parasitology and Mycology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Ambroise D Ahouidi
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Jeffrey D Dvorin
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
- Division of Infectious Diseases, Boston Children's Hospital and Harvard Medical School, Massachusetts
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Ababacar Diouf
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Daouda Ndiaye
- Laboratory of Parasitology and Mycology, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
| | - Zul Premji
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar-es-Salaam, Tanzania
- Department of Pathology, Aga Khan University Hospital, Nairobi, Kenya
| | - Mahamadou Diakite
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odontostomatology, University of Science, Techniques and Technologies of Bamako, Mali
| | - Souleymane Mboup
- Laboratory of Bacteriology and Virology, Le Dantec Hospital, Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal
- Institut de Recherche en Santé, de Surveillance Epidemiologique et de Formations, Dakar, Senegal
| | - Carole A Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
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Abstract
Organisms with identical genome sequences can show substantial differences in their phenotypes owing to epigenetic changes that result in different use of their genes. Epigenetic regulation of gene expression plays a key role in the control of several fundamental processes in the biology of malaria parasites, including antigenic variation and sexual differentiation. Some of the histone modifications and chromatin-modifying enzymes that control the epigenetic states of malaria genes have been characterized, and their functions are beginning to be unraveled. The fundamental principles of epigenetic regulation of gene expression appear to be conserved between malaria parasites and model eukaryotes, but important peculiarities exist. Here, we review the current knowledge of malaria epigenetics and discuss how it can be exploited for the development of new molecular markers and new types of drugs that may contribute to malaria eradication efforts.
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Affiliation(s)
- Alfred Cortés
- ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Catalonia 08036, Spain.,ICREA, Barcelona, Catalonia 08010, Spain
| | - Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10065
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Volkman SK, Herman J, Lukens AK, Hartl DL. Genome-Wide Association Studies of Drug-Resistance Determinants. Trends Parasitol 2016; 33:214-230. [PMID: 28179098 DOI: 10.1016/j.pt.2016.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 09/26/2016] [Accepted: 10/06/2016] [Indexed: 02/07/2023]
Abstract
Population genetic strategies that leverage association, selection, and linkage have identified drug-resistant loci. However, challenges and limitations persist in identifying drug-resistance loci in malaria. In this review we discuss the genetic basis of drug resistance and the use of genome-wide association studies, complemented by selection and linkage studies, to identify and understand mechanisms of drug resistance and response. We also discuss the implications of nongenetic mechanisms of drug resistance recently reported in the literature, and present models of the interplay between nongenetic and genetic processes that contribute to the emergence of drug resistance. Throughout, we examine artemisinin resistance as an example to emphasize challenges in identifying phenotypes suitable for population genetic studies as well as complications due to multiple-factor drug resistance.
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Affiliation(s)
- Sarah K Volkman
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Disease, Boston, MA, USA; The Broad Institute of MIT and Harvard, Infectious Disease Initiative, Cambridge, MA, USA; Simmons College, School of Nursing and Health Science, Boston, MA, USA.
| | - Jonathan Herman
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Disease, Boston, MA, USA; Weill Department of Medicine, Weill Cornell Medical College, New York, NY, USA
| | - Amanda K Lukens
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Disease, Boston, MA, USA; The Broad Institute of MIT and Harvard, Infectious Disease Initiative, Cambridge, MA, USA
| | - Daniel L Hartl
- The Broad Institute of MIT and Harvard, Infectious Disease Initiative, Cambridge, MA, USA; Harvard University, Organismic and Evolutionary Biology, Cambridge, MA, USA
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The MSPDBL2 codon 591 polymorphism is associated with lumefantrine in vitro drug responses in Plasmodium falciparum isolates from Kilifi, Kenya. Antimicrob Agents Chemother 2014; 59:1770-5. [PMID: 25534732 PMCID: PMC4325780 DOI: 10.1128/aac.03522-14] [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] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of drug resistance development in the Plasmodium falciparum parasite to lumefantrine (LUM), commonly used in combination with artemisinin, are still unclear. We assessed the polymorphisms of Pfmspdbl2 for associations with LUM activity in a Kenyan population. MSPDBL2 codon 591S was associated with reduced susceptibility to LUM (P = 0.04). The high frequency of Pfmspdbl2 codon 591S in Kenya may be driven by the widespread use of lumefantrine in artemisinin combination therapy (Coartem).
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15
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Lin CS, Uboldi AD, Marapana D, Czabotar PE, Epp C, Bujard H, Taylor NL, Perugini MA, Hodder AN, Cowman AF. The merozoite surface protein 1 complex is a platform for binding to human erythrocytes by Plasmodium falciparum. J Biol Chem 2014; 289:25655-69. [PMID: 25074930 DOI: 10.1074/jbc.m114.586495] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plasmodium falciparum is the causative agent of the most severe form of malaria in humans. The merozoite, an extracellular stage of the parasite lifecycle, invades erythrocytes in which they develop. The most abundant protein on the surface of merozoites is merozoite surface protein 1 (MSP1), which consists of four processed fragments. Studies indicate that MSP1 interacts with other peripheral merozoite surface proteins to form a large complex. Successful invasion of merozoites into host erythrocytes is dependent on this protein complex; however, the identity of all components and its function remain largely unknown. We have shown that the peripheral merozoite surface proteins MSPDBL1 and MSPDBL2 are part of the large MSP1 complex. Using surface plasmon resonance, we determined the binding affinities of MSPDBL1 and MSPDBL2 to MSP1 to be in the range of 2-4 × 10(-7) m. Both proteins bound to three of the four proteolytically cleaved fragments of MSP1 (p42, p38, and p83). In addition, MSPDBL1 and MSPDBL2, but not MSP1, bound directly to human erythrocytes. This demonstrates that the MSP1 complex acts as a platform for display of MSPDBL1 and MSPDBL2 on the merozoite surface for binding to receptors on the erythrocyte and invasion.
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Affiliation(s)
- Clara S Lin
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia, Department of Medical Biology, The University of Melbourne, Melbourne 3010, Australia
| | - Alessandro D Uboldi
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia
| | - Danushka Marapana
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia, Department of Medical Biology, The University of Melbourne, Melbourne 3010, Australia
| | - Peter E Czabotar
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia, Department of Medical Biology, The University of Melbourne, Melbourne 3010, Australia
| | - Christian Epp
- Department of Infectious Diseases, Parasitology, Universität Heidelberg, INF 324, D-69120 Heidelberg, Germany
| | - Hermann Bujard
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), INF 282, D-69120 Heidelberg, Germany, and
| | - Nicole L Taylor
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3082, Australia
| | - Matthew A Perugini
- Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3082, Australia
| | - Anthony N Hodder
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia, Department of Medical Biology, The University of Melbourne, Melbourne 3010, Australia,
| | - Alan F Cowman
- From the The Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia, Department of Medical Biology, The University of Melbourne, Melbourne 3010, Australia,
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Analysis of antibodies to newly described Plasmodium falciparum merozoite antigens supports MSPDBL2 as a predicted target of naturally acquired immunity. Infect Immun 2013; 81:3835-42. [PMID: 23897617 PMCID: PMC3811751 DOI: 10.1128/iai.00301-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Prospective studies continue to identify malaria parasite genes with particular patterns of polymorphism which indicate they may be under immune selection, and the encoded proteins require investigation. Sixteen new recombinant protein reagents were designed to characterize three such polymorphic proteins expressed in Plasmodium falciparum schizonts and merozoites: MSPDBL1 (also termed MSP3.4) and MSPDBL2 (MSP3.8), which possess Duffy binding-like (DBL) domains, and SURFIN4.2, encoded by a member of the surface-associated interspersed (surf) multigene family. After testing the antigenicities of these reagents by murine immunization and parasite immunofluorescence, we analyzed naturally acquired antibody responses to the antigens in two cohorts in coastal Kenya in which the parasite was endemic (Chonyi [n = 497] and Ngerenya [n = 461]). As expected, the prevalence and levels of serum antibodies increased with age. We then investigated correlations with subsequent risk of clinical malaria among children <11 years of age during 6 months follow-up surveillance. Antibodies to the polymorphic central region of MSPDBL2 were associated with reduced risk of malaria in both cohorts, with statistical significance remaining for the 3D7 allelic type after adjustment for individuals' ages in years and antibody reactivity to whole-schizont extract (Chonyi, risk ratio, 0.51, and 95% confidence interval [CI], 0.28 to 0.93; Ngerenya, risk ratio, 0.38, and 95% CI, 0.18 to 0.82). For the MSPDBL1 Palo Alto allelic-type antigen, there was a protective association in one cohort (Ngerenya, risk ratio, 0.53, and 95% CI, 0.32 to 0.89), whereas the other antigens showed no protective associations after adjustment. These findings support the prediction that antibodies to the polymorphic region of MSPDBL2 contribute to protective immunity.
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