1
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Eldh M, Hammar U, Arnot D, Beck HP, Garcia A, Liljander A, Mercereau-Puijalon O, Migot-Nabias F, Mueller I, Ntoumi F, Ross A, Smith T, Sondén K, Vafa Homann M, Yman V, Felger I, Färnert A. Multiplicity of Asymptomatic Plasmodium falciparum Infections and Risk of Clinical Malaria: A Systematic Review and Pooled Analysis of Individual Participant Data. J Infect Dis 2020; 221:775-785. [PMID: 31585009 PMCID: PMC7026891 DOI: 10.1093/infdis/jiz510] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/01/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The malaria parasite Plasmodium falciparum holds an extensive genetic polymorphism. In this pooled analysis, we investigate how the multiplicity in asymptomatic P. falciparum infections-that is, the number of coinfecting clones-affects the subsequent risk of clinical malaria in populations living under different levels of transmission. METHODS A systematic search of the literature was performed to identify studies in which P. falciparum infections were genotyped in asymptomatic individuals who were followed up prospectively regarding the incidence of clinical malaria. Individual participant data were pooled from 15 studies (n = 3736 individuals). RESULTS Multiclonal asymptomatic infections were associated with a somewhat increased subsequent risk of clinical malaria in the youngest children, followed by an initial declining risk with age irrespective of transmission intensity. At approximately 5 years of age, the risk continued the gradual decline with age in high-transmission settings. However, in older children in moderate-, low-, and seasonal-transmission settings, multiclonal infections were either not significantly associated with the risk of subsequent febrile malaria or were associated with an increased risk. CONCLUSIONS The number of clones in asymptomatic P. falciparum infections is associated with different risks of subsequent clinical malaria depending on age and transmission intensity.
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Affiliation(s)
- Martina Eldh
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Ulf Hammar
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - David Arnot
- Zhejiang-Edinburgh Institute, Zhejiang University Medical School, International Campus of Zhejiang University, Haining, People's Republic of China
| | - Hans-Peter Beck
- Molecular Diagnostics, Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - André Garcia
- MERIT, IRD, Université Paris 5, Sorbonne Paris Cité, Paris, France.,Cerpage, Cotonou, Bénin
| | - Anne Liljander
- International Livestock Research Institute, Nairobi, Kenya
| | | | | | - Ivo Mueller
- Institut Pasteur, Parasites and Insect Vectors Department, Paris, France
| | - Francine Ntoumi
- Fondation Congolaise pour la Recherche Médicale and Faculty of Sciences and Technology University Marien Ngouabi Brazzaville, Republic of Congo.,Institute for Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Amanda Ross
- University of Basel, Basel, Switzerland.,Department of Epidemiology and Public Health, Swiss Tropical Institute, Basel, Switzerland
| | - Thomas Smith
- University of Basel, Basel, Switzerland.,Department of Epidemiology and Public Health, Swiss Tropical Institute, Basel, Switzerland
| | - Klara Sondén
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Manijeh Vafa Homann
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Victor Yman
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Ingrid Felger
- Molecular Diagnostics, Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Anna Färnert
- Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.,Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
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2
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Pigeault R, Isaïa J, Yerbanga RS, Dabiré KR, Ouédraogo JB, Cohuet A, Lefèvre T, Christe P. Different distribution of malaria parasite in left and right extremities of vertebrate hosts translates into differences in parasite transmission. Sci Rep 2020; 10:10183. [PMID: 32576924 PMCID: PMC7311528 DOI: 10.1038/s41598-020-67180-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 06/04/2020] [Indexed: 11/16/2022] Open
Abstract
Malaria, a vector-borne disease caused by Plasmodium spp., remains a major global cause of mortality. Optimization of disease control strategies requires a thorough understanding of the processes underlying parasite transmission. While the number of transmissible stages (gametocytes) of Plasmodium in blood is frequently used as an indicator of host-to-mosquito transmission potential, this relationship is not always clear. Significant effort has been made in developing molecular tools that improve gametocyte density estimation and therefore prediction of mosquito infection rates. However a significant level of uncertainty around estimates remains. The weakness in the relationship between gametocyte burden, measured from a blood sample, and the mosquito infection rate could be explained by a non-homogeneous distribution of gametocytes in the bloodstream. The estimated gametocyte density would then only be a single snapshot that does not reflect the host infectivity. This aspect of Plasmodium infection, however, remains largely neglected. In both humans and birds, we found here that the gametocyte densities differed depending on which side of the body the sample was taken, suggesting that gametocytes are not homogeneously distributed within the vertebrate host. We observed a fluctuating asymmetry, in other words, the extremity of the body with the highest density of parasites is not always the same from one individual to another. An estimation of gametocyte density from only one blood sample, as is commonly measured, could, therefore, over- or underestimated the infectivity of gametocyte carriers. This might have important consequences on the epidemiology of the disease since we show that this variation influences host-to-mosquito transmission. Vectors fed on the least infected body part had a lower parasite burden than those fed on the most infected part. The heterogeneous distribution of gametocytes in bloodstream should be considered to improve diagnosis and test new malaria control strategies.
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Affiliation(s)
- Romain Pigeault
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland.
| | - Julie Isaïa
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland
| | | | - Kounbobr R Dabiré
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | | | - Anna Cohuet
- Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
- Unité MIVEGEC, IRD 224-CNRS 5290-Université Montpellier, Montpellier, France
| | - Philippe Christe
- Department of Ecology and Evolution, CH-1015, Lausanne, Switzerland
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3
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Nkhoma SC, Banda RL, Khoswe S, Dzoole-Mwale TJ, Ward SA. Intra-host dynamics of co-infecting parasite genotypes in asymptomatic malaria patients. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2018; 65:414-424. [PMID: 30145390 PMCID: PMC6219893 DOI: 10.1016/j.meegid.2018.08.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Revised: 08/13/2018] [Accepted: 08/20/2018] [Indexed: 11/22/2022]
Abstract
Malaria-infected individuals often harbor mixtures of genetically distinct parasite genotypes. We studied intra-host dynamics of parasite genotypes co-infecting asymptomatic adults in an area of intense malaria transmission in Chikhwawa, Malawi. Serial blood samples (5 ml) were collected over seven consecutive days from 25 adults with asymptomatic Plasmodium falciparum malaria and analyzed to determine whether a single peripheral blood sample accurately captures within-host parasite diversity. Blood samples from three of the participants were also analyzed by limiting dilution cloning and SNP genotyping of the parasite clones isolated to examine both the number and relatedness of co-infecting parasite haplotypes. We observed rapid turnover of co-infecting parasite genotypes in 88% of the individuals sampled (n = 22) such that the genetic composition of parasites infecting these individuals changed dramatically over the course of seven days of follow up. Nineteen of the 25 individuals sampled (76%) carried multiple parasite genotypes at baseline. Analysis of serial blood samples from three of the individuals revealed that they harbored 6, 12 and 17 distinct parasite haplotypes respectively. Approximately 70% of parasite haplotypes recovered from the three extensively sampled individuals were unrelated (proportion of shared alleles <83.3%) and were deemed to have primarily arisen from superinfection (inoculation of unrelated parasite haplotypes through multiple mosquito bites). The rest were related at the half-sib level or greater and were deemed to have been inoculated into individual human hosts via parasite co-transmission from single mosquito bites. These findings add further to the growing weight of evidence indicating that a single blood sample poorly captures within-host parasite diversity and underscore the importance of repeated blood sampling to accurately capture within-host parasite ecology. Our data also demonstrate a more pronounced role for parasite co-transmission in generating within-host parasite diversity in high transmission settings than previously assumed. Taken together, these findings have important implications for understanding the evolution of drug resistance, malaria transmission, parasite virulence, allocation of gametocyte sex ratios and acquisition of malaria immunity.
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Affiliation(s)
- Standwell C Nkhoma
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi; Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; Wellcome Trust-Liverpool-Glasgow Centre for Global Health Research, 70 Pembroke Place, Liverpool L69 3GF, UK.
| | - Rachel L Banda
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
| | - Stanley Khoswe
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
| | - Tamika J Dzoole-Mwale
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi
| | - Stephen A Ward
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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4
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Chou ES, Abidi SZ, Teye M, Leliwa-Sytek A, Rask TS, Cobbold SA, Tonkin-Hill GQ, Subramaniam KS, Sexton AE, Creek DJ, Daily JP, Duffy MF, Day KP. A high parasite density environment induces transcriptional changes and cell death in Plasmodium falciparum blood stages. FEBS J 2018; 285:848-870. [PMID: 29281179 DOI: 10.1111/febs.14370] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 12/01/2017] [Accepted: 12/20/2017] [Indexed: 12/17/2022]
Abstract
Transient regulation of Plasmodium numbers below the density that induces fever has been observed in chronic malaria infections in humans. This species transcending control cannot be explained by immunity alone. Using an in vitro system we have observed density dependent regulation of malaria population size as a mechanism to possibly explain these in vivo observations. Specifically, Plasmodium falciparum blood stages from a high but not low-density environment exhibited unique phenotypic changes during the late trophozoite (LT) and schizont stages of the intraerythrocytic cycle. These included in order of appearance: failure of schizonts to mature and merozoites to replicate, apoptotic-like morphological changes including shrinking, loss of mitochondrial membrane potential, and blebbing with eventual release of aberrant parasites from infected erythrocytes. This unique death phenotype was triggered in a stage-specific manner by sensing of a high-density culture environment. Conditions of glucose starvation, nutrient depletion, and high lactate could not induce the phenotype. A high-density culture environment induced rapid global changes in the parasite transcriptome including differential expression of genes involved in cell remodeling, clonal antigenic variation, metabolism, and cell death pathways including an apoptosis-associated metacaspase gene. This transcriptional profile was also characterized by concomitant expression of asexual and sexual stage-specific genes. The data show strong evidence to support our hypothesis that density sensing exists in P. falciparum. They indicate that an apoptotic-like mechanism may play a role in P. falciparum density regulation, which, as in yeast, has features quite distinguishable from mammalian apoptosis. DATABASE Gene expression data are available in the GEO databases under the accession number GSE91188.
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Affiliation(s)
- Evelyn S Chou
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Sabia Z Abidi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Marian Teye
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Aleksandra Leliwa-Sytek
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Thomas S Rask
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Simon A Cobbold
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Gerry Q Tonkin-Hill
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC., Australia
| | - Krishanthi S Subramaniam
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | - Anna E Sexton
- Drug Delivery Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC., Australia
| | - Darren J Creek
- Drug Delivery Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC., Australia
| | - Johanna P Daily
- Department of Medicine, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Michael F Duffy
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Karen P Day
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
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5
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Ramiro RS, Pollitt LC, Mideo N, Reece SE. Facilitation through altered resource availability in a mixed-species rodent malaria infection. Ecol Lett 2016; 19:1041-50. [PMID: 27364562 PMCID: PMC5025717 DOI: 10.1111/ele.12639] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/03/2016] [Accepted: 05/13/2016] [Indexed: 12/17/2022]
Abstract
A major challenge in disease ecology is to understand how co-infecting parasite species interact. We manipulate in vivo resources and immunity to explain interactions between two rodent malaria parasites, Plasmodium chabaudi and P. yoelii. These species have analogous resource-use strategies to the human parasites Plasmodium falciparum and P. vivax: P. chabaudi and P. falciparum infect red blood cells (RBC) of all ages (RBC generalist); P. yoelii and P. vivax preferentially infect young RBCs (RBC specialist). We find that: (1) recent infection with the RBC generalist facilitates the RBC specialist (P. yoelii density is enhanced ~10 fold). This occurs because the RBC generalist increases availability of the RBC specialist's preferred resource; (2) co-infections with the RBC generalist and RBC specialist are highly virulent; (3) and the presence of an RBC generalist in a host population can increase the prevalence of an RBC specialist. Thus, we show that resources shape how parasite species interact and have epidemiological consequences.
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Affiliation(s)
- Ricardo S Ramiro
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh, EH9 3JFL, UK
| | - Laura C Pollitt
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh, EH9 3JFL, UK.,Centre for Immunity, Infection & Evolution, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, EH9 3JFL, UK
| | - Nicole Mideo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Sarah E Reece
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh, EH9 3JFL, UK.,Centre for Immunity, Infection & Evolution, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, EH9 3JFL, UK
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6
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Pollitt LC, Bram JT, Blanford S, Jones MJ, Read AF. Existing Infection Facilitates Establishment and Density of Malaria Parasites in Their Mosquito Vector. PLoS Pathog 2015; 11:e1005003. [PMID: 26181518 PMCID: PMC4504473 DOI: 10.1371/journal.ppat.1005003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/04/2015] [Indexed: 02/06/2023] Open
Abstract
Very little is known about how vector-borne pathogens interact within their vector and how this impacts transmission. Here we show that mosquitoes can accumulate mixed strain malaria infections after feeding on multiple hosts. We found that parasites have a greater chance of establishing and reach higher densities if another strain is already present in a mosquito. Mixed infections contained more parasites but these larger populations did not have a detectable impact on vector survival. Together these results suggest that mosquitoes taking multiple infective bites may disproportionally contribute to malaria transmission. This will increase rates of mixed infections in vertebrate hosts, with implications for the evolution of parasite virulence and the spread of drug-resistant strains. Moreover, control measures that reduce parasite prevalence in vertebrate hosts will reduce the likelihood of mosquitoes taking multiple infective feeds, and thus disproportionally reduce transmission. More generally, our study shows that the types of strain interactions detected in vertebrate hosts cannot necessarily be extrapolated to vectors.
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Affiliation(s)
- Laura C. Pollitt
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
- * E-mail:
| | - Joshua T. Bram
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Simon Blanford
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Matthew J. Jones
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
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7
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Sondén K, Doumbo S, Hammar U, Vafa Homann M, Ongoiba A, Traoré B, Bottai M, Crompton PD, Färnert A. Asymptomatic Multiclonal Plasmodium falciparum Infections Carried Through the Dry Season Predict Protection Against Subsequent Clinical Malaria. J Infect Dis 2015; 212:608-16. [PMID: 25712968 DOI: 10.1093/infdis/jiv088] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/06/2015] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Immunity to the antigenically diverse parasite Plasmodium falciparum is acquired gradually after repeated exposure. Studies in areas of high malaria transmission have shown that asymptomatic individuals infected with multiclonal infections are at reduced risk of febrile malaria during follow-up. METHODS We assessed the relationship between the genetic diversity of clones in P. falciparum infections that persist through the dry season and the subsequent risk of febrile malaria in 225 individuals aged 2-25 years in Mali, where the 6-month malaria and dry seasons are sharply demarcated. Polymerase chain reaction-based genotyping of the highly polymorphic merozoite surface protein 2 gene was performed on blood samples collected at 5 cross-sectional surveys. RESULTS In an age-adjusted analysis, individuals with multiclonal P. falciparum infections before the rainy season were at reduced risk of febrile malaria, compared with individuals who were uninfected (hazard ratio [HR], 0.28; 95% confidence interval [CI], .11-.69). In contrast, there was no significant association between risk of malaria and having 1 clone at baseline (HR, 0.71; 95% CI, .36-1.40). CONCLUSIONS The results suggest that persistent multiclonal infections carried through the dry season contribute to protection against subsequent febrile malaria, possibly by maintaining protective immune responses that depend on ongoing parasite infection.
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Affiliation(s)
- Klara Sondén
- Unit of Infectious Diseases, Department of Medicine Solna
| | - Safiatou Doumbo
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Ulf Hammar
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | | | - Aissata Ongoiba
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Boubacar Traoré
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Matteo Bottai
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Anna Färnert
- Unit of Infectious Diseases, Department of Medicine Solna
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8
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Pinkevych M, Petravic J, Bereczky S, Rooth I, Färnert A, Davenport MP. Understanding the relationship between Plasmodium falciparum growth rate and multiplicity of infection. J Infect Dis 2014; 211:1121-7. [PMID: 25301957 DOI: 10.1093/infdis/jiu561] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Natural infections with Plasmodium falciparum are often composed of multiple concurrent genetically distinct parasite clones. Such multiclonal infections are more common in areas of high transmission, and the frequency of multiclonal infection also varies with age. A number of studies have suggested that multiclonal infection predicts the risk of subsequent clinical malaria. The multiplicity of infection is determined by the rate of new infections, the number of clones inoculated at each mosquito bite, and the duration of infections. Here, we used a mathematical modeling approach to understand how variation in the growth rate of blood-stage parasites affects the observed multiplicity of infection (MOI), as well as the relationship between the MOI and the risk of subsequent malaria. We then analyzed data from a study of multiclonal infection and malaria in an malaria-endemic area in Tanzania and show that the proportion of multiclonal infections varies with age and that the observed relationship between multiclonal infection and subsequent clinical events can be explained by a reduction in blood-stage parasite growth with age in this population.
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Affiliation(s)
- Mykola Pinkevych
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Janka Petravic
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Sandor Bereczky
- Unit of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Ingegerd Rooth
- Unit of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Anna Färnert
- Unit of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Miles P Davenport
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
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9
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Genetic diversity of Plasmodium vivax over time and space: a community-based study in rural Amazonia. Parasitology 2014; 142:374-84. [PMID: 25068581 DOI: 10.1017/s0031182014001176] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To examine how community-level genetic diversity of the malaria parasite Plasmodium vivax varies across time and space, we investigated the dynamics of parasite polymorphisms during the early phases of occupation of a frontier settlement in the Amazon Basin of Brazil. Microsatellite characterization of 84 isolates of P. vivax sampled over 3 years revealed a moderate-to-high genetic diversity (mean expected heterozygosity, 0.699), with a large proportion (78.5%) of multiple-clone infections (MCI), but also a strong multilocus linkage disequilibrium (LD) consistent with rare outcrossing. Little temporal and no spatial clustering was observed in the distribution of parasite haplotypes. A single microsatellite haplotype was shared by 3 parasites collected during an outbreak; all other 81 haplotypes were recovered only once. The lowest parasite diversity, with the smallest proportion of MCI and the strongest LD, was observed at the time of the outbreak, providing a clear example of epidemic population structure in a human pathogen. Population genetic parameters returned to pre-outbreak values during last 2 years of study, despite the concomitant decline in malaria incidence. We suggest that parasite genotyping can be useful for tracking the spread of new parasite strains associated with outbreaks in areas approaching malaria elimination.
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10
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Pollitt LC, Huijben S, Sim DG, Salathé RM, Jones MJ, Read AF. Rapid response to selection, competitive release and increased transmission potential of artesunate-selected Plasmodium chabaudi malaria parasites. PLoS Pathog 2014; 10:e1004019. [PMID: 24763470 PMCID: PMC3999151 DOI: 10.1371/journal.ppat.1004019] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 02/06/2014] [Indexed: 11/19/2022] Open
Abstract
The evolution of drug resistance, a key challenge for our ability to treat and control infections, depends on two processes: de-novo resistance mutations, and the selection for and spread of resistant mutants within a population. Understanding the factors influencing the rates of these two processes is essential for maximizing the useful lifespan of drugs and, therefore, effective disease control. For malaria parasites, artemisinin-based drugs are the frontline weapons in the fight against disease, but reports from the field of slower parasite clearance rates during drug treatment are generating concern that the useful lifespan of these drugs may be limited. Whether slower clearance rates represent true resistance, and how this provides a selective advantage for parasites is uncertain. Here, we show that Plasmodium chabaudi malaria parasites selected for resistance to artesunate (an artemisinin derivative) through a step-wise increase in drug dose evolved slower clearance rates extremely rapidly. In single infections, these slower clearance rates, similar to those seen in the field, provided fitness advantages to the parasite through increased overall density, recrudescence after treatment and increased transmission potential. In mixed infections, removal of susceptible parasites by drug treatment led to substantial increases in the densities and transmission potential of resistant parasites (competitive release). Our results demonstrate the double-edged sword for resistance management: in our initial selection experiments, no parasites survived aggressive chemotherapy, but after selection, the fitness advantage for resistant parasites was greatest at high drug doses. Aggressive treatment of mixed infections resulted in resistant parasites dominating the pool of gametocytes, without providing additional health benefits to hosts. Slower clearance rates can evolve rapidly and can provide a strong fitness advantage during drug treatment in both single and mixed strain infections.
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Affiliation(s)
- Laura C. Pollitt
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Centre for Immunology, Infection and Evolution, The University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
| | - Silvie Huijben
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Derek G. Sim
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Rahel M. Salathé
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Matthew J. Jones
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Entomology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
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11
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Dynamics of clonal diversity in natural infections of the malaria parasite Plasmodium mexicanum in its free-ranging lizard host. Parasitol Res 2014; 113:2059-67. [PMID: 24647987 DOI: 10.1007/s00436-014-3854-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 03/05/2014] [Indexed: 10/25/2022]
Abstract
Within mixed-genotype infections of malaria parasites (Plasmodium), the number of genetic clones present is associated with variation in important life history traits of the infection, including virulence. Although the number of clones present is important, how the proportion of those clones varies over time is poorly known. Clonal proportions of the lizard malaria parasite, Plasmodium mexicanum, were assessed in naturally infected free-ranging lizards followed in a mark-recapture program over as long as two warm seasons, the typical life span of the lizard. Clonal proportions were determined by amplifying two microsatellite markers, a method previously verified for accuracy. Most blood samples had been stored for over a decade, so a verification test determined that these samples had not degraded. Although the environment experienced by the parasite (its host) varies over the seasons and transmission occurs over the entire warm season, 68% of infections were stable over time, harboring a single clone (37% of infections) or multiple clones changing only 1-12% maximum comparing any two samples (31% of infections). The maximum change seen in any infection (comparing any two sample periods) was only 30%. A new clone entered three infections (only once successfully), and a clone was lost in only three infections. These results mirror those seen for a previous study of experimentally induced infections that showed little change in relative proportions over time. The results of this study, the first look at how clonal proportions vary over time for any malaria parasite of a nonhuman vertebrate host for natural infections, were surprising because experimental studies show clones of P. mexicanum appear to interact, yet relative proportions of clones typically remain constant over time.
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Mita T, Ohashi J, Venkatesan M, Marma ASP, Nakamura M, Plowe CV, Tanabe K. Ordered accumulation of mutations conferring resistance to sulfadoxine-pyrimethamine in the Plasmodium falciparum parasite. J Infect Dis 2013; 209:130-9. [PMID: 23922363 DOI: 10.1093/infdis/jit415] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Monitoring the prevalence of drug resistant Plasmodium falciparum is essential for effective malaria control. Resistance to pyrimethamine and sulfadoxine increases as mutations accumulate in the parasite genes encoding dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps), respectively. Although parasites are exposed to these antifolate drugs simultaneously, it remains virtually unknown whether dhfr and dhps mutations accumulate along interrelated paths. METHODS We investigated the order of step-wise accumulation in dhfr and dhps by cumulative analyses using binomial tests in 575 P. falciparum isolates obtained from 7 countries in Asia and Melanesia. RESULTS An initial step in the accumulation of mutations preferentially occurred in dhfr (2 mutations), followed by 1 mutation in dhps. In a subsequent step, mutations were estimated separately for 5 dhfr/dhps-resistant lineages identified using 12 microsatellites flanking dhfr and dhps. Among these lineages, we found 3 major mutational paths, each of which follows a unique stepwise trajectory to produce the most highly resistant form with 4 mutations in dhfr and 3 in dhps. CONCLUSIONS The ordered accumulation of mutations in dhfr and dhps elucidated here will assist in predicting the status and progression of antifolate resistance in malaria-endemic regions where antifolate drugs are used for intermittent preventive treatment.
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Affiliation(s)
- Toshihiro Mita
- Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo, Japan
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Hicks ND, Schall JJ. Establishment efficiency among clones of the malaria parasite, Plasmodium mexicanum, for mixed-clone infections in its natural lizard host. J Parasitol 2013; 99:1050-5. [PMID: 23841469 DOI: 10.1645/12-72.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Within genetically diverse infections of malaria parasites ( Plasmodium spp.), the relative proportions of genetic clones in the vertebrate host's blood can influence clonal competition, transmission success, gametocyte sex ratio, and virulence. Clonal proportions depend on establishment success of each clone when they enter a new host and on subsequent differences in rates of asexual replication and clearance. Both of these life history traits could be influenced by clone genotype. To assess genetic (clonal) influences on both establishment success and later changes in relative proportion for the lizard malaria parasite Plasmodium mexicanum , 7 naturally infected fence lizards harboring a single clone of P. mexicanum served as donors to initiate replicate experimental infections containing each of the clones and combinations of 2 clones. Measured were relative establishment success of each clone, change in relative proportions over time, and rate of increase of parasite density and total parasitemia. Relative clonal proportions were determined using microsatellite markers. Rates of increase in the parasitemia and degree of change in relative proportions were not correlated, so both rapidly and slowly growing infections could show either little or substantial change in clonal proportions over time. There was a significant clone effect on establishment efficiency but not on later changes in relative proportions. These results argue for a combination of genetic and environmental (host) effects on the success of P. mexicanum clones in genetically complex infections. The maintenance of genetic variation for establishment success, but not subsequent replication rate or shifts in relative proportion, suggests trade-offs between these traits during life history evolution of malaria parasites.
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Affiliation(s)
- Nathan D Hicks
- Department of Biology, University of Vermont, Burlington, Vermont 05405
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Genetic diversity of Plasmodium falciparum infections in mild and severe malaria of children from Kampala, Uganda. Parasitol Res 2013; 112:1691-700. [PMID: 23408340 PMCID: PMC3597336 DOI: 10.1007/s00436-013-3325-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 01/27/2013] [Indexed: 11/18/2022]
Abstract
Diversity in parasite virulence is one of the factors that contribute to the clinical outcome of malaria infections. The association between the severity of Plasmodium falciparum malaria and the number of distinct parasite populations infecting the host (multiplicity of infection) or polymorphism within any of the specific antigen genes was investigated. The study included 164 children presenting with mild and severe malaria from central Uganda where malaria is meso-endemic. The polymorphic regions of the circumsporozoite protein (csp), merozoite surface proteins 1 and 2 (msp1 and msp2), and glutamate-rich protein (glurp) were genotyped by polymerase chain reaction methods and fragment analysis by gel electrophoresis. In a subset of samples fragment analysis was also performed by fluorescent PCR genotyping followed by capillary electrophoresis. The multiplicity of infection (MOI), determined as the highest number of alleles detected within any of the four genetic loci, was significantly higher in severe than in mild malaria cases (mean 3.7 and 3.0, respectively, P = 0.002). No particular genotype or allelic family of msp1 or msp2 was associated with severity of malaria, and nor did the genotyping method reveal any significant difference in MOI when only assessed by msp2 genotyping. Severity of malaria was not linked to the predominance of any particular msp1 or msp2 allelic types, independent of methods used for genotyping. Monitoring the dynamics of multiple clone infections in relation to disease outcome, host immune status and genetic factors will provide more insight into parasite virulence mechanisms.
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Lundblom K, Murungi L, Nyaga V, Olsson D, Rono J, Osier F, Ogada E, Montgomery S, Scott JAG, Marsh K, Färnert A. Plasmodium falciparum infection patterns since birth and risk of severe malaria: a nested case-control study in children on the coast of Kenya. PLoS One 2013; 8:e56032. [PMID: 23418502 PMCID: PMC3572150 DOI: 10.1371/journal.pone.0056032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 01/04/2013] [Indexed: 01/27/2023] Open
Abstract
Children in malaria endemic areas acquire immunity to severe malaria faster than to mild malaria. Only a minority of children suffers from severe malaria and it is not known what determines this. The aim of this study was to establish how P. falciparum infections during the first years of life affect the risk of severe malaria. A matched case-control study was nested within a large birth cohort set up to study the immunoepidemiology of pneumococci on the Kenyan coast. Infection patterns in three-monthly blood samples in cohort children admitted to hospital with severe malaria were compared to controls matched on age, residential location and time of sampling. P. falciparum detected at least once from birth conferred an increased risk of severe malaria and particularly if multiclonal infections, as characterized by genotyping of a polymorphic antigen gene, were ever detected. The results show for the first time that children with severe malaria have more infections early in life compared to community controls. These findings provide important insights on the immunity to severe disease, knowledge essential for the development of a vaccine against severe malaria.
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Affiliation(s)
- Klara Lundblom
- Unit of Infectious Diseases, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden.
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Pullan RL, Sturrock HJW, Soares Magalhães RJ, Clements ACA, Brooker SJ. Spatial parasite ecology and epidemiology: a review of methods and applications. Parasitology 2012; 139:1870-87. [PMID: 23036435 PMCID: PMC3526959 DOI: 10.1017/s0031182012000698] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 03/11/2012] [Accepted: 04/03/2012] [Indexed: 12/21/2022]
Abstract
The distributions of parasitic diseases are determined by complex factors, including many that are distributed in space. A variety of statistical methods are now readily accessible to researchers providing opportunities for describing and ultimately understanding and predicting spatial distributions. This review provides an overview of the spatial statistical methods available to parasitologists, ecologists and epidemiologists and discusses how such methods have yielded new insights into the ecology and epidemiology of infection and disease. The review is structured according to the three major branches of spatial statistics: continuous spatial variation; discrete spatial variation; and spatial point processes.
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Abstract
Explaining the contribution of host and pathogen factors in driving infection dynamics is a major ambition in parasitology. There is increasing recognition that analyses based on single summary measures of an infection (e.g., peak parasitaemia) do not adequately capture infection dynamics and so, the appropriate use of statistical techniques to analyse dynamics is necessary to understand infections and, ultimately, control parasites. However, the complexities of within-host environments mean that tracking and analysing pathogen dynamics within infections and among hosts poses considerable statistical challenges. Simple statistical models make assumptions that will rarely be satisfied in data collected on host and parasite parameters. In particular, model residuals (unexplained variance in the data) should not be correlated in time or space. Here we demonstrate how failure to account for such correlations can result in incorrect biological inference from statistical analysis. We then show how mixed effects models can be used as a powerful tool to analyse such repeated measures data in the hope that this will encourage better statistical practices in parasitology.
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Affiliation(s)
- Laura C Pollitt
- Institute of Evolutionary Biology, University of Edinburgh, School of Biological Sciences, Edinburgh, United Kingdom.
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Nkhoma SC, Nair S, Cheeseman IH, Rohr-Allegrini C, Singlam S, Nosten F, Anderson TJC. Close kinship within multiple-genotype malaria parasite infections. Proc Biol Sci 2012; 279:2589-98. [PMID: 22398165 PMCID: PMC3350702 DOI: 10.1098/rspb.2012.0113] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Malaria infections containing multiple parasite genotypes are ubiquitous in nature, and play a central role in models of recombination, intra-host dynamics, virulence, sex ratio, immunity and drug resistance evolution in Plasmodium. While these multiple infections (MIs) are often assumed to result from superinfection (bites from multiple infected mosquitoes), we know remarkably little about their composition or generation. We isolated 336 parasite clones from eight patients from Malawi (high transmission) and six from Thailand (low transmission) by dilution cloning. These were genotyped using 384 single-nucleotide polymorphisms, revealing 22 independent haplotypes in Malawi (2–6 per MI) and 15 in Thailand (2–5 per MI). Surprisingly, all six patients from Thailand and six of eight from Malawi contained related haplotypes, and haplotypes were more similar within- than between-infections. These results argue against a simple superinfection model. Instead, the observed kinship patterns may be explained by inoculation of multiple related haploid sporozoites from single mosquito bites, by immune suppression of parasite subpopulations within infections, and serial transmission of related parasites between people. That relatedness is maintained in endemic areas in the face of repeated bites from infected mosquitoes has profound implications for understanding malaria transmission, immunity and intra-host dynamics of co-infecting parasite genotypes.
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Affiliation(s)
- Standwell C Nkhoma
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX 78227, USA
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19
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Mideo N, Reece SE. Plasticity in parasite phenotypes: evolutionary and ecological implications for disease. Future Microbiol 2012; 7:17-24. [DOI: 10.2217/fmb.11.134] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Preventing disease is a major goal of applied bioscience and explaining variation in the harm caused by parasites, and their infectiousness, are major goals of evolutionary biology. The emerging field of evolutionary medicine integrates these two ambitions to inform the development of control strategies that retard or withstand unfavorable parasite evolution. However, as parasites live in hostile and changeable environments – the bodies of other organisms – the success of integrating evolutionary biology with medicine requires a better understanding of how natural selection has solved the problems parasites face. There is increasing appreciation that natural selection shapes parasite strategies to survive in the host and transmit between hosts through facultative (plastic) shifts in parasite traits expressed during infections and in different hosts. This article describes how integrating parasite plasticity into biomedical thinking is central to explaining disease outcomes and transmission patterns, as well as predicting the success of control measures.
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Affiliation(s)
- Nicole Mideo
- Centre for Immunity, Infection & Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
| | - Sarah E Reece
- Institutes of Evolution, Immunity & Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
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Genetic diversity in the merozoite surface protein 1 and 2 genes of Plasmodium falciparum from the Artibonite Valley of Haiti. Acta Trop 2012; 121:6-12. [PMID: 21982798 DOI: 10.1016/j.actatropica.2011.09.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 09/10/2011] [Accepted: 09/13/2011] [Indexed: 11/23/2022]
Abstract
Describing genetic diversity of the Plasmodium falciparum parasite provides important information about the local epidemiology of malaria. In this study, we examined the genetic diversity of P. falciparum isolates from the Artibonite Valley in Haiti using the allelic families of merozoite surface protein 1 and 2 genes (msp-1 and msp-2). The majority of study subjects infected with P. falciparum had a single parasite genotype (56% for msp-1 and 69% for msp-2: n=79); 9 distinct msp-1 genotypes were identified by size differences on agarose gels. K1 was the most polymorphic allelic family with 5 genotypes (amplicons from 100 to 300 base pairs [bp]); RO33 was the least polymorphic, with a single genotype (120-bp). Although both msp-2 alleles (3D7/IC1, FC27) had similar number of genotypes (n=4), 3D7/IC1 was more frequent (85% vs. 26%). All samples were screened for the presence of the K76T mutation on the P. falciparum chloroquine resistance transporter (pfcrt) gene with 10 of 79 samples positive. Of the 2 (out of 10) samples from individuals follow-up for 21 days, P. falciparum parasites were present through day 7 after treatment with chloroquine. No parasites were found on day 21. Our results suggest that the level of genetic diversity is low in this area of Haiti, which is consistent with an area of low transmission.
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Huijben S, Sim DG, Nelson WA, Read AF. The fitness of drug-resistant malaria parasites in a rodent model: multiplicity of infection. J Evol Biol 2011; 24:2410-22. [PMID: 21883612 PMCID: PMC3304104 DOI: 10.1111/j.1420-9101.2011.02369.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Malaria infections normally consist of more than one clonally replicating lineage. Within-host interactions between sensitive and resistant parasites can have profound effects on the evolution of drug resistance. Here, using the Plasmodium chabaudi mouse malaria model, we ask whether the costs and benefits of resistance are affected by the number of co-infecting strains competing with a resistant clone. We found strong competitive suppression of resistant parasites in untreated infections and marked competitive release following treatment. The magnitude of competitive suppression depended on competitor identity. However, there was no overall effect of the diversity of susceptible parasites on the extent of competitive suppression or release. If these findings generalize, then transmission intensity will impact on resistance evolution because of its effect on the frequency of mixed infections, not because of its effect on the distribution of clones per host. This would greatly simplify the computational problems of adequately capturing within-host ecology in models of drug resistance evolution in malaria.
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Affiliation(s)
- S Huijben
- Department of Biology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA 16802, USA.
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22
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Campos IM, Uribe ML, Cuesta C, Franco-Gallego A, Carmona-Fonseca J, Maestre A. Diagnosis of gestational, congenital, and placental malaria in Colombia: comparison of the efficacy of microscopy, nested polymerase chain reaction, and histopathology. Am J Trop Med Hyg 2011; 84:929-35. [PMID: 21633030 DOI: 10.4269/ajtmh.2011.10-0507] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The technical capability of different methods to diagnose Plasmodium in maternal peripheral blood, placenta, and umbilical cord blood has not been assessed in Colombia and seldom explored in other malaria-endemic regions. We designed a study to compare the technical and the operational-economical performances of light microscopy (LM), nested polymerase chain reaction (nPCR), and histopathology (HP). In maternal blood, LM had 41% sensitivity and 100% specificity and in placental blood, 35% and 100%, respectively, compared with nPCR. In placental tissue, LM had 33% sensitivity and 95% specificity; and nPCR 47% and 77%, respectively; compared with HP. Light microscopy had the best operational-economical qualification. We concluded that nPCR and HP performed better compared with LM, but field implementation of these two techniques remains a problem. Therefore, LM is recommended as the gold standard for diagnosis of gestational malaria and placental blood infection in the field.
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Affiliation(s)
- Ivón M Campos
- Grupo Salud y Comunidad, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia.
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The evolution of drug resistance and the curious orthodoxy of aggressive chemotherapy. Proc Natl Acad Sci U S A 2011; 108 Suppl 2:10871-7. [PMID: 21690376 DOI: 10.1073/pnas.1100299108] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The evolution of drug-resistant pathogens is a major challenge for 21st century medicine. Drug use practices vigorously advocated as resistance management tools by professional bodies, public health agencies, and medical schools represent some of humankind's largest attempts to manage evolution. It is our contention that these practices have poor theoretical and empirical justification for a broad spectrum of diseases. For instance, rapid elimination of pathogens can reduce the probability that de novo resistance mutations occur. This idea often motivates the medical orthodoxy that patients should complete drug courses even when they no longer feel sick. Yet "radical pathogen cure" maximizes the evolutionary advantage of any resistant pathogens that are present. It could promote the very evolution it is intended to retard. The guiding principle should be to impose no more selection than is absolutely necessary. We illustrate these arguments in the context of malaria; they likely apply to a wide range of infections as well as cancer and public health insecticides. Intuition is unreliable even in simple evolutionary contexts; in a social milieu where in-host competition can radically alter the fitness costs and benefits of resistance, expert opinion will be insufficient. An evidence-based approach to resistance management is required.
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Ford AF, Schall JJ. Relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite Plasmodium mexicanum. Int J Parasitol 2011; 41:731-8. [PMID: 21396372 DOI: 10.1016/j.ijpara.2011.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Revised: 01/20/2011] [Accepted: 01/25/2011] [Indexed: 11/15/2022]
Abstract
Vertebrate hosts of malaria parasites (Plasmodium) often harbour two or more genetically distinct clones of a single species, and interaction among these co-existing clones can play an important role in Plasmodium biology. However, how relative clonal proportions vary over time in a host is still poorly known. Experimental mixed-clone infections of the lizard malaria parasite, Plasmodium mexicanum, were followed in its natural host, the western fence lizard using microsatellite markers to determine the relative proportions of two to five co-existing clones over time (2-3 months). Results for two markers, and two PCR primer pairs for one of those, matched very closely, supporting the efficacy of the method. Of the 54 infections, 67% displayed stable relative clonal proportions, with the others showing a shift in proportions, usually with one clone outpacing the others. Infections with rapidly increasing or slowly increasing parasitemia were stable, showing that all clones within these infections reproduced at the same rapid or slow rate. Replicate infections containing the same clones did not always reveal the same growth rate, final parasitemia or dominant clone; thus there was no clone effect for these life history measures. The rate of increase in parasitemia was not associated with stable versus unstable relative proportions, but infections with four to five clones were more likely to be unstable than those with two to three clones. This rare look into events in genetically complex Plasmodium infections suggests that parasite clones may be interacting in complex and unexpected ways.
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Affiliation(s)
- Alice Flynn Ford
- Department of Biology, University of Vermont, Burlington, VT 05405, USA
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Liljander A, Bejon P, Mwacharo J, Kai O, Ogada E, Peshu N, Marsh K, Färnert A. Clearance of asymptomatic P. falciparum Infections Interacts with the number of clones to predict the risk of subsequent malaria in Kenyan children. PLoS One 2011; 6:e16940. [PMID: 21383984 PMCID: PMC3044709 DOI: 10.1371/journal.pone.0016940] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 01/17/2011] [Indexed: 12/20/2022] Open
Abstract
Background Protective immunity to malaria is acquired after repeated infections in endemic areas. Asymptomatic multiclonal P. falciparum infections are common and may predict host protection. Here, we have investigated the effect of clearing asymptomatic infections on the risk of clinical malaria. Methods Malaria episodes were continuously monitored in 405 children (1–6 years) in an area of moderate transmission, coastal Kenya. Blood samples collected on four occasions were assessed by genotyping the polymorphic P. falciparum merozoite surface protein 2 using fluorescent PCR and capillary electrophoresis. Following the second survey, asymptomatic infections were cleared with a full course of dihydroartemisinin. Results Children who were parasite negative by PCR had a lower risk of subsequent malaria regardless of whether treatment had been given. Children with ≥2 clones had a reduced risk of febrile malaria compared with 1 clone after clearance of asymptomatic infections, but not if asymptomatic infections were not cleared. Multiclonal infection was associated with an increased risk of re-infection after drug treatment. However, among the children who were re-infected, multiclonal infections were associated with a shift from clinical malaria to asymptomatic parasitaemia. Conclusion The number of clones was associated with exposure as well as blood stage immunity. These effects were distinguished by clearing asymptomatic infection with anti-malarials. Exposure to multiple P. falciparum infections is associated with protective immunity, but there appears to be an additional effect in untreated multiclonal infections that offsets this protective effect.
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Affiliation(s)
- Anne Liljander
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Philip Bejon
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, Oxford University, John Radcliffe Hospital, Oxford, United Kingdom
| | - Jedidah Mwacharo
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Oscar Kai
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Edna Ogada
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Norbert Peshu
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
| | - Kevin Marsh
- Centre for Geographical Medicine Research (Coast), Kenya Medical Research Institute, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, Oxford University, John Radcliffe Hospital, Oxford, United Kingdom
| | - Anna Färnert
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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Zeyrek FY, Tachibana SI, Yuksel F, Doni N, Palacpac N, Arisue N, Horii T, Coban C, Tanabe K. Limited polymorphism of the Plasmodium vivax merozoite surface protein 1 gene in isolates from Turkey. Am J Trop Med Hyg 2011; 83:1230-7. [PMID: 21118926 DOI: 10.4269/ajtmh.2010.10-0353] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The 200-kD merozoite surface protein of Plasmodium vivax (PvMSP-1) is one of the leading vaccine candidates against P. vivax malaria. However, the gene encoding PvMSP-1 (pvmsp1) is highly polymorphic and is a major obstacle to effective vaccine development. To further understand polymorphism in pvmsp1, we obtained 30 full-length pvmsp1 sequences from southeastern Turkey. Comparative analysis of sequences from Turkey and other areas showed substantially limited polymorphism. Substitutions were found at 280 and 162 amino acid sites in samples from other regions and those from Turkey, respectively. Eight substitutions were unique to Turkey. In one of them, D/E at position 1706 in the C-terminal 19-kD region, the K/E change at 1709 was the only polymorphism previously known. Limited diversity was also observed in microsatellites. Data suggest a recent population bottleneck in Turkey that may have obscured a signature for balancing selection in the C-terminal 42-kD region, which was otherwise detectable in other areas.
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Affiliation(s)
- Fadile Yildiz Zeyrek
- Department of Microbiology, Harran University Medical Faculty, Sanliurfa, Turkey.
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Pullan RL, Kabatereine NB, Bukirwa H, Staedke SG, Brooker S. Heterogeneities and consequences of Plasmodium species and hookworm coinfection: a population based study in Uganda. J Infect Dis 2010; 203:406-17. [PMID: 21187338 PMCID: PMC3038339 DOI: 10.1093/infdis/jiq063] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background. Previous studies have suggested that helminth infection exacerbates malaria, but few existing epidemiological studies adequately control for infection heterogeneities and confounding factors. In this study, we investigate spatial and household heterogeneities, predictors, and consequences of Plasmodium species and hookworm coinfection in rural communities in Uganda. Methods. A cross-sectional study was conducted among 1770 individuals aged 0–88 years in 4 villages. We recorded demographic, socioeconomic, and microgeographic factors during household surveys. We determined malaria parasitemia and hemoglobin concentration and collected stool samples on 2 consecutive days. For data analysis, we used a hierarchical, spatially explicit Bayesian framework. Results. Prevalence of Plasmodium-hookworm coinfection was 15.5% overall and highest among school-aged children. We found strong evidence of spatial and household clustering of coinfection and an enduring positive association between Plasmodium-species and hookworm infection among preschool-aged children (odds ratio [OR], 2.36; 95% Bayesian credible interval [BCI], 1.26–4.30) and adults (OR, 2.09; 95% BCI, 1.35–3.16) but not among school-aged children. Coinfection was associated with lower hemoglobin level only among school-aged children. Conclusions.Plasmodium-hookworm coinfection exhibits marked age dependency and significant spatial and household heterogeneity, and among preschool-aged children and adults, occurs more than would be expected by chance. Such heterogeneities provide insight into factors underlying observed patterns and the design of integrated control strategies.
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Affiliation(s)
- Rachel L Pullan
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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Baliraine FN, Afrane YA, Amenya DA, Bonizzoni M, Vardo-Zalik AM, Menge DM, Githeko AK, Yan G. A cohort study of Plasmodium falciparum infection dynamics in Western Kenya Highlands. BMC Infect Dis 2010; 10:283. [PMID: 20868504 PMCID: PMC2955685 DOI: 10.1186/1471-2334-10-283] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 09/24/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Kenyan highlands were malaria-free before the 1910s, but a series of malaria epidemics have occurred in the highlands of western Kenya since the 1980s. Longitudinal studies of the genetic structure, complexity, infection dynamics, and duration of naturally acquired Plasmodium falciparum infections are needed to facilitate a comprehensive understanding of malaria epidemiology in the complex Kenyan highland eco-epidemiological systems where malaria recently expanded, as well as the evaluation of control measures. METHODS We followed a cohort of 246 children residing in 3 villages at altitudes 1430 - 1580 m in western Kenya. Monthly parasitological surveys were undertaken for one year, yielding 866 P. falciparum isolates that were analyzed using 10 microsatellite markers. RESULTS Infection complexity and genetic diversity were high (HE = 0.787-0.816), with ≥83% of infections harboring more than one parasite clone. Diversity remained high even during the low malaria transmission season. There was no significant difference between levels of genetic diversity and population structure between high and low transmission seasons. Infection turn-over rate was high, with the average infection duration of single parasite genotypes being 1.11 months, and the longest genotype persistence was 3 months. CONCLUSIONS These data demonstrate that despite the relatively recent spread of malaria to the highlands, parasite populations seem to have stabilized with no evidence of bottlenecks between seasons, while the ability of residents to clear or control infections indicates presence of effective anti-plasmodial immune mechanisms.
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Affiliation(s)
- Frederick N Baliraine
- University of California - San Francisco, Department of Medicine, Division of Infectious Diseases, P.O. Box 0811, San Francisco, CA 94143-0811, USA
| | - Yaw A Afrane
- Center for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | | | | | | | | | - Andrew K Githeko
- Center for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Guiyun Yan
- University of California - Irvine, Irvine, CA 92697, USA
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Buchholz U, Kobbe R, Danquah I, Zanger P, Reither K, Abruquah HH, Grobusch MP, Ziniel P, May J, Mockenhaupt FP. Multiplicity of Plasmodium falciparum infection following intermittent preventive treatment in infants. Malar J 2010; 9:244. [PMID: 20796302 PMCID: PMC2939622 DOI: 10.1186/1475-2875-9-244] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 08/26/2010] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Intermittent preventive treatment in infants with sulphadoxine-pyrimethamine (IPTi-SP) reduces malaria morbidity by 20% to 33%. Potentially, however, this intervention may compromise the acquisition of immunity, including the tolerance towards multiple infections with Plasmodium falciparum. METHODS Plasmodium falciparum isolates were obtained from children participating in two Ghanaian IPTi-SP trials (Tamale, Afigya Sekyere) at 15 months of age, i.e., six months after they had received the second dose of IPTi-SP or placebo. By typing the polymorphic merozoite surface protein 1 (msp1) and msp2 genes, multiplicity of infection (MOI) was assessed in 389 isolates. A total of additional 133 samples were collected in Tamale at 3, 6, 9, and 12 months of age. Comparisons of MOI between groups were done by non-parametric statistical tests. RESULTS The number of distinguishable P. falciparum clones (MOI) ranged between one and six. Mean MOI in Tamale was stable at 2.13 - 2.17 during the first year of life, and increased to 2.57 at age 15 months (P = 0.01). At no age did MOI differ between the IPTi-SP and placebo groups (each, P ≥ 0.5). At 15 months of age, i.e., six months after the second dose, MOI was very similar for children who had received IPTi or placebo (means, 2.25 vs. 2.33; P = 0.55) as was the proportion of polyclonal infections (69.6% vs. 69.7%; P = 0.99). Adjusting for study site, current and prior malaria, parasite density, and season did not change this finding. CONCLUSIONS IPTi-SP appears to have no impact on the multiplicity of infection during infancy and thereafter. This suggests that tolerance of multiple infections, a component of protective immunity in highly endemic areas, is not affected by this intervention.
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Affiliation(s)
- Ulrike Buchholz
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
| | - Robin Kobbe
- Infectious Disease Epidemiology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Ina Danquah
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
| | - Philipp Zanger
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Klaus Reither
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Harry H Abruquah
- Division of Microbiology and Infectious Diseases, University Hospital, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Martin P Grobusch
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- Medical Research Unit, Hôpital Albert Schweitzer, Lambaréné, Gabon
- Department of Infectious Diseases, Tropical Medicine, HIV/AIDS, Amsterdam Medical Center, University of Amsterdam, The Netherlands
| | - Peter Ziniel
- Northern Region Malaria Project, Tamale, Ghana
- Dept. of Immunology & Microbiology, Rush University, Chicago, USA
| | - Jürgen May
- Infectious Disease Epidemiology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Frank P Mockenhaupt
- Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany
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Sutton PL, Neyra V, Hernandez JN, Branch OH. Plasmodium falciparum and Plasmodium vivax infections in the Peruvian Amazon: propagation of complex, multiple allele-type infections without super-infection. Am J Trop Med Hyg 2010; 81:950-60. [PMID: 19996422 DOI: 10.4269/ajtmh.2009.09-0132] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Outcrossing potential between Plasmodium parasites is defined by the population-level diversity (PLD) and complexity of infection (COI). There have been few studies of PLD and COI in low transmission regions. Since the 1995-1998 Peruvian Amazon epidemic, there has been sustained transmission with < 0.5 P. falciparum and < 1.6 P. vivax infections/person/year. Using weekly active case detection, we described PLD by heterozygosity (H(e)) and COI using P. falciparum Pfmsp1-B2 and P. vivax Pvmsp3alpha. Not being homologous genes, we limited comparisons to within species. P. falciparum (N = 293) had low (H(e) = 0.581) and P. vivax (N = 186) had high (H(e) = 0.845) PLD. A total of 9.5% P. falciparum infections and 26.3% P. vivax infections had COI > 1. Certain allele types were in more mixed infections than expected by chance. The few appearances of new alleles could be explained by stochastic polymerase chain reaction detection or synchronization/sequestration. The results suggest propagation of mixed infections by multiple inocula, not super-infection, implying decade-long opportunity for outcrossing in these mixed infections.
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Affiliation(s)
- Patrick L Sutton
- Department of Infectious Diseases, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Färnert A, Williams TN, Mwangi TW, Ehlin A, Fegan G, Macharia A, Lowe BS, Montgomery SM, Marsh K. Transmission-dependent tolerance to multiclonal Plasmodium falciparum infection. J Infect Dis 2009; 200:1166-75. [PMID: 19702508 DOI: 10.1086/605652] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Whether the number of concurrent clones in asymptomatic Plasmodium falciparum infections reflects the degree of host protection was investigated in children living in areas with different levels of transmission on the coast of Kenya. The number of concurrent clones was determined on the basis of polymorphism in msp2, which encodes the vaccine candidate antigen merozoite surface protein 2. In a low-transmission area, most children had monoclonal infections, and diversity did not predict a risk of clinical malaria. In an area of moderate transmission, asymptomatic infections with 2 clones were, compared with 1 clone, associated with an increased risk of subsequent malaria. In a comparative assessment in a high-transmission area in Tanzania, multiclonal infections conferred a reduced risk. The different nonlinear associations between the number of clones and malaria morbidity suggest that levels of tolerance to multiclonal infections are transmission dependent as a result of cumulative exposure to antigenically diverse P. falciparum infections.
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Affiliation(s)
- Anna Färnert
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
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32
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Population dynamics of genetically diverse Plasmodium falciparum lineages: community-based prospective study in rural Amazonia. Parasitology 2009; 136:1097-105. [PMID: 19631016 DOI: 10.1017/s0031182009990539] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Temporal changes in the prevalence of antigenic variants in Plasmodium falciparum populations have been interpreted as evidence of immune-mediated frequency-dependent selection, but evolutively neutral processes may generate similar patterns of serotype replacement. Over 4 years, we investigated the population dynamics of P. falciparum polymorphisms at the community level by using 11 putatively neutral microsatellite markers. Plasmodium falciparum populations were less diverse than sympatric P. vivax isolates, with less multiple-clone infections, lower number of alleles per locus and lower virtual heterozygosity, but both species showed significant multilocus linkage disequilibrium. Evolutively neutral P. falciparum polymorphisms showed a high turnover rate, with few lineages persisting for several months in the population. Similar results had previously been obtained, in the same community, for sympatric P. vivax isolates. In contrast, the prevalence of the 2 dimorphic types of a major antigen, MSP-2, remained remarkably stable throughout the study period. We suggest that the relatively fast turnover of parasite lineages represents the typical population dynamics of neutral polymorphisms in small populations, with clear implications for the detection of frequency-dependent selection of polymorphisms.
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Israelsson E, Vafa M, Maiga B, Lysén A, Iriemenam NC, Dolo A, Doumbo OK, Troye-Blomberg M, Berzins K. Differences in Fcgamma receptor IIa genotypes and IgG subclass pattern of anti-malarial antibodies between sympatric ethnic groups in Mali. Malar J 2008; 7:175. [PMID: 18793404 PMCID: PMC2553417 DOI: 10.1186/1475-2875-7-175] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 09/15/2008] [Indexed: 11/29/2022] Open
Abstract
Background The Ig Fc receptor family is an important link between the humoral and cellular immune systems. The association of a dimorphism in amino acid 131 (R/H) of the FcγRIIa with malaria severity, the R-allele being associated with a milder disease outcome, led to the investigation of the possible impact of this polymorphism in the interethnic difference in malaria susceptibility seen between the Fulani and Dogon in Mali. Methods Plasma from individuals from Mali (164 Fulani and 164 Dogon) were analysed for malaria-reactive and total IgG subclass antibodies using ELISA, and the same individuals were also genotyped for the FcγRIIa R131H polymorphism using RFLP-PCR. Statistical analyses of the IgG subclass levels were done by unpaired t-test and ANOVA, and genotype differences were tested by χ2-test. Results While the two ethnic groups showed a similar frequency of the FcγRIIa 131 R/H heterozygote genotype, 131R/R dominated over the 131 H/H genotype in the Dogon whereas the Fulani presented a similar frequency of the two homozygote genotypes. The two alleles were evenly distributed in the Fulani, while the Dogon were clearly biased towards the R-allele. The Fulani showed higher levels of anti-malarial IgG1, -2 and -3 antibodies, with a higher proportion of IgG2, than the Dogon. In the Fulani, H-allele carriers had higher anti-malarial IgG2 levels than R/R homozygotes, while in the Dogon, the R-allele carriers showed the higher IgG2 levels. For anti-malarial IgG3, the R-allele carriers in the Fulani had higher levels than the H/H homozygotes. Conclusion Taken together, the results showed marked interethnic differences in FcγRIIa R131H genotypes. Furthermore, the results indicate that the FcγRIIa R131H genotype may influence the IgG subclass responses related to protection against malaria, and that IgG2 may be of importance in this context.
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Affiliation(s)
- Elisabeth Israelsson
- Department of Immunology, Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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