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Tran T, Ekenna C. Molecular Descriptors Property Prediction Using Transformer-Based Approach. Int J Mol Sci 2023; 24:11948. [PMID: 37569322 PMCID: PMC10419034 DOI: 10.3390/ijms241511948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 07/21/2023] [Accepted: 07/24/2023] [Indexed: 08/13/2023] Open
Abstract
In this study, we introduce semi-supervised machine learning models designed to predict molecular properties. Our model employs a two-stage approach, involving pre-training and fine-tuning. Particularly, our model leverages a substantial amount of labeled and unlabeled data consisting of SMILES strings, a text representation system for molecules. During the pre-training stage, our model capitalizes on the Masked Language Model, which is widely used in natural language processing, for learning molecular chemical space representations. During the fine-tuning stage, our model is trained on a smaller labeled dataset to tackle specific downstream tasks, such as classification or regression. Preliminary results indicate that our model demonstrates comparable performance to state-of-the-art models on the chosen downstream tasks from MoleculeNet. Additionally, to reduce the computational overhead, we propose a new approach taking advantage of 3D compound structures for calculating the attention score used in the end-to-end transformer model to predict anti-malaria drug candidates. The results show that using the proposed attention score, our end-to-end model is able to have comparable performance with pre-trained models.
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Masserey T, Penny MA, Lee TE. Patient variability in the blood-stage dynamics of Plasmodium falciparum captured by clustering historical data. Malar J 2022; 21:300. [PMID: 36289505 PMCID: PMC9608883 DOI: 10.1186/s12936-022-04317-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 10/11/2022] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Mathematical models provide an understanding of the dynamics of a Plasmodium falciparum blood-stage infection (within-host models), and can predict the impact of control strategies that affect the blood-stage of malaria. However, the dynamics of P. falciparum blood-stage infections are highly variable between individuals. Within-host models use different techniques to capture this inter-individual variation. This struggle may be unnecessary because patients can be clustered according to similar key within-host dynamics. This study aimed to identify clusters of patients with similar parasitaemia profiles so that future mathematical models can include an improved understanding of within-host variation. METHODS Patients' parasitaemia data were analyzed to identify (i) clusters of patients (from 35 patients) that have a similar overall parasitaemia profile and (ii) clusters of patients (from 100 patients) that have a similar first wave of parasitaemia. For each cluster analysis, patients were clustered based on key features which previous models used to summarize parasitaemia dynamics. The clustering analyses were performed using a finite mixture model. The centroid values of the clusters were used to parameterize two established within-host models to generate parasitaemia profiles. These profiles (that used the novel centroid parameterization) were compared with profiles that used individual-specific parameterization (as in the original models), as well as profiles that ignored individual variation (using overall means for parameterization). RESULTS To capture the variation of within-host dynamics, when studying the overall parasitaemia profile, two clusters efficiently grouped patients based on their infection length and the height of the first parasitaemia peak. When studying the first wave of parasitaemia, five clusters efficiently grouped patients based on the height of the peak and the speed of the clearance following the peak of parasitaemia. The clusters were based on features that summarize the strength of patient innate and adaptive immune responses. Parameterizing previous within host-models based on cluster centroid values accurately predict individual patient parasitaemia profiles. CONCLUSION This study confirms that patients have personalized immune responses, which explains the variation of parasitaemia dynamics. Clustering can guide the optimal inclusion of within-host variation in future studies, and inform the design and parameterization of population-based models.
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Affiliation(s)
- Thiery Masserey
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Basel-Land, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Basel-Land, Switzerland
- University of Basel, Basel, Switzerland
| | - Tamsin E Lee
- Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Basel-Land, Switzerland
- University of Basel, Basel, Switzerland
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3
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Kamau A, Paton RS, Akech S, Mpimbaza A, Khazenzi C, Ogero M, Mumo E, Alegana VA, Agweyu A, Mturi N, Mohammed S, Bigogo G, Audi A, Kapisi J, Sserwanga A, Namuganga JF, Kariuki S, Otieno NA, Nyawanda BO, Olotu A, Salim N, Athuman T, Abdulla S, Mohamed AF, Mtove G, Reyburn H, Gupta S, Lourenço J, Bejon P, Snow RW. Malaria hospitalisation in East Africa: age, phenotype and transmission intensity. BMC Med 2022; 20:28. [PMID: 35081974 PMCID: PMC8793189 DOI: 10.1186/s12916-021-02224-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/21/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Understanding the age patterns of disease is necessary to target interventions to maximise cost-effective impact. New malaria chemoprevention and vaccine initiatives target young children attending routine immunisation services. Here we explore the relationships between age and severity of malaria hospitalisation versus malaria transmission intensity. METHODS Clinical data from 21 surveillance hospitals in East Africa were reviewed. Malaria admissions aged 1 month to 14 years from discrete administrative areas since 2006 were identified. Each site-time period was matched to a model estimated community-based age-corrected parasite prevalence to provide predictions of prevalence in childhood (PfPR2-10). Admission with all-cause malaria, severe malaria anaemia (SMA), respiratory distress (RD) and cerebral malaria (CM) were analysed as means and predicted probabilities from Bayesian generalised mixed models. RESULTS 52,684 malaria admissions aged 1 month to 14 years were described at 21 hospitals from 49 site-time locations where PfPR2-10 varied from < 1 to 48.7%. Twelve site-time periods were described as low transmission (PfPR2-10 < 5%), five low-moderate transmission (PfPR2-10 5-9%), 20 moderate transmission (PfPR2-10 10-29%) and 12 high transmission (PfPR2-10 ≥ 30%). The majority of malaria admissions were below 5 years of age (69-85%) and rare among children aged 10-14 years (0.7-5.4%) across all transmission settings. The mean age of all-cause malaria hospitalisation was 49.5 months (95% CI 45.1, 55.4) under low transmission compared with 34.1 months (95% CI 30.4, 38.3) at high transmission, with similar trends for each severe malaria phenotype. CM presented among older children at a mean of 48.7 months compared with 39.0 months and 33.7 months for SMA and RD, respectively. In moderate and high transmission settings, 34% and 42% of the children were aged between 2 and 23 months and so within the age range targeted by chemoprevention or vaccines. CONCLUSIONS Targeting chemoprevention or vaccination programmes to areas where community-based parasite prevalence is ≥10% is likely to match the age ranges covered by interventions (e.g. intermittent presumptive treatment in infancy to children aged 2-23 months and current vaccine age eligibility and duration of efficacy) and the age ranges of highest disease burden.
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Affiliation(s)
- Alice Kamau
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya.
| | | | - Samuel Akech
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Arthur Mpimbaza
- Child Health and Development Centre, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Cynthia Khazenzi
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Morris Ogero
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Eda Mumo
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Victor A Alegana
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Ambrose Agweyu
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
| | - Neema Mturi
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Kilifi, Kenya
| | - Shebe Mohammed
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Kilifi, Kenya
| | - Godfrey Bigogo
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Allan Audi
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - James Kapisi
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | | | - Simon Kariuki
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Nancy A Otieno
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Bryan O Nyawanda
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Ally Olotu
- Ifakara Health Institute, Bagamoyo, Tanzania
| | - Nahya Salim
- Ifakara Health Institute, Bagamoyo, Tanzania
| | | | | | - Amina F Mohamed
- Kilimanjaro Christian Medical Centre/Joint Malaria Programme, Moshi, Tanzania
- London School of Hygiene and Tropical Medicine, London, UK
| | - George Mtove
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Hugh Reyburn
- London School of Hygiene and Tropical Medicine, London, UK
| | - Sunetra Gupta
- Department of Zoology, University of Oxford, Oxford, UK
| | - José Lourenço
- Department of Zoology, University of Oxford, Oxford, UK
| | - Philip Bejon
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Robert W Snow
- Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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Antimalarial Drug Predictions Using Molecular Descriptors and Machine Learning against Plasmodium Falciparum. Biomolecules 2021; 11:biom11121750. [PMID: 34944394 PMCID: PMC8698534 DOI: 10.3390/biom11121750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/12/2021] [Accepted: 11/17/2021] [Indexed: 11/16/2022] Open
Abstract
Malaria remains by far one of the most threatening and dangerous illnesses caused by the plasmodium falciparum parasite. Chloroquine (CQ) and first-line artemisinin-based combination treatment (ACT) have long been the drug of choice for the treatment and controlling of malaria; however, the emergence of CQ-resistant and artemisinin resistance parasites is now present in most areas where malaria is endemic. In this work, we developed five machine learning models to predict antimalarial bioactivities of a drug against plasmodium falciparum from the features (i.e., molecular descriptors values) obtained from PaDEL software from SMILES of compounds and compare the machine learning models by experiments with our collected data of 4794 instances. As a consequence, we found that three models amongst the five, namely artificial neural network (ANN), extreme gradient boost (XGB), and random forest (RF), outperform the others in terms of accuracy while observing that, using roughly a quarter of the promising descriptors picked by the feature selection algorithm, the five models achieved equivalent and comparable performance. Nevertheless, the contribution of all molecular descriptors in the models was investigated through the comparison of their rank values by the feature selection algorithm and found that the most potent and relevant descriptors which come from the ‘Autocorrelation’ module contributed more while the ‘Atom type electrotopological state’ contributed the least to the model.
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Daniyan MO. Heat Shock Proteins as Targets for Novel Antimalarial Drug Discovery. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1340:205-236. [PMID: 34569027 DOI: 10.1007/978-3-030-78397-6_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Plasmodium falciparum, the parasitic agent that is responsible for a severe and dangerous form of human malaria, has a history of long years of cohabitation with human beings with attendant negative consequences. While there have been some gains in the fight against malaria through the application of various control measures and the use of chemotherapeutic agents, and despite the global decline in malaria cases and associated deaths, the continual search for new and effective therapeutic agents is key to achieving sustainable development goals. An important parasite survival strategy, which is also of serious concern to the scientific community, is the rate at which the parasites continually develop resistance to drugs. Among the key players in the parasite's ability to develop resistance, maintain cellular integrity, and survives within an unusual environment of the red blood cells are the molecular chaperones of the heat shock proteins (HSP) family. HSPs constitute a novel avenue for antimalarial drug discovery and by exploring their ubiquitous nature and multifunctional activities, they may be suitable targets for the discovery of multi-targets antimalarial drugs, needed to fight incessant drug resistance. In this chapter, features of selected families of plasmodial HSPs that can be exploited in drug discovery are presented. Also, known applications of HSPs in small molecule screening, their potential usefulness in high throughput drug screening, as well as possible challenges are highlighted.
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Affiliation(s)
- Michael Oluwatoyin Daniyan
- Department of Pharmacology, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria.
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Paton RS, Kamau A, Akech S, Agweyu A, Ogero M, Mwandawiro C, Mturi N, Mohammed S, Mpimbaza A, Kariuki S, Otieno NA, Nyawanda BO, Mohamed AF, Mtove G, Reyburn H, Gupta S, Bejon P, Lourenço J, Snow RW. Malaria infection and severe disease risks in Africa. Science 2021; 373:926-931. [PMID: 34413238 PMCID: PMC7611598 DOI: 10.1126/science.abj0089] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/29/2021] [Indexed: 12/18/2022]
Abstract
The relationship between community prevalence of Plasmodium falciparum and the burden of severe, life-threatening disease remains poorly defined. To examine the three most common severe malaria phenotypes from catchment populations across East Africa, we assembled a dataset of 6506 hospital admissions for malaria in children aged 3 months to 9 years from 2006 to 2020. Admissions were paired with data from community parasite infection surveys. A Bayesian procedure was used to calibrate uncertainties in exposure (parasite prevalence) and outcomes (severe malaria phenotypes). Each 25% increase in prevalence conferred a doubling of severe malaria admission rates. Severe malaria remains a burden predominantly among young children (3 to 59 months) across a wide range of community prevalence typical of East Africa. This study offers a quantitative framework for linking malaria parasite prevalence and severe disease outcomes in children.
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Affiliation(s)
- Robert S Paton
- Department of Zoology, University of Oxford, Oxford, UK.
| | - Alice Kamau
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Samuel Akech
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Ambrose Agweyu
- Kilimanjaro Christian Medical Centre/Joint Malaria Programme, Moshi, Tanzania
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Morris Ogero
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Charles Mwandawiro
- Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute (KEMRI), Nairobi, Kenya
| | - Neema Mturi
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Shebe Mohammed
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Arthur Mpimbaza
- Child Health and Development Centre, Makerere University, College of Health Sciences, Kampala, Uganda
| | - Simon Kariuki
- Kenya Medical Research Institute (KEMRI)-Centre for Global Health Research, Kisumu, Kenya
| | - Nancy A Otieno
- Kenya Medical Research Institute (KEMRI)-Centre for Global Health Research, Kisumu, Kenya
| | - Bryan O Nyawanda
- Kenya Medical Research Institute (KEMRI)-Centre for Global Health Research, Kisumu, Kenya
| | - Amina F Mohamed
- Kilimanjaro Christian Medical Centre/Joint Malaria Programme, Moshi, Tanzania
- London School of Hygiene and Tropical Medicine, London, UK
| | - George Mtove
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Hugh Reyburn
- London School of Hygiene and Tropical Medicine, London, UK
| | - Sunetra Gupta
- Department of Zoology, University of Oxford, Oxford, UK
| | - Philip Bejon
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Kilifi, Kenya
| | - José Lourenço
- Department of Zoology, University of Oxford, Oxford, UK
| | - Robert W Snow
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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7
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Bailey C, Strepparava N, Ros A, Wahli T, Schmidt-Posthaus H, Segner H, Tafalla C. It's a hard knock life for some: Heterogeneity in infection life history of salmonids influences parasite disease outcomes. J Anim Ecol 2021; 90:2573-2593. [PMID: 34165799 PMCID: PMC8597015 DOI: 10.1111/1365-2656.13562] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 06/19/2021] [Indexed: 11/27/2022]
Abstract
Heterogeneity in immunity occurs across numerous disease systems with individuals from the same population having diverse disease outcomes. Proliferative kidney disease (PKD) caused by Tetracapsuloides bryosalmonae, is a persistent parasitic disease negatively impacting both wild and farmed salmonids. Little is known of how PKD is spread or maintained within wild susceptible populations. We investigated an aspect of fish disease that has been largely overlooked, that is, the role of the host phenotypic heterogeneity in disease outcome. We examined how host susceptibility to T. bryosalmonae infection, and the disease PKD, varied across different infection life-history stages and how it differs between naïve, re-infected and persistently infected hosts. We investigated the response to parasite exposure in host phenotypes with (a) different ages and (b) heterogeneous infection life histories. Among (a) the age phenotypes were young-of-the-year (YOY) fish and juvenile 1+ fish (fish older than one) and, for (b) juvenile 1+ infection survivors were either re-exposed or not re- exposed to the parasite and response phenotypes were assigned post-hoc dependant on infection status. In fish not re-exposed this included fish that cleared infection (CI) or had a persistent infection (PI). In fish re-exposed these included fish that were re-infected (RI), or re-exposed and uninfected (RCI). We assessed both parasite-centric (infection prevalence, parasite burden, malacospore transmission) and host-centric parameters (growth rates, disease severity, infection tolerance and the immune response). In (a), YOY fish, parasite success and disease severity were greater and differences in the immune response occurred, demonstrating an ontogenetic decline of susceptibility in older fish. In (b), in PI and RI fish, parasite success and disease severity were comparable. However, expression of several adaptive immunity markers was greater in RI fish, indicating concomitant immunity, as re-exposure did not intensify infection. We demonstrate the relevance of heterogeneity in infection life history on disease outcome and describe several distinctive features of immune ontogeny and protective immunity in this model not previously reported. The relevance of such themes on a population level requires greater research in many aquatic disease systems to generate clearer framework for understanding the spread and maintenance of aquatic pathogens.
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Affiliation(s)
- Christyn Bailey
- Fish Immunology and Pathology Group, Animal Health Research Centre (CISA-INIA), Madrid, Spain
| | - Nicole Strepparava
- Centre for Fish and Wildlife Health, University of Bern, Bern, Switzerland
| | - Albert Ros
- LAZBW, Fischereiforschungsstelle, Langenargen, Germany
| | - Thomas Wahli
- Centre for Fish and Wildlife Health, University of Bern, Bern, Switzerland
| | | | - Helmut Segner
- Centre for Fish and Wildlife Health, University of Bern, Bern, Switzerland
| | - Carolina Tafalla
- Fish Immunology and Pathology Group, Animal Health Research Centre (CISA-INIA), Madrid, Spain
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8
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Björkman A, Morris U. Why Asymptomatic Plasmodium falciparum Infections Are Common in Low-Transmission Settings. Trends Parasitol 2020; 36:898-905. [PMID: 32855077 DOI: 10.1016/j.pt.2020.07.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/18/2020] [Accepted: 07/18/2020] [Indexed: 12/22/2022]
Abstract
Plasmodium falciparum infections in low-transmission settings are often asymptomatic with low parasite densities despite low herd immunity. Based on studies in Zanzibar, this may be due to parasitic (nonvirulence) rather than host (immunity) factors. In high-transmission settings, high replication rate and virulence represents a competitive advantage, whereas in low-transmission settings nonvirulent parasites escape both competition and treatment. Such parasites also survive longer in low-transmission settings due to lower host immunity response and less frequent indirect drug exposure. This has major implications for optimal malaria control and elimination strategies.
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9
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Daniyan MO, Przyborski JM, Shonhai A. Partners in Mischief: Functional Networks of Heat Shock Proteins of Plasmodium falciparum and Their Influence on Parasite Virulence. Biomolecules 2019; 9:E295. [PMID: 31340488 PMCID: PMC6681276 DOI: 10.3390/biom9070295] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/28/2019] [Accepted: 06/28/2019] [Indexed: 02/06/2023] Open
Abstract
The survival of the human malaria parasite Plasmodium falciparum under the physiologically distinct environments associated with their development in the cold-blooded invertebrate mosquito vectors and the warm-blooded vertebrate human host requires a genome that caters to adaptability. To this end, a robust stress response system coupled to an efficient protein quality control system are essential features of the parasite. Heat shock proteins constitute the main molecular chaperone system of the cell, accounting for approximately two percent of the malaria genome. Some heat shock proteins of parasites constitute a large part (5%) of the 'exportome' (parasite proteins that are exported to the infected host erythrocyte) that modify the host cell, promoting its cyto-adherence. In light of their importance in protein folding and refolding, and thus the survival of the parasite, heat shock proteins of P. falciparum have been a major subject of study. Emerging evidence points to their role not only being cyto-protection of the parasite, as they are also implicated in regulating parasite virulence. In undertaking their roles, heat shock proteins operate in networks that involve not only partners of parasite origin, but also potentially functionally associate with human proteins to facilitate parasite survival and pathogenicity. This review seeks to highlight these interplays and their roles in parasite pathogenicity. We further discuss the prospects of targeting the parasite heat shock protein network towards the developments of alternative antimalarial chemotherapies.
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Affiliation(s)
- Michael O Daniyan
- Department of Pharmacology, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Osun State 220005, Nigeria.
| | - Jude M Przyborski
- Center of Infectious Diseases, Parasitology, University of Heidelberg Medical School, INF324, 69120 Heidelberg, Germany
| | - Addmore Shonhai
- Department of Biochemistry, School of Mathematical & Natural Sciences, University of Venda, P. Bag X5050, Thohoyandou 0950, South Africa.
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10
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Sondo P, Derra K, Lefevre T, Diallo-Nakanabo S, Tarnagda Z, Zampa O, Kazienga A, Valea I, Sorgho H, Ouedraogo JB, Guiguemde TR, Tinto H. Genetically diverse Plasmodium falciparum infections, within-host competition and symptomatic malaria in humans. Sci Rep 2019; 9:127. [PMID: 30644435 PMCID: PMC6333925 DOI: 10.1038/s41598-018-36493-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 11/16/2018] [Indexed: 11/17/2022] Open
Abstract
There is a large genetic diversity of Plasmodium falciparum strains that infect people causing diverse malaria symptoms. This study was carried out to explore the effect of mixed-strain infections and the extent to which some specific P. falciparum variants are associated with particular malaria symptoms. P. falciparum isolates collected during pharmacovigilance study in Nanoro, Burkina Faso were used to determine allelic variation in two polymorphic antigens of the merozoite surface (msp1 and msp2). Overall, parasite density did not increase with additional strains, suggesting the existence of within-host competition. Parasite density was influenced by msp1 allelic families with highest parasitaemia observed in MAD20 allelic family. However, when in mixed infections with allelic family K1, MAD20 could not grow to the same levels as it would alone, suggesting competitive suppression in these mixed infections. Host age was associated with parasite density. Overall, older patients exhibited lower parasite densities than younger patients, but this effect varied with the genetic composition of the isolates for the msp1 gene. There was no effect of msp1 and msp2 allelic family variation on body temperature. Haemoglobin level was influenced by msp2 family with patients harboring the FC27 allele showing lower haemoglobin level than mono-infected individuals by the 3D7 allele. This study provides evidence that P. falciparum genetic diversity influenced the severity of particular malaria symptoms and supports the existence of within-host competition in genetically diverse P. falciparum.
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Affiliation(s)
- Paul Sondo
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso.
| | - Karim Derra
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | - Thierry Lefevre
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso.,MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France
| | - Seydou Diallo-Nakanabo
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | - Zekiba Tarnagda
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | - Odile Zampa
- Centre Muraz of Bobo-Dioulasso, Bobo-Dioulasso, Burkina Faso
| | - Adama Kazienga
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | - Innocent Valea
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso.,Centre Muraz of Bobo-Dioulasso, Bobo-Dioulasso, Burkina Faso
| | - Hermann Sorgho
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | - Jean-Bosco Ouedraogo
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso
| | | | - Halidou Tinto
- Institut de Recherche en Sciences de la Santé (IRSS)/Clinical Research Unit of Nanoro (CRUN), Nanoro, Burkina Faso.,Centre Muraz of Bobo-Dioulasso, Bobo-Dioulasso, Burkina Faso
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11
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Mandala WL, Gondwe EN, Nyirenda TS, Drayson M, Molyneux ME, MacLennan CA. HIV infection compounds the lymphopenia associated with cerebral malaria in Malawian children. J Blood Med 2018; 10:9-18. [PMID: 30588141 PMCID: PMC6305159 DOI: 10.2147/jbm.s187081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Aim Cerebral malaria (CM), unlike severe malarial anemia (SMA), has previously been characterized by pan-lymphopenia that normalizes in convalescence, while HIV infection is associated with depletion of CD4+ T cells. In this study, we investigate whether HIV infection in Malawian children exacerbates the pan-lymphopenia associated with CM. Methods We investigated the absolute and percentage lymphocyte-subset counts and their activation and memory status in Malawian children presenting with either CM who were HIV-uninfected (n=29), HIV-infected (n=9), or SMA who were HIV-uninfected (n=30) and HIV-infected (n=5) in comparison with HIV-uninfected children without malaria (n=42) and HIV-infected children without malaria (n=4). Results HIV-infected CM cases had significantly lower absolute counts of T cells (P=0.006), CD4+ T cells (P=0.0008), and B cells (P=0.0014) than HIV-uninfected CM cases, and significantly lower percentages of CD4+ T cells than HIV-uninfected CM cases (P=0.005). HIV-infected SMA cases had significantly lower percentages of CD4+ T cells (P=0.001) and higher CD8+ T cells (P=0.003) in comparison with HIV-uninfected SMA cases. HIV-infected SMA cases had higher proportions of activated T cells (P=0.003) expressing CD69 than HIV-uninfected SMA cases. Conclusion HIV infection compounds the perturbation of acute CM and SMA on lymphocytes, exacerbating subset-specific lymphopenia in CM and increasing activation status in SMA, potentially exacerbating host immunocompromise.
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Affiliation(s)
- Wilson L Mandala
- Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi, .,Biomedical Sciences Department, College of Medicine, Blantyre, Malawi, .,Academy of Medical Sciences, Malawi University of Science and Technology, Thyolo, Malawi,
| | - Esther N Gondwe
- Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi,
| | - Tonney S Nyirenda
- Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi, .,Pathology Department, College of Medicine, Blantyre, Malawi
| | - Mark Drayson
- Institute of Immunology and Immunotherapy, College of Medicine and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Malcolm E Molyneux
- Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi, .,Liverpool School of Tropical Medicine, Liverpool, UK
| | - Calman A MacLennan
- Malawi Liverpool Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi, .,Jenner Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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Jumanne S, Meda J, Hokororo A, Leshabari K. Clinical Predictors of Malaria, Acute Bacterial Meningitis and Treatment Outcomes among Febrile Children Admitted with Altered Mental Status in Northwestern Tanzania. J Trop Pediatr 2018; 64:426-433. [PMID: 29206991 DOI: 10.1093/tropej/fmx090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Malaria and acute bacterial meningitis (ABM) are the leading infectious causes of febrile encephalopathy in malaria endemic settings. The clinical distinction of the two conditions is complicated by overlap in clinical features. OBJECTIVE To determine the clinical predictors for malaria, ABM and treatment outcome in febrile children aged 2 months to 12 years with altered mentation at two tertiary hospitals in Northwestern Tanzania. METHODS Prospective study of 103 children to document demographic data and physical examination findings, such as level of consciousness and meningeal irritations. Laboratory results for cerebrospinal fluid, hemoglobin, malaria and HIV were also evaluated. RESULTS Age >60 months and hemoglobin ≤5 g/dl were independent predictors of malaria; (p = 0.013 and 0.004, respectively). HIV infection was the only predictor of meningitis, p = 0.037, and mortality was high if the diagnosis was unconfirmed. CONCLUSIONS Children with febrile encephalopathy are more likely to have malaria than ABM if they have severe anemia.
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Affiliation(s)
- Shakilu Jumanne
- Department of Pediatrics & Child Health, College of Health Sciences, University of Dodoma, Dodoma, Tanzania.,Department of Pediatrics & Child Health, Catholic University of Health and Allied sciences, Mwanza, Mwanza, Tanzania
| | - John Meda
- Department of Pediatrics & Child Health, College of Health Sciences, University of Dodoma, Dodoma, Tanzania
| | - Adolfine Hokororo
- Department of Pediatrics & Child Health, Catholic University of Health and Allied sciences, Mwanza, Mwanza, Tanzania
| | - Kelvin Leshabari
- Department of Medicine, Walter Hospital, Dar es, Salaam, Tanzania
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Predictive classifier models built from natural products with antimalarial bioactivity using machine learning approach. PLoS One 2018; 13:e0204644. [PMID: 30265702 PMCID: PMC6161899 DOI: 10.1371/journal.pone.0204644] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 09/12/2018] [Indexed: 11/19/2022] Open
Abstract
In view of the vast number of natural products with potential antiplasmodial bioactivity and cost of conducting antiplasmodial bioactivity assays, it may be judicious to learn from previous antiplasmodial bioassays and predict bioactivity of these natural products before experimental bioassays. This study set out to harness antimalarial bioactivity data of natural products to build accurate predictive models, utilizing classical machine learning approaches, which can find potential antimalarial hits from new sets of natural products. Classical machine learning approaches were used to build four classifier models (Naïve Bayesian, Voted Perceptron, Random Forest and Sequence Minimization Optimization of Support Vector Machines) from bioactivity data of natural products with in-vitro antiplasmodial activity (NAA) using a combination of the molecular descriptors and two-dimensional molecular fingerprints of the compounds. Models were evaluated with an independent test dataset. Possible chemical features associated with reported antimalarial activities of the compounds were also extracted. From the results, Random Forest (accuracy 82.81%, Kappa statistics 0.65 and Area under Receiver Operating Characteristics curve 0.91) and Sequential Minimization Optimization (accuracy 85.93%, Kappa statistics 0.72 and Area under Receiver Operating Characteristics curve 0.86) showed good predictive performance for the NAA dataset. The amine chemical group (specifically alkyl amines and basic nitrogen) was confirmed to be essential for antimalarial activity in active NAA dataset. This study built and evaluated classifier models that were used to predict the antiplasmodial bioactivity class (active or inactive) of a set of natural products from interBioScreen chemical library.
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Sequence variation in Plasmodium falciparum merozoite surface protein-2 is associated with virulence causing severe and cerebral malaria. PLoS One 2018; 13:e0190418. [PMID: 29342212 PMCID: PMC5771562 DOI: 10.1371/journal.pone.0190418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/14/2017] [Indexed: 11/20/2022] Open
Abstract
Parasite virulence, an important factor contributing to the severity of Plasmodium falciparum infection, varies among P. falciparum strains. Relatively little is known regarding markers of virulence capable of identifying strains responsible for severe malaria. We investigated the effects of genetic variations in the P.f. merozoite surface protein 2 gene (msp2) on virulence, as it was previously postulated as a factor. We analyzed 300 msp2 sequences of single P. falciparum clone infection from patients with uncomplicated disease as well as those admitted for severe malaria with and without cerebral disease. The association of msp2 variations with disease severity was examined. We found that the N allele at codon 8 of Block 2 in the FC27-like msp2 gene was significantly associated with severe disease without cerebral complications (odds ratio = 2.73, P = 0.039), while the K allele at codon 17 of Block 4 in the 3D7-like msp2 gene was associated with cerebral malaria (odds ratio = 3.52, P = 0.024). The data suggests possible roles for the associated alleles on parasite invasion processes and immune-mediated pathogenicity. Multiplicity of infection was found to associate with severe disease without cerebral complications, but not cerebral malaria. Variations in the msp2-FC27-block 2-8N and 3D7-block 4-17K allele appear to be parasite virulence markers, and may be useful in determining the likelihood for severe and cerebral malaria. Their interactions with potential host factors for severe diseases should also be explored.
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Botwe AK, Asante KP, Adjei G, Assafuah S, Dosoo D, Owusu-Agyei S. Dynamics in multiplicity of Plasmodium falciparum infection among children with asymptomatic malaria in central Ghana. BMC Genet 2017; 18:67. [PMID: 28716086 PMCID: PMC5514501 DOI: 10.1186/s12863-017-0536-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 07/11/2017] [Indexed: 12/18/2022] Open
Abstract
Background The determinants of malaria parasite virulence is not entirely known, but the outcome of malaria infection (asymptomatic or symptomatic) has been associated with carriage of distinct parasite genotypes. Alleles considered important for erythrocyte invasion and selected as candidate targets for malaria vaccine development are increasingly being shown to have distinct characteristics in infection outcomes. Any unique/distinct patterns or alleles linked to infection outcome should be reproducible for a given malaria-cohort regardless of location, time or intervention. This study compared merozoite surface protein 2 (MSP2) genotypes from children with asymptomatic malaria at same geographical location, from two time periods. Results As the prevalence and incidence of malaria (measured for other studies) significantly reduced between 2004 (time point one) and 2009 (time point two), MSP2 multiplicity of infections (MOI) also reduced significantly from 2.3 at time point (TP) one to 1.9 at TP two. IC/3D7 genotypes out-numbered FC27 genotypes at both time points. At TP2 however, FC27 allele diversity was more than the IC/3D7 allele diversity. A decrease in the IC/3D7:FC27 genotype proportions from 2:1 at TP1 to 1:1 at TP2, seemed to be driven mainly by a decrease in carriage of IC/3D7 alleles. MOI was higher in the dry season than in the subsequent wet season, but the decrease was not significant at TP2. Conclusion MSP2 MOI was higher in the dry season than in the subsequent wet season, while the carriage of IC/3D7 alleles decreased over this time period. It may be that decreases in transmission are related specifically to the IC/3D7 allelic family. The influence of transmission on MSP2 allele diversity needs to be clearly deciphered in studies which should include the use of sensitive methods for the detection of polymorphic parasite markers for both symptomatic and asymptomatic malaria. Such studies will enable better understanding of associations between allelic variants, MOI, transmission, malaria infection and disease.
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Affiliation(s)
- Akua Kyerewaa Botwe
- Ghana Health Service. Health Research Unit, Kintampo Health Research Centre. MOH/GHS, P.O.Box 200, College of Health Street, Kintampo, Brong Ahafo, Ghana. .,Department of Medicine, Solna, Karolinska Institutet, Stockholm, 17176, Sverige, Sweden.
| | - Kwaku Poku Asante
- Ghana Health Service. Health Research Unit, Kintampo Health Research Centre. MOH/GHS, P.O.Box 200, College of Health Street, Kintampo, Brong Ahafo, Ghana
| | - George Adjei
- Ghana Health Service. Health Research Unit, Kintampo Health Research Centre. MOH/GHS, P.O.Box 200, College of Health Street, Kintampo, Brong Ahafo, Ghana
| | - Samuel Assafuah
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - David Dosoo
- Ghana Health Service. Health Research Unit, Kintampo Health Research Centre. MOH/GHS, P.O.Box 200, College of Health Street, Kintampo, Brong Ahafo, Ghana
| | - Seth Owusu-Agyei
- Ghana Health Service. Health Research Unit, Kintampo Health Research Centre. MOH/GHS, P.O.Box 200, College of Health Street, Kintampo, Brong Ahafo, Ghana
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Mackinnon MJ, Read AF. GENETIC RELATIONSHIPS BETWEEN PARASITE VIRULENCE AND TRANSMISSION IN THE RODENT MALARIA PLASMODIUM CHABAUDI. Evolution 2017; 53:689-703. [PMID: 28565637 DOI: 10.1111/j.1558-5646.1999.tb05364.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/1998] [Accepted: 01/08/1999] [Indexed: 01/22/2023]
Abstract
Many parasites evolve to become virulent rather than benign mutualists. One of the major theoretical models of parasite virulence postulates that this is because rapid within-host replication rates are necessary for successful transmission (parasite fitness) and that virulence (damage to the host) is an unavoidable consequence of this rapid replication. Two fundamental assumptions underlying this so-called evolutionary trade-off model have rarely been tested empirically: (1) that higher replication rates lead to higher levels of virulence; and (2) that higher replication rates lead to higher transmission. Both of these relationships must have a genetic basis for this evolutionary hypothesis to be relevant. These assumptions were tested in the rodent malaria parasite, Plasmodium chabaudi, by examining genetic relationships between virulence and transmission traits across a population of eight parasite clones isolated from the wild. Each clone was injected into groups of inbred mice in a controlled laboratory environment, and replication rate (measured by maximum asexual parasitemia), virulence (measured by live-weight loss and degree of anemia in the mouse), and transmission (measured by density of sexual forms, gametocytes, in the blood and proportion of mosquitoes infected after taking a blood-meal from the mouse) were assessed. It was found that clones differed widely in these traits and these clone differences were repeatable over successive blood passages. Virulence traits were strongly phenotypically and genetically (i.e., across clones) correlated to maximum parasitemia thus supporting the first assumption that rapid replication causes higher virulence. Transmission traits were also positively phenotypically and genetically correlated to parasitemia, which supports the second assumption that rapid replication leads to higher transmission. Thus, two assumptions of the parasite-centered trade-off model of the evolution of virulence were shown to be justified in malaria parasites.
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Affiliation(s)
- Margaret J Mackinnon
- Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JT, United Kingdom
| | - Andrew F Read
- Institute of Cell, Animal and Population Biology, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JT, United Kingdom
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Dara A, Drábek EF, Travassos MA, Moser KA, Delcher AL, Su Q, Hostelley T, Coulibaly D, Daou M, Dembele A, Diarra I, Kone AK, Kouriba B, Laurens MB, Niangaly A, Traore K, Tolo Y, Fraser CM, Thera MA, Djimde AA, Doumbo OK, Plowe CV, Silva JC. New var reconstruction algorithm exposes high var sequence diversity in a single geographic location in Mali. Genome Med 2017; 9:30. [PMID: 28351419 PMCID: PMC5368897 DOI: 10.1186/s13073-017-0422-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 03/02/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Encoded by the var gene family, highly variable Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP1) proteins mediate tissue-specific cytoadherence of infected erythrocytes, resulting in immune evasion and severe malaria disease. Sequencing and assembling the 40-60 var gene complement for individual infections has been notoriously difficult, impeding molecular epidemiological studies and the assessment of particular var elements as subunit vaccine candidates. METHODS We developed and validated a novel algorithm, Exon-Targeted Hybrid Assembly (ETHA), to perform targeted assembly of var gene sequences, based on a combination of Pacific Biosciences and Illumina data. RESULTS Using ETHA, we characterized the repertoire of var genes in 12 samples from uncomplicated malaria infections in children from a single Malian village and showed them to be as genetically diverse as vars from isolates from around the globe. The gene var2csa, a member of the var family associated with placental malaria pathogenesis, was present in each genome, as were vars previously associated with severe malaria. CONCLUSION ETHA, a tool to discover novel var sequences from clinical samples, will aid the understanding of malaria pathogenesis and inform the design of malaria vaccines based on PfEMP1. ETHA is available at: https://sourceforge.net/projects/etha/ .
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Affiliation(s)
- Antoine Dara
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD USA
| | - Elliott F. Drábek
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
| | - Mark A. Travassos
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD USA
| | - Kara A. Moser
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
| | - Arthur L. Delcher
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
| | - Qi Su
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
| | - Timothy Hostelley
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
| | - Drissa Coulibaly
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Modibo Daou
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Ahmadou Dembele
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Issa Diarra
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Abdoulaye K. Kone
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Bourema Kouriba
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Matthew B. Laurens
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD USA
| | - Amadou Niangaly
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Karim Traore
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Youssouf Tolo
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Claire M. Fraser
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD USA
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD USA
| | - Mahamadou A. Thera
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Abdoulaye A. Djimde
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Ogobara K. Doumbo
- Malaria Research and Training Center, University of Science, Techniques and Technologies, Bamako, Mali
| | - Christopher V. Plowe
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD USA
| | - Joana C. Silva
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD USA
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19
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Newbold CI, Craig AG, Kyes S, Berendt AR, Snow RW, Peshu N, Marsh K. PfEMP1, polymorphism and pathogenesis. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2016. [DOI: 10.1080/00034983.1997.11813173] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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20
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Sobota RS, Dara A, Manning JE, Niangaly A, Bailey JA, Kone AK, Thera MA, Djimdé AA, Vernet G, Leissner P, Williams SM, Plowe CV, Doumbo OK. Expression of complement and toll-like receptor pathway genes is associated with malaria severity in Mali: a pilot case control study. Malar J 2016; 15:150. [PMID: 26961973 PMCID: PMC4784286 DOI: 10.1186/s12936-016-1189-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 02/23/2016] [Indexed: 11/11/2022] Open
Abstract
Background The host response to infection by Plasmodium falciparum, the parasite most often responsible for severe malaria, ranges from asymptomatic parasitaemia to death. The clinical trajectory of malaria is influenced by host genetics and parasite load, but the factors determining why some infections produce uncomplicated malaria and some proceed to severe disease remain incompletely understood. Methods To identify molecular markers of severe falciparum malaria, human gene expression patterns were compared between children aged 6 months to 5 years with severe and uncomplicated malaria who were enrolled in a case–control study in Bandiagara, Mali. Microarrays were used to obtain expression data on severe cases and uncomplicated controls at the time of acute disease presentation (five uncomplicated and five severe), 1 week after presentation (three uncomplicated and three severe) and treatment initiation, and in the subsequent dry season (late convalescence, four uncomplicated and four severe). This is a pilot study for the first use of microarray technology in Mali. Results Complement and toll-like receptor (TLR) pathways were differentially expressed, with severe cases showing higher expression of the C1q, TLR2, TLR4, TLR8, and CR1 genes. Other genes previously associated with malaria pathogenesis, GZMB, FOS and HSPA6, were also higher among severe cases. TLR2, TLR4, TLR8, CR1, GZMB, FOS, and HSPA6 genes were expressed at lower levels in severe cases at late convalescence. Conclusions Overexpression of genes previously associated with uncomplicated malaria was associated with severe disease. Low baseline expression of these genes may represent candidate markers for severe malaria. Despite the small sample size, results of this pilot study offer promising targets for follow-up analyses. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1189-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rafal S Sobota
- Department of Molecular Physiology and Biophysics, Vanderbilt Genetics Institute, Vanderbilt University, Nashville, TN, USA. .,Department of Genetics, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA.
| | - Antoine Dara
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali. .,Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Jessica E Manning
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
| | - Amadou Niangaly
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali.
| | - Jason A Bailey
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Abdoulaye K Kone
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali.
| | - Mahamadou A Thera
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali.
| | - Abdoulaye A Djimdé
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali.
| | - Guy Vernet
- Pasteur Institute of Cameroon, Yaounde, Cameroon, Fondation Merieux, Lyon, France.
| | | | - Scott M Williams
- Department of Genetics, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA.
| | - Christopher V Plowe
- Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Ogobara K Doumbo
- Department of Epidemiology of Parasitic Diseases, Malaria Research and Training Center, University of Sciences, Techniques and Technology of Bamako, Bamako, Mali.
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Differential Spleen Remodeling Associated with Different Levels of Parasite Virulence Controls Disease Outcome in Malaria Parasite Infections. mSphere 2015; 1:mSphere00018-15. [PMID: 27303680 PMCID: PMC4863626 DOI: 10.1128/msphere.00018-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 11/11/2015] [Indexed: 11/20/2022] Open
Abstract
Infections by malaria parasites can lead to very different clinical outcomes, ranging from mild symptoms to death. Differences in the ability of the spleen to deal with the infected red blood cells (iRBCs) are linked to differences in virulence. Using virulent and avirulent strains of the rodent malaria parasite Plasmodium yoelii, we investigated how parasite virulence modulates overall spleen function. Following parasite invasion, a difference in parasite virulence was observed in association with different levels of spleen morphology and iRBC rigidity, both of which contributed to enhanced parasite clearance. Moreover, iRBC rigidity as modulated by the spleen was demonstrated to correlate with disease outcome and thus can be used as a robust indicator of virulence. The data indicate that alterations in the biomechanical properties of iRBCs are the result of the complex interaction between host and parasite. Furthermore, we confirmed that early spleen responses are a key factor in directing the clinical outcome of an infection. IMPORTANCE The spleen and its response to parasite infection are important in eliminating parasites in malaria. By comparing P. yoelii parasite lines with different disease outcomes in mice that had either intact spleens or had had their spleens removed, we showed that upon parasite infection, the spleen exhibits dramatic changes that can affect parasite clearance. The spleen itself directly impacts RBC deformability independently of parasite genetics. The data indicated that the changes in the biomechanical properties of malaria parasite-infected RBCs are the result of the complex interaction between host and parasite, and RBC deformability itself can serve as a novel predictor of clinical outcome. The results also suggest that early responses in the spleen are a key factor directing the clinical outcome of an infection.
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Lymphocyte Perturbations in Malawian Children with Severe and Uncomplicated Malaria. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2015; 23:95-103. [PMID: 26581890 PMCID: PMC4744922 DOI: 10.1128/cvi.00564-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 11/13/2015] [Indexed: 11/29/2022]
Abstract
Lymphocytes are implicated in immunity and pathogenesis of severe malaria. Since lymphocyte subsets vary with age, assessment of their contribution to different etiologies can be difficult. We immunophenotyped peripheral blood from Malawian children presenting with cerebral malaria, severe malarial anemia, and uncomplicated malaria (n = 113) and healthy aparasitemic children (n = 42) in Blantyre, Malawi, and investigated lymphocyte subset counts, activation, and memory status. Children with cerebral malaria were older than those with severe malarial anemia. We found panlymphopenia in children presenting with cerebral malaria (median lymphocyte count, 2,100/μl) and uncomplicated malaria (3,700/μl), which was corrected in convalescence and was absent in severe malarial anemia (5,950/μl). Median percentages of activated CD69+ NK (73%) and γδ T (60%) cells were higher in cerebral malaria than in other malaria types. Median ratios of memory to naive CD4+ lymphocytes were higher in cerebral malaria than in uncomplicated malaria and low in severe malarial anemia. The polarized lymphocyte subset profiles of different forms of severe malaria are independent of age. In conclusion, among Malawian children cerebral malaria is characterized by lymphocyte activation and increased memory cells, consistent with immune priming. In contrast, there are reduced memory cells and less activation in severe malaria anemia. Further studies are required to understand whether these immunological profiles indicate predisposition of some children to one or another form of severe malaria.
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Clinical Variation of Plasmodium falciparum eba-175, ama-1, and msp-3 Genotypes in Young Children Living in a Seasonally High Malaria Transmission Setting in Burkina Faso. J Parasitol Res 2015; 2015:985651. [PMID: 26634149 PMCID: PMC4655070 DOI: 10.1155/2015/985651] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 10/08/2015] [Accepted: 10/15/2015] [Indexed: 11/17/2022] Open
Abstract
The association between P. falciparum eba-175, ama-1, and msp-3 polymorphism in the pathogenicity of malaria disease was investigated. We therefore compared the prevalence of different alleles between symptomatic and asymptomatic malarial children under five years of age living in Burkina Faso. Blood filter papers were collected during the 2008 malaria transmission season from 228 symptomatic and 199 asymptomatic children under five years of age. All patients were living in the rural area of Saponé at about 50 km from Ouagadougou, the capital city of Burkina Faso. P. falciparum parasite DNA was extracted using QIAGEN kits and the alleles diversity was assessed by a nested PCR. PCR products were then digested by restriction enzymes based on already described polymorphic regions of the eba-175, ama-1, and msp-3 genes. The individual alleles eba-175_FCR3 and msp-3_K1 frequencies were statistically higher (p < 0.0001) in the asymptomatic group compared to the symptomatic ones. No statistically significant difference was noted in the prevalence of ama-1-3D7, ama-1-K1, and ama-1-HB3 genotypes between the two groups (p > 0.05). The comparative analysis of P. falciparum genotypes indicated that the polymorphism in eba-175 and msp-3 genotypes varied between asymptomatic and symptomatic clinical groups and may contribute to the pathogenesis of malaria.
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Pemberton-Ross P, Smith TA, Hodel EM, Kay K, Penny MA. Age-shifting in malaria incidence as a result of induced immunological deficit: a simulation study. Malar J 2015; 14:287. [PMID: 26206255 PMCID: PMC4513612 DOI: 10.1186/s12936-015-0805-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 07/10/2015] [Indexed: 11/10/2022] Open
Abstract
Effective population-level interventions against Plasmodium falciparum malaria lead to age-shifts, delayed morbidity or rebounds in morbidity and mortality whenever they are deployed in ways that do not permanently interrupt transmission. When long-term intervention programmes target specific age-groups of human hosts, the age-specific morbidity rates ultimately adjust to new steady-states, but it is very difficult to study these rates and the temporal dynamics leading up to them empirically because the changes occur over very long time periods. This study investigates the age and magnitude of age- and time- shifting of incidence induced by either pre-erythrocytic vaccination (PEV) programmes or seasonal malaria chemo-prevention (SMC), using an ensemble of individual-based stochastic simulation models of P. falciparum dynamics. The models made various assumptions about immunity decay, transmission heterogeneity and were parameterized with data on both age-specific infection and disease incidence at different levels of exposure, on the durations of different stages of the parasite life-cycle and on human demography. Effects of transmission intensity, and of levels of access to malaria treatment were considered. While both PEV and SMC programmes are predicted to have overall strongly positive health effects, a shift of morbidity into older children is predicted to be induced by either programme if transmission levels remain static and not reduced by other interventions. Predicted shifting of burden continue into the second decade of the programme. Even if long-term surveillance is maintained it will be difficult to avoid mis-attribution of such long-term changes in age-specific morbidity patterns to other factors. Conversely, short-lived transient changes in incidence measured soon after introduction of a new intervention may give over-positive views of future impacts. Complementary intervention strategies could be designed to specifically protect those age-groups at risk from burden shift.
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Affiliation(s)
- Peter Pemberton-Ross
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
| | - Eva Maria Hodel
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
| | - Katherine Kay
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
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Preserved dendritic cell HLA-DR expression and reduced regulatory T cell activation in asymptomatic Plasmodium falciparum and P. vivax infection. Infect Immun 2015; 83:3224-32. [PMID: 26034211 DOI: 10.1128/iai.00226-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 05/24/2015] [Indexed: 02/04/2023] Open
Abstract
Clinical illness with Plasmodium falciparum or Plasmodium vivax compromises the function of dendritic cells (DC) and expands regulatory T (Treg) cells. Individuals with asymptomatic parasitemia have clinical immunity, restricting parasite expansion and preventing clinical disease. The role of DC and Treg cells during asymptomatic Plasmodium infection is unclear. During a cross-sectional household survey in Papua, Indonesia, we examined the number and activation of blood plasmacytoid DC (pDC), CD141(+), and CD1c(+) myeloid DC (mDC) subsets and Treg cells using flow cytometry in 168 afebrile children (of whom 15 had P. falciparum and 36 had P. vivax infections) and 162 afebrile adults (of whom 20 had P. falciparum and 20 had P. vivax infections), alongside samples from 16 patients hospitalized with uncomplicated malaria. Unlike DC from malaria patients, DC from children and adults with asymptomatic, microscopy-positive P. vivax or P. falciparum infection increased or retained HLA-DR expression. Treg cells in asymptomatic adults and children exhibited reduced activation, suggesting increased immune responsiveness. The pDC and mDC subsets varied according to clinical immunity (asymptomatic or symptomatic Plasmodium infection) and, in asymptomatic infection, according to host age and parasite species. In conclusion, active control of asymptomatic infection was associated with and likely contingent upon functional DC and reduced Treg cell activation.
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Griffin JT, Hollingsworth TD, Reyburn H, Drakeley CJ, Riley EM, Ghani AC. Gradual acquisition of immunity to severe malaria with increasing exposure. Proc Biol Sci 2015; 282:20142657. [PMID: 25567652 PMCID: PMC4309004 DOI: 10.1098/rspb.2014.2657] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 12/04/2014] [Indexed: 11/12/2022] Open
Abstract
Previous analyses have suggested that immunity to non-cerebral severe malaria due to Plasmodium falciparum is acquired after only a few infections, whereas longitudinal studies show that some children experience multiple episodes of severe disease, suggesting that immunity may not be acquired so quickly. We fitted a mathematical model for the acquisition and loss of immunity to severe disease to the age distribution of severe malaria cases stratified by symptoms from a range of transmission settings in Tanzania, combined with data from several African countries on the age distribution and overall incidence of severe malaria. We found that immunity to severe disease was acquired more gradually with exposure than previously thought. The model also suggests that physiological changes, rather than exposure, may alter the symptoms of disease with increasing age, suggesting that a later age at infection would be associated with a higher proportion of cases presenting with cerebral malaria regardless of exposure. This has consequences for the expected pattern of severe disease as transmission changes. Careful monitoring of the decline in immunity associated with reduced transmission will therefore be needed to ensure rebound epidemics of severe and fatal malaria are avoided.
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Affiliation(s)
- Jamie T Griffin
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London W2 1PG, UK
| | - T Déirdre Hollingsworth
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK Department of Clinical Sciences, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Hugh Reyburn
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Chris J Drakeley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Eleanor M Riley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Azra C Ghani
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, London W2 1PG, UK
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Nannyonga B, Mwanga GG, Haario H, Mbalawata IS, Heilio M. Determining parameter distribution in within-host severe P. falciparum malaria. Biosystems 2014; 126:76-84. [PMID: 25258181 DOI: 10.1016/j.biosystems.2014.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/25/2014] [Accepted: 09/18/2014] [Indexed: 10/24/2022]
Abstract
Numerous studies have been carried out on within-host Plasmodium falciparum malaria with varying results. Some studies have suggested over estimation of parasite growth within an infected host while others stated that evolution of parasitaemia seems to be quelled by parasite load. Various mathematical models have been designed to understand the dynamics of evolution of within-host malaria. The basic ingredient in most of the models is that the availability of uninfected red blood cells (RBCs) in which the parasite develops is a limiting factor in the propagation of the parasite population. We hypothesize that in severe malaria, due to parasite quest for survival and rapid multiplication, the vicious malaria parasite is sophisticated and can be absorbed in an already infected RBC and speeds up rapture rate. The study reviews the classical models of blood stage malaria and proposes a new model which incorporates double infection. Analysis of the model and parameter identifiability using Markov chain Monte Carlo (MCMC) are presented. MCMC uses distribution of parameters to study the model behavior instead of single points. Results indicate that most infected RBCs rupture quickly due to the disease instead. This may explain anemia in malaria patients and lack of uniformity of oscillations in within-host malaria. Therefore, more needs to be done as far as within-host malaria is concerned, to provide step by step evolution of malaria within a host.
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Affiliation(s)
- B Nannyonga
- Department of Mathematics, Makerere University, P.O. Box 7062, Kampala, Uganda.
| | - G G Mwanga
- Department of Mathematics and Physics, Lappeenranta University of Technology, Box 20, FIN-53851 Lappeenranta, Finland
| | - H Haario
- Department of Mathematics and Physics, Lappeenranta University of Technology, Box 20, FIN-53851 Lappeenranta, Finland
| | - I S Mbalawata
- Department of Mathematics and Physics, Lappeenranta University of Technology, Box 20, FIN-53851 Lappeenranta, Finland
| | - M Heilio
- Department of Mathematics and Physics, Lappeenranta University of Technology, Box 20, FIN-53851 Lappeenranta, Finland
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Kabyemela E, Gonçalves BP, Prevots DR, Morrison R, Harrington W, Gwamaka M, Kurtis JD, Fried M, Duffy PE. Cytokine profiles at birth predict malaria severity during infancy. PLoS One 2013; 8:e77214. [PMID: 24130857 PMCID: PMC3795067 DOI: 10.1371/journal.pone.0077214] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 09/08/2013] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Severe malaria risk varies between individuals, and most of this variation remains unexplained. Here, we examined the hypothesis that cytokine profiles at birth reflect inter-individual differences that persist and influence malaria parasite density and disease severity throughout early childhood. METHODS AND FINDINGS Cytokine levels (TNF-α, IFN-γ, IL-1β, IL-4, IL-5, IL-6 and IL-10) were measured at birth (cord blood; N=783) and during subsequent routine follow-up visits (peripheral blood) for children enrolled between 2002 and 2006 into a birth cohort in Muheza, Tanzania. Children underwent blood smear and clinical assessments every 2-4 weeks, and at the time of any illness. Cord blood levels of all cytokines were positively correlated with each other (Spearman's rank correlation). Cord levels of IL-1β and TNF-α (but not other cytokines) correlated with levels of the same cytokine measured at routine visits during early life (P < 0.05). Higher cord levels of IL-1β but not TNF-α were associated with lower parasite densities during infancy (P=0.003; Generalized Estimating Equation (GEE) method), with an average ~40% reduction versus children with low cord IL-1β levels, and with decreased risk of severe malaria during follow-up (Cox regression): adjusted hazard ratio (95% CI) 0.60 (0.39-0.92), P = 0.02. CONCLUSION IL-1β levels at birth are related to future IL-1β levels as well as the risk of severe malaria in early life. The effect on severe malaria risk may be due in part to the effect of inflammatory cytokines to control parasite density.
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Affiliation(s)
- Edward Kabyemela
- MOMS Project, Seattle Biomedical Research Institute, Seattle, Washington, United States of America, and Muheza Designated District Hospital, Muheza, Tanzania
| | - Bronner P. Gonçalves
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, United States of America
- Laboratory of Clinical Infectious Diseases – Epidemiology Unit, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, United States of America
| | - D. Rebecca Prevots
- Laboratory of Clinical Infectious Diseases – Epidemiology Unit, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, United States of America
| | - Robert Morrison
- MOMS Project, Seattle Biomedical Research Institute, Seattle, Washington, United States of America, and Muheza Designated District Hospital, Muheza, Tanzania
| | - Whitney Harrington
- Seattle Children's Hospital and Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Moses Gwamaka
- MOMS Project, Seattle Biomedical Research Institute, Seattle, Washington, United States of America, and Muheza Designated District Hospital, Muheza, Tanzania
| | - Jonathan D. Kurtis
- Center for International Health Research, Rhode Island Hospital, Providence, Rhode Island, United States of America
- Department of Pathology and Laboratory Medicine, Brown University Medical School, Providence, Rhode Island, United States of America
| | - Michal Fried
- MOMS Project, Seattle Biomedical Research Institute, Seattle, Washington, United States of America, and Muheza Designated District Hospital, Muheza, Tanzania
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, United States of America
| | - Patrick E. Duffy
- MOMS Project, Seattle Biomedical Research Institute, Seattle, Washington, United States of America, and Muheza Designated District Hospital, Muheza, Tanzania
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, United States of America
- * E-mail:
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Nyctanthes arbor-tristis positively affects immunopathology of malaria-infected mice prolonging its survival. Parasitol Res 2013; 112:2601-9. [DOI: 10.1007/s00436-013-3427-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 04/04/2013] [Indexed: 10/26/2022]
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Hansen E, Buckee CO. Modeling the human infectious reservoir for malaria control: does heterogeneity matter? Trends Parasitol 2013; 29:270-5. [PMID: 23597499 DOI: 10.1016/j.pt.2013.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Revised: 02/22/2013] [Accepted: 03/18/2013] [Indexed: 12/19/2022]
Abstract
The complex biological relationships underlying malaria transmission make it difficult to predict the impact of interventions. Mathematical models simplify these relationships and capture essential components of malaria transmission and epidemiology. Models designed to predict the impact of control programs generally infer a relationship between transmission intensity and human infectiousness to the mosquito, requiring assumptions about how infectiousness varies between individuals. A lack of understanding of human infectiousness precludes a standard approach to this inference, however, and field data reveal no obvious correlation between transmission intensity and human population infectiousness. We argue that model assumptions will have important consequences for predicting the impact of control programs.
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Affiliation(s)
- Elsa Hansen
- Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA, USA
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Gouissi FM, Salifou S, Edorh AP, Sedjame AR, Gouissi SA, Yadouleton WA, Akogbeto M, Boko M. Contribution of poses screen preimpregnated (PSP) installed at openings and eaves of dwellings in the reduction of malaria transmission in the commune of aguégués in bénin. ASIAN PAC J TROP MED 2013; 6:61-7. [DOI: 10.1016/s1995-7645(12)60202-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 03/15/2012] [Accepted: 05/15/2012] [Indexed: 11/17/2022] Open
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Possible association of the Plasmodium falciparum T1526C resa2 gene mutation with severe malaria. Malar J 2012; 11:128. [PMID: 22533816 PMCID: PMC3422168 DOI: 10.1186/1475-2875-11-128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 04/25/2012] [Indexed: 11/10/2022] Open
Abstract
Background Plasmodium falciparum exports proteins that remodel the erythrocyte membrane. One such protein, called Pf155/RESA (RESA1) contributes to parasite fitness, optimizing parasite survival during febrile episodes. Resa1 gene is a member of a small family comprising three highly related genes. Preliminary evidence led to a search for clues indicating the involvement of RESA2 protein in the pathophysiology of malaria. In the present study, cDNA sequence of resa2 gene was obtained from two different strains. The proportion of P. falciparum isolates having a non-stop T1526C mutation in resa2 gene was evaluated and the association of this genotype with severity of malaria was investigated. Methods Resa2 cDNAs of two different strains (a patient isolate and K1 culture adapted strain) was obtained by RT-PCR and DNA sequencing was performed to confirm its gene structure. The proportion of isolates having a T1526C mutation was evaluated using a PCR-RFLP methodology on groups of severe malaria and uncomplicated patients recruited in 1991–1994 in Senegal and in 2009 in Benin. Results A unique ORF with an internal translation stop was found in the patient isolate (Genbank access number : JN183870), while the K1 strain harboured the T1526C mutation (Genbank access number : JN183869) which affects the internal stop codon and restores a full length coding sequence. About 14% of isolates obtained from Senegal and Benin harboured mutant T1526C parasites. Some isolates had both wild and mutant resa alleles. The analysis excluding those mixed isolates showed that the resa2 T1526C mutation was found more frequently in severe malaria cases than in uncomplicated cases (p = 0.008). The association of the presence of the mutant allele and parasitaemia >4% was shown in multivariate analysis (p = 0.03) in the group of Beninese children. Conclusions All T1526C mutant parasites theoretically have the ability to give rise to a full-length RESA2 protein. This study raises the hypothesis that the RESA2 protein could favour high-density infections. Other studies in various geographic settings and probably including more patients are now required to replicate these results and to answer the questions raised by these results.
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Hussain MM, Sohail M, Kumar R, Branch OH, Adak T, Raziuddin M. Genetic diversity in merozoite surface protein-1 and 2 among Plasmodium falciparum isolates from malarious districts of tribal dominant state of Jharkhand, India. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2012; 105:579-92. [PMID: 22325817 DOI: 10.1179/2047773211y.0000000012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
INTRODUCTION The genetic make-up of malaria parasite is potent for understanding the parasite virulence, designing antimalarial vaccine and evaluating the impact of malaria control measures. There is a paucity of information on genetic structure of Plasmodium falciparum in Jharkhand, India where malaria is rampant and this study aimed to establish molecular characterization of P. falciparum field isolates from Jharkhand measured with two highly polymorphic genetic markers, i.e. the merozoite surface proteins (MSPs) 1 and 2. METHODS The genetic diversity of P. falciparum population from low transmission area, Ranchi, Bokaro and Hazaribagh and highly malarious area, Latehar and Palamau districts of Jharkhand were evaluated by polymerase chain reaction-sequencing analyzing msp-1 and msp-2 genes to explore the genetic structure of parasite from this understudied region. RESULTS A total of 134 P. falciparum isolates were analyzed by polymorphic regions of msp-1 and msp-2 and classified according to prevalence of allelic families. The majority of patients from all the five sites had mean monoclonal infections of 67·1 and 60·4% of P. falciparum for msp-1 and msp-2, respectively, whereas, mean multiple genotypes of 32·8 and 39·5% for msp-1 and msp-2, respectively. Interestingly, we observed higher multiclonal infection in low transmission area as compared to highly malarious area in the case of msp-1 genotypes, whereas in msp-2 higher multiclonal infection was observed in highly malarious area compared to low transmission area. The overall multiplicities of infection of msp-1 and msp-2 were 1·38 and 1·39, respectively. CONCLUSION This is the first report on molecular characterization of P. falciparum field isolates from Jharkhand. The genetic diversity and allelic distribution found in this study is somewhat similar to other reports from India and Southeast Asian countries. However, P. falciparum infection can be highly complex and diverse in these disease-endemic regions of Jharkhand, suggesting continual genetic mixing that could have significant implications for the use of antimalarial drugs and vaccines.
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Affiliation(s)
- M M Hussain
- Vinoba Bhave University, Hazaribag, Jharkhand, India
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Buckee CO, Recker M. Evolution of the multi-domain structures of virulence genes in the human malaria parasite, Plasmodium falciparum. PLoS Comput Biol 2012; 8:e1002451. [PMID: 22511852 PMCID: PMC3325180 DOI: 10.1371/journal.pcbi.1002451] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 02/10/2012] [Indexed: 11/30/2022] Open
Abstract
The var gene family of Plasmodium falciparum encodes the immunodominant variant surface antigens PfEMP1. These highly polymorphic proteins are important virulence factors that mediate cytoadhesion to a variety of host tissues, causing sequestration of parasitized red blood cells in vital organs, including the brain or placenta. Acquisition of variant-specific antibodies correlates with protection against severe malarial infections; however, understanding the relationship between gene expression and infection outcome is complicated by the modular genetic architectures of var genes that encode varying numbers of antigenic domains with differential binding specificities. By analyzing the domain architectures of fully sequenced var gene repertoires we reveal a significant, non-random association between the number of domains comprising a var gene and their sequence conservation. As such, var genes can be grouped into those that are short and diverse and genes that are long and conserved, suggesting gene length as an important characteristic in the classification of var genes. We then use an evolutionary framework to demonstrate how the same evolutionary forces acting on the level of an individual gene may have also shaped the parasite's gene repertoire. The observed associations between sequence conservation, gene architecture and repertoire structure can thus be explained by a trade-off between optimizing within-host fitness and minimizing between-host immune selection pressure. Our results demonstrate how simple evolutionary mechanisms can explain var gene structuring on multiple levels and have important implications for understanding the multifaceted epidemiology of P. falciparum malaria. Plasmodium falciparum, the most severe of the human malarias, contains within its genome a family of ∼60 var genes which play an important role in disease pathology and maintenance of chronic infections. Var genes have a modular genetic architecture and encode varying numbers of binding domains with specific preferences to a range of host tissues. Given the availability of host receptors for binding and the immunogenic properties of each domain it is not clear why genes encode multiple domains at once and how these are structured within each parasite's antigenic repertoire. Here we investigate the domain architecture of these important virulence genes and highlight an evolutionary trade-off between maintaining within-host fitness and optimizing between-host transmission success as an important driver in structuring var genes and var gene repertoires alike.
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Affiliation(s)
- Caroline O. Buckee
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Mario Recker
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Roca-Feltrer A, Carneiro I, Smith L, Schellenberg JRA, Greenwood B, Schellenberg D. The age patterns of severe malaria syndromes in sub-Saharan Africa across a range of transmission intensities and seasonality settings. Malar J 2010; 9:282. [PMID: 20939931 PMCID: PMC2992028 DOI: 10.1186/1475-2875-9-282] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Accepted: 10/13/2010] [Indexed: 11/25/2022] Open
Abstract
Background A greater understanding of the relationship between transmission intensity, seasonality and the age-pattern of malaria is needed to guide appropriate targeting of malaria interventions in different epidemiological settings. Methods A systematic literature review identified studies which reported the age of paediatric hospital admissions with cerebral malaria (CM), severe malarial anaemia (SMA), or respiratory distress (RD). Study sites were categorized into a 3 × 2 matrix of Plasmodium falciparum transmission intensity and seasonality. Probability distributions were fitted by maximum likelihood methods, and best fitting models were used to estimate median ages and to represent graphically the age-pattern of each outcome for each transmission category in the matrix. Results A shift in the burden of CM towards younger age groups was seen with increasing intensity of transmission, but this was not the case for SMA or RD. Sites with 'no marked seasonality' showed more evidence of skewed age-patterns compared to areas of 'marked seasonality' for all three severe malaria syndromes. Conclusions Although the peak age of CM will increase as transmission intensity decreases in Africa, more than 75% of all paediatric hospital admissions of severe malaria are likely to remain in under five year olds in most epidemiological settings.
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Affiliation(s)
- Arantxa Roca-Feltrer
- Department of Disease Control, Faculty of Infectious & Tropical Disease, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK.
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Forcing versus feedback: epidemic malaria and monsoon rains in northwest India. PLoS Comput Biol 2010; 6:e1000898. [PMID: 20824122 PMCID: PMC2932675 DOI: 10.1371/journal.pcbi.1000898] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Accepted: 07/21/2010] [Indexed: 11/19/2022] Open
Abstract
Malaria epidemics in regions with seasonal windows of transmission can vary greatly in size from year to year. A central question has been whether these interannual cycles are driven by climate, are instead generated by the intrinsic dynamics of the disease, or result from the resonance of these two mechanisms. This corresponds to the more general inverse problem of identifying the respective roles of external forcings vs. internal feedbacks from time series for nonlinear and noisy systems. We propose here a quantitative approach to formally compare rival hypotheses on climate vs. disease dynamics, or external forcings vs. internal feedbacks, that combines dynamical models with recently developed, computational inference methods. The interannual patterns of epidemic malaria are investigated here for desert regions of northwest India, with extensive epidemiological records for Plasmodium falciparum malaria for the past two decades. We formulate a dynamical model of malaria transmission that explicitly incorporates rainfall, and we rely on recent advances on parameter estimation for nonlinear and stochastic dynamical systems based on sequential Monte Carlo methods. Results show a significant effect of rainfall in the inter-annual variability of epidemic malaria that involves a threshold in the disease response. The model exhibits high prediction skill for yearly cases in the malaria transmission season following the monsoonal rains. Consideration of a more complex model with clinical immunity demonstrates the robustness of the findings and suggests a role of infected individuals that lack clinical symptoms as a reservoir for transmission. Our results indicate that the nonlinear dynamics of the disease itself play a role at the seasonal, but not the interannual, time scales. They illustrate the feasibility of forecasting malaria epidemics in desert and semi-arid regions of India based on climate variability. This approach should be applicable to malaria in other locations, to other infectious diseases, and to other nonlinear systems under forcing. Malaria epidemics can exhibit pronounced variation from year to year that can be driven by external forcings, such as climate, or can be generated instead by dynamic feedbacks within the disease system itself. For example, levels of immunity in the population (or control efforts) can rise and fall as the result of past levels of infection. This type of feedback is found in the dynamics of all (nonlinear) biological systems. Feedbacks can interact in complex ways with external drivers, for example by creating refractory periods. It remains a challenge to identify internal feedbacks vs. external forcings from available temporal records of aggregated reported cases and forcing variables. We propose a quantitative approach that can statistically compare the hypotheses of feedbacks vs. forcings (epidemiological vs. climate) based on dynamical and mechanistic models. Our approach is computational, based on a large number of computer simulations of the different models. We illustrate and apply the approach to the analysis of extensive monthly records for malaria incidence in desert regions of India that span two decades. Our analyses confirm the strong role of rainfall, and quantify this effect with transmission model(s) for malaria that include rainfall and are shown to exhibit a remarkable prediction skill.
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Modelling malaria population structure and its implications for control. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 673:112-26. [PMID: 20632533 DOI: 10.1007/978-1-4419-6064-1_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Mathematical models of malaria transmission have been used to inform the design of malaria control programs since the mid 20th century, and many of these models have provided useful insights into the complexity of the disease. Among developing countries, however and particularly in sub-Saharan Africa, malaria remains a major cause of morbidity and mortality. One of the main difficulties in controlling the most virulent human malaria parasite, Plasmodium falciparum, is its genetic diversity, which confounds attempts to design an effective vaccine. The population structure of P. falciparum remains poorly understood but plays a key role in determining epidemiological patterns of disease and the development of immunity. We discuss the seminal model of malaria transmission developed by Ross and MacDonald, and the modifications that have been made since to include more realism. We show that age profiles of disease and serological data support a theoretical model in which the parasite population is diverse and structured into several antigenic types and highlight the implications of this structure for controlling malaria. Lastly, we discuss the current sequence data on parasite antigen genes that are important for the aquisition of immunity, and the results of a new analysis of P. falciparum population structure at the genomic level.
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Schilter HC, Pereira ATM, Eschenazi PD, Fernandes A, Shim D, Sousa ALS, Teixeira MM, Negrão-Corrêa D. Regulation of immune responses to Strongyloides venezuelensis challenge after primary infection with different larvae doses. Parasite Immunol 2010; 32:184-92. [PMID: 20398181 DOI: 10.1111/j.1365-3024.2009.01176.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Nematode infections are generally followed by high rates of reinfection, leading to elevated prevalence in endemic areas. Therefore, the effective control of nematode infections depends on understanding the induction and regulation of protective mechanisms. However, most experimental models for protective immune response against nematodes use high parasite exposure, not always reflecting what occurs naturally in human populations. In this study, we tested whether infecting mice with different Strongyloides venezuelensis larvae loads would affect protective responses against reinfection. Interestingly, we found that a previous infection with 10-500 larvae conferred high rate of protection against reinfection with S. venezuelensis in mice, by destroying large numbers of migrating larvae. However, low-dose priming did not abolish adult worm maturation, as detected in high-dose primed group. Results also indicated that a previous low-dose infection delayed the development of cellular infiltrate, while a high inoculum rapidly induced these inflammatory features. Cytokine production by splenocyte cultures of challenge infected mice demonstrated that low-dose priming had increased production of IL-4 and IFN-gamma, while high-dose induced IL-4 production but not IFN-gamma. Our data support the hypothesis that low-dose nematode infection does not induce a polarized type-2 immune response, allowing adult worm survival.
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Affiliation(s)
- H C Schilter
- Department of Parasitology, Biological Science Institute of the Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
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Romi R, Boccolini D, D'Amato S, Cenci C, Peragallo M, D'Ancona F, Pompa MG, Majori G. Incidence of malaria and risk factors in Italian travelers to malaria endemic countries. Travel Med Infect Dis 2010; 8:144-54. [DOI: 10.1016/j.tmaid.2010.02.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 02/01/2010] [Accepted: 02/04/2010] [Indexed: 11/30/2022]
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Bob NS, Diop BM, Renaud F, Marrama L, Durand P, Tall A, Ka B, Ekala MT, Bouchier C, Mercereau-Puijalon O, Jambou R. Parasite polymorphism and severe malaria in Dakar (Senegal): a West African urban area. PLoS One 2010; 5:e9817. [PMID: 20352101 PMCID: PMC2843705 DOI: 10.1371/journal.pone.0009817] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 02/01/2010] [Indexed: 11/25/2022] Open
Abstract
Background Transmission of malaria in West African urban areas is low and healthcare facilities are well organized. However, malaria mortality remains high. We conducted a survey in Dakar with the general objective to establish who died from severe malaria (SM) in urban areas (particularly looking at the age-groups) and to compare parasite isolates associated with mild or severe malaria. Methodology/Principal Findings The current study included mild- (MM) and severe malaria (SM) cases, treated in dispensaries (n = 2977) and hospitals (n = 104), We analysed Pfdhfr/Pfcrt-exon2 and nine microsatellite loci in 102 matched cases of SM and MM. Half of the malaria cases recorded at the dispensaries and 87% of SM cases referred to hospitals, occurred in adults, although adults only accounted for 26% of all dispensary consultations. This suggests that, in urban settings, whatever the reason for this adult over-representation, health-workers are forced to take care of increasing numbers of malaria cases among adults. Inappropriate self treatment and mutations in genes associated with drug resistance were found associated with SM in adults. SM was also associated with a specific pool of isolates highly polymorphic and different from those associated with MM. Conclusion In this urban setting, adults currently represent one of the major groups of patients attending dispensaries for malaria treatment. For these patients, despite the low level of transmission, SM was associated with a specific and highly polymorphic pool of parasites which may have been selected by inappropriate treatment.
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Affiliation(s)
| | | | | | | | | | - Adama Tall
- Institut Pasteur de Dakar, Dakar, Senegal
| | | | - Marie Therese Ekala
- Institut Pasteur, Immunologie Moléculaire des Parasites, CNRS URA 2581, Paris, France
| | | | | | - Ronan Jambou
- Institut Pasteur de Dakar, Dakar, Senegal
- * E-mail:
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Abstract
Malaria is a major public health problem. An effective vaccine against malaria is actively being sought. We formulate a potential outcomes definition of the efficacy of a malaria vaccine for preventing fever. A challenge in estimating this efficacy is that there is no sure way to determine whether a fever was caused by malaria. We study the properties of two approaches for estimating efficacy: (1) use a deterministic case definition of a malaria caused fever as the conjunction of fever and parasite density above a certain cutoff; (2) use a probabilistic case definition in which the probability that each fever was caused by malaria is estimated. We compare these approaches in a simulation study and find that both approaches can potentially have large biases. We suggest a strategy for choosing an estimator based on the investigator's prior knowledge about the area in which the trial is being conducted and the range of vaccine efficacies over which the investigator would like the estimator to have good properties.
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Plasmodium falciparum var gene expression is modified by host immunity. Proc Natl Acad Sci U S A 2009; 106:21801-6. [PMID: 20018734 DOI: 10.1073/pnas.0907590106] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a potentially important family of immune targets, which play a central role in the host-parasite interaction by binding to various host molecules. They are encoded by a diverse family of genes called var, of which there are approximately 60 copies in each parasite genome. In sub-Saharan Africa, although P. falciparum infection occurs throughout life, severe malarial disease tends to occur only in childhood. This could potentially be explained if (i) PfEMP1 variants differ in their capacity to support pathogenesis of severe malaria and (ii) this capacity is linked to the likelihood of each molecule being recognized and cleared by naturally acquired antibodies. Here, in a study of 217 Kenyan children with malaria, we show that expression of a group of var genes "cys2," containing a distinct pattern of cysteine residues, is associated with low host immunity. Expression of cys2 genes was associated with parasites from young children, those with severe malaria, and those with a poorly developed antibody response to parasite-infected erythrocyte surface antigens. Cys-2 var genes form a minor component of all genomic var repertoires analyzed to date. Therefore, the results are compatible with the hypothesis that the genomic var gene repertoire is organized such that PfEMP1 molecules that confer the most virulence to the parasite tend also to be those that are most susceptible to the development of host immunity. This may help the parasite to adapt effectively to the development of host antibodies through modification of the host-parasite relationship.
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Soulama I, Nébié I, Ouédraogo A, Gansane A, Diarra A, Tiono AB, Bougouma EC, Konaté AT, Kabré GB, Taylor WRJ, Sirima SB. Plasmodium falciparum genotypes diversity in symptomatic malaria of children living in an urban and a rural setting in Burkina Faso. Malar J 2009; 8:135. [PMID: 19545390 PMCID: PMC2705376 DOI: 10.1186/1475-2875-8-135] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2009] [Accepted: 06/20/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The clinical presentation of malaria, considered as the result of a complex interaction between parasite and human genetics, is described to be different between rural and urban areas. The analysis of the Plasmodium falciparum genetic diversity in children with uncomplicated malaria, living in these two different areas, may help to understand the effect of urbanization on the distribution of P. falciparum genotypes. METHODS Isolates collected from 75 and 89 children with uncomplicated malaria infection living in a rural and an urban area of Burkina Faso, respectively, were analysed by a nested PCR amplification of msp1 and msp2 genes to compare P. falciparum diversity. RESULTS The K1 allelic family was widespread in children living in the two sites, compared to other msp1 allelic families (frequency >90%). The MAD 20 allelic family of msp1 was more prevalent (p = 0.0001) in the urban (85.3%) than the rural area (63.2%). In the urban area, the 3D7 alleles of msp2 were more prevalent compared to FC27 alleles, with a high frequency for the 3D7 300bp allele (>30%). The multiplicity of infection was in the range of one to six in the urban area and of one to seven in the rural area. There was no difference in the frequency of multiple infections (p = 0.6): 96.0% (95% C.I: 91.6-100) in urban versus 93.1% (95%C.I: 87.6-98.6) in rural areas. The complexity of infection increased with age [p = 0.04 (rural area), p = 0.06 (urban area)]. CONCLUSION Urban-rural area differences were observed in some allelic families (MAD20, FC27, 3D7), suggesting a probable impact of urbanization on genetic variability of P. falciparum. This should be taken into account in the implementation of malaria control measures.
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Affiliation(s)
- Issiaka Soulama
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Issa Nébié
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Alphonse Ouédraogo
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Adama Gansane
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Amidou Diarra
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Edith C Bougouma
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Amadou T Konaté
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
| | - Gustave B Kabré
- Université de Ouagadougou, Unité de Formation et de Recherche Science de la Vie et de la Terre, Ouagadougou, Burkina Faso
| | - Walter RJ Taylor
- Travel and Migration Medicine Unit, Geneva University Hospital, Geneva, Switzerland
- Oxford University Clinical Research Unit, Hanoi, Vietnam
| | - Sodiomon B Sirima
- Centre National de Recherche et de Formation sur le Paludisme. 01 BP 2208 Ouagadougou 01, Burkina Faso
- Groupe de Recherche et d'Action en Santé, Ouagadougou, Burkina Faso
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Dobson A. Climate variability, global change, immunity, and the dynamics of infectious diseases. Ecology 2009; 90:920-7. [DOI: 10.1890/08-0736.1] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Jambou R, El-Assaad F, Combes V, Grau GE. Citicoline (CDP-choline): What role in the treatment of complications of infectious diseases. Int J Biochem Cell Biol 2009; 41:1467-70. [PMID: 19401146 DOI: 10.1016/j.biocel.2009.02.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Revised: 02/13/2009] [Accepted: 02/13/2009] [Indexed: 10/21/2022]
Abstract
A dysregulated host immune response, as opposed to the intrinsic virulence of a microbial pathogen induces a large part of the pathology seen in infectious diseases. However, current therapies are designed to target the pathogen rather than the underlying pathogenic mechanisms responsible for the manifestation of the pathology. Recent studies have highlighted the role of endothelial cell alteration in the pathology induced in sepsis and cerebral malaria. The endothelial onslaught described, is similar to that seen during ischemia reperfusion in stroke. Protecting endothelial cell membranes during sepsis and cerebral malaria, using citicoline in the same way as in stroke, has thus emerged as a new strategy that needs to be evaluated urgently. Citicoline is a natural compound that is registered for use in ischemic stroke, head trauma and neurological disorders. It enters the phosphatidylcholine synthesis pathway as a rate-limiting step and is involved in the modulation of a large number of metabolic pathways and neurotransmitter levels, and also in the biosynthesis of phospholipids in neuronal membranes. This short review highlights the potential role of citicoline as part of adjunct therapy in the treatment of infectious diseases.
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Affiliation(s)
- Ronan Jambou
- Vascular Immunology Unit, Faculty of Medicine, University of Sydney, Parramatta Road, Camperdown, NSW 2042, Australia.
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Clonal diversity within infections and the virulence of a malaria parasite, Plasmodium mexicanum. Parasitology 2008; 135:1363-72. [PMID: 18937882 DOI: 10.1017/s0031182008004964] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Both verbal and mathematical models of parasite virulence predict that genetic diversity of microparasite infections will influence the level of costs suffered by the host. We tested this idea by manipulating the number of co-existing clones of Plasmodium mexicanum in its natural vertebrate host, the fence lizard Sceloporus occidentalis. We established replicate infections of P. mexicanum made up of 1, 2, 3, or >3 clones (scored using 3 microsatellite loci) to observe the influence of clone number on several measures of parasite virulence. Clonal diversity did not affect body growth or production of immature erythrocytes. Blood haemoglobin concentration was highest for the most genetically complex infections (equal to that of non-infected lizards), and blood glucose levels and rate of blood clotting was highest for the most diverse infections (with greater glucose and more rapid clotting than non-infected animals). Neither specific clones nor parasitaemia were associated with virulence. In this first experiment that manipulated the clonal diversity of a natural Plasmodium-host system, the cost of infection with 1 or 2 clones of P. mexicanum was similar to that previously reported for infected lizards, but the most complex infections had either no cost or could be beneficial for the host.
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Susomboon P, Iwagami M, Tangpukdee N, Krusood S, Looareesuwan S, Kano S. Differences in genetic population structures of Plasmodium falciparum isolates from patients along Thai-Myanmar border with severe or uncomplicated malaria. Malar J 2008; 7:212. [PMID: 18937873 PMCID: PMC2576340 DOI: 10.1186/1475-2875-7-212] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Accepted: 10/21/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There have been many reports on the population genetic structures of Plasmodium falciparum from different endemic regions, but few studies have examined the characteristics of isolates from patients with different clinical outcomes. The population genetic structures of P. falciparum isolates from patients with either severe or uncomplicated malaria were examined. METHODS Twelve microsatellite DNA loci from P. falciparum were used to assess the population genetic structures of 50 isolates (i.e., 25 isolates from patients with severe malaria and 25 from patients with uncomplicated malaria) collected in the Thai-Myanmar border area between 2002 and 2005. RESULTS Genetic diversity and effective population sizes were greater in the uncomplicated malaria group than in the severe malaria group. Evidence of genetic bottlenecks was not observed in either group. Strong linkage disequilibrium was observed in the uncomplicated malaria group. The groups demonstrated significant genetic differentiation (P < 0.05), and allele frequencies for 3 of the 12 microsatellite loci differed significantly between the two groups. CONCLUSION These findings suggest that the genetic structure of P. falciparum populations in patients with severe malaria differs from that in patients with uncomplicated malaria. The microsatellite loci used in this study were presumably unrelated to antigenic features of the parasites, but, these findings suggest that some loci may influence the clinical outcome of malaria.
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Affiliation(s)
- Pannapa Susomboon
- Department of Appropriate Technology Development and Transfer Research Institute, International Medical Center of Japan, Shinjuku, Tokyo, Japan
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Gadsby N, Lawrence R, Carter R. A study on pathogenicity and mosquito transmission success in the rodent malaria parasite Plasmodium chabaudi adami. Int J Parasitol 2008; 39:347-54. [PMID: 18755194 DOI: 10.1016/j.ijpara.2008.07.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 06/23/2008] [Accepted: 07/04/2008] [Indexed: 11/25/2022]
Abstract
We investigated the parasitology, pathogenicity (virulence) and infectivity to mosquitoes of blood infections in mice, of two strains, DS and DK, of the rodent malaria parasite Plasmodium chabaudi adami. Blood infections of DS were found to be highly pathogenic; the asexual parasites in these infections were fast-growing and showed no evidence of selectivity in their infection of host erythrocytes. In contrast to DS, blood infections of DK were much less pathogenic; the asexual parasites were slower-growing and showed a moderate degree of selectivity to a subset of erythrocytes which were not reticulocytes. In both DS and DK infections, infectivity to mosquitoes was highest before the peak of asexual parasitaemia had occurred; usually this did not coincide with the time when gametocyte numbers in the blood were highest. Infections with the pathogenic DS strain in CBA mice produced fewer gametocytes than did the less pathogenic DK strain. The DS strain infections in both CBA and C57 mice were also significantly much less infective to mosquitoes than the DK strain. Investigations by others on the related rodent malaria parasite subspecies, Plasmodium chabaudi chabaudi, have indicated that the mosquito infectivity of blood infections in mice tended to be higher in the more pathogenic (virulent) and lower in the less pathogenic strains of this parasite subspecies. This is the converse of the finding of the present investigation of blood infections of P. c. adami in mice in which a more pathogenic, or virulent, strain (DS) of these parasites was significantly much less infective to mosquitoes than was a less pathogenic strain (DK).
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Affiliation(s)
- Naomi Gadsby
- Institute of Immunology and Infection Research, University of Edinburgh, Ashworth Laboratories, Edinburgh, UK
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Abstract
One theory of why some pathogens are virulent (i.e., they damage their host) is that they need to extract resources from their host in order to compete for transmission to new hosts, and this resource extraction can damage the host. Here we describe our studies in malaria that test and support this idea. We go on to show that host immunity can exacerbate selection for virulence and therefore that vaccines that reduce pathogen replication may select for more virulent pathogens, eroding the benefits of vaccination and putting the unvaccinated at greater risk. We suggest that in disease contexts where wild-type parasites can be transmitted through vaccinated hosts, evolutionary outcomes need to be considered.
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Affiliation(s)
- M J Mackinnon
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
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Giha HA, Elbashir MI, A-Elbasit IE, A-Gadir TME, ELGhazali G. Bimodal transmission of cerebral malaria and severe malarial anemia and reciprocal co-existence of sexual and asexual parasitemia in an area of seasonal malaria transmission. Parasitol Res 2008; 103:81-5. [DOI: 10.1007/s00436-008-0931-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Accepted: 02/07/2008] [Indexed: 11/28/2022]
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