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Obi CF, Okpala MI, Anyogu DC, Onyeabor A, Ezeh IO, Ezeokonkwo RC. Comparative pathogenicity of drug-resistant and drug-sensitive Trypanosoma brucei and Trypanosoma congolense infections in Nigerian local dogs. Parasitol Res 2023; 122:49-60. [PMID: 36251088 DOI: 10.1007/s00436-022-07688-0] [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: 06/02/2022] [Accepted: 10/04/2022] [Indexed: 01/12/2023]
Abstract
Animal trypanosomosis is an important endemic and wasting disease in sub-Saharan Africa. Its control relies on chemotherapy, and resistance to trypanocides has been widely reported. The pathogenicity of drug-resistant canine trypanosomes is not clear with scanty information available. Thus, this study assessed the comparative pathogenicity of drug-resistant and drug-sensitive Trypanosoma brucei and Trypanosoma congolense infections in dogs. Twenty Nigerian local dogs were used and were randomly assigned into five groups (A-E) of four dogs each. Group A served as the uninfected-control group, while groups B and C were infected with 106 drug-sensitive T. congolense and T. brucei. Groups D and E were infected with 106 multidrug-resistant T. congolense and T. brucei, respectively. The pre-patent period (PPP), clinical signs, level of parasitaemia (LOP), rectal temperature, body weight, packed cell volume (PCV), red blood cell count (RBC), haemoglobin concentration (HbC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), total leucocyte count (TLC) and survivability were assessed. Groups D and E had longer (p < 0.05) mean PPP than groups B and C. Also, group E dogs had lower (p < 0.05) mean LOP, longer (p < 0.05) mean survivability, and higher (p < 0.05) mean body weight, PCV, HbC and RBC than group C dogs. The clinical signs were very severe in group C dogs, compared to group E dogs. However, these parameters did not differ statistically between groups B and D. Thus, multidrug-resistant T. brucei was of lower pathogenicity than drug-sensitive T. brucei, while multidrug-resistant and drug-sensitive T. congolense had comparable pathogenicity following infection in dogs.
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Affiliation(s)
- Chukwunonso F Obi
- Department of Veterinary Parasitology and Entomology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria.
| | - Michael I Okpala
- Department of Veterinary Parasitology and Entomology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria
| | - Davinson C Anyogu
- Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria
| | - Amaechi Onyeabor
- Department of Veterinary Parasitology and Entomology, College of Veterinary Medicine, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria
| | - Ikenna O Ezeh
- Department of Veterinary Parasitology and Entomology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria
| | - Romanus C Ezeokonkwo
- Department of Veterinary Parasitology and Entomology, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Enugu State, Nigeria
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2
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Competition between strains of Borrelia afzelii in the host tissues and consequences for transmission to ticks. THE ISME JOURNAL 2021; 15:2390-2400. [PMID: 33658621 PMCID: PMC8319436 DOI: 10.1038/s41396-021-00939-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 01/26/2021] [Accepted: 02/11/2021] [Indexed: 01/31/2023]
Abstract
Pathogen species often consist of genetically distinct strains, which can establish mixed infections or coinfections in the host. In coinfections, interactions between pathogen strains can have important consequences for their transmission success. We used the tick-borne bacterium Borrelia afzelii, which is the most common cause of Lyme disease in Europe, as a model multi-strain pathogen to investigate the relationship between coinfection, competition between strains, and strain-specific transmission success. Mus musculus mice were infected with one or two strains of B. afzelii, strain transmission success was measured by feeding ticks on mice, and the distribution of each strain in six different mouse organs and the ticks was measured using qPCR. Coinfection and competition reduced the tissue infection prevalence of both strains and changed their bacterial abundance in some tissues. Coinfection and competition also reduced the transmission success of the B. afzelii strains from the infected hosts to feeding ticks. The ability of the B. afzelii strains to establish infection in the host tissues was strongly correlated with their transmission success to the tick vector. Our study demonstrates that coinfection and competition between pathogen strains inside the host tissues can have major consequences for their transmission success.
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Owolabi ATY, Reece SE, Schneider P. Daily rhythms of both host and parasite affect antimalarial drug efficacy. Evol Med Public Health 2021; 9:208-219. [PMID: 34285807 PMCID: PMC8284615 DOI: 10.1093/emph/eoab013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 04/23/2021] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND OBJECTIVES Circadian rhythms contribute to treatment efficacy in several non-communicable diseases. However, chronotherapy (administering drugs at a particular time-of-day) against infectious diseases has been overlooked. Yet, the daily rhythms of both hosts and disease-causing agents can impact the efficacy of drug treatment. We use the rodent malaria parasite Plasmodium chabaudi, to test whether the daily rhythms of hosts, parasites and their interactions affect sensitivity to the key antimalarial, artemisinin. METHODOLOGY Asexual malaria parasites develop rhythmically in the host's blood, in a manner timed to coordinate with host daily rhythms. Our experiments coupled or decoupled the timing of parasite and host rhythms, and we administered artemisinin at different times of day to coincide with when parasites were either at an early (ring) or later (trophozoite) developmental stage. We quantified the impacts of parasite developmental stage, and alignment of parasite and host rhythms, on drug sensitivity. RESULTS We find that rings were less sensitive to artemisinin than trophozoites, and this difference was exacerbated when parasite and host rhythms were misaligned, with little direct contribution of host time-of-day on its own. Furthermore, the blood concentration of haem at the point of treatment correlated positively with artemisinin efficacy but only when parasite and host rhythms were aligned. CONCLUSIONS AND IMPLICATIONS Parasite rhythms influence drug sensitivity in vivo. The hitherto unknown modulation by alignment between parasite and host daily rhythms suggests that disrupting the timing of parasite development could be a novel chronotherapeutic approach. LAY SUMMARY We reveal that chronotherapy (providing medicines at a particular time-of-day) could improve treatment for malaria infections. Specifically, parasites' developmental stage at the time of treatment and the coordination of timing between parasite and host both affect how well antimalarial drug treatment works.
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Affiliation(s)
- Alíz T Y Owolabi
- Institute of Evolutionary Biology & Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK,Corresponding author. Institute of Evolutionary Biology & Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK. Tel (office): +441316508642; E-mail:
| | - Sarah E Reece
- Institute of Evolutionary Biology & Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Petra Schneider
- Institute of Evolutionary Biology & Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
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4
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Alizon S. Treating symptomatic infections and the co-evolution of virulence and drug resistance. PEER COMMUNITY JOURNAL 2021; 1:e47. [PMID: 38707518 PMCID: PMC7615929 DOI: 10.24072/pcjournal.38] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/07/2024]
Abstract
Antimicrobial therapeutic treatments are by definition applied after the onset of symptoms, which tend to correlate with infection severity. Using mathematical epidemiology models, I explore how this link affects the coevolutionary dynamics between the virulence of an infection, measured via host mortality rate, and its susceptibility to chemotherapy. I show that unless resistance pre-exists in the population, drug-resistant infections are initially more virulent than drug-sensitive ones. As the epidemic unfolds, virulence is more counter-selected in drug-sensitive than in drug-resistant infections. This difference decreases over time and, eventually, the exact shape of genetic trade-offs govern long-term evolutionary dynamics. Using adaptive dynamics, I show that two types of evolutionary stable strategies (ESS) may be reached in the context of this simple model and that, depending on the parameter values, an ESS may only be locally stable. In general, the more the treatment rate increases with virulence, the lower the ESS value. Overall, both on the short-term and long-term, having treatment rate depend on infection virulence tend to favour less virulent strains in drug-sensitive infections. These results highlight the importance of the feedbacks between epidemiology, public health policies and parasite evolution, and have implications for the monitoring of virulence evolution.
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Affiliation(s)
- Samuel Alizon
- Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS, INSERM, Université PSL, Paris, France
- MIVEGEC, CNRS, IRD, Université de Montpellier, France
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5
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Burgert L, Rottmann M, Wittlin S, Gobeau N, Krause A, Dingemanse J, Möhrle JJ, Penny MA. Ensemble modeling highlights importance of understanding parasite-host behavior in preclinical antimalarial drug development. Sci Rep 2020; 10:4410. [PMID: 32157151 PMCID: PMC7064600 DOI: 10.1038/s41598-020-61304-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 02/20/2020] [Indexed: 11/23/2022] Open
Abstract
Emerging drug resistance and high-attrition rates in early and late stage drug development necessitate accelerated development of antimalarial compounds. However, systematic and meaningful translation of drug efficacy and host-parasite dynamics between preclinical testing stages is missing. We developed an ensemble of mathematical within-host parasite growth and antimalarial action models, fitted to extensive data from four antimalarials with different modes of action, to assess host-parasite interactions in two preclinical drug testing systems of murine parasite P. berghei in mice, and human parasite P. falciparum in immune-deficient mice. We find properties of the host-parasite system, namely resource availability, parasite maturation and virulence, drive P. berghei dynamics and drug efficacy, whereas experimental constraints primarily influence P. falciparum infection and drug efficacy. Furthermore, uninvestigated parasite behavior such as dormancy influences parasite recrudescence following non-curative treatment and requires further investigation. Taken together, host-parasite interactions should be considered for meaningful translation of pharmacodynamic properties between murine systems and for predicting human efficacious treatment.
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Affiliation(s)
- Lydia Burgert
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Matthias Rottmann
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Sergio Wittlin
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | | | - Andreas Krause
- Idorsia Pharmaceuticals Ltd, Clinical Pharmacology, Allschwil, Switzerland
| | - Jasper Dingemanse
- Idorsia Pharmaceuticals Ltd, Clinical Pharmacology, Allschwil, Switzerland
| | - Jörg J Möhrle
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Medicines for Malaria Venture, Geneva, Switzerland
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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6
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Izak D, Klim J, Kaczanowski S. Host-parasite interactions and ecology of the malaria parasite-a bioinformatics approach. Brief Funct Genomics 2019; 17:451-457. [PMID: 29697785 DOI: 10.1093/bfgp/ely013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Malaria remains one of the highest mortality infectious diseases. Malaria is caused by parasites from the genus Plasmodium. Most deaths are caused by infections involving Plasmodium falciparum, which has a complex life cycle. Malaria parasites are extremely well adapted for interactions with their host and their host's immune system and are able to suppress the human immune system, erase immunological memory and rapidly alter exposed antigens. Owing to this rapid evolution, parasites develop drug resistance and express novel forms of antigenic proteins that are not recognized by the host immune system. There is an emerging need for novel interventions, including novel drugs and vaccines. Designing novel therapies requires knowledge about host-parasite interactions, which is still limited. However, significant progress has recently been achieved in this field through the application of bioinformatics analysis of parasite genome sequences. In this review, we describe the main achievements in 'malarial' bioinformatics and provide examples of successful applications of protein sequence analysis. These examples include the prediction of protein functions based on homology and the prediction of protein surface localization via domain and motif analysis. Additionally, we describe PlasmoDB, a database that stores accumulated experimental data. This tool allows data mining of the stored information and will play an important role in the development of malaria science. Finally, we illustrate the application of bioinformatics in the development of population genetics research on malaria parasites, an approach referred to as reverse ecology.
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Affiliation(s)
- Dariusz Izak
- Department of Bioinformatics at the Institute of Biochemistry and Biophysics of the Polish Academy of Sciences
| | - Joanna Klim
- Department of Microbial Chemistry at the Institute of Biochemistry and Biophysics of the Polish Academy of Sciences
| | - Szymon Kaczanowski
- Department of Bioinformatics at the Institute of Biochemistry and Biophysics of the Polish Academy of Sciences
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7
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Birget PLG, Greischar MA, Reece SE, Mideo N. Altered life history strategies protect malaria parasites against drugs. Evol Appl 2018; 11:442-455. [PMID: 29636798 PMCID: PMC5891063 DOI: 10.1111/eva.12516] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 06/30/2017] [Indexed: 11/26/2022] Open
Abstract
Drug resistance has been reported against all antimalarial drugs, and while parasites can evolve classical resistance mechanisms (e.g., efflux pumps), it is also possible that changes in life history traits could help parasites evade the effects of treatment. The life history of malaria parasites is governed by an intrinsic resource allocation problem: specialized stages are required for transmission, but producing these stages comes at the cost of producing fewer of the forms required for within-host survival. Drug treatment, by design, alters the probability of within-host survival, and so should alter the costs and benefits of investing in transmission. Here, we use a within-host model of malaria infection to predict optimal patterns of investment in transmission in the face of different drug treatment regimes and determine the extent to which alternative patterns of investment can buffer the fitness loss due to drugs. We show that over a range of drug doses, parasites are predicted to adopt "reproductive restraint" (investing more in asexual replication and less in transmission) to maximize fitness. By doing so, parasites recoup some of the fitness loss imposed by drugs, though as may be expected, increasing dose reduces the extent to which altered patterns of transmission investment can benefit parasites. We show that adaptation to drug-treated infections could result in more virulent infections in untreated hosts. This work emphasizes that in addition to classical resistance mechanisms, drug treatment generates selection for altered parasite life history. Understanding how any shifts in life history will alter the efficacy of drugs, as well as any limitations on such shifts, is important for evaluating and predicting the consequences of drug treatment.
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Affiliation(s)
- Philip L. G. Birget
- Institutes of Evolutionary Biology, Immunology and Infection ResearchUniversity of EdinburghEdinburghUK
| | - Megan A. Greischar
- Department of Ecology & Evolutionary BiologyUniversity of TorontoTorontoONCanada
| | - Sarah E. Reece
- Institutes of Evolutionary Biology, Immunology and Infection ResearchUniversity of EdinburghEdinburghUK
| | - Nicole Mideo
- Department of Ecology & Evolutionary BiologyUniversity of TorontoTorontoONCanada
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8
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Allen RC, Engelstädter J, Bonhoeffer S, McDonald BA, Hall AR. Reversing resistance: different routes and common themes across pathogens. Proc Biol Sci 2017; 284:20171619. [PMID: 28954914 PMCID: PMC5627214 DOI: 10.1098/rspb.2017.1619] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 08/23/2017] [Indexed: 11/12/2022] Open
Abstract
Resistance spreads rapidly in pathogen or pest populations exposed to biocides, such as fungicides and antibiotics, and in many cases new biocides are in short supply. How can resistance be reversed in order to prolong the effectiveness of available treatments? Some key parameters affecting reversion of resistance are well known, such as the fitness cost of resistance. However, the population biological processes that actually cause resistance to persist or decline remain poorly characterized, and consequently our ability to manage reversion of resistance is limited. Where do susceptible genotypes that replace resistant lineages come from? What is the epidemiological scale of reversion? What information do we need to predict the mechanisms or likelihood of reversion? Here, we define some of the population biological processes that can drive reversion, using examples from a wide range of taxa and biocides. These processes differ primarily in the origin of revertant genotypes, but also in their sensitivity to factors such as coselection and compensatory evolution that can alter the rate of reversion, and the likelihood that resistance will re-emerge upon re-exposure to biocides. We therefore argue that discriminating among different types of reversion allows for better prediction of where resistance is most likely to persist.
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Affiliation(s)
- Richard C Allen
- Institute of Integrative Biology, ETH Zürich, CH-8092 Zurich, Switzerland
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | | | - Bruce A McDonald
- Institute of Integrative Biology, ETH Zürich, CH-8092 Zurich, Switzerland
| | - Alex R Hall
- Institute of Integrative Biology, ETH Zürich, CH-8092 Zurich, Switzerland
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9
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Birget PLG, Repton C, O'Donnell AJ, Schneider P, Reece SE. Phenotypic plasticity in reproductive effort: malaria parasites respond to resource availability. Proc Biol Sci 2017; 284:20171229. [PMID: 28768894 PMCID: PMC5563815 DOI: 10.1098/rspb.2017.1229] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 06/28/2017] [Indexed: 12/11/2022] Open
Abstract
The trade-off between survival and reproduction is fundamental in the life history of all sexually reproducing organisms. This includes malaria parasites, which rely on asexually replicating stages for within-host survival and on sexually reproducing stages (gametocytes) for between-host transmission. The proportion of asexual stages that form gametocytes (reproductive effort) varies during infections-i.e. is phenotypically plastic-in response to changes in a number of within-host factors, including anaemia. However, how the density and age structure of red blood cell (RBC) resources shape plasticity in reproductive effort and impacts upon parasite fitness is controversial. Here, we examine how and why the rodent malaria parasite Plasmodium chabaudi alters its reproductive effort in response to experimental perturbations of the density and age structure of RBCs. We show that all four of the genotypes studied increase reproductive effort when the proportion of RBCs that are immature is elevated during host anaemia, and that the responses of the genotypes differ. We propose that anaemia (counterintuitively) generates a resource-rich environment in which parasites can afford to allocate more energy to reproduction (i.e. transmission) and that anaemia also exposes genetic variation to selection. From an applied perspective, adaptive plasticity in parasite reproductive effort could explain the maintenance of genetic variation for virulence and why anaemia is often observed as a risk factor for transmission in human infections.
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Affiliation(s)
- Philip L G Birget
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Charlotte Repton
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Aidan J O'Donnell
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Petra Schneider
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Sarah E Reece
- Institutes of Evolutionary Biology, and Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3FL, UK
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10
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Smith DRM, Mideo N. Modelling the evolution of HIV-1 virulence in response to imperfect therapy and prophylaxis. Evol Appl 2017; 10:297-309. [PMID: 28250813 PMCID: PMC5322411 DOI: 10.1111/eva.12458] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 12/15/2016] [Indexed: 12/11/2022] Open
Abstract
Average HIV-1 virulence appears to have evolved in different directions in different host populations since antiretroviral therapy first became available, and models predict that HIV drugs can select for either higher or lower virulence, depending on how treatment is administered. However, HIV virulence evolution in response to "leaky" therapy (treatment that imperfectly suppresses viral replication) and the use of preventive drugs (pre-exposure prophylaxis) has not been explored. Using adaptive dynamics, we show that higher virulence can evolve when antiretroviral therapy is imperfectly effective and that this evolution erodes some of the long-term clinical and epidemiological benefits of HIV treatment. The introduction of pre-exposure prophylaxis greatly reduces infection prevalence, but can further amplify virulence evolution when it, too, is leaky. Increasing the uptake rate of these imperfect interventions increases selection for higher virulence and can lead to counterintuitive increases in infection prevalence in some scenarios. Although populations almost always fare better with access to interventions than without, untreated individuals could experience particularly poor clinical outcomes when virulence evolves. These findings predict that antiretroviral drugs may have underappreciated evolutionary consequences, but that maximizing drug efficacy can prevent this evolutionary response. We suggest that HIV virulence evolution should be closely monitored as access to interventions continues to improve.
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Affiliation(s)
- David R. M. Smith
- Department of Ecology and Evolutionary BiologyUniversity of TorontoTorontoONCanada
| | - Nicole Mideo
- Department of Ecology and Evolutionary BiologyUniversity of TorontoTorontoONCanada
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11
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Antibody-independent mechanisms regulate the establishment of chronic Plasmodium infection. Nat Microbiol 2017; 2:16276. [PMID: 28165471 DOI: 10.1038/nmicrobiol.2016.276] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 12/22/2016] [Indexed: 01/15/2023]
Abstract
Malaria is caused by parasites of the genus Plasmodium. All human-infecting Plasmodium species can establish long-lasting chronic infections1-5, creating an infectious reservoir to sustain transmission1,6. It is widely accepted that the maintenance of chronic infection involves evasion of adaptive immunity by antigenic variation7. However, genes involved in this process have been identified in only two of five human-infecting species: Plasmodium falciparum and Plasmodium knowlesi. Furthermore, little is understood about the early events in the establishment of chronic infection in these species. Using a rodent model we demonstrate that from the infecting population, only a minority of parasites, expressing one of several clusters of virulence-associated pir genes, establishes a chronic infection. This process occurs in different species of parasites and in different hosts. Establishment of chronicity is independent of adaptive immunity and therefore different from the mechanism proposed for maintenance of chronic P. falciparum infections7-9. Furthermore, we show that the proportions of parasites expressing different types of pir genes regulate the time taken to establish a chronic infection. Because pir genes are common to most, if not all, species of Plasmodium10, this process may be a common way of regulating the establishment of chronic infections.
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12
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Paz-Y-Miño-C G, Espinosa A. Kin Discrimination in Protists: From Many Cells to Single Cells and Backwards. J Eukaryot Microbiol 2016; 63:367-77. [PMID: 26873616 PMCID: PMC4856593 DOI: 10.1111/jeu.12306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Revised: 02/03/2016] [Accepted: 02/07/2016] [Indexed: 12/16/2022]
Abstract
During four decades (1960-1990s), the conceptualization and experimental design of studies in kin recognition relied on work with multicellular eukaryotes, particularly Unikonta (including invertebrates and vertebrates) and some Bikonta (including plants). This pioneering research had an animal behavior approach. During the 2000s, work on taxa-, clone- and kin-discrimination and recognition in protists produced genetic and molecular evidence that unicellular organisms (e.g. Saccharomyces, Dictyostelium, Polysphondylium, Tetrahymena, Entamoeba and Plasmodium) could distinguish between same (self or clone) and different (diverse clones), as well as among conspecifics of close or distant genetic relatedness. Here, we discuss some of the research on the genetics of kin discrimination/recognition and highlight the scientific progress made by switching emphasis from investigating multicellular to unicellular systems (and backwards). We document how studies with protists are helping us to understand the microscopic, cellular origins and evolution of the mechanisms of kin discrimination/recognition and their significance for the advent of multicellularity. We emphasize that because protists are among the most ancient organisms on Earth, belong to multiple taxonomic groups and occupy all environments, they can be central to reexamining traditional hypotheses in the field of kin recognition, reformulating concepts, and generating new knowledge.
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Affiliation(s)
- Guillermo Paz-Y-Miño-C
- New England Center for the Public Understanding of Science, Roger Williams University, One Old Ferry Road, Bristol, Rhode Island, 02809
| | - Avelina Espinosa
- New England Center for the Public Understanding of Science, Roger Williams University, One Old Ferry Road, Bristol, Rhode Island, 02809
- Department of Biology, Roger Williams University, One Old Ferry Road, Bristol, Rhode Island, 02809
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13
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Cao DH, Wang JC, Liu J, Du YT, Cui LW, Cao YM. Bacillus Calmette-Guérin-inoculation at different time points influences the outcome of C57BL/6 mice infected with Plasmodium chabaudi chabaudi AS. Folia Parasitol (Praha) 2016; 63. [PMID: 27188912 DOI: 10.14411/fp.2016.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Accepted: 03/03/2016] [Indexed: 11/19/2022]
Abstract
Bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium tuberculosis vaccine. We performed a series of co-infection experiments with BCG-Plasmodium chabaudi chabaudi Landau, 1965 AS using C57BL/6 mice to analyse whether BCG can affect the development of protective immunity to infection with Plasmodium spp. and the mechanism of this protection. We divided mice into four groups: BCG-inoculation 4 weeks prior to P. c. chabaudi AS infection (B-4w-Pc); simultaneous BCG-inoculation and P. c. chabaudi AS infection (Pc+B); BCG-inoculation 3 days post P. c. chabaudi AS (Pc-3-B) infection; and mono-P. c. chabaudi AS infection as control (Pc). The parasitemia level in the B-4w-Pc group was noticeably higher than control group at 6-19 days post infection (dpi). Compared with the control group, the proportion of CD4(+)CD69(+) T cells was significantly reduced 5, 8 and 12 dpi, but the proportion of CD4(+)CD25(+)Foxp3(+) Tregs was significantly increased in the B-4w-Pc group on 5 and 8 dpi. The B-4w-Pc group also demonstrated reduced levels of IFN-γ and TNF-α on 5 and 8 dpi and significantly elevated level of IL-10 on 12 dpi. There were significantly fewer mDCs (CD11c(+)CD11b(+)) and pDCs (CD11c(+)B220(+)) in the B-4w-Pc group than the control group at all the time points post infection and the expression of MHC II was noticeably reduced on day 8 pi. Our findings confirmed that BCG inoculation prior to Plasmodium infection resulted in excessive activation and proliferation of Tregs and upregulation of anti-inflammatory mediators, which inhibited establishment of a Th1-dominant immune response during the early stages of Plasmodium infection by inhibiting dendritive cells response. BCG inoculation prior to P. c. chabaudi AS infection may contribute to overgrowth of parasites as well as mortality in mice.
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Affiliation(s)
- Dong-Hua Cao
- Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, China.,Aristogenesis Center, Hospital of People's Liberation Army, Shenyang, China
| | - Ji-Chun Wang
- Department of Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Jun Liu
- Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Yun-Ting Du
- Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Li-Wang Cui
- Department of Entomology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Ya-Ming Cao
- Department of Immunology, College of Basic Medical Sciences, China Medical University, Shenyang, China
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Obaldía N, Dow GS, Gerena L, Kyle D, Otero W, Mantel PY, Baro N, Daniels R, Mukherjee A, Childs LM, Buckee C, Duraisingh MT, Volkman SK, Wirth DF, Marti M. Altered drug susceptibility during host adaptation of a Plasmodium falciparum strain in a non-human primate model. Sci Rep 2016; 6:21216. [PMID: 26880111 PMCID: PMC4754742 DOI: 10.1038/srep21216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 01/19/2016] [Indexed: 01/07/2023] Open
Abstract
Infections with Plasmodium falciparum, the most pathogenic of the Plasmodium species affecting man, have been reduced in part due to artemisinin-based combination therapies. However, artemisinin resistant parasites have recently emerged in South-East Asia. Novel intervention strategies are therefore urgently needed to maintain the current momentum for control and elimination of this disease. In the present study we characterize the phenotypic and genetic properties of the multi drug resistant (MDR) P. falciparum Thai C2A parasite strain in the non-human Aotus primate model, and across multiple passages. Aotus infections with C2A failed to clear upon oral artesunate and mefloquine treatment alone or in combination, and ex vivo drug assays demonstrated reduction in drug susceptibility profiles in later Aotus passages. Further analysis revealed mutations in the pfcrt and pfdhfr loci and increased parasite multiplication rate (PMR) across passages, despite elevated pfmdr1 copy number. Altogether our experiments suggest alterations in parasite population structure and increased fitness during Aotus adaptation. We also present data of early treatment failures with an oral artemisinin combination therapy in a pre-artemisinin resistant P. falciparum Thai isolate in this animal model.
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Affiliation(s)
- Nicanor Obaldía
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States.,Center for the Evaluation of Antimalarial Drugs and Vaccines, Tropical Medicine Research/Instituto Conmemorativo Gorgas de Estudios de la Salud, Panamá City, Republic of Panama
| | - Geoffrey S Dow
- Walter Reed Army Institute of Research, Silver Springs, MD, United States
| | - Lucia Gerena
- Walter Reed Army Institute of Research, Silver Springs, MD, United States
| | - Dennis Kyle
- Department of Global Health, University of South Florida, Tampa, FL, United States
| | - William Otero
- Center for the Evaluation of Antimalarial Drugs and Vaccines, Tropical Medicine Research/Instituto Conmemorativo Gorgas de Estudios de la Salud, Panamá City, Republic of Panama
| | - Pierre-Yves Mantel
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Nicholas Baro
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Rachel Daniels
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Angana Mukherjee
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Lauren M Childs
- Center for Communicable Disease Dynamics and Harvard
- T.H. Chan School of Public Health, Boston, MA, United States.,Department of Epidemiology, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Caroline Buckee
- Center for Communicable Disease Dynamics and Harvard
- T.H. Chan School of Public Health, Boston, MA, United States.,Department of Epidemiology, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
| | - Sarah K Volkman
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States.,The Broad Institute of MIT and Harvard, Cambridge, MA, United States.,School of Nursing and Health Sciences, Simmons College, Boston, MA United States
| | - Dyann F Wirth
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States.,The Broad Institute of MIT and Harvard, Cambridge, MA, United States
| | - Matthias Marti
- Department of Immunology and Infectious Diseases, Harvard
- T.H. Chan School of Public Health, Boston, MA, United States
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15
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Kennedy DA, Kurath G, Brito IL, Purcell MK, Read AF, Winton JR, Wargo AR. Potential drivers of virulence evolution in aquaculture. Evol Appl 2016; 9:344-54. [PMID: 26834829 PMCID: PMC4721074 DOI: 10.1111/eva.12342] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 10/06/2015] [Indexed: 01/24/2023] Open
Abstract
Infectious diseases are economically detrimental to aquaculture, and with continued expansion and intensification of aquaculture, the importance of managing infectious diseases will likely increase in the future. Here, we use evolution of virulence theory, along with examples, to identify aquaculture practices that might lead to the evolution of increased pathogen virulence. We identify eight practices common in aquaculture that theory predicts may favor evolution toward higher pathogen virulence. Four are related to intensive aquaculture operations, and four others are related specifically to infectious disease control. Our intention is to make aquaculture managers aware of these risks, such that with increased vigilance, they might be able to detect and prevent the emergence and spread of increasingly troublesome pathogen strains in the future.
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Affiliation(s)
- David A Kennedy
- Center for Infectious Disease Dynamics Departments of Biology and Entomology The Pennsylvania State University University Park PA USA; Fogarty International Center National Institutes of Health Bethesda MD USA
| | - Gael Kurath
- U.S. Geological Survey Western Fisheries Research Center Seattle WA USA
| | - Ilana L Brito
- Massachusetts Institute of Technology Cambridge MA USA
| | - Maureen K Purcell
- U.S. Geological Survey Western Fisheries Research Center Seattle WA USA
| | - Andrew F Read
- Center for Infectious Disease Dynamics Departments of Biology and Entomology The Pennsylvania State University University Park PA USA; Fogarty International Center National Institutes of Health Bethesda MD USA
| | - James R Winton
- U.S. Geological Survey Western Fisheries Research Center Seattle WA USA
| | - Andrew R Wargo
- Virginia Institute of Marine Science College of William and Mary Gloucester Point VA USA
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16
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Seco-Hidalgo V, Osuna A, Pablos LMD. To bet or not to bet: deciphering cell to cell variation in protozoan infections. Trends Parasitol 2015; 31:350-6. [PMID: 26070403 DOI: 10.1016/j.pt.2015.05.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/11/2015] [Accepted: 05/13/2015] [Indexed: 11/16/2022]
Abstract
Some of the most crucial phenotypic aspects of parasites, such as an antigen-coated surface, parasite sexual differentiation, virulence, and drug resistance, rely on adaptive plasticity and/or stochastic events. At a population level, cell to cell variability represents an avenue for rapid response to drastic changes in the environment. Single cell approaches can be used to unravel the different strategies used by parasites to survive in the context of regulated transcriptional control (apicomplexa) or in its absence (kinetoplastids).
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Affiliation(s)
- Víctor Seco-Hidalgo
- Biochemistry and Molecular Parasitology Research Group, Department of Parasitology, University of Granada, Campus de Fuentenueva, Granada, Spain
| | - Antonio Osuna
- Biochemistry and Molecular Parasitology Research Group, Department of Parasitology, University of Granada, Campus de Fuentenueva, Granada, Spain
| | - Luis Miguel De Pablos
- Biochemistry and Molecular Parasitology Research Group, Department of Parasitology, University of Granada, Campus de Fuentenueva, Granada, Spain; Centre for Immunology and Infection (CII), Biology Department, University of York, York, UK.
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17
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Within-host competition does not select for virulence in malaria parasites; studies with Plasmodium yoelii. PLoS Pathog 2015; 11:e1004628. [PMID: 25658331 PMCID: PMC4450063 DOI: 10.1371/journal.ppat.1004628] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 12/14/2014] [Indexed: 11/19/2022] Open
Abstract
In endemic areas with high transmission intensities, malaria infections are very often composed of multiple genetically distinct strains of malaria parasites. It has been hypothesised that this leads to intra-host competition, in which parasite strains compete for resources such as space and nutrients. This competition may have repercussions for the host, the parasite, and the vector in terms of disease severity, vector fitness, and parasite transmission potential and fitness. It has also been argued that within-host competition could lead to selection for more virulent parasites. Here we use the rodent malaria parasite Plasmodium yoelii to assess the consequences of mixed strain infections on disease severity and parasite fitness. Three isogenic strains with dramatically different growth rates (and hence virulence) were maintained in mice in single infections or in mixed strain infections with a genetically distinct strain. We compared the virulence (defined as harm to the mammalian host) of mixed strain infections with that of single infections, and assessed whether competition impacted on parasite fitness, assessed by transmission potential. We found that mixed infections were associated with a higher degree of disease severity and a prolonged infection time. In the mixed infections, the strain with the slower growth rate was often responsible for the competitive exclusion of the faster growing strain, presumably through host immune-mediated mechanisms. Importantly, and in contrast to previous work conducted with Plasmodium chabaudi, we found no correlation between parasite virulence and transmission potential to mosquitoes, suggesting that within-host competition would not drive the evolution of parasite virulence in P. yoelii.
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18
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Pollitt LC, Sim D, Salathé R, Read AF. Understanding genetic variation in in vivo tolerance to artesunate: implications for treatment efficacy and resistance monitoring. Evol Appl 2014; 8:296-304. [PMID: 25861387 PMCID: PMC4380923 DOI: 10.1111/eva.12194] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/20/2014] [Indexed: 01/10/2023] Open
Abstract
Artemisinin-based drugs are the front-line weapon in the treatment of human malaria cases, but there is concern that recent reports of slow clearing infections may signal developing resistance to treatment. In the absence of molecular markers for resistance, current efforts to monitor drug efficacy are based on the rate at which parasites are cleared from infections. However, some knowledge of the standing variation in parasite susceptibility is needed to identify a meaningful increase in infection half-life. Here, we show that five previously unexposed genotypes of the rodent malaria parasite Plasmodium chabaudi differ substantially in their in vivo response to treatment. Slower clearance rates were not linked to parasite virulence or growth rate, going against the suggestion that drug treatment will drive the evolution of virulence in this system. The level of variation observed here in a relatively small number of genotypes suggests existing ‘resistant’ parasites could be present in the population and therefore, increased parasite clearance rates could represent selection on pre-existing variation rather than de novo resistance events. This has implications for resistance monitoring as susceptibility may depend on evolved traits unrelated to drug exposure.
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Affiliation(s)
- Laura C Pollitt
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA ; Centre for Immunity, Infection and Evolution, University of Edinburgh Edinburgh, UK
| | - Derek Sim
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA
| | - Rahel Salathé
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA
| | - Andrew F Read
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA ; Department of Entomology, The Pennsylvania State University University Park, PA, USA ; Fogarty International Center, National Institutes of Health Bethesda, MD, USA
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19
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Beshir KB, Sutherland CJ, Sawa P, Drakeley CJ, Okell L, Mweresa CK, Omar SA, Shekalaghe SA, Kaur H, Ndaro A, Chilongola J, Schallig HDFH, Sauerwein RW, Hallett RL, Bousema T. Residual Plasmodium falciparum parasitemia in Kenyan children after artemisinin-combination therapy is associated with increased transmission to mosquitoes and parasite recurrence. J Infect Dis 2013; 208:2017-24. [PMID: 23945376 PMCID: PMC3836468 DOI: 10.1093/infdis/jit431] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 08/07/2013] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Parasite clearance time after artemisinin-based combination therapy (ACT) may be increasing in Asian and African settings. The association between parasite clearance following ACT and transmissibility is currently unknown. METHODS We determined parasite clearance dynamics by duplex quantitative polymerase chain reaction (qPCR) in samples collected in the first 3 days after treatment of uncomplicated malaria with ACT. Gametocyte carriage was determined by Pfs25 quantitative nucleic acid sequence-based amplification assays; infectiousness to mosquitoes by membrane-feeding assays on day 7 after treatment. RESULTS Residual parasitemia was detected by qPCR in 31.8% (95% confidence interval [CI], 24.6-39.8) of the children on day 3 after initiation of treatment. Residual parasitemia was associated with a 2-fold longer duration of gametocyte carriage (P = .0007), a higher likelihood of infecting mosquitoes (relative risk, 1.95; 95% CI, 1.17-3.24; P = .015), and a higher parasite burden in mosquitoes (incidence rate ratio, 2.92; 95% CI, 1.61-5.31; P < .001). Children with residual parasitemia were also significantly more likely to experience microscopically detectable parasitemia during follow-up (relative risk, 11.25; 95% CI, 4.08-31.01; P < .001). CONCLUSIONS Residual submicroscopic parasitemia is common after ACT and is associated with a higher transmission potential. Residual parasitemia may also have consequences for individual patients because of its higher risk of recurrent parasitemia.
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Affiliation(s)
| | | | - Patrick Sawa
- Human Health Division, International Centre of Insect Physiology and Ecology, Mbita Point
| | | | - Lucy Okell
- Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, United Kingdom
| | - Collins K. Mweresa
- Human Health Division, International Centre of Insect Physiology and Ecology, Mbita Point
| | | | - Seif A. Shekalaghe
- Kilimanjaro Clinical Medical Research Institute, Kilimanjaro Christian Medical Centre, Moshi
- Ifakara Health Institute, Bagamoyo, Tanzania
| | - Harparkash Kaur
- Department of Clinical Research, London School of Hygiene and Tropical Medicine
| | - Arnold Ndaro
- Kilimanjaro Clinical Medical Research Institute, Kilimanjaro Christian Medical Centre, Moshi
| | - Jaffu Chilongola
- Kilimanjaro Clinical Medical Research Institute, Kilimanjaro Christian Medical Centre, Moshi
| | | | - Robert W. Sauerwein
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | | | - Teun Bousema
- Department of Immunology and Infection
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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20
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O'Donnell AJ, Mideo N, Reece SE. Disrupting rhythms in Plasmodium chabaudi: costs accrue quickly and independently of how infections are initiated. Malar J 2013; 12:372. [PMID: 24160251 PMCID: PMC3819465 DOI: 10.1186/1475-2875-12-372] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 10/23/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In the blood, the synchronous malaria parasite, Plasmodium chabaudi, exhibits a cell-cycle rhythm of approximately 24 hours in which transitions between developmental stages occur at particular times of day in the rodent host. Previous experiments reveal that when the timing of the parasite's cell-cycle rhythm is perturbed relative to the circadian rhythm of the host, parasites suffer a (~50%) reduction in asexual stages and gametocytes. Why it matters for parasites to have developmental schedules in synchronization with the host's rhythm is unknown. The experiment presented here investigates this issue by: (a) validating that the performance of P. chabaudi is negatively affected by mismatch to the host circadian rhythm; (b) testing whether the effect of mismatch depends on the route of infection or the developmental stage of inoculated parasites; and, (c) examining whether the costs of mismatch are due to challenges encountered upon initial infection and/or due to ongoing circadian host processes operating during infection. METHODS The experiment simultaneously perturbed the time of day infections were initiated, the stage of parasite inoculated, and the route of infection. The performance of parasites during the growth phase of infections was compared across the cross-factored treatment groups (i e, all combinations of treatments were represented). RESULTS The data show that mismatch to host rhythms is costly for parasites, reveal that this phenomenon does not depend on the developmental stage of parasites nor the route of infection, and suggest that processes operating at the initial stages of infection are responsible for the costs of mismatch. Furthermore, mismatched parasites are less virulent, in that they cause less anaemia to their hosts. CONCLUSION It is beneficial for parasites to be in synchronization with their host's rhythm, regardless of the route of infection or the parasite stage inoculated. Given that arrested cell-cycle development (quiescence) is implicated in tolerance to drugs, understanding how parasite schedules are established and maintained in the blood is important.
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Affiliation(s)
- Aidan J O'Donnell
- Institutes of Evolution, Immunology and Infection Research, University of Edinburgh, Edinburgh, UK.
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21
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Rosenthal PJ. The interplay between drug resistance and fitness in malaria parasites. Mol Microbiol 2013; 89:1025-38. [PMID: 23899091 DOI: 10.1111/mmi.12349] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2013] [Indexed: 12/01/2022]
Abstract
Controlling the spread of antimalarial drug resistance, especially resistance of Plasmodium falciparum to artemisinin-based combination therapies, is a high priority. Available data indicate that, as with other microorganisms, the spread of drug-resistant malaria parasites is limited by fitness costs that frequently accompany resistance. Resistance-mediating polymorphisms in malaria parasites have been identified in putative drug transporters and in target enzymes. The impacts of these polymorphisms on parasite fitness have been characterized in vitro and in animal models. Additional insights have come from analyses of samples from clinical studies, both evaluating parasites under different selective pressures and determining the clinical consequences of infection with different parasites. With some exceptions, resistance-mediating polymorphisms lead to malaria parasites that, compared with wild type, grow less well in culture and in animals, and are replaced by wild type when drug pressure diminishes in the clinical setting. In some cases, the fitness costs of resistance may be offset by compensatory mutations that increase virulence or changes that enhance malaria transmission. However, not enough is known about effects of resistance mediators on parasite fitness. A better appreciation of the costs of fitness-mediating mutations will facilitate the development of optimal guidelines for the treatment and prevention of malaria.
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Affiliation(s)
- Philip J Rosenthal
- Department of Medicine, University of California, San Francisco, CA, 94143, USA
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22
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Barclay VC. Variation in host resistance could limit the spread of more broadly virulent pathogens. Virulence 2013; 4:347-9. [PMID: 23689611 PMCID: PMC3714125 DOI: 10.4161/viru.25061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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23
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Kubinak JL, Potts WK. Host resistance influences patterns of experimental viral adaptation and virulence evolution. Virulence 2013; 4:410-8. [PMID: 23645287 DOI: 10.4161/viru.24724] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Infectious diseases are major threats to all living systems, so understanding the forces of selection that limit the evolution of more virulent pathogens is of fundamental importance; this includes the practical application of identifying possible mitigation strategies for at-risk host populations. The evolution of more virulent pathogens has been classically understood to be limited by the tradeoff between within-host growth rate and transmissibility. Importantly, heterogeneity among hosts can influence both of these factors. However, despite our substantial understanding of how the immune system operates to control pathogen replication during infection, we have only a limited appreciation of how variability in intrinsic (i.e., genetically determined) levels of host resistance influences patterns of pathogen adaptation and virulence evolution. Here, we describe results from experimental evolution studies using a model host-pathogen (virus-mammal) system; we demonstrate that variability in intrinsic levels of resistance among host genotypes can have significant effects on patterns of pathogen adaptation and virulence evolution during serial passage. Both the magnitude of adaptive response as well as the degree of pathogen specialization was positively correlated with host resistance, while mean overall virulence of post-passage virus was negatively correlated with host resistance. These results are consistent with a model whereby resistant host genotypes impose stronger selection on adapting pathogen populations, which in turn leads to the evolution of more specialized pathogen variants whose overall (i.e., mean) virulence across host genotypes is reduced.
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Affiliation(s)
- Jason L Kubinak
- Division of Microbiology and Immunology, Department of Pathology; School of Medicine, University of Utah; Salt Lake City, UT USA.
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24
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Pollitt LC, Churcher TS, Dawes EJ, Khan SM, Sajid M, Basáñez MG, Colegrave N, Reece SE. Costs of crowding for the transmission of malaria parasites. Evol Appl 2013; 6:617-29. [PMID: 23789029 PMCID: PMC3684743 DOI: 10.1111/eva.12048] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 12/13/2012] [Accepted: 12/13/2012] [Indexed: 01/03/2023] Open
Abstract
The utility of using evolutionary and ecological frameworks to understand the dynamics of infectious diseases is gaining increasing recognition. However, integrating evolutionary ecology and infectious disease epidemiology is challenging because within-host dynamics can have counterintuitive consequences for between-host transmission, especially for vector-borne parasites. A major obstacle to linking within- and between-host processes is that the drivers of the relationships between the density, virulence, and fitness of parasites are poorly understood. By experimentally manipulating the intensity of rodent malaria (Plasmodium berghei) infections in Anopheles stephensi mosquitoes under different environmental conditions, we show that parasites experience substantial density-dependent fitness costs because crowding reduces both parasite proliferation and vector survival. We then use our data to predict how interactions between parasite density and vector environmental conditions shape within-vector processes and onward disease transmission. Our model predicts that density-dependent processes can have substantial and unexpected effects on the transmission potential of vector-borne disease, which should be considered in the development and evaluation of transmission-blocking interventions.
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Affiliation(s)
- Laura C Pollitt
- Institute of Evolutionary Biology, University of Edinburgh Edinburgh, UK ; Center for Infectious Disease Dynamics, Pennsylvania State University University Park, PA, USA
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