1
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Prat M, Jeanneau M, Rakotoarivony I, Duhayon M, Simonin Y, Savini G, Labbé P, Alout H. Virulence and transmission vary between Usutu virus lineages in Culex pipiens. PLoS Negl Trop Dis 2024; 18:e0012295. [PMID: 38935783 PMCID: PMC11236178 DOI: 10.1371/journal.pntd.0012295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 07/10/2024] [Accepted: 06/14/2024] [Indexed: 06/29/2024] Open
Abstract
Usutu virus (USUV) is a zoonotic arbovirus infecting mainly wild birds. It is transmitted by ornithophilic mosquitoes, mainly of the genus Culex from birds to birds and to several vertebrate dead-end hosts. Several USUV lineages, differing in their virulence have emerged in the last decades and now co-circulate in Europe, impacting human populations. However, their relative transmission and effects on their mosquito vectors is still not known. We thus compared the vector competence and survival of Culex pipiens mosquitoes experimentally infected with two distinct USUV lineages, EU2 and EU3, that are known to differ in their virulence and replication in vertebrate hosts. Infection rate was variable among blood feeding assays but variations between EU2 and EU3 lineages were consistent suggesting that Culex pipiens was equally susceptible to infection by both lineages. However, EU3 viral load increased with viral titer in the blood meal while EU2 viral load was high at all titers which suggest a greater replication of EU2 than EU3 in mosquito. While their relative transmission efficiencies are similar, at least at low blood meal titer, positive correlation between transmission and blood meal titer was observed for EU3 only. Contrary to published results in vertebrates, EU3 induced a higher mortality to mosquitoes (i.e. virulence) than EU2 whatever the blood meal titer. Therefore, we found evidence of lineage-specific differences in vectorial capacity and virulence to both the vector and vertebrate host which lead to balanced propagation of both viral lineages. These results highlight the need to decipher the interactions between vectors, vertebrate hosts, and the diversity of arbovirus lineages to fully understand transmission dynamics.
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Affiliation(s)
- Maxime Prat
- Institut des Sciences de l'Evolution de Montpellier, Université de Montpellier-CNRS-IRD, Montpellier, France
- UMR ASTRE, Univ Montpellier, INRAE-CIRAD, Montpellier, France
| | | | | | - Maxime Duhayon
- UMR ASTRE, Univ Montpellier, INRAE-CIRAD, Montpellier, France
| | - Yannick Simonin
- Pathogenesis and Control of Chronic Infections, Université de Montpellier-INSERM-EFS, Montpellier, France
| | - Giovanni Savini
- OIE Reference Centre for West Nile Disease, Istituto Zooprofilattico Sperimentale "G. Caporale", Teramo, Italy
| | - Pierrick Labbé
- Institut des Sciences de l'Evolution de Montpellier, Université de Montpellier-CNRS-IRD, Montpellier, France
| | - Haoues Alout
- UMR ASTRE, Univ Montpellier, INRAE-CIRAD, Montpellier, France
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2
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Hanley KA, Cecilia H, Azar SR, Moehn BA, Gass JT, Oliveira da Silva NI, Yu W, Yun R, Althouse BM, Vasilakis N, Rossi SL. Trade-offs shaping transmission of sylvatic dengue and Zika viruses in monkey hosts. Nat Commun 2024; 15:2682. [PMID: 38538621 PMCID: PMC10973334 DOI: 10.1038/s41467-024-46810-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 03/08/2024] [Indexed: 04/04/2024] Open
Abstract
Mosquito-borne dengue (DENV) and Zika (ZIKV) viruses originated in Old World sylvatic (forest) cycles involving monkeys and canopy-living Aedes mosquitoes. Both viruses spilled over into human transmission and were translocated to the Americas, opening a path for spillback into Neotropical sylvatic cycles. Studies of the trade-offs that shape within-host dynamics and transmission of these viruses are lacking, hampering efforts to predict spillover and spillback. We infected a native, Asian host species (cynomolgus macaque) and a novel, American host species (squirrel monkey) with sylvatic strains of DENV-2 or ZIKV via mosquito bite. We then monitored aspects of viral replication (viremia), innate and adaptive immune response (natural killer (NK) cells and neutralizing antibodies, respectively), and transmission to mosquitoes. In both hosts, ZIKV reached high titers that translated into high transmission to mosquitoes; in contrast DENV-2 replicated to low levels and, unexpectedly, transmission occurred only when serum viremia was below or near the limit of detection. Our data reveal evidence of an immunologically-mediated trade-off between duration and magnitude of virus replication, as higher peak ZIKV titers are associated with shorter durations of viremia, and higher NK cell levels are associated with lower peak ZIKV titers and lower anti-DENV-2 antibody levels. Furthermore, patterns of transmission of each virus from a Neotropical monkey suggest that ZIKV has greater potential than DENV-2 to establish a sylvatic transmission cycle in the Americas.
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Affiliation(s)
- Kathryn A Hanley
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA.
| | - Hélène Cecilia
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Sasha R Azar
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Center for Tissue Engineering, Department of Surgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX, 77030, USA
| | - Brett A Moehn
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Jordan T Gass
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | | | - Wanqin Yu
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Ruimei Yun
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Benjamin M Althouse
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
- Information School, University of Washington, Seattle, WA, 98105, USA
| | - Nikos Vasilakis
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Shannan L Rossi
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX, 77555, USA
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, 77555, USA
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3
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Hanley KA, Cecilia H, Azar SR, Moehn B, Yu W, Yun R, Althouse BM, Vasilakis N, Rossi SL. Immunologically mediated trade-offs shaping transmission of sylvatic dengue and Zika viruses in native and novel non-human primate hosts. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.30.547187. [PMID: 37425901 PMCID: PMC10327119 DOI: 10.1101/2023.06.30.547187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Mosquito-borne dengue (DENV) and Zika (ZIKV) viruses originated in Old World sylvatic cycles involving monkey hosts, spilled over into human transmission, and were translocated to the Americas, creating potential for spillback into neotropical sylvatic cycles. Studies of the trade-offs that shape within-host dynamics and transmission of these viruses are lacking, hampering efforts to predict spillover and spillback. We exposed native (cynomolgus macaque) or novel (squirrel monkey) hosts to mosquitoes infected with either sylvatic DENV or ZIKV and monitored viremia, natural killer cells, transmission to mosquitoes, cytokines, and neutralizing antibody titers. Unexpectedly, DENV transmission from both host species occurred only when serum viremia was undetectable or near the limit of detection. ZIKV replicated in squirrel monkeys to much higher titers than DENV and was transmitted more efficiently but stimulated lower neutralizing antibody titers. Increasing ZIKV viremia led to greater instantaneous transmission and shorter duration of infection, consistent with a replication-clearance trade-off.
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Affiliation(s)
- Kathryn A Hanley
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003 USA
| | - Hélène Cecilia
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003 USA
| | - Sasha R Azar
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Center for Tissue Engineering, Department of Surgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX 77030 USA
| | - Brett Moehn
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003 USA
| | - Wanqin Yu
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003 USA
| | - Ruimei Yun
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555 USA
| | - Benjamin M Althouse
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003 USA
- Information School, University of Washington, Seattle, WA, 98105
| | - Nikos Vasilakis
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX, 77555 USA
| | - Shannan L Rossi
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, 77555 USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX, 77555 USA
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4
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Xu Z, Wei D, Zeng Q, Zhang H, Sun Y, Demongeot J. More or less deadly? A mathematical model that predicts SARS-CoV-2 evolutionary direction. Comput Biol Med 2023; 153:106510. [PMID: 36630829 PMCID: PMC9816089 DOI: 10.1016/j.compbiomed.2022.106510] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 12/18/2022] [Accepted: 12/31/2022] [Indexed: 01/09/2023]
Abstract
SARS-CoV-2 has caused tremendous deaths globally. It is of great value to predict the evolutionary direction of SARS-CoV-2. In this paper, we proposed a novel mathematical model that could predict the evolutionary trend of SARS-CoV-2. We focus on the mutational effects on viral assembly capacity. A robust coarse-grained mathematical model is constructed to simulate the virus dynamics in the host body. Both virulence and transmissibility can be quantified in this model. A delicate equilibrium point that optimizes the transmissibility can be numerically obtained. Based on this model, the virulence of SARS-CoV-2 might further decrease, accompanied by an enhancement of transmissibility. However, this trend is not continuous; its virulence will not disappear but remains at a relatively stable range. A virus assembly model which simulates the virus packing process is also proposed. It can be explained why a few mutations would lead to a significant divergence in clinical performance, both in the overall particle formation quantity and virulence. This research provides a novel mathematical attempt to elucidate the evolutionary driving force in RNA virus evolution.
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Affiliation(s)
- Zhaobin Xu
- Department of Life Science, Dezhou University, Dezhou, 253023, China.
| | - Dongqing Wei
- School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200030, China
| | - Qiangcheng Zeng
- Department of Life Science, Dezhou University, Dezhou, 253023, China
| | - Hongmei Zhang
- Department of Life Science, Dezhou University, Dezhou, 253023, China
| | - Yinghui Sun
- Department of Life Science, Dezhou University, Dezhou, 253023, China
| | - Jacques Demongeot
- Laboratory AGEIS EA 7407, Team Tools for e-Gnosis Medical, Faculty of Medicine, University Grenoble Alpes (UGA), 38700, La Tronche, France.
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5
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Evolutionary consequences of vector-borne transmission: how using vectors shapes host, vector and pathogen evolution. Parasitology 2022; 149:1667-1678. [PMID: 36200511 PMCID: PMC10090782 DOI: 10.1017/s0031182022001378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transmission mode is a key factor that influences host–parasite coevolution. Vector-borne pathogens are among the most important disease agents for humans and wildlife due to their broad distribution, high diversity, prevalence and lethality. They comprise some of the most important and widespread human pathogens, such as yellow fever, leishmania and malaria. Vector-borne parasites (in this review, those transmitted by blood-feeding Diptera) follow unique transmission routes towards their vertebrate hosts. Consequently, each part of this tri-partite (i.e. parasite, vector and host) interaction can influence co- and counter-evolutionary pressures among antagonists. This mode of transmission may favour the evolution of greater virulence to the vertebrate host; however, pathogen–vector interactions can also have a broad spectrum of fitness costs to the insect vector. To complete their life cycle, vector-borne pathogens must overcome immune responses from 2 unrelated organisms, since they can activate responses in both vertebrate and invertebrate hosts, possibly creating a trade-off between investments against both types of immunity. Here, we assess how dipteran vector-borne transmission shapes the evolution of hosts, vectors and the pathogens themselves. Hosts, vectors and pathogens co-evolve together in a constant antagonistic arms race with each participant's primary goal being to maximize its performance and fitness.
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6
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Drew GC, Stevens EJ, King KC. Microbial evolution and transitions along the parasite-mutualist continuum. Nat Rev Microbiol 2021; 19:623-638. [PMID: 33875863 PMCID: PMC8054256 DOI: 10.1038/s41579-021-00550-7] [Citation(s) in RCA: 105] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2021] [Indexed: 12/28/2022]
Abstract
Virtually all plants and animals, including humans, are home to symbiotic microorganisms. Symbiotic interactions can be neutral, harmful or have beneficial effects on the host organism. However, growing evidence suggests that microbial symbionts can evolve rapidly, resulting in drastic transitions along the parasite-mutualist continuum. In this Review, we integrate theoretical and empirical findings to discuss the mechanisms underpinning these evolutionary shifts, as well as the ecological drivers and why some host-microorganism interactions may be stuck at the end of the continuum. In addition to having biomedical consequences, understanding the dynamic life of microorganisms reveals how symbioses can shape an organism's biology and the entire community, particularly in a changing world.
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Affiliation(s)
| | | | - Kayla C King
- Department of Zoology, University of Oxford, Oxford, UK.
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7
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Larsen T, Jefferson C, Bartley A, Strassmann JE, Queller DC. Inference of symbiotic adaptations in nature using experimental evolution. Evolution 2021; 75:945-955. [PMID: 33590884 DOI: 10.1111/evo.14193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 01/30/2021] [Indexed: 11/27/2022]
Abstract
Microbes must adapt to the presence of other species, but it can be difficult to recreate the natural context for these interactions in the laboratory. We describe a method for inferring the existence of symbiotic adaptations by experimentally evolving microbes that would normally interact in an artificial environment without access to other species. By looking for changes in the fitness effects microbes adapted to isolation have on their partners, we can infer the existence of ancestral adaptations that were lost during experimental evolution. The direction and magnitude of trait changes can offer useful insight as to whether the microbes have historically been selected to help or harm one another in nature. We apply our method to the complex symbiosis between the social amoeba Dictyostelium discoideum and two intracellular bacterial endosymbionts, Paraburkholderia agricolaris and Paraburkholderia hayleyella. Our results suggest P. hayleyella-but not P. agricolaris-has generally been selected to attenuate its virulence in nature, and that D. discoideum has evolved to antagonistically limit the growth of Paraburkholderia. The approach demonstrated here can be a powerful tool for studying adaptations in microbes, particularly when the specific natural context in which the adaptations evolved is unknown or hard to reproduce.
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Affiliation(s)
- Tyler Larsen
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, 63130
| | - Cara Jefferson
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, 63130
| | - Anthony Bartley
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, 63130
| | - Joan E Strassmann
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, 63130
| | - David C Queller
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, 63130
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8
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Hill T, Unckless RL. Recurrent evolution of high virulence in isolated populations of a DNA virus. eLife 2020; 9:e58931. [PMID: 33112738 PMCID: PMC7685711 DOI: 10.7554/elife.58931] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 10/28/2020] [Indexed: 12/30/2022] Open
Abstract
Hosts and viruses are constantly evolving in response to each other: as a host attempts to suppress a virus, the virus attempts to evade and suppress the host's immune system. Here, we describe the recurrent evolution of a virulent strain of a DNA virus, which infects multiple Drosophila species. Specifically, we identified two distinct viral types that differ 100-fold in viral titer in infected individuals, with similar differences observed in multiple species. Our analysis suggests that one of the viral types recurrently evolved at least four times in the past ~30,000 years, three times in Arizona and once in another geographically distinct species. This recurrent evolution may be facilitated by an effective mutation rate which increases as each prior mutation increases viral titer and effective population size. The higher titer viral type suppresses the host-immune system and an increased virulence compared to the low viral titer type.
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Affiliation(s)
- Tom Hill
- The Department of Molecular Biosciences, University of KansasLawrenceUnited States
| | - Robert L Unckless
- The Department of Molecular Biosciences, University of KansasLawrenceUnited States
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9
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Kendig AE, Borer ET, Boak EN, Picard TC, Seabloom EW. Host nutrition mediates interactions between plant viruses, altering transmission and predicted disease spread. Ecology 2020; 101:e03155. [PMID: 32745231 DOI: 10.1002/ecy.3155] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 06/18/2020] [Indexed: 01/24/2023]
Abstract
Interactions among co-infecting pathogens are common across host taxa and can affect infectious disease dynamics. Host nutrition can mediate these among-pathogen interactions, altering the establishment and growth of pathogens within hosts. It is unclear, however, how nutrition-mediated among-pathogen interactions affect transmission and the spread of disease through populations. We manipulated the nitrogen (N) and phosphorus (P) supplies to oat plants in growth chambers and evaluated interactions between two aphid-vectored Barley and Cereal Yellow Dwarf Viruses: PAV and RPV. We quantified the effect of each virus on the other's establishment, within-plant density, and transmission. Co-inoculation significantly increased PAV density when N and P supplies were low and tended to increase RPV density when N supply was high. Co-infection increased PAV transmission when N and P supplies were low and tended to increase RPV transmission when N supply was high. Despite the parallels between the effects of among-pathogen interactions on density and transmission, changes in virus density only partially explained changes in transmission, suggesting that virus density-independent processes contribute to transmission. A mathematical model describing the spread of two viruses through a plant population, parameterized with empirically derived transmission values, demonstrated that nutrition-mediated among-pathogen interactions could affect disease spread. Interactions that altered transmission through virus density-independent processes determined overall disease dynamics. Our work suggests that host nutrition alters disease spread through among-pathogen interactions that modify transmission.
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Affiliation(s)
- Amy E Kendig
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA.,Agronomy Department, University of Florida, Gainesville, Florida, 32611, USA
| | - Elizabeth T Borer
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA
| | - Emily N Boak
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA.,Department of Horticultural Sciences, Texas A&M University, College Station, Texas, 77843, USA
| | - Tashina C Picard
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA
| | - Eric W Seabloom
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, 55108, USA
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10
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Costa G, Gildenhard M, Eldering M, Lindquist RL, Hauser AE, Sauerwein R, Goosmann C, Brinkmann V, Carrillo-Bustamante P, Levashina EA. Non-competitive resource exploitation within mosquito shapes within-host malaria infectivity and virulence. Nat Commun 2018; 9:3474. [PMID: 30150763 PMCID: PMC6110728 DOI: 10.1038/s41467-018-05893-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Accepted: 08/01/2018] [Indexed: 11/22/2022] Open
Abstract
Malaria is a fatal human parasitic disease transmitted by a mosquito vector. Although the evolution of within-host malaria virulence has been the focus of many theoretical and empirical studies, the vector’s contribution to this process is not well understood. Here, we explore how within-vector resource exploitation would impact the evolution of within-host Plasmodium virulence. By combining within-vector dynamics and malaria epidemiology, we develop a mathematical model, which predicts that non-competitive parasitic resource exploitation within-vector restricts within-host parasite virulence. To validate our model, we experimentally manipulate mosquito lipid trafficking and gauge within-vector parasite development and within-host infectivity and virulence. We find that mosquito-derived lipids determine within-host parasite virulence by shaping development (quantity) and metabolic activity (quality) of transmissible sporozoites. Our findings uncover the potential impact of within-vector environment and vector control strategies on the evolution of malaria virulence. The evolution of within-host malaria virulence has been studied, but the vector’s contribution isn’t well understood. Here, Costa et al. show that non-competitive parasitic resource exploitation within-vector, in particular lipid trafficking, restricts within-host infectivity and virulence of the parasite.
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Affiliation(s)
- G Costa
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - M Gildenhard
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - M Eldering
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany.,Department of Medical Microbiology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - R L Lindquist
- Immunodynamics, German Rheumatism Research Centre (DRFZ), 10117, Berlin, Germany
| | - A E Hauser
- Immunodynamics, German Rheumatism Research Centre (DRFZ), 10117, Berlin, Germany.,Immune Dynamics and Intravital Microscopy, Charité-Universitätsmedizin, 10117, Berlin, Germany
| | - R Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - C Goosmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - V Brinkmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - P Carrillo-Bustamante
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany
| | - E A Levashina
- Vector Biology Unit, Max Planck Institute for Infection Biology (MPIIB), 10117, Berlin, Germany.
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11
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Antonovics J. Transmission dynamics: critical questions and challenges. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0087. [PMID: 28289255 DOI: 10.1098/rstb.2016.0087] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2016] [Indexed: 11/12/2022] Open
Abstract
This article overviews the dynamics of disease transmission in one-host-one-parasite systems. Transmission is the result of interacting host and pathogen processes, encapsulated with the environment in a 'transmission triangle'. Multiple transmission modes and their epidemiological consequences are often not understood because the direct measurement of transmission is difficult. However, its different components can be analysed using nonlinear transmission functions, contact matrices and networks. A particular challenge is to develop such functions for spatially extended systems. This is illustrated for vector transmission where a 'perception kernel' approach is developed that incorporates vector behaviour in response to host spacing. A major challenge is understanding the relative merits of the large number of approaches to quantifying transmission. The evolution of transmission mode itself has been a rather neglected topic, but is important in the context of understanding disease emergence and genetic variation in pathogens. Disease impacts many biological processes such as community stability, the evolution of sex and speciation, yet the importance of different transmission modes in these processes is not understood. Broader approaches and ideas to disease transmission are important in the public health realm for combating newly emerging infections.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
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Affiliation(s)
- Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
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12
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Wilson AJ, Morgan ER, Booth M, Norman R, Perkins SE, Hauffe HC, Mideo N, Antonovics J, McCallum H, Fenton A. What is a vector? Philos Trans R Soc Lond B Biol Sci 2017; 372:20160085. [PMID: 28289253 PMCID: PMC5352812 DOI: 10.1098/rstb.2016.0085] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2016] [Indexed: 11/18/2022] Open
Abstract
Many important and rapidly emerging pathogens of humans, livestock and wildlife are 'vector-borne'. However, the term 'vector' has been applied to diverse agents in a broad range of epidemiological systems. In this perspective, we briefly review some common definitions, identify the strengths and weaknesses of each and consider the functional differences between vectors and other hosts from a range of ecological, evolutionary and public health perspectives. We then consider how the use of designations can afford insights into our understanding of epidemiological and evolutionary processes that are not otherwise apparent. We conclude that from a medical and veterinary perspective, a combination of the 'haematophagous arthropod' and 'mobility' definitions is most useful because it offers important insights into contact structure and control and emphasizes the opportunities for pathogen shifts among taxonomically similar species with similar feeding modes and internal environments. From a population dynamics and evolutionary perspective, we suggest that a combination of the 'micropredator' and 'sequential' definition is most appropriate because it captures the key aspects of transmission biology and fitness consequences for the pathogen and vector itself. However, we explicitly recognize that the value of a definition always depends on the research question under study.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'.
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Affiliation(s)
- Anthony James Wilson
- Vector-borne Viral Diseases Programme, The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, UK
| | - Eric René Morgan
- School of Veterinary Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Mark Booth
- School of Medicine, Pharmacy and Health, Durham University, Thornaby TS17 6BH, UK
| | - Rachel Norman
- School of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
| | - Sarah Elizabeth Perkins
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff CF10 3AX, UK
- Department of Biodiversity and Molecular Ecology, Centre for Research and Innovation, Fondazione Edmund Mach, Via E. Mach 1, 38010 S Michele all'Adige (TN), Italy
| | - Heidi Christine Hauffe
- Department of Biodiversity and Molecular Ecology, Centre for Research and Innovation, Fondazione Edmund Mach, Via E. Mach 1, 38010 S Michele all'Adige (TN), Italy
| | - Nicole Mideo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2
| | - Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Hamish McCallum
- Environmental Futures Research Institute, Griffith University, Nathan 4111, Queensland, Australia
| | - Andy Fenton
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
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13
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Dalmon A, Desbiez C, Coulon M, Thomasson M, Le Conte Y, Alaux C, Vallon J, Moury B. Evidence for positive selection and recombination hotspots in Deformed wing virus (DWV). Sci Rep 2017; 7:41045. [PMID: 28120868 PMCID: PMC5264398 DOI: 10.1038/srep41045] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 12/15/2016] [Indexed: 01/05/2023] Open
Abstract
Deformed wing virus (DWV) is considered one of the most damaging pests in honey bees since the spread of its vector, Varroa destructor. In this study, we sequenced the whole genomes of two virus isolates and studied the evolutionary forces that act on DWV genomes. The isolate from a Varroa-tolerant bee colony was characterized by three recombination breakpoints between DWV and the closely related Varroa destructor virus-1 (VDV-1), whereas the variant from the colony using conventional Varroa management was similar to the originally described DWV. From the complete sequence dataset, nine independent DWV-VDV-1 recombination breakpoints were detected, and recombination hotspots were found in the 5′ untranslated region (5′ UTR) and the conserved region encoding the helicase. Partial sequencing of the 5′ UTR and helicase-encoding region in 41 virus isolates suggested that most of the French isolates were recombinants. By applying different methods based on the ratio between non-synonymous (dN) and synonymous (dS) substitution rates, we identified four positions that showed evidence of positive selection. Three of these positions were in the putative leader protein (Lp), and one was in the polymerase. These findings raise the question of the putative role of the Lp in viral evolution.
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Affiliation(s)
- A Dalmon
- INRA, Unité Abeilles et Environnement, F-84000 Avignon, France.,UMT PRADE, F-84000 Avignon, France
| | - C Desbiez
- INRA, Unité Pathologie végétale, F-84000 Avignon, France
| | - M Coulon
- INRA, Unité Abeilles et Environnement, F-84000 Avignon, France.,ANSES, laboratoire de Sophia Antipolis, F-06902 Sophia Antipolis
| | - M Thomasson
- INRA, Unité Abeilles et Environnement, F-84000 Avignon, France
| | - Y Le Conte
- INRA, Unité Abeilles et Environnement, F-84000 Avignon, France.,UMT PRADE, F-84000 Avignon, France
| | - C Alaux
- INRA, Unité Abeilles et Environnement, F-84000 Avignon, France.,UMT PRADE, F-84000 Avignon, France
| | - J Vallon
- UMT PRADE, F-84000 Avignon, France
| | - B Moury
- INRA, Unité Pathologie végétale, F-84000 Avignon, France
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14
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Kribs-Zaleta CM. Graphical analysis of evolutionary trade-off in sylvatic Trypanosoma cruzi transmission modes. J Theor Biol 2014; 353:34-43. [DOI: 10.1016/j.jtbi.2014.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 02/25/2014] [Accepted: 03/04/2014] [Indexed: 11/28/2022]
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15
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Carter LM, Kafsack BF, Llinás M, Mideo N, Pollitt LC, Reece SE. Stress and sex in malaria parasites. EVOLUTION MEDICINE AND PUBLIC HEALTH 2013; 2013:135-47. [PMID: 24481194 PMCID: PMC3854026 DOI: 10.1093/emph/eot011] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
For vector-borne parasites such as malaria, how within- and between-host processes interact to shape transmission is poorly understood. In the host, malaria parasites replicate asexually but for transmission to occur, specialized sexual stages (gametocytes) must be produced. Despite the central role that gametocytes play in disease transmission, explanations of why parasites adjust gametocyte production in response to in-host factors remain controversial. We propose that evolutionary theory developed to explain variation in reproductive effort in multicellular organisms, provides a framework to understand gametocyte investment strategies. We examine why parasites adjust investment in gametocytes according to the impact of changing conditions on their in-host survival. We then outline experiments required to determine whether plasticity in gametocyte investment enables parasites to maintain fitness in a variable environment. Gametocytes are a target for anti-malarial transmission-blocking interventions so understanding plasticity in investment is central to maximizing the success of control measures in the face of parasite evolution.
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Affiliation(s)
- Lucy M. Carter
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
- *Corresponding author. Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, EH9 3JT, UK. Tel: +44 131 650 7706; Fax: +44 131 650 6564; E-mail:
| | - Björn F.C. Kafsack
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
| | - Manuel Llinás
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
| | - Nicole Mideo
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
| | - Laura C. Pollitt
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
| | - Sarah E. Reece
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK; Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA; Department of Molecular Biology, 246 Carl Icahn Lab, Washington Road, Princeton University, Princeton, NJ, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, Millennium Science Complex, University Park, PA, USA and Centre for Immunity, Infection & Evolution. Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK
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16
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Dances with worms: the ecological and evolutionary impacts of deworming on coinfecting pathogens. Parasitology 2013; 140:1119-32. [PMID: 23714427 PMCID: PMC3695730 DOI: 10.1017/s0031182013000590] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Parasitic helminths are ubiquitous in most host, including human, populations. Helminths
often alter the likelihood of infection and disease progression of coinfecting
microparasitic pathogens (viruses, bacteria, protozoa), and there is great interest in
incorporating deworming into control programmes for many major diseases (e.g. HIV,
tuberculosis, malaria). However, such calls are controversial; studies show the
consequences of deworming for the severity and spread of pathogens to be highly variable.
Hence, the benefits of deworming, although clear for reducing the morbidity due to
helminth infection per se, are unclear regarding the outcome of
coinfections and comorbidities. I develop a theoretical framework to explore how helminth
coinfection with other pathogens affects host mortality and pathogen spread and evolution
under different interspecific parasite interactions. In all cases the outcomes of
coinfection are highly context-dependent, depending on the mechanism of helminth-pathogen
interaction and the quantitative level of helminth infection, with the effects of
deworming potentially switching from beneficial to detrimental depending on helminth
burden. Such context-dependency may explain some of the variation in the benefits of
deworming seen between studies, and highlights the need for obtaining a quantitative
understanding of parasite interactions across realistic helminth infection ranges.
However, despite this complexity, this framework reveals predictable patterns in the
effects of helminths that may aid the development of more effective, integrated management
strategies to combat pathogens in this coinfected world.
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17
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Gjini E, Haydon DT, Barry JD, Cobbold CA. Linking the antigen archive structure to pathogen fitness in African trypanosomes. Proc Biol Sci 2013; 280:20122129. [PMID: 23282992 PMCID: PMC3574339 DOI: 10.1098/rspb.2012.2129] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 12/05/2012] [Indexed: 12/31/2022] Open
Abstract
Systems that generate antigenic variation enable pathogens to evade host immune responses and are intricately interwoven with major pathogen traits, such as host choice, growth, virulence and transmission. Although much is understood about antigen switching at the molecular level, little is known about the cross-scale links between these molecular processes and the larger-scale within and between host population dynamics that they must ultimately drive. Inspired by the antigenic variation system of African trypanosomes, we apply modelling approaches to our expanding understanding of the organization and expression of antigen repertoires, and explore links across these scales. We predict how pathogen population processes are determined by underlying molecular genetics and infer resulting selective pressures on important emergent repertoire traits.
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Affiliation(s)
- Erida Gjini
- School of Mathematics and Statistics, College of Science and Engineering, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK.
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18
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Kendal JR. Cultural Niche Construction and Human Learning Environments: Investigating Sociocultural Perspectives. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s13752-012-0038-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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19
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RÅBERG L. Infection intensity and infectivity of the tick-borne pathogen Borrelia afzelii. J Evol Biol 2012; 25:1448-53. [DOI: 10.1111/j.1420-9101.2012.02515.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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20
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Antonovics J, Boots M, Abbate J, Baker C, McFrederick Q, Panjeti V. Biology and evolution of sexual transmission. Ann N Y Acad Sci 2011; 1230:12-24. [PMID: 21824163 DOI: 10.1111/j.1749-6632.2011.06127.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sexual reproduction brings together and recombines different genomes. Associated with these contacts is transmission of microorganisms and selfish genetic elements, many of which can be harmful to the host. In organisms with internal fertilization, sexually transmitted infections are caused by pathogens transmitted between the parents participating in mating. Sexual transmission has different epidemiological dynamics from nonsexual transmission in that it is less likely to be dependent on host density, there may be no population density threshold for disease increase, and it is more likely to lead to host extinction. Analysis of the evolutionary pathways that have led to the sexual mode of transmission in pathogens indicates that sexual transmission appears more often to be derived from nonsexual transmission, although the pathways are highly variable, and several groups of pathogens are exceptions to this rule. Sexual transmission has evolved from a wide variety of alternative transmission modes, although rarely from aerially transmitted diseases. More data are needed on the phylogeny and transmission mode of the relatives of sexually transmitted pathogens in order to guide development of animal models and comparative studies.
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Affiliation(s)
- Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, Virginia 22903, USA.
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21
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Lafforgue G, Sardanyés J, Elena SF. Differences in accumulation and virulence determine the outcome of competition during Tobacco etch virus coinfection. PLoS One 2011; 6:e17917. [PMID: 21423618 PMCID: PMC3057992 DOI: 10.1371/journal.pone.0017917] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 02/15/2011] [Indexed: 11/18/2022] Open
Abstract
Understanding the evolution of virulence for RNA viruses is essential for developing appropriate control strategies. Although it has been usually assumed that virulence is a consequence of within-host replication of the parasite, viral strains may be highly virulent without experiencing large accumulation as a consequence of immunopathological host responses. Using two strains of Tobacco etch potyvirus (TEV) that show a negative relationship between virulence and accumulation rate, we first explored the evolution of virulence and fitness traits during simple and mixed infections. Short-term evolution experiments initiated with each strain independently confirmed the genetic and evolutionary stability of virulence and viral load, although infectivity significantly increased for both strains. Second, competition experiments between hypo- and hypervirulent TEV strains have shown that the outcome of competition is driven by differences in replication rate. A simple mathematical model has been developed to analyze the dynamics of these two strains during coinfection. The model qualitatively reproduced the experimental results using biologically meaningful parameters. Further analyses of the model also revealed a wide parametric region in which a low-fitness but hypovirulent virus can still outcompete a high-fitness but hypervirulent one. These results provide additional support to the observation that virulence and within-host replication may not necessarily be strongly tied in plant RNA viruses.
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Affiliation(s)
- Guillaume Lafforgue
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas – UPV, València, Spain
| | - Josep Sardanyés
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas – UPV, València, Spain
| | - Santiago F. Elena
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas – UPV, València, Spain
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
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22
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Staves PA, Knell RJ. Virulence and competitiveness: testing the relationship during inter- and intraspecific mixed infections. Evolution 2011; 64:2643-52. [PMID: 20394652 DOI: 10.1111/j.1558-5646.2010.00999.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the reasons why different parasites cause different degrees of harm to their hosts is an important objective in evolutionary biology. One group of models predicts that if hosts are infected with more than one strain or species of parasite, then competition between the parasites will select for higher virulence. While this idea makes intuitive sense, empirical data to support it are rare and equivocal. We investigated the relationship between fitness and virulence during both inter- and intraspecific competition for a fungal parasite of insects, Metarhizium anisopliae. Contrary to theoretical expectations, competition favored parasite strains with either a lower or a higher virulence depending on the competitor: when in interspecific competition with an entomopathogenic nematode, Steinernema feltiae, less virulent strains of the fungus were more successful, but when competing against conspecific fungi, more virulent strains were better competitors. We suggest that the nature of competition (direct via toxin production when competing against the nematode, indirect via exploitation of the host when competing against conspecific fungal strains) determines the relationship between virulence and competitive ability.
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Affiliation(s)
- Peter A Staves
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, United Kingdom.
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23
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Pollitt LC, Mideo N, Drew DR, Schneider P, Colegrave N, Reece SE. Competition and the Evolution of Reproductive Restraint in Malaria Parasites. Am Nat 2011; 177:358-67. [DOI: 10.1086/658175] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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24
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Froissart R, Doumayrou J, Vuillaume F, Alizon S, Michalakis Y. The virulence-transmission trade-off in vector-borne plant viruses: a review of (non-)existing studies. Philos Trans R Soc Lond B Biol Sci 2010; 365:1907-18. [PMID: 20478886 PMCID: PMC2880117 DOI: 10.1098/rstb.2010.0068] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The adaptive hypothesis invoked to explain why parasites harm their hosts is known as the trade-off hypothesis, which states that increased parasite transmission comes at the cost of shorter infection duration. This correlation arises because both transmission and disease-induced mortality (i.e. virulence) are increasing functions of parasite within-host density. There is, however, a glaring lack of empirical data to support this hypothesis. Here, we review empirical investigations reporting to what extent within-host viral accumulation determines the transmission rate and the virulence of vector-borne plant viruses. Studies suggest that the correlation between within-plant viral accumulation and transmission rate of natural isolates is positive. Unfortunately, results on the correlation between viral accumulation and virulence are very scarce. We found only very few appropriate studies testing such a correlation, themselves limited by the fact that they use symptoms as a proxy for virulence and are based on very few viral genotypes. Overall, the available evidence does not allow us to confirm or refute the existence of a transmission-virulence trade-off for vector-borne plant viruses. We discuss the type of data that should be collected and how theoretical models can help us refine testable predictions of virulence evolution.
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Affiliation(s)
- R Froissart
- Laboratoire Génétique & évolution des maladies infectieuses (GEMI), UMR 2724 CNRS IRD, 911 avenue Agropolis, 34394 Montpellier, France.
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25
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Arenas AJ, González-Parra G, Villanueva Micó RJ. Modeling toxoplasmosis spread in cat populations under vaccination. Theor Popul Biol 2010; 77:227-37. [PMID: 20304000 DOI: 10.1016/j.tpb.2010.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 07/16/2009] [Accepted: 03/03/2010] [Indexed: 11/28/2022]
Abstract
In this paper we present an epidemiological model to study the transmission dynamics of toxoplasmosis in a cat population under a continuous vaccination schedule. We explore the dynamics of toxoplasmosis at the population level using a mathematical model that includes the effect of oocyst, since the probability of acquisition of Toxoplasma Gondii infection depends on the environmental load of the parasite. This model considers indirectly the infection of prey through the oocyst shedding by cats. We prove that the basic reproduction number R(0) is a threshold value that completely determines the global dynamics and the outcome of the disease. Numerical computer simulations are presented to investigate different scenarios. These simulations show the effectiveness of a constant vaccination program.
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Affiliation(s)
- Abraham J Arenas
- Departamento de Matemáticas y Estadística, Universidad de Córdoba, Montería, Colombia
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26
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Alizon S, Hurford A, Mideo N, Van Baalen M. Virulence evolution and the trade-off hypothesis: history, current state of affairs and the future. J Evol Biol 2009; 22:245-59. [PMID: 19196383 DOI: 10.1111/j.1420-9101.2008.01658.x] [Citation(s) in RCA: 556] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
It has been more than two decades since the formulation of the so-called 'trade-off' hypothesis as an alternative to the then commonly accepted idea that parasites should always evolve towards avirulence (the 'avirulence hypothesis'). The trade-off hypothesis states that virulence is an unavoidable consequence of parasite transmission; however, since the 1990s, this hypothesis has been increasingly challenged. We discuss the history of the study of virulence evolution and the development of theories towards the trade-off hypothesis in order to illustrate the context of the debate. We investigate the arguments raised against the trade-off hypothesis and argue that trade-offs exist, but may not be of the simple form that is usually assumed, involving other mechanisms (and life-history traits) than those originally considered. Many processes such as pathogen adaptation to within-host competition, interactions with the immune system and shifting transmission routes, will all be interrelated making sweeping evolutionary predictions harder to obtain. We argue that this is the heart of the current debate in the field and while species-specific models may be better predictive tools, the trade-off hypothesis and its basic extensions are necessary to assess the qualitative impacts of virulence management strategies.
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Affiliation(s)
- S Alizon
- Department of Mathematics and Statistics, Queen's University, Kingston, Canada.
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27
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Reece SE, Ramiro RS, Nussey DH. Plastic parasites: sophisticated strategies for survival and reproduction? Evol Appl 2009; 2:11-23. [PMID: 20305703 PMCID: PMC2836026 DOI: 10.1111/j.1752-4571.2008.00060.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 11/26/2008] [Indexed: 11/28/2022] Open
Abstract
Adaptive phenotypic plasticity in life history traits, behaviours, and strategies is ubiquitous in biological systems. It is driven by variation in selection pressures across environmental gradients and operates under constraints imposed by trade-offs. Phenotypic plasticity has been thoroughly documented for multicellular taxa, such as insects, birds and mammals, and in many cases the underlying selective pressures are well understood. Whilst unicellular parasites face many of the same selective pressures and trade-offs, plasticity in their phenotypic traits has been largely overlooked and remains poorly understood. Here, we demonstrate that evolutionary theory, developed to explain variation observed in the life-history traits of multicellular organisms, can be applied to parasites. Though our message is general - we can expect the life-histories of all parasites to have evolved phenotypic plasticity - we focus our discussion on malaria parasites. We use an evolutionary framework to explain the trade-offs that parasites face and how plasticity in their life history traits will be expressed according to changes in their in-host environment. Testing whether variation in parasites traits is adaptive will provide new and fundamental insights into the basic biology of parasites, their epidemiology and the processes of disease during individual infections.
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28
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Alizon S, van Baalen M. Acute or chronic? Within-host models with immune dynamics, infection outcome, and parasite evolution. Am Nat 2009; 172:E244-56. [PMID: 18999939 DOI: 10.1086/592404] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
There is ample theoretical and experimental evidence that virulence evolution depends on the immune response of the host. In this article, we review a number of recent studies that attempt to explicitly incorporate the dynamics of the immune system (instead of merely representing it by a single black box parameter) in models for the evolution of parasite virulence. A striking observation is that the type of infection (acute or chronic) is invariably considered to be a constraint that model assumptions have to satisfy rather than as a potential outcome of the interaction of the parasite with its host's immune system. We argue that avoiding making assumptions about the type of infection will lead to a better understanding of infectious diseases, even though a number of fundamental and technical problems remain. Dynamical modeling of the immune system opens a wide range of perspectives: for understanding how the immune system eradicates a parasite (which it does for most pathogens but not for all, HIV being a notorious example of a virus that is not completely eliminated), for studying multiple infections through concomitant immunity, for understanding the emergence and evolution of the immune system in animals, and for evolutionary epidemiology in general (e.g., predicting evolutionary consequences of new therapies and public health policies). We conclude by discussing new approaches based on embedded (or nested) models and identify future perspectives for the modeling of infectious diseases.
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Affiliation(s)
- Samuel Alizon
- Ecole Normale Supérieure, Unité Mixte de Recherche 7625 Fonctionnement et Evolution des Systèmes Ecologiques, Paris F-75005, France.
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