1
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Hawley DM, Pérez-Umphrey AA, Adelman JS, Fleming-Davies AE, Garrett-Larsen J, Geary SJ, Childs LM, Langwig KE. Prior exposure to pathogens augments host heterogeneity in susceptibility and has key epidemiological consequences. PLoS Pathog 2024; 20:e1012092. [PMID: 39231171 DOI: 10.1371/journal.ppat.1012092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 08/19/2024] [Indexed: 09/06/2024] Open
Abstract
Pathogen epidemics are key threats to human and wildlife health. Across systems, host protection from pathogens following initial exposure is often incomplete, resulting in recurrent epidemics through partially-immune hosts. Variation in population-level protection has important consequences for epidemic dynamics, but how acquired protection influences inter-individual heterogeneity in susceptibility and its epidemiological consequences remains understudied. We experimentally investigated whether prior exposure (none, low-dose, or high-dose) to a bacterial pathogen alters host heterogeneity in susceptibility among songbirds. Hosts with no prior pathogen exposure had little variation in protection, but heterogeneity in susceptibility was significantly augmented by prior pathogen exposure, with the highest variability detected in hosts given high-dose prior exposure. An epidemiological model parameterized with experimental data found that heterogeneity in susceptibility from prior exposure more than halved epidemic sizes compared with a homogeneous population with identical mean protection. However, because infection-induced mortality was also greatly reduced in hosts with prior pathogen exposure, reductions in epidemic size were smaller than expected in hosts with prior exposure. These results highlight the importance of variable protection from prior exposure and/or vaccination in driving population-level heterogeneity and epidemiological dynamics.
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Affiliation(s)
- Dana M Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virgina, United States of America
| | - Anna A Pérez-Umphrey
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virgina, United States of America
| | - James S Adelman
- Department of Biological Sciences, University of Memphis, Memphis, Tennessee, United States of America
| | | | - Jesse Garrett-Larsen
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virgina, United States of America
| | - Steven J Geary
- Department of Pathobiology & Veterinary Science, University of Connecticut, Storrs, Connecticut, United States of America
| | - Lauren M Childs
- Department of Mathematics and Virginia Tech Center for the Mathematics of Biosystems, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Kate E Langwig
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virgina, United States of America
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2
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Hawley DM, Pérez-Umphrey AA, Adelman JS, Fleming-Davies AE, Garrett-Larsen J, Geary SJ, Childs LM, Langwig KE. Prior exposure to pathogens augments host heterogeneity in susceptibility and has key epidemiological consequences. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.05.583455. [PMID: 38496428 PMCID: PMC10942282 DOI: 10.1101/2024.03.05.583455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Pathogen epidemics are key threats to human and wildlife health. Across systems, host protection from pathogens following initial exposure is often incomplete, resulting in recurrent epidemics through partially-immune hosts. Variation in population-level protection has important consequences for epidemic dynamics, but how acquired protection influences inter-individual heterogeneity in susceptibility and its epidemiological consequences remains understudied. We experimentally investigated whether prior exposure (none, low-dose, or high-dose) to a bacterial pathogen alters host heterogeneity in susceptibility among songbirds. Hosts with no prior pathogen exposure had little variation in protection, but heterogeneity in susceptibility was significantly augmented by prior pathogen exposure, with the highest variability detected in hosts given high-dose prior exposure. An epidemiological model parameterized with experimental data found that heterogeneity in susceptibility from prior exposure more than halved epidemic sizes compared with a homogeneous population with identical mean protection. However, because infection-induced mortality was also greatly reduced in hosts with prior pathogen exposure, reductions in epidemic size were smaller than expected in hosts with prior exposure. These results highlight the importance of variable protection from prior exposure and/or vaccination in driving population-level heterogeneity and epidemiological dynamics.
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Affiliation(s)
- Dana M Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | | | - James S Adelman
- Department of Biological Sciences, University of Memphis, Memphis, TN, USA
| | | | | | - Steven J Geary
- Department of Pathobiology & Veterinary Science, University of Connecticut, Storrs, CT, USA
| | - Lauren M Childs
- Department of Mathematics and Virginia Tech Center for Mathematics of Biosystems, Virginia Tech, Blacksburg, VA, USA
| | - Kate E Langwig
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
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3
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Li S, Gulisija D, Carja O. The evolutionary cost of homophily: social stratification facilitates stable variant coexistence and increased rates of evolution in host-associated pathogens. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.14.603415. [PMID: 39071438 PMCID: PMC11275799 DOI: 10.1101/2024.07.14.603415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Coexistence of multiple strains of a pathogen in a host population can present significant challenges to vaccine development or treatment efficacy. Here we discuss a novel mechanism that can increase rates of long-lived strain polymorphism, rooted in the presence of social structure in a host population. We show that social preference of interaction, in conjunction with differences in immunity between host subgroups, can exert varying selection pressure on pathogen strains, creating a balancing mechanism that supports stable viral coexistence, independent of other known mechanisms. We use population genetic models to study rates of pathogen heterozygosity as a function of population size, host population composition, mutant strain fitness differences and host social preferences of interaction. We also show that even small periodic epochs of host population stratification can lead to elevated strain coexistence. These results are robust to varying social preferences of interaction, overall differences in strain fitnesses, and spatial heterogeneity in host population composition. Our results highlight the role of host population social stratification in increasing rates of pathogen strain diversity, with effects that should be considered when designing policies or treatments with a long-term view of curbing pathogen evolution.
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Affiliation(s)
- Shuanger Li
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA
- Current affiliation: Ecology and Evolution Graduate Program, University of Chicago, Chicago, USA
| | - Davorka Gulisija
- Department of Biology, University of New Mexico, Albuquerque, NM, USA
| | - Oana Carja
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA
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4
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Hoang KL, Read TD, King KC. Incomplete immunity in a natural animal-microbiota interaction selects for higher pathogen virulence. Curr Biol 2024; 34:1357-1363.e3. [PMID: 38430909 PMCID: PMC10962313 DOI: 10.1016/j.cub.2024.02.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 12/18/2023] [Accepted: 02/07/2024] [Indexed: 03/05/2024]
Abstract
Incomplete immunity in recovered hosts is predicted to favor more virulent pathogens upon re-infection in the population.1 The microbiota colonizing animals can generate a similarly long-lasting, partial immune response, allowing for infection but dampened disease severity.2 We tracked the evolutionary trajectories of a widespread pathogen (Pseudomonas aeruginosa), experimentally passaged through populations of nematodes immune-primed by a natural microbiota member (P. berkeleyensis). This bacterium can induce genes regulated by a mitogen-activated protein kinase (MAPK) signaling pathway effective at conferring protection against pathogen-induced death despite infection.3 Across host populations, this incomplete immunity selected for pathogens more than twice as likely to kill as those evolved in non-primed (i.e., naive) or immune-compromised (mutants with a knockout of the MAPK ortholog) control populations. Despite the higher virulence, pathogen molecular evolution in immune-primed hosts was slow and constrained. In comparison, evolving pathogens in immune-compromised hosts were characterized by substantial genomic differentiation and attenuated virulence. These findings directly attribute the incomplete host immunity induced from microbiota as a significant force shaping the virulence and evolutionary dynamics of novel infectious diseases.
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Affiliation(s)
- Kim L Hoang
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK; Division of Infectious Diseases, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA 30322, USA.
| | - Timothy D Read
- Division of Infectious Diseases, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA 30322, USA
| | - Kayla C King
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK; Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada; Department of Microbiology & Immunology, University of British Columbia, 1365 - 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
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5
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El Jarkass HT, Reinke AW. Pathogen evolution: Protective microbes act as a double-edged sword. Curr Biol 2024; 34:R247-R249. [PMID: 38531318 DOI: 10.1016/j.cub.2024.02.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Vaccines and infection can sometimes cause incomplete immunity, which allows for pathogen re-infection with decreased disease severity but also contributes to the evolution of pathogen virulence. A new study demonstrates that incomplete immunity from resident protective microbes results in similar evolutionary trajectories.
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Affiliation(s)
| | - Aaron W Reinke
- Department of Molecular Genetics, University of Toronto, Toronto ON M5G 1M1, Canada.
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6
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Kuttiyarthu Veetil N, Henschen AE, Hawley DM, Melepat B, Dalloul RA, Beneš V, Adelman JS, Vinkler M. Varying conjunctival immune response adaptations of house finch populations to a rapidly evolving bacterial pathogen. Front Immunol 2024; 15:1250818. [PMID: 38370402 PMCID: PMC10869556 DOI: 10.3389/fimmu.2024.1250818] [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: 01/11/2024] [Indexed: 02/20/2024] Open
Abstract
Pathogen adaptations during host-pathogen co-evolution can cause the host balance between immunity and immunopathology to rapidly shift. However, little is known in natural disease systems about the immunological pathways optimised through the trade-off between immunity and self-damage. The evolutionary interaction between the conjunctival bacterial infection Mycoplasma gallisepticum (MG) and its avian host, the house finch (Haemorhous mexicanus), can provide insights into such adaptations in immune regulation. Here we use experimental infections to reveal immune variation in conjunctival tissue for house finches captured from four distinct populations differing in the length of their co-evolutionary histories with MG and their disease tolerance (defined as disease severity per pathogen load) in controlled infection studies. To differentiate contributions of host versus pathogen evolution, we compared house finch responses to one of two MG isolates: the original VA1994 isolate and a more evolutionarily derived one, VA2013. To identify differential gene expression involved in initiation of the immune response to MG, we performed 3'-end transcriptomic sequencing (QuantSeq) of samples from the infection site, conjunctiva, collected 3-days post-infection. In response to MG, we observed an increase in general pro-inflammatory signalling, as well as T-cell activation and IL17 pathway differentiation, associated with a decrease in the IL12/IL23 pathway signalling. The immune response was stronger in response to the evolutionarily derived MG isolate compared to the original one, consistent with known increases in MG virulence over time. The host populations differed namely in pre-activation immune gene expression, suggesting population-specific adaptations. Compared to other populations, finches from Virginia, which have the longest co-evolutionary history with MG, showed significantly higher expression of anti-inflammatory genes and Th1 mediators. This may explain the evolution of disease tolerance to MG infection in VA birds. We also show a potential modulating role of BCL10, a positive B- and T-cell regulator activating the NFKB signalling. Our results illuminate potential mechanisms of house finch adaptation to MG-induced immunopathology, contributing to understanding of the host evolutionary responses to pathogen-driven shifts in immunity-immunopathology trade-offs.
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Affiliation(s)
| | - Amberleigh E. Henschen
- Department of Biological Sciences, The University of Memphis, Memphis, TN, United States
| | - Dana M. Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Balraj Melepat
- Department of Zoology, Charles University, Faculty of Science, Prague, Czechia
| | - Rami A. Dalloul
- Department of Poultry Science, The University of Georgia, Athens, GA, United States
| | - Vladimír Beneš
- European Molecular Biology Laboratory (EMBL), Genomics Core Facility, Heidelberg, Germany
| | - James S. Adelman
- Department of Biological Sciences, The University of Memphis, Memphis, TN, United States
| | - Michal Vinkler
- Department of Zoology, Charles University, Faculty of Science, Prague, Czechia
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7
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Somé BM, Guissou E, Da DF, Richard Q, Choisy M, Yameogo KB, Hien DF, Yerbanga RS, Ouedraogo GA, Dabiré KR, Djidjou-Demasse R, Cohuet A, Lefèvre T. Mosquito ageing modulates the development, virulence and transmission potential of pathogens. Proc Biol Sci 2024; 291:20232097. [PMID: 38166422 PMCID: PMC10762442 DOI: 10.1098/rspb.2023.2097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/27/2023] [Indexed: 01/04/2024] Open
Abstract
Host age variation is a striking source of heterogeneity that can shape the evolution and transmission dynamic of pathogens. Compared with vertebrate systems, our understanding of the impact of host age on invertebrate-pathogen interactions remains limited. We examined the influence of mosquito age on key life-history traits driving human malaria transmission. Females of Anopheles coluzzii, a major malaria vector, belonging to three age classes (4-, 8- and 12-day-old), were experimentally infected with Plasmodium falciparum field isolates. Our findings revealed reduced competence in 12-day-old mosquitoes, characterized by lower oocyst/sporozoite rates and intensities compared with younger mosquitoes. Despite shorter median longevities in older age classes, infected 12-day-old mosquitoes exhibited improved survival, suggesting that the infection might act as a fountain of youth for older mosquitoes specifically. The timing of sporozoite appearance in the salivary glands remained consistent across mosquito age classes, with an extrinsic incubation period of approximately 13 days. Integrating these results into an epidemiological model revealed a lower vectorial capacity for older mosquitoes compared with younger ones, albeit still substantial owing to extended longevity in the presence of infection. Considering age heterogeneity provides valuable insights for ecological and epidemiological studies, informing targeted control strategies to mitigate pathogen transmission.
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Affiliation(s)
- Bernard M. Somé
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
- Département de Biochimie, Université Nazi Boni, 01 BP 1091 Bobo Dioulasso, Burkina Faso
| | - Edwige Guissou
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
- Département de Biochimie, Université Nazi Boni, 01 BP 1091 Bobo Dioulasso, Burkina Faso
- MIVEGEC, IRD, CNRS, University of Montpellier, 34090 Montpellier cedex 5, France
- Ecole Normale Supérieure, BP 376 Koudougou, Burkina Faso
| | - Dari F. Da
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
| | - Quentin Richard
- IMAG, Université de Montpellier, CNRS, 34090 Montpellier, France
| | - Marc Choisy
- Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, 700000, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7BN, UK
| | - Koudraogo B. Yameogo
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Domombabele FdS. Hien
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Rakiswende S. Yerbanga
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Georges A. Ouedraogo
- Département de Biochimie, Université Nazi Boni, 01 BP 1091 Bobo Dioulasso, Burkina Faso
| | - Kounbobr R. Dabiré
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | | | - Anna Cohuet
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
- MIVEGEC, IRD, CNRS, University of Montpellier, 34090 Montpellier cedex 5, France
| | - Thierry Lefèvre
- Unité Paludisme et Maladies Tropicales Négligées, Institut de Recherche en Sciences de la Santé (IRSS), 01 BP 545 Bobo Dioulasso, Burkina Faso
- Laboratoire Mixte International sur les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
- MIVEGEC, IRD, CNRS, University of Montpellier, 34090 Montpellier cedex 5, France
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8
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Viney M, Cheynel L. Gut immune responses and evolution of the gut microbiome-a hypothesis. DISCOVERY IMMUNOLOGY 2023; 2:kyad025. [PMID: 38567055 PMCID: PMC10917216 DOI: 10.1093/discim/kyad025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 11/03/2023] [Accepted: 11/22/2023] [Indexed: 04/04/2024]
Abstract
The gut microbiome is an assemblage of microbes that have profound effects on their hosts. The composition of the microbiome is affected by bottom-up, among-taxa interactions and by top-down, host effects, which includes the host immune response. While the high-level composition of the microbiome is generally stable over time, component strains and genotypes will constantly be evolving, with both bottom-up and top-down effects acting as selection pressures, driving microbial evolution. Secretory IgA is a major feature of the gut's adaptive immune response, and a substantial proportion of gut bacteria are coated with IgA, though the effect of this on bacteria is unclear. Here we hypothesize that IgA binding to gut bacteria is a selection pressure that will drive the evolution of IgA-bound bacteria, so that they will have a different evolutionary trajectory than those bacteria not bound by IgA. We know very little about the microbiome of wild animals and even less about their gut immune responses, but it must be a priority to investigate this hypothesis to understand if and how host immune responses contribute to microbiome evolution.
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Affiliation(s)
- Mark Viney
- Department of Evolution, Ecology & Behaviour, University of Liverpool, Liverpool, UK
| | - Louise Cheynel
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, Villeurbanne, France
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9
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Langager MM, Adelman JS, Hawley DM. Let's stick together: Infection enhances preferences for social grouping in a songbird species. Ecol Evol 2023; 13:e10627. [PMID: 37841224 PMCID: PMC10576248 DOI: 10.1002/ece3.10627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/25/2023] [Accepted: 10/04/2023] [Indexed: 10/17/2023] Open
Abstract
Acute infections can alter foraging and movement behaviors relevant to sociality and pathogen spread. However, few studies have directly examined how acute infections caused by directly transmitted pathogens influence host social preferences. While infected hosts often express sickness behaviors (e.g., lethargy) that can reduce social associations with conspecifics, enhanced sociality during infection might be favored in some systems if social grouping improves host survival of infection. Directly assaying social preferences of infected hosts is needed to elucidate potential changes in social preferences that may act as a form of behavioral tolerance (defined as using behavior to minimize fitness costs of infection). We tested how infection alters sociality in juvenile house finches (Haemorhous mexicanus), which are both highly gregarious and particularly susceptible to infection by the bacterial pathogen Mycoplasma gallisepticum (MG). We inoculated 33 wild-caught but captive-held juvenile house finches with MG or media (sham control). At peak infection, birds were given a choice assay to assess preference for associating near a flock versus an empty cage. We then repeated this assay after all birds had recovered from infection. Infected birds were significantly more likely than controls to spend time associating with, and specifically foraging near, the flock. However, after infected birds had recovered from MG infection, there were no significant differences in the amount of time birds in each treatment spent with the flock. These results indicate augmented social preferences during active infection, potentially as a form of behavioral tolerance. Notably, infected birds showed strong social preferences regardless of variation in disease severity or pathogen loads, with 14/19 harboring high loads (5-6 log10 copies of MG) at the time of the assay. Overall, our results show that infection with a directly transmitted pathogen can augment social preferences, with important implications for MG spread in natural populations.
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Affiliation(s)
| | - James S. Adelman
- Department of Biological SciencesThe University of MemphisMemphisTennesseeUSA
| | - Dana M. Hawley
- Department of Biological SciencesVirginia TechBlacksburgVirginiaUSA
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10
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Tang R, Tan H, Dai Y, Li L, Huang Y, Yao H, Cai Y, Yu G. Application of antimicrobial peptides in plant protection: making use of the overlooked merits. FRONTIERS IN PLANT SCIENCE 2023; 14:1139539. [PMID: 37538059 PMCID: PMC10394246 DOI: 10.3389/fpls.2023.1139539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Accepted: 04/07/2023] [Indexed: 08/05/2023]
Abstract
Pathogen infection is one of the major causes of yield loss in the crop field. The rapid increase of antimicrobial resistance in plant pathogens has urged researchers to develop both new pesticides and management strategies for plant protection. The antimicrobial peptides (AMPs) showed potential on eliminating plant pathogenic fungi and bacteria. Here, we first summarize several overlooked advantages and merits of AMPs, which includes the steep dose-response relations, fast killing ability, broad synergism, slow resistance selection. We then discuss the possible application of AMPs for plant protection with above merits, and highlight how AMPs can be incorporated into a more efficient integrated management system that both increases the crop yield and reduce resistance evolution of pathogens.
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11
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Henschen AE, Vinkler M, Langager MM, Rowley AA, Dalloul RA, Hawley DM, Adelman JS. Rapid adaptation to a novel pathogen through disease tolerance in a wild songbird. PLoS Pathog 2023; 19:e1011408. [PMID: 37294834 DOI: 10.1371/journal.ppat.1011408] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 05/08/2023] [Indexed: 06/11/2023] Open
Abstract
Animal hosts can adapt to emerging infectious disease through both disease resistance, which decreases pathogen numbers, and disease tolerance, which limits damage during infection without limiting pathogen replication. Both resistance and tolerance mechanisms can drive pathogen transmission dynamics. However, it is not well understood how quickly host tolerance evolves in response to novel pathogens or what physiological mechanisms underlie this defense. Using natural populations of house finches (Haemorhous mexicanus) across the temporal invasion gradient of a recently emerged bacterial pathogen (Mycoplasma gallisepticum), we find rapid evolution of tolerance (<25 years). In particular, populations with a longer history of MG endemism have less pathology but similar pathogen loads compared with populations with a shorter history of MG endemism. Further, gene expression data reveal that more-targeted immune responses early in infection are associated with tolerance. These results suggest an important role for tolerance in host adaptation to emerging infectious diseases, a phenomenon with broad implications for pathogen spread and evolution.
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Affiliation(s)
- Amberleigh E Henschen
- Department of Biological Sciences, University of Memphis; Memphis, Tennessee, United States of America
- Department of Natural Resource Ecology and Management, Iowa State University; Ames, Iowa, United States of America
| | - Michal Vinkler
- Department of Zoology, Charles University; Prague, Czech Republic
| | - Marissa M Langager
- Department of Biological Sciences, Virginia Tech; Blacksburg, Virginia, United States of America
| | - Allison A Rowley
- Department of Biological Sciences, Virginia Tech; Blacksburg, Virginia, United States of America
| | - Rami A Dalloul
- Department of Poultry Science, University of Georgia; Athens, Georgia, United States of America
| | - Dana M Hawley
- Department of Biological Sciences, Virginia Tech; Blacksburg, Virginia, United States of America
| | - James S Adelman
- Department of Biological Sciences, University of Memphis; Memphis, Tennessee, United States of America
- Department of Natural Resource Ecology and Management, Iowa State University; Ames, Iowa, United States of America
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12
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Kennedy DA. Death is overrated: the potential role of detection in driving virulence evolution. Proc Biol Sci 2023; 290:20230117. [PMID: 36987649 PMCID: PMC10050922 DOI: 10.1098/rspb.2023.0117] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
A common assumption in the evolution of virulence theory literature is that pathogens transmit better when they exploit their host more heavily, but by doing so, they impose a greater risk of killing their host, thus truncating infectious periods and reducing their own opportunities for transmission. Here, I derive an equation for the magnitude of this cost in terms of the infection fatality rate, and in doing so, I show that there are many cases where mortality costs are too small to plausibly constrain increases in host exploitation by pathogens. I propose that pathogen evolution may often be constrained by detection costs, whereby hosts alter their behaviour when infection is detectable, and thus reduce pathogen opportunities for onward transmission. I then derive an inequality to illustrate when mortality costs or detection costs impose stronger constraints on pathogen evolution, and I use empirical data from the literature to demonstrate that detection costs are frequently large in both human and animal populations. Finally, I give examples of how evolutionary predictions can change depending on whether costs of host exploitation are borne out through mortality or detection.
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Affiliation(s)
- David A. Kennedy
- Department of Biology, Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, USA
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13
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Reinoso-Pérez MT, Dhondt KV, Levitskiy AA, Dupont G, Tulman ER, Geary SJ, Dhondt AA. Are Purple Finches (Haemorhous purpureus) the Next Host for a Mycoplasmal Conjunctivitis Epidemic? Avian Dis 2023; 67:42-48. [PMID: 37140110 DOI: 10.1637/aviandiseases-d-22-00047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 01/04/2023] [Indexed: 03/17/2023]
Abstract
Ever since 1994, when the bacterial pathogen Mycoplasma gallisepticum jumped from poultry to wild birds, it has been assumed that the primary host species of this pathogen in wild North American birds was the house finch (Haemorhous mexicanus), in which disease prevalence was higher than in any other bird species. Here we tested two hypotheses to explain a recent increase in disease prevalence in purple finches (Haemorhous purpureus) around Ithaca, New York. Hypothesis 1 is that, as M. gallisepticum evolved and became more virulent, it has also become better adapted to other finches. If this is correct, early isolates of M. gallisepticum should cause less-severe eye lesions in purple finches than in house finches, while more-recent isolates should cause eye lesions of similar severity in the two species. Hypothesis 2 is that, as house finch abundance declined following the M. gallisepticum epidemic, purple finches around Ithaca increased in abundance relative to house finches and purple finches are thus more frequently exposed to M. gallisepticum-infected house finches. This would then lead to an increase in M. gallisepticum prevalence in purple finches. Following an experimental infection with an early and a more-recent M. gallisepticum isolate, eye lesions in purple finches were more severe than in house finches. This did not a support Hypothesis 1; similarly, an analysis of Project Feeder Watch data collected around Ithaca did not show differences in changes in purple and house finches' abundance since 2006, a result which does not support Hypothesis 2. We conclude that purple finch populations will, unlike those of house finches, not suffer a severe decline because of a M. gallisepticum epidemic.
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Affiliation(s)
| | - Keila V. Dhondt
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
| | | | - Gates Dupont
- Department of Ecology and Evolution, Princeton University Princeton NJ 08544
| | - Edan R. Tulman
- Center of Excellence for Vaccine Research, Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CN 06269
| | - Steven J. Geary
- Center of Excellence for Vaccine Research, Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CN 06269
| | - André A. Dhondt
- Laboratory of Ornithology, Cornell University, Ithaca, NY 14850
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14
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Langwig KE, Kilpatrick AM, Kailing MJ, Laggan NA, White JP, Kaarakka HM, Redell JA, DePue JE, Parise KL, Foster JT, Hoyt JR. Shifting effects of host physiological condition following pathogen establishment. Biol Lett 2023; 19:20220574. [PMID: 36855852 PMCID: PMC9975657 DOI: 10.1098/rsbl.2022.0574] [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: 12/01/2022] [Accepted: 02/14/2023] [Indexed: 03/02/2023] Open
Abstract
Understanding host persistence with emerging pathogens is essential for conserving populations. Hosts may initially survive pathogen invasions through pre-adaptive mechanisms. However, whether pre-adaptive traits are directionally selected to increase in frequency depends on the heritability and environmental dependence of the trait and the costs of trait maintenance. Body condition is likely an important pre-adaptive mechanism aiding in host survival, although can be seasonally variable in wildlife hosts. We used data collected over 7 years on bat body mass, infection and survival to determine the role of host body condition during the invasion and establishment of the emerging disease, white-nose syndrome. We found that when the pathogen first invaded, bats with higher body mass were more likely to survive, but this effect dissipated following the initial epizootic. We also found that heavier bats lost more weight overwinter, but fat loss depended on infection severity. Lastly, we found mixed support that bat mass increased in the population after pathogen arrival; high annual plasticity in individual bat masses may have reduced the potential for directional selection. Overall, our results suggest that some factors that contribute to host survival during pathogen invasion may diminish over time and are potentially replaced by other host adaptations.
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Affiliation(s)
- Kate E. Langwig
- Department of Biological Sciences, Virginia Polytechnic Institute, Blacksburg, VA 24061, USA
| | - A. Marm Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA
| | - Macy J. Kailing
- Department of Biological Sciences, Virginia Polytechnic Institute, Blacksburg, VA 24061, USA
| | - Nichole A. Laggan
- Department of Biological Sciences, Virginia Polytechnic Institute, Blacksburg, VA 24061, USA
| | - J. Paul White
- Wisconsin Department of Natural Resources, Madison, WI 53707, USA
| | | | | | - John E. DePue
- Michigan Department of Natural Resources, Baraga, MI 49908, USA
| | - Katy L. Parise
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Jeffrey T. Foster
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Joseph R. Hoyt
- Department of Biological Sciences, Virginia Polytechnic Institute, Blacksburg, VA 24061, USA
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15
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Metcalf R, White HL, Ormsby MJ, Oliver DM, Quilliam RS. From wastewater discharge to the beach: Survival of human pathogens bound to microplastics during transfer through the freshwater-marine continuum. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 319:120955. [PMID: 36581243 DOI: 10.1016/j.envpol.2022.120955] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/05/2022] [Accepted: 12/24/2022] [Indexed: 06/17/2023]
Abstract
Large quantities of microplastics are regularly discharged from wastewater treatment plants (WWTPs) into the aquatic environment. Once released, these plastics can rapidly become colonised by microbial biofilm, forming distinct plastisphere communities which may include potential pathogens. We hypothesised that the protective environment afforded by the plastisphere would facilitate the survival of potential pathogens during transitions between downstream environmental matrices and thus increase persistence and the potential for environmental dissemination of pathogens. The survival of Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa colonising polyethylene or glass particles has been quantified in mesocosm incubation experiments designed to simulate, (1) the direct release of microplastics from WWTPs into freshwater and seawater environments; and (2) the movement of microplastics downstream following discharge from the WWTP through the river-estuary-marine-beach continuum. Culturable E. coli, E. faecalis and P. aeruginosa were successfully able to survive and persist on particles whether they remained in one environmental matrix or transitioned between different environmental matrices. All three bacteria were still detectable on both microplastic and glass particles after 25 days, with higher concentrations on microplastic compared to glass particles; however, there were no differences in bacterial die-off rates between the two materials. This potential for environmental survival of pathogens in the plastisphere could facilitate their transition into places where human exposure is greater (e.g., bathing waters and beach environments). Therefore, risks associated with pathogen-microplastic co-pollutants in the environment, emphasises the urgency for updated regulations on wastewater discharge and the management of microplastic generation and release.
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Affiliation(s)
- Rebecca Metcalf
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK.
| | - Hannah L White
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Michael J Ormsby
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - David M Oliver
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Richard S Quilliam
- Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
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16
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Hawley DM, Thomason CA, Aberle MA, Brown R, Adelman JS. High virulence is associated with pathogen spreadability in a songbird-bacterial system. ROYAL SOCIETY OPEN SCIENCE 2023; 10:220975. [PMID: 36686556 PMCID: PMC9832288 DOI: 10.1098/rsos.220975] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 12/19/2022] [Indexed: 06/11/2023]
Abstract
How directly transmitted pathogens benefit from harming hosts is key to understanding virulence evolution. It is recognized that pathogens benefit from high within-host loads, often associated with virulence. However, high virulence may also directly augment spread of a given amount of pathogen, here termed 'spreadability'. We used house finches and the conjunctival pathogen Mycoplasma gallisepticum to test whether two components of virulence-the severity of conjunctival inflammation and behavioural morbidity produced-predict pathogen spreadability. We applied ultraviolet powder around the conjunctiva of finches that were inoculated with pathogen treatments of distinct virulence and measured within-flock powder spread, our proxy for 'spreadability'. When compared to uninfected controls, birds infected with a high-virulence, but not low-virulence, pathogen strain, spread significantly more powder to flockmates. Relative to controls, high-virulence treatment birds both had more severe conjunctival inflammation-which potentially facilitated powder shedding-and longer bouts on feeders, which serve as fomites. However, food peck rates and displacements with flockmates were lowest in high-virulence treatment birds relative to controls, suggesting inflammatory rather than behavioural mechanisms likely drive augmented spreadability at high virulence. Our results suggest that inflammation associated with virulence can facilitate pathogen spread to conspecifics, potentially favouring virulence evolution in this system and others.
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Affiliation(s)
- Dana M. Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0131, USA
| | - Courtney A. Thomason
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0131, USA
| | - Matt A. Aberle
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0131, USA
| | - Richard Brown
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061-0131, USA
| | - James S. Adelman
- Department of Biological Sciences, The University of Memphis, Memphis, TN 38152, USA
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17
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Virulence evolution during a naturally occurring parasite outbreak. Evol Ecol 2023; 37:113-129. [PMID: 35431396 PMCID: PMC9002213 DOI: 10.1007/s10682-022-10169-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 02/27/2022] [Accepted: 03/03/2022] [Indexed: 11/22/2022]
Abstract
Virulence, the degree to which a pathogen harms its host, is an important but poorly understood aspect of host-pathogen interactions. Virulence is not static, instead depending on ecological context and potentially evolving rapidly. For instance, at the start of an epidemic, when susceptible hosts are plentiful, pathogens may evolve increased virulence if this maximizes their intrinsic growth rate. However, if host density declines during an epidemic, theory predicts evolution of reduced virulence. Although well-studied theoretically, there is still little empirical evidence for virulence evolution in epidemics, especially in natural settings with native host and pathogen species. Here, we used a combination of field observations and lab assays in the Daphnia-Pasteuria model system to look for evidence of virulence evolution in nature. We monitored a large, naturally occurring outbreak of Pasteuria ramosa in Daphnia dentifera, where infection prevalence peaked at ~ 40% of the population infected and host density declined precipitously during the outbreak. In controlled infections in the lab, lifespan and reproduction of infected hosts was lower than that of unexposed control hosts and of hosts that were exposed but not infected. We did not detect any significant changes in host resistance or parasite infectivity, nor did we find evidence for shifts in parasite virulence (quantified by host lifespan and number of clutches produced by hosts). However, over the epidemic, the parasite evolved to produce significantly fewer spores in infected hosts. While this finding was unexpected, it might reflect previously quantified tradeoffs: parasites in high mortality (e.g., high predation) environments shift from vegetative growth to spore production sooner in infections, reducing spore yield. Future studies that track evolution of parasite spore yield in more populations, and that link those changes with genetic changes and with predation rates, will yield better insight into the drivers of parasite evolution in the wild. Supplementary Information The online version contains supplementary material available at 10.1007/s10682-022-10169-6.
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18
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CHANGES IN TISSUE TROPISM OF MYCOPLASMA GALLISEPTICUM FOLLOWING HOST JUMP. J Wildl Dis 2022; 58:716-724. [PMID: 36302353 DOI: 10.7589/jwd-d-21-00187] [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: 11/23/2021] [Accepted: 07/01/2022] [Indexed: 12/05/2022]
Abstract
Mycoplasma gallisepticum, a pathogen of worldwide economic importance in poultry, is recovered in chickens, especially from the respiratory tract. Some strains, however, are specialized to other tissues and because it jumps from poultry to wild birds, the new strains also cause severe conjunctivitis in new hosts. Nevertheless, most studies of M. gallisepticum in wild birds use choanal swabs or combine choanal and conjunctival swabs to quantify bacterial load. Because the clinical signs associated with M. gallisepticum infection differ markedly between poultry and House Finches (Haemorhous mexicanus), we compared the bacterial load in choanal and conjunctival samples following experimental inoculation of House Finches with M. gallisepticum isolates originating from poultry or from House Finches. This allowed us to test two hypotheses: M. gallisepticum changed tissue tropism, or M. gallisepticum simply expanded its within-host niche. By comparing bacterial loads from choanal and conjunctival swabs in birds inoculated with one of a suite of M. gallisepticum isolates, we found support for hypothesis 2. The choanal loads in House Finches did not differ between isolates, while the conjunctival loads of birds inoculated with poultry isolates were lower than in birds inoculated with House Finch isolates. When measuring the bacterial load of M. gallisepticum in birds, it is important to sample and analyze separately choanal and conjunctival swabs, as quantifying bacterial loads in pooled samples may not provide reliable information on differences in virulence.
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19
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Bull JJ, Antia R. Which 'imperfect vaccines' encourage the evolution of higher virulence? Evol Med Public Health 2022; 10:202-213. [PMID: 35539897 PMCID: PMC9081871 DOI: 10.1093/emph/eoac015] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 04/06/2022] [Indexed: 12/27/2022] Open
Abstract
Background and objectives Theory suggests that some types of vaccines against infectious pathogens may lead to the evolution of variants that cause increased harm, particularly when they infect unvaccinated individuals. This theory was supported by the observation that the use of an imperfect vaccine to control Marek's disease virus in chickens resulted in the virus evolving to be more lethal to unvaccinated birds. This raises the concern that the use of some other vaccines may lead to similar pernicious outcomes. We examine that theory with a focus on considering the regimes in which such outcomes are expected. Methodology We evaluate the plausibility of assumptions in the original theory. The previous theory rested heavily on a particular form of transmission-mortality-recovery trade-off and invoked other assumptions about the pathways of evolution. We review alternatives to mortality in limiting transmission and consider evolutionary pathways that were omitted in the original theory. Results The regime where the pernicious evolutionary outcome occurs is narrowed by our analysis but remains possible in various scenarios. We propose a more nuanced consideration of alternative models for the within-host dynamics of infections and for factors that limit virulence. Our analysis suggests imperfect vaccines against many pathogens will not lead to the evolution of pathogens with increased virulence in unvaccinated individuals. Conclusions and implications Evolution of greater pathogen mortality driven by vaccination remains difficult to predict, but the scope for such outcomes appears limited. Incorporation of mechanistic details into the framework, especially regarding immunity, may be requisite for prediction accuracy. Lay Summary A virus of chickens appears to have evolved high mortality in response to a vaccine that merely prevented disease symptoms. Theory has predicted this type of evolution in response to a variety of vaccines and other interventions such as drug treatment. Under what circumstances is this pernicious result likely to occur? Analysis of the theory in light of recent changes in our understanding of viral biology raises doubts that medicine-driven, pernicious evolution is likely to be common. But we are far from a mechanistic understanding of the interaction between pathogen and host that can predict when vaccines and other medical interventions will lead to the unwanted evolution of more virulent pathogens. So, while the regime where a pernicious result obtains may be limited, caution remains warranted in designing many types of interventions.
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Affiliation(s)
- James J Bull
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051, USA
| | - Rustom Antia
- Department of Biology, Emory University, Atlanta, GA 30322, USA
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20
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Hoang KL, King KC. Symbiont-mediated immune priming in animals through an evolutionary lens. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35442184 DOI: 10.1099/mic.0.001181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Protective symbionts can defend hosts from parasites through several mechanisms, from direct interference to modulating host immunity, with subsequent effects on host and parasite fitness. While research on symbiont-mediated immune priming (SMIP) has focused on ecological impacts and agriculturally important organisms, the evolutionary implications of SMIP are less clear. Here, we review recent advances made in elucidating the ecological and molecular mechanisms by which SMIP occurs. We draw on current works to discuss the potential for this phenomenon to drive host, parasite, and symbiont evolution. We also suggest approaches that can be used to address questions regarding the impact of immune priming on host-microbe dynamics and population structures. Finally, due to the transient nature of some symbionts involved in SMIP, we discuss what it means to be a protective symbiont from ecological and evolutionary perspectives and how such interactions can affect long-term persistence of the symbiosis.
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Affiliation(s)
- Kim L Hoang
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
| | - Kayla C King
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
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21
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Weitzman CL, Ceja G, Leon AE, Hawley DM. Protection Generated by Prior Exposure to Pathogens Depends on both Priming and Challenge Dose. Infect Immun 2022; 90:e0053721. [PMID: 35041488 PMCID: PMC8929379 DOI: 10.1128/iai.00537-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 12/14/2021] [Indexed: 11/20/2022] Open
Abstract
Free-living hosts encounter pathogens at a wide range of frequencies and concentrations, including low doses that are largely aclinical, creating a varied landscape of exposure history and reinfection likelihood. While several studies show that higher priming doses result in stronger immunological protection against reinfection, it remains unknown how the reinfection challenge dose and priming dose interact to determine the likelihood and severity of reinfection. We manipulated both priming and challenge doses of Mycoplasma gallisepticum, which causes mycoplasmal conjunctivitis, in captive house finches (Haemorhous mexicanus), to assess reinfection probability and severity. We found a significant interaction between priming and challenge doses on reinfection probability, with the likelihood of reinfection by a high but not a low challenge dose decreasing exponentially at higher priming doses. While this interaction was likely driven by lower average infection probabilities for low-dose versus high-dose challenges, even the highest priming dose provided only negligible protection against reinfection from low-dose challenges. Similarly, pathogen loads during reinfection were significantly reduced with increasing priming doses only for birds reinfected at high but not low doses. We hypothesize that these interactions arise to some degree from fundamental differences in host immune responses across doses, with single low doses only weakly triggering host immune responses. Importantly, our results also demonstrate that reinfections can occur from a variety of exposure doses and across diverse degrees of standing immunity in this system. Overall, our study highlights the importance of considering both initial and subsequent exposure doses where repeated exposure to a pathogen is common in nature.
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Affiliation(s)
- Chava L. Weitzman
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Guadalupe Ceja
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Ariel E. Leon
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
| | - Dana M. Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, USA
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22
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Rovenolt FH, Tate AT. The Impact of Coinfection Dynamics on Host Competition and Coexistence. Am Nat 2022; 199:91-107. [DOI: 10.1086/717180] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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23
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Hochachka WM, Dobson AP, Hawley DM, Dhondt AA. Host population dynamics in the face of an evolving pathogen. J Anim Ecol 2021; 90:1480-1491. [PMID: 33821505 DOI: 10.1111/1365-2656.13469] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 02/19/2021] [Indexed: 11/28/2022]
Abstract
Interactions between hosts and pathogens are dynamic at both ecological and evolutionary levels. In the resultant 'eco-evolutionary dynamics' ecological and evolutionary processes affect each other. For example, the house finch Haemorhous mexicanus and its recently emerged pathogen, the bacterium Mycoplasma gallisepticum, form a system in which evidence suggests that changes in bacterial virulence through time enhance levels of host immunity in ways that drive the evolution of virulence in an arms race. We use data from two associated citizen science projects in order to determine whether this arms race has had any detectable effect at the population level in the north-eastern United States. We used data from two citizen science projects, based on observations of birds at bird feeders, which provide information on the long-term changes in sizes of aggregations of house finches (host population density), and the probabilities that these house finches have observable disease (disease prevalence). The initial emergence of M. gallisepticum caused a rapid halving of house finch densities; this was then followed by house finch populations remaining stable or slowly declining. Disease prevalence also decreased sharply after the initial emergence and has remained low, although with fluctuations through time. Surprisingly, while initially higher local disease prevalence was found at sites with higher local densities of finches, this relationship has reversed over time. The ability of a vertebrate host species, with a generation time of at least 1 year, to maintain stable populations in the face of evolved higher virulence of a bacterium, with generation times measurable in minutes, suggests that genetic changes in the host are insufficient to explain the observed population-level patterns. We suggest that acquired immunity plays an important role in the observed interaction between house finches and M. gallisepticum.
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Affiliation(s)
| | - Andrew P Dobson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Dana M Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
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24
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Barnett KM, Civitello DJ. Ecological and Evolutionary Challenges for Wildlife Vaccination. Trends Parasitol 2020; 36:970-978. [PMID: 32952060 PMCID: PMC7498468 DOI: 10.1016/j.pt.2020.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/23/2020] [Accepted: 08/24/2020] [Indexed: 12/13/2022]
Abstract
Wildlife vaccination is of urgent interest to reduce disease-induced extinction and zoonotic spillover events. However, several challenges complicate its application to wildlife. For example, vaccines rarely provide perfect immunity. While some protection may seem better than none, imperfect vaccination can present epidemiological, ecological, and evolutionary challenges. While anti-infection and antitransmission vaccines reduce parasite transmission, antidisease vaccines may undermine herd immunity, select for increased virulence, or promote spillover. These imperfections interact with ecological and logistical constraints that are magnified in wildlife, such as poor control and substantial trait variation within and among species. Ultimately, we recommend approaches such as trait-based vaccination, modeling tools, and methods to assess community- and ecosystem-level vaccine safety to address these concerns and bolster wildlife vaccination campaigns.
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Affiliation(s)
- K M Barnett
- Department of Biology, Emory University, Atlanta, GA 30322, USA.
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25
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Reinoso‐Pérez MT, Dhondt KV, Sydenstricker AV, Heylen D, Dhondt AA. Complex interactions between bacteria and haemosporidia in coinfected hosts: An experiment. Ecol Evol 2020; 10:5801-5814. [PMID: 32607191 PMCID: PMC7319152 DOI: 10.1002/ece3.6318] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/02/2020] [Accepted: 04/05/2020] [Indexed: 01/08/2023] Open
Abstract
Hosts are typically coinfected by multiple parasite species whose interactions might be synergetic or antagonistic, producing unpredictable physiological and pathological impacts on the host. This study shows the interaction between Plasmodium spp. and Leucocytozoon spp. in birds experimentally infected or not infected with Mycoplasma gallisepticum.In 1994, the bacterium Mycoplasma gallisepticum jumped from poultry to wild birds in which it caused a major epidemic in North America. Birds infected with M. gallisepticum show conjunctivitis as well as increased levels of corticosterone.Malaria and other haemosporidia are widespread in birds, and chronic infections become apparent with the detectable presence of the parasite in peripheral blood in response to elevated levels of natural or experimental corticosterone levels.Knowing the immunosuppressive effect of corticosterone on the avian immune system, we tested the hypothesis that chronic infections of Plasmodium spp. and Leucocytozoon spp. in house finches would respond to experimental inoculation with M. gallisepticum as corticosterone levels are known to increase following inoculation. Plasmodium spp. infection intensity increased within days of M. gallisepticum inoculation as shown both by the appearance of infected erythrocytes and by the increase in the number and the intensity of positive PCR tests. Leucocytozoon spp. infection intensity increased when Plasmodium spp. infection intensity increased, but not in response to M. gallisepticum inoculation. Leucocytozoon spp. and Plasmodium spp. seemed to compete in the host as shown by a negative correlation between the changes in their PCR score when both pathogens were present in the same individual.Host responses to coinfection with multiple pathogens measured by the hematocrit and white blood cell count depended on the haemosporidian community composition. Host investment in the leukocyte response was higher in the single-haemosporidia-infected groups when birds were infected with M. gallisepticum.A trade-off was observed between the immune control of the chronic infection (Plasmodium spp./Leucocytozoon spp.) and the immune response to the novel bacterial infection (M. gallisepticum).
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Affiliation(s)
- María Teresa Reinoso‐Pérez
- Department of Natural ResourcesCornell UniversityIthacaNew York
- Laboratory of OrnithologyCornell UniversityIthacaNew York
| | - Keila V. Dhondt
- Department of Microbiology and ImmunologyCollege of Veterinary MedicineCornell UniversityIthacaNew York
| | | | - Dieter Heylen
- Department of Ecology and Evolutionary BiologyPrinceton UniversityPrincetonNew Jersey
- Interuniversity Institute for Biostatistics and statistical BioinformaticsHasselt UniversityDiepenbeekBelgium
| | - André A. Dhondt
- Laboratory of OrnithologyCornell UniversityIthacaNew York
- Department of Ecology and Evolutionary BiologyCornell UniversityIthacaNew York
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26
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Bale NM, Leon AE, Hawley DM. Differential house finch leukocyte profiles during experimental infection with Mycoplasma gallisepticum isolates of varying virulence. Avian Pathol 2020; 49:342-354. [PMID: 32270701 DOI: 10.1080/03079457.2020.1753652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Leukocyte differentials are a useful tool for assessing systemic immunological changes during pathogen infections, particularly for non-model species. To date, no study has explored how experimental infection with a common bacterial pathogen, Mycoplasma gallisepticum (MG), influences the course and strength of haematological changes in the natural songbird host, house finches. Here we experimentally inoculated house finches with MG isolates known to vary in virulence, and quantified the proportions of circulating leukocytes over the entirety of infection. First, we found significant temporal effects of MG infection on the proportions of most cell types, with strong increases in heterophil and monocyte proportions during infection. Marked decreases in lymphocyte proportions also occurred during infection, though these proportional changes may simply be driven by correlated increases in other leukocytes. Second, we found significant effects of isolate virulence, with the strongest changes in cell proportions occurring in birds inoculated with the higher virulence isolates, and almost no detectable changes relative to sham treatment groups in birds inoculated with the lowest virulence isolate. Finally, we found that variation in infection severity positively predicted the proportion of circulating heterophils and lymphocytes, but the strength of these correlations was dependent on isolate. Taken together, these results indicate strong haematological changes in house finches during MG infection, with markedly different responses to MG isolates of varying virulence. These results are consistent with the possibility that evolved virulence in house finch MG results in higher degrees of immune stimulation and associated immunopathology, with potential direct benefits for MG transmission. RESEARCH HIGHLIGHTS House finches show a marked pro-inflammatory response to M. gallisepticum infection. Virulent pathogen isolates produce stronger finch white blood cell responses. Among birds, stronger white blood cell responses are associated with higher infection severity.
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Affiliation(s)
- Natalie M Bale
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Ariel E Leon
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Dana M Hawley
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
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27
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Henschen AE, Adelman JS. What Does Tolerance Mean for Animal Disease Dynamics When Pathology Enhances Transmission? Integr Comp Biol 2020; 59:1220-1230. [PMID: 31141137 DOI: 10.1093/icb/icz065] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Host competence, or how well an individual transmits pathogens, varies substantially within and among animal populations. As this variation can alter the course of epidemics and epizootics, revealing its underlying causes will help predict and control the spread of disease. One host trait that could drive heterogeneity in competence is host tolerance, which minimizes fitness losses during infection without decreasing pathogen load. In many cases, tolerance should increase competence by extending infectious periods and enabling behaviors that facilitate contact among hosts. However, we argue that the links between tolerance and competence are more varied. Specifically, the different physiological and behavioral mechanisms by which hosts achieve tolerance should have a range of effects on competence, enhancing the ability to transmit pathogens in some circumstances and impeding it in others. Because tissue-based pathology (damage) that reduces host fitness is often critical for pathogen transmission, we focus on two mechanisms that can underlie tolerance at the tissue level: damage-avoidance and damage-repair. As damage-avoidance reduces transmission-enhancing pathology, this mechanism is likely to decrease host competence and pathogen transmission. In contrast, damage-repair does not prevent transmission-relevant pathology from occurring. Rather, damage-repair provides new, healthy tissues that pathogens can exploit, likely extending the infectious period and increasing host competence. We explore these concepts through graphical models and present three disease systems in which damage-avoidance and damage-repair alter host competence in the predicted directions. Finally, we suggest that by incorporating these links, future theoretical studies could provide new insights into infectious disease dynamics and host-pathogen coevolution.
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Affiliation(s)
- Amberleigh E Henschen
- Department of Natural Resource Ecology and Management, Iowa State University, 339 Science Hall II, 2310 Pammel Drive, Ames, IA 50011, USA
| | - James S Adelman
- Department of Natural Resource Ecology and Management, Iowa State University, 339 Science Hall II, 2310 Pammel Drive, Ames, IA 50011, USA
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28
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Understanding the Evolutionary Ecology of host--pathogen Interactions Provides Insights into the Outcomes of Insect Pest Biocontrol. Viruses 2020; 12:v12020141. [PMID: 31991772 PMCID: PMC7077243 DOI: 10.3390/v12020141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/15/2020] [Accepted: 01/17/2020] [Indexed: 01/07/2023] Open
Abstract
The use of viral pathogens to control thepopulation size of pest insects has produced both successful and unsuccessful outcomes. Here, we investigate whether those biocontrol successes and failures can be explained by key ecological and evolutionary processes between hosts and pathogens. Specifically, we examine how heterogeneity inpathogen transmission, ecological and evolutionary tradeoffs, andpathogen diversity affect insect population density and thus successful control. Wefirst review theexisting literature and then use numerical simulations of mathematical models to further explore these processes. Our results show that thecontrol of insect densities using viruses depends strongly on theheterogeneity of virus transmission among insects. Overall, increased heterogeneity of transmission reduces theeffect of viruses on insect densities and increases thelong-term stability of insect populations. Lower equilibrium insect densities occur when transmission is heritable and when there is atradeoff between mean transmission and insect fecundity compared to when theheterogeneity of transmission arises from non-genetic sources. Thus, theheterogeneity of transmission is akey parameter that regulates thelong-term population dynamics of insects and their pathogens. Wealso show that both heterogeneity of transmission and life-history tradeoffs modulate characteristics of population dynamics such as thefrequency and intensity of ``boom--bust" population cycles. Furthermore, we show that because of life-history tradeoffs affecting thetransmission rate, theuse of multiple pathogen strains is more effective than theuse of asingle strain to control insect densities only when thepathogen strains differ considerably intheir transmission characteristics. By quantifying theeffects of ecology and evolution on population densities, we are able to offer recommendations to assess thelong-term effects of classical biocontrol.
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29
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Flies AS, Flies EJ, Fox S, Gilbert A, Johnson SR, Liu GS, Lyons AB, Patchett AL, Pemberton D, Pye RJ. An oral bait vaccination approach for the Tasmanian devil facial tumor diseases. Expert Rev Vaccines 2020; 19:1-10. [PMID: 31971036 DOI: 10.1080/14760584.2020.1711058] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Introduction: The Tasmanian devil (Sarcophilus harrisii) is the largest extant carnivorous marsupial. Since 1996, its population has declined by 77% primarily due to a clonal transmissible tumor, known as devil facial tumor (DFT1) disease. In 2014, a second transmissible devil facial tumor (DFT2) was discovered. DFT1 and DFT2 are nearly 100% fatal.Areas covered: We review DFT control approaches and propose a rabies-style oral bait vaccine (OBV) platform for DFTs. This approach has an extensive safety record and was a primary tool in large-scale rabies virus elimination from wild carnivores across diverse landscapes. Like rabies virus, DFTs are transmitted by oral contact, so immunizing the oral cavity and stimulating resident memory cells could be advantageous. Additionally, exposing infected devils that already have tumors to OBVs could serve as an oncolytic virus immunotherapy. The primary challenges may be identifying appropriate DFT-specific antigens and optimization of field delivery methods.Expert opinion: DFT2 is currently found on a peninsula in southern Tasmania, so an OBV that could eliminate DFT2 should be the priority for this vaccine approach. Translation of an OBV approach to control DFTs will be challenging, but the approach is feasible for combatting ongoing and future disease threats.
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Affiliation(s)
- Andrew S Flies
- Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Australia
| | - Emily J Flies
- School of Natural Sciences, College of Sciences and Engineering, University of Tasmania, Sandy Bay, Australia
| | - Samantha Fox
- Save the Tasmanian Devil Program, DPIPWE, Hobart, Australia.,Toledo Zoo, Toledo, OH, USA
| | - Amy Gilbert
- National Wildlife Research Center, USDA, APHIS, Wildlife Services, Fort Collins, CO, USA
| | - Shylo R Johnson
- National Wildlife Research Center, USDA, APHIS, Wildlife Services, Fort Collins, CO, USA
| | - Guei-Sheung Liu
- Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, East Melbourne, Australia
| | - A Bruce Lyons
- School of Medicine, College of Health and Medicine, University of Tasmania, Hobart, Australia
| | - Amanda L Patchett
- Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Australia
| | | | - Ruth J Pye
- Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Australia
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30
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Host exposure history modulates the within-host advantage of virulence in a songbird-bacterium system. Sci Rep 2019; 9:20348. [PMID: 31889059 PMCID: PMC6937340 DOI: 10.1038/s41598-019-56540-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 12/14/2019] [Indexed: 11/08/2022] Open
Abstract
The host immune response can exert strong selective pressure on pathogen virulence, particularly when host protection against reinfection is incomplete. Since emerging in house finch populations, the bacterial pathogen Mycoplasma gallisepticum (MG) has been increasing in virulence. Repeated exposure to low-doses of MG, a proxy for what birds likely experience while foraging, provides significant but incomplete protection against reinfection. Here we sought to determine if the within-host, pathogen load advantage of high virulence is mediated by the degree of prior pathogen exposure, and thus the extent of immune memory. We created variation in host immunity by experimentally inoculating wild-caught, MG-naïve house finches with varying doses and number of exposures of a single pathogen strain of intermediate virulence. Following recovery from priming exposures, individuals were challenged with one of three MG strains of distinct virulence. We found that the quantitative pathogen load advantage of high virulence was strongly mediated by the degree of prior exposure. The greatest within-host load advantage of virulence was seen in hosts given low-dose priming exposures, akin to what many house finches likely experience while foraging. Our results show that incomplete host immunity produced by low-level prior exposure can create a within-host environment that favors more virulent pathogens.
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31
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Miller IF, Metcalf CJ. Vaccine-driven virulence evolution: consequences of unbalanced reductions in mortality and transmission and implications for pertussis vaccines. J R Soc Interface 2019; 16:20190642. [PMID: 31822219 PMCID: PMC6936036 DOI: 10.1098/rsif.2019.0642] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 11/19/2019] [Indexed: 11/12/2022] Open
Abstract
Many vaccines have heterogeneous effects across individuals. Additionally, some vaccines do not prevent infection, but reduce disease-associated mortality and transmission. Both of these factors will alter selection pressures on pathogens and thus shape the evolution of pathogen virulence. We use a mathematical modelling framework to show that (i) the balance of how vaccines reduce transmission versus mortality and (ii) individual variability in protection conferred both shape the evolution of pathogen virulence. Epidemiological (burden of disease) and evolutionary (pathogen virulence) outcomes are both worse when vaccines confer smaller reductions in transmission than in mortality. Furthermore, outcomes are modulated by variability in vaccine effects, with increased variability limiting the extent of virulence evolution but in some cases preventing eradication. These findings are pertinent to current concerns about the global resurgence of pertussis and the efficacy of pertussis vaccines, as the two classes of these vaccines may reduce disease symptoms without preventing infection and differ in their ability to reduce transmission. Furthermore, these findings point to the importance of generating precise predictions for virulence evolution in Bordetella pertussis (and other similar pathogens) by incorporating empirical characterizations of vaccine effects into models capturing the epidemiological details of this system.
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Affiliation(s)
- Ian F. Miller
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - C. Jessica Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
- Woodrow Wilson School of Public Affairs, Princeton University, Princeton, NJ, USA
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32
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Duggal NK, Langwig KE, Ebel GD, Brault AC. On the Fly: Interactions Between Birds, Mosquitoes, and Environment That Have Molded West Nile Virus Genomic Structure Over Two Decades. JOURNAL OF MEDICAL ENTOMOLOGY 2019; 56:1467-1474. [PMID: 31549720 PMCID: PMC7182917 DOI: 10.1093/jme/tjz112] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Indexed: 05/15/2023]
Abstract
West Nile virus (WNV) was first identified in North America almost 20 yr ago. In that time, WNV has crossed the continent and established enzootic transmission cycles, resulting in intermittent outbreaks of human disease that have largely been linked with climatic variables and waning avian seroprevalence. During the transcontinental dissemination of WNV, the original genotype has been displaced by two principal extant genotypes which contain an envelope mutation that has been associated with enhanced vector competence by Culex pipiens L. (Diptera: Culicidae) and Culex tarsalis Coquillett vectors. Analyses of retrospective avian host competence data generated using the founding NY99 genotype strain have demonstrated a steady reduction in viremias of house sparrows over time. Reciprocally, the current genotype strains WN02 and SW03 have demonstrated an inverse correlation between house sparrow viremia magnitude and the time since isolation. These data collectively indicate that WNV has evolved for increased avian viremia while house sparrows have evolved resistance to the virus such that the relative host competence has remained constant. Intrahost analyses of WNV evolution demonstrate that selection pressures are avian species-specific and purifying selection is greater in individual birds compared with individual mosquitoes, suggesting that the avian adaptive and/or innate immune response may impose a selection pressure on WNV. Phylogenomic, experimental evolutionary systems, and models that link viral evolution with climate, host, and vector competence studies will be needed to identify the relative effect of different selective and stochastic mechanisms on viral phenotypes and the capacity of newly evolved WNV genotypes for transmission in continuously changing landscapes.
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Affiliation(s)
- Nisha K Duggal
- Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Kate E Langwig
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Gregory D Ebel
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO
| | - Aaron C Brault
- Division of Vector-borne Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
- Corresponding author, e-mail:
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33
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Perez K, Mullen N, Canter JA, Ley DH, May M. Phenotypic diversity in an emerging mycoplasmal disease. Microb Pathog 2019; 138:103798. [PMID: 31639466 DOI: 10.1016/j.micpath.2019.103798] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 10/08/2019] [Accepted: 10/11/2019] [Indexed: 11/27/2022]
Abstract
The avian pathogen Mycoplasma gallisepticum (MG) is a known pathogen of poultry, and newly emerged pathogen of house finches wherein it is associated with lethal conjunctivitis. Factors present in MG that are known to mediate virulence include cytadherence, sialidase activity, peroxide production, and biofilm formation. We have quantitatively assessed these factors for MG isolates from house finches from a temporal and geographic distribution across the continental United States that show differing capacity for virulence in vivo. Statistically significant (P < 0.05) differences were observed across strains for sialidase activity, cytadherence, and hydrogen peroxide production. Sialidase activity increased over time in geographically static populations, but did not correlate with time overall. All strains were able to bind α-2,6-linked sialic acid. No strains were found to bind α-2,3-linked sialic acid. All strains produced biofilms in vitro; however, no significant differences were observed in the density of biofilms across strains. Quantitative variance in virulence-associated traits is consistent with within-host evolutionary adaptation in response to a change in ecological niche by a parasitic pathogen.
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Affiliation(s)
- Kailey Perez
- Department of Biomedical Sciences, University of New England, Biddeford, ME, USA
| | - Nathan Mullen
- Department of Biomedical Sciences, University of New England, Biddeford, ME, USA
| | - Jessica A Canter
- Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT, USA
| | - David H Ley
- Department of Population Health and Pathobiology, North Carolina State University, Raleigh, NC, USA
| | - Meghan May
- Department of Biomedical Sciences, University of New England, Biddeford, ME, USA.
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34
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Guth S, Visher E, Boots M, Brook CE. Host phylogenetic distance drives trends in virus virulence and transmissibility across the animal-human interface. Philos Trans R Soc Lond B Biol Sci 2019; 374:20190296. [PMID: 31401961 PMCID: PMC6711300 DOI: 10.1098/rstb.2019.0296] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2019] [Indexed: 12/18/2022] Open
Abstract
Historically, efforts to assess 'zoonotic risk' have focused mainly on quantifying the potential for cross-species emergence of viruses from animal hosts. However, viruses clearly differ in relative burden, both in terms of morbidity and mortality (virulence) incurred and the capacity for sustained human-to-human transmission. Extending previously published databases, we delineated host and viral traits predictive of human mortality associated with viral spillover, viral capacity to transmit between humans following spillover and the probability of a given virus being zoonotic. We demonstrate that increasing host phylogenetic distance from humans positively correlates with human mortality but negatively correlates with human transmissibility, suggesting that the virulence induced by viruses emerging from hosts at high phylogenetic distance may limit capacity for human transmission. Our key result is that hosts most closely related to humans harbour zoonoses of lower impact in terms of morbidity and mortality, while the most distantly related hosts-in particular, order Chiroptera (bats)-harbour highly virulent zoonoses with a lower capacity for endemic establishment in human hosts. As a whole, our results emphasize the importance of understanding how zoonoses manifest in the human population and also highlight potential risks associated with multi-host transmission chains in spillover. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.
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Affiliation(s)
- Sarah Guth
- Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Elisa Visher
- Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Mike Boots
- Department of Integrative Biology, University of California, Berkeley, CA, USA
- Centre for Ecology and Conservation, University of Exeter, Exeter TR10 9FE, UK
| | - Cara E. Brook
- Department of Integrative Biology, University of California, Berkeley, CA, USA
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35
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Affiliation(s)
- Maziar Divangahi
- Departments of Medicine, Microbiology and Immunology, and Pathology, Meakins-Christie Laboratories, McGill International TB Centre and McGill University Health Centre, McGill University, Montreal, Québec, Canada.
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36
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Contrasting evolution of virulence and replication rate in an emerging bacterial pathogen. Proc Natl Acad Sci U S A 2019; 116:16927-16932. [PMID: 31371501 PMCID: PMC6708350 DOI: 10.1073/pnas.1901556116] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With increasing antibiotic resistance, there is a pressing need to understand how host resistance naturally influences bacterial virulence and replication rates. We test this in an infection experiment using 55 isolates of a bacterium, which were collected over the course of the epidemic following its natural emergence in a North American songbird. We demonstrate virulence has increased linearly from outbreak to the present day, encompassing >150,000 bacterial generations. Despite this, bacterial replication rate only increased during the initial spread of host resistance but not thereafter. Thus, contrary to common assumptions, virulence and replication rates can evolve independently, particularly after the initial spread of host resistance. Host resistance through immune clearance is predicted to favor pathogens that are able to transmit faster and are hence more virulent. Increasing pathogen virulence is, in turn, typically assumed to be mediated by increasing replication rates. However, experiments designed to test how pathogen virulence and replication rates evolve in response to increasing host resistance, as well as the relationship between the two, are rare and lacking for naturally evolving host–pathogen interactions. We inoculated 55 isolates of Mycoplasma gallisepticum, collected over 20 y from outbreak, into house finches (Haemorhous mexicanus) from disease-unexposed populations, which have not evolved protective immunity to M. gallisepticum. We show using 3 different metrics of virulence (body mass loss, symptom severity, and putative mortality rate) that virulence has increased linearly over >150,000 bacterial generations since outbreak (1994 to 2015). By contrast, while replication rates increased from outbreak to the initial spread of resistance (1994 to 2004), no further increases have occurred subsequently (2007 to 2015). Finally, as a consequence, we found that any potential mediating effect of replication rate on virulence evolution was restricted to the period when host resistance was initially increasing in the population. Taken together, our results show that pathogen virulence and replication rates can evolve independently, particularly after the initial spread of host resistance. We hypothesize that the evolution of pathogen virulence can be driven primarily by processes such as immune manipulation after resistance spreads in host populations.
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37
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Langwig KE, Gomes MGM, Clark MD, Kwitny M, Yamada S, Wargo AR, Lipsitch M. Limited available evidence supports theoretical predictions of reduced vaccine efficacy at higher exposure dose. Sci Rep 2019; 9:3203. [PMID: 30824732 PMCID: PMC6397254 DOI: 10.1038/s41598-019-39698-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 01/30/2019] [Indexed: 12/18/2022] Open
Abstract
Understanding the causes of vaccine failure is important for predicting disease dynamics in vaccinated populations and planning disease interventions. Pathogen exposure dose and heterogeneity in host susceptibility have both been implicated as important factors that may reduce overall vaccine efficacy and cause vaccine failure. Here, we explore the effect of pathogen dose and heterogeneity in host susceptibility in reducing efficacy of vaccines. Using simulation-based methods, we find that increases in pathogen exposure dose decrease vaccine efficacy, but this effect is modified by heterogeneity in host susceptibility. In populations where the mode of vaccine action is highly polarized, vaccine efficacy decreases more slowly with exposure dose than in populations with less variable protection. We compared these theoretical results to empirical estimates from a systematic literature review of vaccines tested over multiple exposure doses. We found that few studies (nine of 5,389) tested vaccine protection against infection over multiple pathogen challenge doses, with seven studies demonstrating a decrease in vaccine efficacy with increasing exposure dose. Our research demonstrates that pathogen dose has potential to be an important determinant of vaccine failure, although the limited empirical data highlight a need for additional studies to test theoretical predictions on the plausibility of reduced host susceptibility and high pathogen dose as mechanisms responsible for reduced vaccine efficacy in high transmission settings.
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Affiliation(s)
- Kate E Langwig
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA. .,Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, 02115, USA.
| | - M Gabriela M Gomes
- CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Vairão, Portugal.,Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Mercedes D Clark
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Molly Kwitny
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Steffany Yamada
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Andrew R Wargo
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA, 23062, USA
| | - Marc Lipsitch
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, 02115, USA
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38
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Immunologic Pathways in Protective versus Maladaptive Host Responses to Attenuated and Pathogenic Strains of Mycoplasma gallisepticum. Infect Immun 2019; 87:IAI.00613-18. [PMID: 30559221 DOI: 10.1128/iai.00613-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 11/20/2018] [Indexed: 01/06/2023] Open
Abstract
Mycoplasmas are small bacterial commensals or pathogens that commonly colonize host mucosal tissues and avoid rapid clearance, in part by stimulating inflammatory, immunopathogenic responses. We previously characterized a wide array of transcriptomic perturbations in avian host tracheal mucosae infected with virulent, immunopathologic Mycoplasma gallisepticum; however, mechanisms delineating these from protective responses, such as those induced upon vaccination, have not been thoroughly explored. In this study, host transcriptomic responses to two experimental M. gallisepticum vaccines were assessed during the first 2 days of infection. Relative to virulent infection, host metabolic and immune gene responses to both vaccines were greatly decreased, including early innate immune responses critical to disease development and subsequent adaptive immunity. These data specify host genes and potential mechanisms contributing to maladaptive versus beneficial host responses-information critical for design of vaccines efficacious in both limiting inflammation and enabling pathogen clearance.
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39
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Acevedo MA, Dillemuth FP, Flick AJ, Faldyn MJ, Elderd BD. Virulence-driven trade-offs in disease transmission: A meta-analysis. Evolution 2019; 73:636-647. [PMID: 30734920 DOI: 10.1111/evo.13692] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 12/22/2018] [Indexed: 12/31/2022]
Abstract
The virulence-transmission trade-off hypothesis proposed more than 30 years ago is the cornerstone in the study of host-parasite co-evolution. This hypothesis rests on the premise that virulence is an unavoidable and increasing cost because the parasite uses host resources to replicate. This cost associated with replication ultimately results in a deceleration in transmission rate because increasing within-host replication increases host mortality. Empirical tests of predictions of the hypothesis have found mixed support, which cast doubt about its overall generalizability. To quantitatively address this issue, we conducted a meta-analysis of 29 empirical studies, after reviewing over 6000 published papers, addressing the four core relationships between (1) virulence and recovery rate, (2) within-host replication rate and virulence, (3) within-host replication and transmission rate, and (4) virulence and transmission rate. We found strong support for an increasing relationship between replication and virulence, and replication and transmission. Yet, it is still uncertain if these relationships generally decelerate due to high within-study variability. There was insufficient data to quantitatively test the other two core relationships predicted by the theory. Overall, the results suggest that the current empirical evidence provides partial support for the trade-off hypothesis, but more work remains to be done.
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Affiliation(s)
- Miguel A Acevedo
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, 32611
| | - Forrest P Dillemuth
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Andrew J Flick
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Matthew J Faldyn
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Bret D Elderd
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803
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40
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Flies AS, Woods GM. Editorial: Wild Immunology-The Answers Are Out There. Front Immunol 2019; 10:126. [PMID: 30761154 PMCID: PMC6364755 DOI: 10.3389/fimmu.2019.00126] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 01/15/2019] [Indexed: 11/13/2022] Open
Affiliation(s)
- Andrew S Flies
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Gregory M Woods
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia.,School of Medicine, University of Tasmania, Hobart, TAS, Australia
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41
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Orlov M, Garanina I, Fisunov GY, Sorokin A. Comparative Analysis of Mycoplasma gallisepticum vlhA Promoters. Front Genet 2018; 9:569. [PMID: 30519256 PMCID: PMC6258824 DOI: 10.3389/fgene.2018.00569] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/06/2018] [Indexed: 12/15/2022] Open
Abstract
Mycoplasma gallisepticum is an intracellular parasite affecting respiratory tract of poultry that belongs to class Mollicutes. M. gallisepticum features numerous variable lipoprotein hemagglutinin genes (vlhA) that play a role in immune escape. The vlhA promoters have a set of distinct properties in comparison to promoters of the other genes. The vlhA promoters carry a variable GAA repeats region at approximately 40 nts upstream of transcription start site. The promoters have been considered active only in the presence of exactly 12 GAA repeats. The mechanisms of vlhA expression regulation and GAA number variation are not described. Here we tried to understand these mechanisms using different computational methods. We conducted a comparative analysis among several M. gallisepticum strains. Nucleotide sequences analysis showed the presence of highly conserved regions flanking repeated trinucleotides that are not linked to GAA number variation. VlhA genes with 12 GAA repeats and their orthologs in 12 M. gallisepticum strains are more conserved than other vlhA genes and have narrower GAA number distribution. We conducted comparative analysis of physicochemical profiles of M. gallisepticum vlhA and sigma-70 promoters. Stress-induced duplex destabilization (SIDD) profiles showed that sigma-70 group is characterized by the common to prokaryotic promoters sharp maxima while vlhA promoters are hardly destabilized with the region between GAA repeats and transcription start site having zero opening probability. Electrostatic potential profiles of vlhA promoters indicate the presence of the distinct patterns that appear to govern initial stages of specific DNA-protein recognition. Open state dynamics profiles of vlhA demonstrate the pattern that might facilitate transcription bubble formation. Obtained data could be the basis for experimental identification of mechanisms of phase variation in M. gallisepticum.
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Affiliation(s)
- Mikhail Orlov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
| | - Irina Garanina
- Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical-Biological Agency, Moscow, Russia
| | - Gleb Y Fisunov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Federal Medical-Biological Agency, Moscow, Russia
| | - Anatoly Sorokin
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Russia
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Gates DE, Valletta JJ, Bonneaud C, Recker M. Quantitative host resistance drives the evolution of increased virulence in an emerging pathogen. J Evol Biol 2018; 31:1704-1714. [PMID: 30107064 DOI: 10.1111/jeb.13366] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 07/31/2018] [Accepted: 08/09/2018] [Indexed: 12/01/2022]
Abstract
Emergent infectious diseases can have a devastating impact on host populations. The high selective pressures on both the hosts and the pathogens frequently lead to rapid adaptations not only in pathogen virulence but also host resistance following an initial outbreak. However, it is often unclear whether hosts will evolve to avoid infection-associated fitness costs by preventing the establishment of infection (here referred to as qualitative resistance) or by limiting its deleterious effects through immune functioning (here referred to as quantitative resistance). Equally, the evolutionary repercussions these different resistance mechanisms have for the pathogen are often unknown. Here, we investigate the co-evolutionary dynamics of pathogen virulence and host resistance following the epizootic outbreak of the highly pathogenic bacterium Mycoplasma gallisepticum in North American house finches (Haemorhous mexicanus). Using an evolutionary modelling approach and with a specific emphasis on the evolved resistance trait, we demonstrate that the rapid increase in the frequency of resistant birds following the outbreak is indicative of strong selection pressure to reduce infection-associated mortality. This, in turn, created the ecological conditions that selected for increased bacterial virulence. Our results thus suggest that quantitative host resistance was the key factor underlying the evolutionary interactions in this natural host-pathogen system.
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Affiliation(s)
| | - John Joseph Valletta
- Centre for Mathematics & the Environment, University of Exeter, Penryn, Cornwall, UK
| | | | - Mario Recker
- Centre for Mathematics & the Environment, University of Exeter, Penryn, Cornwall, UK
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Rapid Antagonistic Coevolution in an Emerging Pathogen and Its Vertebrate Host. Curr Biol 2018; 28:2978-2983.e5. [PMID: 30197084 DOI: 10.1016/j.cub.2018.07.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 04/24/2018] [Accepted: 07/02/2018] [Indexed: 02/02/2023]
Abstract
Host-pathogen coevolution is assumed to play a key role in eco-evolutionary processes, including epidemiological dynamics and the evolution of sexual reproduction [1-4]. Despite this, direct evidence for host-pathogen coevolution is exceptional [5-7], particularly in vertebrate hosts. Indeed, although vertebrate hosts have been shown to evolve in response to pathogens or vice versa [8-12], there is little evidence for the necessary reciprocal changes in the success of both antagonists over time [13]. Here, we generate a time-shift experiment to demonstrate adaptive, reciprocal changes in North American house finches (Haemorhous mexicanus) and their emerging bacterial pathogen, Mycoplasma gallisepticum [14-16]. Our experimental design is made possible by the existence of disease-exposed and unexposed finch populations, which were known to exhibit equivalent responses to experimental inoculation until the recent spread of genetic resistance in the former [14, 17]. Whereas inoculations with pathogen isolates from epidemic outbreak caused comparable sub-lethal eye swelling in hosts from exposed (hereafter adapted) and unexposed (hereafter ancestral) populations, inoculations with isolates sampled after the spread of resistance were threefold more likely to cause lethal symptoms in hosts from ancestral populations. Similarly, the probability that pathogens successfully established an infection in the primary host and, before inducing death, transmitted to an uninfected sentinel was highest when recent isolates were inoculated in hosts from ancestral populations and lowest when early isolates were inoculated in hosts from adapted populations. Our results demonstrate antagonistic host-pathogen coevolution, with hosts and pathogens displaying increased resistance and virulence in response to each other over time.
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