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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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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: 0] [Impact Index Per Article: 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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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: 1] [Impact Index Per Article: 1.0] [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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PREVALENCE AND PATHOGEN LOAD OF EIMERIA IN WILD YELLOW-EYED PENGUINS (MEGADYPTES ANTIPODES) AND THE MORPHOLOGIC CHARACTERIZATION OF A NOVEL EIMERIA SPECIES. J Wildl Dis 2022; 58:836-846. [PMID: 36136602 DOI: 10.7589/jwd-d-21-00146] [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: 09/01/2021] [Accepted: 05/05/2022] [Indexed: 12/04/2022]
Abstract
Coccidia infections in wild birds rarely cause clinical signs; however, disease and mortality can occur with predisposing environmental and host conditions. The Yellow-eyed Penguin (Megadyptes antipodes) is an endangered species endemic to New Zealand that has seen significant ongoing population decline. The aim of this study was to examine the host-pathogen dynamics of coccidian parasites in two wild populations of Yellow-eyed Penguin: the mainland (South Island) population and the sub-Antarctic (Enderby Island) population. There was weak evidence for a difference in the prevalence of the Eimeria sp. in birds from Enderby Island (76.6%; 36/47; 95% confidence interval [CI] 62.78-86.4%) and the South Island of New Zealand (58.54%; 24/41; 95% CI 43.37-72.24%). The mean pathogen load in penguins on Enderby Island was 9,723 oocysts/g of feces (SE=5831 oocysts/g) and from the South Island of New Zealand was 1,050 oocysts/g (SE=398 oocysts/g). No evidence of an association was found between pathogen load and body weight in either study population. The morphology of the sporulated coccidial oocysts was consistent with a novel species of Eimeria. There was statistically significant variation between the oocysts collected from the two sites in all measurements apart from the oocyst wall thickness. However, the standard technique of assessing linear regressions of the length and width of oocysts from both sampling sites was 0.80, and therefore above the standard R2>0.5 used to indicate variation within a single population of oocysts, suggesting that only a single species of Eimeria was present at both sampling locations. The prevalence and pathogen load of Eimeria sp. was substantially higher than previous reports of coccidial oocysts in Yellow-eyed Penguins and free-living Sphenisciformes globally. This host-parasite relationship deserves further investigation, as the impact of this novel organism on the population remains unclear.
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Ruden RM, Adelman JS. Disease tolerance alters host competence in a wild songbird. Biol Lett 2021; 17:20210362. [PMID: 34699737 PMCID: PMC8548076 DOI: 10.1098/rsbl.2021.0362] [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: 07/02/2021] [Accepted: 10/04/2021] [Indexed: 11/12/2022] Open
Abstract
Individuals can express a range of disease phenotypes during infection, with important implications for epidemics. Tolerance, in particular, is a host response that minimizes the per-pathogen fitness costs of infection. Because tolerant hosts show milder clinical signs and higher survival, despite similar pathogen burdens, their potential for prolonged pathogen shedding may facilitate the spread of pathogens. To test this, we simulated outbreaks of mycoplasmal conjunctivitis in house finches, asking how the speed of transmission varied with tissue-specific and behavioural components of tolerance, milder conjunctivitis and anorexia for a given pathogen load, respectively. Because tissue-specific tolerance hinders pathogen deposition onto bird feeders, important transmission hubs, we predicted it would slow transmission. Because behavioural tolerance should increase interactions with bird feeders, we predicted it would speed transmission. Our findings supported these predictions, suggesting that variation in tolerance could help identify individuals most likely to transmit pathogens.
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Affiliation(s)
- Rachel M. Ruden
- Department of Natural Resource Ecology and Management, Iowa State University, Ames, IA, USA
- Iowa Department of Natural Resources, Des Moines, IA, USA
| | - James S. Adelman
- Department of Natural Resource Ecology and Management, Iowa State University, Ames, IA, USA
- Department of Biological Sciences, University of Memphis, Memphis, TN, USA
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Seal S, Dharmarajan G, Khan I. Evolution of pathogen tolerance and emerging infections: A missing experimental paradigm. eLife 2021; 10:e68874. [PMID: 34544548 PMCID: PMC8455132 DOI: 10.7554/elife.68874] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 08/23/2021] [Indexed: 12/11/2022] Open
Abstract
Researchers worldwide are repeatedly warning us against future zoonotic diseases resulting from humankind's insurgence into natural ecosystems. The same zoonotic pathogens that cause severe infections in a human host frequently fail to produce any disease outcome in their natural hosts. What precise features of the immune system enable natural reservoirs to carry these pathogens so efficiently? To understand these effects, we highlight the importance of tracing the evolutionary basis of pathogen tolerance in reservoir hosts, while drawing implications from their diverse physiological and life-history traits, and ecological contexts of host-pathogen interactions. Long-term co-evolution might allow reservoir hosts to modulate immunity and evolve tolerance to zoonotic pathogens, increasing their circulation and infectious period. Such processes can also create a genetically diverse pathogen pool by allowing more mutations and genetic exchanges between circulating strains, thereby harboring rare alive-on-arrival variants with extended infectivity to new hosts (i.e., spillover). Finally, we end by underscoring the indispensability of a large multidisciplinary empirical framework to explore the proposed link between evolved tolerance, pathogen prevalence, and spillover in the wild.
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Affiliation(s)
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of GeorgiaAikenUnited States
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Becker DJ, Downs CJ, Martin LB. Multi-Scale Drivers of Immunological Variation and Consequences for Infectious Disease Dynamics. Integr Comp Biol 2020; 59:1129-1137. [PMID: 31559436 DOI: 10.1093/icb/icz138] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The immune system is the primary barrier to parasite infection, replication, and transmission following exposure, and variation in immunity can accordingly manifest in heterogeneity in traits that govern population-level infectious disease dynamics. While much work in ecoimmunology has focused on individual-level determinants of host immune defense (e.g., reproductive status and body condition), an ongoing challenge remains to understand the broader evolutionary and ecological contexts of this variation (e.g., phylogenetic relatedness and landscape heterogeneity) and to connect these differences into epidemiological frameworks. Ultimately, such efforts could illuminate general principles about the drivers of host defense and improve predictions and control of infectious disease. Here, we highlight recent work that synthesizes the complex drivers of immunological variation across biological scales of organization and scales these within-host differences to population-level infection outcomes. Such studies note the limitations involved in making species-level comparisons of immune phenotypes, stress the importance of spatial scale for immunology research, showcase several statistical tools for translating within-host data into epidemiological parameters, and provide theoretical frameworks for linking within- and between-host scales of infection processes. Building from these studies, we highlight several promising avenues for continued work, including the application of machine learning tools and phylogenetically controlled meta-analyses to immunology data and quantifying the joint spatial and temporal dependencies in immune defense using range expansions as model systems. We also emphasize the use of organismal traits (e.g., host tolerance, competence, and resistance) as a way to interlink various scales of analysis. Such continued collaboration and disciplinary cross-talk among ecoimmunology, disease ecology, and mathematical modeling will facilitate an improved understanding of the multi-scale drivers and consequences of variation in host defense.
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Affiliation(s)
- Daniel J Becker
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.,Center for the Ecology of Infectious Disease, University of Georgia, Athens, GA 30602, USA
| | - Cynthia J Downs
- Department of Biology, Hamilton College, Clinton, NY 13323, USA
| | - Lynn B Martin
- Department of Global and Planetary Health, University of South Florida, Tampa, FL 33620, USA
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