Characterizing the chelonian innate immune response through ranaviral challenge and in a natural system

Rayl, Jeremy Michael

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https://hdl.handle.net/2142/101781 Copy

Description

Title

Characterizing the chelonian innate immune response through ranaviral challenge and in a natural system

Author(s)

Rayl, Jeremy Michael

Issue Date

2018-07-03

Director of Research (if dissertation) or Advisor (if thesis)

Allender, Matthew C.

Doctoral Committee Chair(s)

Allender, Matthew C.

Committee Member(s)

• Ko, CheMyong
• Mahoney, Megan
• Phillips, Christopher A.
• Wellehan, James X.F.

Department of Study

Comparative Biosciences

Discipline

VMS - Comparative Biosciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chelonia
• cytokine
• innate immune response
• radio telemetry

Abstract

Chelonians are among the most imperiled vertebrates in the world (Rhodin et al. 2011). Multiple factors contribute to chelonian population declines, including habitat degradation and fragmentation, climate change, and direct anthropogenic effects such as road mortalities and illegal collection for food, medicine, or pet trade (Gibbons 2000). Additionally, disease is playing an increasing role in population stability for many species. However, many cryptic species lack the information concerning disease processes and the overall impacts on population sustainability leading to an inability to inform management decisions. The complex relationships between host, pathogen, and environment need to be investigated to maximize conservation impact. To address deficits in knowledge of chelonian and pathogen dynamics, we designed a cytokine mRNA transcript assay to apply to an experimental challenge study of red-eared sliders (Trachemys scripta elegans) with a highly fatal chelonian pathogen, ranavirus, as well as to a natural population of free-range eastern box turtles (Terrapene carolina carolina) with a history of ranavirus outbreak. The cytokine qPCR assay was successful for the reference gene, beta actin, as well as the cytokine targets interleukin 1-beta, tumor necrosis factor alpha, and interleukin-10. These cytokines have previously identified roles in the ectothermic vertebrate immune response, and were evaluated through these studies of red-eared sliders (N=24) and eastern box turtles (N=36) using repeated samples of RNA extracted from isolated buffy coats (N=599). Patterns of transcription for interleukin 1-beta describe the mechanistic timeline for ranaviral disease in the red-eared sliders. Eastern box turtles with evidence of inflammation based on history and hematology also demonstrated an increase in the inflammatory cytokines. Tumor necrosis factor was measured, though at much lower levels and less consistently than interleukin 1-beta. Interleukin-10 was identified in multiple turtles, consistent with a pattern of anti-inflammatory response in control red-eared sliders and in eastern box turtles with histories of chronic conditions. Overall, cytokine mRNA transcription analysis is a valuable tool as a measurement of chelonian host innate immune response to pathogen exposure and infection. Patterns of increased and decreased transcription over time in our experimental and longitudinal field studies provide guidelines for future research. For hematology, patterns of increased heterophil:lymphocyte ratio also describe the mechanistic timeline of ranaviral disease in the red-eared sliders. In the free-ranging eastern box turtles, hematology varied by sex and season. Home range and movement models were applied to quantify this population’s spatial dynamics over two active seasons. Further investigations of chelonian innate immune response should continue to understand the mechanisms of the host-pathogen interaction through the investigation of additional cytokine targets and pathogens. Enhanced spatiotemporal data will help to recognize drivers of these relationships, and offer insight to population management techniques that contribute to captive and wild chelonian population health.

Graduation Semester

2018-08

Type of Resource

text

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Copyright and License Information

Copyright 2018 Jeremy Rayl

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