Insight into Chelonian Innate Immune Response by Tracking Cytokine Transcription Over Time in Experimental and Free-Ranging Populations
Global reptile populations face numerous threats to viability, including disease.3 In chelonians and other herptile species, innate immunity is an important factor in host response to infectious disease.5 Cytokines are transient signaling molecules that trigger a myriad of responses in the vertebrate innate immune system.1 Cytokine mRNA transcription analysis has been used in other vertebrates as a measure of the innate immune response.2,4 To evaluate the chelonian immune response, we designed assays for three cytokine targets in chelonians for experimental and field testing: interleukin 1-beta (IL1B) and tumor necrosis factor-alpha (TNF) which are pro-inflammatory, and interleukin 10 (IL10), which is anti-inflammatory. As a model species, red-eared sliders (Trachemys scripta elegans) were challenged with frog virus-3 at two temperatures (28°C, 22°C), and samples were collected twice weekly over 30 days for hematology, pathogen detection, and cytokine mRNA transcription analysis. IL1B was significantly greater in infected turtles compared to uninfected turtles, with differences in transcription across time frames and temperatures. TNF and IL10 were transcribed at detectable levels but were not significantly different between groups. In free-ranging eastern box turtles, samples were collected bi-weekly over two active seasons (2016–2017) for hematology, pathogen detection, and cytokine mRNA transcription analysis. IL1B transcription was highest in the summer of 2016 and the spring of 2017, while transcription for TNF and IL10 were similar between seasons and years. IL1B and IL10 transcription were greater in females. Using these assays, we seek to elaborate chelonian health by quantifying host response to pathogens and the environment.
Thank you to Kayla Boers and Marta Kelly for assistance with slider care and sampling. Additionally, thank you to Marta Kelly and to Michelle Beermann for your summer assistance. Finally, thank you to John Rucker, the turtle dogs, and WEL members for their contributions to box turtle health.
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