Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Mackin, Andrew

Committee Member

Pharr, G. Todd

Committee Member

Bulla, Camilo

Committee Member

Lunsford, Kari

Committee Member

Pinchuk, Lesya

Other Advisors or Committee Members

Wills, Robert||Archer, Todd

Date of Degree

5-7-2016

Document Type

Dissertation - Open Access

Major

Veterinary Medicine

Degree Name

Doctor of Philosophy

College

College of Veterinary Medicine

Department

Veterinary Medical Science Program

Abstract

Cyclosporine is a commonly used immunosuppressive drug in dogs, but dosing is often empirical and based primarily on clinical response. Pharmacokinetic monitoring of blood drug concentrations can be performed, but target blood concentrations for various disease states in dogs are not well described. Pharmacodynamic assays measuring the effects of cyclosporine on target cells are being used to evaluate immunosuppressive effectiveness in humans, but have been minimally explored in veterinary medicine. This dissertation describes the development of pharmacodynamic assays for measuring the effects of cyclosporine on canine T cell cytokine production and surface antigen expression. Incubation with cyclosporine in vitro caused significant suppression of activated T cell production of interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-gamma), CD25, and CD95 measured in peripheral blood mononuclear cells using flow cytometry. IL-2 and IFN-gamma were then evaluated using flow cytometry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) in whole blood incubated with cyclosporine and dexamethasone in vitro. Cyclosporine caused concentration-dependent inhibition of both cytokines, and a greater degree of suppression was noted with qRT-PCR than flow cytometry. Dexamethasone caused concentration-dependent inhibition of IFN-gamma with both methods, but IL-2 reduction was only significant for qRT-PCR. Both methods were then used to evaluate IL-2 and IFN-gamma after administration of high dose oral cyclosporine to dogs. Both qRT-PCR and flow cytometry identified marked cytokine suppression after cyclosporine dosing, but qRT-PCR was uniformly suppressed across the 12-hour dosing interval, while flow cytometry results were significantly higher at trough blood drug concentrations than at peak blood concentrations and subsequent post-dosing time points. Both flow cytometry and qRT-PCR are valid methods for evaluation of T cell cytokine expression in dogs. Further study at lower drug doses is needed to correlate pharmacodynamic results with pharmacokinetic drug concentrations, and to confirm the best method for cytokine monitoring. Studies in clinic patients are also needed to determine the level of cytokine suppression associated with clinical effectiveness in different disease states. Pharmacodynamic evaluation of cyclosporine’s effects shows promise, and may allow for more individualized dosing of cyclosporine in dogs.

URI

https://hdl.handle.net/11668/17733

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