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Developing an improved laboratory diagnostic test for early detection of sepsis in dogs

Brookes, Laura (2021) Developing an improved laboratory diagnostic test for early detection of sepsis in dogs. PhD thesis, Murdoch University.

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Abstract

Dogs with sepsis – the life-threatening tissue damage resulting from an inappropriate host response to infection – often suffer up to 50% mortality, largely due to a lack of accurate clinical and laboratory tests for rapid diagnosis and guiding management. Procalcitonin (PCT) is a biomarker used for rapid and accurate diagnosis and management of sepsis in humans, thereby improving outcomes. Commercial assays for canine PCT (cPCT) are available; although prior to this project they were not validated. Different antigenicity between recombinant and native PCT was one possible explanation for poor performance of canine PCT ELISAs. Chapter One identified a need for a monoclonal antibody confirmed to detect native canine PCT. This would enable development of a reliable ELISA for procalcitonin measurement in dogs with sepsis. This project aimed to produce monoclonal antibodies (Mabs) recognizing native cPCT to develop a rapid and specific cPCT diagnostic test for sepsis. Additionally, this project aimed to better understand the epidemiology of canine sepsis.

Chapter Two features an epidemiological study of sepsis in hospitalized dogs, contributing a large study to the currently limited data on clinical impact of canine sepsis. For 486 admissions of dogs, sepsis prevalence was 5.5% and incidence was 2.2%. The most common source of infection was peritonitis. Mortality was highest in the sepsis group at 35.1% (p=0.0008, χ2 test; overall mortality 15.4%), compared with dogs who had non-infectious systemic inflammatory response syndrome (SIRS) or infection. All sepsis deaths occurred within four days of diagnosis. Cost and length of hospitalisation were also highest for sepsis.

Chapters Three and Four describe how native cPCT was extracted from canine thyroid glands, isolated via chromatography, identified with a commercial procalcitonin antibody (BioVendor, Asheville, NC, USA), confirmed by mass spectrometry (MS), and used to immunize mice although purity was low (≤42%). This produced two Mabs, that were assessed for PCT affinity using immunoprecipitation and MS. Unfortunately, neither monoclonal antibody demonstrated affinity to native or recombinant PCT, most likely due to insufficient purification or sameness between canine and murine PCT. However, the same screening confirmed the BioVendor polyclonal antibody does recognise native canine procalcitonin in septic dog plasma, contributing to its validation. Furthermore, native PCT was detected in septic dog plasma directly using mass spectrometry.

In Chapter Five, a general discussion gives an overview of the project findings and recommends future directions. Focus should be directed towards full validation of the existing antibody in the BioVendor ELISA, calibration, and reference intervals. A monoclonal antibody should be developed to native canine PCT to enable consistent quantitation of PCT. Larger epidemiological studies can provide information on the impact of sepsis in the wider canine population.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Veterinary Medicine
Supervisor(s): Currie, Andrew, Sharp, Claire, Rossi, Gabriele and Gummer, Joel
URI: http://researchrepository.murdoch.edu.au/id/eprint/64690
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