Abstract
Studies of large free-ranging mammals incorporating physiological measurements typically require the collection of urine or faecal samples, due to ethical and practical concerns over trapping or darting animals. However, there is a dearth of validated biomarkers of immune activation and inflammation that can be measured non-invasively. We here evaluate the utility of urinary measurements of the soluble form of the urokinase plasminogen activator receptor (suPAR), for use as a health marker in studies of wild large mammals. We investigate how urinary suPAR concentrations change in response to viral infection and surgical trauma (inflammation), comparing it to the measurement of a marker of cellular immune activation, urinary neopterin (uNEO), in captive rhesus macaques. We then test the field utility of urinary suPAR, assessing the effects of soil and faecal contamination, sunlight, storage at different temperatures, freeze–thaw cycles, and lyophilization. We find that suPAR concentrations rise markedly in response to both infection and surgery-associated inflammation, unlike uNEO concentrations, which only rise in response to the former. Our field validation demonstrates that urinary suPAR is reasonably robust to many of the issues associated with field collection, sample processing, and storage, as long as samples can be stored in a freezer. Urinary suPAR is thus a promising biomarker applicable for monitoring various aspects of health in wild primates and potentially also other large mammals.
Highlights
Studies of large-bodied wild and free-ranging mammals present specific problems due to the physical difficulties, expense, and ethics associated with capturing and anaesthetizing them for blood collection
Based on the finding that wounding and surgical trauma is associated with secretion of inflammation markers such as acute phase proteins [66,67], we predicted that the medical interventions would activate suPAR secretion and that this would be reflected in elevated urinary suPAR concentrations
Given that urinary neopterin (uNEO) concentrations showed a stronger and broader response to infection than suPAR, but that suPAR concentrations showed a clear response to tissue inflammation whereas uNEO did not, it seems that NEO is likely to be a better marker for measuring infection, and suPAR for tissue damage and inflammation
Summary
Studies of large-bodied wild and free-ranging mammals present specific problems due to the physical difficulties, expense, and ethics associated with capturing and anaesthetizing them for blood collection. Given the usefulness of biomarkers that could be potentially measured non-invasively to reflect various aspects of health, and the dearth of such biomarkers that are available for use, new biomarkers of inflammation, infection and immune system activation that can be measured in the urine and/or faecal samples of large mammals are needed. We assessed the validity of suPAR as a non-invasive urinary biomarker of inflammation and immune system activation processes in a primate model, the rhesus macaque (Study 1: biological and analytical validation). Based on the finding that wounding and surgical trauma is associated with secretion of inflammation markers such as acute phase proteins [66,67], we predicted that the medical interventions would activate suPAR secretion and that this would be reflected in elevated urinary suPAR concentrations
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