BIOMARKER IDENTIFICATION IN CEREBROSPINAL FLUID: NEW APPROACHES FOR DISCRIMINATING CENTRAL NERVOUS SYSTEM DISORDERS IN VETERINARY NEUROLOGY

Cerebrospinal fluid (CSF) and serum biomarkers are increasingly recognized in human medicine for their diagnostic, prognostic, and monitoring potential in neurological diseases. However, their application in veterinary neurology, and particularly in large animals, remains limited. This PhD thesis aimed to expand the understanding of central nervous system (CNS) biomarkers in veterinary medicine by exploring the diagnostic potential of neurofilament light chain (Nf-L) and inflammatory mediators in cattle and dogs affected by neurological disorders. In the first project, Nf-L concentration was measured in serum and CSF from healthy (n = 49) and neurologically affected cattle (n = 75) to assess its stability, age-related variation, and diagnostic utility. Nf-L proved stable across storage temperatures (−20 °C and −80 °C). Physiological median Nf-L levels were 6.3 pg/mL (serum) and 414 pg/mL (CSF) in calves and 5.5 pg/mL (serum) and 828 pg/mL (CSF) in adult cattle. CSF Nf-L exhibited significantly elevated levels in animals with degenerative (p = 0.004) and infectious CNS disorders across different age groups (< 2 months, p = 0.04; 2-12 months, p = 0.0001; 1-6 years, p = 0.001), supporting its role as a sensitive marker of axonal damage. A significant relationship between serum and CSF Nf-L concentrations was also observed in diseased cattle (r2 = 0.2, p =0.009), suggesting its potential as a minimally invasive diagnostic tool. A second study extended the evaluation of Nf-L to neurological dogs (n = 83), revealing similar stability across storage conditions and elevated CSF Nf-L concentrations in animals with structural brain disorders (n = 32) compared to those with idiopathic epilepsy (n = 27; p < 0.0001), while no significant differences have been highlighted in the comparison among dogs affected by various structural brain or spinal cord disorders. These findings confirm Nf-L as a reliable marker of structural CNS damage in both species, though its lack of disease specificity underscores the need for complementary diagnostic tools. The third project investigated CSF cytokine and chemokine profiles in healthy (n = 30) and diseased cattle (n = 56) using a multiplex bead-based assay. Physiological levels of CSF cytokines and chemokines in healthy 15 cattle were established. Significantly higher levels of proinflammatory mediators [interleukin (IL)-6, p = 0.02; monocyte chemoattractant protein (MCP)-1, p < 0.001; IL-36 receptor antagonist (RA), p < 0.0001; and IL-10, p < 0.008] were identified in animals with infectious CNS disorders, reflecting active neuroinflammation. These results mirror cytokine patterns described in human bacterial meningitis and support the relevance of inflammatory biomarkers in bovine neurology. Collectively, this work demonstrates the translational value of established human neurological biomarkers in veterinary contexts and highlights the potential of both Nf-L and inflammatory mediators as tools to improve the diagnosis and understanding of CNS diseases in animals. By bridging veterinary and human neurology, these findings contribute to the growing field of comparative neurobiology and offer a foundation for biomarker-guided approaches in clinical veterinary practice