Commercial cytokine assay on equine cerebrospinal fluid does not distinguish equine degenerative myeloencephalopathy from cervical vertebral stenotic myelopathy.

Objective: To measure and compare CSF cytokine concentrations among horses with equine neuroaxonal dystrophy (eNAD)/equine degenerative myeloencephalopathy (EDM), horses with cervical vertebral stenotic myelopathy (CVSM), and control horses and to evaluate for associations with clinical parameters.

Methods: Banked equine CSF samples from horses with neurologic disease that underwent a complete neurologic examination and postmortem diagnosis confirmation of CVSM or eNAD/EDM or from control horses were included. Cytokines were measured with an equine-specific cytokine/chemokine magnetic bead multiplex panel (23-cytokine multiplex). Results were compared between groups, and correlations with clinical parameters were evaluated.

Results: Cerebrospinal fluid samples from 35 horses with CVSM, 35 horses with eNAD/EDM, and 8 control horses were analyzed. Most cytokines analyzed were below the lower limit of detection in the majority of samples. Eotaxin, IL-10, interferon-γ-induced protein 10, granulocyte colony-stimulating factor, and tumor necrosis factor-α were detectable in 5 or more samples; however, concentrations were not different between groups. Increasing sample volume or using a commercial protein-concentrating column did not enhance cytokine recovery. In horses with eNAD/EDM, IL-10 concentrations correlated with CSF phosphorylated neurofilament heavy concentrations.

Conclusions: This commercial cytokine assay was unable to distinguish between CVSM and eNAD/EDM based on CSF cytokine profiles in this population.

Clinical relevance: Optimization of a more sensitive assay is warranted as CSF cytokine concentrations have high potential to be used as biomarkers to characterize neuroinflammation in equine neurological diseases.