CSF Proteins Associated With Neuroaxonal Damage in Early Active Multiple Sclerosis

The aim of this study was to identify biological processes associated with neuroaxonal degeneration in multiple sclerosis (MS) by analyzing protein patterns linked to neurofilament light (NfL) protein in CSF and serum samples.

The highly sensitive proximity extension assay technology was used to quantify protein levels in paired CSF and serum samples from treatment-naïve, early-stage active MS patients (n = 114). The cohort was stratified into above and below median of CSF-NfL level. A discovery phase identified proteins upregulated in CSF, and a validation cohort (n = 128) confirmed findings in a more clinically diverse MS population, including patients receiving disease-modifying therapies.

In the discovery cohort, 13 proteins were upregulated in CSF (leukocyte immunoglobulin like receptor B4, CXCL6, CXCL5, cluster of differentiation 38, CCL19, CXCL11, IMPA1, macrophage scavenger receptor 1 (MSR1), CXCL10, monocyte chemotactic protein 2, ITM2A, TNFRSF12A, and CCL23). It is important to note that associations with CCL19, CXCL11, MSR1, CXCL10, TNFRSF12A, and CCL23 were replicated in a validation MS cohort. By contrast, no consistent serum protein profiles associated with serum levels of NfL could be discerned in this group-based analysis. Furthermore, 75 CSF proteins showed a positive adjusted linear association with CSF-NfL, whereas no such significant association remained in the corresponding analysis in serum.

The identified and replicated CSF protein profile indicates distinct inflammatory processes associated with ongoing neuroaxonal degeneration. All of these most robust 6 proinflammatory markers-CCL19, CXCL11, MSR1, CXCL10, TNFRSF12A, and CCL23-independently replicated and were individually observed to be relevant in the context of MS. These findings may further elucidate the immunologic pathways underlying disease processes leading to neuroaxonal degeneration.