Soluble TIM-3 and galectin-9 in cerebrospinal fluid are associated with disability at 6 months in aquaporin-4 IgG-positive neuromyelitis optica spectrum disorder.

Background: Neuromyelitis optica spectrum disorders (NMOSD) are severe autoimmune diseases of the central nervous system characterized by autoantibodies against aquaporin 4 (AQP4-IgG). Despite the availability of several molecular targeted therapies, biomarkers capable of predicting subsequent disability early during the acute relapse phase remain insufficient. Given that abnormalities in immune checkpoint molecules are known to be involved in autoimmunity, this study investigated whether immune checkpoint-related molecules in the cerebrospinal fluid (CSF) of acute-phase AQP4-IgG-positive NMOSD patients correlate with disability at 6 months. Methods: Thirty-four patients with AQP4 IgG-positive NMOSD, 10 patients with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD)at disease flare, and 11 patients with idiopathic normal pressure hydrocephalus (iNPH) as control non-inflammatory neurological disease were enrolled. Bead-based multiplex assays were used to quantify levels of immune checkpoint molecules and related factors (PD-1, PD-L1, CTLA-4, TIM-3, galectin-9, LAG-3, 4-1BB, B7.2, IL-2Rα, TGF-β1, FasL) in CSF. These molecules were measured in the soluble fraction. Disease severity at 6 months was classified as mild (EDSS < 6) or severe (EDSS ≥ 6). ROC analysis was performed to evaluate prognostic performance. Results: Twenty-six cases of NMOSD showed mild disability, and 8 cases showed severe disability. All cases of MOGAD showed mild disability. Compared to the mild group, the severe group had higher age, a higher male ratio, and higher cerebrospinal fluid protein levels (p=0.004, p=0.017, p<0.001, respectively). Cerebrospinal fluid levels of TIM-3, galectin-9, and IL-2Rα were significantly higher in the severe group (p=0.011, p=0.008, p=0.006, respectively), with area under the ROC curve values of 0.89, 0.88, and 0.80, respectively. Conclusion: In AQP4-IgG-positive NMOSD patients, elevated levels of TIM-3, galectin-9, and IL-2Rα in CSF during the acute attack phase correlate with worsening disability severity at 6 months. These findings suggest their potential as early prognostic biomarkers, which requires validation in a large cohort.