Background: Neurofilament light chain (NfL) and glial fibrilliary acidic protein (GFAP) have been suggested to be biomarkers of the pathophysiological process of neuromyelitis optica spectrum disorders (NMOSD), but the relationship between the plasma levels of these molecules with disease activity and treatment is incompletely understood. Objective: To investigate the treatment effects of disease-modifying drugs on plasma neurofilament light chain (pNfL) and plasma glial fibrillary acidic protein (pGFAP) and explore the predictive value of pNfL and pGFAP in the activity of NMOSD. Methods: pNfL and pGFAP levels were measured using single-molecule arrays in 72 patients with NMOSD and 38 healthy controls (HCs). Patients with NMOSD received tocilizumab ( n = 29), rituximab ( n = 23), oral prednisone ( n = 16), and oral azathioprine or mycophenolate mofetil ( n = 4). Results: NMOSD patients had significantly higher pNfL and pGFAP levels than HCs (pNfL, 18.3 (11.2–39.3) versus 11.5 (7.0–23.3) pg/mL; p = 0.001; pGFAP, 149.7 (88.6–406.5) versus 68.7 (59.4–80.8) pg/mL; p < 0.001). Multivariable regression analyses indicated that baseline pNfL concentration was associated with age ( p = 0.017), Expanded Disability Status Scale (EDSS) score ( p = 0.002), and recent relapses ( p < 0.001). Baseline pGFAP concentration was also associated with EDSS ( p < 0.001) and recent relapses ( p < 0.001). Compared with prednisone, tocilizumab and rituximab significantly reduced pNfL [tocilizumab, exp(β), 0.65; 95% confidence interval (CI), 0.56–0.75; p < 0.001; rituximab, exp(β), 0.79; 95% CI = 0.68–0.93; p = 0.005] and pGFAP levels [tocilizumab, exp(β), 0.64; 95% CI, 0.51–0.80; p < 0.001; rituximab, exp(β), 0.77; 95% CI, 0.61–0.98; p = 0.041] at the end of the study. The pNfL levels in the tocilizumab and rituximab groups were reduced to those of HCs [tocilizumab, 8.5 (7.06–17.90) pg/mL; p = 0.426; rituximab, 14.0 (9.94–21.80) pg/mL; p = 0.216]. However, the pGFAP levels did not decrease to those of HCs in NMOSD patients at the end of study [tocilizumab, 88.9 (63.4–131.8) pg/mL; p = 0.012; rituximab, 141.7 (90.8–192.7) pg/mL; p < 0.001]. Conclusion: pNfL and pGFAP may serve as biomarkers for NMOSD disease activity and treatment effects.

Background: Progressive retinal neuroaxonal damage after acute optic neuritis may occur in neuromyelitis optica spectrum disorder (NMOSD). However, it is unclear if treatments used to prevent attacks influence neurodegeneration.Objectives: We aimed to investigate retinal damage in patients treated with disease-modifying drugs in a longitudinal study.Methods: We retrospectively included 50 patients with aquaporin 4-antibody-seropositive NMOSD. Peripapillary retinal nerve fiber layer (pRNFL) thickness, macular ganglion cell complex (mGCC) thickness, total macular volume (TMV), and optic disc measures were acquired by spectral domain optical coherence tomography in patients treated with tocilizumab, rituximab, and azathioprine.Results: Longitudinally, in eyes with a history of ON (NMOSDON+), we observed annual thinning of mGCC [tocilizumab: −1.77 (−3.44, −0.09) μm, p = 0.041; rituximab: −2.03 (−3.58, −0.48) μm, p = 0.017; azathioprine: −1.79 (−2.22, −1.37) μm, p &lt; 0.001], and pRNFL [tocilizumab: −2.07 (−0.75, −3.39) μm, p = 0.005; rituximab: −2.18 (−0.36, −4.00) μm, p = 0.023; azathioprine: −2.37 (−0.98, −3.75) μm, p = 0.003], reduced TMV [tocilizumab: −0.12 (−0.22, −0.01) mm3, p = 0.028; rituximab: −0.15 (−0.21, −0.08) mm3, p = 0.001; azathioprine: −0.12 (−0.20, −0.04) mm3, p = 0.006], and increased cup area [tocilizumab: 0.08 (−0.01, 0.16) mm2, p = 0.010; rituximab: 0.07 (0.01, 0.12) mm2, p = 0.019; azathioprine: 0.14 (0.02, 0.26) mm2, p = 0.023]. However, we detected no significant differences in annual changes in mGCC, pRNFL, TMV, and cup area between patients with tocilizumab, rituximab, and azathioprine in NMOSDON+ eyes. NMOSDON− eyes did not display mGCC or pRNFL thinning in patients treated with tocilizumab and rituximab. Intriguingly, we observed significant thinning of mGCC in patients treated with azathioprine compared with tocilizumab [−0.84 (−1.50, −0.18) μm vs. −0.19 (−0.87, 0.48) μm, p = 0.012] and rituximab [−0.84 (−1.50, −0.18) μm vs. −0.07 (−1.25, −2.51) μm, p = 0.015] in NMOSDON− eyes.Conclusions: This study demonstrated that retinal ganglion cell loss is independent of ON attacks in NMOSD. Tocilizumab and rituximab may delay mGCC thinning in NMOSDON− eyes compared with azathioprine.

Background and ObjectivesTo assess the molecular landscape of B-cell subpopulations across different compartments in patients with neuromyelitis optica spectrum disorder (NMOSD).MethodsWe performed B-cell transcriptomic profiles via single-cell RNA sequencing across CSF, blood, and bone marrow in patients with NMOSD.ResultsAcross the tissue types tested, 4 major subpopulations of B cells with distinct signatures were identified: naive B cells, memory B cells, age-associated B cells, and antibody-secreting cells (ASCs). NMOSD B cells show proinflammatory activity and increased expression of chemokine receptor genes (CXCR3 and CXCR4). Circulating B cells display an increase of antigen presentation markers (CD40 and CD83), as well as activation signatures (FOS, CD69, and JUN). In contrast, the bone marrow B-cell population contains a large ASC fraction with increased oxidative and metabolic activity reflected by COX genes and ATP synthase genes. Typically, NMOSD B cells become hyperresponsive to type I interferon, which facilitates B-cell maturation and anti–aquaporin-4 autoantibody production. The pool of ASCs in blood and CSF were significantly elevated in NMOSD. Both CD19− and CD19+ ASCs could be ablated by tocilizumab, but not rituximab treatment in NMOSD.DiscussionB cells are compartmentally fine tuned toward autoreactivity in NMOSD and become hyperreactive to type I interferon. Inhibition of type I interferon pathway may provide a new therapeutic avenue for NMOSD.