Spinal cord reactive-antibodies identified by serological antigen selection show prognostic value in traumatic spinal cord injury patients

Outcome prediction after traumatic spinal cord injury (SCI) remains challenging due to patient heterogeneity, highlighting the need for better prognostic tools. Neural tissue damage and blood-spinal cord barrier disruption expose the immune system to spinal cord proteins, eliciting autoantibody responses that may be beneficial or detrimental. This study aimed to identify the (auto)antibody profile of SCI patients, and examine the prognostic antibody biomarker potential. A healthy and a SCI cDNA phage display library were screened for novel antibodies using SCI samples (n = 12/11). Antibody reactivity was validated using phage ELISA in 291 samples from 190 SCI patients collected at baseline (0-4 days post-injury [dpi]) and follow-up (15-30 dpi; 31-56 dpi). Correlations between antibody reactivity and clinical characteristics including SCI level, and American Spinal Injury Association impairment scale (AIS), were analysed. Immunofluorescent stainings were used to validate expression of two antigenic targets. We identified antibodies against 6 novel autoantigens (University Hasselt [UH.] SCI.104/105/106/108/109/110). A panel of three antigens (UH.SCI.104/109/110) demonstrated increased antibody reactivity in 31.3% of SCI patients with AIS improvement versus 4.8% with no improvement, resulting in a positive likelihood ratio of 6.56. Patients with injuries above thoracic level 4 had significantly lower antibody reactivity against UH.SCI.105/110 compared to patients with lower lesions. Anti-UH.SCI.108/110 antibodies bound to astrocytes, in mouse spinal cord tissue and primary cell cultures, confirming disease-relevant reactivity. Antibodies targeting the novel antigens demonstrated prognostic biomarker potential, supporting their future use in outcome prediction and patient stratification for SCI management and clinical trial design.