Abstract
BackgroundRecent evidence implicates antibody responses as pivotal damaging factors in spinal cord injury (SCI)-induced neuroinflammation. To date, only a limited number of the antibody targets have been uncovered, and the discovery of novel targets with pathologic and clinical relevance still represents a major challenge.MethodsIn this study, we, therefore, applied an unbiased, innovative and powerful strategy, called serological antigen selection (SAS), to fully identify the complex information present within the antibody repertoire of SCI patients.ResultsWe constructed a high-quality cDNA phage display library derived from human spinal cord tissue to screen for antibody reactivity in pooled plasma samples from traumatic SCI patients (n = 10, identification cohort). By performing SAS, we identified a panel of 19 antigenic targets to which the individual samples of the plasma pool showed antibody reactivity. Sequence analysis to identify the selected antigenic targets uncovered 5 known proteins, to which antibody reactivity has not been associated with SCI before, as well as linear peptides. Immunoreactivity against 9 of the 19 novel identified targets was validated in 41 additional SCI patients and an equal number of age- and gender-matched healthy subjects. Overall, we found elevated antibody levels to at least 1 of the 9 targets in 51 % of our total SCI patient cohort (n = 51) with a specificity of 73 %. By combining 6 of these 9 targets into a panel, an overall reactivity of approximately half of the SCI patients could be maintained while increasing the specificity to 82 %.ConclusionsIn conclusion, our innovative high-throughput approach resulted in the identification of previously unexplored antigenic targets with elevated immunoreactivity in more than 50 % of the SCI patients. Characterization of the validated antibody responses and their targets will not only provide new insight into the underlying disease processes of SCI pathology but also significantly contribute to uncovering potential antibody biomarkers for SCI patients.
Highlights
Recent evidence implicates antibody responses as pivotal damaging factors in spinal cord injury (SCI)-induced neuroinflammation
Antibody profiling of SCI plasma samples using serological antigen selection (SAS) A high-quality hSC complementary DNA (cDNA) phage display library was generated from human spinal cord tissue of 18 Caucasians
Details of the performed quality controls are described in [23]. These results showed that the hSC cDNA phage display library had a high quality and diversity. This hSC cDNA phage display library was screened for antibody reactivity using a plasma pool consisting of 10 randomly selected traumatic SCI patients (identification cohort; mean age 48 years; Table 1)
Summary
Recent evidence implicates antibody responses as pivotal damaging factors in spinal cord injury (SCI)-induced neuroinflammation. Neuroinflammation is a key process in spinal cord injury (SCI) pathophysiology that can persist for months or even years after primary trauma. In experimental SCI, B cells accumulated in the injured spinal cord, formed follicle-like structures and contributed to aggravated tissue damage [4]. SCI-induced B cell activation culminated in the production of pathologic and central nervous system (CNS)-reactive antibodies which were released in the blood stream and migrated to the lesion [4, 5]. Passive transfer of serum antibodies from SCI mice into naïve/uninjured mice showed that these SCIinduced antibodies participated in neuroinflammatory responses and exerted a degenerative effect in the spinal cord by causing cell death and sustained neurological dysfunction [4, 5]. A proteomics study on spinal cord tissue in mice indicated that more than 50 different proteins were targeted by antibodies after SCI; up to now, only glutamate receptor 2/3 and nuclear antigens have been described as antibody targets in SCI models [4, 6]
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