Immunoglobulin-Derived Peptides Are a Source of Novel Antigen-Specific Markers for Paraneoplastic Neurological Syndromes (P06.002)

Abstract

Objective: The study objective is to demonstrate in patient samples that immunoglobulin-derived peptides can be markers for auto-immune conditions such as paraneoplastic neurological syndromes (PNS). Background In earlier work, it was shown that the antigen specificity of immune sera can be distinguished by the proteomic analysis of immunoglobulins from immunized animals. It is hypothesized that the sequence of the antigen binding sites converges to a similar subset in individuals exposed to a given antigen. The human population is genetically and environmentally much more diverse than laboratory animals. We therefore tested our approach in patients with PNS, a well-characterized auto-immune disorder. Design/Methods: The patient cohorts consisted of 20 patients with PNS associated with the anti-HuD antibodies (Hu-PNS), 20 patients with Yo-PNS, 10 patients with amphiphysin-PNS and 10 patients with CV2-PNS. Antigen-specific immunoglobulins were collected by affinity enrichment on beads coated with recombinant antigen. These immunoglobulins were digested and analyzed by nano-LC and mass spectrometry. From the resulting dataset, peptides were identified that uniquely identified one of the patient groups, and the peptide sequence was deduced from fragmentation spectra. Results: In the mass spectrometry dataset we identified 28 specific and unique peptides; 0 specific for amphiphysin, 2 specific for CV2, 11 for HuD and 15 for Yo. Several marker peptide sequences showed homology to known immunoglobulin sequences, and no relations were found to other known proteins from the NCBInr protein database. Conclusions: The data show that immunoglobulin-derived biomarkers can indeed be found in samples from patients. After validation of these results, we will apply this technique to auto-immune disorders that are difficult to diagnose using conventional techniques. Disclosure: Dr. vanDuijn has nothing to disclose. Dr. Maat has nothing to disclose. Dr. Dekker has nothing to disclose. Dr. Luider has nothing to disclose. Dr. Sillevis Smitt has nothing to disclose.