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Carsten Schmelter, Natarajan Perumal, Sebastian Funke, Katharina Bell, Norbert Pfeiffer, Franz H Grus; Mass spectrometric analysis of novel antibody-peptide sequences in glaucoma.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6018. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is a neurodegenerative disease and one of the leading causes of blindness. In our recent studies, we demonstrated that the neurodegeneration process of retinal ganglion cells is significantly correlated to altered autoantibody profiles in sera of glaucoma patients. Therefore, the main objective of this study was to characterize specific antibody-peptide sequences in sera of glaucoma patients employing mass spectrometry-based proteomics strategies.
Sera were taken from 13 patients diagnosed with primary open-angle glaucoma (POAG, N=13, mean age=60±7) and 15 healthy controls (CTRL, N=15, mean age=56±5). IgG were isolated by anti-Fc (crystallisable fragment) beads and subsequently digested into Fab (antigen-binding fragment) and Fc by papain. Fab was further purified from the digested mixture by anti-Fc beads. In-solution trypsin digestion of Fab was performed and analyzed by liquid chromatography – mass spectrometry (LC-MS) strategies. Peptide identification and label-free quantification (LFQ) were done employing state-of-the-art bioinformatics tools. Identified peptides were aligned to IgG germline sequences using IMGT database (ImMunoGeneTics Information System) and IgBLAST algorithm.
In total we sequenced 1874 heavy and 1672 light chain variable peptides in controls and glaucoma patients with a false discovery rate of < 1%. LFQ analysis identified 37 peptides (p=0.01) to be exclusively expressed in glaucoma patients compared to healthy individuals. Seven of these peptides were annotated as complementarity determining regions (CDR1 and CDR2) whereas the other peptides were mainly located within the framework regions (FR1, FR2 and FR3) of the antibodies.
The present pilot study shows for the first time that novel antibody-peptide sequences are associated to glaucoma. These findings provide further evidence that autoimmunity plays an essential role in the degeneration process of retinal ganglions cells. Nevertheless, it remains elusive how exactly these changes in the antibody-peptide composition influence the pathomechanism of glaucoma. Further studies will be needed focus on the participation of immunological processes in neurodegenerative diseases.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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