Synthetic polyclonal-derived CDR peptides as innovative strategy in glaucoma therapy

The pathogenesis of glaucoma is strongly associated with the occurrence of autoimmune-mediated loss of retinal ganglion cells (RGCs) and recently it was proven that specific antibody-derived signature peptides are significantly differentially expressed in sera of primary open angle glaucoma patients (POAG) compared to healthy controls. Synthetic antibody-derived peptides are known since several years to modulate various effector functions of the immune system and to act as antimicrobial or antiviral molecules. The present study shows for the first time that polyclonal-derived complementarity-determining regions (CDRs) significantly increased the survival rate of RGCs in an ex vivo glaucoma model (P=0.013) by using immunohistochemical staining techniques. Affinity capture experiments verified serine protease HTRA2 (mitochondrial) as high-confident retinal epitope target of CDR1 sequence motive ASGYTFTNYGLSWVR. Quantitative proteomic analysis of the CDR-treated retinal explants revealed increased expression of various anti-apoptotic and anti-oxidative proteins (e.g. VDAC2 and TXN) compared to untreated controls (P<0.05) and decreased expression levels of cellular stress response markers (e.g. HSPE1 and HSP90AA1) were observed. Mitochondrial dysfunction, protein ubiquitination pathway and oxidative phosphorylation were annotated as the most significantly affected signaling pathways and can possibly be traced back to the CDR-induced inhibition or modulation of the master regulator HTRA2. These findings emphasize the great potential of synthetic polyclonal-derived CDR peptides as therapeutic agents in future glaucoma therapy and provide an excellent basis for affinity-based biomarker discovery purposes.