Identification of eye-homing peptides and their use for targeted liposomal drug delivery in posterior uveitis

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Human posterior segment uveitis of autoimmune origin is a chronic disease that can impair vision and result in blindness. A variety of autoantigens, including interphotoreceptor retinoid binding protein (IRBP), have been implicated in uveitis pathogenesis. The T cells reactive against these antigens access the eye through the blood-retinal barrier and cause local inflammation and tissue damage. Two of the main challenges in non- infectious posterior uveitis are – 1) to define the molecular changes induced during uveitis in endothelium of the choroidal and retinal vasculature, and 2) to devise novel ways to direct the systemically-administered drugs primarily into the eye to enhance their efficacy but minimize adverse effects. We hypothesize that the vascular endothelium of the eye in uveitis is characterized by unique molecular markers that facilitate both selective migration of the pathogenic T cells into the target organ and cellular interaction with the inducers/ mediators of inflammation and tissue damage. Accordingly, the identification of peptide ligands (by phage peptide library screening) that interact with such markers would be invaluable tools to study disease pathogenesis. Furthermore, these peptide ligands can be exploited for targeted drug delivery to the eye with the objective of enhancing efficacy, but reducing systemic toxicity of those drugs. In collaboration with Dr. Erkki Ruoslahti (Sanford-Burnham, La Jolla), who pioneered the concept of vascular ‘address molecules’ or ‘zip codes’, we published a study on the molecular profiling of the synovial vasculature in adjuvant arthritis in rats (PNAS 2011). We identified unique joint-homing peptide ligands using an innovative approach of ex vivo/ in vivo enrichment of clones from a phage peptide-display library. Recently, we also reported CNS-homing peptides in the EAE model of human multiple sclerosis. The advantage of using phages to detect tissue-specific markers is that there is no a priori bias in predicting the peptide sequences/motifs. And, unlike antibodies, phage peptides interact with functional domains of target molecules. We now plan to apply this methodology to rat experimental autoimmune uveitis (EAU). The aims of our study in collaboration with experts in EAU (Dr. Caspi and Dr. Sun), [in vascular biology (Dr. Teesalu from Ruoslahti group), and in pharmacodynamics (Dr. Swaan)] are: Aim 1. To identify peptide ligands homing to the diseased eye in EAU using the ex vivo/ in vivo screening of phage peptide library. (a) To identify unique peptide-encoding phages that home to the vasculature and retina of the diseased eye; and (b) to determine the relative specificity of select phages/ peptides [for other tissues within the eye as well as other organs in EAU versus control (healthy/EAE) rats.] Aim 2. To use the eye-homing peptides for targeted drug delivery to the diseased sites in EAU. To use a specific peptide to guide liposomes encapsulating a drug (e.g., methotrexate) [to the diseased sites in eyes in EAU, and compare the pharmacodynamics and safety of that drug] with that using plain liposomes or free drug. The results would advance understanding of pathogenesis of human uveitis and designing of novel therapies.