Auto-Antibodies as Serum Biomarkers for Age-Related Macular Degeneration

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DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is characterized since its earliest stages by formation of deposits between the Bruch's membrane (BM) and the retinal pigment epithelium (RPE), termed drusen. In recent years, a role for inflammation in the pathogenesis of both AMD in general and drusen in particular has been established at the biological, experimental, and genetic level. Drusen have high contents of inflammatory effectors and by-products, and dendritic cells (DCs) from the choroid (Ch), which are among the resident antigen-presenting cells of the eye, are recruited to and infiltrate the BM and drusen cores. With these premises, and based on evidence from the literature indicating that AMD patients have a higher frequency of circulating antibodies directed against antigens not only of Ret, but also of BM/Ch and RPE origin than in controls, we hypothesize that auto-antibodies (Auto-Abs) are biomarkers relevant to ocular disease status and that they will be measurable in the serum of AMD patients. To test the basic tenet of this hypothesis, the Aim of this proposal is to analyze serum samples collected from participants with (n=188) and without (n=222) AMD. Of these, 108 of the AMD subjects and the 222 unaffected individuals (mean age: 79 years old) are participants in the ARMA Study, a study ancillary to Health ABC conducted by the P.I. during his K23 Award. Additional 80 subjects with advanced AMD will be recruited during this award. Serum samples collected at the time of examination will be screened for the presence of auto-Abs directed against macula-specific Ret, RPE, and BM/Ch homogenates generated from fresh tissues dissected from human donors eyes. Homogenate proteins reacting against serum auto-Abs will be immunoprecipitated and separated on 2D gels. The identity of the most common gel spots observed uniquely and/or more intensely in AMD samples will be preliminarily characterized by mass spectrometry. Based on our overall rationale, we predict that sera from AMD patients will show higher frequency of auto-Abs than control subjects not only against Ret, but also and especially against RPE and/or BM/Ch antigens. If our hypothesis will prove correct, in a subsequent R01 application we plan to test the additional hypotheses that (1) within the group of patients with AMD, anti-Ret, anti-RPE, and/or anti-BM/Ch auto-Abs will be seen more often in subjects harboring disease-predisposing genetic variants, and that (2) patients with advanced AMD will have a higher frequency of auto-Abs than patients with early-stage AMD. We further plan to (3) characterize in detail all the identified auto-antigens towards which the auto-Abs are directed by mass spectrometry and (4) localize their expression at the tissue level by conducting immunohistochemistry experiments on macular section from human donor eyes. We predict that, ultimately, this line of research will provide us with useful biomarkers to elucidate further at the tissue level the pathways involved in AMD, and to identify potential prognostic and therapeutic targets.