Abstract

SA.16.09

Is it possible to cause retinal ganglion cell loss through immunization with heat shock protein and how does this influence the antibody profile?

Joachim S. C.¹, Wuenschig D.¹, Wax M. B.², Pfeiffer N.¹, Grus F. H.^1 
1Experimental Ophthalmology, Department of Ophthalmology, Johannes Gutenberg University, Mainz, Germany, ²Alcon Research, Ltd., Fort Worth, Texas, USA

Objective: Antibodies against heat shock protein 27 (HSP27) have been identified in sera of glaucoma patients. The aim of this study was to analyze if immunization with HSP27 can cause retinal ganglion cell loss in rats and analyze changes in antibody profiles.
Methods: Rats were immunized with 100 μg HSP27 and euthanized after 6 weeks (n=8). Control animals that received no immunization were also euthanized after 6 weeks (n=9). Intraocular pressure (IOP) was measured in all animals before and 2 and 4 weeks after immunization. Blood was collected at different time points: before immunization and 2, 4, and 6 weeks after. A Protein G bead approach followed by ProteinChip techniques (Seldi-TOF) was used to detect IgG antibody profiles against retinal antigens in sera. The antibody patterns were analyzed by multivariate statistical techniques. Eyes were harvested and flatmounts were stained with Brn-3a to detect retinal ganglion cell (RGC) nuclei. We used a computer assisted quantitation of the RGC density.
Results: No significant changes in IOP were observed during the course of the study. After 6 weeks the immunized group showed a lower number of RGCs comparison to controls (approx. 30% loss, P<0.05). All sera showed complex IgG antibody profiles. Immunized animals showed significantly increased antibody reactivity against HSP27 and significant up- and down-regulations of antibody reactivity in other regions. Using multivariate statistical methods we demonstrated a significant difference between antibody patterns before and 2 weeks after immunization (P=0.009) as well as between patterns before and 4 weeks after immunization (P=0.0004).
Conclusions: After immunization with HSP27, animals developed strong antibody reactivities against HSP27, which led to significant loss of retinal ganglion cells. In glaucoma patients previous studies could demonstrate specific antibody profiles. Similar to our findings in patients immunized animals did also develop complex profiles. Thus, immunization with ocular antigens like HSP27 might be a promising approach to understand autoimmune mechanisms involved in glaucoma.
Supported by Böhringer Ingelheim Foundation

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