C5 Contributes to Ocular Inflammation in Experimental Autoimmune Uveitis

Abstract

Purpose : Complement has been implicated in ocular inflammation. The present study was undertaken to evaluate the role of C5 in experimental autoimmune uveitis (EAU). We used both genetic (C5 KO, C3/C5 double KO mice), and pharmacologic (anti-C5 antibody) experimental approaches.

Methods : Adult C57BL/6J mice (n=25), C5 KO (n=13) and C3/C5 KO (n=8) mice (Regeneron Pharmaceuticals Inc.) were used. EAU was induced by subcutaneous injection of human interphotoreceptor retinoid-binding protein peptide (IRBP, New England Peptide) in complete Freund’s adjuvant and intraperitoneal injection of pertussis toxin. Anti-mouse C5 mAb or isotype control mAb was administered through S.C injections every 3 days from day 5 to 28 post-IRBP. The SPECTRALIS HRA+OCT was used to assess levels of inflammation on days -1, 7, 14, 21 and 28. All animals were euthanized on day 28 and eyes and blood recovered. Hemolysis assays were performed with the recovered serum to assess in vivo complement inhibition. Data were analyzed by ANOVA.

Results : Compared to wild type mice, inflammation incidence (30-50%) and vitreous cell cluster counts were significantly decreased in C5 KO mice (p<0.01). OCT scores in C5 KO mice also significantly reduced 50% at week 3 (p<0.0001). Interestingly, in C3/C5 double KO mice, there were significantly more vitreous cell clusters and higher disease scores on day 28 compared to wild type mice (p<0.05). In animals that received anti-C5 Ab (50mg/kg), inflammation incidence and vitreous cell clusters were significantly lower compared to either no treatment or isotype control on day 21 (p<0.01). At week 3 and 4, OCT scores in anti-C5 Ab (50mg/kg) group were significantly lower compared to no treatment or isotype control (p<0.0001). Hemolysis assays confirmed the inhibition by anti-C5 Ab at week 4.

Conclusions : Ocular inflammation due to EAU was mitigated by inhibiting C5 activity, either by genetic deletion or pharmacologic inhibition with a specific monoclonal antibody. These results indicate that C5 is a potential therapeutic target for autoimmune uveitis.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.