Severity of Experimental Autoimmune Uveoretinitis (EAU) is Reduced in Germ-Free Mice

Abstract

Purpose: The gut microbiome is now recognized as an important regulatory element in immunological homeostasis and autoimmunity. The aim of our study is to evaluate the impact of a reduced microbial environment in the model of IRBP-peptide induced EAU in gnotobiotic mice i.e. mice bred in germ free conditions.

Methods: EAU was induced in C57BL/6 mice by subcutaneous inoculation of 500 ug IRBP (interphotoreceptor retinoid binding protein) in complete Freund’s adjuvant and intraperitoneal application of pertussis toxin. Severity of disease was compared in 4 study groups: (a) germ-free mice (14 eyes) (b) conventionally- housed (c-h) mice in which EAU was induced using sterile reagents (38 eyes) (c) c-h EAU mice treated with antibiotics (metronidazole and cetirizine) in the drinking water, (32 eyes) and (d) c-h EAU mice induced using standard reagents (50 eyes). Histological grading of EAU was performed at day 35 post induction on a scale of 0 (no inflammation) to 4 (severe inflammation).

Results: When compared to control mice, in germ-free mice the inflammation was significantly lower (p = 0,007). The median of inflammation intensity reaches in germ-free mice grade 1 compared to grade 2 in control group. The mice induced with sterile chemicals did not show a significant difference in inflammation intensity when compared to the control group (p = 0,564) nor was there a statistically significant difference in inflammation intensity between control mice and mice treated with antibiotics in drinking water.

Conclusions: In this study we have confirmed that germ-free mice developed less severe intensity of EAU. Our results also show that exposure to microbial material, in addition to the mycobacteria and CFA and the pertussis toxin as used in the standard induction protocol does not influence the severity of EAU. This study demonstrates a close link between the microbiome and experimental autoimmune uveoretinitis.