Gut microbial interaction networks control autoimmunity to neuroretina.

The gut microbiome influences the development of immune-mediated inflammatory diseases. One such condition is autoimmune uveitis, a sight-threatening ocular inflammation driven by retina-specific T cells1. Using a model of spontaneous experimental autoimmune uveitis (sEAU) we showed that gut commensals provide innate and adaptive immune stimuli that trigger the disease2. Here we report that uveitis-promoting microbes are present in human gut flora and that colonization of germ-free (GF) mice with commensal flora from healthy human donors was sufficient to provoke disease. Severity of sEAU correlated with expansion of Akkermansia and contraction of short-chain fatty acid (SCFA)-producing Firmicutes, as well as decreased SCFA levels and a dominant gut Th1 effector response. Mechanistic gain-of-function experiments, enriching GF sEAU mice with Akkermansia, reproduced these microbiome, metabolite and immune phenotype shifts, and exacerbated disease. We propose that Akkermansia promotes autoimmunity by outcompeting SCFA-producers and enhancing Th1-type responses. Notably, an inverse correlation between Akkermansia (Verrucomicrobia) and Firmicutes was also present in fecal microbiome of patients with uveitis, multiple sclerosis and Crohn's disease. These findings reveal a stereotypic gut microbial interaction network that regulates systemic immune balance, and may represent an ecologically conserved mechanism through which the gut microbiome modulates autoimmune and inflammatory diseases.