Spontaneous Translocation Of A Human Enterococcal Gut Pathobiont Drives Systemic Autoimmunity

Abstract Host-microbiota interactions in the pathogenesis of autoimmunity remain poorly understood. Here, we show that a gut commensal, Enterococcus gallinarum, reaches lymphocytes beyond the gut barrier in the mesenteric lymph node, liver and spleen of lupus-prone (NZWxBXSB)F1 mice. Oral vancomycin treatment suppressed growth of E. gallinarum in tissues of these mice, prevented organ manifestations and mortality by lowering pathogenic autoantibodies, Th17 and Tfh cells. Hepatocyte-commensal cocultures revealed induction of the lupus signature cytokine IFN-α as well as the AhR pathway (AhR, Cyp1a1, Cyp1a2) that could be linked to Th17 induction in vivo. E. gallinarum monocolonization in germ-free C57BL/6 animals allowed for translocation to internal organs and induction of autoantibodies as well as increase of lamina propria plasmacytoid dendritic cells (pDCs) and systemic Th17 cells. Additionally, RNA-Seq of short-term ileum E. gallinarum-monocolonized mice demonstrated induction of molecules related to barrier function (occludin, claudins, Plvap, Axin2), the mucus layer (mucin, Fut2), antimicrobial defence (Reg3b, Defa2), and inflammation and pDC induction (AhR/Cyp1a1, Enpp3). Species-specific PCR of sterilely obtained liver tissue from autoimmune hepatitis and lupus patients revealed also E. gallinarum, suggesting similar processes in humans. Accordingly, human hepatocyte-commensal coculture demonstrated production of the same autoimmune-promoting factors as with murine hepatocytes. Collectively, these data indicate that a human pathobiont translocates spontaneously to promote autoimmunity in genetically predisposed hosts, broadening our understanding of autoimmune host-microbiota interactions.