Sex-dependent Lupus Ruminococcus blautia gnavus strain induction of zonulin-mediated intestinal permeability and autoimmunity

Imbalances in the gut microbiome are suspected as contributors to the pathogenesis of Systemic Lupus Erythematosus, and our studies and others have documented that patients with active Lupus nephritis have expansions of the obligate anaerobe, Ruminococcus blautia gnavus (RG). To investigate whether the RG strains in Lupus patients have in vivo pathogenic properties, we colonized C57BL/6 mice with individual RG strains from healthy adults or those from Lupus patients. These strains had a similar capacity for murine intestinal colonization, in antibiotic-preconditioned specific-pathogen-free, as well as germ-free adults, and their neonatally colonized litters. Lupus-derived RG strains induced high levels of intestinal permeability that was significantly greater in female than male mice, whereas the RG species-type strain (ATCC29149/VPI C7-1) from a healthy donor had little or no effects. Lupus RG strain-induced functional alterations were associated dysregulated occluden transcript production in the ileal wall as well as raised serum levels of zonulin, a regulator of tight junction formation between cells that form the gut barrier. Notably, the level of Lupus RG-induced intestinal permeability was significantly correlated with serum IgG anti RG cell-wall lipoglycan antibodies, and to anti-native DNA autoantibodies that are a biomarker for SLE. Strikingly, gut permeability was completely reversed by oral treatment with larazotide acetate, an octapeptide that is a specific molecular antagonist of zonulin. Taken together, these studies document a molecular pathway by which RG strains from Lupus patients induce a leaky gut and autoimmunity that have been implicated in the pathogenesis of flares of clinical Lupus disease.