Azzouz, D. F. | Search bioRxiv

bioRxiv2022

Lupus disease flares are concordant with immune responses to blooms of lipoglycan-expressing Ruminococcus blautia gnavus strains arising from unstable gut microbiota communities

Whereas genetic susceptibility for Systemic Lupus Erythematosus has been well explored, the precipitants for clinical disease flares remain a mystery. To investigate for dynamic-relationships between gut-microbial communities and Lupus disease activity, we performed taxonomic surveys of fecal 16S rRNA gene amplicon-libraries from Lupus patients and healthy volunteers, obtained at serial timepoints over many months to several years. Individual Lupus patients commonly displayed imbalances in alpha and beta microbiota-diversity, which were uniquely different from healthy individuals as well as from other Lupus patients. Moreover, multivariate analysis of sequential Lupus libraries documented community-wide ecological microbiota instability overtime, most pronounced in patients with Lupus Nephritis LN), a severe form associated with worse prognosis. Lupus gut communities displayed transient spikes of pathogenic bacterial species, with by far the most prevalent being blooms of Ruminococcus blautia gnavus (RG), occurring in nearly half of LN patients often concordant with disease activity flares. RG strains isolated during disease flares, but not those isolated from healthy individuals or patients with inflammatory bowel disease, commonly expressed a novel, highly immunogenic cell wall-associated lipoglycan with conserved structural features that include a diacyl glycerol anchor. Cross-reactive antigenic determinants on these lipoglycans were recognized by murine monoclonal antibodies, and by spontaneously arising Lupus serum IgG antibodies with peak serum antibody responses also concordant with RG blooms. As SLE is frequently characterized by remitting-relapsing disease, despite appropriate treatment, we speculate that gut blooms of pathogenic bacteria, that impair gut barrier function and stoke systemic inflammation, directly contribute to immunopathogenesis.

immunology↗

bioRxiv2021

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.

microbiology↗