Commensal orthologs of the human autoantigen Ro60 as triggers of autoimmunity in lupus

Abstract

The earliest autoantibodies in lupus are directed against the RNA binding autoantigen Ro60, but the triggers against this evolutionarily conserved antigen remain elusive. We identified Ro60 orthologs in a subset of human skin, oral, and gut commensal bacterial species and confirmed the presence of these orthologs in patients with lupus and healthy controls. Thus, we hypothesized that commensal Ro60 orthologs may trigger autoimmunity via cross- reactivity in genetically susceptible individuals. Sera from human anti-Ro60–positive lupus patients immunoprecipi-tated commensal Ro60 ribonucleoproteins. Human Ro60 autoantigen–specific CD4 memory T cell clones from lupus patients were activated by skin and mucosal Ro60-containing bacteria, supporting T cell cross-reactivity in humans. Further, germ-free mice spontaneously initiated anti-human Ro60 T and B cell responses and developed glomerular immune complex deposits after monocolonization with a Ro60 ortholog–containing gut commensal, linking anti- Ro60 commensal responses in vivo with the production of human Ro60 autoantibodies and signs of autoimmunity. Together, these data support that colonization with autoantigen ortholog-producing commensal species may initiate and sustain chronic autoimmunity in genetically predisposed individuals. The concept of commensal ortholog cross-reactivity may apply more broadly to autoimmune diseases and lead to novel treatment approaches aimed at defined commensal species.

A Diet-Sensitive Commensal Lactobacillus Strain Mediates TLR7-Dependent Systemic Autoimmunity

“…Monocolonization with L. reuteri also led to splenomegaly, hepatomegaly (Figure 4E), as well as splenic and ileal type I IFN gene expression (Figure 4F). Hepatosplenomegaly was not seen after monocolonization with an unrelated gut bacterium, B. thetaiotaomicron (BT) (Figure S4G) that mainly triggers cross-reactive adaptive as opposed to innate signals related to autoimmunity (Greiling et al, 2018). L. reuteri- monocolonized mice accumulated more pDCs in spleen and MLN compared to B. thetaiotaomicron (Figures 4G and S4H) and suffered from worsened signs of lupus nephritis (Figures 4H-4J).…”

“…Stool samples were collected from SLE patients (n = 12 females, 18 years of age and older) and sex- and age-matched (±5 years) healthy controls (n = 22) from up to three study visits (baseline, week 4, and week 8). The SLE patient cohort, longitudinal study design, inclusion and exclusion criteria as well as sampling protocol and 16S rDNA sequencing were previously described (Greiling et al, 2018) (ClinicalTrials.gov identifier: NCT02394964). In brief, all patients were diagnosed by a healthcare provider and thoroughly evaluated at each study visit at the Yale Center for Clinical Investigation.…”

“…In brief, all patients were diagnosed by a healthcare provider and thoroughly evaluated at each study visit at the Yale Center for Clinical Investigation. Number of visits, sex, age, race, ethnicity, weight, height, body mass index, autoantibody profile, complete blood counts, kidney function, inflammatory markers, complement levels, constitutional symptoms, cutaneous, mucosal, musculoskeletal, vascular, and neurologic manifestations, immunomodulatory drugs, and adjunctive medications, as well as a detailed dietary history have been captured and were previously described (Greiling et al, 2018). Exclusion criteria were ongoing chronic infection, antibiotic or probiotic use in the last 90 days, topical antibiotic or antimicrobial use in the last 7 days, bathing or tooth brushing in the last 8 hours, major gastrointestinal surgery in the last 5 years, gastrointestinal bleeding history, inflammatory bowel disease, bulimia or anorexia nervosa, morbid obesity, uncontrolled diabetes mellitus, malignancy in the past year, and known excessive alcohol use.…”

“…The model under SPF conditions was similarly applied to the GF setting as previously described (Greiling et al, 2018). Mice under both conditions were followed until 24 weeks of age for survival analysis.…”

“…Filtered operational taxonomic units (OTUs) were rarefied to a depth of 4,000 sequences per sample and OTUs representing less than 0.01% of total abundance were excluded from further analysis. Analysis of human 16S rDNA sequencing data from SLE patients was performed similarly as above, with the exception that OTUs were rarefied to a depth of 10,000 sequences per sample as previously described (Greiling et al, 2018). …”