Background/Purpose: Anti-Ro60 autoantibodies are present in asymptomatic individuals years before onset of disease. We hypothesize that differences in autoreactivity-inducing commensal abundances may drive progression to autoimmune diseases such as SLE. This study tests whether gut pathobionts associate with disease outcome in high titer anti-Ro⁺ women of children with neonatal lupus.

Methods: The study included 25 healthy controls and 85 anti-Ro⁺ mothers recruited from the Research Registry for Neonatal Lupus (RRNL); the RRNL consisted of 27 asymptomatic or undifferentiated autoimmune syndrome (UAS) (incomplete) and 58 Sjögren’s Syndrome and/or ACR/SLICC SLE (complete), and 77 SLE patients (non-RRNL, recruited from NYU Specimen and Matched Phenotype Linked Evaluation (SAMPLE)). The rheumatologic diagnoses of the RRNL women were independently determined by two rheumatologists via questionnaire, telephone, and/or in-person history/physical exam, and review of medical records. After extraction of host and non-host genomic DNA from stool, the microbiome was assessed using 16S rRNA gene amplification using standard protocols (mean of 20k sequences per sample). Operational taxonomic units (OTUs) were identified by closed-reference OTU-picking using Green Genes as reference. Shannon’s index (H’) and relative abundance were tested for differences using the Kruskal-Wallis tests. To adjust for multiple comparisons, tests of lower taxa required significance at all higher taxonomic levels, similar to a Fisher’s protected least significant multiple comparisons procedure.

Results: H’ was different for phylum (p=0.0023), class (p<0.0001) and order (p<0.0001), but not family (p=0.62), between controls, RRNL and SLE (non-RRNL). For these three taxonomic levels, the non-RRNL SLE cases had greater diversity than either the controls or RRNL subjects. The strongest differences in relative abundance were for multiple subtaxa of the phylum Firmicutes (p=5.9x10E-4). Within Firmicutes, class Closteridia (p=9.3x10E-6), order Closteridiales (p=9.3x10E-6) show the strongest differences in mean abundance (controls 0.727, RRNL 0.717, SLE (non-RRNL) 0.620). Multiple families within Closteridiales showed significant differences (p<0.01) with Peptostreptococcaceae exhibiting the strongest statistical evidence (mean abundance controls 0.0248, RRNL 0.0303, SLE (non-RRNL) 0.0117; p=3.2E-07). Within RRNL, the complete and incomplete groups had comparable abundances at the order level (complete 0.7156, incomplete 0.7158), suggesting the primary distinction is with non-RRNL SLE cases.

Conclusion: Non-RRNL SLE showed significant increases in fecal diversity and significant reduction in relative abundance at multiple taxa compared to high titer anti-Ro RRNL subjects who in aggregate more closely resemble healthy subjects. Fecal microbiome differences between preclinical and established disease may provide insight regarding anti-Ro positivity and the progression to complete SLE.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/commensal-gut-bacteria-of-anti-ro-positive-mothers-of-children-with-neonatal-lupus-in-aggregate-resemble-healthy-subjects-without-overt-dysbiosis-of-abundance-of-microorganisms/