Prevotella copri in individuals at risk for rheumatoid arthritis

Rheumatoid arthritis (RA) has been associated with a relative expansion of faecal Prevotellaceae. To determine the microbiome composition and prevalence of Prevotella spp. in a group of individuals at increased risk for RA, but prior to the development of the disease.In an ongoing cohort study of first-degree relatives (FDRs) of patients with RA, we identified 'FDR controls', asymptomatic and without autoantibodies, and individuals in pre-clinical RA stages, who had either developed anticitrullinated peptide antibodies or rheumatoid factor positivity and/or symptoms and signs associated with possible RA. Stool sampling and culture-independent microbiota analyses were performed followed by descriptive statistics and statistical analyses of community structures.A total of 133 participants were included, of which 50 were categorised as 'FDR controls' and 83 in 'pre-clinical RA stages'. The microbiota of individuals in 'pre-clinical RA stages' was significantly altered compared with FDR controls. We found a significant enrichment of the bacterial family Prevotellaceae, particularly Prevotella spp., in the 'pre-clinical RA' group (p=0.04).Prevotella spp. enrichment in individuals in pre-clinical stages of RA, before the onset of RA, suggests a role of intestinal dysbiosis in the development of RA.