Does human microbiota interact with immunosuppressive treatment of systemic autoimmune rheumatological diseases? A...

To collect and analyse studies evaluating the interaction between the human microbiota (HM) and immunosuppressive (IS) treatments for systemic autoimmune rheumatological diseases (ARDs), and their impact on the disease.

A systematic review was performed based on an electronic search strategy in Medline, Embase, and Cochrane Library (inception-02/2024). We included papers studying the interaction of HM and IS treatments in adult patients with ARDs in which parameters of diversity and taxonomic composition were measured. We excluded spondyloarthritis for which more extensive knowledge is available. Studies of any language were allowed, prioritising clinical trials but also including observational longitudinal prospective and retrospective, and case-control studies.

Of 2570 papers identified, 20 were included (15 from rheumatoid arthritis, 3 from systemic lupus erythematosus, 1 from primary Sjögren's syndrome and 1 from systemic sclerosis), overall, with a moderate risk of bias. The paucity of studies and niche specificity limited the study to the gut microbiota. A trend towards decreased diversity and compositional changes in gut microbiota and partial restitution in patients responding to IS treatment was identified. The heterogeneity observed in the design and outcome measures of the studies precluded a metaanalysis; however, the results point to a possible relationship between HM alterations and response to IS treatments in ARDs.

Available studies suggest a potential association between the HM and the response to IS therapies in ARDs. However, the overall moderate quality of evidence and substantial methodological heterogeneity limit the strength of combined conclusions. Standardization of microbiota-related studies is needed to enable data integration and support more robust inferences.