Weizmannia coagulans BC99 alleviates pediatric allergic rhinitis via the gut microbiota-SCFAs- immunomodulatory axis: A randomized, double-blind, placebo-controlled trial.

BACKGROUND

Allergic rhinitis (AR) is a prevalent global health issue. This trial evaluated the efficacy and mechanisms of Weizmannia coagulans BC99 (W. coagulans BC99) in managing pediatric AR.

METHODS

In this randomized, double-blind, placebo-controlled trial, 52 children with AR received either W. coagulans BC99 (2 × 109 CFU/day) or a placebo for 8 weeks. The trial was registered at ClinicalTrials.gov (NCT06676111). Rhinitis Control Assessment Test (RCAT) and Rhino-conjunctivitis Quality of Life Questionnaire (RQLQ) scores, inflammatory biomarkers, gut microbiota (16S rRNA sequencing), and fecal short-chain fatty acids (SCFAs) were assessed at baseline and endpoint.

RESULTS

BC99 supplementation significantly improved RCAT and RQLQ scores compared to the placebo (p < 0.01), indicating better symptom control and quality of life. It also significantly reduced serum levels of IgE, IL-4, IL-13, and TNF-α while increasing IFN-γ and the IFN-γ/IL-4 ratio (p < 0.05). Gut microbiota analysis revealed that BC99 increased the abundance of beneficial SCFAs-producing genera (e.g. Bifidobacterium, Roseburia) and decreased pro-inflammatory genera (e.g. Escherichia-Shigella, Collinsella). This microbial shift was associated with elevated fecal concentrations of acetic acid, butyric acid, and isovaleric acid. Correlation analysis further strengthened the gut-immune link, showing positive associations between beneficial bacteria and SCFAs, and between harmful bacteria and inflammatory mediators. Functional prediction indicated that BC99 influenced key metabolic pathways, including enhanced PPAR signaling and purine metabolism. The intervention was well-tolerated with no adverse events reported. Our findings elucidate a novel gut-immune pathway through which W. coagulans BC99 exerts its anti-allergic effects, supporting its potential as a probiotic-based immunomodulatory strategy for AR.

CONCLUSION

W. coagulans BC99 alleviates AR in children by modulating the gut microbiota, increasing SCFAs production, and subsequently rebalancing the level of inflammatory cytokines, highlighting its potential as a novel probiotic therapy for AR. These findings underscore the potential of BC99 as a probiotic therapy targeting the gut-immune axis, offering a novel strategy for managing AR.