Longitudinal Dynamics of Gut Microbiota in the Pathogenesis of Acute Graft‐versus‐host Disease

AIM:The gut microbiota has been reported to be associated with acute graft-versus-host disease (aGvHD) in hematopoietic stem cell transplantation (HSCT). Dynamic surveillance of the microbiota is required to understand the detailed pathogenesis involved in the process of aGvHD.METHODS:Fecal samples were collected prospectively at four timepoints, including pre-HSCT (T1), graft infusion (T2), neutrophil engraftment (T3), and 30 days after transplantation (T4). Fecal samples were profiled by 16S ribosomal RNA gene sequencing to assess the microbiota composition.RESULTS:From the T1 to T4 timepoint, the diversity of the gut microbiota decreased, and the dominant species also changed, with a decrease in the obligate anaerobic bacteria and a shift toward a "pathogenic community". Compared with non-aGvHD patients, aGvHD patients had a lower abundance of Roseburia at T1 and a higher abundance of Acinetobacter johnsonii at T2. Furthermore, Acinetobacter johnsonii was negatively correlated with the secretion of IL-4 and TNF-α. At T3, Rothia mucilaginos was demonstrated to be linked with a decreased risk of aGvHD, which was accompanied by decreased secretion of IL-8. At T4, higher abundances of Lactobacillus paracasei and Acinetobacter johnsonii were identified to be related with aGvHD. Lactobacillus paracasei was associated with the downregulation of IL-10, and Acinetobacter johnsonii was associated with the downregulation of IL-2 and TNF-α.CONCLUSIONS:Dynamic changes in gut microbiota composition and related cytokines were found to be related to aGvHD, including pathogenic or protective changes. These findings suggested that manipulation of gut microbiota at different timepoints might be a promising avenue for preventing or treating this common complication.