Microbiota long-term dynamics and prediction of acute graft-versus-host-disease in allogeneic stem cell transplantation. Ingham et al. (II)

After allogeneic hematopoietic stem cell transplantation for the treatment of hematologic malignancies, the community structure of the stem cell recipient’s microbiota undergoes major shifts. Important knowledge has been acquired concerning changes early after transplantation. However, stronger focus on the subsequent reconstitution of the microbiota is needed. Evaluating the resilience of the commensal community is of importance since it provides a crucial functional repertoire to the human host. This applies not only to the microbiota residing in the gut, but also to other body sites, such as the oral and nasal cavities. For instance, immunomodulatory properties of the microbiotas at these sites might be of relevance locally and systemically in HSCT, but have hitherto not been studied as extensively as the gut in HSCT patients. Here, we have tracked gut, oral, and nasal microbial changes over a period of one year and assessed host-microbe associations at all three body sites. Allogeneic HSCT is often accompanied by side effects, such as bloodstream infections and graft-versus-host disease. Specific gut bacterial taxa are depleted, or expand after HSCT, which has been linked to aGvHD. To advance our knowledge about host immune-microbial associations in HSCT and GVHD towards clinical prognostic applications, we used pre-HSCT gut, oral, and nasal bacterial abundances in machine learning models for the prediction of GvHD severity post-transplant.