The importance of the intestinal microbiome for graft-versus-host disease (GvHD) after allogeneic hematopoietic cell transplantation (allo-HCT) was initially demonstrated both in preclinical and clinical studies several decades ago. Since then major advances in microbiome research have resulted in a better understanding of the interplay between microbiome and host in health and disease.  This session will address various aspects of the role of the intestinal microbiome in patients with hematological malignancies (especially allo-HCT recipients), including novel methodologies to study interactions between microbiome and host, preclinical and clinical studies regarding the intestinal microbiome and GvHD and the clinical potential of fecal microbiota transplant in allo-HCT patients.

Dr. Ami Bhatt will discuss how alterations in the human gut microbiome are correlated with disease prognosis, treatment response, and complications of therapy in patients with hematologic disorders. Recently developed technologies and bioinformatic approaches have enabled us to understand the mechanisms that might underlie these interactions. By understanding microbes at the strain level and defining the macromolecules that microbes use to communicate with one another and the host, her lab hopes to characterize the rich signaling interface between microbes in humans. In so doing, it is anticipated that modifying and eventually controlling this type of signaling could help improve patient outcomes.

Dr. Marcel van den Brink will discuss preclinical and clinical studies demonstrating the role of changes in the intestinal microbiota of recipients of allo-HCT and its effects on GvHD, as well as infections, relapse and engraftment.

Dr. Mette Hazenburg will discuss how disruption of the intestinal microbiome is a key element of GvHD pathophysiology. This has led to the hypothesis that with fecal microbiota transplantation (FMT) the damaged microbiome can be repaired by FMT, and that reparation of the microbiome may cure GvHD. By inference, it can be hypothesized that reconstitution of a healthy microbiome before or shortly after allogeneic HCT by FMT could prevent severe GvHD. In this presentation, both hypotheses will be addressed, based on the literature available and also including Dr. Hazenburg’s own data on FMT in steroid-refractory patients.