Longitudinal changes of ocular surface microbiome in patients undergoing hemopoietic stem cell transplant (HSCT)

Graft-versus-host disease (GVHD) is the major complication of allogeneic hematopoietic stem cell transplantation (HSCT), which severely impacts survival and quality of life of patients. The gastrointestinal tract is particularly affected by GVHD, and the onset of a dysbiosis of the intestinal microbiota has been demonstrated in these patients, characterized by a diversity loss, a decrease in commensals and an increase in pathogens. Despite its exposition to the external environment, the ocular surface hosts a paucibacterial microbiome mainly composed of three phyla which appears to play a role in regulating immune responses. Ocular manifestations of GVHD (oGVHD) are frequent post-transplant complications that develop in 30-60% of patients after allo-HSCT and 60-90% of patients with acute or chronic systemic GVHD. The aim of this study was to evaluate the possible longitudinal changes of the ocular surface microbiome (OSM) in patients pre- and post-transplant and the relations between OSM characteristics and the development of oGVHD.