Vitamin A and D Supplementation in Allogeneic HCT

Currently there is an emerging evidence of gut microbiota role in major complications of HCT, including GVHD, oral mucositis, infectious complications due to multi-drug resistant bacteria in the gut. Early exhaustion of most intestinal bacterial phyla after HSCT is documented in many studies. This effect of intensive anti-infectious therapy is well known. Most authors explain the disruption of intestinal microbiota by massive antibiotic treatment in order to prevent infectious complications due to immune deficiency following HCT. Early decrease in anaerobic bacteria (phylum Firmicutes) is revealed in many studies, with subsequent recovery of these bacterial populations within next 2 months. This time dynamics is in accordance with reported data on depletion of certain anaerobic gut bacteria, e.g., Ruminococcus, Faecalibacterium spp., Roseburia, Blautia post-transplant, being associated with severe complications in HCT patients. These results are in accordance with severe posttransplant dysbiosis at different mucosal sites post-HCT, as shown elsewhere by routine bacteriology techniques. The metabolism of bacteria with positive effect on GVHD includes both vitamin D and vitamin A. It was demonstrated that Ruminococcus abundance is dependent on vitamin A and D intake. Another bacteria genera Faecalibacterium prausnitzii, which is also reported to produce butyrate and reduce GVHD is also dependent on abundance of vitamin A. The big phylum Firmicutes are also dependant on vitamin D and their abundance is reported to be associated with lower incidence of immune complications and suppression of antibiotic-resistant strains. To summarize the idea of the study is based on modulation of gut microbiota, which in term may result in lower incidence of GVHD and toxic complications of HCT.