The effect of microbiota in allogeneic stem cell transplants: Engraftment and GVHD

After allo-hematopoietic stem cell transplantation (HSCT), alloreactive donor T cells can attack target organs and hematopoietic system of the host, including skin, liver, intestine, thymus, central nervous system, ovary or testis, resulting in acute graft-versus host disease (aGVHD) is called. A large number of microorganisms, often called the "microbiota", have been colonized in the human body. It is known that the microbiota changes depending on the drug treatments used with Allo-HSCT and that the microbiota is an important regulator of the disease during the development of aGVHD. 25 patients/donors who had HSCT were included in the study. It was found that 16% of the patients developed relapse or aGVHD. HLA (Human Leukocyte Antigen), alleles detected with high frequency in recipients and donors; It is HLA-A*02:01, B*51:01, -C*06:02, -DRB1*15:01,-DQB1*03:01. Firmicutes phylum constituted 70% of the donors' gut microbiota, while Bacteriodetes phylum constituted 24%. It was determined that 63% of the pre-transplant intestinal microbiota of the patients was Firmicutes phylum, and 54% of the post-transplant intestinal microbiota was Firmicutes phylum. When the stool sample taken before Allo-HSCT was compared with the stool sample taken after engraftment, Roseburia (p=0,01), Bifidobacterium (p=0,05), Faecalibacterium (p=0,04) and Dorea (p=0,05) was observed to be a statistically significant decrease in breeds. An raise in Enterococcus (p=0,3) genus was observed in patients who developed aGVHD following Allo-HSCT, and an raise in Klebsiella (p=0,4) genus was observed in patients with broad-spectrum beta-lactamase (GBSL) positive, but no statistical significance was found. In this thesis study, the microbiota and flora differences between the donor/receiver were examined. In addition, the relationship of fully compatible HLA donors with the microbiota has been revealed.