Intestinal Microbial Changes During Immune System Reconstruction After Bone Marrow Transplantation

Bone marrow transplantation is a major treatment method for hematologic malignancies and primary immune diseases,and has been widely used in clinical practice.Before undergoing bone marrow transplantation,the patients will receive large doses of radiotherapy and chemotherapy,which cause damage to the human intestine,reduce the host immune defense ability and furthermore develop a variety of infections.After bone marrow transplantation,the immune system reconstructs.During the reconstruction of the immune system,there are also reconstruction problems in the composition of the intestinal microflora.In this study,the changes of the composition of the intestinal microflora during immune system reconstruction after bone marrow transplantation were studied,in order to analyze the correlation between immune system reconstruction and intestinal microbial reconstitution after bone marrow transplantation,providing theoretical support for clinical.In this study,feces from donors and bone marrow transplant patients were used as experimental materials,and four periods were selected: beforepretreatment,two weeks post transplantation,four weeks post transplantation and six weeks post transplantation.The high-throughput sequencing technology was used to sequence donor and patient fecal samples at different times,on the basis of OTU,the intestinal microbial community was analyzed by α-diversity,community composition,and differences between sample groups.The results showed that,compared with healthy donors,the microbial diversity is decreasedbefore pretreatment,the diversity of gut microbial is lowest at two weeks post transplantation,the diversity of gut microbial is increased at four weeks post transplantation,and the diversity at six weeks after transplantation approached before pretreatment.Further analysis found that in the level of the Phylum,there are some changes in different periods but no statistical significance.In the genus level,there are some changes in different periods.Additionally,it was also found thatEnterococcus,Bacteroides,Alistipes,Faecalibacterium,Roseburia,Dorea and other 15 kinds of bacteria showed significant differencein different times of patients and among the donors.Furthermore,it is found that 16 kinds of common microorganisms such as Faecalibacterium,Blautia and Streptococcus in the donorsand patients,and that no common intestinal microbes were found betweenthe samples before pretreatmentand two weeks post transplantation.Four weeks post transplantation,a common Enterococcus species appeared in the samples,which is also the only common microorganism during the six weeks post transplantation.Thus,based on these findings,it was hypothesized that a relatively stable population of microorganisms might begin to form in intestineat four weeks post transplantation.We also analysed the correlation between intestinal microbial diversity and patient-related clinical data,and the results showed that the variation trend of intestinal microbial diversity is similar to that of lymphocyte/monocyte ratio(LMR).It showed that there may be a certain correlation between the diversity of intestinal microbes and immune cells.In summary,in the present study,high-throughput sequencing technology was used to study the intestinal microorganism in healthy donors and bone marrow transplant patients at different times.We discovered the change law of intestinal microflora in patients at different times,and it was presumed that there is a correlation between intestinal microbial diversity and immune cells,which will provide a certain experimental basis for reducing and preventing patients’ clinical infections after transplantation.