Mini-review: How can we protect the microbiota in our gut from antimicrobial agents during hematopoietic stem cell transplantation?

Abstract

 In patients receiving hematopoietic stem cell transplantation (HSCT), antimicrobial prophylaxis is performed to prevent severe infection and improve prognosis. However, this prophylactic measure is associated with the disruption of the intestinal microflora and the onset and deterioration of graft-versus-host disease after HSCT. A trilogy of studies published in Science in 2018 showed that the immunological effect of treatment with anti-programmed death-1 (anti-PD-1) antibody in tumor-bearing mice varied with respect to the intestinal microbiota. Moreover, they demonstrated that the anti-tumor effect exerted by treatment with the anti-PD-1 antibody was enhanced as a result of the inoculation of intestinal bacterial flora. However, the bacteria which promoted the immunotherapeutic effect were not unique to this trilogy of studies. Further, these studies failed to identify universal bacteria that are responsible for the improvement of immunotherapy. Therefore, the fecal transplantation of intestinal bacterial flora, derived from a healthy donor, was investigated and established. However, one should note that an important aspect of fecal transplantation is the restoration of favorable functioning of gut microbiota.