Dynamics of the Gut Microbiota in Children Receiving Selective or Total Gut Decontamination Treatment during Hematopoietic Stem Cell Transplantation

Bloodstream infections and graft-versus-host disease are common complications after hematopoietic stem cell transplantation (HSCT) procedures, associated with the gut microbiota that acts as a reservoir for opportunistic pathogens. Selective gut decontamination (SGD) and total gut decontamination (TGD) during HSCT have been associated with a decreased risk of developing these complications after transplantation. However, because studies have shown conflicting results, the use of these treatments remains subject of debate. In addition, their impact on the gut microbiota is not well studied. The aim of this study was to elucidate the dynamics of the microbiota during and after TGD and to compare these with the dynamics of SGD. In this prospective, observational, single center study fecal samples were longitudinally collected from 19 children eligible for allogenic HSCT (TGD, n=12; SGD, n=7), weekly during hospital admission and monthly after discharge. In addition, fecal samples were collected from 3 family stem cell donors. Fecal microbiota structure of patients and donors was determined by 16S rRNA gene amplicon sequencing. Microbiota richness and diversity markedly decreased during SGD and TGD and gradually increased after cessation of decontamination treatment. During SGD, gut microbiota composition was relatively stable and dominated by Bacteroides, whereas it showed high inter- and intraindividual variation and low Bacteroides abundance during TGD. In some children TGD allowed the genera Enterococcus and Streptococcus to thrive during treatment. A gut microbiota dominated by Bacteroides was associated with increased predicted activity of several metabolic processes. Comparing the microbiota of recipients and their donors indicated that receiving an SCT did not alter the patient's microbiota to become more similar to that of its donor. Overall, our findings indicate that SGD and TGD affect gut microbiota structure in a treatment-specific manner. Whether these treatments affect clinical outcomes via interference with the gut microbiota needs to be further elucidated. (C) 2019 American Society for Blood and Marrow Transplantation.Peer reviewe

Usage of TCRAV and TCRBV gene families in human fetal and adult TCR rearrangements

We have investigated fetal and adult T-cell receptor (TCR) A and B V-gene repertoires both by fluorescence-activated cell sorter (FACS) analysis with the avialable TCR V region-specific mAbs and by the polymerase chain reaction (PRC) with TRC V gene family-specific oligonucleotides. Among the low number of CD3+ T cells, most of the TRC V region tested for could be detected by FACS analysis in liver, bone marrow, and spleen derived from a 14-week-old fetus and two 15-weeks-old fetuses. Similarly, the PCR analysis showed that the majority of the TCRAV and TCRBV families were expressed in the peripheral organs of the 13-week-old fetus, although an apparent absence of particular TCR V families was found in liver and bone marrow. This was most probably the consequence of the low number of CD3+ T cells in these organs. In 17-week-old week-old fetal thymi the level of expression of some TCRAV and TCRBV gene families, in particular those that contain single member, was lower compared to post-partum thymi and adult peripheral blood mononuclear cells. The combined data of FACS and PCR analysis demonstrate that TCR genes belonging to the majority of TCR V gene families can be used in TCR α and β chain rearrngements during early human fetal life. Our data also suggest that the expression levels of some of the single member TCR V gene families may be influenced by the development stage

Complete Suppression of the Gut Microbiome Prevents Acute Graft-Versus-Host Disease following Allogeneic Bone Marrow Transplantation

<div><p>The hypothesis that elimination of facultative and strict anaerobic microorganisms from the gastro-intestinal tract by antimicrobial drugs in the period of time around allogeneic bone marrow transplantation (BMT) prevents acute graft-versus-host disease (GVHD), was examined in a cohort of 112 children grafted between 1989 and 2002 for hematological malignancies. All patients received T-cell replete marrow from human leukocyte antigens (HLA) matched sibling donors under identical transplantation conditions. To eliminate microorganisms from the gastro-intestinal tract, total gastro-intestinal decontamination (GID) was applied by high doses of non-absorbable antimicrobial drugs while the graft recipient was maintained in strict protective isolation. About half of the children (51%) proved to be successfully decontaminated, and about half (49%) unsuccessfully. One recipient got acute GVHD in the first group and 8 in the second group (p = 0.013). The degree of success of total GID was decisive for the occurrence of acute GVHD, irrespective of the presence of other risk factors such as higher age of recipient and/or donor, female donor for male recipient and carriership or reactivation of herpesviruses. Our results demonstrate that successful total GID of the graft recipient prevents moderate to severe acute GVHD. We suppose that substantial translocation of gastro-intestinal microorganisms or parts of these, functioning as microbial-associated molecular patterns (MAMP's), triggering macrophages/dendritic cells via pattern recognizing receptors (PRR's) is prohibited. As a consequence the initiation and progression of an inflammatory process leading to acute GVHD is inhibited.</p></div

HSV-, VZV-, CMV- and EBV- serological status of donor and recipient before BMT and relation to acute GVhD at day 50 post BMT.

a<p>DR: donor c.q. recipient of BMT</p>b<p>( ): number of ≥ grade II acute GVHD</p>c<p>p-value for D-R- versus other combinations; log-rank test.</p><p>HSV-, VZV-, CMV- and EBV- serological status of donor and recipient before BMT and relation to acute GVhD at day 50 post BMT.</p

Schematic representation of sequential events, cells and products concerned with acute GVHD following allogeneic BMT.

<p>DC, EC, MC,MØ, SC: dendritic cell, epithelial cell, microfold cell, macrophage, stem cell. IFN, IL, TGF, TNF: interferon, interleukin, T-cell growth factor, tumor necrosis factor. MAMPS, MHC, PRR: microbial-associated molecular patterns, major histocompatibility complex, pattern recognizing receptor.</p

Characteristics of the BMT recipients and donors.

<p>Abbreviations: ALL =  acute lymphoblastic leukemia; AML =  acute myeloid leukemia; CR =  complete remission; F =  female; JMML  =  juvenile myelo-monocytic leukemia; M =  male; NHL  =  non- Hodgkin lymphoma.</p>a<p>According to the treatment protocols of the Dutch Childhood Leukemia Study Group.</p><p>Characteristics of the BMT recipients and donors.</p

Severe bacterial and fungal infections after BMT and relation to acute GVHD.

a<p>in case only one blood culture was positive for coagulase negative Staphylococcus (which occurred 10 times) this was considered to be a contamination.</p>b<p>diagnosed by HR-CT scan.</p>c<p>(first) day of positive culture.</p>d<p>S/F of TGID: success or failure of total gastrointestinal decontamination.</p>e<p>grade and day of start of GVHD.</p><p>*, **, ***single patients with 2 infectious episodes.</p><p>Severe bacterial and fungal infections after BMT and relation to acute GVHD.</p