Dental Biofilm Microbiota Dysbiosis Is Associated With the Risk of Acute Graft- Versus-Host Disease After Allogeneic Hematopoietic Stem Cell Transplantation

Abstract

Acute graft-versus-host disease (aGVHD) is one of the major causes of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Recently, aGVHD onset was linked to intestinal microbiota (IM) dysbiosis. However, other bacterial-rich gastrointestinal sites, such as the mouth, which hosts several distinctive microbiotas, may also impact the risk of GVHD. The dental biofilm microbiota (DBM) is highly diverse and, like the IM, interacts with host cells and modulates immune homeostasis. We characterized changes in the DBM of patients during allo-HSCT and evaluated whether the DBM could be associated with the risk of aGVHD. DBM dysbiosis during allo-HSCT was marked by a gradual loss of bacterial diversity and changes in DBM genera composition, with commensal genera reductions and potentially pathogenic bacteria overgrowths. High Streptococcus and high Corynebacterium relative abundance at preconditioning were associated with a higher risk of aGVHD (67% vs. 33%; HR = 2.89, P = 0.04 and 73% vs. 37%; HR = 2.74, P = 0.04, respectively), while high Veillonella relative abundance was associated with a lower risk of aGVHD (27% vs. 73%; HR = 0.24, P < 0.01). Enterococcus faecalis bloom during allo-HSCT was observed in 17% of allo-HSCT recipients and was associated with a higher risk of aGVHD (100% vs. 40%; HR = 4.07, P < 0.001) and severe aGVHD (60% vs. 12%; HR = 6.82, P = 0.01). To the best of our knowledge, this is the first study demonstrating that DBM dysbiosis is associated with the aGVHD risk after allo-HSCT.

Keywords: acute GVHD; allogeneic HSCT; bone marrow transplant; microbiome dysbiosis; oral microbiota; supragingival plaque.

Figure 1

Characterization of dental biofilm microbiota (DBM) during allogeneic hematopoietic stem cell transplantation. (A) DBM alpha diversity (Shannon) boxplots at preconditioning (n = 30), aplasia (n = 30) and engraftment (n = 27). Mann-Whitney U test was used with the preconditioning as the reference for comparisons. The boxes highlight the median value and cover the 25th and 75th percentiles, with whiskers extending to the more extreme value within 1.5 times the length of the box. (B) Average DBM genera relative abundance composition across transplantation phases. Only genera with at least 0.1% relative abundance in at least 25% study samples are shown. Taxa are sorted based on taxonomic relatedness. (C) Significant genera relative abundance variations from preconditioning to engraftment according to ANCOM test (W > 0.7). Log₂(Fold Change) for the average relative abundance variation (Engraftment/Preconditioning) is shown.

Figure 2

Dental biofilm microbiota alpha diversity is not associated with the risk of acute graft-versus-host disease (aGVHD). (A–C) Cumulative incidence of aGVHD with patients stratified by Shannon diversity index (High vs. Low) at preconditioning (A; n = 30), aplasia (B; n = 30) or engraftment (C; n = 27).

Figure 3

Specific genera relative abundance at preconditioning are associated with the risk of acute graft-versus-host disease (aGVHD). (A) Volcano plot for the univariate competing risk analysis for the association of aGVHD with genera relative abundance (hazard ratio vs. P-value) at preconditioning (left), aplasia (center) and engraftment (right). Only genera with ≥0.1% relative abundance in at least 25% of samples at a given phase were evaluated. Genera with P-value < 0.4 for the association are indicated explicitly. (B–D) Cumulative incidence of aGVHD with patients (n = 30) stratified by either Veillonella (B), Streptococcus (C) or Corynebacterium (D) relative abundance at preconditioning (High vs. Low). (E) Cumulative incidence of aGVHD with patients (n = 30) stratified by Veillonella/Streptococcus relative abundance ratio at preconditioning (>1 vs. ≤1).

Figure 4

Dental biofilm Enterococcus faecalis bloom during allogeneic hematopoietic stem cell transplantation is associated with a higher risk of acute graft-versus-host disease (aGVHD) and severe aGVHD (saGVHD). (A) Number of observed blooming events per genera in all patients (n = 30). The number of Enterococcus blooms caused exclusively by Enterococcus faecalis is indicated. (B) Relative abundance of Enterococcus faecalis across transplantation phases for all patients experiencing Enterococcus faecalis bloom (n = 5). Patients are sorted based on the highest Enterococcus faecalis relative abundance observed per patient. White horizontal dashed line indicates dominance threshold. P, Preconditioning; A, Aplasia; E, Engraftment. (C, D) Cumulative incidence of aGVHD (C) or saGVHD (D) with patients (n = 30) stratified by Enterococcus faecalis bloom occurrence (No vs. Yes).