Citrulline and Monocyte-Derived Macrophage Reactivity before Conditioning Predict Acute Graft-versus-Host Disease

Future biomarkers for acute graft-versus-host disease: potential roles of nucleic acids, metabolites, and immune cell markers

INTRODUCTION

Acute graft versus host disease (aGVHD) is a potentially lethal complication after allogeneic stem cell transplantation. Biomarkers are used to estimate the risk of aGVHD and evaluate response to treatment. The most widely used biomarkers are systemic levels of various protein mediators involved in immunoregulation or reflecting tissue damage. However, systemic levels of other molecular markers such as nucleic acids or metabolites, levels of immunocompetent cells or endothelial cell markers may also be useful biomarkers in aGVHD.

AREAS COVERED

This review is based on selected articles from the PubMed database. We review and discuss the scientific basis for further studies to evaluate nucleic acids, metabolites, circulating immunocompetent cell subsets or endothelial markers as biomarkers in aGVHD.

EXPERT OPINION

A wide range of interacting and communicating cells are involved in the complex pathogenesis of aGVHD. Both nucleic acids and metabolites function as soluble mediators involved in communication between various subsets of immunocompetent cells and between immunocompetent cells and other neighboring cells. Clinical and experimental studies suggest that both neutrophils, monocytes, and endothelial cells are involved in the early stages of aGVHD pathogenesis. In our opinion, the possible clinical use of these molecular and cellular biomarkers warrants further investigation.

Single-cell RNA-sequencing reveals the transcriptional landscape of lacrimal gland in GVHD mouse model

PURPOSE

To investigate the global transcriptional landscape of lacrimal gland cell populations in the GVHD mouse model.

METHODS

Single-cell RNA sequencing and further bioinformatic analysis of dissociated lacrimal gland (LG) cells from the mouse model were performed. Parts of transcriptional results were confirmed by immunofluorescence staining.

RESULTS

We identified 23 cell populations belonging to 11 cell types. In GVHD LG, the proportion of acinar cells, myoepithelial cells, and endothelial cells was remarkably decreased, while T cells and macrophages were significantly expanded. Gene expression analysis indicated decreased secretion function, extracellular matrix (ECM) synthesis, and increased chemokines of myoepithelial cells. A newly described epithelial population named Lrg1high epithelial cells, expressing distinct gene signatures, was exclusively identified in GVHD LG. The fibroblasts exhibited an inflammation gene pattern. The gene pattern of endothelial cells suggested an increased ability to recruit immune cells and damaged cell-cell junctions. T cells were mainly comprised of Th2 cells and effective memory CD8+ T cells. GVHD macrophages exhibited a Th2 cell-linked pattern.

CONCLUSIONS

This single-cell atlas uncovered alterations of proportion and gene expression patterns of cell populations and constructed cell-cell communication networks of GVHD LG. These data may provide some new insight into understanding the development of ocular GVHD.

[Management of patients developing acute gastro-intestinal graft-versus-host-disease: Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

Graft-versus-host disease (GVHD) is the most common complication after allogeneic hematopoietic cell transplantation (allo-HCT) with a frequency range of 30% to 50%. GVH is the leading cause of non-relapse-related deaths and a cause early mortality. Gastro-intestinal (GI) GVH results in digestive manifestations that involve the small intestine and the colon. The patient may then have diarrhea, intestinal bleeding, abdominal pain but also clinical signs such as nausea and vomiting may lead to anorexia. GI-GVHD promotes undernutrition as well as significant losses of vitamins and trace elements. In the case of post-transplant diarrhea, differential diagnosis can include GI-GVHD, infection and drug toxicity. Although, corticosteroids w/wo calcineurin inhibitors represent the standard of care in first line treatment, there is no consensus regarding salvage therapy in case of corticoresistant GI-GVH. In addition, assessment of early nutritional status would help combating undernutrition, which is an independent risk factor for mortality in patients with GI-GVHD. In this workshop of the Fancophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC) we focused on the management of patients developing GI-GVHD following allo-HCT.

Impact and consequences of intensive chemotherapy on intestinal barrier and microbiota in acute myeloid leukemia: the role of mucosal strengthening

Induction chemotherapy (7 + 3 regimen) remains the gold standard for patients with acute myeloid leukemia (AML) but is responsible for gut damage leading to several complications such as bloodstream infection (BSI). We aimed to investigate the impact of induction chemotherapy on the intestinal barrier of patients with AML and in wild-type mice. Next, we assessed the potential benefit of strengthening the mucosal barrier in transgenic mice releasing a recombinant protein able to reinforce the mucus layer (Tg222). In patients, we observed a decrease of plasma citrulline, which is a marker of the functional enterocyte mass, of short-chain fatty acids and of fecal bacterial load, except for Escherichia coli and Enterococcus spp., which became dominant. Both the α and β-diversities of fecal microbiota decreased. In wild-type mice, citrulline levels decreased under chemotherapy along with an increase of E. coli and Enterococcus spp load associated with concomitant histologic impairment. By comparison with wild-type mice, Tg222 mice, 3 days after completing chemotherapy, had higher citrulline levels, a faster healing epithelium, and preserved α-diversity of their intestinal microbiota. This was associated with reduced bacterial translocations. Our results highlight the intestinal damage and the dysbiosis induced by the 7 + 3 regimen. As a proof of concept, our transgenic model suggests that strengthening the intestinal barrier is a promising approach to limit BSI and improve AML patients' outcome.

Macrophage regulation of graft-vs-host disease

Hematopoietic stem cell transplantation has become a curative choice of many hematopoietic malignancy, but graft-vs-host disease (GVHD) has limited the survival quality and overall survival of hematopoietic stem cell transplantation. Understanding of the immune cells’ reaction in pathophysiology of GVHD has improved, but a review on the role of macrophages in GVHD is still absent. Studies have observed that macrophage infiltration is associated with GVHD occurrence and development. In this review, we summarize and analyze the role of macrophages in GVHD based on pathophysiology of acute and chronic GVHD, focusing on the macrophage recruitment and infiltration, macrophage polarization, macrophage secretion, and especially interaction of macrophages with other immune cells. We could conclude that macrophage recruitment and infiltration contribute to both acute and chronic GVHD. Based on distinguishing pathology of acute and chronic GVHD, macrophages tend to show a higher M1/M2 ratio in acute GVHD and a lower M1/M2 ratio in chronic GVHD. However, the influence of dominant cytokines in GVHD is controversial and inconsistent with macrophage polarization. In addition, interaction of macrophages with alloreactive T cells plays an important role in acute GVHD. Meanwhile, the interaction among macrophages, B cells, fibroblasts, and CD4+ T cells participates in chronic GVHD development.

Brazilian Nutritional Consensus in Hematopoietic Stem Cell Transplantation: Graft- versus -host disease

The Brazilian Consensus on Nutrition in Hematopoietic Stem Cell Transplantation: Graft- versus -host disease was approved by Sociedade Brasileira de Transplante de Medula Óssea , with the participation of 26 Brazilian hematopoietic stem cell transplantation centers. It describes the main nutritional protocols in cases of Graft- versus -host disease, the main complication of hematopoietic stem cell transplantation.

A distinct glycerophospholipid metabolism signature of acute graft versus host disease with predictive value

BACKGROUND

Acute graft-versus-host disease (aGvHD) is a major factor that limits the successful outcomes of allogeneic hematopoietic cell transplantation (alloHSCT). Currently there are few validated biomarkers that can help predict the risk of aGvHD in clinical settings.

METHODS

We performed an integrated metabolomics and transcriptomics study and identified biomarkers that distinguish alloHSCT recipients with aGvHD from alloHSCT recipients without aGvHD in two separate cohorts.

RESULTS

Pathway analysis of 38 significantly altered metabolites and 1148 differentially expressed genes uncovered a distinctly altered glycerophospholipid (GPL) metabolism network. Subsequently, we developed an aGvHD risk score (GRS) based on 5 metabolites markers from GPL metabolism to predict the risk of aGvHD. GRS showed a positive predictive value of 92.2% and 89.6% in the training and validation cohorts, respectively. In addition, high GRS was correlated with poor overall survival. Gene expressions of GPL-related lipases were significantly altered in aGvHD samples, leading to dysregulated GPLs.

CONCLUSIONS

Using integrative "Omic" analysis, we unraveled a comprehensive view of the molecular perturbations underlying the pathogenesis of aGvHD. Our work represents an initial investigation of a unique metabolic and transcriptomic network that may help identify aGvHD at an early stage and facilitate preemptive therapy.

FUNDING

National Natural Science Foundation of China (NSFC; 81530047, 81870143, 81470321, 81770160, 81270567, 81270638, 81573396, 81703674). Shanghai Sailing Program from Science and Technology Commission Shanghai Municipality (17YF1424700). Scholarship from Shanghai Municipal Health and Family Planning Commission (2017BR012). Special Clinical Research in Health Industry in Shanghai (20184Y0054).

Innate Immune Determinants of Graft-Versus-Host Disease and Bidirectional Immune Tolerance in Allogeneic Transplantation

The success of tissue transplantation from a healthy donor to a diseased individual (allo-transplantation) is regulated by the immune systems of both donor and recipient. Developing a state of specific non-reactivity between donor and recipient, while maintaining the salutary effects of immune function in the recipient, is called “immune (transplantation) tolerance”. In the classic early post-transplant period, minimizing bidirectional donor ←→ recipient reactivity requires the administration of immunosuppressive drugs, which have deleterious side effects (severe immunodeficiency, opportunistic infections, and neoplasia, in addition to drug-specific reactions and organ toxicities). Inducing immune tolerance directly through donor and recipient immune cells, particularly via subsets of immune regulatory cells, has helped to significantly reduce side effects associated with multiple immunosuppressive drugs after allo-transplantation. The innate and adaptive arms of the immune system are both implicated in inducing immune tolerance. In the present article, we will review innate immune subset manipulations and their potential applications in hematopoietic stem cell transplantation (HSCT) to cure malignant and non-malignant hematological disorders by inducing long-lasting donor ←→ recipient (bidirectional) immune tolerance and reduced graft-versus-host disease (GVHD). These innate immunotherapeutic strategies to promote long-term immune allo-transplant tolerance include myeloid-derived suppressor cells (MDSCs), regulatory macrophages, tolerogenic dendritic cells (tDCs), Natural Killer (NK) cells, invariant Natural Killer T (iNKT) cells, gamma delta T (γδ-T) cells and mesenchymal stromal cells (MSCs).

Pretransplant Serum Citrulline Predicts Acute Graft-versus-Host Disease

Post-transplant biomarkers of acute graft-versus-host disease (aGVHD) and nonrelapse mortality (NRM) after allogeneic hematopoietic cell transplantation (allo-HCT) have been extensively studied. However, pretransplant biomarkers may provide a greater window of opportunity to intervene. We measured serum biomarkers of various aspects of gut barrier physiology before HCT (median, day -7) and 7 and 28 days post-HCT in 95 consecutive allo-HCT recipients enrolled in an open-label biorepository protocol. Biomarkers included citrulline for total functional enterocyte mass, Reg3a for antibacterial activity of the gut, and intestinal fatty acid binding protein (I-FABP) for enterocyte turnover. Compared to 16 healthy control subjects, we demonstrated that patients came to transplant with abnormal levels of all 3 biomarkers (P < .05), reflecting residual damage from prior chemotherapy. All 3 biomarkers initially declined from pre-HCT to day +7 (more pronounced after myeloablative than reduced-intensive conditioning) followed by a recovery phase and return toward pre-HCT values by day +28. A lower pre-HCT citrulline was independently associated with a higher risk of aGVHD grades II to IV (hazard ratio, 1.32; 95% confidence interval, 1.03 to 1.69; P = .02), and this association was not specific to gut GVHD. The strongest correlate of NRM was a higher level of Reg3a at day +7 (P < .001). I-FABP did not predict transplant outcomes. In conclusion, pre-HCT serum citrulline levels identify patients at high risk for developing aGVHD. Our results suggest that pre-HCT interventions to augment the gut barrier may decrease the risk of aGVHD.

Association Between Low Plasma Level of Citrulline Before Allogeneic Hematopoietic Cell Transplantation and Severe Gastrointestinal Graft vs Host Disease

BACKGROUND & AIMS

The gastrointestinal form of acute graft vs host disease increases morbidity and mortality following allogeneic hematopoietic cell transplantation. Plasma levels of citrulline, a non-proteinogenic amino acid, indicate functional enterocyte mass. We measured citrulline in patients before allogeneic hematopoietic cell transplantation and investigated its association with incidence and severity of gastrointestinal graft vs host disease.

METHODS

We performed a retrospective study with 191 patients (69 women, 122 men; median age of 52 years) who underwent allogeneic hematopoietic cell transplantation for hematological malignancies at a tertiary center of France from January 2013 through April 2015. Levels of citrulline in plasma samples collected 30 days before graft infusion were measured by high performance liquid chromatography with tandem mass spectrometry. We assigned patients to groups with a high level of citrulline (>26 μmol/L) or low level of citrulline (≤26 μmol/L). The primary outcomes were difference between groups in incidence of stage 2-4 gastrointestinal graft vs host disease, death without hematological disease relapse (non-relapse mortality), relapse of the hematological disease, and overall survival through 2 years after transplantation.

RESULTS

Ninety-six patients (50%) developed acute graft vs host disease and 37 (19%) developed a gastrointestinal form. Among patients with gastrointestinal involvement, 33 patients (89%) had stage 2-4 gastrointestinal graft vs host disease. In univariable analysis, low level of citrulline associated with higher cumulative incidence of stage 2-4 gastrointestinal graft vs host disease, non-relapse mortality, and shorter overall survival. In multivariable analysis, low level of citrulline was the only risk factor independently associated with stage 2-4 gastrointestinal graft vs host disease (hazard ratio, 3.06; 95% CI, 1.37-6.85; P = .007); it also associated with increased non-relapse mortality (hazard ratio, 2.29; 95% CI, 1.24-4.22; P = .008).

CONCLUSIONS

In a retrospective study with 191 patients, we associated a low plasma level of citrulline before allogeneic hematopoietic cell transplantation with a higher risk for stage 2-4 gastrointestinal graft vs host disease and non-relapse mortality. This marker might be used to manage patients before allogeneic hematopoietic cell transplantation.

Better early outcome with enteral rather than parenteral nutrition in children undergoing MAC allo-SCT

There is no consensus on the type of nutritional support to introduce in children undergoing allogeneic stem cell transplantation (allo-SCT) after myeloablative conditioning (MAC). This retrospective, multicenter, observational study compared the early administration of enteral nutrition (EN group, n = 97) versus parenteral nutrition (PN group, n = 97) in such patients with matching for important covariates. The primary endpoint was the study of day 100 overall mortality. The early outcome at day 100 was better in EN group regarding mortality rate (1% vs. 13%; p = 0.0127), non relapse mortality (1% vs. 7%; p = 0.066), acute GVHD grades II-IV (37% vs. 54%; p = 0.0127), III-IV (18% vs. 34%; p = 0.0333) and its gut localization (16% vs. 32%; p = 0.0136). Platelet engraftment was better in EN group than in PN group for the threshold of 20 G/L (97% vs. 80% p < 0.0001) and 50 G/L (92% vs. 78%, p < 0.0001). The length of stay was shorter in EN group (28 vs. 52 days, p < 0.0001). There were no differences between the two groups regarding the polynuclear neutrophil engraftment, infection rate or mucositis occurrence. These results suggest that, in children undergoing MAC allo-SCT, PN should be reserved to the only cases when up-front EN is insufficient or impossible to perform.