Acute GVHD after allogeneic hematopoietic transplantation affects early marrow reconstitution and speed of engraftment

Low content of clonogenic progenitors on day+18 is associated with acute graft-versus-host disease and predicts transplant-related mortality

A marrow reaction associated with acute-graft-versus-host disease (a-GVHD) has been demonstrated in experimental models; its existence in human transplantation is controversial. The aim of the present study was to investigate whether clonogenic marrow precursors are an early marker for a-GVHD and transplant-related mortality (TRM). We prospectively studied 133 patients for colony-forming units-granulocyte-monocyte (CFU-GM) at day +18/+19 posttransplantation. CFU-GM frequency below the 25th percentile was predictive of an acute GVHD score I°-IV° when evaluated in multivariate logistic regression analysis (odds ratio = 13.551, 95% confidence interval [CI]: 1.583-116.031, p = 0.01). In the group with a clonogenic frequency below the 25th percentile, the cumulative incidence of GVHD grades II-IV was significantly more frequent with respect to the group with a frequency greater than the 25th percentile, 86% versus 54% (Gray test: p = 0.02). In multivariate Cox proportional analysis, a CFU-GM frequency below the 25th percentile at day +18 was associated with reduced overall survival (OS) (hazard ratio = 1.778, 95% CI: 1.022-3.093, p = 0.04). Patients with a frequency of CFU-GM greater than the 25th percentile had increased TRM with respect to patients with a clonogenic cell frequency greater than the 25th percentile (33.5% vs. 13.0%, p = 0.01). Patients were divided based on median content of viable CD34+ cells, and measurement of viable CD34+ cells was predictive for OS (p = 0.005) and TRM (p = 0.003). A weak correlation was observed between CFU-GM frequency in marrow at day +18 and levels of IL-2 receptor (IL-2R) in plasma (r = -0.226, p = 0.03). We conclude that marrow progenitor cell counts, on day +18 may be a useful marker for identifying patients at risk for severe a-GVHD, TRM, and inferior survival.

Preliminary Results of a Combined Score Based on sIL2-Rα and TIM-3 Levels Assayed Early After Hematopoietic Transplantation

Assays of cytokines in the plasma at the onset of graft-vs. -host disease (GVHD) can predict disease severity and treatment-related mortality (TRM); however, the optimal time during which cytokines should be tested and the specific panel of cytokines with the highest predictive ability remain unknown. We chose a predefined time point, 18 days after hematopoietic stem cell transplantation (HSCT), to measure the levels of six cytokines in the plasma: soluble interleukin-2 receptor alpha (sIL2-Rα), T-cell immunoglobulin domain and mucin domain-3 (TIM-3), suppression of tumorigenicity-2 (ST-2), intercellular adhesion molecule (ICAM-1), interferon-gamma (IFN-γ), and interleukin-6 (IL-6). The study included 95 patients, who underwent allogeneic hematopoietic transplantation at our institution. Plasma levels of sIL2-Rα and TIM-3, measured as continuous data, had predictive value for overall survival (sIL2-Rα, p = 0.002; TIM-3, p = 0.0007), while TRM could be predicted by sIL2-Rα (p = 0.0005), IFN-gamma (p = 0.01), and IL-6 (p = 0.0001). No cytokine was associated with the risk of relapse. Patients were categorized into groups, according to cytokine thresholds determined by receiver operating characteristic curve analysis (sIL2-Rα ≤ or > 8,100 pg/ml; TIM-3 ≤ or > 950 pg/ml) and multivariate analysis was conducted. High levels of both TIM-3 and sIL2-Rα were significant predictors of poor survival [TIM-3 > 950 pg/ml: hazard ratio (HR) = 6.214 (95% CI 1.939–19.910), p = 0.002 and sIL2-Rα > 8.100 pg/ml: HR = 2.644 (95% CI 1.308–5.347), p = 0.006]. Using these cutoff thresholds, we constructed a composite scoring system that could distinguish three different groups of patients with varying rates of TRM: high risk, 41.7%; intermediate risk, 10.8%; and low risk, 7.1% (Gray's test: p = 0.001). If confirmed in a validation cohort, this composite scoring system could be used to guide the modulation of post-transplant immune suppressive therapy.

Loss of Lkb1 impairs Treg function and stability to aggravate graft-versus-host disease after bone marrow transplantation

Accumulating evidence suggests that a reduction in the number of Foxp3⁺ regulatory T cells (Tregs) contributes to the pathogenesis of acute graft-versus-host disease (aGVHD), which is a major adverse complication that can occur after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the precise features and mechanism underlying the defects in Tregs remain largely unknown. In this study, we demonstrated that Tregs were more dramatically decreased in bone marrow compared with those in peripheral blood from aGVHD patients and that bone marrow Treg defects were negatively associated with hematopoietic reconstitution. Tregs from aGVHD patients exhibited multiple defects, including the instability of Foxp3 expression, especially in response to IL-12, impaired suppressor function, decreased migratory capacity, and increased apoptosis. Transcriptional profiling revealed the downregulation of Lkb1, a previously identified critical regulator of murine Treg identity and metabolism, and murine Lkb1-regulated genes in Tregs from aGVHD patients. Foxp3 expression in human Tregs could be decreased and increased by the knockdown and overexpression of the Lkb1 gene, respectively. Furthermore, a loss-of-function assay in an aGVHD murine model confirmed that Lkb1 deficiency could impair Tregs and aggravate disease severity. These findings reveal that Lkb1 downregulation contributes to multiple defects in Tregs in human aGVHD and highlight the Lkb1-related pathways that could serve as therapeutic targets that may potentially be manipulated to mitigate aGVHD.

Marrow damage and hematopoietic recovery following allogeneic bone marrow transplantation for acute leukemias: Effect of radiation dose and conditioning regimen

BACKGROUND AND PURPOSE

Total body irradiation (TBI) is a common component of hematopoietic cell transplantation (HCT) conditioning regimens. Preclinical studies suggest prolonged bone marrow (BM) injury after TBI could contribute to impaired engraftment and poor hematopoietic function.

MATERIALS AND METHODS

We studied the longitudinal changes in the marrow environment in patients receiving allogeneic HCT with myeloablative (MA, n=42) and reduced intensity (RIC, n=56) doses of TBI from 2003-2013, including BM cellularity, histologic features of injury and repair, hematologic and immunologic recovery.

RESULTS

Following MA conditioning, a 30% decrease in the marrow cellularity persisted at 1 year post-transplant (p=0.03). RIC HCT marrow cellularity transiently decreased but returned to baseline by 6 months even though the RIC group received mostly umbilical cord blood (UCB) grafts (82%, vs. 17% in the MA cohort, p<0.01). There was no evidence of persistent marrow vascular damage or inflammation. Recipients of more intensive conditioning did not show more persistent cytopenias with the exception of a tendency for minimal thrombocytopenia. Immune recovery was similar between MA and RIC.

CONCLUSIONS

These findings suggest that TBI associated with MA conditioning leads to prolonged reductions in marrow cellularity, but does not show additional histological evidence of long-term injury, which is further supported by similar peripheral counts and immunologic recovery.