Individualization of Hematopoietic Stem Cell Transplantation Using Alpha/Beta T-Cell Depletion

Abstract

Allogeneic hematopoietic stem cell transplantation (HSCT) is associated with several potentially lethal complications. Higher levels of CD3+ T-cells in the graft have been associated with increased risk of graft-versus-host disease (GVHD), but also beneficial graft-versus-leukemia effect and reduced infections. To tackle post-transplant complications, donor lymphocyte infusions have been used but with an increased risk of GVHD. To reduce this risk, we performed depletion of αβ T-cells and treated 12 patients post-HSCT suffering from infections and/or poor immune reconstitution. The αβ T-cell depleted cell products were characterized by flow cytometry. The median log depletion of αβ T-cells was -4.3 and the median yield of γδ T-cells was 73.5%. The median CD34+ cell dose was 4.4 × 10⁶/kg. All 12 patients were alive 3 months after infusion and after 1 year, two patients had died. No infusion-related side effects were reported and no severe acute GVHD (grade III-IV) developed in any patient post-infusion. Overall, 3 months after infusion 11 out of 12 patients had increased levels of platelets and/or granulocytes. In conclusion, we describe the use of αβ T-cell depleted products as stem cell boosters with encouraging results.

Keywords: CliniMACS; allogeneic hematopoietic stem cell transplantation; donor lymphocyte infusion; graft manipulation; stem cell booster; αβ T-cell depletion; γδ T-cells.

Figure 1

Characteristics of αβ T-cell depleted grafts used as stem cell boosters (n = 12). (A) Log depletion of αβ T-cells and yield (recovery) of γδ T-cells in target fractions infused into patients (connected with dashed lines). (B) Analysis of cell subsets of interest in the αβ T-cell depleted cell products with (C) more detailed analysis of γδ subsets and invariant NKT-cells post-depletion gated on total T-cells. (D) Representative example plots of T-cells with αβ T-cell receptor (TCR), γδ TCR and γδ subsets are shown from patient 9 (all plots gated on total CD3+ T-cells).

Figure 2

Characterization of peripheral blood mononuclear cells 3–5 weeks (n = 9) after infusion of αβ T-cell depleted stem cell booster. (A) Major lymphocyte populations: T-cells (CD3+), B-cells (CD19+) and NK-cells (CD56+CD16+); (B) CD4 and CD8 T-cell subsets; (C) memory/maturation status of total (CD3+) T-cells; naïve (T_N, CCR7+CD45RO-), central memory (T_CM, CCR7+CD45RO+), effector memory (T_EM, CCR7-CD45RO+) and terminally differentiated (T_TD, CCR7-CD45RO-); (D) αβ T-cells, γδ T-cells and subsets of γδ T-cells and invariant NKT-cells (all gated on total T-cells); and (E) regulatory T-cells (CD25^highCD127^−/low on CD4+ T-cells) are presented along with (F) representative example plots from all indicated populations from patient 2. (G) Absolute numbers of T-, B- and NK-cells (with gray areas representing the normal range determined for healthy adult patients) and αβ+ and γδ+ cells, respectively (n = 8). Absolute numbers were calculated by multiplying the frequency of the subsets (gated from total alive cells) with the white blood count determined at 4 weeks post-infusion of αβ T-cell depleted cell product.

Figure 3

Clinical parameters (platelet, granulocyte and lymphocyte concentrations in peripheral blood) of patients (n = 12) before, at day of infusion and 12 weeks post-infusion of αβ T-cell depleted stem cell booster. (A) Relative fold change in concentration of platelets, (B) granulocytes, and (C) lymphocytes at 3, 6, 9, and 12 weeks post-infusion. For patients who did not have a reported count for these specific time points, counts from ±1 week were used. Concentration at the day of infusion was set to 1 (indicated by the line) to follow the relative development. Wilcoxon signed-rank test was used to determine paired statistical differences between each time point and the day of infusion. Significance levels were set to p < 0.05 (*), p < 0.01 (**), and p < 0.001 (***). (D) Individual development of the three cellular compartments in each patient (n = 12) where week 0 indicates time point of infusion are presented. Dashed line represents platelet concentration at time point of infusion. ^†indicates deceased patients at 12 months post-infusion (n = 2, patient 3 died at 4 months and patient 12 died at 8.5 months post-infusion).