The number of donor CD3(+) cells is the most important factor for graft failure after allogeneic transplantation of CD34(+) selected cells from peripheral blood from HLA-identical siblings

The Impact of Graft CD3+ T-Cell Dose on the Outcome of T-Cell Replete Human Leukocyte Antigen-Mismatched Allogeneic Hematopoietic Peripheral Blood Stem Cells Transplantation

Background

Data on whether the graft CD3-positive (CD3⁺) T-cell dose in T-cell-replete human leukocyte antigen (HLA)-mismatched allogeneic hematopoietic peripheral blood stem cells transplantation (PBSCT) influences post-transplant outcomes are controversial.

Methods

Using King Hussein Cancer Center (KHCC) Blood and Marrow Transplantation (BMT) Registry database, 52 adult subjects, receiving the first T-cell-replete HLA-mismatched allogeneic hematopoietic PBSCT for acute leukemias or myelodysplastic syndrome, were identified, from January 2017 to December 2020. The cutoff value of graft CD3⁺ T-cell dose was identified using the receiver operating characteristic (ROC) formula and Youden's analysis. Subjects were divided into two cohorts: cohort 1 with low CD3⁺ T-cell dose (n = 34) and cohort 2 with high CD3⁺ T-cell dose (n = 18). Correlative analyses were performed between CD3⁺ T-cell dose and the risk of graft-versus-host disease (GvHD), relapse, relapse-free survival (RFS), and overall survival (OS). P-values were two-sided and considered significant when P < 0.05.

Results

Subject covariates were displayed. Subject's characteristics were comparable, except for higher nucleated cells and more female donors in the high CD3⁺ T-cell cohort. The 100-day cumulative incidence of acute GvHD (aGvHD) was 45±7% and 3-year cumulative incidence of chronic GvHD (cGvHD) was 28±6.7%. There was no statistically significant difference between the two cohorts in aGvHD (50% vs. 39%, P = 0.4) or cGvHD (29% vs. 22%, P = 0.7). The 2-year cumulative incidence of relapse (CIR) was 67.5±16.3% for low compared with 14.3±6.8% for high CD3⁺ T-cell cohort (P = 0.018). Fifteen subjects relapsed and 24 have died, 13 due to disease relapse. There was an improvement in 2-year RFS (94% vs. 83%; P = 0.0022) and 2-year OS (91% vs. 89%; P = 0.025) in low CD3⁺ T-cell cohort compared with high CD3⁺ T-cell cohort. Graft CD3⁺ T-cell dose is the only significant risk factor for relapse (P = 002), and OS (P = 0.030) in univariate analysis which was maintained in multivariate for relapse (P = 0.003), but not for OS (P = 0.050).

Conclusions

Our data suggest that high graft CD3⁺ T-cell dose is associated with lower risk of relapse, and might improve long-term survival, but has no influence on the risk of developing aGvHD or cGvHD.

Targeting Glycolysis in Alloreactive T Cells to Prevent Acute Graft-Versus-Host Disease While Preserving Graft-Versus-Leukemia Effect

Alloreactive donor T cells undergo extensive metabolic reprogramming to become activated and induce graft-versus-host disease (GVHD) upon alloantigen encounter. It is generally thought that glycolysis, which promotes T cell growth and clonal expansion, is employed in this process. However, conflicting data have been reported regarding the requirement of glycolysis to induce T cell-mediated GVHD due to the lack of T cell-specific treatments using glycolysis inhibitors. Importantly, previous studies have not evaluated whether graft-versus-leukemia (GVL) activity is preserved in donor T cells deficient for glycolysis. As a critical component affecting the clinical outcome, it is necessary to assess the anti-tumor activity following treatment with metabolic modulators in preclinical models. In the present study, we utilized T cells selectively deficient for glucose transporter 1 (Glut1^T-KO), to examine the role of glycolysis exclusively in alloreactive T cells without off-targeting effects from antigen presenting cells and other cell types that are dependent on glycolysis. We demonstrated that transfer of Glut1^T-KO T cells significantly improved acute GVHD outcomes through increased apoptotic rates, impaired expansion, and decreased proinflammatory cytokine production. In addition to impaired GVHD development, donor Glut1^T-KO T cells mediated sufficient GVL activity to protect recipients from tumor development. A clinically relevant approach using donor T cells treated with a small molecule inhibitor of glycolysis, 2-Deoxy-D-glucose ex vivo, further demonstrated protection from tumor development. These findings indicate that treatment with glycolysis inhibitors prior to transplantation selectively eliminates alloreactive T cells, but spares non-alloreactive T cells including those that protect against tumor growth. The present study has established a definitive role for glycolysis in acute GVHD and demonstrated that acute GVHD can be selectively prevented through targeting glycolysis.

Variable impact of graft CD3+ cell content on graft versus host disease in hematopoietic stem cell transplant recipients: Is the role of donor CD3+ cells overestimated?

Graft cellular composition is considered as a significant determinant of transplant outcome. Donor CD3⁺ cells were shown to have a significant association with the development of graft vs host disease (GvHD). The aim of this study was to investigate the impact of graft CD3⁺ cell content on transplant outcome, particularly in terms of GvHD and relapse. We retrospectively analysed the records of 515 allo-HCT recipients [median age: 37(15-71) years; male/female: 323/192]. The optimal threshold of infused CD3⁺ cell count for acute GvHD development was estimated to be 197.5 × 10⁶/kg (AUC: 0.572; 95 % CI: 0.513-0.631; p = 0.018) and 198.5 × 10⁶/kg (AUC: 0.6; 95 % CI: 0.520-0.679; p = 0.019) for the general population and reduced-intensity conditioning (RIC) subgroup, respectively. Acute GvHD was more frequent in low-CD3⁺ group in the whole study population, particularly in RIC transplants. The incidence of cytomegalovirus reactivation was higher in low-CD3⁺ group and neutrophil engraftment occured earlier in the same group of patients. Overall survival and non-relapse mortality were comparable between high and low-CD3⁺ groups. Age, ECOG performance status, hypogammaglobulinemia, chronic GvHD and post-transplant relapse were found to predict prognosis in multivariate analysis. By focusing mainly on donor T cells, the potential role of host immune cells in the early post-transplant milieu may have been underestimated. Drawing a more detailed profile of graft and host immune cells in the joint microenvironment may elucidate our way to a better understanding of GvHD pathogenesis. By this way a comprehensive pre-transplant risk assessment could be improved to generate more personalized approaches.

The effect of granulocyte colony-stimulating factor dose and administration interval after allogeneic hematopoietic cell transplantation on early engraftment of neutrophil and platelet

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is one of the treatments for hematologic malignancies. Numerous factors affect the HSCT outcome. The purpose of this study was to investigate the effect of post-HSCT administration of granulocyte colony-stimulating factor (post-G-CSF) on early neutrophil and platelet engraftment in allogeneic HSCT (allo-HSCT).

MATERIAL & METHODS

The study was performed on 76 patients diagnosed with AML and ALL. All patients underwent allo-HSCT at Taleghani stem cell transplantation center, Tehran, Iran, from February 2016 to December 2018. Chemotherapy regimens based on patients' conditions were selected between myeloablative and reduced-intensity regimens.

RESULTS

Statistical analysis revealed that the number of administered G-CSF units after HSCT was a time-dependent variable. Statistical analysis before day +11 reported that patients who received G-CSF <14 units had three times better early neutrophil engraftment than those with G-CSF ≥14 (CI 95%, AHR = 3.03, p:0.002). CD3+ cells count <318.5 × 10⁶ /kg was associated with fast platelet engraftment (CI 95%, AHR 2.28, p:0.01).

CONCLUSION

In this study, post-G-CSF stimulation was associated with early engraftment in a time- and dose-dependent manner. Administration of G-CSF beyond 14 units resulted in adverse effects on neutrophil early engraftment. It also appeared that with a reduction in CD3+ cell counts, the likelihood of GVHD decreases, and platelet engraftment occurs earlier. Further investigations in the future are required to determine the factors affecting the process of early engraftment.

"Ex-vivo" T-cell depletion in allogeneic hematopoietic stem cell transplantation: New clinical approaches for old challenges

Allogeneic transplantation still remains as standard of care for patients with high-risk hematological malignancies at diagnosis or after relapse. However, GvHD remains yet as the most relevant clinical complication in the early post-transplant period. TCD allogeneic transplant is now considered a valid option to reduce severe GvHD and to provide a platform for cellular therapy to prevent relapse disease or to treat opportunistic infections.

[Comparison of the clinical outcomes of haploidentical and matched-sibling donor stem cell transplantation for T cell acute lymphoblastic leukemia in complete remission]

目的

比较亲缘单倍型造血干细胞移植（HIDT）和同胞相合造血干细胞移植（MSDT）治疗完全缓解期（CR）急性T淋巴细胞白血病（T-ALL）的疗效。

方法

回顾性分析2012年5月至2017年5月间在河北燕达陆道培医院接受HIDT（81例）和MSDT（17例）的CR期T-ALL患者的临床特点和预后。

结果

HIDT组、MSDT组移植后100 d Ⅱ～Ⅳ度急性GVHD发生率分别为51.9％（95％CI42.0％～64.0％）、29.4％（95％CI 14.1％～61.4％）（P＝0.072），Ⅲ/Ⅳ度急性GVHD发生率分别为9.8％（95％CI 5.1％～19.1％）、11.8％（95％CI 3.2％～43.3％）（P＝1.000），巨细胞病毒（CMV）血症发生率分别为53.1％（95％CI 43.3％～65.2％）、29.4％（95％CI 14.1％～61.4％）（P＝0.115），EB病毒（EBV）血症发生率分别为35.8％（95％CI 26.8％～47.9％）、11.8％（95％CI 3.2％～43.3％）（P＝0.048）。HIDT、MSDT两组移植后5年总生存（OS）率分别为60.5％（95％CI 5.4％～49.0％）、68.8％（95％CI 11.8％～40.0％）（P＝0.315），无白血病生存（LFS）率分别为58.0％（95％CI 5.5％～46.5％）、68.8％（95％CI11.8％～40.0％）（P＝0.258），累积复发率分别为16.1％（95％ CI 9.8％～26.4％）、11.8％（95％ CI3.2％～43.3％）（P＝0.643），非复发死亡率（NRM）分别为25.9％（95％CI 17.9％～37.5％）、19.4％（95％CI6.9％～54.4％）（P＝0.386）。

结论

对于CR期T-ALL患者，当缺乏合适供者时，HIDT可作为替代选择。

The apheresis content analysis in Allo-HSCT represents reliable influential factors on graft-versus-host disease and overall survival

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is an established treatment for hematologic malignancies. However the post-HSCT outcome can be affected by multiple pre-transplant, transplant, and post-transplant factors. The cellular content of graft could be possible factors influencing the graft-versus-host disease (GVHD) and overall survival (OS) as transplantation outcomes.

PURPOSE

The aim of this study was to assess the impact of infused CD34+ cells, CD3+ cells, and MNC count on the patients' survival and incidence of graft-versus-host disease (GVHD).

MATERIAL AND METHODS

We analyzed 87 patients with hematological malignancies who underwent allogeneic hematopoietic stem cell transplantation at the Taleghani Stem Cell Transplantation and Cell therapy center, Tehran, Iran from January 2016 to December 2018. Patients were conditioned with either myeloablative conditioning regimen or reduced-intensity regimen.

RESULT

A CD34⁺ cell dose < 4.35 × 10⁶/kg and CD3⁺ cell dose < 365 × 10⁶/kg was associated with higher survival and lower acute and chronic GVHD incidence, although their association was not statistically significant. Moreover, there was a significant association between MNC count < 6.15 × 10⁸/kg and acute GVHD incidence.

CONCLUSION

Graft cell dose, lower than the cut-off level, could lead to better outcomes after allogeneic transplantation. However, this study showed that future investigations are required in a larger population of patients in order to determine the exact effect of allogeneic graft cell dose on transplantation outcome.

Peripheral blood stem cell grafts in allogeneic hematopoietic cell transplantation: It is not all about the CD34+ cell dose

Allogeneic Hematopoietic Cell Transplantation is a curative approach in various malignant and non-malignant disorders. The majority of adult transplants in the current era are performed using mobilized stem cells, harvested from the peripheral blood by leukapheresis. Peripheral blood stem cell (PBSC) collections are designed to target a dose of stem cells that will result in safe engraftment and hematopoietic recovery; however, 99 % of the cells contained in a PBSC graft are not stem cells and a growing number of studies attempt to characterize the associations between graft composition and transplant outcomes. A better understanding of the impact of the quantity and quality of various cell types in PBSC grafts may lead to development of novel collection strategies or improved donor selection algorithms. Here we review relevant findings from recent studies in this area.

CD34+ Stem Cell Selection and CD3+ T Cell Add-Back from Matched Unrelated Adult Donors in Children with Primary Immunodeficiencies and Hematological Diseases

Less than 25% of children who require hematopoietic stem cell transplantation (HSCT) for primary immunodeficiencies (PIDs) or genetic hematological diseases have an HLA-identical sibling. For them, a matched unrelated donor (MUD), although baring a greater risk of graft failure, delayed engraftment and immune reconstitution, and severe graft-versus-host disease (GvHD), represents a valid alternative. The stem cell source is also important, as unprocessed peripheral blood stem cells (PBSCs) contain 5 to 10 times more T cells than bone marrow (BM)-derived grafts, a major risk especially for small children with PID. A CD34+ positive selection can mitigate HLA compatibility issues, but the resulting CD3+ T cell depletion hampers engraftment and facilitates infections. To mitigate those problems, we decided to add back a certain number of T cells (30 × 10⁶ cells/kg body weight [BW]) to the positive CD34+ selection derived from MUD BM or PBSCs and report the results in terms of time to engraftment and immune reconstitution, GvHD incidence, infections, and survival. Our aim was to show not only the feasibility and clinical efficacy of this addback but also that PBSC-derived CD34+ selected grafts with calibrated T cell addback would be equivalent to BM-derived grafts. We analyzed retrospectively our single-center cohort of 76 children (median age, 1.9 years) affected by PID (61) and hematological diseases (15) who received a total of 79 MUD HSCTs with CD34+ selection and addback of 30 × 10⁶ CD3+ cells/kg BW between 2001 and 2019. We used descriptive and analytic statistics (chi-square, Student's t-test, Mann-Whitney U test, as appropriate) and constructed Kaplan-Meier curves using the log-rank test to compare patients grafted with BM or PBSC-derived inocula. The two groups showed no statistically significant differences in terms of age, sex, HLA-mismatch, or amount of CD3+ cells/kg BW added back to the CD34+ selection. However, the latter being higher in the PBSC group (P = .0001). Overall engraftment rate was 96% (73/76) and occurred faster in the PBSC group than in BM recipients: polymorphonuclear cells, 16 versus 21 days (P = .006); platelets, 15 versus 22 days (P = .001). GvHD incidence was low. No acute GvHD was diagnosed in 24 children, whereas grades I, II, III, and IV occurred in 19, 28, five, and three children, respectively (P not significant). Chronic GvHD was seen in only two children. The CD4+ count at six months after HSCT was higher in PBSC recipients as compared to those receiving BM (184 versus 88 CD4+ cells; P = .003). Overall survival for the whole cohort was 80% at 10 years, with no significant difference between the two stem cell sources (P not significant). Viral infections occurred among five of the PBSC grafted children and 14 in the BM group (P not significant), and no patient suffered from post-transplant lymphoproliferative disorder (PTLD). The results we present show that an addback of 30 × 10⁶ donor CD3+ cells/kg recipient BW to a MUD BM or PBSC-derived CD34+ selection gives promising results in infants and young children undergoing HSCT for PID or hematological diseases. Furthermore, with this manipulation the inherent limits of PBSC-derived grafts can be overcome, allowing both swift engraftment and immune reconstitution without an increase in GvHD, infections, or PTLD.

Immune Reconstitution After Allogeneic Haematopoietic Cell Transplantation: From Observational Studies to Targeted Interventions

Immune reconstitution (IR) after allogeneic haematopoietic cell transplantation (HCT) represents a central determinant of the clinical post-transplant course, since the majority of transplant-related outcome parameters such as graft-vs.-host disease (GvHD), infectious complications, and relapse are related to the velocity, quantity and quality of immune cell recovery. Younger age at transplant has been identified as the most important positive prognostic factor for favourable IR post-transplant and, indeed, accelerated immune cell recovery in children is most likely the pivotal contributing factor to lower incidences of GvHD and infectious complications in paediatric allogeneic HCT. Although our knowledge about the mechanisms of IR has significantly increased over the recent years, strategies to influence IR are just evolving. In this review, we will discuss different patterns of IR during various time points post-transplant and their impact on outcome. Besides IR patterns and cellular phenotypes, recovery of antigen-specific immune cells, for example virus-specific T cells, has recently gained increasing interest, as certain threshold levels of antigen-specific T cells seem to confer protection against severe viral disease courses. In contrast, the association between IR and a possible graft-vs. leukaemia effect is less well-understood. Finally, we will present current concepts of how to improve IR and how this could change transplant procedures in the near future.

Combined kidney and hematopoeitic cell transplantation to induce mixed chimerism and tolerance

Based on preclinical studies, combined kidney and hematopoietic cell transplantation was performed on fully HLA matched and haplotype matched patients at the Stanford University Medical Center. The object of the studies was to induce mixed chimerism, immune tolerance, and complete immunosuppressive drug withdrawal. Tolerance, persistent mixed chimerism, and complete withdrawal was achieved in the majority of fully matched patients. Persistent mixed chimerism and partial withdrawal has been achieved in the haplotype matched patients at present.

Harnessing the immune system after allogeneic stem cell transplant in acute myeloid leukemia

Allogeneic stem cell transplantation (allo-SCT) is the most successful and widely used immunotherapy for the treatment of acute myeloid leukemia (AML), as a result of its anti-leukemic properties driven by T cells and natural killer (NK) cells, leading to a graft-vs-leukemia (GVL) effect. Despite its essential role in AML treatment, relapse after allo-SCT is common and associated with a poor prognosis. There is longstanding interest in developing immunologic strategies to augment the GVL effect post-transplant to prevent relapse and improve outcomes. In addition to prophylactic maintenance strategies, the GVL effect can also be used in relapsed patients to reinduce remission. While immune checkpoint inhibitors and other novel immune-targeted agents have been successfully used in the post-transplant setting to augment the GVL effect and induce remission in small clinical trials of relapsed patients, exacerbations of graft-vs-host disease (GVHD) have limited their broader use. Here we review advances in three areas of immunotherapy that have been studied in post-transplant AML: donor lymphocyte infusion (DLI), immune checkpoint inhibitors, and other monoclonal antibodies (mAbs), including antibody-drug conjugates (ADCs) and ligand receptor antagonists. We also discuss additional therapies with proposed immunologic mechanisms, such as hypomethylating agents, histone deacetylase inhibitors, and the FLT3 inhibitor sorafenib.

High proportions of CD3+ T cells in grafts delayed lymphocyte recovery and reduced overall survival in haploidentical peripheral blood stem cell transplantation

T cells in grafts serve an important role in the pathogenesis of graft versus host disease (GVHD) and immune recovery during HLA matched allogeneic stem cell transplantation. However, the role of T cells in the haploidentical peripheral blood stem cell transplantation (Haplo-PBSCT) is yet to be determined. In the present study, the role of CD3⁺ T cells in grafts and impact on hematopoietic and immune recovery, cytomegalovirus (CMV) reactivation, GVHD, relapse, progress free survival and overall survival (OS) were evaluated and analyzed. A total of 30 patients who underwent haplo-PBSCT were included in the present study. CD3⁺ T cells accounted for a median of 23.1% (range 8-47.4%) with a median dose of 299.7x10⁶/kg (range 104-623.4). Patients were divided into two groups according to the CD3⁺ T cell count: Above the median (high T cell group) and below the median CD3⁺ T cell (low T cell group). No significant difference was identified between neutrophil and platelet recovery time between two groups (P>0.05). The mean lymphocyte recovery time of high T cell group and low T cell group were 107.07 days (95% CI 79.88-134.25), and 50.4 days (95% CI 41.42-59.38), respectively. The lymphocyte recovery time of high T cell group was higher that of low T cell group (P<0.05). No significant difference between CMV reactivation, chronic GVHD and primary disease relapse rates was observed between two groups (P>0.05). The cumulative incidence of grade II or above acute GVHD was higher in the high T groups compared with low T groups (P<0.05). The overall survival and progress free survival rates were higher in the low T cell group compared with the high T cell group (P<0.05). In conclusion, high levels of CD3⁺ T cells in the grafts were associated with delayed lymphocyte recovery and an increased risk of acute GVHD and decreased overall survival.

Olfactory ensheathing cells improve the survival of porcine neural xenografts in a Parkinsonian rat model

BACKGROUND

Parkinson's disease (PD) features the motor control deficits resulting from irreversible, progressive degeneration of dopaminergic (DA) neurons of the nigrostriatal pathway. Although intracerebral transplantation of human fetal ventral mesencephalon (hfVM) has been proven effective at reviving DA function in the PD patients, this treatment is clinically limited by availability of hfVM and the related ethical issues. Homologous tissues to hfVM, such as porcine fetal ventral mesencephalon (pfVM) thus present a strong clinical potential if immune response following xenotransplantation could be tamed. Olfactory ensheathing cells (OECs) are glial cells showing immunomodulatory properties. It is unclear but intriuging whether these properties can be applied to reducing immune response following neural xenotransplantation of PD.

METHODS

To determine whether OECs may benefit neural xenografts for PD, different compositions of grafting cells were transplanted into striatum of the PD model rats. We used apomorphine-induced rotational behavior to evaluate effectiveness of the neural grafts on reviving DA function. Immunohistochemistry was applied to investigate the effect of OECs on the survival of neuroxenografts and underlying mechanisms of this effect.

RESULTS

Four weeks following the xenotransplantation, we found that the PD rats receiving pfVM + OECs co-graft exhibited a better improvement in apomorphine-induced rotational behavior compared with those receiving only pfVM cells. This result can be explained by higher survival of DA neurons (tyrosine hydroxylase immunoreactivity) in grafted striatum of pfVM + OECs group. Furthermore, pfVM + OECs group has less immune response (CD3⁺ T cells and OX-6⁺ microglia) around the grafted area compared with pfVM only group. These results suggest that OECs may enhance the survival of the striatal xenografts via dampening the immune response at the grafted sites.

CONCLUSIONS

Using allogeneic OECs as a co-graft material for xenogeneic neural grafts could be a feasible therapeutic strategy to enhance results and applicability of the cell replacement therapy for PD.

Impact of T Cell Dose on Outcome of T Cell-Replete HLA-Matched Allogeneic Peripheral Blood Stem Cell Transplantation

Data on whether the T cell dose of allogeneic peripheral blood stem cell (PBSC) products influences transplantation outcomes are conflicting. Using the Center for International Blood and Marrow Transplant Research database, we identified 2736 adult patients who underwent first allogeneic PBSC transplantation for acute leukemia or myelodysplastic syndrome between 2008 and 2014 using an HLA-matched sibling donor (MSD) or an 8/8-matched unrelated donor (MUD). We excluded ex vivo and in vivo T cell-depleted transplantations. Correlative analysis was performed between CD3+ T cell dose and the risk of graft-versus-host-disease (GVHD), relapse, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Using maximum likelihood estimation, we identified CD3+ T cell dose cutoff that separated the risk of acute GVHD (aGVHD) grade II-IV in both the MSD and MUD groups. A CD3+ T cell dose cutoff of 14 × 107 cells/kg identified MSD/low CD3+ (n = 223) and MSD/high CD3+ (n = 1214), and a dose of 15 × 107 cells/kg identified MUD/low CD3+ (n = 197) and MUD/high CD3+ (n = 1102). On univariate analysis, the MSD/high CD3+ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MSD/low CD3+ group (33% versus 25%; P = .009). There were no differences between the 2 groups in engraftment rate, risk of aGVHD grade III-IV or chronic GVHD (cGVHD), NRM, relapse, DFS, or OS. The MUD/high CD3+ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MUD/low CD3+ group (49% versus 41%; P = .04). There were no differences between the 2 groups in engraftment rate, risk of severe aGVHD or cGVHD, NRM, relapse, DFS, or OS. Multivariate analysis of the MSD and MUD groups failed to show an association between CD3+ T cell dose and the risk of either aGVHD grade II-IV (P = .10 and .07, respectively) or cGVHD (P = .80 and .30, respectively). Subanalysis of CD4+ T cells, CD8+ T cells, and CD4+/CD8+ ratio failed to identify cutoff values predictive of transplantation outcomes; however, using the log-rank test, the sample size was suboptimal for identifying a difference at this cutoff cell dose. In this registry study, the CD3+ T cell dose of PBSC products did not influence the risk of aGVHD or cGVHD or other transplantation outcomes when using an MSD or an 8/8-matched MUD. Subset analyses of CD4+ and CD8+ T cell doses were not possible given our small sample size.

Concise Review: Boosting T-Cell Reconstitution Following Allogeneic Transplantation-Current Concepts and Future Perspectives

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for a large number of malignant and nonmalignant (inherited) diseases of the hematopoietic system. Nevertheless, non‐HLA identical transplantations are complicated by a severe T‐cell immunodeficiency associated with a high rate of infection, relapse and graft‐versus‐host disease. Initial recovery of T‐cell immunity following HSCT relies on peripheral expansion of memory T cells mostly driven by cytokines. The reconstitution of a diverse, self‐tolerant, and naive T‐cell repertoire, however, may take up to 2 years and crucially relies on the interaction of T‐cell progenitors with the host thymic epithelium, which may be altered by GvHD, age or transplant‐related toxicities. In this review, we summarize current concepts to stimulate reconstitution of a peripheral and polyclonal T‐cell compartment following allogeneic transplantation such as graft manipulation (i.e., T‐cell depletion), transfusion of ex vivo manipulated donor T cells or the exogenous administration of cytokines and growth factors to stimulate host‐thymopoiesis with emphasis on approaches which have led to clinical trials. Particular attention will be given to the development of cellular therapies such as the ex vivo generation of T‐cell precursors to fasten generation of a polyclonal and functional host‐derived T‐cell repertoire. Having been tested so far only in preclinical mouse models, clinical studies are now on the way to validate the efficacy of such T‐cell progenitors in enhancing immune reconstitution following HSCT in various clinical settings. stem cells translational medicine2019;00:1–8

Favorable immune recovery and low rate of GvHD in children transplanted with partially T cell-depleted PBSC grafts

Transplantation of peripheral blood stem cells (PBSC) from matched unrelated donors (MUD) is still associated with a significant risk for graft vs. host disease (GvHD), especially in pediatric patients receiving grafts from adult donors containing high amounts of T cells. Here, we present long-term follow-up results on 25 pediatric patients, (acute leukemia n = 15, NHL n = 3, CML n = 3, MDS n = 5), transplanted with CD34 or CD133 positively selected PBSC from MUDs supplemented with an add-back of 1 × 10⁷/kg body weight (kgBW) unselected T cells resulting in a median T-cell depletion (TCD) of 1.97 log. A total of 24/25 (96%) patients had primary engraftment. Early T-cell recovery was significantly improved compared to patients receiving CD34-selected grafts without T-cell add-back and similar to patients receiving unmanipulated bone marrow. GvHD incidence was low with 8/4% aGvHD grade II/III, no grade IV and 13% limited cGvHD. In total, 16/25 (64%) patients are alive after a median follow-up of 10 years. Five-year event-free survival (EFS) was 68%, relapse probability 24% and transplantation-related mortality (TRM) 12%. Thus, in PBSC allotransplants from MUD, partial TCD with serotherapy and CSA/MTX prophylaxis, can effectively reduce GvHD without hampering engraftment and immune reconstitution.

Allogeneic transplantation using CD34+ selected peripheral blood progenitor cells combined with non-mobilized donor T cells for refractory severe aplastic anaemia

Allogeneic haematopoietic stem cell transplantation is curative for severe aplastic anaemia (SAA) unresponsive to immunosuppressive therapy. To reduce chronic graft-versus-host disease (GVHD), which occurs more frequently after peripheral blood stem cell (PBSC) transplantation compared to bone-marrow transplantation (BMT), and to prevent graft rejection, we developed a novel partial T-cell depleted transplant that infuses high numbers of granulocyte colony-stimulating factor-mobilized CD34⁺ selected PBSCs combined with a BMT-equivalent dose of non-mobilized donor T-cells. Fifteen patients with refractory SAA received cyclophosphamide, anti-thymocyte globulin and fludarabine conditioning, and were transplanted with a median 8 × 10⁶ CD34⁺  cells/kg and 2 × 10⁷ non-mobilized CD3⁺ T-cells/kg from human leucocyte antigen-matched sibling donors. All achieved sustained engraftment with only two developing acute and two developing chronic GVHD. With a 3·5-year median follow-up, 86% of patients survived and were transfusion-independent. When compared to a retrospective cohort of 56 bone-marrow failure patients that received the identical transplant preparative regimen and GVHD prophylaxis with the exception that the allograft contained unmanipulated PBSCs, partial T-cell depleted transplant recipients had delayed donor T-cell chimerism and relative reduction of 75% in the incidence of acute grade II-IV GVHD (13% vs. 52%; P = 0·010) and of 82% in chronic GVHD (13% vs. 72%; P = 0·0004). In multivariate analysis, partial T-cell depleted transplants remained significantly associated with a reduced risk of GVHD. In conclusion, for patients with refractory SAA, this novel transplant strategy achieves excellent engraftment and survival when compared to unmanipulated PBSC transplants and dramatically reduces the incidence of both acute and chronic GVHD.

Specific removal of alloreactive T-cells to prevent GvHD in hemopoietic stem cell transplantation: rationale, strategies and perspectives

Hemopoietic stem cell transplantation (HSCT) is a standard procedure for treatment of malignant and non-malignant hematological diseases. HSCT donors include HLA-identical siblings, matched or mismatched unrelated donors and haploidentical related donors. Graft-versus-host disease (GvHD), mediated by donor alloreactive T-cells in the graft, can be triggered by minor histocompatibility antigens in HLA-identical pairs, by alleles at loci not considered for MUD-matching or by the mismatched haplotype in haplo-HSCT. Therefore, removal of donor T-cells, that contain the alloreactive precursors, is required, but T-cell depletion associates with opportunistic infections and with reduced graft-versus-leukemia effect. Selective T-cell depletion strategies have been introduced, like removal of αβ T-lymphocytes and of naive T-cells, two subsets including the alloreactive precursors, but the ultimate goal is specific removal of alloreactive T-cells. Here we review the different approaches to deplete alloreactive T-cells only and discuss pros and cons, specificity, efficiency and efficacy. Combinations of different methods and innovative approaches are also proposed for depleting specific alloreactive T-cells with high efficiency.

Chimerism, graft survival, and withdrawal of immunosuppressive drugs in HLA matched and mismatched patients after living donor kidney and hematopoietic cell transplantation

Thirty-eight HLA matched and mismatched patients given combined living donor kidney and enriched CD34(+) hematopoietic cell transplants were enrolled in tolerance protocols using posttransplant conditioning with total lymphoid irradiation and anti-thymocyte globulin. Persistent chimerism for at least 6 months was associated with successful complete withdrawal of immunosuppressive drugs in 16 of 22 matched patients without rejection episodes or kidney disease recurrence with up to 5 years follow up thereafter. One patient is in the midst of withdrawal and five are on maintenance drugs. Persistent mixed chimerism was achieved in some haplotype matched patients for at least 12 months by increasing the dose of T cells and CD34(+) cells infused as compared to matched recipients in a dose escalation study. Success of drug withdrawal in chimeric mismatched patients remains to be determined. None of the 38 patients had kidney graft loss or graft versus host disease with up to 14 years of observation. In conclusion, complete immunosuppressive drug withdrawal could be achieved thus far with the tolerance induction regimen in HLA matched patients with uniform long-term graft survival in all patients.

The cell composition of infused donor lymphocyte has different impact in different types of allogeneic hematopoietic stem cell transplantation

Donor lymphocyte infusion (DLI) is often used to enhance the graft-versus-leukemia (GVL) effect after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this study, we first evaluated the impact of the cell composition of a modified DLI (mDLI) on the prognoses of patients. A total of 194 patients undergoing allo-HSCT were enrolled and received mDLI for various clinical reasons. The infused cellular components of the mDLI were examined by flow cytometry. The results showed that infusion with a lower dose of CD14(+) cells (<0.33 × 10(8) /kg) was an independent risk factor for the occurrence of II-IV acute graft-versus-host disease (aGVHD) (HR = 0.104, p = 0.032) in human leukoctye antigen-identical transplant patients. In addition, a dose of CD14(+) cells greater than the 50th percentile was associated with a lower incidence of hematological relapse and longer disease-free survival (DFS) after the mDLI (relapse: HR = 0.193, p = 0.007; DFS: HR = 0.259, p = 0.016). However, we also found that a greater number of CD14(+) cells were an independent risk factor for II-IV aGVHD (HR = 1.758, p = 0.034) in haploidentical allo-HSCT. In conclusion, our data were the first to demonstrate that the cell composition of a 56 mDLI played a distinct role in different types of allo-HSCT. This finding provided a novel approach for the development of cellular therapies by manipulating the components of infused cells.

Effect of CD8⁺ cell content on umbilical cord blood transplantation in adults with hematological malignancies

Total nucleated (TNCs) and CD34(+) cells are considered major determinants of outcome after umbilical cord blood (UCB) transplantation but the effect of other cell subtypes present in the graft is unknown. This single-center cohort study included patients with hematological malignancies who received UCB transplantation after a myeloablative conditioning regimen. UCB units were primarily selected according to cell content, both TNCs and CD34(+) cells, and also according to the degree of HLA matching. Counts of several cell subtypes of the infused UCB unit, together with HLA disparities and other patient- and transplantation-related characteristics, were analyzed by multivariable methodology for their association with myeloid and platelet engraftment, graft-versus-host disease, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Two hundred patients (median age, 32 years) were included in the study. In multivariable analyses, a greater number of CD8(+) cells was significantly associated with better results for myeloid (P = .001) and platelet (P = .008) engraftment, NRM (P = .02), DFS (P = .007), and OS (P = .01). CD34(+) cell content was predictive of myeloid engraftment (P < .001). This study suggests that the outcome after UCB transplantation in adults with hematological malignancies could be better when UCB grafts had a greater CD8(+) cell content.

Long-term outcome of fludarabine-based reduced-intensity allogeneic hematopoietic cell transplantation for debilitating paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by intravascular hemolysis, venous thrombosis, and bone marrow failure. Seventeen patients with debilitating PNH, including 8 who were HLA-alloimmunized, underwent a reduced-intensity allogeneic hematopoietic cell transplantation (HCT). All received cyclophosphamide/fludarabine +/- antithymocyte globulin followed by a granulocyte colony-stimulating factor-mobilized HCT from an HLA-matched relative. Glycosylphosphatidylinositol-negative neutrophils were detectable after engraftment but disappeared completely at a median 100 days after transplantation. With a median follow-up of nearly 6 years, 15 patients (87.8%) survived, all without any evidence of PNH, transfusion independent, and off anticoagulation. Allogeneic reduced-intensity HCT remains a curative therapeutic option for PNH patients who are not candidates for eculizumab treatment.

Rapid donor T-cell engraftment increases the risk of chronic graft-versus-host disease following salvage allogeneic peripheral blood hematopoietic cell transplantation for bone marrow failure syndromes

The risk of graft-rejection after allogeneic hematopoietic cell transplantation using conventional cyclophosphamide-based conditioning is increased in patients with bone marrow failure syndromes (BMFS) who are heavily transfused and often HLA-alloimmunized. Fifty-six patients with BMFS underwent fludarabine-based reduced-intensity conditioning and allogeneic peripheral blood progenitor cell (PBPC) transplantation at a single institution. The conditioning regimen consisted of intravenous cyclophosphamide, fludarabine, and equine antithymocyte globulin. Graft-versus-host disease (GVHD) prophylaxis included cyclosporine A alone or in combination with either mycophenolate mofetil or methotrexate. To reduce the risk of graft-rejection/failure, unmanipulated G-CSF mobilized PBPCs obtained from an HLA-identical or single HLA-antigen mismatched relative were transplanted rather than donor bone marrow. Despite a high prevalence of pretransplant HLA-alloimmunization (41%) and a heavy prior transfusion burden, graft-failure did not occur with all patients having sustained donor lympho-hematopoietic engraftment. The cumulative incidence of grade II-IV acute-GVHD and chronic-GVHD was 51.8% and 72%, respectively; with 87.1% surviving at a median follow-up of 4.5 years. A multivariate analysis showed pretransplant alloimmunization and rapid donor T-cell engraftment (≥95% donor by day 30) were both significantly (P < 0.05) associated with the development of chronic-GVHD (adjusted HR 2.13 and 2.99, respectively). These data show fludarabine-based PBPC transplantation overcomes the risk of graft-failure in patients with BMFS, although rapid donor T-cell engraftment associated with this approach appears to increase the risk of chronic-GVHD. (Clinicaltrials.gov identifier: NCT00003838).

Predictive factors for rapid neutrophil and platelet engraftment after allogenic peripheral blood stem cell transplantation in patients with acute leukemia

The aim of this study was to investigate predictive factors for rapid engraftment after allogeneic peripheral blood stem cell transplantation (alloPBSCT) in patients with acute leukemia. Two hundred sixty-two patients receiving alloPBSCT were analyzed. Subset analyses of donor stem cells were conducted using a flow cytometric method. The correlation between rapid engraftment of neutrophils, platelets, and donor stem cells doses, as well as other recipient and donor clinical factors, was analyzed. In univariate analysis, factors correlated with neutrophil engraftment (≥0.5 × 10(9)/L) by day 12 were achievement of complete remission (CR) after induction chemotherapy (CR1) before hematopoietic cell transplantation (HCT) and high numbers of CD34+ cells, CD3+ T cells, and CD3+/CD4+ T cells. Factors correlated with platelet engraftment (≥20 × 10(9)/L) by day 12 were achievement of CR1 before HCT, donor and recipient sex mismatch, and high numbers of mononuclear cells, CD34+ cells, CD3+ T cells, CD3+/CD4+ T cells, CD3+/CD8+ T cells, and CD56+ NK cells. In multivariate analysis, independent predictive factors for rapid neutrophil and platelet engraftment were CR1 before HCT (p < 0.001 and p = 0.002, respectively), high number of donor CD34+ cells (p = 0.005 and p < 0.001, respectively), and high number of CD3+ T cells (p = 0.005 and p = 0.001, respectively). In conclusion, achieving CR1 before HCT, as well as larger quantities of donor CD34+ and CD3+ T cells, may predict rapid neutrophil and platelet engraftment after PBSCT.

The impact of graft composition on clinical outcomes in pediatric patients undergoing unmanipulated HLA-mismatched/haploidentical hematopoietic stem cell transplantation

OBJECTIVE

In pediatric patients, the association of graft composition with clinical outcomes after unmanipulated haploidentical hematopoietic stem cell transplantation has not been well defined. Therefore, the impact of graft composition on transplant outcomes was evaluated.

METHODS

We examined the absolute numbers and relative proportions of CD3+, CD4+, CD8+, CD14+, and CD34+ cells contained in allografts of 103 children who underwent unmanipulated HLA-mismatched/haploidentical hematopoietic stem cell transplantation (HSCT) without in vitro T cell depletion.

RESULTS

Multivariate analysis showed that a high CD34+ cell dose in G-CSF-primed bone marrow and peripheral blood grafts (G-PB) was related to accelerated platelet engraftment (P = 0.004). A higher CD3/CD14 ratio in G-PB (≥ 1.30) was associated with grade II-IV acute graft-versus-host disease (GVHD) (HR = 3.552; 95%CI 1.015-12.428, P = 0.047). In addition, only a heavier donor weight (HR = 5.837; 95%CI 1.841-18.513, P = 0.003) and a higher ratio of CD3/CD14 in the total graft (HR = 9.752; 95%CI 1.834-51.865, P = 0.008) were associated with worse overall survival. No aspect of graft composition affected neutrophil engraftment or disease relapse, though occurrence of chronic GVHD and a higher CD3/CD14 ratio in G-PB and total graft may reflect a lower incidence of relapse without statistical significance.

CONCLUSIONS

The dose of CD34+ cells and the CD3/CD14 ratio in allografts seem to have prognostic value for engraftment and clinical outcomes in pediatric patients undergoing unmanipulated haploidentical hematopoietic stem cell transplantation. A lower CD3/CD14 ratio in allografts demonstrated a survival benefit.

Gene-modified T lymphocytes in the setting of hematopoietic cell transplantation: potential benefits and possible risks

INTRODUCTION

Allogeneic hematopoietic cell transplantation (HCT) is a consolidated treatment for several hematologic malignancies. Donor T lymphocytes can mediate a graft versus tumor (GVT) effect and control opportunistic infections but can also cause severe graft versus host disease (GVHD). Gene-transfer strategies are appealing tools to modulate T cell functions when infused after HCT.

AREAS COVERED

The current and potential future applications of T cell gene-transfer approaches to HCT. This review is not limited to GVHD control but covers the issues of GVT and immune reconstitution. Clinical data are used to discuss more general issues, perspectives and concerns common to gene-modification of T cells. An overview of the results and limitations emerging from clinical trials with herpes simplex virus-thymidine kinase (HSV-TK) engineered lymphocytes is provided. The review provides perspectives on additional gene-transfer strategies, currently at preclinical level or that have just entered clinical trials, to increase the efficacy and safety of HCT.

EXPERT OPINION

Gene-transfer can positively interfere with T cell functions after HCT. TK-lymphocytes have proven effective in controlling GVHD while retaining an acceptable GVT effect. Strategies exploiting new suicide molecules or engineered T cell receptors (TCRs) should be further explored to address current limitations with TK-lymphocytes and augment the efficacy and specificity of GVT and antiviral activity.

The impact of CD34+ cell dose on platelet engraftment in pediatric patients following unmanipulated haploidentical blood and marrow transplantation

OBJECTIVE

Unmanipulated haploidentical blood and marrow transplantation has been developed as an alternative transplant strategy for pediatric patients with hematological diseases. The aim of this study was to investigate the effects of donor and recipient characteristics on hematopoietic recovery in pediatric patients following unmanipulated haploidentical transplantation.

METHODS

Factors correlating with hematopoietic recovery in 133 pediatric patients after unmanipulated haploidentical transplantation were analyzed retrospectively.

RESULTS

All patients reached an absolute neutrophil count of 500/microl in a median of 12 days (range, 9-49 days). One hundred thirty-three patients reached an untransfused platelet count of more than 20,000/microl in a median of 15 days (range, 7-180 days). Univariate analysis showed five factors associated with platelet engraftment. These were time to transplantation after diagnosis (P = 0.072), infused nuclear cells/kg of recipient weight (P = 0.028), CD3+ cells/kg of recipient weight (P = 0.082), CD4+ cells/kg of recipient weight (P = 0.083), and CD34+ cells/kg of recipient weight (P = 0.012). Multivariate analysis showed that infused CD34+ cells/kg of recipient weight (CD34+ cells more than 2.42 x 10(6)/kg vs. less than or equal to 2.42 x 10(6)/kg, HR = 1.733; 95% CI 1.222-2.549; P = 0.002) were significantly associated with an increased risk of platelet engraftment. Patients receiving a CD34+ cell dose more than 2.42 x 10(6)/kg had a short time [12 days (range, 7-176 days)] to achieve an untransfused platelet engraftment, compared to 18 days (range, 7-180 days) in patients receiving a lower dose (P < 0.001).

CONCLUSIONS

Our results suggest that low number of CD34+ cells in allografts is a critical factor associated with delayed platelet engraftment after unmanipulated haploidentical transplantation in pediatric patients.

Decision analysis of peripheral blood versus bone marrow hematopoietic stem cells for allogeneic hematopoietic cell transplantation. Biol Blood Marrow Transplant. 2009;15:1415-1421. [PMID: 19822301 DOI: 10.1016/j.bbmt.2009.07.009]

Peripheral blood stem cells (PBSCs) and bone marrow (BM) hematopoietic stem cells represent therapeutic alternatives in allogeneic hematopoietic cell transplantation. Randomized controlled trials and an individual patient data meta-analysis (IPDMA) have demonstrated a decreased risk of disease relapse and an increased risk of acute and chronic graft-versus-host disease (aGVHD, cGVHD) in patients receiving PBSCs compared with those receiving BM stem cells. Decision modeling provides quantitative integration of the risks and benefits associated with these alternative treatments, incorporates survival discounts for lower quality of life in patients with aGVHD or cGVHD and post-transplantation relapse, and allows sensitivity analyses for all model assumptions. We have constructed an externally validated Markov model to represent and analyze the decision to use PBSC or BM, estimating post-transplantation state transition probabilities (eg, GVHD and relapse) and quality-of-life discounts from the IPDMA and relevant literature; importantly, this IPDMA synthesized data from primarily adult patients treated with myeloablative (MA) conditioning regimens with T cell-replete matched sibling donors. In this setting, the model demonstrates the superiority of PBSC over BM in both overall and quality-adjusted life expectancy, with a 7-month advantage for PBSC. Sensitivity analyses support this conclusion through a range of values for each variable supported by the IPDMA and quality-of-life discounts, as supported by the literature. However, BM is the optimal strategy in conditions in which the 1-year relapse probability is < 5%. PBSC is the optimal stem cell source in terms of both overall and quality-adjusted life expectancy, except in conditions with a very low relapse probability, in which BM provides optimal outcomes.

CD34?+ cell dose and outcome of patients undergoing reduced-intensity-conditioning allogeneic peripheral blood stem cell transplantation

While in bone marrow allogeneic transplantation the infusion of high doses of progenitor stem cells has a favourable impact on outcome, due to a faster hematopoietic and immune recovery, in the peripheral blood allo-setting the infusion of a high number of CD34 cells increases the risk of extensive chronic graft vs. host disease (cGVHD). This higher incidence of extensive cGVHD has an adverse impact on outcome due to a higher transplant related mortality, specially among patients receiving T-cell depleted allogeneic transplantation with myeloablative conditioning. By contrast, patients undergoing reduced intensity conditioning regimen may benefit from increasing higher CD34 + cell doses, especially those categorized as high risk according to disease status at transplant. Thus, the source of progenitors cells, type of conditioning and GVHD prophylaxis, among other factors, may influence the effect of the progenitor cell dose on outcome after allogeneic transplant.

G-CSF-mobilized haploidentical peripheral blood stem cell transplantation in children with poor prognostic nonmalignant disorders

Haploidentical hematopoietic stem cell transplantation (HSCT) is currently one of the alternative curative treatment options for some nonmalignant but also for malignant diseases. However, concerns regarding its safety cause delays in time and a successful outcome. Between 2000 and 2005, twenty-one children with poor prognostic nonmalignant disorders, 13 boys and 8 girls, with a median age of 12 months, underwent 28 haploidentical peripheral HSCT. Immunomagnetic bead depletion device (CliniMACS) was used for indirect T-cell depletion. Indications for transplant were severe combined immunodeficiency (n=16), osteopetrosis (n=2), MDS (n=1), amegakaryocytic thrombocytopenia (n=1), and aplastic anemia (n=1). Five patients (24%) had lung infection at the time of transplantation. The patients received a median of 25.67 x 10(6) G-CSF-mobilized peripheral CD34(+) progenitor cells and a median of 4.19 x 10(4) T-lymphocytes per kilogram of body weight with a T-cell depletion rate of median 4.59 logs. The rate of total engraftment was 66.6%. Median times for leukocyte and platelet engraftment were 14 and 16 days, respectively. The 6-year projected survival was 32% for all patients and 29.76% for patients with severe combined immunodeficiency (SCID). The rates of transplant-related mortality, graft failure, and severe GvHD were 14.2, 33.4%, and 8.3%, respectively. Infection was the main cause of death. The poor outcome may be explained with the poor prognostic factors of our patients such as the type of SCID in most cases (T-B- SCID), the median age over 6 months and the presence of lung infection in some children at the time of transplantation.

Clinical stem-cell sources contain CD8+CD3+ T-cell receptor-negative cells that facilitate bone marrow repopulation with hematopoietic stem cells. Blood. 2008;111:1735-1738. [PMID: 17984314 DOI: 10.1182/blood-2007-02-076000]

Clinical observations in patients undergoing bone marrow transplantation implicate the involvement of CD8(+) cells in promoting the stem-cell engraftment process. These findings are supported by mouse transplant studies, which attributed the engraftment-facilitating function to subpopulations of murine CD8(+) cells, but the analogous cells in humans have not been identified. Here, we report that clinical stem-cell grafts contain a population of CD8alpha(+)CD3epsilon(+) T-cell receptor- negative cells with an engraftment facilitating function, named candidate facilitating cells (cFCs). Purified cFC augmented human hematopoiesis in NOD/SCID mice receiving suboptimal doses of human CD34(+) cells. In vitro, cFCs cocultured with CD34(+) cells increased hematopoietic colony formation, suggesting a direct effect on clonogenic precursors. These results provide evidence for the existence of rare human CD8(+)CD3(+)TCR(-) cells with engraftment facilitating properties, the adoptive transfer of which could improve the therapeutic outcome of stem-cell transplantation.

Comparative analysis of naïve and memory CD4+ and CD8+ T-cell subsets in bone marrow and G-CSF-mobilized peripheral blood stem cell allografts: impact of donor characteristics

OBJECTIVE

Donor T cells expressing lymph node homing receptors are the foremost initiators of acute graft-vs-host disease (aGVHD), and a high proportion of CD4(+)CCR7(+) T cells in human leukocyte antigen-matched allografts has been shown to confer a high risk of aGVHD without interfering in other outcomes.

METHODS

Naïve, central memory (T(CM)), effector memory (T(EM)), and terminally differentiated effector memory (T(TD)) subsets, further subdivided by CD28 expression, were compared in 52 bone marrow and 37 granulocyte colony-stimulating factor-mobilized peripheral blood harvests.

RESULTS

CCR7(+) cells (naïve and T(CM)) predominated in the CD4(+) population, whereas CD8(+) memory cells were chiefly CCR7(neg) in the grafts. Donor age, antecedent of chronic infections, and graft type were independent factors influencing graft composition. CD8(+) naïve cells negatively correlated and CD8(+) T(EM) positively correlated with age. Cytomegalovirus seropositivity was associated with more CD8(+) T(TD) and diminished CD28 expression. Toxoplasmosis seropositivity was associated with more CD4(+) T(CM) (p = 0.021). Marrow grafts comprised more CD28(+) cells within CD8(+) T(TD), but the percentage of CD4(+)CCR7(+) cells did not differ significantly between the two graft sources. Each of the four CD4(+) subsets and the percentage of CD4(+)CCR7(+) cells (p < 0.001) were correlated between graft and venous blood analyzed in 42 donors before harvest procedures.

CONCLUSION

This study provides reference values for CD4(+) and CD8(+) naïve and memory subsets within allografts applicable to the healthy donor population and indicates that beforehand analysis of a whole-blood sample can help evaluating the risk of aGVHD conferred by each donor and, when possible, choosing the one conferring the lowest risk.

Risk assessment in haematopoietic stem cell transplantation: Stem cell source

Bone marrow (BM) has been used for many years as the unique source of progenitor cells for allogeneic transplantation. However, two other sources of progenitor cells, peripheral blood (PB) and umbilical cord (UC), are being increasingly used. The type of graft is one of the most important factors in determining the speed and robustness of the reconstitution after the transplant of monocytes, T lymphocytes, B lymphocytes, NK cells, and dendritic cells. This fact is of especial relevance since the most important reactions after allogeneic transplants - e.g. graft-versus-host disease (GVHD), graft-versus-leukaemia effect (GvL), achievement of full donor chimerism, and fight against infections - are strongly influenced by a rapid and robust reconstitution of these cells. For this reason, the choice of the type of graft for allogeneic transplantation will influence the clinical outcome.

Non-CD34+ cells, especially CD8+ cytotoxic T cells and CD56+ natural killer cells, rather than CD34 cells, predict early engraftment and better transplantation outcomes in patients with hematologic malignancies after allogeneic peripheral stem cell transplantation

The effect of the transplant dose of each cell subset on engraftment kinetics and transplantation outcomes was evaluated in HLA-identical allogeneic peripheral blood stem cell transplantation (PBSCT). Sixty-nine patients were included in this retrospective study. Engraftment kinetics, transplantation outcomes, and immune reconstitution up to 1 year after transplantation were analyzed according to the transplant dose of CD34+ and non-CD34+ cells, including natural killer (NK) cells and CD8+ cytotoxic T (Tc) cells. An accelerated neutrophil engraftment was strongly associated with a higher transplant dose of NK cells (12 versus 16 days, P < .001) and Tc cells (13 versus 16 days, P < .001) but not CD34+ cells (P = .442). Survival analyses revealed a favorable prognosis for patients who received a higher dose of non-CD34+ cell subsets, rather than CD34+ cells, in terms of overall survival (OS; P = .024 for NK cells and .050 for Tc cells) and nonrelapse mortality (NRM; P = .005 for NK cells, .060 for Tc cells). In addition, a higher transplant dose of NK and Tc cells was correlated with a faster lymphoid reconstitution. In multivariate analyses, rapid neutrophil engraftment was correlated with a higher transplant dose of NK cells (P = .001) and Tc cells (P = .004). Moreover, an increased OS was associated with the NK cell dose (P = .007) and chronic graft-versus-host disease (P = .009), whereas a decreased NRM was associated with the NK dose (P = .024). In conclusion, in a PBSCT setting, a higher transplant dose of NK and Tc cells accelerated neutrophil engraftment, improved the immune reconstitution, and decreased NRM, thereby increasing OS after allogeneic PBSCT.

A high proportion of donor CD4+ T cells expressing the lymph node-homing chemokine receptor CCR7 increases incidence and severity of acute graft-versus-host disease in patients undergoing allogeneic stem cell transplantation for hematological malignancy

CC-chemokine receptor 7 (CCR7), a chemokine receptor required for transmigration into lymphoid organs, is only expressed by naive and central memory T cells. T cells with a capacity of homing into lymphoid organs can initiate acute graft-versus-host disease (GVHD) in mice and respond vigorously in vitro to alloantigens in humans, but their impact on clinical outcomes is unknown. We evaluated prospectively the distribution of naive, central memory and CCR7neg memory T-cell subsets in 39 bone marrow and 23 granulocyte colony-stimulating factor-mobilized peripheral blood stem cell allografts and investigated their impact on patient outcomes. Ranges of the relative proportions of CCR7+ cells within CD4+ and CD8+ T-cell populations were broad, but did not differ between the two sources of allografts. By multivariate analysis, high percentage of donor-derived CD4+CCR7+ T cells (>73.5%) significantly correlated with incidence, earliness of onset and severity of acute GVHD, conferring the highest adjusted hazard ratio (HR=3.9; 95% confidence interval 1.4-10.8; P=0.008) without interfering in other clinical events, especially chronic GVHD and relapse. Determination of the percentage of CD4+CCR7+ T cells in the graft provides a predictive indicator of acute GVHD. Partial depletion of this subset may reduce the risk of acute GVHD while preserving immunotherapeutic effects.