Donor lymphocyte infusion to eradicate recurrent host hematopoiesis after allogeneic BMT for sickle cell disease

Mixed chimerism and graft loss in pediatric recipients of an alemtuzumab-based reduced-intensity conditioning regimen for non-malignant disease

BACKGROUND

Reduced-intensity conditioning (RIC) regimens can mitigate the toxicity of hematopoietic cell transplantation (HCT) in children with non-malignant diseases, but are associated with increased risk for post-transplant mixed donor/recipient chimerism (MC) and/or graft loss (GL). Intervention with donor lymphocytes or stem cell boosts (DLI/boost) may be necessary, but there is limited information about timing and results of intervention.

PROCEDURE

We retrospectively evaluated 31 consecutive pediatric recipients of an alemtuzumab-based RIC HCT at the Children's Hospital of Philadelphia from May 2007 to December 2012 to determine the incidence of MC, GL, and use of DLI/boost. All patients received alemtuzumab with either fludarabine (150 mg/m(2) )/melphalan (140 mg/m(2) ) (n = 30) or fludarabine/busulfan (n = 1), and unmanipulated marrow grafts from related (48%) or matched unrelated (52%) donors.

RESULTS

Of surviving patients, 67% and 44% displayed MC and MC with ≤80% donor contribution (MC ≤ 80%), respectively. Rates of MC, MC ≤ 80%, DLI/boost, and GL were significantly higher in recipients of proximal/intermediate (100%, 73%, 46%, and 46%, respectively) compared to distal alemtuzumab (44%, 25%, 6%, and 6%, respectively). Event-free and overall survival was significantly lower in HLH compared with non-HLH patients. Twenty percent of patients required DLI/boost, and DLI/boost did not affect the incidence of GL.

CONCLUSIONS

RIC with proximal/intermediate alemtuzumab is associated with high rates of MC, need for DLI/boost, and GL.

Escalating doses of donor lymphocytes for incipient graft rejection following SCT for thalassemia

Mixed chimerism (MC) and secondary graft failure are frequent events following SCT for thalassemia. There is limited information regarding the outcome of donor lymphocyte infusion (DLI) to prevent rejection, mainly from case reports describing only successful cases. We describe a series of seven children affected by beta-thalassemia treated with escalating doses of DLI for level 2-3 MC (donor<90%) following myeloablative SCT from a matched family donor. The infusions were safe and no acute or chronic GVHD were documented; five patients experienced neutropenia and thrombocytopenia resolving spontaneously. DLI was successful in converting to full donor chimerism two patients stratified in the low-risk class (Pesaro class II). Conversely, for five high-risk patients, DLI was not effective in preventing secondary graft failure. This limited series suggests that escalating doses of DLI are safe in thalassemia patients post myeloablative therapy but efficacy may be jeopardized by rapidly growing anti-donor alloimmunity in high-risk patients. We suggest giving escalating doses of donor T cells to attempt a graft-versus-thalassemia as soon as level 2-3 MC is detected.

How and when should we monitor chimerism after allogeneic stem cell transplantation?

SUMMARY

Chimerism analysis has become an important tool for the peri-transplant surveillance of engraftment. It offers the possibility to realize impending graft rejection and can serve as an indicator for the recurrence of the underlying malignant or nonmalignant disease. Most recently, these investigations have become the basis for treatment intervention, for example, to avoid graft rejection, to maintain engraftment and to treat imminent relapse by pre-emptive immunotherapy. This invited review focuses on the clinical implications of characterization of hematopoietic chimerism in stem cell transplantation.

Successful treatment of incipient graft rejection with donor leukocyte infusions, further proof of a graft versus host lymphohaemopoietic effect

Graft rejection is a major cause of treatment failure after T-cell-depleted stem cell transplantation (TCD-SCT) and remains a therapeutic challenge. Donor leukocyte infusions (DLIs) have an efficient graft versus host effect, which has been successfully used to treat recipient relapses. We hypothesized that this effect could be exploited to counteract the host versus graft reactions responsible for graft rejection. We report two adult patients with haematological malignancies who underwent sex-mismatched TCD-SCT from HLA-identical sibling donors. Peripheral blood (PB) counts and bone marrow (BM) cellularity were studied on a serial basis. Sequential chimaerism and minimal residual disease analysis were performed by FISH on PB and BM samples as well as on leukocyte lineages (T and B lymphocytes and myeloid cells) purified from PB using immunomagnetic technology. Both patients were diagnosed with incipient graft rejection 2-3 months after engraftment, based on persistently decreasing PB counts and BM cellularity together with the observation of decreasing mixed chimaerism (increasing percentage of recipient cells), mostly in whole PB and T lymphocytes. Both patients were successfully treated with a single DLI (1 x 10(7) CD3+ cells/kg), thereafter achieving normal PB counts and BM cellularity as well as complete chimaerism. Interestingly, the only side effect observed was mild graft versus host disease that did not require treatment. In conclusion, provided that an early diagnosis is made, the graft versus host lymphohaemopoietic effect harboured by immunocompetent donor cells can be successfully used for the treatment of incipient graft rejection.

Molecular assessment of erythroid lineage chimerism following nonmyeloablative allogeneic stem cell transplantation

OBJECTIVE

Nonmyeloablative conditioning regimens for allogeneic stem cell transplantation are now commonly used in the treatment of patients with hematologic malignancies. Since this treatment often results in the establishment of mixed hematopoietic chimerism, this approach may also prove to be useful in the treatment of nonmalignant disorders, such as sickle cell disease and thalassemia major. To apply this approach to these diseases, it will be necessary to determine the levels of donor erythropoiesis required to correct hemolysis and ameliorate disease symptoms. Current methods for measuring hematopoietic chimerism are based on DNA polymorphisms that distinguish recipient from donor. These methods accurately measure donor leukocyte engraftment but do not quantify the relative contributions of recipient and donor erythropoiesis following transplant.

METHODS

To specifically measure erythroid-lineage chimerism, we used pyrosequencing of the sickle cell mutation to quantify the relative levels of normal and sickle beta-globin mRNA in patient samples. Results of beta-globin RNA chimerism were compared to assessment of beta-globin DNA chimerism as well as analysis of short tandem repeat (STR) polymorphisms, cytogenetics, and hemoglobin electrophoresis.

RESULTS

Donor engraftment was measured in two adult patients following nonmyeloablative stem cell transplant for sickle cell disease. In Patient 1, 25 to 30% of peripheral leukocytes were donor derived after day 41. In contrast, more than 55% of peripheral blood beta-globin mRNA was of donor origin, and these results correlated with posttransplant clinical improvement. Patient 2 achieved 40 to 50% donor leukocyte engraftment from day 33 onward. This was associated with 70 to 100% peripheral blood donor beta-globin mRNA.

CONCLUSIONS

These studies demonstrate that relatively low levels of donor leukocyte engraftment can be associated with higher levels of donor erythropoiesis and with significant clinical improvement. Pyrosequencing of lineage-specific mRNA directly measures functional reconstitution of donor cells and provides valuable information that can affect clinical decisions in patients with nonmalignant diseases following allogeneic transplant.

Complete allogeneic hematopoietic chimerism achieved by a combined strategy of in utero hematopoietic stem cell transplantation and postnatal donor lymphocyte infusion

In utero hematopoietic stem cell transplantation (IUHSCTx) can achieve mixed hematopoietic chimerism and donor-specific tolerance without cytoreductive conditioning or immunosuppression. The primary limitation to the clinical application of IUHSCTx has been minimal donor cell engraftment, well below therapeutic levels for most target diseases. Donor lymphocyte infusion (DLI) has been used in postnatal circumstances of mixed chimerism as targeted immunotherapy to achieve a graft-versus-hematopoietic effect and to increase levels of donor cell engraftment. In this report we demonstrate in the murine model that a combined approach of IUHSCTx followed by postnatal DLI can convert low-level, mixed hematopoietic chimerism to complete donor chimerism across full major histocompatibility complex barriers with minimal risk for graft-versus-host disease (GVHD). Time-dated embryonic day 14 (E14) to E15 Balb/c (H-2K(d), CD45.2) fetuses underwent intraperitoneal injection of 5 x 10(6) T-cell-depleted B6 (H-2K(b), CD45.2) bone marrow cells. Chimeric recipients then received transplants at either 4 or 8 weeks of age with 1 of 3 doses (5, 15, or 30 x 10(6) cells) of donor congenic splenocytes (B6-Ly5.2/Cr, H-2K(b), CD45.1). The response to DLI was dose dependent, with conversion to complete donor peripheral blood chimerism in 100% of animals that received high-dose (30 x 10(6) cells) DLI. Only 1 of 56 animals receiving this dose succumbed to GVHD. This study directly supports the potential therapeutic strategy of prenatal tolerance induction to facilitate nontoxic postnatal cellular therapy and organ transplantation, and it has broad implications for the potential treatment of prenatally diagnosed genetic disorders.

Nonmyeloablative allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the most effective treatment for selected hematological malignancies. Its curative potential is largely mediated by an immune-mediated destruction of malignant cells by donor lymphocytes termed graft-versus-leukemia (GVL) effect. However, because of its toxicity, conventional allogeneic HSCT is restricted to younger and fitter patients. These observations led several groups to set up new (less toxic) transplant protocols (nonmyeloablative stem cell transplantation or NMSCT) based on a two-step approach: first, the use of immunosuppressive (but nonmyeloablative) preparative regimens providing sufficient immunosuppression to achieve engraftment of allogeneic hematopoietic stem cells and, in a second step, destruction of malignant cells by the GVL effect. Preliminary results showed that NMSCT were feasible with a relatively low transplant-related mortality (TRM), even in patients older than 65 years. In addition, strong antitumor responses were observed in several hematological malignancies as well as in some patients with renal cell carcinoma. After discussing the mechanisms and efficacy of the GVL effect as well as the rationale for NMSCT strategies, this article reviews the first results of ongoing clinical trials. Innovative modalities that may permit amplification of the GVL effect while minimizing the risk of GVHD are discussed. Because the benefits of NMSCT over alternative forms of treatment remain to be demonstrated, this strategy should be restricted to patients included in clinical trials.

Allogeneic transplantation for haemoglobinopathies

Beta-thalassaemia major and sickle-cell disease (SCD) reduce lifespan and quality of life for >300000 children and young adults worldwide. The only cure for both disorders is allogeneic stem cell transplantation (SCT). The decision-making processes in recommending SCT for patients with thalassaemia and SCD are different. For thalassaemia, where transfusion-related iron overload is universal, SCT should be offered to all patients <17 years because long-term survival and thalassaemia-free survival are about 80 and 70% respectively. For thalassaemics unable to comply with medical treatment, SCT offers a significant survival advantage; however, for patients with optimal medical care, short-term survival after SCT is inferior to medical treatment, and SCT instead offers a life free from transfusions and iron chelation. The clinical heterogeneity of SCD means that SCT is recommended only for selected patients with severe disease, particularly sickle-related neurological problems, for whom long-term survival and SCD-free survival after SCT approach 92 and 86% respectively. We here review the evidence available to help physicians evaluate the role of SCT for individual patients with thalassaemia major or SCD.

Ex vivo evaluation of PBMNCs collected with a new cell separator

BACKGROUND

This study reports on an evaluation of the ability of a cell separator (Amicus, Baxter Healthcare) and the integral MNC computer software program to collect a variety of MNC subsets. The collection efficiency (CE) of the Amicus for these MNC subsets was compared to that of another cell separator (CS-3000 Plus, Baxter). The collected MNCs were also assayed ex vivo to determine if these cells remained functional.

STUDY DESIGN AND METHODS

Healthy volunteer blood donors were recruited to provide PBMNCs for the isolation of CD3+, CD4+, CD8+, CD19+, NK, and gammadelta+ cells and monocytes. Cells were collected with an Amicus (test arm; n = 16) or a CS-3000 Plus (control arm; n = 11) cell separator. Cells were counted on a flow cytometer and CEs were calculated. For functional studies, the Amicus-collected MNC data were compared to CS-3000 Plus historical data. Functional studies performed included surface antigen expression assays (CD8+), proliferation assays (CD4+ and CD8+ cells), NK cytotoxicity assays for K562 and HUVE cells, and E-selectin induction on endothelial cells through NK+ contact dependency. Dendritic cells (DCs) were generated from CD34+ cells collected on the Amicus, positively selected by the use of antibody-bound, magnetic bead technology, and then cultured ex vivo with a combination of growth factors to generate the DCs.

RESULTS

CEs were higher on the Amicus than on the CS-3000 Plus for CD3+ (68 vs. 54%), CD4+ (70 vs. 56%), CD8+ (68 vs. 52%), and CD19+ (60 vs. 48%) cells (p<0.05). For the two separators, CEs were equivalent for monocytes, NK+, and gammadelta+ cells. The Amicus separator collected significantly fewer platelets than did the CS-3000 Plus (p<0.00001). CD4+, CD8+, and NK cells proliferated normally. NK cells appropriately stimulated E-selectin expression on endothelial cells. Culture-generated DCs obtained by using Amicus-collected CD34+ cells expressed appropriate cell surface markers.

CONCLUSION

The Amicus separator is acceptable for the collection of PBMNC subsets. The device collects CD3+, CD4+, CD8+, and CD19+ T- and B-cell subsets with greater efficiency and collects MNCs with significantly fewer contaminating platelets than does the CS-3000 Plus. Cells collected on the Amicus are suitable for use in a variety of research and clinical immunobiologic studies.