T cell depletion utilizing CD34(+) stem cell selection and CD3(+) addback from unrelated adult donors in paediatric allogeneic stem cell transplantation recipients

CD34‐selected haploidentical and unrelated donor allogeneic stem cell transplantation (AlloSCT) in paediatric recipients is associated with sustained engraftment and low risk of acute graft‐versus‐host disease (aGVHD), but limited by delayed immune reconstitution and increased risk of viral and fungal infection. The optimal dose of donor T cells to prevent graft failure and minimize risk of early opportunistic infection and post‐transplant lymphoproliferative disorder (PTLD), while avoiding severe aGVHD, remains unknown. We prospectively studied CD34‐selected 8–10/10 human leucocyte antigen (HLA)‐matched unrelated donor (MUD) peripheral blood stem cell transplantation (PBSCT) in a cohort of 19 paediatric AlloSCT recipients with malignant (n = 13) or non‐malignant (n = 6) diseases. T cells were added back to achieve total dose 1·0–2·5 × 10⁵ CD3⁺/kg. GVHD pharmacoprophylaxis consisted only of tacrolimus. All patients engrafted neutrophils. Probabilities of grade II–IV aGVHD, limited chronic GVHD (cGVHD), and extensive cGVHD were 15·8%, 23·3%, and 0%, respectively. One patient developed PTLD. One‐year infection‐related mortality was 5·6%. T cell immune reconstitution was delayed. One‐year overall survival was 82·3%. Five patients with malignant disease ultimately died from progressive disease. CD34‐selected MUD PBSCT using a defined dose of T cell add‐back resulted in high rates of engraftment and low risk of grade II–IV aGVHD, early transplantation‐related mortality, and extensive cGVHD.     

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 CD 34⁺ selected PBSC s 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 CD 34⁺ cells/kg and 2 × 10⁷ non‐mobilized CD 3⁺ 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 PBSC s, 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 .     

Activating killer immunoglobulin‐like receptor incompatibilities enhance graft‐versus‐host disease and affect survival after allogeneic hematopoietic stem cell transplantation

Objectives: Killer immunoglobulin‐like receptors (KIRs) regulate function of natural killer (NK) cells and a subset of T cells. In this study, we prospectively evaluated the impact of donor and recipient activating KIR genes on outcome of allogeneic hematopoietic stem cell transplantation (alloHSCT) for patients with hematological malignancies. Methods: One‐hundred consecutive recipients of myeloablative transplantation and their donors were tested for KIR genotype as well as for immune reconstitution, including activating KIR expression on NK cells and T cells. Results: In a multivariate analysis, mismatches of particular activating KIRs such that the patient was negative and the donor was positive (P^?D⁺) resulted in increased risk of acute (KIR2DS1) and chronic (KIR2DS3) graft‐versus‐host disease (GVHD) as well as relapse (KIR2DS5). KIR2DS1 incompatibility in the same direction in the presence of HLA‐C‐group 2 ligand in recipient was associated with reduced overall (risk ratio, RR = 3.01; P = 0.01) and disease‐free survival (RR = 2.92, P = 0.03). Activating mismatches in P^?D⁺ direction resulted in decreased CD4⁺ : CD8⁺ T‐cell ratio up to 1 yr after alloHSCT, as a consequence of decreased CD3⁺CD4⁺ number within the first 100 d and increased CD3⁺CD8⁺ number in later time‐points. Among six evaluated patients, expression of activating KIRs on NK cells and T cells was particularly prominent for those developing intestinal GVHD. Conclusion: Our findings indicate that the presence of particular activating KIRs in donor with their absence in recipient enhances GVHD, which is not accompanied by graft‐versus‐leukemia effect. Evaluation of activating KIR genotype may allow optimization of both donor selection and transplantation procedure in order to avoid GVHD.     

Combining CD34+ stem cell selection with prophylactic pathogen and leukemia directed T-cell immunotherapy to simultaneously reduce graft versus host disease,infection, and leukemia recurrence after allogeneic stem cell transplant

We designed a trial to simultaneously address the problems of graft versus host disease (GVHD), infection, and recurrence of malignancy after allogeneic stem cell transplantation. CD34⁺ stem cell isolation was used to minimize the development of acute and chronic GVHD. Two prophylactic infusions, one combining donor-derived cytomegalovirus, Epstein–Barr virus, and Aspergillus fumigatus specific T-cells and the other comprising donor-derived CD19 directed chimeric antigen receptor (CAR) bearing T-cells, were given 21–28 days after transplant. Two patients were transplanted for acute lymphoblastic leukemia from HLA identical siblings using standard doses of cyclophosphamide and total body irradiation without antilymphocyte globulin. Patients received no post-transplant immune suppression and were given no pre-CAR T-cell lymphodepletion. Neutrophil and platelet engraftment was prompt. Following adoptive T-cell infusions, there was rapid appearance of antigen-experienced CD8⁺ and to a lesser extent CD4⁺ T-cells. Tetramer-positive T-cells targeting CMV and EBV appeared rapidly after T-cell infusion and persisted for at least 1 year. CAR T-cell expansion occurred and persisted for up to 3 months. T-cell receptor tracking confirmed the presence of product-derived T-cell clones in blood targeting all three pathogens. Both patients are alive over 3 years post-transplant without evidence of GVHD or disease recurrence. Combining robust donor T-cell depletion with directed T-cell adoptive immunotherapy targeting infectious and malignant antigens permits independent modulation of GVHD, infection, and disease recurrence. The combination may separate GVHD from the graft versus tumor effect, accelerate immune reconstitution, and improve transplant tolerability.     

Quantitative lymphocyte subset reconstitution after allogeneic hematopoietic transplantation from matched related donors with CD34+ selected PBPC grafts unselected PBPC grafts or BM grafts.

CD34+ cell selection of PBPC after harvest from G-CSF-treated allogeneic donors results in a more than 200-fold depletion of T lymphocytes in the graft and has been used to reduce the incidence of acute GVHD post transplant. Since transplantation with T cell-depleted BM grafts is associated with a delay in immune reconstitution and an increase of opportunistic infections, we evaluated the immunological reconstitution of patients with hematologic malignancies after therapy followed by CD34+-selected PBPC34 transplantation from matched related donors. Lymphocyte subset reconstitution over the first 12 months post transplant and the incidence of infections were evaluated in 12 patients receiving PBPC34 grafts and compared to that of patients after transplantation with PBPC without CD34+ enrichment (n = 20) or unmanipulated bone marrow grafts (BM; n = 15). PBPC34 grafts contained 264-fold fewer T lymphocytes (median 0.53 x 10(6) kg/body weight) than PBPC grafts and 36-fold fewer than BM grafts (140 x 10(6)/kg and 19 x 10(6)/kg, respectively). Despite a two log depletion of T cells in the PBPC34 grafts, T lymphocyte reconstitution appeared comparable among the three transplant groups over the first 12 months. A positive patient CMV serostatus pretransplant was correlated with a faster T cell reconstitution in all transplant groups. GVHD prophylaxis with methylprednisolone delayed B lymphocyte reconstitution. The incidence of infections post transplant did not appear to be increased in the PBPC34 group compared with the PBPC and BMT groups. It remains to be shown in larger prospective trials, whether these promising preliminary data of lymphocyte reconstitution and the clinical course after transplantation with PBPC34 can be confirmed.     

Immune reconstitution and cytomegalovirus infection after allogeneic stem cell transplantation: the important impact of in vivo T cell depletion

We analyzed cytomegalovirus (CMV) infection risk factors and immune reconstitution kinetics in 89 patients after allogeneic stem cell transplantation (allo-SCT). The use of alemtuzumab for in vivo T cell depletion (TCD) had, besides the donor/recipient CMV serostatus, the strongest influence on the CMV infection risk in univariate and multivariate analyses. In comparison to without use of in vivo TCD, the CMV infection risk [hazard ratio (HR)] was 4.82-fold after TCD with alemtuzumab, but only 1.40-fold after TCD with antithymocyte globulin (ATG). Alemtuzumab strongly depressed CD4⁺ and CD8⁺ T cell reconstitution, whereas ATG only delayed CD4⁺ T cell reconstitution. Considering the reconstitution kinetics of CD4⁺ and CD8⁺ T cells, CMV-specific CD8⁺ T cells, NK cells and the IgG concentration, only a low day +60 NK cell count (≤161 versus >161/μl) was significantly associated with CMV infection development (HR 2.92, p = 0.034). CMV-specific CD8⁺ T cells were detected in 57% of patients with a CMV-seropositive donor, but in none of the patients with a CMV-seronegative donor on day +30 (p = 0.01). Our data indicate that the type of in vivo TCD (alemtuzumab or ATG) differentially influences both the CMV infection risk and CD4⁺/CD8⁺ T cell reconstitution kinetics in patients after allo-SCT.     

Different immune reconstitution in multiple myeloma, chronic myeloid leukemia and acute myeloid leukemia patients after allogeneic transplantation of peripheral blood stem cells

In this study we compared the lymphocyte reconstitution in 13 multiple myeloma (MM), nine acute myeloid leukemia (AML) and 10 chronic myeloid leukemia (CML) patients after allogeneic G-CSF-mobilized PBSC transplantation from HLA-identical siblings. Conditioning regimens included standard total body irradiation + cyclophosphamide (CY), or busulphan + CY, whereas VP-16 was added in patients with advanced disease. Overall comparable numbers of mononuclear cells, CD34+ cells and CD3+ T cells were infused in each group. A significantly higher CD3+ T cell number was observed in MM and AML than in CML patients 1 month after transplant. However, MM patients showed a faster and better recovery of CD4+ T cells than both AML and CML patients at 3 months (P = 0.01 and P = 0.01, respectively) and 12 months (P = 0.01 vs AML, while P = NS vs CML) after transplant, and had a CD4:CD8 ratio > 1 with a median CD4+ T cell value > 400/microl 1 year after transplant. Development of acute graft-versus-host disease (GVHD) did not affect CD4:CD8 ratios but patients who experienced acute GVHD > grade I had lower CD4+ and CD8+ T cell numbers at all time points. However, after excluding patients with GVHD > grade I, MM patients still showed a significantly higher CD4+ T cell value than patients with myeloproliferative diseases 1 year after transplant. These findings suggest that although allogeneic PBSC transplantation induces rapid immune reconstitution, different kinetics may occur among patients with hematological malignancies. In particular, the rapid reconstitution of CD4+ T cells in MM patients may contribute to the low transplant-related mortality achieved in this disease.     

Immune reconstitution assessed during five years after allogeneic bone marrow transplantation

Immune reconstitution is an important component of successful allogeneic bone marrow transplantation. Immune reconstitution was evaluated for 5 years after transplantation. While the number of CD8+ T cells and CD56+ cells recovered early post transplantation, a low number of CD4+ and CD4+ CD45RA+ T cells and reversal of the CD4/CD8 ratio continued up to 5 years. Although early recovery of IgG and IgM was seen at day 100 post transplantation, serum concentration of IgA was below the normal range at 6 months and increased gradually up to 5 years. Development of acute GVHD did not affect the numbers of CD4+, CD8+, CD4+ CD45RA+ and CD4+ CD29+ T cells, but the number of CD56+ cells in patients who developed grades II-IV acute GVHD was low. The number of CD4+ CD29+ T cells had a tendency to be higher in the patients with extensive chronic GVHD than in those without chronic GVHD 2 years after transplantation whereas the number of CD4+ CD45RA+ T cells was low in spite of the absence of chronic GVHD. Serum concentration of IgA was lower in patients with extensive chronic GVHD than in those without chronic GVHD at 180 days. The number of CD4+ CD45RA+ cells in 10-19-year-old patients was higher than that in 40-49-year-old patients. Response to the Con A and PHA in 10-19-year-old patients was higher than that in older patients at 1 and 2 years. There was no significant difference in the ability of immune reconstitution between related transplant recipients and unrelated transplant recipients. These results suggest that chronic GVHD and age of patients affected immune reconstitution post transplant.     

T memory stem cells after allogeneic haematopoietic cell transplantation: unique long-term kinetics and influence of chronic graft-versus-host disease

T memory stem cells (TSCMs) are a subset of primitive T cells capable of both self-renewal and differentiation into all subsets of memory and effector T cells. Therefore, TSCMs may play a role in immune reconstitution and graft-versus-host disease (GVHD) in patients receiving allogeneic haematopoietic cell transplantation (HCT). We conducted a cross-sectional study to evaluate the proportions, absolute counts, phenotypes and functions of TSCMs in 152 adult patients without disease recurrence at least 12 months after undergoing HCT. CD4⁺ TSCMs were negatively correlated with number of months after transplantation in HCT patients that received cord blood transplantation, but not in patients that received bone marrow transplantation or peripheral blood stem cell transplantation. The proportions and absolute counts of CD4⁺ TSCMs and expression levels of inducible co-stimulator (ICOS) in CD8⁺ TSCMs were significantly higher in patients with mild and moderate/severe cGVHD compared to patients without cGVHD. These data suggested that, more than 12 months after allogeneic HCT, the kinetics of CD4⁺ TSCMs were dependent on the type of donor source, and further that CD4⁺ TSCMs and ICOS levels in CD8⁺ TSCMs were associated with cGVHD.     

High donor FOXP3-positive regulatory T-cell (Treg) content is associated with a low risk of GVHD following HLA-matched allogeneic SCT

Regulatory T cells (T(reg)s) that constitutively express FOXP3 are instrumental to the maintenance of tolerance and may suppress graft-versus-host disease (GVHD) in humans. To determine whether regulatory T cells in allogeneic stem cell transplants (SCTs) ameliorate GVHD after transplantation, we quantitated the coexpression of FOXP3 on CD4(+) T cells in 32 donor SCTs infused into HLA-matched siblings and examined GVHD incidence in respective recipients. High CD4(+)FOXP3(+) T-cell count in the donor was associated with a reduced risk of GVHD. We monitored T(reg)s during immune reconstitution in 21 patients with leukemia undergoing a T-cell-depleted allogeneic SCT. Early after SCT, there was a significant expansion in the CD4(+)FOXP3(+) T-cell compartment. A low CD4(+)FOXP3(+) T-cell count early after SCT (day 30) was associated with an increased risk of GVHD, and the ratio of CD4(+)FOXP3(+) T cells to CD4(+)CD25(+)FOXP3(-) T cells was significantly reduced in patients with GVHD, suggesting diminished control of effector T cells. Our findings suggest that graft T(reg) content may predict for risk of GVHD after SCT. Determining the T(reg) levels in the donor and manipulating T(reg)s early after transplantation may provide a new approach to controlling GVHD.     

T lymphocytes of recipient origin may contribute to the recovery of specific immune response toward viruses and fungi in children undergoing cord blood transplantation

Patients undergoing allogeneic cord blood transplantation (CBT) benefit from a low risk of graft-versus-host disease (GVHD), but there are still concerns that they be able to recover an effective immune capacity early after transplantation. We investigated the ability to develop in vitro T-lymphocyte-mediated immune response toward human cytomegalovirus and Candida albicans antigens, early and late after transplantation, in children given cord blood transplants from either an HLA-identical sibling or an unrelated donor. Proliferative capacity and frequency of antigen-specific T cells were evaluated; antigen-specific CD4(+) T-cell clones were also generated and characterized for T-cell receptor repertoire diversity, cytokine phenotype, and their origin (either from donor or patient). We found that the majority of recipients can develop a specific response to viral or fungal antigens already early after transplantation. Antigen-specific T-cell clones of both donor and recipient origin contributed to the reconstitution of immune response. Antigen-specific T lymphocytes of recipient origin were detected in patients receiving a transplant from a relative, after a chemotherapy-based conditioning regimen, and who did not have GVHD. Our results document, at a clonal level, that after CBT recovery of either polyclonal or pauciclonal T-cell response toward widespread pathogens is prompt, with some patients benefiting from a contribution of recipient-derived cells.     

Donor lymphocyte infusion and methotrexate for immune recovery after T‐cell depleted haploidentical transplantation

CD34+ cell selection minimizes graft‐versus‐host disease (GVHD) after haploidentical donor stem cell transplant but is associated with slow immune recovery and infections. We report a Phase I/II study of prophylactic donor lymphocyte infusion (DLI) followed by methotrexate (MTX) GVHD prophylaxis after CD34‐selected haploidentical donor transplant. A prophylactic DLI was given between day +30 and +42. Rituximab was given with DLI for the last 10 patients. The goal of the study was to determine a DLI dose that would result in a CD4+ cell count > 100/µL at Day +120 in ≥ 66% of patients with ≤ 33% grade II‐III, ≤ 17% grade III, and no grade IV acute GVHD by Day +180. Thirty‐five patients with malignant (n = 25) or nonmalignant disease (n = 10) were treated after CD34‐selected haploidentical donor peripheral blood stem cell transplant. The DLI dose of 5 × 10⁴/kg met the CD4/GVHD goal with 67% of patients having CD4+ cells > 100/µL and 11% grade II‐IV acute GVHD. The cumulative incidence of chronic GVHD was 16%. Fatal viral and fungal infections occurred in 11%. The 2 year estimated overall survival was 69% and the relapse rate was 14% for patients in remission at transplant. There was no effect of NK alloreactivity on relapse. Nine of ten patients at the target DLI dose cohort of 5 × 10⁴/kg are alive with median follow‐up of 18 mos (range 6‐29). Delayed prophylactic DLI and MTX was associated with promising outcomes at the target DLI dose. This trial was registered at clinicaltrials.gov , # NCT01027702.     

Epstein–Barr virus‐associated pneumonia in patients with post‐transplant lymphoproliferative disease after hematopoietic stem cell transplantation

Q.‐F. Liu, Z.‐P. Fan, X.‐D. Luo, J. Sun, Y. Zhang, Y.‐Q. Ding. Epstein–Barr virus‐associated pneumonia in patients with post‐transplant lymphoproliferative disease after hematopoietic stem cell transplantation.
Transpl Infect Dis 2010: 12: 284–291. All rights reserved. Abstract: Epstein–Barr virus (EBV) reactivation or infection after hematopoietic stem cell transplantation (HSCT) most often induces post‐transplant lymphoproliferative disease (PTLD), but it also may be associated with clinical symptoms such as pneumonia. Our aim was to investigate and describe the clinical manifestations of PTLD and PTLD accompanied by EBV‐associated pneumonia in 323 patients after HSCT. PTLD within extravisceral lymphoid tissue was identified in 7 cases (5 with CD20⁺ diffuse large B‐cell lymphoma, 1 with CD20⁺ polymorphic B‐cell hyperplasia, and 1 with CD3⁺CD45RO⁺ peripheral T‐cell lymphoma unspecified). Six of the patients with PTLD were EBV positive. Three patients had EBV‐associated pneumonia, and chest computed tomography revealed multifocal patchy and diffuse ground‐glass attenuation in both lungs. EBV‐DNA was positive in bronchoalveolar lavage (BAL) fluid, which contained mainly CD3⁺ T cells but no CD19⁺ or CD20⁺ B cells. Lung biopsy showed interstitial intra‐alveolar infiltrates of mainly CD3⁺ T cells and some CD68⁺ macrophages without CD19⁺ and CD20⁺ B cells. The patients with PTLD accompanied by EBV‐associated pneumonia developed hyperpyrexia and dyspnea, which progressed rapidly, and eventually all died within 2 weeks of the onset of PTLD. EBV‐associated PTLD accompanied by EBV‐associated pneumonia after HSCT is rare. Cytology of BAL fluid and lung biopsy may help establish the diagnosis.     

The current role of T cell depletion in paediatric stem cell transplantation

Haematopoeitic stem cell transplantation (HSCT) is a curative procedure for children with malignant and non‐malignant haematological disease as well as an expanding number of inherited disorders. Most patients lack a human leucocyte antigen‐matched related donor, making alternative donors, such as closely matched unrelated donors, unrelated umbilical cord blood donations and haploidentical donors, necessary choices. T cell depletion (TCD) has been employed for over 30 years to reduce the risk of graft‐versus‐host disease (GvHD) associated with non‐genoidentical HSCT. However, until recently overall survival had not improved with TCD due to increased rates of graft failure, disease relapse and delayed immune reconstitution. Recent advances in graft manipulation and reduced toxicity conditioning regimens have offered renewed hope, particularly for children undergoing haploidentical HSCT, where encouraging results have been achieved using negative depletion techniques to retain beneficial accessory cells, which speed immune reconstitution and reduce disease relapse. Translational work building on megadose CD34⁺ selected grafts, including pathogen‐specific immunotherapy, suicide gene therapy and other adoptive cellular immunotherapies, has also offered improved outcomes for such patients.     

Immunologic effects of prophylactic donor lymphocyte infusion after allogeneic marrow transplantation for multiple myeloma

Reconstitution of T-cell immunity after bone marrow transplantation (BMT) is often delayed, resulting in a prolonged period of immunodeficiency. Donor lymphocyte infusion (DLI) has been used to enhance graft-versus-leukemia activity after BMT, but the effects of DLI on immune reconstitution have not been established. We studied 9 patients with multiple myeloma who received myeloablative therapy and T-cell-depleted allogeneic BMT followed 6 months later by infusion of lymphocytes from the same donor. DLI consisted of 3 x 10(7) CD4(+) donor T cells per kilogram obtained after in vitro depletion of CD8(+) cells. Cell surface phenotype of peripheral lymphocytes, T-cell receptor (TCR) V beta repertoire, TCR rearrangement excision circles (TRECs), and hematopoietic chimerism were studied in the first 6 months after BMT and for 1 year after DLI. These studies were also performed in 7 patients who received similar myeloablative therapy and BMT but without DLI. Phenotypic reconstitution of T and natural killer cells was similar in both groups, but patients who received CD4(+) DLI developed increased numbers of CD20(+) B cells. TCR V beta repertoire complexity was decreased at 3 and 6 months after BMT but improved more rapidly in patients who received DLI (P =.01). CD4(+) DLI was also associated with increased numbers of TRECs in CD3(+) T cells (P <.001) and with conversion to complete donor hematopoiesis (P =.05). These results provide evidence that prophylactic infusion of CD4(+) donor lymphocytes 6 months after BMT enhances reconstitution of donor T cells and conversion to donor hematopoiesis as well as promoting antitumor immunity.     

Rapid immune reconstitution after a reduced-intensity conditioning regimen and a CD3-depleted haploidentical stem cell graft for paediatric refractory haematological malignancies

The main obstacles to successful haploidentical haematopoietic stem cell transplantation from a mismatched family member donor are delayed immune reconstitution, vulnerability to infections and severe graft-versus-host disease (GvHD). We designed a reduced-intensity conditioning regimen that excluded total body irradiation and anti-thymocyte globulin in order to expedite immune reconstitution after a CD3-depleted haploidentical stem cell transplant. This protocol was used to treat 22 paediatric patients with refractory haematological malignancies. After transplantation, 91% of the patients achieved full donor chimaerism. They also showed rapid recovery of CD3(+) T-cells, T-cell receptor (TCR) excision circle counts, TCRbeta repertoire diversity and natural killer (NK)-cells during the first 4 months post-transplantation, compared with those results from a group of patients treated with a myeloablative conditioning regimen. The incidence and extent of viremia were limited and no lethal infection was seen. Only 9% of patients had grade 3 acute GvHD, while 27% patients had grade 1 and another 27% had grade 2 acute GvHD. This well-tolerated regimen appears to accelerate immune recovery and shorten the duration of early post-transplant immunodeficiency, thereby reducing susceptibility to viral infections. Rapid T-cell reconstitution, retention of NK-cells in the graft and induction of low grade GvHD may also enhance the potential anti-cancer immune effect.     

Immune reconstitution after T-cell replete HLA-haploidentical transplantation

Impaired immune reconstitution has been one of the perceived limitations of alternative donor transplantation. However, modern transplantation platforms such as HLA-haploidentical transplantation with either post-transplantation cyclophosphamide or with anti-thymocyte globulin combined with intense immunosuppression may be associated with robust immune recovery as inferred by low rate of infectious mortality and post-transplantation lymphoproliferative disease. Here, we review the data on immune reconstitution including individual cell subsets, the effect of reconstitution on outcomes, and comparative studies using these commonly utilized T-cell replete HLA-haploidentical platforms. We find robust recovery of neutrophils, natural killer cells, CD8⁺ T-cells, and B-cells, with delayed CD4⁺ T-cell recovery comparable to that after HLA-matched transplantation. In addition, while viral reactivations and infections appear more common after HLA-haploidentical when compared with HLA-matched transplantation, infectious mortality remains low likely due to modern cytomegalovirus monitoring, preemptive treatment, as well as relative frequency of nonlethal viral infections like polyomavirus hominis 1 (BK virus). Higher graft cell doses also appear to be associated with faster recovery without concomitant increases in lethal graft-vs-host disease. Finally, despite rapid numerical return of natural killer cells post-transplant, phenotypically they retain immaturity markers till day 180 or more after transplantation, which suggests an avenue for future research to improve outcomes further.     

Infusion of CD3/CD28 costimulated umbilical cord blood T cells at the time of single umbilical cord blood transplantation may enhance engraftment

Limited cell numbers in umbilical cord blood (UCB) grafts present a major impediment to favorable outcomes in adult transplantation, largely related to delayed or failed engraftment. The advent of UCB transplantation (UCBT) using two grafts successfully circumvents this obstacle, despite the engraftment of only one unit. Preclinical models suggested that the addition of UCB T cells at the time of transplant can enhance engraftment. We tested whether ex vivo activation by CD3/CD28 costimulation and expansion of T cells from a single UCB graft would be safe and feasible in adults with advanced hematologic malignancies, with an overall objective of optimizing engraftment in single unit UCBT. In this phase 1 study, recipients of single UCB units were eligible if the unit was stored in two adequate fractions. Dose limiting toxicity was defined as grade 3 or grade 4 GVHD within 90 days of UCBT. Four patients underwent UCBT; all were treated at the first dose level (10⁵cells/kg). At the 10⁵cells/kg dose level two subjects experienced grade 3 intestinal GVHD, thus meeting stopping criteria. For three subjects, neutrophil engraftment was early (12, 17, and 20 days), while one subject experienced primary graft failure. We observed early donor T cell trafficking and found that expanded T cells produced supraphysiologic levels of cytokines relevant to engraftment and to lymphoid differentiation and function. Taken together, these preliminary data suggest rapid engraftment in recipients of a single UCBT combined with relatively low doses of activated T cells, though potentially complicated by severe GVHD. Am. J. Hematol. 91:453–460, 2016. © 2016 Wiley Periodicals, Inc.     

Successful haploidentical bone marrow transplantation in Fanconi anemia

A 10-year-old girl with Fanconi anemia and severe aplastic anemia underwent a haploidentical BMT from her mother due to lack of a matched family donor. T cell depletion was done by positive selection of CD34 cells with immunomagnetic beads. Due to graft rejection a second haploidentical BMT from the father was successfully undertaken. No immunosuppression was given after the transplant. Immunological reconstitution took approximately 6 months, with no GVHD or severe infections. Such a transplant, containing a large purified CD34 cell fraction with a minimal number of added T cells, should be considered as the treatment of choice for patients with Fanconi anemia if no HLA matched donor is available.     

Massive activation-induced cell death of alloreactive T cells with apoptosis of bystander postthymic T cells prevents immune reconstitution in mice with graft-versus-host disease.

After hematopoietic stem cell transplantation, the persistence and expansion of grafted mature postthymic T cells allow both transfer of donor immunologic memory and generation of a diverse T repertoire. This thymic-independent process, which is particularly important in humans, because most transplant recipients present severe thymus atrophy, is impaired by graft-versus-host disease (GVHD). The goal of this study was to decipher how GVHD influences the fate of grafted postthymic T cells. Two major findings emerged. First, we found that, after a brisk proliferation phase, alloreactive antihost T cells underwent a massive activation-induced cell death (AICD). For both CD4(+) and CD8(+) T cells, the Fas pathway was found to play a major role in this AICD: alloreactive T cells upregulated Fas and FasL, and AICD of antihost T cells was much decreased in the case of lpr (Fas-deficient) donors. Second, whereas non-host-reactive donor T cells neither upregulated Fas nor suffered apoptosis when transplanted alone, they showed increased membrane Fas expression and apoptosis when coinjected with host-reactive T cells. We conclude that GVHD-associated AICD of antihost T cells coupled with bystander lysis of grafted non-host-reactive T cells abrogate immune reconstitution by donor-derived postthymic T lymphocytes. Furthermore, we speculate that massive lymphoid apoptosis observed in the acute phase of GVHD might be responsible for the occurrence of autoimmunity in the chronic phase of GVHD.