Early and Long-Term Impaired T Lymphocyte Immune Reconstitution after Cord Blood Transplantation with Antithymocyte Globulin

Phase 2 trial of cyclosporine-A, mycophenolate mofetil, and tocilizumab GVHD prophylaxis in cord blood transplantation

ABSTRACT

Double-unit cord blood transplantation (dCBT) has been associated with high rates of progression-free survival (PFS) in adults with hematologic malignancies but also with relatively high rates of acute graft-versus-host disease (aGVHD). We conducted a single-arm, phase 2 clinical trial that investigated the addition of tocilizumab, an interleukin-6 receptor blocker, to cyclosporine-A (CSA) and mycophenolate mofetil (MMF) for aGVHD prophylaxis after intermediate-intensity dCBT. A total of 45 patients (median age, 47 years; range, 27-60 years; 80% acute leukemia; median hematopoietic cell transplant-comorbidity index, 2) were enrolled from March 2018 to March 2021. Transplant outcomes were compared with 39 previous CSA and MMF dCBT controls with similar inclusion criteria. Tocilizumab recipients had less pre-engraftment syndrome (38%; 95% confidence interval [CI], 24-52 vs 72%; 95% CI, 54-84; P < .001) but inferior day 45 neutrophil engraftment (93%; median, 25.5 days vs 97%; median, 22 days; P = .009]. The primary end point of day 100 grade 2 to 4 aGVHD was no different between groups (71%; 95% CI, 55-82 with tocilizumab vs 82%; 95% CI, 65-91; P = .11). However, there was a trend toward a lower day 100 incidence of stage 1 to 4 lower gastrointestinal aGVHD with tocilizumab (16%; 95% CI, 7-28 vs 33%; 95% CI, 19-48; P = .059). There were no significant differences in the 3-year incidences of relapse, transplant-related mortality, PFS, or overall survival between the groups. Tocilizumab recipients exhibited a distinct pattern of gut microbiome disruption. In summary, tocilizumab-based GVHD prophylaxis delayed neutrophil recovery without a significant reduction in aGVHD and had no survival benefit after dCBT. Investigation of alternative strategies to prevent severe aGVHD after dCBT is warranted. This trial was registered at www.clinicaltrials.gov as #NCT03434730.

Haploidentical versus Cord Blood Transplantation in Pediatric AML. A Retrospective Outcome Analysis on Behalf of the Pediatric Subcommittee of GETH (Grupo Español de Trasplante Hematopoyético)

Haploidentical stem cell transplantation (Haplo-SCT) and cord blood transplantation (CBT) are both effective alternative treatments in patients suffering from acute myeloid leukemia (AML) and lacking a matched HLA donor. In the last years, many centers have abandoned CBT procedures mostly due to concern about poorer immune recovery compared with Haplo-SCT. We conducted a retrospective multicenter study comparing the outcomes using both alternative approaches in AML. A total of 122 transplants (86 Haplo-SCTs and 36 CBTs) from 12 Spanish centers were collected from 2007 to 2021. Median age at hematopoietic stem cell transplantation (HSCT) was 7 years (0.4-20). Thirty-nine patients (31.9%) showed positive minimal residual disease (MRD) at HSCT and a previous HSCT was performed in 37 patients (30.3%). The median infused cellularity was 14.4 × 106/kg CD34+ cells (6.0-22.07) for Haplo-SCT and 4.74 × 105/kg CD34+ cells (0.8-9.4) for CBT. Median time to neutrophil engraftment was 14 days (7-44) for Haplo-SCT and 17 days (8-29) for CBT (P = .03). The median time to platelet engraftment was 14 days (6-70) for Haplo-SCT and 43 days (10-151) for CBT (P < .001). Graft rejection was observed in 13 Haplo-SCTs (15%) and in 6 CBTs (16%). The cumulative incidence of acute graft versus host disease (GvHD) grades II-IV was 54% and 51% for Haplo-SCT and CBT, respectively (P = .50). The cumulative incidence of severe acute GvHD (grades III-IV) was 22% for Haplo-SCT and 25% for CBT (P = .90). There was a tendency to a higher risk of chronic GvHD in the Haplo-SCT group being the cumulative incidence of 30% for Haplo-SCT and 12% for CBT (P = .09). The cumulative incidence of relapse was 28% and 20% for Haplo-SCT and CBT, respectively (P = .60). We did not observe statistically significant differences in outcome measures between Haplo-SCT and CBT procedures: 5-year overall survival (OS) was 64% versus 57% (P = .50), 5-year disease-free survival (DFS) 58% versus 57% (P = .80), GvHD-free and relapse-free survival (GFRFS) 41% versus 54% (P = .30), and cumulative incidence of transplant-related mortality (TRM) 14% versus 15% (P = .80), respectively. In the multivariate analysis, MRD positivity and a disease status >CR1 at the time of HSCT were significantly associated with poorer outcomes (P < .05). In conclusion, our study supports that both haploidentical and cord blood transplantation show comparable outcomes in pediatric AML patients. We obtained comparable survival rates, although CBT showed a trend to lower rates of chronic GvHD and higher GFRFS, demonstrating that it should still be considered a valuable option, particularly for pediatric patients.

Unsupervised Clustering Analysis of Regimen and HLA Characteristics in Pediatric Umbilical Cord Blood Transplantation

HLA matching is a critical factor in allogeneic unrelated hematopoietic cell transplantation (HCT) because of its impact on post-transplantation survival and quality of life. Umbilical cord blood transplantation (UCBT) offers unique advantages, but determining the optimal approach to graft selection and immunosuppression remains challenging. Unsupervised clustering, a machine learning technique, has potential for analyzing transplantation outcomes, but its application in investigating leukemia outcomes has been limited. This study aimed to identify optimal combinations of HLA/ killer immunoglobulin receptor (KIR) donor-patient pairing, conditioning, and immunosuppressive regimens in pediatric patients with acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML) undergoing UCBT. Outcome data for single, unmanipulated UCBT in pediatric AML (n = 708) and ALL (n = 1034) patients from the Eurocord/EBMT registry were analyzed using unsupervised clustering. Resulting clusters were used to inform post hoc competing risks and Kaplan-Meier analyses. In AML, single HLA-C mismatches with other loci fully matched (7/8) were associated with poorer relapse-free survival (RFS) (P = .039), but a second mismatch at any other locus counteracted this effect. In ALL, total body irradiation (TBI) effectively prevented relapse mortality (P = .007). KIR/HLA-C match status affected RFS in AML (P = .039) but not in ALL (P = .8). Administration of antithymocyte globulin (ATG) substantially increased relapse, with no relapses occurring in the 85 patients who did not receive ATG. Our unsupervised clustering analyses generate several key statistical and mechanistic hypotheses regarding the relationships between HLA matching, conditioning regimens, immunosuppressive therapies, and transplantation outcomes in pediatric AML and ALL patients. HLA-C and KIR combinations significantly impact RFS in pediatric AML but not in ALL. ATG use in fully matched pediatric patients is associated with late-stage relapse. TBI regimens appear to be beneficial in ALL, with efficacy largely independent of histocompatibility variables. These findings reflect the distinct genetic and biological profiles of AML and ALL.

Immune reconstitution after single-unit umbilical cord blood transplantation using anti-thymoglobulin and myeloablative conditioning in adults with hematological malignancies

This study aimed to investigate the kinetics of immune recovery following umbilical cord blood transplantation (UCBT) in adults who received a myeloablative conditioning (MAC) regimen and antithymocyte globulin (ATG). While the immune recovery kinetics has been extensively studied in pediatric UCBT recipients, limited data exist for adults. We conducted a comprehensive analysis of 221 consecutive adult patients who underwent UCBT with MAC and ATG at a single institution. Our objective was to evaluate the influence of patient, disease, and transplant factors, along with acute graft-versus-host disease (aGVHD), on immune reconstitution and overall survival. Our findings confirm a delayed recovery of T cells, while B and NK cell reconstitution exhibited rapid progress, with NK cell counts reaching normal levels within 3 months post-transplantation and B cells within 6 months. Within CD3+ T cells, CD8+ T cells also experienced a delayed recovery (12 months), but to a lesser extent compared to CD4+ T cells (18 months). Delayed immune recovery of T-cell subsets was associated with the development of aGVHD grade II-IV, older age, CMV negativity, and a female donor. Patients with lymphoproliferative diseases showed slower NK cell recovery. Our study demonstrates that adult patients undergoing MAC with ATG and receiving a single unit UCBT for hematologic malignancies experienced rapid reconstitution of NK and B cells. However, T cell recovery, particularly CD4+ T cells, was significantly delayed. To enhance T cell recovery, it may be crucial to consider UCB units with higher cellularity and optimize ATG doses in conditioning.

Cord Blood Transplantation for Very Early-Onset Inflammatory Bowel Disease Caused by Interleukin-10 Receptor Deficiency

PURPOSE

Interleukin-10 receptor (IL-10R) deficiency can result in life-threatening very early-onset inflammatory bowel disease (VEO-IBD). Umbilical cord blood transplantation (UCBT) is a curative therapy for patients with IL-10R deficiency. This study aimed to investigate the efficacy of UCBT in treating IL-10R deficiency and develop a predictive model based on pre-transplant factors.

METHODS

Eighty patients with IL-10R deficiency who underwent UCBT between July 2015 and April 2023 were retrospectively analyzed. Cox proportional hazards regression and random survival forest were used to develop a predictive model.

RESULTS

Median age at transplant was 13.0 months (interquartile range [IQR], 8.8-25.3 months). With a median follow-up time of 29.4 months (IQR, 3.2-57.1 months), the overall survival (OS) rate was 65.0% (95% confidence interval [CI], 55.3%-76.3%). The engraftment rate was 85% (95% CI, 77%-93%). The cumulative incidences of acute and chronic graft-versus-host disease were 48.2% (95% CI, 37.1%-59.4%) and 12.2% (95% CI, 4.7%-19.8%), respectively. VEO-IBD-associated clinical symptoms were resolved in all survivors. The multivariate analysis showed that IL-6 and stool occult blood were independent prognostic risk factors. The multivariate Cox proportional hazards regression model with stool occult blood, length- or height-for-age Z-score, medical history of sepsis, and cord blood total nucleated cells showed good discrimination ability, with a bootstrap concordance index of 0.767-0.775 in predicting OS.

CONCLUSION

Better inflammation control before transplantation and higher cord blood total nucleated cell levels can improve patient prognosis. The nomogram can successfully predict OS in patients with IL-10R deficiency undergoing UCBT.

[Single non-blood-related umbilical cord blood transplantation using a reduced-intensity conditioning regimen for the treatment of severe aplastic anemia]

Objective: To evaluated the clinical efficacy of a reduced-intensity preconditioning regimen for single non-blood-related umbilical cord blood transplantation (sUCBT) in the treatment of severe aplastic anemia (SAA) . Methods: The clinical data of 63 patients with SAA who underwent sUCBT from January 2021 to July 2023 at the Department of Hematology of the First Affiliated Hospital of USTC were retrospectively analyzed. Fifty-two patients received total body irradiation/total bone marrow irradiation (TMI) combined with fludarabine or a cyclophosphamide- conditioning regimen (non-rATG group) , while 11 patients received rabbit anti-human thymocyte immunoglobulin (rATG) combined with TMI, fludarabine, or the cyclophosphamide-conditioning regimen (rATG group) . All patients received cyclosporine A and mycophenolate mofetil for graft-versus-host disease (GVHD) prophylaxis. Complications post-transplantation and long-term survival were compared between the two groups. Results: The baseline parameters were balanced between the two groups (P>0.05) . In the rATG group, all patients achieved stem cell engraftment, and in the non-rATG group, five patients had primary graft failure. There was no significant difference in the cumulative incidence of neutrophil engraftment at 42 days after transplantation or platelet engraftment at 60 days between the two groups. The incidence of grade Ⅱ-Ⅳ acute GVHD in the rATG group was significantly lower than in the non-rATG group (10.0% vs. 46.2% , P=0.032) , and the differences in the cumulative incidences of grade Ⅲ/Ⅳ acute GVHD and 1-year chronic GVHD were not statistically significant (P=0.367 and P=0.053, respectively) . There were no significant differences in the incidences of pre-engraftment syndrome, bacterial bloodstream infections, cytomegalovirus viremia, or hemorrhagic cystitis between the two groups (P>0.05 for all) . The median follow-up time for surviving patients was 536 (61-993) days, and the 1-year transplantation related mortality (TRM) of all patients after transplantation was 13.0% (95% CI 6.7% -24.3% ) . Among the patients in the non-rATG and rATG groups, 15.5% (95% CI 8.1% -28.6% ) and 0% (P=0.189) , respectively, had mutations. The 1-year overall survival (OS) rate of all patients after transplantation was 87.0% (95% CI 75.7% -93.3% ) . The 1-year OS rates in the rATG group and non-rATG group after transplantation were 100% and 84.5% , respectively (95% CI 71.4% -91.9% ) (P=0.198) . Conclusion: The preliminary results of sUCBT with a low-dose irradiation-based reduced-intensity conditioning regimen with fludarabine/cyclophosphamide for the treatment of patients with SAA showed good efficacy. Early application of low-dose rATG can reduce the incidence of acute GVHD after transplantation without increasing the risk of implantation failure or infection.

[Efficacy analysis of anti-thymocyte globulin regimens with different timing strategies for matched sibling donor hematopoietic stem cell transplantation]

Objective: To compare the effects of two administration time strategies for rabbit antihuman thymocyte immunoglobulin (rATG) of 5mg/kg total dose in matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) . Methods: This study retrospectively analyzed the clinical data of 32 patients who received MSD-HSCT with 5 mg/kg rATG conditioning regimen at the Department of Hematology of the First Medical Center of the People's Liberation Army General Hospital from October 2020 to April 2022. The patients were classified into two groups: the 4d-rATG group (16 cases), who received antithymocyte globulin (ATG) from day -5 to day -2, and the 2d-rATG group (16 cases), who received ATG from day -5 to day -4. Between the two groups, the transplantation outcomes, serum concentrations of active antithymocyte globulin (ATG) in patients from -4 days to 28 days after graft infusion (+28 days), and the reconstitution of lymphocyte subsets on days +30, +60, and +90 were compared. Results: The cumulative incidences of acute graft-versus-host disease at 100 days after graft infusion were 25.0% (95% CI 7.8% -47.2% ) and 18.8% (95% CI 4.6% -40.2% ) (P=0.605) in the 4d-rATG group and 2d-rATG group, respectively. The 1-year cumulative incidences of chronic graft-versus-host disease were 25.9% (95% CI 8.0% -48.6% ) and 21.8% (95% CI 5.2% -45.7% ) (P=0.896). The 1-year cumulative incidence of relapse was 37.5% (95% CI 18.9% -65.1% ) and 14.6% (95% CI 3.6% -46.0% ) (P=0.135), and the 1-year probabilities of overall survival were 75.0% (95% CI 46.3% -89.8% ) and 100% (P=0.062). The total area under the curve (AUC) of serum active ATG was 36.11 UE/ml·d and 35.89 UE/ml·d in the 4d-rATG and 2d-rATG groups, respectively (P=0.984). The AUC was higher in the 4d-rATG group than that in the 2d-rATG group (20.76 UE/ml·d vs 15.95 UE/ml·d, P=0.047). Three months after graft infusion, the average absolute count of CD8(+) T lymphocytes in the 4d-rATG group was lower than that in the 2d-rATG group (623 cells/μl vs 852 cells/μl, P=0.037) . Conclusion: The efficiencies of GVHD prophylaxis in MSD-PBSCT receiving 4d-ATG regimen and the 2d-rATG regimen were found to be similar. The reconstruction of CD8(+)T lymphocytes in the 2d-rATG group was better than that in the 4d-rATG group, which is related to the lower AUC of active ATG after transplantation.

Transplant for non-malignant disorders: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the role of alternative donors, stem cell sources and graft engineering

Hematopoietic stem cell transplantation (HSCT) is curative for many non-malignant disorders. As HSCT and supportive care technologies improve, this life-saving treatment may be offered to more and more patients. With the development of new preparative regimens, expanded alternative donor availability, and graft manipulation techniques, there are many options when choosing the best regimen for patients. Herein the authors review transplant considerations, transplant goals, conditioning regimens, donor choice, and graft manipulation strategies for patients with non-malignant disorders undergoing HSCT.

Impact of posttransplant cyclophosphamide on the outcome of patients undergoing unrelated single-unit umbilical cord blood transplantation for pediatric acute leukemia

Background

Umbilical cord blood transplantation (UCBT) from unrelated donors is one of the successful treatments for acute leukemia in childhood. The most frequent side effect of UCBT is peri-engraftment syndrome (PES), which is directly associated with the greater prevalence of acute and chronic graft-versus-host-disease (aGvHD and cGvHD). In haploidentical stem cell transplantation, posttransplant cyclophosphamide (PTCY) has been demonstrated to be an effective method against GvHD. However, the effects of PTCY as a GvHD prophylactic in UCBT had not been investigated. This study aimed to evaluate the effects of PTCY on the outcomes of UCBT for pediatric acute leukemia.

Methods

This retrospective study included 52 children with acute leukemia who underwent unrelated single-unit UCBT after myeloablative conditioning regimens. The results from the PTCY and non-PTCY groups were compared.

Results

The incidence of transplantation-related mortality in non-PTCY and PTCY were 5% and 10% (p = 0.525), respectively. The incidence of relapse in non-PTCY and PTCY were 5% and 23% (p = 0.095), respectively. Second complete remission status (CR2) was an independent risk factor for relapse-free survival (hazard ratio = 9.782, p = 0.001). The odds ratio for sepsis or bacteremia incidence was significantly greater in the PTCY group (9.524, p = 0.017). PTCY group had increased rates of cytomegalovirus activity and fungal infection. The incidence of PES, aGvHD, cGvHD, and hemorrhagic cystitis in the PTCY group was lower than that in the non-PTCY group, although it was not significantly different. Additionally, higher doses of PTCY (29 mg/kg and 40 mg/kg) were associated with lower incidences of aGvHD and severe GvHD (65% and 29%, respectively) than lower doses (93% and 57%, respectively). Engraftment time and graft failure incidence were similar across groups.

Conclusion

The results support the safety and efficiency of PTCY as part of PES controlling and GvHD prophylaxis in single-unit UCBT for children with acute leukemia. A PTCY dosage of 29 mg/kg to 40 mg/kg appears to be more effective in GvHD prophylaxis for UCBT patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10309-9.

Umbilical cord blood: an undervalued and underutilized resource in allogeneic hematopoietic stem cell transplant and novel cell therapy applications

PURPOSE OF REVIEW

The purpose of this review is to primarily discuss the unwarranted decline in the use of umbilical cord blood (UCB) as a source of donor hematopoietic stem cells (HSC) for hematopoietic cell transplantation (HCT) and the resulting important implications in addressing healthcare inequities, and secondly to highlight the incredible potential of UCB and related birthing tissues for the development of a broad range of therapies to treat human disease including but not limited to oncology, neurologic, cardiac, orthopedic and immunologic conditions.

RECENT FINDINGS

When current best practices are followed, unrelated donor umbilical cord blood transplant (CBT) can provide superior quality of life-related survival compared to other allogeneic HSC donor sources (sibling, matched or mismatched unrelated, and haploidentical) through decreased risks of relapse and chronic graft vs. host disease. Current best practices include improved UCB donor selection criteria with consideration of higher resolution human leukocyte antigen (HLA) typing and CD34+ cell dose, availability of newer myeloablative but reduced toxicity conditioning regimens, and rigorous supportive care in the early posttransplant period with monitoring for known complications, especially related to viral and other infections that may require intervention. Emerging best practice may include the use of ex vivo expanded single-unit CBT rather than double-unit CBT (dCBT) or 'haplo-cord' transplant, and the incorporation of posttransplant cyclophosphamide as with haploidentical transplant and/or incorporation of novel posttransplant therapies to reduce the risk of relapse, such as NK cell adoptive transfer. Novel, non-HCT uses of UCB and birthing tissue include the production of UCB-derived immune effector cell therapies such as unmodified NK cells, chimeric antigen receptor-natural killer cells and immune T-cell populations, the isolation of mesenchymal stem cells for immune modulatory treatments and derivation of induced pluripotent stem cells haplobanks for regenerative medicine development and population studies to facilitate exploration of drug development through functional genomics.

SUMMARY

The potential of allogeneic UCB for HCT and novel cell-based therapies is undervalued and underutilized. The inventory of high-quality UCB units available from public cord blood banks (CBB) should be expanding rather than contracting in order to address ongoing healthcare inequities and to maintain a valuable source of cellular starting material for cell and gene therapies and regenerative medicine approaches. The expertise in Good Manufacturing Practice-grade manufacturing provided by CBB should be supported to effectively partner with groups developing UCB for novel cell-based therapies.

Unmanipulated haploidentical haematopoietic cell transplantation with radiation-free conditioning in Fanconi anaemia: A retrospective analysis from the Chinese Blood and Marrow Transplantation Registry Group

Haematopoietic cell transplantation (HCT) is the only curative treatment for haematological complications in patients with Fanconi anaemia (FA). Haploidentical (haplo-) HCT is a promising alternative for FA. We aimed to analyse the outcomes of unmanipulated haplo-HCT in patients with FA with radiation-free conditioning. A total of 56 patients from 11 centres between 2013 and 2021 in China were retrospectively analysed. The mean (SD) cumulative incidence was 96.4% (0.08%) for 30-day neutrophil engraftment and 85.5% (0.24%) for 100-day platelet engraftment. With a median (range) follow-up of 2.4 (0.2-5.8) years, favourable mean (SD) overall survival of 80.9% (5.5%) and event-free survival of 79.3% (5.6%) were achieved. The mean (SD) incidences of acute graft-versus-host disease (aGvHD) Grade II-IV and Grade III-IV were 55.4% (0.45%) and 42.9 (0.45%) respectively. The mean (SD) cumulative incidence of 3-year chronic graft-versus-host disease (cGvHD) was 34.7% (0.86%) and that of moderate-to-severe cGvHD was 9.0% (0.19%). Our data demonstrate that in unmanipulated haplo-HCT for patients with FA, radiation-free regimens based on fludarabine and low-dose cyclophosphamide ± busulfan achieved favourable engraftment and survival with relatively high incidences of aGvHD and cGvHD. These results prompt the use of low-intensity conditioning without radiation and intensive GvHD prophylaxis when considering unmanipulated haplo-HCT in patients with FA.

Real-world efficacy of letermovir prophylaxis for cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation: A single-center retrospective analysis

INTRODUCTION

Cytomegalovirus (CMV) infection is a common complication following allogeneic hematopoietic stem cell transplantation (aHSCT) and is associated with increased mortality. Letermovir (LET) is a novel antiviral drug used to prevent CMV infection.

METHODS

We analyzed 111 consecutive patients who underwent aHSCT, retrospectively, to evaluate the efficacy of LET prophylaxis for clinically significant CMV infection (csCMVi) in real-world situations. In addition, we analyzed the influence of LET on transplant outcomes. Thirty-eight patients who were administered LET prophylactically were compared with 73 patients without LET prophylaxis after aHSCT.

RESULTS

On day 180, the cumulative incidence of csCMVi in patients who received LET prophylaxis was significantly lower than that in patients without LET prophylaxis (29.7% vs. 56.2%, P < 0.001). Among the patients who developed csCMVi, the interval from aHSCT to the initiation of preemptive therapy was significantly longer in patients who received LET prophylaxis than in those who did not (129.5 days vs. 42 days, P < 0.001). The six-month overall survival was 86.1% in patients who received LET prophylaxis and 66.8% in the non-LET group (P = 0.035).

CONCLUSION

LET prophylaxis was highly effective in preventing csCMVi and could potentially improve transplant outcomes, particularly when initiated early after transplantations.

Cord-Blood Engraftment Using an Enhanced Dual-Conditioning Regimen for Malignant Hematologic Diseases

To explore a more effective conditioning regimen for umbilical cord blood transplantation (UCBT) to treat hematologic malignancies, we conducted a cohort study of a fludarabine/busulfan/cytarabine plus cyclophosphamide 200 mg/kg regimen. Forty-two consecutive patients with leukemia, myelodysplastic syndrome, or lymphoma received the regimen. The median number of infused total nucleated cells per kilogram was 5.5 × 10⁷ (1.81–20.6), the median number of infused CD34⁺ cells per kilogram was 1.58 × 10⁵ (0.58–6.6), and the median follow-up for surviving patients was 37 months (4.0–79.5 months). The cumulative incidence of neutrophil engraftment at 31 days was 100% [95% confidence interval (CI): 0.9159–1.0], and the median time to neutrophil engraftment was 19 days. The cumulative incidence of nonrelapse mortality was 12.76% (95% CI: 0.0455–0.2356) at 180 days and 3 years. The 3-year overall survival (OS) and disease-free survival (DFS) rates were 71.6% and 59.6%, respectively. Especially in patients who received transplants in the early and intermediate stages, the 3-year OS and DFS rates were 90.3% (95% CI: 0.805–1.0) and 76.2% (95% CI: 0.608–0.956), respectively. The regimen significantly improved engraftment and survival, indicating that the high graft failure of UCBT was caused by rejection.

Umbilical cord blood transplantation: Still growing and improving

Umbilical cord blood transplantation (UCBT) has been performed in the clinic for over 30 years. The biological and immunological characteristics of umbilical cord blood (UCB) have been re-recognized in recent years. UCB, previously considered medical waste, is rich in hematopoietic stem cells (HSCs), which are naïve and more energetic and more easily expanded than other stem cells. UCB has been identified as a reliable source of HSCs for allogeneic hematopoietic stem cell transplantation (allo-HSCT). UCBT has several advantages over other methods, including no harm to mothers and donors, an off-the-shelf product for urgent use, less stringent HLA match, lower incidence and severity of chronic graft-vs-host disease (GVHD), and probably a stronger graft-vs-leukemia effect, especially for minimal residual disease-positive patients before transplant. Recent studies have shown that the outcome of UCBT has been improved and is comparable to other types of allo-HSCT. Currently, UCBT is widely used in malignant, nonmalignant, hematological, congenital and metabolic diseases. The number of UCB banks and transplantation procedures increased exponentially before 2013. However, the number of UCBTs increased steadily in Asia and China but decreased in the United States and Europe year-on-year from 2013 to 2019. In this review, we focus on the development of UCBT over the past 30 years, the challenges it faces and the strategies for future improvement, including increasing UCB numbers, cord blood unit selection, conditioning regimens and GVHD prophylaxis for UCBT, and management of complications of UCBT.

Guidelines for the Prevention and Management of Graft-versus-Host Disease after Cord Blood Transplantation

The incidence of graft-versus-host disease (GVHD) after cord blood (CB) transplantation (CBT) is lower than expected given the marked degree of human leukocyte antigen (HLA)-mismatch of CB grafts. While the exact mechanism that underlies this biology remains unclear, it is hypothesized to be due to the low number of mostly immature T-cells infused as part of the graft1,2, and increased tolerance of CB-derived lymphocytes induced by the state of pregnancy. Nevertheless, acute GVHD (aGVHD) is a significant complication of CBT. In contrast, the incidence of chronic GVHD (cGVHD) following CBT is lower than what is observed following matched related or unrelated donor HSC transplantation (HSCT)3-6. This review outlines the guidelines for the prevention and management of acute and chronic GVHD following CBT.

Guidelines for Infection Prophylaxis, Monitoring and Therapy in Cord Blood Transplantation

As an alternative stem cell source, cord blood (CB) has many advantages. However, delayed engraftment, lack of transferred immunity, and a significant incidence of acute graft-versus-host disease renders CB transplant (CBT) recipients at high risk of infectious complications. This guidance written by CBT and infectious disease experts outlines evidence-based recommendations for the prevention and treatment of opportunistic infections in adult patients undergoing CBT. Topics addressed include bacterial, fungal, viral, pneumocystis jirovcii and toxoplasmosis prophylaxis, suggested PCR monitoring for viruses, therapy for the most commonly encountered infections after CBT. We review key concepts including the recent important role of letermovir in the prevention of CMV reactivation. In instances where there is a paucity of data, practice recommendations are provided, including the duration of antimicrobial prophylaxis.

Adult cord blood transplant results in comparable overall survival and improved GRFS vs matched related transplant

We compared outcomes among adult matched related donor (MRD) patients undergoing peripheral blood stem cell transplantation and adult patients undergoing double unit cord blood transplantation (CBT) at our center between 2010 and 2017. A total of 190 CBT patients were compared with 123 MRD patients. Median follow-up was 896 days (range, 169-3350) among surviving CBT patients and 1262 days (range, 249-3327) among surviving MRD patients. Comparing all CBT with all MRD patients, overall survival (OS) was comparable (P = .61) and graft-versus-host disease (GVHD) relapse-free survival (GRFS) was significantly improved among CBT patients (P = .0056), primarily because of decreased moderate to severe chronic GVHD following CBT (P < .0001; hazard ratio [HR], 3.99; 95% confidence interval [CI], 2.26-7.04). Among patients undergoing our most commonly used MRD and umbilical cord blood (CB) myeloablative regimens, OS was comparable (P = .136) and GRFS was significantly improved among CBT patients (P = .006). Cumulative incidence of relapse trended toward decreased in the CBT group (P = .075; HR, 1.85; CI 0.94-3.67), whereas transplant-related mortality (TRM) was comparable (P = .55; HR, 0.75; CI, 0.29-1.95). Among patients undergoing our most commonly used nonmyeloablative regimens, OS and GRFS were comparable (P = .158 and P = .697). Cumulative incidence of both relapse and TRM were comparable (P = .32; HR, 1.35; CI, 0.75-2.5 for relapse and P = .14; HR, 0.482; CI, 0.18-1.23 for TRM). Our outcomes support the efficacy of CBT and suggest that among patients able to tolerate more intensive conditioning regimens at high risk for relapse, CB may be the preferred donor source.

Robust CD4+ T-cell recovery in adults transplanted with cord blood and no antithymocyte globulin

Quality of immune reconstitution after cord blood transplantation (CBT) without antithymocyte globulin (ATG) in adults is not established. We analyzed immune recovery in 106 engrafted adult CBT recipients (median age 50 years [range 22-70]) transplanted for hematologic malignancies with cyclosporine/mycophenolate mofetil immunoprophylaxis and no ATG. Patients were treated predominantly for acute leukemia (66%), and almost all (96%) underwent myeloablation. Recovery of CD4+ T cells was faster than CD8+ T cells with median CD4+ T-cell counts exceeding 200/mm3 at 4 months. Early post-CBT, effector memory (EM), and central memory cells were the most common CD4+ subsets, whereas effector and EM were the most common CD8+ T-cell subsets. Naive T-cell subsets increased gradually after 6 to 9 months post-CBT. A higher engrafting CB unit infused viable CD3+ cell dose was associated with improved CD4+ and CD4+CD45RA+ T-cell recovery. Cytomegalovirus reactivation by day 60 was associated with an expansion of total, EM, and effector CD8+ T cells, but lower CD4+ T-cell counts. Acute graft-versus-host disease (aGVHD) did not significantly compromise T-cell reconstitution. In serial landmark analyses, higher CD4+ T-cell counts and phytohemagglutinin responses were associated with reduced overall mortality. In contrast, CD8+ T-cell counts were not significant. Recovery of natural killer and B cells was prompt, reaching medians of 252/mm3 and 150/mm3 by 4 months, respectively, although B-cell recovery was delayed by aGVHD. Neither subset was significantly associated with mortality. ATG-free adult CBT is associated with robust thymus-independent CD4+ T-cell recovery, and CD4+ recovery reduced mortality risk.

Case Report: A Novel IL2RG Frame-Restoring Rescue Mutation Mimics Early T Cell Engraftment Following Haploidentical Hematopoietic Stem Cell Transplantation in a Patient With X-SCID

Mutations of the interleukin 2 receptor γ chain (IL2RG) result in the most common form of severe combined immunodeficiency (SCID), which is characterized by severe and persistent infections starting in early life with an absence of T cells and natural killer cells, normal or elevated B cell counts and hypogammaglobulinemia. SCID is commonly fatal within the first year of life, unless the immune system is reconstituted by hematopoietic stem cell transplantation (HSCT) or gene therapy. We herein describe a male infant with X-linked severe combined immunodeficiency (X-SCID) diagnosed at 5 months of age. Genetic testing revealed a novel C to G missense mutation in exon 1 resulting in a 3' splice site disruption with premature stop codon and aberrant IL2 receptor signaling. Following the diagnosis of X-SCID, the patient subsequently underwent a TCRαβ/CD19-depleted haploidentical HSCT. Post transplantation the patient presented with early CD8⁺ T cell recovery with the majority of T cells (>99%) being non-donor T cells. Genetic analysis of CD4⁺ and CD8⁺ T cells revealed a spontaneous 14 nucleotide insertion at the mutation site resulting in a novel splice site and restoring the reading frame although defective IL2RG function was still demonstrated. In conclusion, our findings describe a spontaneous second-site mutation in IL2RG as a novel cause of somatic mosaicism and early T cell recovery following haploidentical HSCT.

Immune Reconstitution in Pediatric Patients Following Hematopoietic Cell Transplant for Non-malignant Disorders

Allogeneic hematopoietic cell transplant (HCT) is curative for pediatric patients with non-malignant hematopoietic disorders, including hemoglobinopathies, bone marrow failure syndromes, and primary immunodeficiencies. Early establishment of donor-derived innate and adaptive immunity following HCT is associated with improved overall survival, lower risk of infections and decreased incidence of graft failure. Immune reconstitution (IR) is impacted by numerous clinical variables including primary disease, donor characteristics, conditioning regimen, and graft versus host disease (GVHD). Recent advancements in HCT have been directed at reducing toxicity of conditioning therapy, expanding donor availability through use of alternative donor sources, and addressing morbidity from GVHD with novel graft manipulation. These novel transplant approaches impact the kinetics of immune recovery, which influence post-transplant outcomes. Here we review immune reconstitution in pediatric patients undergoing HCT for non-malignant disorders. We explore the transplant-associated factors that influence immunologic recovery and the disease-specific associations between IR and transplant outcomes.

[Optimization of ATG dose in haploid hematopoietic stem cell transplantation for hematologic malignancies]

Objective: To compare the clinical efficacy of different doses of rabbit antithymocyte globulin (rATG) in haplo-HSCT in the treatment of hematologic malignancies. Methods: Malignant hematological patients treated at our hospital from March 2013 to December 2018 were retrospectively analyzed. These patients were divided into three groups as per three doses of ATG (6 mg/kg, 7.5 mg/kg, and 9 mg/kg) in the conditioning regimens. The transplant outcomes were compared in terms of the occurrence of acute graft versus host disease (GVHD) , infection, and survival. Results: ①Total 288 patients were enrolled in the study, including 182 men and 106 women, with a median age of 18 (6-62) years. Total 110 patients were diagnosed with acute lymphoblastic leukemia (ALL) , 128 with acute myelogenous leukemia (AML) , 8 with chronic myeloid leukemia (CML) , 28 with myelodysplastic syndrome (MDS) , and 14 with mixed cell leukemia (MAL) . There were 159 patients in the ATG-6 group, 72 in the ATG-7.5 group, and 57 in the ATG-9 group. The median follow-up time of post transplantation was 14 (0.2-74) months. ②The incidence of neutrophil engraftment (96.9% , 97.2% , and 96.5% , respectively) and platelet engraftment (92.5% , 87.5% , and 86% , respectively) did not significantly differ among the ATG-6, ATG-7.5, and ATG-9 groups (P=0.972, P=0.276) . The incidence of grades 2-4 acute GVHD was 14.5% , 11.1% , and 8.8% in the three groups, respectively (P=0.493) , chronic GVHD incidence in the three group was 8.8% , 14.3% and 12.0% , respectively (P=0.493) . The infection rates of CMV and EBV in the ATG-9 group (77.2% and 12.5% ) were significantly higher than those in the ATG-6 (43.3% and 3.5% ) , and ATG -7.5 group (44.4% and 1.5% ) (P<0.001 and P=0.033, respectively) . ③Among the three groups, there were no significant difference in the 3-year overall survival [68.5% (95% CI 60.3% -77.9% ) , 60.1% (95% CI 48.3% -74.8% ) , 64.7% (95% CI 51.9% -80.7% ) ], cumulative incidences of relapse [34.6% (95% CI 34.3% -35.1% ) , 38.0% (95% CI 37.3% -38.7% ) , 20.6% (95% CI 20.0% -21.3% ) ], disease-free survival [53.3% (95% CI 44.9% -63.4% ) , 51.9% (95% CI 41% -65.8% ) , 63.9% (95% CI 51.9% -78.7% ) ] and non-relapse mortality [24.2% (95% CI 23.8% -24.5% ) , 26.0% (95% CI 25.4% -26.6% ) , 23.6% (95% CI 26.3% -28.2% ) ] (P=0.648, P=0.165, and P=0.486 and P=0.955) . Conclusion: Low dose (6 mg/kg) of rATG may increase the risk of grade Ⅱ-Ⅳ aGVHD, and a high dose (9 mg/kg) of ATG could significantly increase the risk of CMV and EBV infection. Median dose (7.5 mg/kg) of ATG is expected to reduce the incidence of moderate to severe aGVHD and viral infections without increasing the mortality.

Mass cytometry reveals immune signatures associated with cytomegalovirus (CMV) control in recipients of allogeneic haemopoietic stem cell transplant and CMV-specific T cells

Objectives

Cytomegalovirus (CMV) is known to have a significant impact on immune recovery post‐allogeneic haemopoietic stem cell transplant (HSCT). Adoptive therapy with donor‐derived or third‐party virus‐specific T cells (VST) can restore CMV immunity leading to clinical benefit in prevention and treatment of post‐HSCT infection. We developed a mass cytometry approach to study natural immune recovery post‐HSCT and assess the mechanisms underlying the clinical benefits observed in recipients of VST.

Methods

A mass cytometry panel of 38 antibodies was utilised for global immune assessment (72 canonical innate and adaptive immune subsets) in HSCT recipients undergoing natural post‐HSCT recovery (n = 13) and HSCT recipients who received third‐party donor‐derived CMV‐VST as salvage for unresponsive CMV reactivation (n = 8).

Results

Mass cytometry identified distinct immune signatures associated with CMV characterised by a predominance of innate cells (monocytes and NK) seen early and an adaptive signature with activated CD8⁺ T cells seen later. All CMV‐VST recipients had failed standard antiviral pharmacotherapy as a criterion for trial involvement; 5/8 had failed to develop the adaptive immune signature by study enrolment despite significant CMV antigen exposure. Of these, VST administration resulted in development of the adaptive signature in association with CMV control in three patients. Failure to respond to CMV‐VST in one patient was associated with persistent absence of the adaptive immune signature.

Conclusion

The clinical benefit of CMV‐VST may be mediated by the recovery of an adaptive immune signature characterised by activated CD8⁺ T cells.

Immune reconstitution following umbilical cord blood transplantation: IRES, a study of UK paediatric patients

To obtain a qualitative as well as quantitative view immune reconstitution following umbilical cord blood (UCB) transplantation of paediatric patients, we utilised a broad panel of flow cytometry markers to monitor the phenotypes of lymphoid and myeloid cells at 1-12 months post-transplant. Samples were received from 46 patients with a median age of 3.3 years and survival was 76% at 1 year. Monocytes were at similar or higher median levels than in adult controls at all times tested, with a high CD16+ proportion in the first 3 months. NK cells were also within adult ranges, with a CD56++ high proportion in the first 6 months. B cell recovery was seen from 2 months in most patients and T cells from 3 months, both were delayed with anti-thymocyte globulin (ATG) treatment. CD4:CD8 ratios were high in the first 6 months, and the proportion of T cells with recent thymic emigrant and naïve phenotypes rose from 3 months. NK and plasmacytoid dendritic cell numbers remained at reduced levels in patients not surviving to 1 year. Our results can serve as a useful reference for detailed monitoring of immune reconstitution in paediatric recipients of UCB.

Engraftment kinetics after transplantation of double unit cord blood grafts combined with haplo-identical CD34+ cells without antithymocyte globulin

Double unit cord blood (dCB) transplantation (dCBT) is associated with high engraftment rates but delayed myeloid recovery. We investigated adding haplo-identical CD34+ cells to dCB grafts to facilitate early haplo-identical donor-derived neutrophil recovery (optimal bridging) prior to CB engraftment. Seventy-eight adults underwent myeloablation with cyclosporine-A/mycophenolate mofetil immunoprophylaxis (no antithymocyte globulin, ATG). CB units (median CD34+ dose 1.1 × 10⁵/kg/unit) had a median 5/8 unit-recipient human leukocyte antigen (HLA)-match. Haplo-identical grafts had a median CD34+ dose of 5.2 × 10⁶/kg. Of 77 evaluable patients, 75 had sustained CB engraftment that was mediated by a dominant unit and heralded by dominant unit-derived T cells. Optimal haplo-identical donor-derived myeloid bridging was observed in 34/77 (44%) patients (median recovery 12 days). Other engrafting patients had transient bridging with second nadir preceding CB engraftment (20/77 (26%), median first recovery 12 and second 26.5 days) or no bridge (21/77 (27%), median recovery 25 days). The 2 (3%) remaining patients had graft failure. Higher haplo-CD34+ dose and better dominant unit-haplo-CD34+ HLA-match significantly improved the likelihood of optimal bridging. Optimally bridged patients were discharged earlier (median 28 versus 36 days). ATG-free haplo-dCBT can speed neutrophil recovery but successful bridging is not guaranteed due to rapid haplo-identical graft rejection.

Cord blood transplants supported by unrelated donor CD34+ progenitor cells

Alternative donor transplantation with the haplo-cord platform allows the use of a lower-dose single umbilical cord blood unit (CBU) by co-infusion of third-party CD34⁺-selected cells from a haploidentical relative, which provides early transient engraftment while awaiting durable CBU engraftment. In our experience, ~15% of patients lack a suitable haploidentical donor. Here we report 26 patients who underwent haplo-cord transplant using CD34⁺-selected partially matched unrelated donor grafts. Twenty-four were conditioned with fludarabine/melphalan +/- low-dose TBI (n = 16). Twenty-five received ATG and all received posttransplant tacrolimus and mycophenolate mofetil. Median time to neutrophil and platelet recovery was 11 and 18 days. CBU engraftment, with CD33 and CD3 >5% cord chimerism in the myeloid/lymphoid compartment by day +60, occurred in 20 of 24 patients (83%). Incidence of grade 2-4 acute graft-versus-host disease (GVHD) was 27% at day +100, and chronic GVHD was 4% at 1 year. Overall survival at 1 year was 54%. For patients in need of an alternative transplant who lack a haploidentical donor, haplo-cord transplantation using CD34⁺-selected partially matched unrelated donor grafts results in rapid engraftment with no increased rate of cord graft failure or GVHD.

Role of antithymocyte globulin in patients with hematologic diseases undergoing umbilical cord blood transplantation: A systematic review and meta-analysis

The role of antithymocyte globulin (ATG) in patients with hematologic diseases undergoing umbilical cord blood transplantation (UCBT) remains controversial. This systematic review and meta-analysis was conducted to comprehensively evaluate this issue. PubMed, Embase, and the Cochrane Library were systematically searched. Clinical studies reporting the impact of ATG- vs non-ATG-containing conditioning regimens on transplantation outcomes were identified. Twenty-five studies were included. ATG significantly prevented grade II-IV and grade III-IV acute graft-vs-host disease (GVHD) (11 studies, 5020 patients, HR: 0.49, 95% CI: 0.42-0.56, P < .001; 5 studies, 5490 patients, HR: 0.60, 95% CI: 0.46-0.80, P < .001) but not chronic GVHD (8 studies, 5952 patients, HR: 0.78, 95% CI: 0.51-1.20, P = .266). However, use of ATG was associated with increased transplantation-related mortality and inferior overall survival (9 studies, 4244 patients, HR: 1.79, 95% CI: 1.38-2.33, P < .001; 8 studies, 5438 patients, HR: 1.96, 95% CI: 1.56-2.46, P < .001). Our study did not recommend routine use of ATG in UCBT. Individualizing the ATG timing and dose based on patient characteristics to retain the prophylactic effects of ATG on GVHD without compromising the survival of UCBT recipients may be reasonable.

Impacts of thymoglobulin in patients with acute leukemia in remission undergoing allogeneic HSCT from different donors

Antithymocyte globulin (ATG) is widely used to reduce acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD). To clarify the different impacts of ATG for conditioning across different donor types, we retrospectively analyzed patients with acute leukemia (n = 6617) who underwent hematopoietic stem cell transplantation between 2008 and 2015 with ATG (n = 279) or without ATG (n = 6338). Because thymoglobulin is the only ATG drug approved for GVHD prophylaxis in Japan since September 2008, we included thymoglobulin alone in the present analysis. The survivors' median follow-up time was 1081 days. Patients were categorized into 5 groups: cord blood (CB; n = 1915), matched related donor (n = 1772), 1-antigen mismatched related donor (1-MMRD; n = 225), matched unrelated donor (MUD; n = 1742), and 1-allele mismatched unrelated donor (1-MMUD; n = 963). In multivariate analysis, ATG decreased overall survival (hazard ratio [HR], 1.403; P = .054) and GVHD-free/relapse-free survival (GRFS) (HR, 1.458; P = .053) in association with increased nonrelapse mortality (NRM) (HR, 1.608; P =03) with CB, whereas it improved GRFS (HR, 0.515; P < .01) and decreased grades II to IV aGVHD (HR, 0.576; P < .01), extensive cGVHD (HR, 0.460; P = .02), and NRM (HR, 0.545; P = .03) with 1-MMUD. ATG did not impact survival with 1-MMRD and MUD. The use of ATG in conditioning is beneficial due to the reduction in acute/chronic GVHD without increasing NRM or disease relapse only in 1-MMUD transplantation. On the other hand, ATG is not recommended for CB transplantation.

Incidence and Risk Factors for Acute and Chronic Kidney Injury after Adult Cord Blood Transplantation

Although cord blood transplantation (CBT) extends allograft access, patient comorbidities, chemoradiation, and nephrotoxic medications all contribute to acute kidney injury (AKI) risk. We analyzed AKI in adult myeloablative CBT recipients who underwent transplantation from 2006 to 2017 for hematologic malignancies using cyclosporine A (CSA)/mycophenolate mofetil immunosuppression. Maximum grades of AKI were calculated using Kidney Disease: Improving Global Outcomes (grade 1, 1.5 to <2-fold; grade 2, 2 to <3-fold; or grade 3, ≥3-fold over baseline) definitions. In total, 153 patients (median 51 years [range, 23-65], 114/153 [75%] acute leukemia, 27/153 [18%] African, 88/153 [58%] cytomegalovirus seropositive, median age-adjusted hematopoietic cell comorbidity index 3 [range, 0-9], median pretransplant albumin 4.0 g/dL [range, 2.6-5.2]) underwent transplantation. The day 100 cumulative incidence of grade 1-3 AKI was 83% (95% confidence interval [CI], 77%-89%) (predominantly grade 2, median onset 40 days, range 0 to 96), and grade 2-3 AKI incidence was 54% (95% CI, 46%-62%) (median onset 43 days, range 0 to 96). Mean CSA level preceding AKI onset was high (360 ng/mL, target range 300-350). In multivariate analysis, African ancestry, addition of haploidentical CD34⁺ cells, low day -7 albumin, critical illness/intensive care admission, and nephrotoxic drug exposure (predominantly CSA and/or foscarnet) were associated with AKI. In a day 100 landmark analysis, 6% of patients with no prior AKI had chronic kidney disease (CKD) at 2 years versus 43% with prior grade 1 and 38% with prior grade 2-3 AKI (overall P= .02). Adult CBT recipients are at significant AKI risk, and AKI is associated with increased risk of CKD. Prevention strategies, early recognition, and prompt intervention are critical to mitigate kidney injury.

Immune reconstitution following hematopoietic stem cell transplantation using different stem cell sources

Introduction: Adequate immune reconstitution post-HSCT is crucial for the success of transplantation, and can be affected by both patient- and transplant-related factors. Areas covered: A systematic literature search in PubMed, Scopus, and abstracts of international congresses is performed to investigate immune recovery posttransplant. In this review, we discuss the pattern of immune recovery in the post-transplant period focusing on the impact of stem cell source (bone marrow, peripheral blood stem cells, and cord blood) on immune recovery and HSCT outcome. We examine the impact of serotherapy on immune reconstitution and the need to tailor dosing of serotherapy agents when using different stem cell sources. We discuss new techniques being used particularly with cord blood and haploidentical grafts to improve immune recovery in each scenario. Expert opinion: Cord blood T cells provide a unique CD4+ biased immune reconstitution. Initial studies using targeted serotherapy with cord grafts showed improved immune recovery with limited alloreactivity. Two competing haploidentical approaches have developed in recent years including TCRαβ/CD19 depleted grafts and post-cyclophosphamide haplo-HSCT. Both approaches have comparable survival rates with limited alloreactivity. However, delayed immune reconstitution is still an ongoing problem and could be improved by modified donor lymphocyte infusions from the same haploidentical donor.

Intrabone transplant provides full stemness of cord blood stem cells with fast hematopoietic recovery and low GVHD rate: results from a prospective study

Umbilical Cord Blood (UCB) represents a valid option for patients with hematopoietic malignancies lacking an HLA matched donor. To overcome the limitation of the low stem cell dose of UCB, the intrabone (IB) route has been proposed. We report the results of a prospective study on a poor-prognosis cohort of 23 patients receiving intrabone single UCB transplant (Clinicaltrials.gov NCT00886522). Cumulative incidence of hematological recovery at day 90 was 82 ± 9% (ANC > 0.5 × 10⁹/L) and 70 ± 10% (platelet > 50 × 10⁹/L) and correlated with CD34 + cells in the graft. NRM was 20 ±  9%. No severe aGVHD and only one extensive cGVHD occurred, with fast immune reconstitution. To test the hypothesis that the direct IB injection could affect the expression of stem cells regulatory pathways, CD34 + cells from BM aspirates at day + 10, + 20, + 30, processed in hypoxic conditions mimicking the BM-microenvironment (7%pO₂), were studied for the expression of c-Mpl, Notch1 and CXCR4. We found that the expression of c-Mpl in CD34 + cells at day + 10 significantly correlated with hematological recovery. In conclusion, IB-UCB transplant success is associated with low incidence of GVHD and high-speed platelet recovery; intrabone route may preserve full hematopoietic stemness by direct delivery of UCB stem cells into the hypoxic HSC niche.

Joint Modeling of Immune Reconstitution Post Haploidentical Stem Cell Transplantation in Pediatric Patients With Acute Leukemia Comparing CD34+-Selected to CD3/CD19-Depleted Grafts in a Retrospective Multicenter Study

Rapid immune reconstitution (IR) following stem cell transplantation (SCT) is essential for a favorable outcome. The optimization of graft composition should not only enable a sufficient IR but also improve graft vs. leukemia/tumor effects, overcome infectious complications and, finally, improve patient survival. Especially in haploidentical SCT, the optimization of graft composition is controversial. Therefore, we analyzed the influence of graft manipulation on IR in 40 patients with acute leukemia in remission. We examined the cell recovery post haploidentical SCT in patients receiving a CD34⁺-selected or CD3/CD19-depleted graft, considering the applied conditioning regimen. We used joint model analysis for overall survival (OS) and analyzed the dynamics of age-adjusted leukocytes; lymphocytes; monocytes; CD3⁺, CD3⁺CD4⁺, and CD3⁺CD8⁺ T cells; natural killer (NK) cells; and B cells over the course of time after SCT. Lymphocytes, NK cells, and B cells expanded more rapidly after SCT with CD34⁺-selected grafts (P = 0.036, P = 0.002, and P < 0.001, respectively). Contrarily, CD3⁺CD4⁺ helper T cells recovered delayer in the CD34 selected group (P = 0.026). Furthermore, reduced intensity conditioning facilitated faster immune recovery of lymphocytes and T cells and their subsets (P < 0.001). However, the immune recovery for NK cells and B cells was comparable for patients who received reduced-intensity or full preparative regimens. Dynamics of all cell types had a significant influence on OS, which did not differ between patients receiving CD34⁺-selected and those receiving CD3/CD19-depleted grafts. In conclusion, cell reconstitution dynamics showed complex diversity with regard to the graft manufacturing procedure and conditioning regimen.

Selected biological issues affecting relapse after stem cell transplantation: role of T-cell impairment, NK cells and intrinsic tumor resistance

The graft vs. leukemia (GvL) effect as a method of preventing relapse is well described after allogeneic hematopoietic cell transplantation (HCT), but the mechanisms to this effect and how tumor sometimes develops resistance to GvL are just beginning to be understood. This article reviews and expands upon data presented at the Third International Workshop on Biology, Prevention and Treatment of Relapse after Stem Cell Transplantation held in Hamburg, Germany, in November 2016. We first discuss in detail the role that T-cell impairment early after HCT plays in relapse by looking at data from T cell-depleted approaches as well as the clear role that early T-cell recovery has shown in improving outcomes. We then review key findings regarding the role of specific KIR donor/recipient pairings that contribute to relapse prevention after HCT for several tumor types. Finally, we discuss a unique mouse model following the development of tumor resistance to GvL. Detailed molecular characterization of events marking the development of tumor resistance to the immunotherapy of GvL may help in developing future strategies to overcome immune escape.

Mycobacterial Infections in Solid Organ and Hematopoietic Stem Cell Transplantation

Mycobacterial infections are uncommon in solid organ and hematopoietic stem cell transplant recipients but carry significant morbidity and mortality. Donor screening strategies for tuberculosis should be emphasized in high-risk populations. Both tuberculosis and nontuberculous mycobacterial infections can have pulmonary and extrapulmonary manifestations of infections. Recommended treatment regimens typically involve multiple drugs with significant adverse effects and drug interactions.

Reconstitution of adaptive immunity after umbilical cord blood transplantation: impact on infectious complications

In comparison with allogeneic stem cell transplantation (alloHSCT) with other stem cell sources, umbilical cord blood transplantation (UCBT) was traditionally associated with increased risk of infections, particularly during the first 3 months after transplantation. Longitudinal studies of immune monitoring reported peculiar patterns of T- and B-cell recovery in the peripheral blood of UCB recipients during the first months post-transplantation. Overall, current data suggest delayed reconstitution of naive and memory CD4⁺ and CD8⁺ T-cell pools after UCBT. This is particularly true for adult recipients and for patients who received in vivo T-cell depleting approaches before the transplantation. Such delayed T-cell recovery may increase susceptibility of UCB recipients for developing opportunistic infections and viral reactivations. Regarding B-cell recovery, UCBT was associated with accelerated B-lymphopoiesis. Recent studies also reported evidence for faster functional memory B-cell recovery in UCB recipients. In this article, we briefly review T- and B-cell reconstitution after alloHSCT, with emphasis on peculiarities observed after UCBT. We further put these data in lines with risks of infections after UCBT.

Immune reconstitution and outcomes after conditioning with anti-thymocyte-globulin in unrelated cord blood transplantation; the good, the bad, and the ugly

Unrelated umbilical cord blood transplantation (UCBT) exhibits a low risk of graft-versus-host-disease (GvHD) and has unique potent anti-virus and anti-leukemia effects. Anti-thymocyte globulin (ATG) in the conditioning regimen for UCBT is successful in reducing graft rejection and GvHD. Nevertheless, this beneficial effect of ATG coincides with its detrimental effect on immune reconstitution. The latter directly relates to a high incidence of viral infections and leukemia relapses. ATG has been used in transplant patients for over 30 years. In recent years, the knowledge on the mechanisms of action of ATG and its implementation in the UCBT setting has increased dramatically. Important data became available showing the highly variable pharmacokinetics (PK) of ATG and its consequence on outcome measures. Here, we review the effects of ATG on immune reconstitution and subsequent outcomes after UCBT, and describe the mechanisms causing these effects. We highlight the importance of optimizing ATG exposure before and after UCBT and discuss strategies to maintain the 'good' and overcome the 'bad and ugly' effects of ATG on UCBT outcome.