Which is more important for the selection of cord blood units for haematopoietic cell transplantation: the number of CD34-positive cells or total nucleated cells?

A higher CD34 + cell dose correlates with better event-free survival after KIR-ligand mismatched cord blood transplantation for childhood acute myeloid leukemia

Although killer Ig-like receptor ligands (KIR-L) mismatch has been associated with alloreactive natural killer cell activity and potent graft-versus-leukemia (GVL) effect among adults with acute myeloid leukemia (AML), its role among children with AML receiving cord blood transplantation (CBT) has not been determined. We conducted a retrospective study using a nationwide registry of the Japanese Society for Transplantation and Cellular Therapy. Patients who were diagnosed with de novo non-M3 AML and who underwent their first CBT in remission between 2000 and 2021 at under 16 years old were included. A total of 299 patients were included; 238 patients were in the KIR-L match group, and 61 patients were in the KIR-L mismatch group. The cumulative incidence rates of neutrophil recovery, platelet engraftment, and acute/chronic graft-versus-host disease did not differ significantly between the groups. The 5-year event-free survival (EFS) rate was 69.8% in the KIR-L match group and 74.0% in the KIR-L mismatch group (p = 0.490). Stratification by CD34 + cell dose into four groups revealed a significant correlation between CD34 + cell dose and EFS in the KIR-L mismatch group (p = 0.006) but not in the KIR-L match group (p = 0.325). According to our multivariate analysis, KIR-L mismatch with a high CD34 + cell dose (≥ median dose) was identified as an independent favorable prognostic factor for EFS (hazard ratio = 0.19, p = 0.029) and for the cumulative incidence of relapse (hazard ratio = 0.09, p = 0.021). Our results suggested that higher CD34 + cell doses are crucial for achieving a potent GVL effect in the context of KIR-L-mismatched CBT.

Development of an umbilical cord blood transplantation-specific nonrelapse mortality risk assessment score

ABSTRACT

Higher rate of nonrelapse mortality (NRM) remains yet to be resolved in umbilical cord blood transplantation (UCBT). Considering that UCBT has some unique features compared with allogeneic hematopoietic cell transplantation from other graft sources, a UCBT-specific NRM risk assessment system is required. Thus, in this study, we sought to develop a UCBT-specific NRM Risk Assessment (CoBRA) score. Using a nationwide registry database, we retrospectively analyzed 4437 recipients who had received their first single-unit UCBT. Using the backward elimination method, we constructed the CoBRA score in a training cohort (n = 2687), which consisted of recipients age ≥55 years (score 2), hematopoietic cell transplantation-specific comorbidity index ≥3 (score 2), male recipient, graft-versus-host disease prophylaxis other than tacrolimus in combination with methotrexate, performance status (PS) 2 to 4, HLA allele mismatch ≥ 2, refined Disease Risk Index high risk, myeloablative conditioning, and CD34+ cell doses < 0.82 × 105/kg (score 1 in each). The recipients were categorized into 3 groups: low (0-4 points), intermediate (5-7 points), and high (8-11 points) groups according to the CoBRA score. In the validation cohort (n = 1750), the cumulative incidence of NRM at 2 years was 14.9%, 25.5%, and 47.1% (P < .001), and 2-year overall survival (OS) was 74.2%, 52.7%, and 26.3% (P < .001) in the low, intermediate, and high groups, respectively. In summary, the CoBRA score could predict the NRM risk as well as OS after UCBT. Further external validation will be needed to confirm the significance of the CoBRA score.

Cord blood transplantation for adult mature lymphoid neoplasms in Europe and Japan

ABSTRACT

To clarify the different characteristics and prognostic factors of cord blood transplantation (CBT) in adult patients with lymphoid neoplasms in Europe and Japan, we conducted a collaborative study. Patients aged 18-75 years receiving their first CBT (Europe: single CBT, n = 192; double CBT, n = 304; Japan: single CBT, n = 1150) in 2000-2017 were analyzed. Fewer patients with Hodgkin lymphoma (Europe vs Japan, 26% vs 5%), and older patients (≥50 years) (39% vs 59%) with a higher refined disease risk index (rDRI) (high-very high: 49% vs 14%) were included in the Japanese registry. High-very high rDRI was associated with inferior overall survival (OS) (vs low rDRI, Europe: hazard ratio [HR], 1.87; P = .001; Japan: HR, 2.34; P < .001) with higher progression/relapse risks. Total body irradiation (TBI)-containing conditioning contributed to superior OS both in Europe (vs TBI-reduced-intensity conditioning [RIC], non-TBI-RIC: HR, 1.93; P < .001; non-TBI-Myeloablative conditioning [MAC]: HR, 1.90; P = .003) and Japan (non-TBI-RIC: HR, 1.71; P < .001; non-TBI-MAC: HR 1.50, P = .007). The impact of HLA mismatches (≥2) on OS differed (Europe: HR, 1.52; P = .007; Japan: HR, 1.18; P = .107). CBT for lymphoid neoplasms, especially in those with high rDRI showed poor outcomes despite all the different characteristics in both registries. TBI should be considered in conditioning regimens to improve these outcomes. The different impacts of HLA mismatches call attention to the fundamental differences among these populations.

Selection of Cord Blood Unit by CD34+ Cell and GM-CFU Numbers and Allele-Level HLA Matching in Single Cord Blood Transplantation

In Japan, only single-unit cord blood transplantations (CBTs) are typically performed, and their number has increased over the last 23 years, with ongoing improvement in results. In most cases, CBTs with multiple HLA mismatches are used, owing to a low HLA barrier, and lower engraftment rate is a problem that must be overcome. Here, as part of an effort to improve guidelines for the selection and processing of CB units for transplantation, we sought to assess the present status of CBT in Japan and to elucidate factors contributing to the favorable outcomes, focusing in particular on selection by cell components of CB unit and HLA allele matching. We conducted a nationwide study analyzing 13,443 patients who underwent first CBT between in Japan between December 1997 and December 2019 using multivariate regression analysis. Both patient- and transplantation-related variables, such as age and Hematopoietic Cell Transplantation Comorbidity Index, as well as selected CB unit characteristics, were included in the analysis. The interaction analysis elucidated that CB unit selection favoring higher counts of CD34+ cells and granulocyte macrophage colony-forming units (GM-CFU)/kg, but not of total nucleated cells, contributed to improved engraftment after transplantation. Moreover, a higher CD34+ cell dose was associated with improved overall survival (OS). Distinctive HLA allele matching was observed. A 0 or 1 HLA allele mismatch between patient and donor had favorable engraftment and carried significantly lower risks of acute GVHD and chronic GVHD but had a significantly higher leukemia relapse rate, compared with a 3-HLA allele mismatch. HLA-DRB1 mismatches were associated with reduced risk of leukemia relapse. Notably, the number of HLA allele mismatches had no incremental effect on engraftment, acute and chronic GVHD, or relapse incidence. As a result, 5-year overall survival did not differ significantly among patients receiving CB units with 0 to 7 HLA allele mismatches. The main points of CB unit selection are as follows. First, selection according to a higher number of CD34+ cells/kg and then of CFU-GM/kg is recommended to obtain favorable engraftment. A unit with .5 × 105 CD34+ cells/kg is minimally acceptable. For units with a CD34+ cell dose of .5 to 1.0 × 105 cells/kg, applying the parameter of ≥20 to 50 × 103 GM-CFU/kg (66.5% of transplanted CB units in this cohort) is associated with a neutrophil engraftment rate of approximately 90%. A unit with ≥1.0 × 105 CD34+ cells/kg can achieve a ≥90% mean neutrophil engraftment rate. Subsequently, HLA allele matching of HLA-A, -B, -C, and -DRB1 at the 2-field level should be searched for units with 0 or 1 HLA allele mismatch in the host-versus-graft direction for favorable engraftment. Units with 2 to 6 HLA allele mismatches are acceptable in patients age ≥15 years and units with 2 to 4 HLA allele mismatches are acceptable in patients age ≤14 years. Units with HLA-DRB1 and/or -B allele mismatch(es) might not be preferable owing to an increased GVHD risk. Our analysis demonstrates that single-unit CBT with the selection of adequate CD34+/kg and GM-CFU/kg and HLA allele matching showed favorable outcomes in both pediatric and adult patients.

Forging international collaboration and alliances to establish the largest transplant center in the north of Vietnam

Through collaboration with international experts, our institution established a highly active and successful hematopoietic stem cell transplant program, providing access to this potentially curative treatment modality for patients with a variety of benign and malignant hematological diseases. The initial development of an autologous stem cell transplant program provided our institution with the infrastructure, equipment, and expertise needed for the subsequent development of an allogeneic stem cell transplant program. Key transplant staff received training from international transplant experts at the NHLBI/NIH, the Mayo Clinic, the Johns Hopkins Hospital, and Nagoya Japan, providing them with the expertise to conduct a variety of different transplant approaches, including PBSC transplants from HLA-matched relatives, unrelated cord blood transplants, haploidentical transplants, and CD34 selected stem cell transplants. Patient characteristics were varied among all groups. The number of allogeneic and autologous transplants performed at the NIHBT has increased steadily every year since the initiation of our transplant program. By 2022, 547 transplant procedures had been performed, including 268 autologous and 279 allogeneic transplants. Allogeneic transplants were performed for both malignant and nonmalignant hematological diseases, with acute leukemia (AL) being the most common indication for allogeneic HCT. The majority of recipients undergoing allogeneic transplantation received G-CSF mobilized PBSC allografts from either HLA identical or haplo-identical relatives, with a smaller percentage of patients receiving a UCB transplant or a PBSC allograft that had been CD34+ selected. Amongst the 279 recipients of an allogeneic transplant, mortality rates within day 100 and beyond day 100 were 12.6% and 26.2% respectively. Overall survival (OS) and event-free survival at 5 years in benign and malignant subgroups were 81% and 73% vs 52% and 48% respectively. Through collaboration with international transplant experts, the National Institute of Hematology and Blood Transfusion in Hanoi has stood up the most active transplant center in the northern region of Vietnam. Patients coming from low-income financial backgrounds are now able to receive a variety of different state-of-the-art transplant approaches that are affordable and have been associated with excellent long-term outcomes.

Allogeneic hematopoietic stem cell transplantation for inherited metabolic disorders

Allogeneic hematopoietic stem cell transplantation (HSCT) has been used to treat patients with inherited metabolic disorders (IMDs) for more than 40 years. In the first two decades, various IMDs were treated by HSCT with a wide variety of donor sources and conditioning regimens selected at the institutional level. However, HSCT was not always successful due to post-transplant complications such as graft failure. In the third decade, myeloablative conditioning with targeted busulfan-based pharmacokinetic monitoring was established as an optimal conditioning regimen, and unrelated cord blood was recognized as an excellent donor source. During the fourth decade, further improvements were made to transplant procedures, including modification of the conditioning regimen, and the survival rate after HSCT markedly improved. Simultaneously, several long-term observational studies for patients after HSCT clarified its therapeutic effects on growth and development of cognitive function, fine motor skills, and activities of daily living when compared with enzyme replacement therapy. Although immune-mediated cytopenia was newly highlighted as a problematic morbidity after HSCT for IMDs, especially in younger patients who received unrelated cord blood, a recent study with rituximab added to the conditioning raised expectations that this issue can be overcome.

Ideal body weight is useful for predicting neutrophil engraftment and platelet recovery for overweight and obese recipients in single-unit cord blood transplantation

BACKGROUND

Since cord blood (CB) units are usually selected based on the cell dose /kg, overweight (25 kg/m² ≤ body mass index (BMI) < 30 kg/m²) and obese (30 kg/m² ≤ BMI) recipients tend to have difficulty in getting appropriate CB units. In general, actual body weight (ABW) is used for CB unit selection. However, ideal body weight (IBW) has been reported to be more closely correlated with successful engraftment after autologous, allogeneic bone marrow, and peripheral blood stem cell transplantation than ABW.

OBJECTIVES

We conducted this analysis to clarify the threshold of CD34⁺ cell doses based on ideal body weight (CD34^IBW) and to compare the outcomes among the groups stratified by the threshold according to actual body weight (CD34^ABW) and CD34^IBW for overweight and obese recipients in cord blood transplantation (CBT).

STUDY DESIGN

We retrospectively analyzed 650 overweight and obese recipients who received single-unit CBT. To focus on the recipients who received a low CD34⁺ cell dose /kg, those who received 1.5×10⁵ CD34⁺ cells /ABW or more were excluded. Using a cut-off of 0.8×10⁵ CD34⁺ cells/kg, we compared the outcomes in 3 groups with low CD34^ABW and low CD34^IBW (CD34^Low/Low), low CD34^ABW but high CD34^IBW (CD34^Low/High), and high CD34^ABW and high CD34^IBW (CD34^High/High).

RESULTS

Hematopoietic recoveries were significantly delayed in the CD34^Low/Low group compared with those in the CD34^Low/High group (hazard ratio (HR) 0.67 for neutrophil, P < 0.001; HR 0.72 for platelet, P = 0.014), while those were comparable in the CD34^Low/High and CD34^High/High groups (HR 1.22 for neutrophil, P = 0.16; HR 1.29 for platelet, P = 0.088). Moreover, the CD34^Low/High group demonstrated longer overall survival than the CD34^Low/Low group (HR 1.48, P = 0.011) and comparable survival to the CD34^High/High group (HR 0.93, P = 0.68).

CONCLUSIONS

This finding may address the lack of availability of CB units for some overweight and obese recipients for whom suitable donors are unavailable. Further investigations are warranted to evaluate the appropriateness of ABW and IBW.

Decision Analysis for Unrelated Bone Marrow Transplantation or Immediate Cord Blood Transplantation for Patients with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia in First Complete Remission

An HLA-matched relative is the first-choice donor for patients with Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) in first complete remission (CR1). The most promising alternative donor is thought to be an HLA-matched unrelated donor (MUD) in patients who do not have an HLA-matched related donor. Cord blood transplantation (CBT) is an alternative option. Higher rates of engraftment failure and nonrelapse mortality are significant problems, but the ready availability of cord blood can be an advantage, because patients can immediately undergo transplantation before progression. This study was conducted to identify an appropriate alternative donor in patients with Ph-negative ALL in CR1 who do not have an HLA-matched related donor (MRD). Decision analyses using a Markov model were performed to compare immediate CBT, in which CBT was performed at 1 month after the achievement of CR1, with elective unrelated bone marrow transplantation (uBMT) from an 8/8 HLA-matched unrelated donor (MUD) (8/8 uBMT) or uBMT from 7/8 MUD (7/8 uBMT), in which uBMT was performed at 4 months, in patients age 16 to 55 years with Ph-negative ALL in CR1 who did not have an MRD. We constructed a decision tree. The cycle length was set at 3 months, and analyses were performed for 19 cycles for uBMT and 20 cycles for CBT, resulting in evaluation of the 5-year life expectancy after both decisions. Transition probabilities (TPs) and utilities were estimated from prospective and retrospective Japanese studies and the registry database of Japan. Subgroup analyses were performed according to risk stratification based on WBC count and cytogenetics at diagnosis and according to age stratification, with a cutoff of 25 years. One-way sensitivity analyses for TPs and utilities were performed as well. The baseline analyses showed that 8/8 uBMT or 7/8 uBMT had superior results to CBT, with quality-adjusted life years (QALYs) of 2.86 in 8/8 uBMT, 2.84 in 7/8 uBMT, and 2.75 in CBT. One-way sensitivity analyses showed that the results of the baseline analyses were reversed if the probability of nonrelapse mortality (NRM) in CBT improved. Subgroup analyses showed similar results in younger, older, and high-risk patients. However, QALY was worse in 8/8 uBMT compared with CBT in standard-risk patients. In one-way sensitivity analyses, the probabilities of NRM in uBMT and CBT affected the baseline results in all analyses except for comparisons between 8/8 uBMT and CBT in younger and high-risk patients. In these 2 populations, the superiority of 8/8 uBMT was consistently demonstrated throughout the one-way sensitivity analyses. For patients with Ph-negative ALL in CR1 who decide to undergo transplantation from an alternative donor, elective uBMT from either an 8/8 MUD or a 7/8 MUD is expected to yield a better outcome than immediate CBT. Nonetheless, CBT is a viable option, and improvements to reduce the risk of NRM in CBT may change these results.

Combined impact of HLA-allele matching and the CD34-positive cell dose on optimal unit selection for single-unit cord blood transplantation in adults

The combined effects of HLA-allele matching at six-loci (HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1) and CD34⁺ cell dose on clinical outcomes were analyzed in 1,226 adult cases with single-unit unrelated cord blood transplantation. In the six-loci analysis, low HLA-allele matches did not significantly increase the overall mortality compared to higher matches, whereas in the five-loci analysis excluding HLA-DPB1, they caused a higher overall mortality (HR 1.42, p = .002), possibly due to the graft-versus-leukemia effect of HLA-DPB1 mismatches. A lower CD34⁺ cell dose (<.50 × 10⁵/kg) resulted in higher mortality and lower engraftment; these inferior outcomes were offset by high HLA-allele matches (7-10/10 match), while the inferior outcomes of low HLA-allele matches were improved by increasing the CD34⁺ cell dose. Consideration of the combined effects of the CD34⁺ cell dose and HLA matching may expand the options for transplantable units when HLA matching or the CD34⁺ cell dose is inadequate.

A multicenter phase II study of intrabone single-unit cord blood transplantation without antithymocyte globulin

To overcome the delayed or failed engraftment after unrelated cord blood transplantation (CBT), we conducted a multicenter phase II study of intrabone single-unit CBT without antithymocyte globulin (ATG) for adult patients with hematological malignancies (UMIN-CTR, UMIN000020997). Sixty-four patients received an intrabone injection of unwashed (n = 61) or washed (n = 3) cord blood after local anesthesia. All injection-related adverse events were mild and resolved spontaneously. Sixty-two patients were evaluable for the efficacy of intrabone CBT of serological HLA-A, -B, and -DR ≥ 4/6 matched cord blood with a median number of 2.57 × 10⁷/kg cryopreserved total nucleated cells. The probability of survival with neutrophil engraftment on day 28 was 77.4% (95% confidence interval, 67.0-85.8%), which exceeded the threshold value. The cumulative incidences of neutrophils ≥ 0.5 × 10⁹/L on day 60 was 80.6% (68.2-88.6%), with a median time to recovery of 21 days after transplantation. The cumulative incidences of platelets ≥ 20 × 10⁹/L and platelets ≥ 50 × 10⁹/L on day 100 were 75.8% (62.6-84.9%) and 72.6% (59.4-82.1%), respectively, with median time to platelets ≥ 20 × 10⁹/L and platelets ≥ 50 × 10⁹/L of 38 and 45 days after transplantation, respectively. The cumulative incidences of grade II-IV and III-IV acute graft-versus-host disease were 29.0% and 6.5%, respectively. All responded to steroid therapy, and secondary treatments were not required. The present study suggests the efficacy of intrabone single-unit CBT without ATG in terms of early engraftment and controllable acute graft-versus-host disease.

Autologous Hematopoietic Recovery after Unrelated Umbilical Cord Blood Transplantation with Myeloablative Conditioning for Acute Myelogenous Leukemia

Autologous hematopoietic recovery after allogeneic hematopoietic cell transplantation (allo-HCT) is rare in patients who receive myeloablative conditioning (MAC). Autologous hematopoietic recovery suggests graft rejection, leading to concerns about subsequent disease relapse. We herein report a rare case of a patient with acute leukemia who experienced autologous hematopoietic recovery after cord blood transplantation (CBT) with total body irradiation-based MAC. Chromosomal abnormalities were repeatedly detected without any disease relapse for eight months. The accumulation of similar cases is required to accurately assess the incidence and clinical outcomes of autologous hematopoietic recovery after CBT with MAC.

Allogeneic hematopoietic stem cell transplantation in a prior lung transplant recipient

Hematological diseases after solid organ transplant (SOT) are an emerging issue as the number of long-term SOT survivors increases. Expertise in managing patients requiring allogeneic hematopoietic stem cell transplantation (HSCT) after SOT from independent donors is needed; however, clinical reports of HSCT after SOT are limited, and the feasibility and risk are not well understood. In particular, HSCT in prior lung transplant recipients is thought to be complicated as the lung is immunologically distinct and is constantly exposed to the surrounding environment. Herein, we describe a case of successful HSCT in a patient with myelodysplastic syndromes who had previously received a lung transplant from a deceased donor for bronchiolitis obliterans syndrome. Reports about cases of HSCT after lung transplant are quite rare; thus, we discuss the mechanisms of immune tolerance through the clinical course of our case. This case suggests that HSCT after SOT can be considered a therapeutic option in cases where the transplanted organ is functionally retained and the hematological disease is in remission.

Guidelines for Cord Blood Unit Selection

Optimal cord blood (CB) unit selection is critical to maximize the likelihood of successful engraftment and survival after CB transplantation (CBT). However, unit selection can be complex because multiple characteristics must be considered including unit cell dose, donor-recipient human leukocyte antigen (HLA) match, and unit quality. This review provides evidence-based and experience-based comprehensive guidelines for CB unit selection. Topics addressed include the use of both the TNC and the CD34⁺ cell dose, as well as the CD34⁺ cell to TNC content ratio to evaluate unit progenitor cell content and engraftment potential, the acceptable TNC and CD34⁺ cell dose criteria that define an adequate single-unit graft, and the indication and acceptable cell dose criteria for double-unit grafts. The acceptable criteria for 6-loci (HLA-A, -B antigen, -DRB1 allele) and 8-allele (HLA-A, -B, -C, -DRB1) donor-recipient HLA match, the evaluation of patients with donor-specific HLA antibodies, and the multiple determinants of unit quality are also reviewed in detail. Finally, a practical step-by-step guide to CB searches and the principles that guide ultimate graft selection are outlined.

Reduced dose of MTX for GVHD prophylaxis promotes engraftment and decreases non-relapse mortality in umbilical cord blood transplantation

Although a combination of calcineurin inhibitor and methotrexate (MTX) is used for graft-versus-host disease (GVHD) prophylaxis in umbilical cord blood transplantation (CBT), optimal dose of MTX for CBT remains to be determined.We conducted a retrospective study to evaluate the safety and efficacy of standard-dose MTX (St-MTX, 15 mg/m² on day 1 and 10 mg/m² on days 3 and 6) and mini-dose MTX (Mini-MTX, 5 mg/m² on days 1, 3 and 6) for GVHD prophylaxis in patients who underwent single unit CBT against hematological malignancies.Thirty-two and 26 patients received St-MTX and Mini-MTX, respectively. Cumulative incidence of neutrophil engraftment was significantly higher in the Mini-MTX group than in the St-MTX group (88.5% vs 65.6%, P = 0.00448). Cumulative incidences of grade II to IV and grade III to IV of acute graft-versus-host disease (GVHD) were 34.4% and 6.2% in the St-MTX group, and 34.6% and 7.7% in the Mini-MTX group with no statistical significance. One-year non-relapse mortality (NRM) was significantly lower in the Mini-MTX group compared to the St-MTX group (31.2% vs 3.8%, P = 0.00938), whereas relapse rate was not different between the groups. Multivariate analysis also indicated that Mini-MTX significantly improved engraftment (HR, 0.5359; 95% CI, 0.3082 to 0.9318; P = 0.0270) and reduced NRM (HR, 0.117; 95% CI, 0.0151 to 0.9067; P = 0.040).Our study suggests that GVHD prophylaxis using Mini-MTX in CBT is feasible and associated with improvement of engraftment and reduction in NRM.

Effects of Haplotype Matching on Outcomes after Adult Single-Cord Blood Transplantation

It remains unclear whether the HLA haplotype of unrelated cord blood (UCB) should be matched to that of the patient in single UCB transplantation. Thus, using data from a Japanese registry, we analyzed the effect of haplotype matching on outcomes. Patients with hematologic diseases aged 16 years or older who had undergone their first transplant were included (N = 1347). The effects of haplotype matching and high-frequency HLA haplotype on outcomes were analyzed. Median patient age was 55 years. The cumulative incidences of neutrophil engraftment among groups with 0, 1, and 2 HLA haplotype matches were 79%, 82%, and 88%, respectively (P = .008). In a multivariate analysis, the group with 0 haplotype matches was marginally associated with worse neutrophil engraftment (P = .087) and significantly associated with platelet engraftment (P = .044) compared with the group with 1 haplotype match. Two-haplotype matches were associated with a higher risk of relapse. In the group with 1 haplotype match, the top 3 shared haplotypes were "A*24:02-B*52:01-C*12:02-DRB1*15:02" (HP-P1), "A*33:03-B*44:03-C*14:03-DRB1*13:02" (HP-P2), and "A*24:02-B*07:02-C*07:02-DRB1*01:01" (HP-P3). The presence of HP-P2 but not HP-P1 or HP-P3 was associated with a decreased risk of grades II to IV acute graft-versus-host disease (hazard ratio, .56; P = .001) but an increased risk of relapse (hazard ratio, 1.35; P = .045). HLA haplotype matching might be considered to improve engraftment. Two-haplotype matches should be avoided if the relapse risk is high. The haplotype itself may have an effect on the risk of acute graft-versus-host disease and relapse.

Impact of pretransplant donor-specific anti-HLA antibodies on cord blood transplantation on behalf of the Transplant Complications Working Group of Japan Society for Hematopoietic Cell Transplantation

Graft failure (GF) remains a major complication of cord blood transplantation (CBT). Although the presence of pretransplant, donor-specific anti-HLA antibodies (DSA) was reported to be associated with an increased risk of GF after CBT, data are still limited. Thus, we conducted a retrospective analysis of recipients of single-unit CBT with pretransplant anti-HLA antibodies using the database of Japan Society for Hematopoietic Cell Transplantation (JSHCT). Data for recipients of single-unit CBT with pretransplant anti-HLA antibodies from 2010 to 2014 were obtained. In total, 343 patients who received CBT and who had detailed information about anti-HLA antibodies were included. The median age was 51 years (range, 0-71). Regarding DSA, 25 patients had a mean fluorescence intensity (MFI) ≥ 1000 (DSA-positive group) and 318 patients had a MFI <1000 (DSA-negative group). The cumulative incidence of neutrophil engraftment at 60 days after CBT was 75.7% (95% CI, 70.6-80.1) in the DSA-negative group and 56.0% (95% CI, 34.1-73.1) in the DSA-positive group (P = 0.03). In conclusion, pretransplant DSA with a MFI ≥ 1000 was associated with an increased risk of GF in single-unit CBT.

Human Leukocyte Antigen and Red Blood Cells Impact Umbilical Cord Blood CD34+ Cell Viability after Thawing

Hematopoietic progenitor cell (HPC) transplantation is a treatment option for malignant and nonmalignant diseases. Umbilical cord blood (UCB) is an important HPC source, mainly for pediatric patients. It has been demonstrated that human leukocyte antigen (HLA) matching and cell dose are the most important features impacting clinical outcomes. However, UCB matching is performed using low resolution HLA typing and it has been demonstrated that the unnoticed mismatches negatively impact the transplant. Since we found differences in CD34+ viability after thawing of UCB units matched for two different patients (p = 0.05), we presumed a possible association between CD34+ cell viability and HLA. We performed a multivariate linear model (n = 67), comprising pre-cryopreservation variables and high resolution HLA genotypes separately. We found that pre-cryopreservation red blood cells (RBC), granulocytes, and viable CD34+ cell count significantly impacted CD34+ viability after thawing, along with HLA-B or -C (R2 = 0.95, p = 0.01; R2 = 0.56, p = 0.007, respectively). Although HLA-B*40:02 may have a negative impact on CD34+ cell viability, RBC depletion significantly improves it.

Single cord blood transplantation in Japan; expanding the possibilities of CBT

Cord blood (CB) has been an alternative stem cell source for patients with a wide variety of hematological diseases. Cord blood confers the advantages of rapid availability and higher tolerance to two HLA antigen mismatches compared with unrelated donors, and this has increased opportunities for patients who do not have suitable donors or require urgent transplantation. Although the higher rate of engraftment failure remains a serious concern after cord blood transplantation (CBT), the mechanisms underlying this risk have gradually been clarified, which has helped to improve engraftment. Recent studies of CBT and other alternatives have reported comparable outcomes. Moreover, CBT shows promise even when patients are in a non-remission status, which may reflect the potent graft-versus-leukemia effect of CB. Here we compare the most recent outcomes of CBT with those of other stem cell sources and discuss the potential of CB and several outstanding issues that require resolution.

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.