Lymphocyte recovery predicts outcomes in cord blood and T cell-depleted haploidentical stem cell transplantation

Persistent Impairment in Immune Reconstitution and Worse Survival Outcomes in Allogeneic Stem Cell Transplantation Patients with Early Coronavirus Disease 2019 Infection

Patients undergoing allogenic hematopoietic stem cell transplantation (HSCT) are at an increased risk of mortality due to transplantation-related complications in the first year post-transplantation, owing in part to the profound immune dysregulation with T cell and B cell lymphopenia and functional impairment. Although several large studies have reported higher mortality rates from Coronavirus disease 2019 (COVID-19) in HSCT recipients, to date no study has focused on the impact of early COVID-19 infection on immune reconstitution post-transplantation and the correlation with transplantation outcomes. We retrospectively analyzed 61 consecutive adult patients who underwent their first allogeneic HSCT at our institution. Thirteen patients (21.3%) experienced early COVID-19 infection, with a median time to diagnosis of 100 days post-transplantation. In multivariable analysis, patients with early COVID-19 infection had significantly worse overall survival (adjusted hazard ratio [aHR], 4.06; 95% confidence interval [CI], 1.26 to 13.05; P = .019) and progression-free survival (aHR, 6.68; 95% CI, 2.11 to 21.11; P = .001). This was attributed mainly to higher nonrelapse mortality (NRM) among early COVID-19 patients (P = .042). Allogeneic HSCT recipients with early COVID-19 infection had significant delays in absolute lymphocyte count (95% CI, -703.69 to -56.79; P = .021), CD3+CD4+ cell (95% CI, -105.35 to -11.59; P = .042), CD3+CD8+ cell (95% CI, -324.55 to -57.13; P = .038), and CD3-CD56+ cell (95% CI, -193.51 to -47.31; P = .014) recovery compared to those without early COVID-19 infection. Our findings suggest that patients with early COVID-19 infection after allogeneic HSCT have higher NRM and worse survival, at least in part due to impaired immune reconstitution post-transplantation.

"Incidence and significance of donor-specific antibodies in haploidentical stem cell transplantation"

PGF is a devastating complication after allogeneic transplant. We retrospectively analyzed our haploidentical transplant registry to report the incidence and impact of DSA and anti-HLA on engraftment. 107 patients were identified. Median recipient-age of 22, median donor-age of 31. Sixty-two patients had AML (58%), 29 had ALL (27%), 16 (15%) had other malignancies. Sixty-one recipients (57%) had positive anti-HLA, 56 of them had the DSA results available, of these 17 patients had DSAs (15% of the total number of patients, or 28% of patients who have anti-HLA antibodies). The median cumulative MFI was 2062. Sixty-three percent of the DSA were against class-II HLA antigens. The OS, CIR, aGvHD, and cGvHD did not differ between patients with and without anti-HLA antibodies, nor between patients with and without DSA. The gender of the recipient and donor, as well as the gender mismatch between recipient and donor, were statistically associated with the incidence of anti-HLA antibodies. Three patients only developed GF (2.8%), one was primary (0.9%) and the other two secondary GF (1.9%). None of the GF cases was in patients with anti-HLA antibodies or DSA. The presence of anti-HLA or DSAs did not affect the outcomes including the incidence of PGF.

A Case of Daratumumab-Induced Significant Decrease in Donor-Specific HLA Antibodies and Remission Induction Before Haploidentical Stem Cell Transplantation in a Refractory B-ALL Patient

Objective:

To explore the method of eliminating donor-specific anti-HLA antibodies (DSA) in haploidentical stem cell transplantation (haplo-SCT).

Methods:

We present a refractory B-cell acute lymphoblastic leukemia (ALL) patient who had strongly positive DSA, but had no human leukocyte antigen–matched donor. Although CD38 expression on leukemia cells was negative, daratumumab combined with etoposide and venetoclax therapy was chosen for her.

Results:

She achieved a significant decrease in DSA levels and complete remission on the combination therapy with daratumumab. She then received a haplo-SCT from a daughter as a donor and had a successful engraftment of donor stem cell. In haplo-SCT, strongly positive DSA levels, directed against donor HLA antigens, could be significantly reduced by daratumumab therapy before transplantation and successfully bridge subsequent haplo-SCT.

Conclusion:

Although CD38 expression is negative in leukemia cells, refractory B-ALL patients may still benefit from combination therapy with daratumumab. We need further clinical observation.

Anti-PD-L1/TGF-βR fusion protein (SHR-1701) overcomes disrupted lymphocyte recovery-induced resistance to PD-1/PD-L1 inhibitors in lung cancer

Background

Second‐generation programmed cell death‐protein 1/programmed death‐ligand 1 (PD‐1/PD‐L1) inhibitors, such as bintrafusp alfa (M7824), SHR‐1701, and YM101, have been developed to simultaneously block PD‐1/PD‐L1 and transforming growth factor‐beta/transforming growth factor‐beta receptor (TGF‐β/TGF‐βR). Consequently, it is necessary to identify predictive factors of lung cancer patients who are not only resistant to PD‐1/PD‐L1 inhibitors but also sensitive to bifunctional drugs. The purpose of this study was to search for such predictors.

Methods

Multivariable Cox regression was used to study the association between the clinical outcome of treatment with PD‐1/PD‐L1 inhibitors and lymphocyte recovery after lymphopenia in lung cancer patients. Murine CMT167 lung cancer cells were engineered to express the firefly luciferase gene and implanted orthotopically in the lung of syngeneic mice. Bioluminescence imaging, flow cytometry, and immunohistochemistry were employed to determine response to immunotherapy and function of tumor‐infiltrating immune cells.

Results

For lung cancer patients treated with anti‐PD‐1/PD‐L1 antibodies, poor lymphocyte recovery was associated with a shorter progression‐free survival (PFS; P < 0.001), an accumulation of regulatory T cells (Tregs), and an elimination of CD8⁺ T cells in the peripheral blood. Levels of CD8⁺ T cells and Treg cells were also imbalanced in the tumors and peripheral immune organs of mice with poor lymphocyte recovery after chemotherapy. Moreover, these mice failed to respond to anti‐PD‐1 antibodies but remained sensitive to the anti‐PD‐L1/TGF‐βR fusion protein (SHR‐1701). Consistently, SHR‐1701 but not anti‐PD‐1 antibodies, markedly enhanced IFN‐γ production and Ki‐67 expression in peripheral CD8⁺ T cells from patients with impaired lymphocyte recovery.

Conclusions

Lung cancer patients with poor lymphocyte recovery and suffering from persistent lymphopenia after previous chemotherapy are resistant to anti‐PD‐1/PD‐L1 antibodies but might be sensitive to second‐generation agents such as SHR‐1701.

Comparison of clinical outcomes between unrelated single umbilical cord blood and "ex-vivo" T-cell depleted haploidentical transplantation in children with hematological malignancies

BACKGROUND

Over the last two decades, umbilical cord blood (UCB) and haploidentical transplantation (HaploHSCT) have emerged as alternative sources of hematopoietic stem cell for allogeneic transplantation. There are few retrospective studies and no prospective studies comparing both types of alternative transplantation in pediatric patients.

RESULTS

We analyzed the data of 134 children with hematological malignancies who received a hematopoietic stem cell transplantation from a single umbilical cord blood (UCB) (n = 42) or an "ex-vivo" T-cell depleted transplant from a haploidentical-related donor (HaploHSCT) (n = 92) between 1996 and 2014. Hematological recovery was faster after HaploHSCT than the UCB transplant group (median times to neutrophil and platelet recovery: 13 vs. 16 days, 10 vs. 57 days, respectively) (P < 0.001). The HaploHSCT group had a significantly early immune reconstitution based on NK and CD8 + T cells compared with the UCB group. However, after the first year post-transplantation, HaploHSCT had a lower number of CD4 + T and B lymphocytes compared with the UCB transplant recipients. The cumulative incidence of TRM was 29±8% in the HaploHSCT group versus 40±5% in the UCB group. Relapse incidence was 21±7% in the HaploHSCT group and 19±8% in the UCB group. Probability of DFS was 58±8% in the HaploHSCT group versus 40±9% in the UCB group (P = 0.051).

CONCLUSIONS

TCD haploidentical transplant is associated with advantages in terms of engraftment and early immune reconstitution kinetics. TCD haploidentical transplant was associated with lower incidence of infectious and non-infectious complications, especially in the early phases of the transplant compared with UCB transplant recipients. However, there are no advantages in transplant outcomes compared with UCB transplant.

Comparison of haploidentical and umbilical cord blood transplantation after myeloablative conditioning

Three-year survival is similar after PTCy haplo- and UCB transplant.

Lower relapse but higher nonrelapse mortality in ≤5/8 matched UCB as compared with haplo- and 6-8/8 UCB transplant.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) has emerged as an important treatment modality. Most reports comparing haplo-HSCT with posttransplant cyclophosphamide (PTCy) and other donor sources have focused on outcomes in older adults treated with reduced intensity conditioning. Therefore, in the current study, we evaluated outcomes in patients with hematological malignancy treated with myeloablative conditioning prior to haplo- (n = 375) or umbilical cord blood (UCB; n = 333) HSCT. All haplo recipients received a 4 of 8 HLA-matched graft, whereas recipients of UCB were matched at 6-8/8 (n = 145) or ≤5/8 (n = 188) HLA antigens. Recipients of 6-8/8 UCB transplants were younger (14 years vs 21 and 29 years) and more likely to have lower comorbidity scores compared with recipients of ≤5/8 UCB and haplo-HSCT (81% vs 69% and 63%, respectively). UCB recipients were more likely to have acute lymphoblastic leukemia and transplanted in second complete remission (CR), whereas haplo-HSCT recipients were more likely to have acute myeloid leukemia in the first CR. Other characteristics, including cytogenetic risk, were similar. Survival at 3 years was similar for the donor sources (66% haplo- and 61% after ≤5/8 and 58% after 6-8/8 UCB). Notably, relapse at 3 years was lower in recipients of ≤5/8 UCB (21%, P = .03) compared with haplo- (36%) and 6-8/8 UCB (30%). However, nonrelapse mortality was higher in ≤5/8 UCB (21%) compared with other groups (P < .0001). These data suggest that haplo-HSCT with PTCy after myeloablative conditioning provides an overall survival outcome comparable to that after UCB regardless HLA match group.

Outcomes after Haploidentical Stem Cell Transplantation with Post-Transplantation Cyclophosphamide in Patients with Primary Immunodeficiency Diseases

Allogeneic hematopoietic stem cell transplantation (HCT) can cure primary immunodeficiency diseases (PID). When a HLA-matched donor is not available, a haploidentical family donor may be considered. The use of T cell-replete haploidentical HCT with post-transplantation cyclophosphamide (haplo-PTCy) in children with PID has been reported in few case series. A donor is usually readily available, and haplo-PTCy can be used in urgent cases. We studied the outcomes of 73 patients with PID who underwent haplo-PTCy, including 55 patients who did so as a first transplantation and 18 who did so as a salvage transplantation after graft failure of previous HCT. The median patient age was 1.6 years. Most of the children were male (n = 54) and had active infection at the time of transplantation (n = 50); 10 children had severe organ damage. The diagnosis was severe combined immunodeficiency (SCID) in 34 patients and non-SCID in 39 (Wiskott-Aldrich syndrome; n = 14; chronic granulomatous disease, n = 10; other PID, n = 15). The median duration of follow-up of survivors was 2 years. The cumulative incidence of neutrophil recovery was 88% in the SCID group and 84% in non-SCID group and was 81% for first transplantations and 83% after a salvage graft. At 100 days, the cumulative incidence of acute GVHD grade II-IV and III-IV was 33% and 14%, respectively. The majority of patients reached 200/μL CD4⁺ and 1000/μL CD3⁺ cell counts between 3 and 6 months. The estimated 2-year overall survival was 66%; it was 64% for SCID patients and 65% for non-SCID patients and 63% for first HCT and 77% for salvage transplantations. Twenty-five patients died, most of them due to infection early after transplantation (before 100 days). In conclusion, haplo-PTCy is a feasible procedure, can cure two-thirds of children with PID, and can be used as rescue treatment for previous graft failure. © 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Innate Immune Responses in the Outcome of Haploidentical Hematopoietic Stem Cell Transplantation to Cure Hematologic Malignancies

In the context of allogeneic transplant platforms, human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) represents one of the latest and most promising curative strategies for patients affected by high-risk hematologic malignancies. Indeed, this platform ensures a suitable stem cell source immediately available for virtually any patents in need. Moreover, the establishment in recipients of a state of immunologic tolerance toward grafted hematopoietic stem cells (HSCs) remarkably improves the clinical outcome of this transplant procedure in terms of overall and disease free survival. However, the HLA-mismatch between donors and recipients has not been yet fully exploited in order to optimize the Graft vs. Leukemia effect. Furthermore, the efficacy of haplo-HSCT is currently hampered by several life-threatening side effects including the onset of Graft vs. Host Disease (GvHD) and the occurrence of opportunistic viral infections. In this context, the quality and the kinetic of the immune cell reconstitution (IR) certainly play a major role and several experimental efforts have been greatly endorsed to better understand and accelerate the post-transplant recovery of a fully competent immune system in haplo-HSCT. In particular, the IR of innate immune system is receiving a growing interest, as it recovers much earlier than T and B cells and it is able to rapidly exert protective effects against both tumor relapses, GvHD and the onset of life-threatening opportunistic infections. Herein, we review our current knowledge in regard to the kinetic and clinical impact of Natural Killer (NK), γδ and Innate lymphoid cells (ILCs) IRs in both allogeneic and haplo-HSCT. The present paper also provides an overview of those new therapeutic strategies currently being implemented to boost the alloreactivity of the above-mentioned innate immune effectors in order to ameliorate the prognosis of patients affected by hematologic malignancies and undergone transplant procedures.

Immune reconstitution after T-cell replete HLA-haploidentical transplantation

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

The European Society for Blood and Marrow Transplantation (EBMT) consensus recommendations for donor selection in haploidentical hematopoietic cell transplantation

The number of HLA-haploidentical hematopoietic cell transplants continues to increase worldwide due to recent improvements in outcomes, allowing more patients with hematological malignancies and non-malignant disorders to benefit from this procedure and have a chance to cure their disease. Despite these encouraging results, questions remain as multiple donors are usually available for transplantation, and choosing the best HLA-haploidentical donor for transplantation remains a challenge. Several approaches to haploidentical transplantation have been developed over time and, based on the graft received, can be grouped as follows: T-cell depleted haploidentical transplants, either complete or partial, or with T-cell replete grafts, performed with post-transplant cyclophosphamide-based graft-versus-host disease (GVHD) prophylaxis, or G-CSF-primed bone marrow graft and enhanced GVHD prophylaxis. Carefully selecting the donor can help optimize transplant outcomes for recipients of haploidentical donor transplants. Variables usually considered in the donor selection include presence of donor-specific antibodies in the recipient, donor age, donor/recipient gender and ABO combinations, and immunogenic variables, such as natural killer cell alloreactivity or KIR haplotype. Here we provide a comprehensive review of available evidence for selecting haploidentical donors for transplantation, and summarize the recommendations from the European Society for Blood and Marrow Transplantation (EBMT) on donor selection for different transplant platforms.

Single Antigen-Mismatched Unrelated Hematopoietic Stem Cell Transplantation Using High-Dose Post-Transplantation Cyclophosphamide Is a Suitable Alternative for Patients Lacking HLA-Matched Donors

The optimal prophylaxis regimen for graft-versus-host disease (GVHD) in the setting of mismatched unrelated donor (MMUD) allogeneic hematopoietic stem cell transplantation (alloHSCT) is not defined. The use of high-dose post-transplant cyclophosphamide (PTCy) in haploidentical transplantation has proven feasible and effective in overcoming the negative impact of HLA disparity on survival. We hypothesized that PTCy could also be effective in the setting of MMUD transplantation. We retrospectively analyzed 86 consecutive adult recipients of alloHSCT in our institution, comparing 2 contemporaneous groups: PTCy MMUD (n = 26) versus matched unrelated donor (MUD) (n = 60). Graft source was primarily peripheral blood (92%). All PTCy MMUD were HLA 7/8 (differences in HLA class I loci in 92% of patients) and received PTCy plus tacrolimus ± mofetil mycophenolate as GVHD prophylaxis. No differences were observed between PTCy MMUD and MUD in the 100-day cumulative incidence of acute GVHD grades II to IV (31% versus 22%, respectively; P = .59) and III to IV (8% versus 10%, P = .67). There was a trend for a lower incidence of moderate to severe chronic GVHD at 1 year after PTCy MMUD in comparison with MUD (22% versus 41%, P = .098). No differences between PTCy MMUD and MUD were found regarding nonrelapse mortality (25% versus 18%, P = .52) or relapse rate (11% versus 19%, P = .18). Progression-free survival and overall survival at 2 years were similar in both cohorts (67% versus 54% [HR, .84; 95% CI, .38 to 1.88; P = .68] and 72% versus 57% [HR, .71; 95% CI, .31 to 1.67; P = .44], respectively). The 2-year cumulative incidence of survival free of moderate to severe chronic GVHD and relapse tended to be higher in the PTCy MMUD group (47% versus 24%; HR, .60; 95% CI, .31 to 1.14; P = .12). We conclude that HLA 7/8 MMUD transplantation using PTCy plus tacrolimus is a suitable alternative for those patients who lack a MUD.

The European Society for Blood and Marrow Transplantation (EBMT) Consensus Guidelines for the Detection and Treatment of Donor-specific Anti-HLA Antibodies (DSA) in Haploidentical Hematopoietic Cell Transplantation

Haploidentical donors are now increasingly considered for transplantation in the absence of HLA-matched donors or when an urgent transplant is needed. Donor-specific anti-HLA antibodies (DSA) have been recently recognized as an important barrier against successful engraftment of donor cells, which can affect transplant survival. DSA appear more prevalent in this type of transplant due to higher likelihood of alloimmunization of multiparous females against offspring's HLA antigens, and the degree of mismatch. Here we summarize the evidence for the role of DSA in the development of primary graft failure in haploidentical transplantation and provide consensus recommendations from the European Society for Blood and Marrow Transplant Group on testing, monitoring, and treatment of patients with DSA receiving haploidentical hematopoietic progenitor cell transplantation.

NK cell therapy after hematopoietic stem cell transplantation: can we improve anti-tumor effect?

After decades since the discovery of natural killer (NK) cells as potential effector cells fighting malignantly transformed and virally infected cells, little progress has been made in their clinical application. This yet unrealized therapeutic effect is presumably, at least in part, due to low numbers of functional NK cells that could be obtained from the peripheral blood relative to tumor burden. Our group hypothesized that a relatively small NK cell number to targeted malignant cells is the cause of a lack of clinical effect. We pursued obtaining large numbers of NK cells via ex vivo expansion using feeder cells that express membrane-bound IL-21. Early clinical studies demonstrate safety of administration of ex vivo expanded NK cells after transplantation using this method and suggest a therapeutic benefit in terms on decreasing relapse rate and possible control of viral infections post-transplant can be achieved. Successful application of NK cells after hematopoietic stem cell transplantation opens the possibility to effectively enhance the anti-tumor effect and decrease relapse rate post-transplant. Moreover, high doses of NK cells could prove more efficacious in enhancing anti-tumor effects, not only in hematological malignancies, with our without transplantation, but also in solid tumor oncology.

T Cell Depletion as an Alternative Approach for Patients 55 Years or Older Undergoing Allogeneic Stem Cell Transplantation as Curative Therapy for Hematologic Malignancies

T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (HSCT) is curative treatment for hematologic malignancies in adults, shown to reduce graft-versus-host disease (GVHD) without increased relapse. We retrospectively reviewed a single-center, 11-year experience of 214 patients aged ≥ 55 years to determine tolerability and efficacy in the older adult. Most patients (70%) had myeloid diseases, and most acute leukemias were in remission. Median age was 61 years, with related and unrelated donors ≥8/10 HLA matched. Hematopoietic cell transplantation-specific comorbidity index scores were intermediate and high for 84%. Conditioning regimens were all myeloablative. Grafts were peripheral blood stem cells (97%) containing CD3 dose ≤103-4/kg body weight, without pharmacologic GVHD prophylaxis. With median follow-up of 70 months among survivors, Kaplan-Meier estimates of overall and relapse-free survival were 44% and 41%, respectively (4 years). Cumulative incidence of nonrelapse mortality at day +100 was only 10%. Incidence of GVHD for acute (grades II to IV) was 9% at day +100 and for chronic was 7% at 2 and 4 years (8 extensive, 1 overlap). Median Karnofsky performance status for patients > 2 years post-transplant was 90%. As 1 of the largest reports for patients ≥2 aged ≥55 years receiving TCD HSCTs, it demonstrates curative therapy with minimal GVHD, similar to that observed in a younger population.

A review of infectious complications after haploidentical hematopoietic stem cell transplantations

BACKGROUND

Allogeneic hematopoietic stem cell transplantation from haploidentical donor is a feasible option for patients with hematological diseases who lack a suitable HLA-matched donor, but viral and fungal infections are still the most common causes of morbidity and mortality in haploidentical transplantation setting because of delayed immune reconstitution, increased risk of graft vs host disease (GvHD) or systemic steroid use. Therefore, this review will focus on the infectious complications after haploidentical hematopoietic stem cell transplantation (HSCT).

MATERIALS AND METHODS

Electronic publications were searched until February 2017 throughout databases, including Pubmed, Cochrane, and Embase. The following keywords were used 'haploidentical transplantation', 'infection', 'T cell replete', and 'T cell deplete'.

RESULTS

An increased incidence of bacterial, fungal, or viral infections is detected in haplo-HSCT compared to related, unrelated, or cord blood transplantations. Neutropenia and use of systemic steroid for GvHD and delayed immune reconstitution are important risk factors for infection after haplo-HSCT.

CONCLUSION

A shift towards T cell repletes haplo-HSCT with post-transplant cyclophosphamide (CY) for GvHD has been emerged in recent years, in which the incidence of viral and fungal infections is detected to be lower. Prophylaxis and pre-emptive treatment strategies should be applied according to patient status.

Donor Specific Anti-HLA Antibody and Risk of Graft Failure in Haploidentical Stem Cell Transplantation

Outcomes of allogeneic hematopoietic stem cell transplantation (AHSCT) using HLA-half matched related donors (haploidentical) have recently improved due to better control of alloreactive reactions in both graft-versus-host and host-versus-graft directions. The recognition of the role of humoral rejection in the development of primary graft failure in this setting has broadened our understanding about causes of engraftment failure in these patients, helped us better select donors for patients in need of AHSCT, and developed rational therapeutic measures for HLA sensitized patients to prevent this unfortunate event, which is usually associated with a very high mortality rate. With these recent advances the rate of graft failure in haploidentical transplantation has decreased to less than 5%.

Optimal Threshold and Time of Absolute Lymphocyte Count Assessment for Outcome Prediction after Bone Marrow Transplantation

The recovery pace of absolute lymphocyte count (ALC) is prognostic after hematopoietic stem cell transplantation. Previous studies have evaluated a wide range of ALC cutoffs and time points for predicting outcomes. We aimed to determine the optimal ALC value for outcome prediction after bone marrow transplantation (BMT). A total of 518 patients who underwent BMT for acute leukemia or myelodysplastic syndrome between 1999 and 2010 were divided into a training set and a test set to assess the prognostic value of ALC on days 30, 60, 90, 120, 180, as well as the first post-transplantation day of an ALC of 100, 200, 300, 400, 500, and 1000/μL. In the training set, the best predictor of overall survival (OS), relapse-free survival (RFS), and nonrelapse mortality (NRM) was ALC on day 60. In the entire patient cohort, multivariable analyses demonstrated significantly better OS, RFS, and NRM and lower incidence of graft-versus-host disease (GVHD) in patients with an ALC >300/μL on day 60 post-BMT, both including and excluding patients who developed GVHD before day 60. Among the patient-, disease-, and transplant-related factors assessed, only busulfan-based conditioning was significantly associated with higher ALC values on day 60 in both cohorts. The optimal ALC cutoff for predicting outcomes after BMT is 300/μL on day 60 post-transplantation.

Importance of early absolute lymphocyte count after allogeneic stem cell transplantation: a retrospective study

INTRODUCTION

Early lymphocyte recovery after allogeneic hematopoietic stem cell transplantation (HSCT) is related to the prevention of serious infections and the clearing of residual tumor cells.

METHODS

We analyzed the absolute lymphocyte count at 20 (D+20) and 30 (D+30) days after HSCT in 100 patients with malignant hematologic diseases and correlated with the risk of transplant-related mortality, overall survival (OS), disease-free survival (DFS), nonrelapsed mortality (NRM), and risk of infection.

RESULTS

Patients presenting with lymphocyte counts of <300 × 103/μL on D+30 have a 3.76 times greater risk of death in <100 days. Over a medium follow-up of 20 months OS, DFS, and NRM were similar between the groups.

CONCLUSION

In our group of patients delayed lymphocyte recovery after HSCT was a predictor of early death post-HSCT.

Haploidentical Hematopoietic Stem Cell Transplantation as a Platform for Post-Transplantation Cellular Therapy

Haploidentical transplantation can extend the opportunity for transplantation to almost all patients who lack an HLA-matched donor. Advances in the field of haploidentical transplantation have led to a marked decrease in treatment-related mortality, allowing investigators to focus on developing rationale pre- and peri-remission therapies aimed at preventing disease relapse after transplantation. Because of widespread availability, low treatment-related mortality, and cost, haploidentical donors may become the preferred "alternative" donors for allogeneic hematopoietic stem cell transplantation. One of the major advantages of using a related donor is the possibility of collecting or generating additional cellular products from the same immediately available donor, which will not be rejected. Infusion of these cells in the peri-transplantation period, derived from the same immune system, is opening the possibility of markedly enhancing the antitumor effects of the graft and hastening immunologic reconstitution after transplantation.

Haploidentical stem cell transplantation augmented by CD45RA negative lymphocytes provides rapid engraftment and excellent tolerability

BACKGROUND

Haploidentical donors are being increasingly used for allogeneic hematopoietic cell transplantation (HCT). However, the requisite T-cell depletion results in a profound and often long-lasting immunocompromised state, and donor lymphocyte infusions bring a risk of graft-versus-host disease (GVHD). Naïve T-cells are believed to be among the most alloreactive T-cell subset and can be identified by CD45RA expression. Allogeneic HCT using CD45RA depletion has not been previously described for haploidentical donors.

PROCEDURE

Eight children with relapsed or refractory solid tumors were transplanted following myeloablative conditioning. Each patient received two cell products, one created by CD3 depletion and the other through CD45RA depletion.

RESULTS

Median CD34 recovery was 59.2% with CD45RA depletion, compared to 82.4% using CD3 depletion. Median CD3+ T-cell dose after CD45RA reduction was 99.2 × 10(6)  cells/kg, yet depletion of CD3+ CD45RA+ cells exceeded 4.5 log. CD45RA depletion also resulted in substantial depletion of B-cells (median 2.45 log). All eight patients engrafted within 14 days and rapidly achieved 100% donor chimerism. No acute GVHD or secondary graft failure was observed.

CONCLUSIONS

CD45RA depletion is a novel approach to haploidentical HCT that offers rapid engraftment with minimal risk of GVHD.

Immune reconstitution after haploidentical hematopoietic stem cell transplantation

Haploidentical hematopoietic stem cell transplantation (HSCT) offers the benefits of rapid and nearly universal donor availability and has been accepted worldwide as an alternative treatment for patients with hematologic malignancies who do not have a completely HLA-matched sibling or who require urgent transplantation. Unfortunately, serious infections and leukemia relapse resulting from slow immune reconstitution remain the 2 most frequent causes of mortality in patients undergoing haploidentical HSCT, particularly in those receiving extensively T cell-depleted megadose CD34(+) allografts. This review summarizes advances in immune recovery after haploidentical HSCT, focusing on the immune subsets likely to have the greatest impact on clinical outcomes. The progress made in accelerating immune reconstitution using different strategies after haploidentical HSCT is also discussed. It is our belief that a predictive immune subset-guided strategy to improve immune recovery might represent a future clinical direction.

Predicting the Clinical Outcome of Allogeneic Hematopoietic Stem Cell Transplantation: The Long and Winding Road toward Validated Immune Biomarkers

The clinical outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is strongly influenced from the potential complications arising during the delicate phase of post-transplant immune restoration. The quantitative aspects of immune-cell repopulation after HSCT and the qualitative features their functional restitution have been extensively reported. Nevertheless, measurable immune biomarkers predicting the clinical outcome of HSCT await formal validation. The aim of this review is an appraisal of most studies published so far on the predictive value of different T and NK-cell biomarkers after HSCT with emphasis on defined thresholds endorsed by multivariate analysis.

Thymic function recovery after unrelated donor cord blood or T-cell depleted HLA-haploidentical stem cell transplantation correlates with leukemia relapse

Use of alternative donors/sources of hematopoietic stem cells (HSC), such as cord blood (CB) or HLA-haploidentical (Haplo)-related donors, is associated with a significant delay in immune reconstitution after transplantation. Long-term T-cell immune reconstitution largely relies on the generation of new T cells in the recipient thymus, which can be evaluated through signal joint (sj) and beta T-cell-Receptor Excision Circles (TREC) quantification. We studied two groups of 33 and 24 children receiving, respectively, HSC Transplantation (HSCT) from an HLA-haploidentical family donor or an unrelated CB donor, for both malignant (46) and non-malignant disorders (11). Relative and absolute sj and beta-TREC values indicated comparable thymic function reconstitution at 3 and 6 months after the allograft in both groups. Compared to children with non-malignant disorders, those with hematological malignancies had significantly lower pre-transplantation TREC counts. Patients who relapsed after HSCT had a significantly less efficient thymic function both before and 6 months after HSCT with especially low beta-TREC values, this finding suggesting an impact of early intra-thymic T-cell differentiation on the occurrence of leukemia relapse.

Immune reconstitution after hematopoietic cell transplantation

PURPOSE OF REVIEW

Successful immune reconstitution is important for decreasing posthematopoietic cell transplant (post-HCT) infections, relapse, and secondary malignancy, without increasing graft-versus-host disease (GVHD). Here we review how different parts of the immune system recover, and the relationship between recovery and clinical outcomes.

RECENT FINDINGS

Innate immunity (e.g., neutrophils, natural killer cells) recovers within weeks, whereas adaptive immunity (B and T cells) recovers within months to years. This has been known for years; however, more recently, the pattern of recovery of additional immune cell subsets has been described. The role of these subsets in transplant complications like infections, GVHD and relapse is becoming increasingly recognized, as gleaned from studies of the association between subset counts or function and complications/outcomes, and from studies depleting or adoptively transferring various subsets.

SUMMARY

Lessons learned from observational studies on immune reconstitution are leading to new strategies to prevent or treat posttransplant infections. Additional knowledge is needed to develop effective strategies to prevent or treat relapse, second malignancies and GVHD.

Fifty years of melphalan use in hematopoietic stem cell transplantation

Melphalan remains the most widely used agent in preparative regimens for hematopoietic stem cell transplantation (SCT). From its initial discovery more than 50 years ago, it has been gradually incorporated in the conditioning regimens for both autologous and allogeneic transplantations because of its myeloablative properties and broad antitumor effects as a DNA alkylating agent. Melphalan remains the mainstay conditioning for multiple myeloma and lymphomas, and it has been used successfully in preparative regimens of a variety of other hematological and nonhematological malignancies. The addition of newer agents to conditioning, such as bortezomib or lenalidomide for myeloma or clofarabine for myeloid malignancies, may improve antitumor effects for transplantation, whereas melphalan in combination with alemtuzumab may represent a backbone for future cellular therapy because of reliable engraftment and low toxicity profile. This review summarizes the development and the current use of this remarkable drug in hematopoietic SCT.

Improved early outcomes using a T cell replete graft compared with T cell depleted haploidentical hematopoietic stem cell transplantation

Haploidentical stem cell transplantation (SCT) has been generally performed using a T cell depleted (TCD) graft; however, a high rate of nonrelapse mortality (NRM) has been reported, particularly in adult patients. We hypothesized that using a T cell replete (TCR) graft followed by effective posttransplantation immunosuppressive therapy would reduce NRM and improve outcomes. We analyzed 65 consecutive adult patients with hematologic malignancies who received TCR (N = 32) or TCD (N = 33) haploidentical transplants. All patients received a preparative regimen consisting of melphalan, fludarabine, and thiotepa. The TCR group received posttransplantation treatment with cyclophosphamide (Cy), tacrolimus (Tac), and mycophenolate mofetil (MMF). Patients with TCD received antithymocyte globulin followed by infusion of CD34+ selected cells with no posttransplantation immunosuppression. The majority of patients in each group had active disease at the time of transplantation. Outcomes are reported for the TCR and TCD recipients, respectively. Engraftment was achieved in 94% versus 81% (P = NS). NRM at 1 year was 16% versus 42% (P = .02). Actuarial overall survival (OS) and progression-free survival (PFS) rates at 1 year posttransplantation were 64% versus 30% (P = .02) and 50% versus 21% (P = .02). The cumulative incidence of grade II-IV acute graft-versus-host disease (aGVHD) was 20% versus 11% (P = .20), and chronic GVHD (cGVHD) 7% versus 18% (P = .03). Improved reconstitution of T cell subsets and a lower rate of infection were observed in the TCR group. These results indicate that a TCR graft followed by effective control of GVHD posttransplantation may lower NRM and improve survival after haploidentical SCT.

Rapid thymic reconstitution following bone marrow transplantation in neonatal mice is VEGF-dependent

Age-related differences in thymic function influence the rapidity of T cell reconstitution following hematopoietic stem cell transplantation (HSCT). In adults, thymic reconstitution is delayed until after marrow engraftment is established, and is significantly improved by approaches that increase marrow chimerism, such as pretransplantation irradiation. In contrast, we show that neonatal mice undergo more rapid and efficient thymic reconstitution than adults, even when bone marrow (BM) engraftment is minimal and in the absence of pretransplantation radiation. We have previously shown that the neonatal thymus produces high levels of vascular endothelial growth factor (VEGF) that drives angiogenesis locally. In this report, we show that inhibition of VEGF prior to HSCT prevents rapid thymic reconstitution in neonates, but has no effect on thymic reconstitution in adults. These data suggest that the early radiation-independent thymic reconstitution unique to the neonatal host is mediated through VEGF, and reveals a novel pathway that might be targeted to improve immune reconstitution post-HSCT.

Fludarabine, melphalan, thiotepa and anti-thymocyte globulin conditioning for unrelated cord blood transplant

Unrelated cord blood transplant (CBT) is an alternative treatment option for patients who lack a matched donor. However, the optimal type and intensity of the preparative regimen remains unclear. We evaluated the toxicity and outcomes of a conditioning regimen consisting of melphalan 140 mg/m(2) (day - 8), thiotepa 10 mg/kg (day - 7), fludarabine 160 mg/m(2) over 4 days (days - 6 to - 3) and rabbit antithymocyte globulin (ATG) 1.25 mg/kg (day - 4) and 1.75 mg/kg (day - 3) (FMT). Forty-seven patients with advanced hematologic malignancies with a median age of 23 years (30 adults and 17 children) were treated. Sixty percent of patients were in remission at transplant. Ninety-one percent of the patients engrafted neutrophils after a median of 22 days, and all but one of the patients achieving donor engraftment had hematopoietic recovery with 100% cord blood-derived cells. Grade 3 gastrointestinal toxicity was the major non-hematopoietic toxicity, occurring in 32% of patients. Cumulative incidence of day-100 grade II-IV acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease (cGVHD) was 53% and 34%, respectively, and non-relapse mortality at day 100 and 2 years was 11% and 40%. Two-year disease-free and overall survival rates were 31% and 44%, respectively. These results suggest that FMT is a feasible conditioning regimen for patients undergoing CBT.

Infectious complications in cord blood and T-cell depleted haploidentical stem cell transplantation

Infections due to post transplant immune deficiency is a major problem following allogeneic stem cell transplantation, particularly in patients receiving cord blood or T-cell depleted haploidentical transplants. We evaluated the incidence and type of infectious complications that occurred in these two types of transplant for 65 patients, 37 cord blood and 28 haploidentical, who received the same conditioning regimen: fludarabine, melphalan and thiotepa. While incidence of infections appeared similar in both types of transplant, viral infections were more frequent than bacterial or fungal infections and were the most common cause of death in both groups. Patients in the haploidentical group were 1.7 times (95% CI: 1.1 to 2.5) more likely to have a viral infection (p=0.013). Bacterial, fungal and CMV infections still quite frequent but contributed less to mortality. Pneumonia was the most common clinical syndrome and the number one cause of death in both groups. Both pneumonia and bacteremia occurred within the first 100 days in the majority of HSCT patients while CBT patients had a bimodal distribution, with more than one third of episodes after 6 months post transplant.