Plasticity after allogeneic hematopoietic stem cell transplantation

The postulated almost unlimited potential of transplanted hematopoietic stem cells (HSCs) to transdifferentiate into cell types that do not belong to the hematopoietic system denotes a complete paradigm shift of the hierarchical hemopoietic tree. In several studies during the last few years, donor cells have been identified in almost all recipient tissues after allogeneic HSC transplantation (HSCT), supporting the theory that any failing organ could be accessible to regenerative cell therapy. However, the putative potential ability of the stem cells to cross beyond lineage barriers has been questioned by other studies which suggest that hematopoietic cells might fuse with non-hematopoietic cells and mimic the appearance of transdifferentiation. Proof that HSCs have preserved the capacity to transdifferentiate into other cell types remains to be demonstrated. In this review, we focus mainly on clinical studies addressing plasticity in humans who underwent allogeneic HSCT. We summarize the published data on non-hematopoietic chimerism, donor cell contribution to tissue repair, the controversies related to the methods used to detect donor-derived non-hematopoietic cells and the functional impact of this phenomenon in diverse specific target tissues and organs.     

Early CD4+ T cell reconstitution as predictor of outcomes after allogeneic hematopoietic cell transplantation

Background: An association between early CD4+ T cell immune reconstitution (CD4+ IR) and survival after T-replete allogeneic hematopoietic cell transplantation (HCT) has been previously reported. Here we report validation of this relationship in a separate cohort that included recipients of ex vivo T-cell-depleted (TCD) HCT. We studied the relationship between CD4+ IR and clinical outcomes.Methods: A retrospective analysis of children/young adults receiving their first allogeneic HCT for any indication between January 2008 and December 2017 was performed. We related early CD4+ IR (defined as achieving >50 CD4+ T cells/µL on two consecutive measures within 100 days of HCT) to overall survival (OS), relapse, non-relapse mortality (NRM), event-free survival (EFS) and acute graft-versus-host disease (aGVHD). Fine and Gray competing risk models and Cox proportional hazard models were used.Results: In this analysis, 315 patients with a median age of 10.4 years (interquartile range 5.0–16.5 years) were included. The cumulative incidence of CD4+ IR at 100 days was 66.7% in the entire cohort, 54.7% in TCD (N = 208, hazard ratio [HR] 0.47, P < 0.001), 90.0% in uCB (N = 40) and 89.6% in T-replete (N = 47) HCT recipients. In multi-variate analyses, not achieving early CD4+ IR was a predictor of inferior OS (HR 2.35, 95% confidence interval [CI] 1.46–3.79, P < 0.001) and EFS (HR 1.80, 95% CI 1.20–2.69, P = 0.004) and increased NRM (HR 6.58, 95% CI 2.82–15.38, P < 0.001). No impact of CD4+ IR on relapse or aGVHD was found. Within the TCD group, similar associations were observed.Conclusion: In this HCT cohort, including recipients of TCD HCT, we confirmed that early CD4+ IR was an excellent predictor of outcomes. Finding strategies to predict or improve CD4+ IR may influence outcomes.     

Immune reconstitution after anti-thymocyte globulin-conditioned hematopoietic cell transplantation

Background aimsAnti-thymocyte globulin (ATG) is being used increasingly to prevent graft-versus-host disease (GvHD); however, its impact on immune reconstitution is relatively unknown. We (i) studied immune reconstitution after ATG-conditioned hematopoietic cell transplantation (HCT), (ii) determined the factors influencing the reconstitution, and (iii) compared it with non-ATG-conditioned HCT.MethodsImmune cell subset counts were determined at 1–24 months post-transplant in 125 HCT recipients who received ATG during conditioning. Subset counts were also determined in 46 non-ATG-conditioned patients (similarly treated).Results(i) Reconstitution after ATG-conditioned HCT was fast for innate immune cells, intermediate for B cells and CD8 T cells, and very slow for CD4 T cells and invariant natural killer T (iNKT) (iNKT) cells. (ii) Faster reconstitution after ATG-conditioned HCT was associated with a higher number of cells of the same subset transferred with the graft in the case of memory B cells, naive CD4 T cells, naive CD8 T cells, iNKT cells and myeloid dendritic cells; lower recipient age in the case of naive CD4 T cells and naive CD8 T cells; cytomegalovirus recipient seropositivity in the case of memory/effector T cells; an absence of GvHD in the case of naive B cells; lower ATG serum levels in the case of most T-cell subsets, including iNKT cells; and higher ATG levels in the case of NK cells and B cells. (iii) Compared with non-ATG-conditioned HCT, reconstitution after ATG-conditioned HCT was slower for CD4 T cells, and faster for NK cells and B cells.ConclusionsATG worsens the reconstitution of CD4 T cells but improves the reconstitution of NK and B cells.     

Rapid reconstitution of antibody responses following transplantation of purified allogeneic hematopoietic stem cells

Allogeneic hematopoietic cell transplantation has broad clinical applications extending from the treatment of malignancies to induction of immunologic tolerance. However, adaptive cellular and humoral immunity frequently remain impaired posttransplantation. Here, recovery of T-dependent and T-independent Ab responses was evaluated in mice transplanted with purified hematopoietic stem cells (HSCs) devoid of the mature immune cells believed to hasten immune recovery. Mixed and full donor chimeras were created by conditioning recipients with sublethal or lethal irradiation, respectively, across different donor/host genetic disparities. By 6 wk posttransplantation, all animals demonstrated robust T-independent Ab responses, and all mixed chimeras and recipients of MHC-matched or haploidentical HSCs with a shared MHC haplotype had T-dependent Ab responses equivalent to those of untransplanted controls. Full chimeras that received fully MHC-disparate HSCs showed delayed T-dependent Ab responses that recovered by 12 wk. This delay occurred despite early reconstitution and proper migration to germinal centers of donor-derived T(follicular helper) (T(FH)) cells. Congenic transplants into T(FH)-deficient CD4(-/-) mice revealed restoration of T-dependent Ab responses by 6 wk, leading us to conclude that MHC disparity caused delay in humoral recovery. These findings, together with our previous studies, show that, contrary to the view that depletion of graft lymphocytes results in poor posttransplant immunity, elimination of immune-suppressing graft-versus-host reactions permits superior immune reconstitution. This study also provides insight into the regeneration of T(FH) cells and humoral immunity after allogeneic HSC transplantation.     

Effect of alemtuzumab-based T-cell depletion on graft compositional change in vitro and immune reconstitution early after allogeneic stem cell transplantation

Background aimsTo reduce the risk of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (alloSCT), T-cell depletion (TCD) of grafts can be performed by the addition of alemtuzumab (ALT) “to the bag” (in vitro) before transplantation. In this prospective study, the authors analyzed the effect of in vitro incubation with 20 mg ALT on the composition of grafts prior to graft infusion. Furthermore, the authors assessed whether graft composition at the moment of infusion was predictive for T-cell reconstitution and development of GVHD early after TCD alloSCT.MethodsSixty granulocyte colony-stimulating factor-mobilized stem cell grafts were obtained from ≥9/10 HLA-matched related and unrelated donors. The composition of the grafts was analyzed by flow cytometry before and after in vitro incubation with ALT. T-cell reconstitution and incidence of severe GVHD were monitored until 12 weeks after transplantation.ResultsIn vitro incubation of grafts with 20 mg ALT resulted in an initial median depletion efficiency of T-cell receptor (TCR) α/β T cells of 96.7% (range, 63.5–99.8%), followed by subsequent depletion in vivo. Graft volumes and absolute leukocyte counts of grafts before the addition of ALT were not predictive for the efficiency of TCR α/β T-cell depletion. CD4^pos T cells were depleted more efficiently than CD8^pos T cells, and naive and regulatory T cells were depleted more efficiently than memory and effector T cells. This differential depletion of T-cell subsets was in line with their reported differential CD52 expression. In vitro depletion efficiencies and absolute numbers of (naive) TCR α/β T cells in the grafts after ALT incubation were not predictive for T-cell reconstitution or development of GVHD post- alloSCT.ConclusionsThe addition of ALT to the bag is an easy, fast and generally applicable strategy to prevent GVHD in patients receiving alloSCT after myeloablative or non-myeloablative conditioning because of the efficient differential depletion of donor-derived lymphocytes and T cells.     

Improving immune reconstitution while preventing GvHD in allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematologic malignancies and inherited disorders of the hematopoietic system. Ex vivo T-cell depletion (TCD) of the graft and post-transplantation immunosuppression efficiently prevents the development of GvHD in no- MHC-identical settings. However, the consequence of these non-specific strategies is a long-lasting immunodeficiency associated with increased incidence of disease relapse, graft rejection and reactivation of viral infections. Donor lymphocyte infusion, which is used for treating leukemic relapse after allogeneic HSCT, can result in severe GvHD. Several strategies are being optimized specifically to inactivate anti-host T cells while preserving anti-leukemic or anti-microbial immunocompetence. Based on the ex vivo or in vivo elimination of anti-host T cells, or on the modulation of their anti-host activity, these approaches, which have been explored extensively in pre-clinical studies and tested in some preliminary clinical trials, are discussed in this paper.     

G-CSF诱导移植物抗白血病效应治疗异基因造血干细胞移植后复发白血病的研究

目的观察应用G-CSF诱导移植物抗白血病效应治疗异基因造血干细胞移植后复发白血病的疗效。方法对2011年7月至2013年2月该科异基因造血干细胞移植后40例复发的白血病患者,进行输注粒细胞集落刺激因子动员后供者外周血单个核细胞治疗。其中-CR3髓系有4例,细胞混合有6例,-CR2淋巴细胞有10例,-CR2髓系有16例,髓系加速期慢性有4例。在异基因造血干细胞移植后,半年内,40例患者均复发,予G-CSF动员后,供者外周血单个核细胞输注,每次输注细胞量逐级增加,每次输注间隔4周。结果 24例患者再次缓解完全,未缓解的16例。患者输注后,6例发生急性移植物抗宿主病Ⅰ~Ⅱ度,24例发生慢性移植物抗宿主病,5例未发生并发症。结论 G-CSF诱导移植物抗白血病效应治疗后,白血病复发有较好的疗效,不良反应小,值得临床推广。     

异基因造血干细胞移植后并发自身免疫性溶血性贫血的治疗进展

异基因造血干细胞移植（HSCT）后自身免疫性溶血性贫血（AIHA）是HSCT后并不少见的并发症,其发病率约1﹪~ 6﹪,不同于一般的AIHA,HSCT后AIHA发病机制尚未完全明确,可能与HSCT后受者体内免疫失调相关。危险因素与移植患者年龄小、非恶性疾病、使用无关供者、半相合供者移植、脐血移植、去T细胞移植及移植后并发慢性移植物抗宿主病（GVHD）等有关。皮质激素作为一线治疗,疗效有限,难以持续缓解,需联合使用利妥昔单抗（RTX）、大剂量丙种球蛋白等,甚至需要联合霉酚酸酯、环磷酰胺、西罗莫司、阿伦单抗、依库丽单抗或蛋白酶体抑制剂硼替佐米等免疫抑制剂治疗,部分患者需行血浆置换,偶有行脾切除术者。移植后AIHA总死亡率常高达50﹪,总体预后差于单纯AIHA。该综述旨在总结HSCT后并发AIHA的最新治疗进展,供临床医师参考。     

Monitoring of human cytomegalovirus and virus-specific T-cell response in young patients receiving allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem-cell transplantation (HSCT) recipients, outcome of human cytomegalovirus (HCMV) infection results from balance between viral load/replication and pathogen-specific T-cell response. Using a cut-off of 30,000 HCMV DNA copies/ml blood for pre-emptive therapy and cut-offs of 1 and 3 virus-specific CD4(+) and CD8(+) T cells/μl blood for T-cell protection, we conducted in 131 young patients a prospective 3-year study aimed at verifying whether achievement of such immunological cut-offs protects from HCMV disease. In the first three months after transplantation, 55/89 (62%) HCMV-seropositive patients had infection and 36/55 (65%) were treated pre-emptively, whereas only 7/42 (17%) HCMV-seronegative patients developed infection and 3/7 (43%) were treated. After 12 months, 76 HCMV-seropositive and 9 HCMV-seronegative patients (cumulative incidence: 90% and 21%, respectively) displayed protective HCMV-specific immunity. Eighty of these 85 (95%) patients showed spontaneous control of HCMV infection without additional treatment. Five patients after reaching protective T-cell levels needed pre-emptive therapy, because they developed graft-versus-host disease (GvHD). HSCT recipients reconstituting protective levels of HCMV-specific T-cells in the absence of GvHD are no longer at risk for HCMV disease, at least within 3 years after transplantation. The decision to treat HCMV infection in young HSCT recipients may be taken by combining virological and immunological findings.     

DNA immunization against tissue-restricted antigens enhances tumor immunity after allogeneic hemopoietic stem cell transplantation

Malignant relapse remains a major problem for recipients of allogeneic hemopoietic stem cell transplantation (HSCT). We hypothesized that immunization of allogeneic HSCT recipients against tissue-restricted Ags using DNA vaccines would decrease the risk of relapse without enhancing graft-vs-host disease (GVHD). Using the mouse B16 melanoma model, we found that post-HSCT DNA immunization against a single tumor Ag induces tumor rejection that is significantly greater than HSCT alone in a T cell-depleted MHC-matched minor Ag-mismatched allogeneic HSCT model (LP --> B6). In treatment models, post-HSCT DNA immunization provides significantly greater overall survival than the vaccine alone. Donor leukocyte infusion further enhances tumor-free survival, including in treatment models. There was no GVHD in HSCT recipients treated with DNA vaccination and donor leukocyte infusion. Further analysis demonstrated that these effects are dependent on CD8+ T cells of donor origin that recognize multiple epitopes. These results demonstrate that DNA immunization against tissue-restricted Ags after allogeneic T cell-depleted HSCT can induce potent antitumor effects without causing GVHD.     

Potential of glycosylation research in graft versus host disease after allogeneic hematopoietic stem cell transplantation

BackgroundGlycans, complex oligosaccharides, are directly involved in almost every biological process, have a fundamental role in the immune system, and are probably involved in nearly every human disease. However, glycosylation has been greatly ignored in the area of allogeneic hematopoietic stem cell transplantation (alloHSCT) and graft versus host disease (GVHD). Both acute and chronic GVHD are multisystemic debilitating immunological disturbances arising after alloHSCT.Scope of reviewIn this paper, we review the glycosylation research already done in the field of alloHSCT and GVHD and evaluate further potential of glycan analysis in GVHD by looking into resembling inflammatory and autoimmune conditions.Major ConclusionsGlycan research could bring significant improvement in alloHSCT procedure with reduction in following complications, such as GVHD. Identifying glycan patterns that induce self-tolerance and the ones that cause the auto- and allo-immune response could lead to innovative and tissue-specific immunomodulative therapy instead of the current immunosuppressive treatment, enabling preservation of the graft-versus-tumor effect. Moreover, improved glycan pattern analyses could offer a more complete assessment and greatly needed dynamic biomarkers for GVHD.General significanceThis review is written with a goal to encourage glycan research in the field of alloHSCT and GVHD as a perspective tool leading to improved engraftment, discovery of much needed biomarkers for GVHD, enabling an appropriate therapy and improved monitoring of therapeutic response. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.     

Enhanced immune reconstitution by sex steroid ablation following allogeneic hemopoietic stem cell transplantation

Delayed immune reconstitution in adult recipients of allogeneic hemopoietic stem cell transplantations (HSCT) is related to age-induced thymic atrophy. Overcoming this paucity of T cell function is a major goal of clinical research but in the context of allogeneic transplants, any strategy must not exacerbate graft-vs-host disease (GVHD) yet ideally retain graft-vs-tumor (GVT) effects. We have shown sex steroid ablation reverses thymic atrophy and enhances T cell recovery in aged animals and in congenic bone marrow (BM) transplant but the latter does not have the complications of allogeneic T cell reactivity. We have examined whether sex steroid ablation promoted hemopoietic and T cell recovery following allogeneic HSCT and whether this benefit was negated by enhanced GVHD. BM and thymic cell numbers were significantly increased at 14 and 28 days after HSCT in castrated mice compared with sham-castrated controls. In the thymus, the numbers of donor-derived thymocytes and dendritic cells were significantly increased after HSCT and castration; donor-derived BM precursors and developing B cells were also significantly increased. Importantly, despite restoring T cell function, sex steroid inhibition did not exacerbate the development of GVHD or ameliorate GVT activity. Finally, IL-7 treatment in combination with castration had an additive effect on thymic cellularity following HSCT. These results indicate that sex steroid ablation can profoundly enhance thymic and hemopoietic recovery following allogeneic HSCT without increasing GVHD and maintaining GVT.     

Molecular monitoring of immune reconstitution after haploidentical stem cell transplantation

Haploidentical hematopoietic stem cell transplantation from a mismatched family member is an alternative treatment for transplant candidates who lack a HLA-matched related or an appropriate unrelated donor. One of main obstacles to successful haploidentical transplantation is slow immune reconstitution which significantly increases the risk of opportunistic infections, graft-vs-host-disease and disease relapse. Immune reconstitution is conventionally estimated by phenotypic recovery of immune cells according to lineage and/or by in vitro evidence of cell function. The limitations of these approaches include the sensitivity and specificity of phenotype markers, the availability of antibodies, the instability of long-term cell culture and the laborious nature of cell-function assays. Investigators have sought alternative approaches that are more sensitive, specific and simple, and that allow high-throughput testing for use in clinical transplantation. In this mini-review, we briefly introduce the concept of "molecular monitoring of immune-reconstitution" and discuss recent progress in this field achieved by our laboratory and other groups. We also propose future directions for clinical research incorporating these novel concepts.     

CAR19/22 T cell cocktail therapy for B-ALL relapsed after allogeneic hematopoietic stem cell transplantation

B cell acute lymphocytic leukemia (B-ALL) patients who have relapsed after hematopoietic stem cell transplantation (HSCT) have a poor prognosis, and there is currently no standard approach available. Chimeric antigen receptor (CAR)-T cells induce high rates of initial response and long-term remission among patients with B-cell malignancies, especially B-ALL. Meanwhile, sequential infusion of CAR19/22 T cells has been proven to be effective at preventing tumor immune escape. In the present study, we retrospectively analyzed 23 B-ALL patients who relapsed after allogeneic (allo)-HSCT and underwent sequential infusion of CAR19/22 T cells, including nine donor-derived and 14 recipient-derived, in our center from July 2016 to July 2020, to evaluate the safety and efficacy of the cocktail of two single-specific CAR-T cells in B-ALL patients relapsed after transplantation. Except for one patient refusing evaluation, the remaining 22 patients achieved minimal residual disease (MRD)-negative complete remission within 30 days after CAR-T infusion. Most toxicities were slight and reversible. The estimated 12-month progression-free survival (PFS) rate was 59.2% (95% confidence interval [CI], 35.9% to 76.5%), and the estimated 12-month overall survival (OS) rate was 67.4% (95% CI, 43.2% to 83.1%). Only two patients had CD19-negative recurrence. In addition, early recurrence after transplantation, graft-versus-host disease (GVHD) and severe infection after CAR-T infusion were poor prognostic factors. Our results indicate that sequential infusion of CAR19/22 T cells is safe and effective for relapsed ALL patients after HSCT. This trial was registered at www.chictr.org.cn as #ChiCTR-OPN-16008526.