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

The role of immune reconstitution in relapse after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Leukemia relapse following stem cell transplantation remains a significant barrier to long-term remission. Timely and balanced immune recovery after transplantation is crucial for preventing leukemia relapse.

AREAS COVERED

After an extensive literature search of PubMed and Web of Science through October 2023, we provide an overview of the dynamics of immune reconstitution and its role in controlling leukemia relapse. We also discuss strategies to promote immune reconstitution and reduce disease recurrence following allogeneic hematopoietic stem cell transplantation.

EXPERT OPINION

Immune reconstitution after transplantation has substantial potential to prevent relapse and might predict disease recurrence and prognosis. High dimensional cytometry, multi-omics, and T cell repertoire analysis allow for a more comprehensive and detailed understanding of the immune system's dynamics post-transplantation, and contribute to the identification of rare immune cell subsets or potential biomarkers associated with successful immune reconstitution or increased risk of complications. Strategies to enhance the immune system, such as adoptive immunotherapy and cytokine-based therapy, have great potential for reducing leukemia relapse after transplantation. Future research directions should focus on refining patient selection for these therapies, implementing appropriate and timely treatment, investigating combination approaches to maximize therapeutic outcomes, and achieving a robust graft-versus-leukemia (GVL) effect while minimizing graft-versus-host disease (GVHD) for optimal results.

Current status and new experimental diagnostic methods of invasive fungal infections after hematopoietic stem cell transplantation

Invasive fungal infections (IFIs) are common and life-threatening complications in post-hematopoietic stem cell transplantation (post-HSCT) recipients, Severe IFIs can lead to systemic infection and organ damage, which results in high mortality in HSCT recipients. With the development of the field of fungal infection diagnosis, more and more advanced non-culture diagnostic tools have been developed, such as glip biosensors, metagenomic next-generation sequencing, Magnetic Nanoparticles and Identified Using SERS via AgNPs+ , and artificial intelligence-assisted diagnosis. The advanced diagnostic approaches contribute to the success of HSCT and improve the overall survival of post-HSCT leukemia patients by supporting therapeutical decisions. This review provides an overview of the characteristics of two high-incidence IFIs in post-HSCT recipients and discusses some of the recently developed IFI detection technologies. Additionally, it explores the potential application of cationic conjugated polymer fluorescence resonance energy transfer (CCP-FRET) technology for IFI detection. The aim is to offer insights into selecting appropriate IFI detection methods and gaining an understanding of novel fungal diagnostic approaches in laboratory settings.

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

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

Clinical characteristics and outcomes of Epstein-Barr virus viral load after allogeneic hematopoietic stem cell transplantation

Epstein-Barr virus (EBV) reactivation can occur following allogenic hematopoietic stem cell transplantation (allo-HSCT). However, the clinical characteristics and outcomes of EBV-viral load are not well known. Thus, we retrospectively analyzed the clinical features and prognostic impact of the EBV viral load in 121 allo-HSCT recipients from our hospital. EBV DNA quantification was performed in whole blood after transplantation. Patients were grouped based on whether EBV DNA quantification reached > 1000 copies/mL during follow-up (N = 50) or not (N = 71). Patients with EBV > 1000 EBV copies/mL were relatively more common in the groups with graft versus host disease (GVHD) prophylaxis including ATG, haploidentical donor type, peripheral blood as a donor source, and acute GVHD II-IV. The 20-month OS and DFS were not significantly different between patients with < 1000 EBV copies/mL and patients with > 1000 EBV copies/mL (20-month OS, 56.0% vs. 60.6%; p = 0.503, 20-month DFS, 50.0% vs. 57.7%; p = 0.179). Immunosuppressant (ISS) dose reduction was achieved after the maximum increase in EBV in 41/50 (82%) patients. Additionally, 30/50 (60%) patients achieved a 50% dose reduction or no restarting of ISS within 3 months of the maximum EBV increase. Among cases wherein EBV DNA quantification reached > 1000 copies/mL, those that achieved rapid dose reduction of ISS tended to have longer overall survival ("not reached" vs 5.4 months, p < 0.001) and disease-free survival (88.4 months vs 5.3 months, p < 0.001) than those in patients who did not. Our data highlight the importance of rapid ISS reduction in post-transplant EBV reactivation.

A successfully cured case of cytomegalovirus multiple organ infection after hematopoietic stem cell transplantation: A case report

Cytomegalovirus (CMV) infection is one of the most common infectious complications following hematopoietic stem cell transplantation (HSCT); however, cases involving multiple organs at the same time are rare. The present study describes a case of CMV pneumonia combined with CMV DNAemia and CMV cystitis after HSCT. A 33-year-old male patient with acute myeloid leukemia was treated with HSCT. The first month after HSCT, the patient developed a cough and shortness of breath. At 2 months post-HSCT, the patient developed hematuria. The CMV DNA levels in the blood and urine were elevated; bronchoalveolar lavage fluid (BALF) was also positive for CMV DNA. Heterotypic cells exhibiting a large nuclear morphology were observed in the BALF and bronchial brushes. Recurrent and progressive ground-glass opacities were evident on chest computed tomography. The patient was diagnosed with CMV pneumonia complicated by CMV DNAemia and CMV cystitis, and was treated with a combination of ganciclovir and foscarnet, along with immunoglobulin therapy. The patient was cured and discharged. It was determined that the CMV DNA in the blood was inconsistent with that in the BALF, which delayed the early diagnosis of CMV pneumonia. The association between T-cell immune function and the therapeutic efficacy for CMV multi-organ infection following HSCT is known to be significant. Moreover, the timely administration of ganciclovir and foscarnet in combination with immunoglobulin therapy demonstrated favorable clinical outcomes.

Joint models quantify associations between immune cell kinetics and allo-immunological events after allogeneic stem cell transplantation and subsequent donor lymphocyte infusion

Alloreactive donor-derived T-cells play a pivotal role in alloimmune responses after allogeneic hematopoietic stem cell transplantation (alloSCT); both in the relapse-preventing Graft-versus-Leukemia (GvL) effect and the potentially lethal complication Graft-versus-Host-Disease (GvHD). The balance between GvL and GvHD can be shifted by removing T-cells via T-cell depletion (TCD) to reduce the risk of GvHD, and by introducing additional donor T-cells (donor lymphocyte infusions [DLI]) to boost the GvL effect. However, the association between T-cell kinetics and the occurrence of allo-immunological events has not been clearly demonstrated yet. Therefore, we investigated the complex associations between the T-cell kinetics and alloimmune responses in a cohort of 166 acute leukemia patients receiving alemtuzumab-based TCD alloSCT. Of these patients, 62 with an anticipated high risk of relapse were scheduled to receive a prophylactic DLI at 3 months after transplant. In this setting, we applied joint modelling which allowed us to better capture the complex interplay between DLI, T-cell kinetics, GvHD and relapse than traditional statistical methods. We demonstrate that DLI can induce detectable T-cell expansion, leading to an increase in total, CD4+ and CD8+ T-cell counts starting at 3 months after alloSCT. CD4+ T-cells showed the strongest association with the development of alloimmune responses: higher CD4 counts increased the risk of GvHD (hazard ratio 2.44, 95% confidence interval 1.45-4.12) and decreased the risk of relapse (hazard ratio 0.65, 95% confidence interval 0.45-0.92). Similar models showed that natural killer cells recovered rapidly after alloSCT and were associated with a lower risk of relapse (HR 0.62, 95%-CI 0.41-0.93). The results of this study advocate the use of joint models to further study immune cell kinetics in different settings.

Effect of mTOR Inhibition with Sirolimus on Natural Killer Cell Reconstitution in Allogeneic Stem Cell Transplantation

Sirolimus is an inhibitor of the mammalian target of rapamycin (mTOR) and is emerging as a promising component of graft-versus-host disease (GVHD) prophylaxis regimens in the context of allogeneic hematopoietic stem cell transplantation (HSCT). Multiple studies have explored the clinical benefits of adding sirolimus to GVHD prophylaxis; however, detailed immunologic studies have not yet been carried out in this context. Mechanistically, mTOR is at the center of metabolic regulation in T cells and natural killer (NK) cells and is critical for their differentiation to mature effector cells. Therefore, close evaluation of the inhibition of mTOR in the context of immune reconstitution post-HSCT is warranted. In this work, we studied the effect of sirolimus on immune reconstitution using a biobank of longitudinal samples from patients receiving either tacrolimus/sirolimus (TAC/SIR) or cyclosporin A/methotrexate (CSA/MTX) as conventional GVHD prophylaxis. Healthy donor controls, donor graft material, and samples from 28 patients (14 with TAC/SIR, 14 with CSA/MTX) at 3 to 4 weeks and 34 to 39 weeks post- HSCT were collected. Multicolor flow cytometry was used to perform broad immune cell mapping, with a focus on NK cells. NK cell proliferation was evaluated over a 6-day in vitro homeostatic proliferation protocol. Furthermore, in vitro NK cell responses to cytokine stimulation or tumor cells were evaluated. Systems-level assessment of the immune repertoire revealed a deep and prolonged suppression (weeks 34 to 39 post-HSCT) of the naïve CD4 T cell compartment with relative sparing of regulatory T cells and enrichment of CD69⁺Ki-67⁺HLA-DR⁺ CD8 T cells, independent of the type of GVHD prophylaxis. Early after transplantation (weeks 3 to 4), while patients were still on TAC/SIR or CSA/MTX, we found a relative increase in less-differentiated CD56^bright NK cells and NKG2A⁺CD57^-KIR^- CD56^dim NK cells and a distinct loss of CD16 and DNAM-1 expression. Both regimens led to suppressed proliferative responses ex vivo and functional impairment with preferential loss of cytokine responsiveness and IFN-γ production. Patients who received TAC/SIR as GVHD prophylaxis showed delayed NK cell reconstitution with lower overall NK cell counts and fewer CD56^bright and NKG2A⁺ CD56^dim NK cells. Treatment with sirolimus- containing regimens generated similar immune cell profiles as conventional prophylaxis; however, the NK cell compartment seemed to be composed of slightly more mature NK cells. These effects were also present after the completion of GVHD prophylaxis, suggesting that mTOR inhibition with sirolimus leaves a lasting imprint on homeostatic proliferation and NK cell reconstitution following HSCT.

Extracorporeal membrane oxygenation in adults receiving haematopoietic cell transplantation: an international expert statement

Combined advances in haematopoietic cell transplantation (HCT) and intensive care management have improved the survival of patients with haematological malignancies admitted to the intensive care unit. In cases of refractory respiratory failure or refractory cardiac failure, these advances have led to a renewed interest in advanced life support therapies, such as extracorporeal membrane oxygenation (ECMO), previously considered inappropriate for these patients due to their poor prognosis. Given the scarcity of evidence-based guidelines on the use of ECMO in patients receiving HCT and the need to provide equitable and sustainable access to ECMO, the European Society of Intensive Care Medicine, the Extracorporeal Life Support Organization, and the International ECMO Network aimed to develop an expert consensus statement on the use of ECMO in adult patients receiving HCT. A steering committee with expertise in ECMO and HCT searched the literature for relevant articles on ECMO, HCT, and immune effector cell therapy, and developed opinion statements through discussions following a Quaker-based consensus approach. An international panel of experts was convened to vote on these expert opinion statements following the Research and Development/University of California, Los Angeles Appropriateness Method. The Appraisal of Guidelines for Research and Evaluation statement was followed to prepare this Position Paper. 36 statements were drafted by the steering committee, 33 of which reached strong agreement after the first voting round. The remaining three statements were discussed by all members of the steering committee and expert panel, and rephrased before an additional round of voting. At the conclusion of the process, 33 statements received strong agreement and three weak agreement. This Position Paper could help to guide intensivists and haematologists during the difficult decision-making process regarding ECMO candidacy in adult patients receiving HCT. The statements could also serve as a basis for future research focused on ECMO selection criteria and bedside management.

Outcomes and risk factors of hemorrhagic cystitis in pediatric allogeneic hematopoietic stem cell transplantation recipients using different graft source and condition with severe aplastic anemia

BACKGROUND

Hemorrhagic cystitis (HC) is a severe complication of allo-HSCT, characterized by irritative symptoms of the urinary tract and a higher morbidity rate. The risk factors and prognosis of HC are still unclear.

OBJECTIVE

The objective of this study is to identify risk factors and outcomes to improve treatment in pediatric SAA patients undergoing HSCTs in the Children's Hospital of Soochow University.

METHODS

A total of 97 SAA patients as a cohort were enrolled from 2010 to 2019 in the Children's Hospital of Soochow University and a number of factors related to HC and outcomes were analysed. In all transplants (except UCBT), patients received a combination of G-CSF stimulated bone marrow (BM) and peripheral blood stem cell (PBSC). The minimum number of CD34 + cells is 5 × 10⁶ cells/kg.

RESULTS

Mononuclear cells dose (MNC, cut off: 8.53 × 10⁸/kg) and grade II-IV acute graft versus host disease (aGVHD) were identified as independent risk factors for HC. Patients without HC had better overall survival (OS) than with HC (No HC: 98.6%±1.4% vs HC: 87.4% ± 6.8%, p = 0.03).

CONCLUSION

We concluded that aGVHD and MNC dose in graft might play an important role in the development of HC in pediatric SAA patients undergoing allo-HSCT. HC is also a key complication affecting the prognosis of children with SAA after allo-HSCT.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Safety and Immunogenicity After a Three-Dose SARS-CoV-2 Vaccine Schedule in Allogeneic Stem Cell Transplant Recipients

In allogeneic stem cell transplant (Allo-SCT) recipients, the cell-mediated and humoral immunogenicity of the 3-dose SARS-CoV-2 vaccination schedule has not been investigated in prospective studies. In a prospective cohort, we recruited 122 Allo-SCT recipients since August 2021, when Ontario began offering a 3-dose vaccine schedule for Allo-SCT recipients. We determined humoral and cell-mediated immunity and adverse effects of the 3-dose SARS-COV-2 vaccination schedule in Allo-SCT recipients. In immunogenicity analysis (n = 95), the median (interquartile range [IQR]) antibody titer against the receptor-binding domain (RBD) of the spike (S) protein after the third dose (10,358.0 U/mL [IQR = 673.9-31,753.0]) was significantly higher than that after the first (10.2 U/mL [IQR = 0.6-37.0]) and the second doses (125.6 U/mL [IQR = 2.8-1251.0]) (P < .0001). The haploidentical donor status was an independent risk factor (adjusted odds ratio = 7.67, 95% confidence interval [CI], 1.86-31.60) for suboptimal antibody response (anti-RBD < 100 U/mL). S-specific CD4⁺ and CD8⁺ T-cell responses were measured in a subset of Allo-SCT recipients (n = 20) by flow cytometry. Most developed antigen-specific CD4⁺ (55%-80%) and CD8⁺ T-cells (80%) after 2 doses of vaccine. Frequencies of CD4⁺ polyfunctional (P = .020) and IL-2 monofunctional (P = .013) T-cells significantly increased after the third dose. Twenty-three episodes (23/301 doses [7.6%]) of new-onset or worsening pre-existing graft-versus-host disease (GVHD) occurred, including 4 episodes after the third dose. We observed 4 relapses (3.27%). Seven patients developed SARS-CoV-2 infection despite vaccination, although none required hospitalization. In conclusion, the 3-dose SARS-CoV-2 vaccine schedule provided immunity associated with a low risk of GVHD and other adverse effects. This prospective cohort showed that the third dose of SARS-CoV-2 vaccine in allogeneic stem cell transplant recipients promoted better humoral and cellar immune responses than after the initial series without increasing the risk of GVHD or severe adverse effects.

Mucosal-associated invariant T cells predict increased acute graft-versus-host-disease incidence in patients receiving allogeneic hematopoietic stem cell transplantation

BACKGROUND

Mucosal-associated invariant T (MAIT) cells are innate-like T cells, some studies have reported that the number of circulating MAIT cells reduced in patients with acute graft-versus-host-disease (aGVHD) development. However, the role of donor MAIT cells on aGVHD development and subsequent functional change still remain unclear.

METHODS

The study recruited 86 patients with hematological malignancies who underwent allogeneic hematopoietic cell transplantation (HCT) from May 1, 2018 to June 30, 2019. MAIT cells, their subset, and cytokine levels were measured by flow cytometry. Gray's test was used to assess the impact of graft MAIT cell proportion and number on aGVHD incidence. The Cox proportional hazard model was used in the multivariate analysis. The comparison for continuous variables was assessed using Mann-Whitney analysis. RNA-sequencing was performed to investigate the possible molecular pathway changes.

RESULTS

Our study showed that the proportion of MAIT cells in grafts was not different from normal controls, but the CD4/8 subsets were altered. Taking the median of the proportion and number of MAIT cells in the graft as the threshold, the results showed that the incidence of grade B-D aGVHD in patients with MAIT cell proportion ≥ 3.03% was significantly higher than that in patients with MAIT cell proportion < 3.03% (56.3%, 95% CI 37.1-71.2 versus 23.1%, 95% CI 13.8-46.2; P = 0.038).The number of MAIT cells in the graft was not associated with aGVHD development (P = 0.173), however, when the graft contained more CD4 positive, CD8 positive, and CD4/CD8 double-positive MAIT cells, the incidence of aGVHD was significantly increased (P = 0.019, P = 0.035 and P = 0.027, respectively). Besides, reduced frequencies and counts of circulating MAIT cells were observed in patients with aGVHD when compared to patients without aGVHD, accompanied by enhanced production of Tumor necrosis factor-α, Interferon-γ and upregulated programmed death-1, CXC Chemokine Receptor-6 (CXCR6) and CD38 expression. Gene set enrichment analysis of MAIT cell RNA-seq data showed interferon-α response pathway upregulated in aGVHD patients when compared with patients without aGVHD and healthy controls.

CONCLUSIONS

Our study shows that MAIT cells in grafts and peripheral blood are both closely related to the aGVHD development post allogeneic HCT. Interferon-α response pathway perhaps is a critical regulation mechanism for the MAIT cell involvement in aGVHD development.

TCRαβ-Depleted Haploidentical Grafts Are a Safe Alternative to HLA-Matched Unrelated Donor Stem Cell Transplants for Infants with Severe Combined Immunodeficiency

Hematopoietic stem cell transplantation and gene therapy are the only curative therapies for severe combined immunodeficiency (SCID). In patients lacking a matched donor, TCRαβ/CD19-depleted haploidentical family donor transplant (TCRαβ-HaploSCT) is a promising strategy. Conditioned transplant in SCID correlates to better myeloid chimerism and reduced immunoglobulin dependency. We studied transplant outcome in SCID infants according to donor type, specifically TCRαβ-HaploSCT, and conditioning, through retrospective cohort analysis of 52 consecutive infants with SCID transplanted between 2013 and 2020. Median age at transplant was 5.1 months (range, 0.8-16.6). Donors were TCRαβ-HaploSCT (n = 16, 31.4%), matched family donor (MFD, n = 15, 29.4%), matched unrelated donor (MUD, n = 9, 17.6%), and matched unrelated cord blood (CB, n = 11, 21.6%). Forty-one (80%) received fludarabine/treosulfan-based conditioning, 3 (6%) had alemtuzumab only, and 7 (14%) received unconditioned infusions. For conditioned transplants (n = 41), 3-year overall survival was 91% (95% confidence interval, 52-99%) for TCRαβ-HaploSCT, 80% (41-98%) for MFD, 87% (36-98%) for MUD, and 89% (43-98%) for CB (p = 0.89). Cumulative incidence of grade II-IV acute graft-versus-host disease was 11% (2-79%) after TCRαβ-HaploSCT, 0 after MFD, 29% (7-100%) after MUD, and 11% (2-79%) after CB (p = 0.10). 9/10 patients who received alemtuzumab-only or unconditioned transplants survived. Myeloid chimerism was higher following conditioning (median 47%, range 0-100%) versus unconditioned transplant (median 3%, 0-9%) (p < 0.001), as was the proportion of immunoglobulin-free long-term survivors (n = 29/36, 81% vs n = 4/9, 54%) (p < 0.001). TCRαβ-HaploSCT has comparable outcome to MUD and is a promising alternative donor strategy for infants with SCID lacking MFD. This study confirms that conditioned transplant offers better myeloid chimerism and immunoglobulin freedom in long-term survivors.

An ISCT Stem Cell Engineering Committee Position Statement on Immune Reconstitution: the importance of predictable and modifiable milestones of immune reconstitution to transplant outcomes

Allogeneic stem cell transplantation is a potentially curative therapy for some malignant and non-malignant disease. There have been substantial advances since the approaches first introduced in the 1970s, and the development of approaches to transplant with HLA incompatible or alternative donors has improved access to transplant for those without a fully matched donor. However, success is still limited by morbidity and mortality from toxicity and imperfect disease control. Here we review our emerging understanding of how reconstitution of effective immunity after allogeneic transplant can protect from these events and improve outcomes. We provide perspective on milestones of immune reconstitution that are easily measured and modifiable.

Rates and Predictors of Nonadherence to the Post-Allogeneic Hematopoietic Cell Transplantation Medical Regimen in Patients and Caregivers

Allogeneic hematopoietic cell transplantation (HCT) requires a complex, multicomponent medical regimen after hospital discharge. Patients must manage multiple medications; care for their catheter; minimize exposure to sources of potential infection; follow diet, exercise, and self-care guidelines; and attend frequent follow-up medical appointments. Their caregivers are tasked with helping them manage the regimen. Despite the importance of this management in preventing adverse clinical outcomes, there has been little study of regimen nonadherence and its predictors. We sought to prospectively determine rates and predictors of nonadherence to components of the post-HCT medical regimen during the first 8 weeks after hospital discharge. Patients (n = 92) and their caregivers (n = 91) (total n = 183) completed interview assessments pre-HCT, and at 4 weeks and 8 weeks after hospital discharge post-HCT. Sociodemographic factors (eg, age, sex), patient clinical status (eg, disease type, donor type), patient and caregiver self-reported health-related factors (eg, medical comorbidities), and patient and caregiver psychosocial factors (eg, anxiety, depression, HCT task-specific and general self-efficacy, relationship quality) were assessed pre-HCT. Nonadherence to each of 17 regimen tasks was assessed at 4 and 8 weeks after hospital discharge via self and caregiver collateral reports. Nonadherence rates varied among tasks, with 11.2% to 15.7% of the sample reporting nonadherence to immunosuppressant medication, 34.8% to 38.6% to other types of medications, 14.6% to 67.4% to required infection precautions, and 27.0% to 68.5% to lifestyle-related behaviors (eg, diet/exercise). Nonadherence rates were generally stable but worsened over time for lifestyle-related behaviors. The most consistent nonadherence predictors were patient and caregiver pre-HCT perceptions of lower HCT task efficacy. Higher caregiver depression, caregiver perceptions of poorer relationship with the patient, having a nonspousal caregiver, and having diseases other than acute myelogenous leukemia also predicted greater nonadherence in 1 or more areas. Rates of nonadherence varied across tasks, and both patient and caregiver factors, particularly self-efficacy, predicted nonadherence. The findings highlight the importance of considering not only patient factors, but also caregiver factors, in post-HCT regimen nonadherence.

[Correlation between immune reconstitution and chronic graft-versus-host disease after unrelated cord blood transplantation and sibling peripheral blood stem cell transplantation]

Objective: To explore the relationship between the reconstitution of immune cells in patients with hematological malignancies and the occurrence of chronic graft-versus-host disease (cGVHD) after treatment with unrelated cord blood transplantation (UCBT) and sibling peripheral blood stem cell transplantation (PBSCT) . Methods: A total of 124 patients undergoing allogenic hematopoietic stem cell transplantation (allo-HSCT) in the First Affiliated Hospital of University of Science and Technology of China from March 2018 to August 2019, including 96 patients with UCBT and 28 patients with PBSCT. Peripheral blood immune cells of patients with UCBT and PBSCT were detected at 1, 3, 6, 9, and 12 months after transplantation using flow cytometry, and both UCBT and PBSCT patients were divided into cGVHD and non-cGVHD groups based on whether cGVHD occurred to explore the correlation between the immune cells reconstitution of the two types of transplantation and cGVHD. Results: ①The cumulative incidence of the moderate to severe cGVHD in the UCBT group was significantly lower than that in the PBSCT group[9.38% (95% CI 3.35%-15.02%) vs 28.57% (95% CI 9.72%-43.50%) , P=0.008]; the 2-year cumulative incidence of cGVHD and moderate to severe cGVHD in the UCBT group was lower than that in the PBSCT group[15.60% (95% CI 9.20%-23.60%) vs 32.10% (95% CI 15.80%-49.70%) , P=0.047; 10.40% (95% CI 5.30%-17.50%) vs 28.60% (95% CI 13.30%-46.00%) , P=0.014]. ②The absolute counts of CD4(+)T cells in the UCBT group were higher than those in the PBSCT group at 6, 9, and 12 months after transplantation[59.00 (36.70-89.65) ×10(7)/L vs 31.40 (18.10-44.00) ×10(7)/L, P<0.001; 71.30 (49.60-101.45) ×10(7)/L vs 41.60 (25.82-56.27) ×10(7)/L, P<0.001; 83.00 (50.17-121.55) ×10(7)/L vs 44.85 (31.62-62.10) ×10(7)/L, P<0.001]; the proportions of CD4(+)T cells in the UCBT group were always higher than those in the PBSCT group (P<0.05) . The absolute counts and proportions of B cells in the PBSCT group were higher than those in the UCBT group at the first month after transplantation[0.70 (0.30-1.70) ×10(7)/L vs 0.10 (0-0.30) ×10(7)/L, P<0.001; 0.45% (0.30%-2.20%) vs 0.20% (0.10%-0.40%) , P=0.002]; the absolute counts and proportions of B cells in the UCBT group were higher than those in the PBSCT group at 9 and 12 months after transplantation[53.80 (28.00-103.20) ×10(7)/L vs 23.35 (5.07-35.00) ×10(7)/L, P<0.001; 21.45 (11.80-30.45) % vs 9.00% (3.08%-16.73%) , P<0.001. 66.70 (36.97-98.72) ×10(7)/L vs 20.85 (7.72-39.40) ×10(7)/L, P<0.001; 22.20% (14.93%-29.68%) vs 8.75% (5.80%-18.93%) , P<0.001]. The absolute counts and proportions of regulatory B (Breg) cells in the UCBT group were higher than those in the PBSCT group at 6, 9, and 12 months after transplantation[1.23 (0.38-3.52) ×10(7)/L vs 0.05 (0-0.84) ×10(7)/L, P<0.001; 5.35% (1.90%-12.20%) vs 1.45% (0-7.78%) , P=0.002. 2.25 (1.07-6.71) ×10(7)/L vs 0.12 (0-0.77) ×10(7)/L, P<0.001; 6.25% (2.00%-12.33%) vs 0.80% (0-5.25%) , P<0.001. 3.69 (0.83-8.66) ×10(7)/L vs 0.46 (0-0.93) ×10(7)/L, P<0.001; 6.15% (1.63%-11.75%) vs 1.40% (0.18%-5.85%) , P<0.001].The absolute counts and proportions of CD3(+)T cells, CD8(+)T cells, and Treg cells in the UCBT group were not significantly different from those in the PBSCT group. ③The absolute counts of B cells in the non-cGVHD group of UCBT patients were higher than those in the moderate to severe cGVHD group at 6 and 12 months after transplantation (P=0.038, P=0.043) ; the proportions of B cells in the non-cGVHD group were higher than those in the moderate to severe cGVHD group at 6 months after transplantation (P=0.049) . The absolute counts of Breg cells in the non-cGVHD group of patients with UCBT were higher than those in the moderate to severe cGVHD group at 6, 9, and 12 months after transplantation (P=0.006, P=0.028, P=0.050) ; the proportions of Breg cells in the non-cGVHD group were higher than those in the moderate to severe cGVHD group at 9 months after transplantation (P=0.038) . ④The absolute counts and proportions of B and Breg cells in the non-cGVHD group of patients with PBSCT were not statistically different than those in the moderate to severe cGVHD group. Conclusion: In the process of immune cell reconstitution, the Breg cells in the UCBT group were higher than those in the PBSCT group, and the Breg cells in the non-cGVHD group of the two types of transplantation were always higher than those in the moderate to severe cGVHD group, indicating that Breg cells can reduce the occurrence of cGVHD, revealing the possible reason for the lower incidence of cGVHD in the UCBT group.

Potential of Mesenchymal Stem Cells in the Rejuvenation of the Aging Immune System

Rapid growth of the geriatric population has been made possible with advancements in pharmaceutical and health sciences. Hence, age-associated diseases are becoming more common. Aging encompasses deterioration of the immune system, known as immunosenescence. Dysregulation of the immune cell production, differentiation, and functioning lead to a chronic subclinical inflammatory state termed inflammaging. The hallmarks of the aging immune system are decreased naïve cells, increased memory cells, and increased serum levels of pro-inflammatory cytokines. Mesenchymal stem cell (MSC) transplantation is a promising solution to halt immunosenescence as the cells have excellent immunomodulatory functions and low immunogenicity. This review compiles the present knowledge of the causes and changes of the aging immune system and the potential of MSC transplantation as a regenerative therapy for immunosenescence.

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

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

Efficacy and safety of mesenchymal stem cells co-infusion in allogeneic hematopoietic stem cell transplantation: a systematic review and meta-analysis

Background

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is life-saving for severe hematological conditions. However, its outcomes need further improvement, and co-infusion of mesenchymal stem cells (MSCs) may show promise. A growing body of research on this subject exists, while the results of different trials are conflicting. A systematic review and meta-analysis is needed to appraise the real efficacy and safety of MSC co-transplantation in allo-HSCT.

Methods

Studies comparing MSC co-transplantation in allo-HSCT with allo-HSCT alone were searched in six medical databases from inception to June 10, 2020. The primary outcomes were engraftment and graft-versus-host disease (aGVHD and cGVHD, respectively). Other outcomes included overall survival (OS), relapse rate (RR), non-relapse mortality (NRM), and immune reconstitution. Information was independently extracted by two investigators. Methodological quality was assessed using the Cochrane Collaboration tool. Meta-analysis was performed using RevMan 5.4.

Results

Six randomized controlled trials (RCTs) and 13 non-randomized controlled trials (nRCTs) were included. MSC co-infusion resulted in shorter times to neutrophil engraftment (RCTs: standardized mean difference (SMD) − 1.20, p = 0.04; nRCTs: SMD − 0.54, p = 0.04) and platelet engraftment (RCTs: SMD − 0.60, p = 0.04; nRCTs: SMD − 0.70, p = 0.01), a lower risk of cGVHD (RCTs: risk ratio (RR) 0.53, p = 0.01; nRCTs: RR 0.50, p <  0.01), and a slightly positive trend towards reducing the risk of aGVHD and NRM, without affecting RR and OS. Subgroup analyses revealed that when MSCs were co-transplanted, children and adolescents, and patients receiving human leukocyte antigen (HLA)-nonidentical HSCT showed improvements in engraftment and incidence of GVHD and NRM; adults and patients who received HLA-identical HSCT had lower cGVHD; patients with malignancies exhibited improvements in GVHD and NRM incidence; and patients with non-malignancies experienced accelerated engraftment. Notably, a reduced OS was observed in patients with hematological malignancies undergoing HLA-identical HSCT.

Conclusion

MSC co-infusion generally improved engraftment and reduced cGVHD, without increasing mortality or relapse. Regarding aGVHD and NRM, the effects of MSCs were not quite significant. Specifically, our data support the utilization of MSC co-transplantation in children and young individuals with HLA-nonidentical HSCT, but not in adult patients with hematological malignancies undergoing HLA-identical HSCT.

Immune Reconstitution in the Aging Host: Opportunities for Mechanism-Based Therapy in Allogeneic Hematopoietic Cell Transplantation

Older patients with hematologic malignancies are increasingly considered for allogeneic hematopoietic cell transplantation with encouraging outcomes. While aging-related thymic dysfunction remains a major obstacle to optimal and timely immune reconstitution post- transplantation, recent accumulating evidence has suggested that various aging hallmarks such as cellular senescence, inflamm-aging, and hematopoietic stem cell exhaustion, could also impact immune reconstitution post-transplantation in both thymic-dependent and independent manner. Here we review molecular and cellular aspects of immune senescence and immune rejuvenation related to allogeneic hematopoietic cell transplantation among older patients and discuss potential strategies for mechanism-based therapeutic intervention.

Co-Transplantation of Haploidentical Stem Cells and a Dose of Unrelated Cord Blood in Pediatric Patients with Thalassemia Major

Allogeneic stem cell transplantation is a cure for patients suffering from thalassemia major (TM). Historically, patients were limited by the selection of donors, while the advancement of haploidentical stem cell transplantation (haplo-SCT) has greatly expanded the donor pool. However, the outcomes of haplo-SCT in TM recipients vary between different programs. In this study, we retrospectively studied 73 pediatric TM patients (median age, 7 years; range, 3 to 14 years) who underwent haplo-cord transplantation. Both the estimated overall survival and transfusion-free survival were 95.26% (CI 95.77% to 96.23%). Neither primary nor secondary graft failures were observed. The median follow-up period was 811 days (range, 370 to 1433 days). Median neutrophil and platelet engraftment times were 22 days (range, 8 to 48 days) and 20 days (range, 8 to 99 days), respectively. Acute graft-versus-host disease (aGVHD) was observed in 52% of patients and of these, 25% developed grade III to IV aGVHD. Cord blood engraftment was associated with delayed immune recovery and increased aGVHD severity. Viral DNAemia occurred in a relatively high proportion of patients but only 7% of patients developed CMV disease, while another 7% of patients had post-transplantation lymphoproliferative disorder. Long-term complication outcomes were good. Only one patient developed extensive chronic GVHD. No surviving patients were reliant on blood transfusion by the time this manuscript was submitted. This is one of the largest studies on the outcomes of pediatric TM patients who received stem cell transplantations from alternative donors. The haplo-cord program is safe and practical for TM patients that do not have matched donors.

A Review of Infections After Hematopoietic Cell Transplantation Requiring PICU Care: Transplant Timeline Is Key

Despite major advances in antimicrobial prophylaxis and therapy, opportunistic infections remain a major cause of morbidity and mortality after pediatric hematopoietic cell transplant (HCT). Risk factors associated with the development of opportunistic infections include the patient's underlying disease, previous infection history, co-morbidities, source of the donor graft, preparative therapy prior to the graft infusion, immunosuppressive agents, early and late toxicities after transplant, and graft-vs.-host disease (GVHD). Additionally, the risk for and type of infection changes throughout the HCT course and is greatly influenced by the degree and duration of immunosuppression of the HCT recipient. Hematopoietic cell transplant recipients are at high risk for rapid clinical decompensation from infections. The pediatric intensivist must remain abreast of the status of the timeline from HCT to understand the risk for different infections. This review will serve to highlight the infection risks over the year-long course of the HCT process and to provide key clinical considerations for the pediatric intensivist by presenting a series of hypothetical HCT cases.

Immune Reconstitution After Allogeneic Haematopoietic Cell Transplantation: From Observational Studies to Targeted Interventions

Immune reconstitution (IR) after allogeneic haematopoietic cell transplantation (HCT) represents a central determinant of the clinical post-transplant course, since the majority of transplant-related outcome parameters such as graft-vs.-host disease (GvHD), infectious complications, and relapse are related to the velocity, quantity and quality of immune cell recovery. Younger age at transplant has been identified as the most important positive prognostic factor for favourable IR post-transplant and, indeed, accelerated immune cell recovery in children is most likely the pivotal contributing factor to lower incidences of GvHD and infectious complications in paediatric allogeneic HCT. Although our knowledge about the mechanisms of IR has significantly increased over the recent years, strategies to influence IR are just evolving. In this review, we will discuss different patterns of IR during various time points post-transplant and their impact on outcome. Besides IR patterns and cellular phenotypes, recovery of antigen-specific immune cells, for example virus-specific T cells, has recently gained increasing interest, as certain threshold levels of antigen-specific T cells seem to confer protection against severe viral disease courses. In contrast, the association between IR and a possible graft-vs. leukaemia effect is less well-understood. Finally, we will present current concepts of how to improve IR and how this could change transplant procedures in the near future.

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

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

Impact of Intestinal Microbiota on Reconstitution of Circulating Monocyte, Dendritic Cell, and Natural Killer Cell Subsets in Adults Undergoing Single-Unit Cord Blood Transplantation

The intestinal microbiota plays a fundamental role in the development of host innate immune cells, such as monocytes, dendritic cells (DCs), and natural killer (NK) cells. We examined the association between intestinal microbiota and subsequent immune reconstitution of circulating monocyte, DC, and NK cell subsets in 38 adult patients undergoing single-unit cord blood transplantation (CBT). A higher diversity of intestinal microbiota at 1 month was significantly associated with higher counts of plasmacytoid DCs at 7 months after CBT, as measured by the Chao1 index. Principal coordinate analysis of unweighted UniFrac distances showed significant differences between higher and lower classical monocyte reconstitution at 7 months post-CBT. The families Neisseriaceae, Burkholderiaceae, Propionibacteriaceae, and Coriobacteriaceae were increased in higher classical monocyte reconstitution at 7 months post-CBT, whereas the family Bacteroidaceae was increased in lower classical monocyte reconstitution at 7 months post-CBT. These data show that intestinal microbiota composition affects immune reconstitution of classical monocyte and plasmacytoid DCs following single-unit CBT.

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

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

Immune Monitoring After Allogeneic Hematopoietic Cell Transplantation: Toward Practical Guidelines and Standardization

Hematopoietic cell transplantation (HCT) is often a last resort, but potentially curative treatment option for children suffering from hematological malignancies and a variety of non-malignant disorders, such as bone marrow failure, inborn metabolic disease or immune deficiencies. Although efficacy and safety of the HCT procedure has increased significantly over the last decades, the majority of the patients still suffer from severe acute toxicity, viral reactivation, acute or chronic graft-versus-host disease (GvHD) and/or, in case of malignant disease, relapses. Factors influencing HCT outcomes are numerous and versatile. For example, there is variation in the selected graft sources, type of infused cell subsets, cell doses, and the protocols used for conditioning, as well as immune suppression and treatment of adverse events. Moreover, recent pharmacokinetic studies show that medications used in the conditioning regimen (e.g., busulphan, fludarabine, anti-thymocyte globulin) should be dosed patient-specific to achieve optimal exposure in every individual patient. Due to this multitude of variables and site-specific policies/preferences, harmonization between HCT centers is still difficult to achieve. Literature shows that adequate immune recovery post-HCT limits both relapse and non-relapse mortality (death due to viral reactivations and GvHD). Monitoring immune parameters post-HCT may facilitate a timely prediction of outcome. The use of standardized assays to measure immune parameters would facilitate a fast comparison between different strategies tested in different centers or between different clinical trials. We here discuss immune cell markers that may contribute to clinical decision making and may be worth to standardize in multicenter collaborations for future trials.