Reconstitution of T Cell Subsets Following Allogeneic Hematopoietic Cell Transplantation

Allogeneic (allo) hematopoietic cell transplantation (HCT) is the only curative treatment option for patients suffering from chemotherapy-refractory or relapsed hematological malignancies. The occurrence of morbidity and mortality after allo-HCT is still high. This is partly correlated with the immunological recovery of the T cell subsets, of which the dynamics and relations to complications are still poorly understood. Detailed information on T cell subset recovery is crucial to provide tools for better prediction and modulation of adverse events. Here, we review the current knowledge regarding CD4+ and CD8+ T cells, γδ T cells, iNKT cells, Treg cells, MAIT cells and naive and memory T cell reconstitution, as well as their relations to outcome, considering different cell sources and immunosuppressive therapies. We conclude that the T cell subsets reconstitute in different ways and are associated with distinct adverse and beneficial events; however, adequate reconstitution of all the subsets is associated with better overall survival. Although the exact mechanisms involved in the reconstitution of each T cell subset and their associations with allo-HCT outcome need to be further elucidated, the data and suggestions presented here point towards the development of individualized approaches to improve their reconstitution. This includes the modulation of immunotherapeutic interventions based on more detailed immune monitoring, aiming to improve overall survival changes

Naive T Cells in Graft Versus Host Disease and Graft Versus Leukemia: Innocent or Guilty?

The outcome of allogeneic hematopoietic cell transplantation (allo-HCT) largely depends on the development and management of graft-versus-host disease (GvHD), infections, and the occurrence of relapse of malignancies. Recent studies showed a lower incidence of chronic GvHD and severe acute GvHD in patients receiving naive T cell depleted grafts compared to patients receiving complete T cell depleted grafts. On the other hand, the incidence of acute GvHD in patients receiving cord blood grafts containing only naive T cells is rather low, while potent graft-versus-leukemia (GvL) responses have been observed. These data suggest the significance of naive T cells as both drivers and regulators of allogeneic reactions. The naive T cell pool was previously thought to be a quiescent, homogenous pool of antigen-inexperienced cells. However, recent studies showed important differences in phenotype, differentiation status, location, and function within the naive T cell population. Therefore, the adequate recovery of these seemingly innocent T cells might be relevant in the imminent allogeneic reactions after allo-HCT. Here, an extensive review on naive T cells and their contribution to the development of GvHD and GvL responses after allo-HCT is provided. In addition, strategies specifically directed to stimulate adequate reconstitution of naive T cells while reducing the risk of GvHD are discussed. A better understanding of the relation between naive T cells and alloreactivity after allo-HCT could provide opportunities to improve GvHD prevention, while maintaining GvL effects to lower relapse risk

Case Report: Lessons Learned From Subsequent Autologous and Allogeneic Hematopoietic Stem Cell Transplantations in a Pediatric Patient With Relapsing Polychondritis

Background: Autologous hematopoietic stem cell transplantation (autoHSCT) is increasingly being recognized as a treatment option for severe refractory autoimmune diseases (AD). However, efficacy is hampered by high relapse rates. In contrast, allogeneic HSCT (alloHSCT) has high potential to cure AD, but is associated with significant morbidity and mortality, and data in AD are limited. Experience with autoHSCT in relapsing polychondritis, a rare episodic inflammatory disorder characterized by destruction of cartilage, is scarce and alloHSCT has not been described before. Case Presentation: Here, we present a case of a 9-year-old girl who was diagnosed with relapsing polychondritis, with severe airway involvement requiring a tracheostomy. The disease proved to be steroid-dependent and refractory to a wide array of disease-modifying anti-rheumatic drugs and biologicals. After an autoHSCT procedure, the disease became inactive for a short period of time, until the patient experienced a relapse after 31 days, accompanied by repopulation of effector/memory CD8+ T cells. Because of persistent inflammation and serious steroid toxicity, including severe osteoporosis, growth restriction, and excessive weight gain, the patient was offered an alloHSCT. She experienced transient antibody-mediated immune events post-alloHSCT, which subsided after rituximab. She ultimately developed a balanced immune reconstitution and is currently still in long-term disease remission, 8 years after alloHSCT. Conclusion: This case adds to the few existing reports on autoHSCT in relapsing polychondritis and gives new insights in its pathogenesis, with a possible role for CD8+ T cells. Moreover, it is the first report of successful alloHSCT as a treatment for children with this severe autoimmune disease

Challenges and opportunities targeting mechanisms of epithelial injury and recovery in acute intestinal graft-versus-host disease

Despite advances in immunosuppressive prophylaxis and overall supportive care, gastrointestinal (GI) graft-versus-host disease (GVHD) remains a major, lethal side effect after allogeneic hematopoietic stem cell transplantation (allo-HSCT). It has become increasingly clear that the intestinal epithelium, in addition to being a target of transplant-related toxicity and GVHD, plays an important role in the onset of GVHD. Over the last two decades, increased understanding of the epithelial constituents and their microenvironment has led to the development of novel prophylactic and therapeutic interventions, with the potential to protect the intestinal epithelium from GVHD-associated damage and promote its recovery following insult. In this review, we will discuss intestinal epithelial injury and the role of the intestinal epithelium in GVHD pathogenesis. In addition, we will highlight possible approaches to protect the GI tract from damage posttransplant and to stimulate epithelial regeneration, in order to promote intestinal recovery. Combined treatment modalities integrating immunomodulation, epithelial protection, and induction of regeneration may hold the key to unlocking mucosal recovery and optimizing therapy for acute intestinal GVHD

Definitions, incidence and outcome of poor graft function after hematopoietic cell transplantation: A systematic review and meta-analysis

Poor graft function (PGF) after allogeneic hematopoietic stem cell transplantation (HCT) is a serious complication with high morbidity and mortality. The reported incidence of PGF, its risk factors and outcome vary substantially between studies. This variability may be explained by heterogeneity in patient cohorts and HCT strategies, differences in the underlying causes of cytopenia, as well as by differences in PGF definition. In this systematic review and meta-analysis, we provide an overview of the various PGF definitions used and determined the impact of this variability on the reported incidence and outcome. We searched MEDLINE, EMBASE and Web of Science up to July 2022, for any study on PGF in HCT recipients. We performed random-effect meta-analyses for incidence and outcome and subgroup analyses based on different PGF criteria. Among 69 included studies (14.265 HCT recipients), we found 63 different PGF definitions, using various combinations of 11 common criteria. The median incidence of PGF was 7% (IQR: 5-11%, 22 cohorts). The pooled survival of PGF patients was 53% (95% CI: 45-61%, 23 cohorts). The most commonly reported risk factors associated with PGF were history of cytomegalovirus infection and prior graft-versus-host disease. Incidence was lower in studies with strict cytopenic cutoffs, while survival was lower for primary compared to secondary PGF. This work indicates that a standardized, quantitative definition of PGF is needed to facilitate clinical guideline development and to advance scientific progress

Allogenic Hematopoietic Stem Cell Transplantation Is Feasible in Pediatric Patients with an Active or Recently Diagnosed Invasive Fungal Infection

Data on the outcome of allogenic hematopoietic stem cell transplantation (HSCT) in pediatric patients with a history of invasive fungal infection (IFI) are limited. The aim of this study was to report on the feasibility and outcome of allogenic HSCT in pediatric patients with an active or recently diagnosed IFI. In this retrospective, single-center study, 317 children underwent an allogenic HSCT (January 2012 to June 2020), of whom 23 had an active or recent (<6 months before transplantation) diagnosis of a probable or proven IFI before HSCT. Medical records were reviewed for data collection. Descriptive statistics were performed. One-year survival was described with Kaplan–Meier analysis. Four proven and 19 probable IFIs were diagnosed. The lungs were the main site of infection (22 out of 23 patients); brain involvement was diagnosed in six patients (26.1%). Aspergillus spp. were the most frequently identified organisms. Of the four patients diagnosed with mucormycosis, three had mixed infections with Aspergillus spp. One patient was diagnosed with Alternaria sinusitis and one patient with an infection with Curvularia spp. with both pulmonary and cutaneous involvement. One year after HSCT, 18 of the 23 patients (78.3%) were alive. Four of the five patients who did not survive died of non–IFI-related causes. One patient died due to a newly developed IFI post-transplant. Three patients showed non-fatal progression of their original IFIs that required prolonged antifungal treatment. Survival of this cohort of high-risk pediatric patients who underwent allogenic HSCT with an active or recently diagnosed IFI was favorable. An active IFI or recent history of IFI should not be a contraindication for proceeding to allogenic HSCT

The Effect of Genetic HLA Matching on Liver Transplantation Outcome: A Systematic Review and Meta-Analysis

OBJECTIVE: We aim to investigate the effects of genetically based HLA matching on patient and graft survival, and acute and chronic rejection after liver transplantation. BACKGROUND: Liver transplantation is a common treatment for patients with end-stage liver disease. In contrast to most other solid organ transplantations, there is no conclusive evidence supporting human leukocyte antigen (HLA) matching for liver transplantations. With emerging alternatives such as transplantation of bankable (stem) cells, HLA matching becomes feasible, which may decrease the need for immunosuppressive therapy and improve transplantation outcomes. METHODS: We systematically searched the PubMed, Embase, and Cochrane databases and performed a meta-analysis investigating the effect of genetic HLA matching on liver transplantation outcomes (acute/chronic rejection, graft failure, and mortality). RESULTS: We included 14 studies with 2682 patients. HLA-C mismatching significantly increased the risk of acute rejection (full mismatching: risk ratio = 1.90, 95% confidence interval = 1.08 to 3.33, P = 0.03; partial mismatching: risk ratio = 1.33, 95% confidence interval = 1.07 to 1.66, P = 0.01). We did not discern any significant effect of HLA mismatching per locus on acute rejection for HLA-A, -B, -DR, and -DQ, nor on chronic rejection, graft failure, or mortality for HLA-DR, and -DQ. CONCLUSIONS: We found evidence that genetic HLA-C matching reduces the risk of acute rejection after liver transplantation while matching for other loci does not reduce the risk of acute rejection, chronic rejection, graft failure, or mortality

Clinical Grade Production of Wilms' Tumor-1 Loaded Cord Blood-Derived Dendritic Cells to Prevent Relapse in Pediatric AML After Cord Blood Transplantation

Hematopoietic cell transplantation (HCT) is a last resort, potentially curative treatment option for pediatric patients with refractory acute myeloid leukemia (AML). Cord blood transplantation (CBT) results in less relapses and less graft-versus-host disease when compared to other sources. Nevertheless, still more than half of the children die from relapses. We therefore designed a strategy to prevent relapses by inducing anti-AML immunity after CBT, using a CB-derived dendritic cell (CBDC) vaccine generated from CD34+ CB cells from the same graft. We here describe the optimization and validation of good manufacturing practice (GMP)-grade production of the CBDC vaccine. We show the feasibility of expanding low amounts of CD34+ cells in a closed bag system to sufficient DCs per patient for at least three rounds of vaccinations. The CBDCs showed upregulated costimulatory molecules after maturation and showed enhanced CCR7-dependent migration toward CCL19 in a trans-well migrations assay. CBDCs expressed Wilms' tumor 1 (WT1) protein after electroporation with WT1-mRNA, but were not as potent as CBDCs loaded with synthetic long peptides (peptivator). The WT1-peptivator loaded CBDCs were able to stimulate T-cells both in a mixed lymphocyte reaction as well as in an antigen-specific (autologous) setting. The autologous stimulated T-cells lysed not only the WT1+ cell line, but most importantly, also primary pediatric AML cells. Altogether, we provide a GMP-protocol of a highly mature CBDC vaccine, loaded with WT1 peptivator and able to stimulate autologous T-cells in an antigen-specific manner. Finally, these T-cells lysed primary pediatric AML demonstrating the competence of the CBDC vaccine strategy

Prophylactic use of liposomal amphotericin B in children and adolescents undergoing allogeneic hematopoietic cell transplantation: A 10-years single center experience

Background: Azoles are recommended as antifungal prophylaxis in decreasing the incidence of invasive fungal disease (IFD) in high-risk patients in pediatric oncology, including patients receiving allogeneic hematopoietic cell transplantation (HCT). However, azole related toxicity, pharmacological interactions with immunosuppressive medication and conditioning regimen and growing incidence of azole resistance makes this antifungal agent not ideal in the transplant setting. This study reports on the contemporary incidence and outcome of IFD after allogeneic HCT in children with prophylactic liposomal amphotericin B (L-AMB). Methods: This single-center retrospective study included all patients transplanted between 2012 and 2022. Primary endpoint was the incidence of IFD until hospital discharge post-transplant. Secondary aims were the incidence of IFD and survival 180 days after allogeneic HCT, the evaluation of toxicity of L-AMB and further risk factors for development of IFD during antifungal prophylaxis. Descriptive statistics were performed. Results: 161 pediatric patients received L-AMB. Incidence of breakthrough IFD post-transplant was 7.5 % (12/161). The 12 cases comprised of three invasive yeast infections (1.9 %), three probable (1.9 %) and six possible (3.7 %) mold infections. Adverse events were in 22.4 % of the patients, most of them mild and reversible. Discontinuation of L-AMB occurred in 2.5 % (4/161) of the patients due to severe hypersensitivity reactions. Conclusions: The risk of breakthrough IFD in pediatric patients undergoing allogeneic HCT under L-AMB prophylaxis is comparable with the reported risk under first line recommendation drugs for antifungal prophylaxis. If no hypersensitivity reaction occurs, L-AMB is tolerated with manageable side effects. This antifungal agent should therefore be considered as an alternative option to azoles in pediatric allogeneic HCT recipients