A clinician’s guide to HLA matching in allogeneic hematopoietic stem cell transplant

Human leukocyte antigen (HLA) matching is an essential component of allogeneic hematopoietic stem cell transplant (HSCT). However, for some clinicians the biology underpinning HLA structure and function may be but a distant memory from lectures many years past, and, understanding the complexities of HLA matching can be challenging for clinicians new to the field, particularly as there have been several important advances in the field this past decade. In this review, we provide an up to date resource to educate and remind clinicians of: 1) Why HLA matching matters, including reviewing the role HLA molecules play in the adaptive immune system and the consequences of HLA mismatch. 2) What is involved in HLA matching, including a review of the different HLA genes, HLA protein structure, HLA sequencing approaches through time, and HLA allele nomenclature. And 3) how to apply this knowledge to identify an HLA matched donor for allogeneic HSCT, including discussion regarding HLA-DPB1 permissive mismatching and Donor Specific Antibodies.     

Epstein-Barr virus DNA load kinetics analysis in allogeneic hematopoietic stem cell transplant recipients: Is it of any clinical usefulness?

BackgroundThere is a lack of clinical information regarding the usefulness of plasma Epstein-Barr virus (EBV) DNA load kinetics analyses in the management of EBV infections in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Namely, it remains unknown whether this type of analysis can help physicians to anticipate the development of high-level EBV DNAemia episodes requiring rituximab treatment or predict the risk of recurrent EBV DNAemia or post-transplant lymphoproliferative disorders (PTLDs).Study designUnicentric, retrospective, observational study including 142 consecutive patients undergoing T-cell replete allo-HSCT. The plasma EBV DNA load was monitored on a weekly basis using the artus^® EBV PCR kit.ResultsFifty-five of the 142 patients (38.7%) developed at least one episode of EBV DNAemia; 13 of the 55 initial EBV DNAemia episodes (23.6%) were preemptively treated with rituximab, 7 patients had a recurrent episode of EBV DNAemia, and biopsy-proven PTLDs were diagnosed in 4 patients. The initial plasma EBV DNA load was not significantly different (P = 0.269) in episodes of self-resolving EBV DNAemia, those requiring rituximab treatment, or those leading to PTLDs. The plasma EBV DNA load doubling times were similar across all the groups (P = 0.799), and the EBV DNA-load half-life was not associated with the occurrence of recurrent EBV DNAemia (P = 0.550).ConclusionPlasma EBV DNA-load kinetics analyses are unlikely to be useful in predicting the occurrence of high-level EBV DNAemia, PTLD, or recurrent EBV DNAemia.     

Transforming growth factor-β1 polymorphisms and the outcome of hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is a medical procedure used to treat malignant and nonmalignant haematological diseases, congenital immunodeficiency syndromes, solid tumours and metabolic diseases. Despite its usefulness, several major complications, such as graft-versus-host disease, can negatively affect patients treated with HSCT. Apart from clinical factors well known to affect the outcome of HSCT, patient and donor genetics have been shown to play an important role in the susceptibility to post-transplant complications. Histocompatibility as determined by the human leucocyte antigen (HLA) system has been a major genetic determinant of the success of HSCT. Non-HLA immunogenetics are increasingly recognized to play a part in the events related to transplantation. Cytokine genes, and their receptors, bear a considerable amount of polymorphism. One of the genes that may play an important role on the outcome of allogeneic HSCT is TGFB1, which encodes transforming growth factor, βeta 1 (TGF-β1). TGF-β1 is a pleiotropic cytokine, which plays a central role in the development, homeostasis and responses of the immune system. Several functional polymorphisms in TGFB1 have been identified, and these are known to cause alterations in cytokine secretion in several settings. The present review will focus on the current knowledge surrounding the effect of polymorphisms within TGFB1 on the outcome of HSCT.     

2016 guideline strategies for the use of antifungal agents in patients with hematological malignancies or hematopoietic stem cell transplantation recipients in Taiwan

The Infectious Diseases Society of Taiwan (IDST), the Hematology Society of Taiwan, the Taiwan Society of Blood and Marrow Transplantation, Medical Foundation in Memory of Dr. Deh-Lin Cheng, Foundation of Professor Wei-Chuan Hsieh for Infectious Diseases Research and Education, and CY Lee's Research Foundation for Pediatric Infectious Diseases and Vaccines cooperatively published this guideline for the use of antifungal agents in hematological patients with invasive fungal diseases (IFDs) in Taiwan. The guideline is the first one endorsed by IDST focusing on selection of antifungal strategies, including prophylaxis, empirical (or symptom-driven) and pre-emptive (or diagnostic-driven) strategy. We suggest a risk-adapted dynamic strategy and provide an algorithm to facilitate decision making in population level as well as for individual patient. Risk assessment and management accordingly is explicitly emphasized. In addition, we highlight the importance of diagnosis in each antifungal strategy among five elements of the antimicrobial stewardship (diagnosis, drug, dose, de-escalation and duration). The rationale, purpose, and key recommendations for the choice of antifungal strategy are summarized, with concise review of international guidelines or recommendation, key original articles and local epidemiology reports. We point out the interaction and influence between elements of recommendations and limitation of and gap between evidences and daily practice. The guideline balances the quality of evidence and feasibility of recommendation in clinical practice. Finally, this version introduces the concept of health economics and provides data translated from local disease burdens. All these contents hopefully facilitate transparency and accountability in medical decision-making, improvements in clinical care and health outcomes, and appropriateness of medical resource allocation.     

KIR alloreactivity based on the receptor–ligand model is associated with improved clinical outcomes of allogeneic hematopoietic stem cell transplantation: Result of single center prospective study

Receptors on natural killer (NK) cells, named killer immunoglobulin-like receptors (KIRs), recognize HLA class I alleles. Patients (n = 59) who received allogeneic hematopoietic stem cell transplantation (HSCT) from either a related (n = 17) or unrelated donor (n = 42) in Samsung Medical Center (Seoul, South Korea) were included. KIR mismatch was defined as incompatibility between the donor KIR and recipient KIR ligand (receptor–ligand model), and all cases were classified into the two broad haplotypes of KIR A and B. Patients with acute leukemia (n = 51, 86.4%) or myelodysplastic syndrome (n = 8, 13.6%) were included. Peripheral blood was used as the source of stem cells in all patients. Kaplan–Meier survival curves for overall survival (OS), disease-free survival (DFS), and cumulative incidence of relapse (CIR) favored recipients with a KIR-mismatched donor, although the differences were not statistically significant. In multivariate analysis, KIR mismatch was an independent prognostic indicator of a better OS (P = 0.010, HR = 0.148, 95% CI 0.034–0.639), DFS (P = 0.022, HR = 0.237, 95% CI 0.069–0.815), and CIR (P = 0.031, HR = 0.117, 95% CI 0.017–0.823). OS, DFS, and CIR did not differ significantly between the KIR A and B haplotypes.     

Ambulatory management of sickle cell disease: evaluation of the first year follow up of patients in the pediatric department of Lomé (Togo)

BACKGROUND: This study is an evaluation of the first year ambulatory follow up of patients from the sickle-cell care centre of the paediatric ward of the teaching hospital in Lomé-Tokoin. PATIENTS AND METHODS: Togo is situated in the epicentre of the Benin haplotype. A total of 132 patients (109 SS, 22 SC and 1 S beta zero thal) followed up during one year from their admission date (period of 1st January 1996 to 31st December 1997). 132 patients were included in the study. RESULTS: The patients' age varied, for the majority, between 2 months and 15 years, but a few adults (15%) were included in the study. Information was collected from the hospital files and health cards, which unfortunately did not have specific entrees for sickle cell disease. Clinical features revealed that the frequency of tooth decay and chronic persistent splenomegaly was low when compared to the rates in central Africa (Bantu haplotype). Laboratory findings lead to the conclusion that some analysis are relevant such as the dosage of the G6PD activity (24.1% of patients were deficient), parasitologic analysis of faeces (positive in 22.5%), retinal fluoro-angiography (32.2% of ocular lesions), and cardiologic check-up. On the other hand, scanning of biliary tracts and systematic X-rays of the hips seems to be secondary. Some positive results were noticed by the scanning of biliary tracts without any therapeutic decisions in non-symptomatic patients; no case of osteonecrosis was detected by the X-rays. The mean haemoglobin level was 7.4 +/- 1.4 g/dl for the SS and 10.7 +/- 2.4 g/dl for the SC. The mean MCV were 91.3 +/- 10.1 fl and 82.1 +/- 7.7 fl, respectively. Specific vaccinations were not well performed because of their high cost. CONCLUSION: In order to carry on and improve the ambulatory management of patients with sickle cell disease, it is important in low income countries, such as Togo, to target the necessary laboratory tests for an initial and annual check-up. Solidarity networks for patients should be promoted and effective involvement of the health authorities ensured.     

Evolution of HLA testing for hematopoietic stem cell transplantation: Importance of the candidate’s antibody profile for donor selection

Hematopoietic Stem Cell Transplantation (HSCT) is a curative treatment for several malignant and non-malignant diseases. Access to this life saving therapy was limited by the requirement of an HLA matched donor. Introduction of platforms allowing transplantation with haploidentical and partially mismatched donors has enlarged the donor pool so that most candidates have a possible donor. HLA circulating antibodies specific for the donor’s mismatched antigens may cause delayed engraftment and primary graft failure. The role of the HLA laboratory supporting HSCT has expanded to provide HLA antibody detection and monitoring for selection of compatible donors and for monitoring of desensitization treatments. This review gives an outline of the evolution of HSCT and HLA and the current tools available to the HLA team to support donor selection and desensitization treatments in this new era of transplantation.     

Suppression of HLA expression by lentivirus-mediated gene transfer of siRNA cassettes and in vivo chemoselection to enhance hematopoietic stem cell transplantation

Current approaches for hematopoietic stem cell (HSC) and organ transplantation are limited by donor and host-mediated immune responses to allo-antigens. Application of these therapies is limited by the toxicity of preparative and post-transplant immunosuppressive regimens and a shortage of appropriate HLA-matched donors. We have been exploring two complementary approaches for genetically modifying donor cells that achieve long-term suppression of cellular proteins that elicit host immune responses to mismatched donor antigens, and provide a selective advantage to genetically engineered donor cells after transplantation. The first approach is based on recent advances that make feasible targeted down-regulation of HLA expression. Suppression of HLA expression could help to overcome limitations imposed by extensive HLA polymorphisms that restrict the availability of suitable donors. Accordingly, we have recently investigated whether knockdown of HLA by RNA interference (RNAi) enables allogeneic cells to evade immune recognition. For efficient and stable delivery of short hairpin-type RNAi constructs (shRNA), we employed lentivirus-based gene transfer vectors that integrate into genomic DNA, thereby permanently modifying transduced donor cells. Lentivirus-mediated delivery of shRNA targeting pan-Class I and allele-specific HLA achieved efficient and dose-dependent reduction in surface expression of HLA in human cells, and enhanced resistance to allo-reactive T lymphocyte-mediated cytotoxicity, while avoiding non-MHC restricted killing. Complementary strategies for genetic engineering of HSC that would provide a selective advantage for transplanted donor cells and enable successful engraftment with less toxic preparative and immunosuppressive regimens would increase the numbers of individuals to whom HLA suppression therapy could be offered. Our second strategy is to provide a mechanism for in vivo selection of genetically modified HSC and other donor cells. We have uniquely combined transplantation during the neonatal period, when tolerance may be more readily achieved, with a positive selection strategy for in vivo amplification of drug-resistant donor HSC. This model system enables the evaluation of mechanisms of tolerance induction to neo-antigens, and allogeneic stem cells during immune ontogeny. HSC are transduced ex vivo by lentivirus-mediated gene transfer of P140K-O⁶-methylguanine-methyltransferase (MGMT^P140K). The MGMT^P140K DNA repair enzyme confers resistance to benzylguanine, an inhibitor of endogenous MGMT, and to chloroethylating agents such as BCNU. In vivo chemoselection enables enrichment of donor cells at the stem cell level. Using complementary approaches of in vivo chemoselection and RNAi-induced silencing of HLA expression may enable the generation of histocompatibility-enhanced, and eventually, perhaps “universally” compatible cellular grafts.     

Parameters for establishing humanized mouse models to study human immunity: Analysis of human hematopoietic stem cell engraftment in three immunodeficient strains of mice bearing the IL2rγ mutation

“Humanized” mouse models created by engraftment of immunodeficient mice with human hematolymphoid cells or tissues are an emerging technology with broad appeal across multiple biomedical disciplines. However, investigators wishing to utilize humanized mice with engrafted functional human immune systems are faced with a myriad of variables to consider. In this study, we analyze HSC engraftment methodologies using three immunodeficient mouse strains harboring the IL2rγ^null mutation; NOD-scid IL2rγ^null, NOD-Rag1^null IL2rγ^null, and BALB/c-Rag1^null IL2rγ^null mice. Strategies compared engraftment of human HSC derived from umbilical cord blood following intravenous injection into adult mice and intracardiac and intrahepatic injection into newborn mice. We observed that newborn recipients exhibited enhanced engraftment as compared to adult recipients. Irrespective of the protocol or age of recipient, both immunodeficient NOD strains support enhanced hematopoietic cell engraftment as compared to the BALB/c strain. Our data define key parameters for establishing humanized mouse models to study human immunity.     

Active vaccination after allogeneic bone marrow cell transplantation: a new option in the immunotherapy of cancer?

The concept of immunotherapy of cancer was evoked more than a century ago by W. Coley. Yet it is only recently that the state of knowledge allows for molecularly defined therapeutic approaches and much effort will still be required to place immunotherapy beside of surgery, chemotherapy and radiation as a fourth option. In this review, we will focus chiefly on two aspects: active therapeutic vaccination, because it is our belief that this approach will provide a major breakthrough, and the potential efficacy of combining active vaccination with allogeneic bone marrow cell transplantation. It was recently established in clinical trials that allogeneic bone marrow cell transplantation does not require myeloablative conditioning. Non-myeloabaltive conditioning, which avoids the high toxicity of the conventional approach, it is only kind which allows the recruitment of elderly patients and patients in poor health. Concerning active vaccination protocols, we will address the questions 1) what the targets (i.e. the antigens) of immunotherapeutic approaches could be; 2) how to achieve an optimal confrontation of the immune system with these tumor-associated antigens; and 3) which response elements are needed for raising a therapeutically successful immune reaction against these antigens. Many question remain to be answered in the field of allogeneic bone marrow transplantation after non-myelablative conditioning to optimize the therapeutic setting for this, most likely, very powerful tool of cancer therapy. We will briefly summarize current considerations to improve engraftment, and reduce graft-versus-host disease while strengthening graft-versus-tumor reactivity. There is some hope that the latter can be "naturally" maintained during the process of T cell maturation in the allogeneic host. Provided this hypothesis can be substantiated, the efficacy of active vaccination of the allogeneically reconstituted host will provide a pool of virgin T cells which are tolerant towards the host, but not anergized towards tumor antigens presented by MHC molecules of the host. We will only briefly mention supportive regimen of immunomodulation and those hazards which one is most frequently confronted with in attempts to attack tumors with the inherent weapon of immune defense. Though the successful immunotherapy of cancer still remains far behind expectations, there is a solid basis for the belief that, by improving our understanding of the molecular mechanisms of immunity, this may become a very powerful and less harmful tool than conventional therapies.     

Ultrastructural findings of cutaneous nerves in patients with Hunter’s syndrome following hematopoietic stem cell transplant

Hematopoietic stem cell transplant (HSCT) has been performed on patients with Hunters syndrome. If applied, evaluation of recovery in various organs is needed for long-term follow-up. However, it remains unclear whether HSCT is effective against the neurological involvement in Hunters syndrome, and morphological evaluation of recovery is inconsistent. We observed the degree of cutaneous nerve involvement in patients with Hunters syndrome ultrastructurally before and after HSCT. Electron microscopic studies revealed that membrane-bound clear vacuoles were still observed in the cytoplasm of endoneurial fibroblasts and Schwann cells 2 months and 2 years, respectively, after HSCT. On the other hand, only a few vacuoles were present in dermal fibroblasts at 2 months after HSCT, and these disappeared within 2 years. These results suggest that the persistence of clear vacuoles in endoneurial fibroblasts and Schwann cells indicates a disturbed internal condition in the endoneurium 2 years after HSCT. Skin biopsies can be used in patients with Hunters syndrome to study peripheral nerves for long-term follow-up to evaluate morphological efficacy.     

The effect of HLA allele and haplotype polymorphisms on donor matching in hematopoietic stem cell transplantation – Croatian experience

The knowledge of HLA characteristics of a patient’s population helps to predict the probability of finding a MUD.The study included 170 transplanted patients for whom a search for a MUD in BMDW was performed and a sample of 4000 volunteer unrelated donors from the Croatian Bone Marrow Donor Registry (CBMDR). Patients and their MUDs were typed for HLA-A, -B, -C, -DRB1, and -DQB1 loci using PCR-SSO and PCR-SSP methods while donors were typed for HLA-A, -B, -C, and -DRB1 loci using the PCR-SSO method.A comparison of allele frequencies at tested HLA loci between patients and donors from CBMDR did not reveal significant differences. The majority of patients (117, 68.8%) had a 10/10 MUD, 45 (26.5%) patients had a 9/10 MUD and eight (4.7%) patients had an 8/10 MUD. The highest number of mismatches (MM) was present at HLA-DRB1 (19; 31.1%). The presence of DRB1*11 and DRB1*04 allelic groups among patients caused allelic MMs at HLA-DRB1 in most cases. The presence of an infrequent HLA-B∼C haplotype resulted in the HLA-C MM at antigen level in the majority of cases.The present study clarified HLA factors that cause difficulties in searching for a 10/10 MUD for Croatian patients.     

Late relapse of primary hemophagocytic lymphohistiocytosis after hematopoietic stem cell transplantation: a consequence of low-level chimerism from a carrier donor?

Immunologic Research -     

Haematopoietic stem cell transplantation and gene therapy in the fetus: ready for clinical use?

Allogeneic haematopoietic stem cell transplantation in utero has been successfully used for the prenatal treatment of severe combined immunodefiency syndrome. However, this treatment has not been successful in the therapy of other conditions in which the fetus is immunologically competent. The main obstacles to success are lack of competitive advantage of donor versus host stem cells, preventing stable engraftment and graft rejection. Several strategies are being explored to overcome these problems, and some of them have been successful in animal studies. Prenatal gene therapy, using ex-vivo transduced autologous haematopoietic cells or direct gene targeting in utero, is another potential approach in the treatment of immunocompetent fetal recipients. Although this has been shown to be feasible in animal models, safety concerns regarding transduction of fetal germ cells or maternal cells should be addressed in preclinical experiments prior to initiation of clinical trials.     

Complications and death causes of peripheral blood stem cell transplantation in the treatment of thalassemia major北大核心

BACKGROUND: Allogeneic hematopoietic stem cell transplantation is the only effective method to cure thalassemia major. However, the risk factors influencing the prognosis of transplantation remain unclear. OBJECTIVE: To analyze the distribution of common complications and cause of death after allogeneic hematopoietic stem cell transplantation in children with thalassemia major, and to explore the prognostic factors so as to provide references for improving the survival rate of patients. METHODS: This retrospective cohort study included 257 patients with β-thalassemia major who underwent allogeneic hematopoietic stem cell transplantation at Department of Hematology and Oncology, Guangzhou Women and Children Medical Center between September 2013 and September 2019. There were 172 males and 85 females, with a median age of 6 years at the time of transplantation. The basic clinical data before transplantation and complications after transplantation were compared between the surviving group and dead group using single factor. The overall survival rate was analyzed by the Kaplan-Meier method, and the overall survival rate was compared by the Log-rank test. Multivariate Cox regression was used to analyze factors affecting survival. RESULTS AND CONCLUSION: The median follow-up time was 29 months, and no cases were lost to follow-up. (1) Univariate analysis results showed that there were significant differences in the risk classification between surviving patients and dead patients (P=0.033). Patients with higher risk class had an increased risk of death after transplantation. Multivariate analysis showed that risk classification and severe pneumonia were independent risk factors for overall survival after thalassemia major hematopoietic stem cell transplantation (P < 0.05). (2) Among 20 dead patients, there were 13 patients with severe pneumonia and respiratory failure, 2 patients with grade IV intestinal graft-versus-host disease, 1 patient with intracranial hemorrhage due to thrombocytopenia, 1 patient with thrombocytopenia with acute pulmonary hemorrhage, 1 patient with sepsis with shock, and 1 patient with myasthenia gravis. (3) Totally 17 cases died within 1 year after transplantation, while the rest 3 patients died of severe pneumonia more than 1 year after transplantation. (4) The incidence of bronchiolitis obliterans was significantly higher in patients who died after transplantation than in those who survived (P < 0.000 1). (5) It is concluded that the important factors that affect survival rate in thalassemia major patients after hematopoietic stem cell transplantation are infection and severe graft-versus-host disease. The risk of death increased in patients with bronchiolitis obliterans after transplantation. © 2023, Chinese Journal of Tissue Engineering Research. All rights reserved.     

Safety of hematopoietic stem cell transplantation from hepatitis B core antibodies-positive donors with low/undetectable viremia in HBV-naïve children

Scarce data exist on allogeneic hematopoietic stem cell transplantation (HSCT) outcomes in hepatitis B virus (HBV)-naïve recipients from HBV-experienced donors. Long-term follow-up is herein reported for 17 allogeneic HSCT performed in 13 HBV-naïve children from HBc-antibodies-positive donors between 2006 and 2012. Four donors were HBs-antigen-positive, with detectable but low viremia in 2 cases (<2 log₁₀IU/ml). HBV-DNA was undetectable in all transplanted cell products. Recipients’ HBV prophylaxis consisted of pre-transplant vaccination, polyvalent immune globulins, specific anti-HBV immune globulins, and/or oral lamivudine in 3, 12, 8, and 8 children, respectively. No case of HBV transmission occurred based on negative close monitoring of recipients’ HBV serology and plasma HBV-DNA during a median follow-up of 22 months. In case of undetectable viremia in the donor, prophylaxis with vaccination and/or immune globulins in the recipient seems to be sufficient and lamivudine prophylaxis might be unnecessary to prevent viral transmission. In case of undetectable viremia in the donor, a systematic screening of HBV DNA in the stem cell product might be unnecessary to confirm the low risk of viral transmission. Prior exposure to HBV in the donor should not be considered a contraindication to HSCT.