HLA disparity is not crucial for the survival rate and severity of chronic health conditions in adult recipients following family donor hematopoietic stem cell transplantation

HLA Matching in Pediatric Stem Cell Transplantation

For several malignant and nonmalignant disorders such as leukemias, lymphomas, or inborn errors of hematopoiesis, stem cell transplantation is the only curative option. Depending on the underlying cause of the disease, the conditioning regimens, source of the stem cells, and graft composition may vary. Possible stem cell donors are selected from databases considering existing major histocompatibility genes of the donor and the recipient. This is currently performed by matching human leukocyte antigen (HLA)-A, -B, and -C for class I, as well as HLA-DRB1 and -DQB1 for class II. Stem cell transplantation for nonmalignant disorders is a specialty of pediatrics. While algorithms for donor selection in these cases are generally similar, the objective of optimizing a possible graft-versus-leukemia effect is less important. In this article, we aim to provide an overview on the current methods for HLA typing and the algorithms for HLA matching. We also address ethical aspects regarding children and minors as stem cell donors.

Evaluation of HistoCheck as a Predictor of Clinical Outcomes after Haploidentical Hematopoietic Stem Cell Transplantation

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is available for nearly all patients without matching HLA-related or -unrelated donors. There was not a valid evaluation system to predict the most proper donor. HistoCheck was based on the functional similarity of amino acids to estimate the allogenicity of HLA mismatches with a sequence similarity matching (SSM) score. We investigated whether HistoCheck could predict clinical outcomes in 500 patients with acute leukemia or myelodysplastic syndrome receiving haplo-HSCT. The total SSM score of the 5 loci (HLA-A, -B, -C, -DRB1, and -DQB1) had no association with clinical outcomes. HLA-C SSM score was significantly associated with transplant-related mortality (TRM) (hazard ratio [HR], .in691; 95% confidence interval [CI], .520 to .917; P = .011), disease-free survival (DFS) (HR, .714; 95% CI, .586 to .869; P = .001), and overall survival (OS) (HR, .711; 95% CI, .574 to .881; P = .002) by multivariate analysis. No significant associations were observed between other single-locus SSM score and clinical outcomes. In summary, our data demonstrate that a high HLA-C HistoCheck SSM score may lead to lower TRM and improved DFS and OS after haplo-HSCT and inclusion of HLA-C HistoCheck in donor selection criteria may need to be further confirmed in prospective studies.

Update on current research into haploidentical hematopoietic stem cell transplantation

INTRODUCTION

Haploidentical stem cell transplantation (Haplo-SCT) is currently a suitable alternative worldwide for patients with hematological diseases, who lack human leukocyte antigen (HLA)-matched siblings or unrelated donors. Areas covered: This review summarizes the advancements in Haplo-SCT in recent years, primarily focusing on the global trends of haploidentical allograft, the comparison of outcomes between Haplo-SCT and other transplantation modalities, strategies for improving clinical outcomes, including donor selection, hematopoietic reconstitution promotion, and graft-versus-host disease, and relapse prevention/management, as well as the expanded indications of Haplo-SCT, such as severe aplastic anemia, myeloma and lymphoma. Expert commentary: Haploidentical allografts, including granulocyte colony-stimulating factor-based protocol and a post-transplant cyclophosphamide-based protocol, have been the mainstream strategy for Haplo-SCT. However, there are many unanswered questions in this field.

Impact of HLA allele mismatch at HLA-A, -B, -C, -DRB1, and -DQB1 on outcomes in haploidentical stem cell transplantation

The impact of human leukocyte antigen (HLA) allele mismatch on transplant outcomes in haploidentical stem cell transplantation (haplo-SCT) has not been established. We retrospectively studied 595 patients with hematologic malignancy who received haplo-SCT. The impact of multiple HLA allele mismatches (HLA-A, -B, -C, -DRB1, and -DQB1) and each HLA allele mismatch on transplant outcomes was analyzed. Greater number of HLA allele disparity does not appear worsen outcome. As for each HLA locus, HLA-A mismatch correlated with decreased rate of platelet engraftment (HR 0.740, P = .003); HLA-B mismatch independently correlated with decreased relapse rate (HR 0.494, P = .032) and improved disease-free survival and overall survival (HR 0.514, P = .003; HR 0.494, P = .002, respectively); HLA-C mismatch appeared to be protective for transplant-related mortality (TRM) (HR 0.567, P = .039); HLA-DRB1 mismatch was associated with increased cumulative incidence of grade II-IV acute graft-vs.-host disease (GVHD) (HR 1.942, P = .002). No associations of any HLA mismatch with delayed neutrophil engraftment or increased cumulative incidence of chronic GVHD were observed. Our data indicated that high degree of HLA allele mismatches did not adversely affect transplant outcomes in haplo-SCT and each HLA allele mismatch had different effect.

Predicted indirectly recognizable HLA epitopes are not associated with clinical outcomes after haploidentical hematopoietic stem cell transplantation

Haploidentical stem cell transplantation (haplo-SCT) provides an alternative method to cure patients with malignant and nonmalignant hematologic diseases who lack a human leukocyte antigen (HLA) matched related or unrelated donor. HLA disparity between donor and patient was the main reason causing lots of clinical immune response. The aim of this study was to investigate whether indirect recognition of mismatched HLA could predict the clinical outcomes in haplo-SCT. The probability of indirect recognition was predicted by the Predicted Indirectly ReCognizable HLA Epitopes (PIRCHE) model. 577 patients with acute leukemia or myelodysplastic syndrome receiving haplo-SCT were enrolled in the study. Patients were divided into 4 quartiles according to PIRCHE-Ⅰ or PIRCHE-Ⅱ. Although the cumulative incidences of chronic graft-versus-host disease (GVHD) were significantly different among the 4 PIRCHE-Ⅰgroups, with 20.4% for group 0-6, 40.5% for group >6-11, 26.1% for group >11-19 and 23.9% for group >19 (P = .007), PIRCHE-Ⅰ was not significantly associated with chronic GVHD in multivariate models (RR, 0.993; 95% CI, 0.858-1.149; P = .926). And no significant associations were observed between PIRCHE-Ⅰ or PIRCHE-Ⅱ and other clinical outcomes. In summary, PIRCHE did not correlate with clinical outcomes and could not predict haplo-SCT outcomes.

How do we choose the best donor for T-cell-replete, HLA-haploidentical transplantation?

In haploidentical stem cell transplantations (haplo-SCT), nearly all patients have more than one donor. A key issue in the haplo-SCT setting is the search for the best donor, because donor selection can significantly impact the incidences of acute and chronic graft-versus-host disease, transplant-related mortality, and relapse, in addition to overall survival. In this review, we focused on factors associated with transplant outcomes following unmanipulated haplo-SCT with anti-thymocyte globulin (ATG) or after T-cell-replete haplo-SCT with post-transplantation cyclophosphamide (PT/Cy). We summarized the effects of the primary factors, including donor-specific antibodies against human leukocyte antigens (HLA); donor age and gender; killer immunoglobulin-like receptor-ligand mismatches; and non-inherited maternal antigen mismatches. We also offered some expert recommendations and proposed an algorithm for selecting donors for unmanipulated haplo-SCT with ATG and for T-cell-replete haplo-SCT with PT/Cy.

Fighting against hematological malignancy in China: from unique system to global impact

During recent decades, substantial progress has been made in clinical strategies for treating hematological malignancies. Not only did China benefit from the global progression in the management of acute promyelocytic leukemia, risk-stratification-directed strategies for acute or chronic leukemia and haploidentical hematopoietic stem cell transplantation, the unique system developed by Chinese doctors has also become inspiration for refining global clinical practice. The multicenter trials and collaborations adhering to international standards might further strengthen the global impact and lead the way in specific fields of research worldwide.