How important is NK alloreactivity and KIR in allogeneic transplantation?

Reconstitution of Natural Killer cells after allogeneic hematopoietic stem cell transplantation is facilitated by Huiyang-Guben decoction through activating the Smad7/Stat3 signal pathway

Natural Killer (NK) cell is the first batch of re-constructed cell populations after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and its delayed reconstitution inevitably causes poor outcome. The traditional Chinese medicine Huiyang-Guben decoction (HYGB) has been clinically used in patients undergoing allo-HSCT, but its effect on NK cell reconstruction is still unclear. 40 patients with allo-HSCT therapy were randomly divided into the control group and the HYGB group, and were given oral administration of normal saline or HYGB for 4 weeks before allo-HSCT, respectively. NK cells were cultured and treated with transforming growth factor β (TGF-β) and HYGB in vitro, and cell viability, cell apoptosis, and the function of NK cells were evaluated. Functional verification experiments were performed by knocking down signal transduction molecule 7 (Smad7) in NK cells before TGF-β and HYGB treatment. Clinical data suggested that HYGB intervention decreased the incidence of acute graft-versus-host disease after allo-HSCT, and increased the proportion of NK cell population. Meanwhile, HYGB improved cell viability, restrained apoptotic cell death, and enhanced cell killing activity of NK cells in patients with allo-HSCT. Notably, we found that HYGB significantly increased the expression level of Smad7 and the phosphorylation level of signal transducer and activator of transcription 3 (Stat3) in NK cells from patients with allo-HSCT. Moreover, HYGB alleviated TGF-β-induced NK cell impairment and re-activated the Smad7/Stat3 signaling in vitro, while silencing Smad7 reversed the protective effect of HYGB on TGF-β-treated NK cells. HYGB promotes NK cell reconstruction and improves NK cell function after allo-HSCT through activating the Smad7/Stat3 signaling pathway.

Impact of Natural Killer Cell-Associated Factors on Acute Leukemia Outcomes after Haploidentical Hematopoietic Stem Cell Transplantation with αβ T Cell Depletion in a Pediatric Cohort

The technique of αβ T cell depletion (αβTCD) is a well-established method of hematopoietic stem cell transplantation (HSCT) for children with acute leukemia owing to the low rates of graft-versus-host disease and nonrelapse mortality (NRM). The graft-versus-leukemia effect is generally ascribed to natural killer (NK) cells conserved within the graft. It is not known whether NK-related factors affect the outcome of αβTCD HSCT, however. The aim of this retrospective study was to explore the impact of NK alloreactivity (based on donor-recipient killer immunoglobulin-like receptor [KIR] mismatch), graft NK cell dose, and blood NK cell recovery on day +30 post-HSCT on the incidences of leukemia relapse and NRM. The pediatric acute leukemia cohort comprised 295 patients who underwent their first HSCT from a haploidentical donor in complete remission. During post hoc analysis, the total cohort was divided into subcohorts by diagnosis (acute lymphoblastic leukemia [ALL]/acute myeloid leukemia [AML]), NK alloreactivity prediction (KIR match/KIR mismatch), graft NK cell dose (less than versus greater than the median value), and blood NK cell recovery on day +30 post-HSCT (less than versus greater than the median value). We also investigated the influence of serotherapy (antithymocyte globulin [ATG] group) versus abatacept + tocilizumab combination [aba+toci] group) on relapse risk in the context of KIR mismatch. The risks of relapse and NRM were calculated by the cumulative risk method, and groups were compared using the Gray test. Multivariate analysis revealed no apparent impact of predicted NK alloreactivity or any other studied NK cell-related factors for the entire cohort. For patients with AML, a significantly higher relapse risk associated with high NK cell graft content on the background of no predicted KIR mismatch (P = .002) was shown. Multivariate analysis confirmed this finding (P = .018); on the other hand, for the KIR-mismatched patients, there was a trend toward a lower risk of relapse associated with high NK cell dose. The use of ATG was associated with a trend toward reduced relapse risk (P = .074) in the AML patients. There was no significant impact of NK-related factors in the ALL patients. Overall, the evaluated NK-related factors did not show a clear and straightforward correlation with the key outcomes of HSCT in our cohort of children with acute leukemia. In practice, the data support prioritization of KIR-mismatched donors for patients with AML. Importantly, a potential interaction of KIR ligand mismatch and NK cell content in the graft was identified. Indirect evidence suggests that additional cellular constituents of the graft could influence the function of NK cells after HSCT and affect their role as graft-versus-leukemia effectors.

Graft versus Leukemia in 2023

Allogeneic hematopoietic stem cell transplantation (HSCT) is commonly utilized in the management of leukemia across multiple subtypes. Graft versus leukemia (GVL) is a critical component of successful transplantation and involves donor cells eradicating residual leukemia within the recipient. Graft versus host disease (GVHD) by contrast is a common complication of the transplantation process in which donor cells identify the recipient's various organ systems as foreign, thereby leading to a multitude of organ toxicities that can be described as autoimmune in nature. As both GVL and GVHD are mediated by a similar mechanism, these processes are felt to occur in tandem with one another. Here, we review the allogeneic HCT process in the context of GVL.

The Role of NK Cells and Their Exosomes in Graft Versus Host Disease and Graft Versus Leukemia

Natural killer (NK) cells are one of the innate immune cells that play an important role in preventing and controlling tumors and viral diseases, but their role in hematopoietic stem cell transplantation (HCT) is not yet fully understood. However, according to some research, these cells can prevent infections and tumor relapse without causing graft versus host disease (GVHD). In addition to NK cells, several studies are about the anti-leukemia effects of NK cell-derived exosomes that can highlight their roles in graft-versus-leukemia (GVL). In this paper, we intend to investigate the results of various articles on the role of NK cells in allogeneic hematopoietic cell transplantation and also their exosomes in GVL. Also, we have discussed the antiviral effects of these cells in post-HCT cytomegalovirus infection.

High-resolution human KIR genotyping

Killer immunoglobulin-like receptors (KIR) regulate the function of natural killer cells through interactions with various ligands on the surface of cells, thereby determining whether natural killer (NK) cells are to be activated or inhibited from killing the cell being interrogated. The genes encoding these proteins display extensive variation through variable gene content, copy number and allele polymorphism. The combination of KIR genes and their ligands is implicated in various clinical settings including haematopoietic stem cell and solid organ transplant and infectious disease progression. The determination of KIR genes has been used as a factor in the selection of optimal stem cell donors with haplotype variations in recipient and donor giving differential clinical outcomes. Methods to determine KIR genes have primarily involved ascertaining the presence or absence of genes in an individual. With the more recent introduction of massively parallel clonal next-generation sequencing and single molecule very long read length third-generation sequencing, high-resolution determination of KIR alleles has become feasible. Determining the extent and functional impact of allele variation has the potential to lead to further optimisation of clinical outcomes as well as a deeper understanding of the functional properties of the receptors and their interactions with ligands. This review summarizes recently published high-resolution KIR genotyping methods and considers the various advantages and disadvantages of the approaches taken. In addition the application of allele level genotyping in the setting of transplantation and infectious disease control is discussed.

Optimizing Blood Stem Cell Transplants Through Cellular Engineering

Haematopoietic stem cell transplants (HSCT) are used in the treatment of blood cancers, autoimmune diseases, and metabolic disorders. Over 1.5 million transplants have been performed around the world thus far. In an attempt to enhance the efficacy of the cells used for transplantation, efforts are underway to use cellular engineering to increase cell numbers through: (1) the expansion of hematopoietic stem and progenitor cells (HSPC); (2) cellular subset selection to remove cells that cause graft-versus-host disease (GvHD), while adding back cells, which can mediate anti-tumor and anti-viral immunity; (3) the use of immune regulatory cells, such as mesenchymal stromal cells (MSC) and regulatory T cells (Tregs) to control GvHD; (4) the use of immune effector cells to mount immunological control of tumor cells before, after, or independent of blood stem cell transplants.

OMIP-080: 29-Color flow cytometry panel for comprehensive evaluation of NK and T cells reconstitution after hematopoietic stem cells transplantation

This 29-color panel was developed and optimized for the monitoring of NK cell and T cell reconstitution in peripheral blood of patients after HSCT. We considered major post-HSCT complications during the design, such as relapses, viral infections, and GvHD and identification of lymphocyte populations relevant to their resolution. The panel includes markers for all major NK cell and T cell subsets and analysis of their development and qualitative properties. In the NK cell compartment, we focus mainly on CD57 + NKG2C+ cells and the expression of activating (NKG2D, DNAM-1) and inhibitory receptors (NKG2A, TIGIT). Another priority is the characterization of T cell reconstitution; therefore, we included detection of CD4+ RTEs based on CD45RA, CD62L, CD95, and CD31 as a marker of thymus function. Besides that, we also analyze the emergence and properties of major T cell populations with a particular interest in CD8, Th1, ThCTL, and Treg subsets. Overall, the panel allows for comprehensive analysis of the reconstituting immune system and identification of potential markers of immune cell dysfunction.

Influence of Killer Immunoglobulin-Like Receptors and Somatic Mutations on Transplant Outcomes in Acute Myeloid Leukemia

Natural killer (NK) cells are regulated by killer immunoglobulin-like receptor (KIR) interactions with human leukocyte antigen class I ligands. Various models of NK cell alloreactivity have been associated with outcomes after allogeneic hematopoietic cell transplant (alloHCT), but results have varied widely. We hypothesized that somatic mutations in acute myeloid leukemia (AML) in the context of KIR profiles may further refine their association with transplant outcomes. In this single-center, retrospective, observational study, 81 AML patients who underwent matched-related donor alloHCT were included. Post-HCT outcomes were assessed based on mutational status and KIR profiles with the Kaplan-Meier method and log-rank test. On multivariable analysis those with any somatic mutations and C1/C2 heterozygosity had less acute graft-versus-host disease (GvHD) (hazard ratio [HR], 0.32; 95% confidence interval [CI], 0.14-0.75; P = .009), more relapse (HR, 3.02; 95% CI, 1.30-7.01; P = .010), inferior relapse-free survival (RFS; (HR, 2.22; 95% CI, 1.17-4.20; P = .014), and overall survival (OS; HR, 2.21; 95% CI, 1.17-4.20; P = .015), whereas those with a missing KIR ligand had superior RFS (HR, 0.53; 95% CI, 0.30-0.94; P = .031). The presence of a somatic mutation and donor haplotype A was also associated with less acute GvHD (HR, 0.38; 95% CI, 0.16-0.92; P = .032), more relapse (HR, 2.72; 95% CI, 1.13-6.52; P = .025), inferior RFS (HR, 2.11; 95% CI, 1.07-4.14; P = .030), and OS (HR, 2.20; 95% CI, 1.11-4.38; P = .024). Enhanced NK cell alloreactivity from more KIR activating signals (donor B haplotype) and fewer inhibitory signals (recipient missing KIR ligand or C1 or C2 homozygosity) may help mitigate the adverse prognosis associated with some AML somatic mutations. These results may have implications for improving patient risk stratification prior to transplant and optimizing donor selection.

Immune Reconstitution-Based Score for Risk Stratification of Chronic Graft-Versus-Host Disease Patients

Introduction

Allogeneic stem cell transplantation survivors are at a relevant risk of developing chronic GvHD (cGvHD), which importantly affects quality of life and increases morbidity and mortality. Early identification of patients at risk of cGvHD-related morbidity could represent a relevant tool to tailor preventive strategies. The aim of this study was to evaluate the prognostic power of immune reconstitution (IR) at cGvHD onset through an IR-based score.

Methods

We analyzed data from 411 adult patients consecutively transplanted between January 2011 and December 2016 at our Institution: 151 patients developed cGvHD (median follow-up 4 years). A first set of 111 consecutive patients with cGvHD entered the test cohort while an additional consecutive 40 patients represented the validation cohort. A Cox multivariate model for OS (overall survival) in patients with cGvHD of any severity allowed the identification of six variables independently predicting OS and TRM (transplant-related mortality). A formula for a prognostic risk index using the β coefficients derived from the model was designed. Each patient was assigned a score defining three groups of risk (low, intermediate, and high).

Results

Our multivariate model defined the variables independently predicting OS at cGvHD onset: CD4+ >233 cells/mm³, NK <115 cells/mm³, IgA <0.43g/L, IgM <0.45g/L, Karnofsky PS <80%, platelets <100x10³/mm³. Low-risk patients were defined as having a score ≤3.09, intermediate-risk patients >3.09 and ≤6.9, and high-risk patients >6.9. By ROC analysis, we identified a cut-off of 6.310 for both TRM and overall mortality.

In the training cohort, the 6-year OS and TRM from cGvHD occurrence were 85% (95% CI, 70-92) and 13% (95% CI, 5-25) for low-risk, 64% (95% CI, 44-89) and 30% (95% CI, 15-47) for intermediate-risk, 26% (95% CI, 10-47), and 42% (95% CI, 19-63) for high-risk patients (OS p<0.0001; TRM p = 0.015).

The validation cohort confirmed the model with a 6-year OS and TRM of 83% (95% CI, 48-96) and 8% (95% CI, 1-32) for low-risk, 78% (95% CI, 37-94) and 11% (95% CI, 1-41) for intermediate-risk, 37% (95% CI, 17-58), and 63% (95% CI, 36-81) for high-risk patients (OS p = 0.0075; TRM p = 0.0009).

Conclusions

IR score at diagnosis of cGvHD predicts GvHD severity and overall survival. IR score may contribute to the risk stratification of patients. If confirmed in a larger and multicenter-based study, IR score could be adopted to identify patients at high risk and modulate cGvHD treatments accordingly in the context of clinical trial.

Realizing Innate Potential: CAR-NK Cell Therapies for Acute Myeloid Leukemia

Next-generation cellular immunotherapies seek to improve the safety and efficacy of approved CD19 chimeric antigen receptor (CAR) T-cell products or apply their principles across a growing list of targets and diseases. Supported by promising early clinical experiences, CAR modified natural killer (CAR-NK) cell therapies represent a complementary and potentially off-the-shelf, allogeneic solution. While acute myeloid leukemia (AML) represents an intuitive disease in which to investigate CAR based immunotherapies, key biological differences to B-cell malignancies have complicated progress to date. As CAR-T cell trials treating AML are growing in number, several CAR-NK cell approaches are also in development. In this review we explore why CAR-NK cell therapies may be particularly suited to the treatment of AML. First, we examine the established role NK cells play in AML biology and the existing anti-leukemic activity of NK cell adoptive transfer. Next, we appraise potential AML target antigens and consider common and unique challenges posed relative to treating B-cell malignancies. We summarize the current landscape of CAR-NK development in AML, and potential targets to augment CAR-NK cell therapies pharmacologically and through genetic engineering. Finally, we consider the broader landscape of competing immunotherapeutic approaches to AML treatment. In doing so we evaluate the innate potential, status and remaining barriers for CAR-NK based AML immunotherapy.

An Unconventional View of T Cell Reconstitution After Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) is performed as curative-intent therapy for hematologic malignancies and non-malignant hematologic, immunological and metabolic disorders, however, its broader implementation is limited by high rates of transplantation-related complications and a 2-year mortality that approaches 50%. Robust reconstitution of a functioning innate and adaptive immune system is a critical contributor to good long-term patient outcomes, primarily to prevent and overcome post-transplantation infectious complications and ensure adequate graft-versus-leukemia effects. There is increasing evidence that unconventional T cells may have an important immunomodulatory role after allo-HCT, which may be at least partially dependent on the post-transplantation intestinal microbiome. Here we discuss the role of immune reconstitution in allo-HCT outcome, focusing on unconventional T cells, specifically mucosal-associated invariant T (MAIT) cells, γδ (gd) T cells, and invariant NK T (iNKT) cells. We provide an overview of the mechanistic preclinical and associative clinical studies that have been performed. We also discuss the emerging role of the intestinal microbiome with regard to hematopoietic function and overall immune reconstitution.

Immune Reconstitution after Haploidentical Donor and Umbilical Cord Blood Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (HCT) is the only potentially curative therapy for a variety of hematologic diseases. However, this therapeutic platform is limited by an initial period when patients are profoundly immunocompromised. There is gradual immune recovery over time, that varies by transplant platform. Here, we review immune reconstitution after allogeneic HCT with a specific focus on two alternative donor platforms that have dramatically improved access to allogeneic HCT for patients who lack an HLA-matched related or unrelated donor: haploidentical and umbilical cord blood HCT. Despite challenges, interventions are available to mitigate the risks during the immunocompromised period including antimicrobial prophylaxis, modified immune suppression strategies, graft manipulation, and emerging adoptive cell therapies. Such interventions can improve the potential for long-term overall survival after allogeneic HCT.

Harnessing Natural Killer Cell Antitumor Immunity: From the Bench to Bedside

Natural killer (NK) cells are critical effector lymphocytes mediating tumor immune surveillance and clearance. They do so by direct tumor killing using cytolytic granules and death receptors, and by interfacing with and potentiating adaptive immune responses through the production of cytokines. From a therapeutic perspective, NK cells have been shown to exert graft-versus-leukemia activity in the context of hematopoietic stem cell transplantation and are important in the clinical efficacy of antibodies. Advances in basic and translational NK cell biology have led to multiple potential strategies to augment their in vivo activity to improve antitumor responses. Despite their potent effects, NK cells have been shown to be safe for adoptive cell therapy in both the autologous and allogeneic settings, with promising, but so far limited, clinical efficacy. This review will provide an overview of strategies being pursued to improve NK cell activity and efficacy, focusing on cell source, NK cell activation, and in vivo persistence.

Dissecting the biology of allogeneic HSCT to enhance the GvT effect whilst minimizing GvHD

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) was the first successful therapy for patients with haematological malignancies, predominantly owing to graft-versus-tumour (GvT) effects. Dramatic methodological changes, designed to expand eligibility for allo-HSCT to older patients and/or those with comorbidities, have led to the use of reduced-intensity conditioning regimens, in parallel with more aggressive immunosuppression to better control graft-versus-host disease (GvHD). Consequently, disease relapse has become the major cause of death following allo-HSCT. Hence, the prevention and treatment of relapse has come to the forefront and remains an unmet medical need. Despite >60 years of preclinical and clinical studies, the immunological requirements necessary to achieve GvT effects without promoting GvHD have not been fully established. Herein, we review learnings from preclinical modelling and clinical studies relating to the GvT effect, focusing on mechanisms of relapse and on immunomodulatory strategies that are being developed to overcome disease recurrence after both allo-HSCT and autologous HSCT. Emphasis is placed on discussing current knowledge and approaches predicated on the use of cell therapies, cytokines to augment immune responses and dual-purpose antibody therapies or other pharmacological agents that can control GvHD whilst simultaneously targeting cancer cells.

Recent progress in and challenges in cellular therapy using NK cells for hematological malignancies

NK cells have killing activity against leukemic cells and solid cancer cells that escape from T cell recognition because of the low expression level of HLA class I molecules. This characteristic feature of NK cell recognition of target cells in contrast to T cells provides a strategy to overcome tolerance in cancer and leukemia patients. A strong alloreactive NK cell-mediated anti-leukemia effect can be induced in haploidentical hematopoietic stem cell transplantation. Also, NK cells can be expanded by several methods for adoptive immunotherapy for hematological malignancies and other malignant diseases. We review the historical role of NK cells and recent approaches to enhance the functions of NK cells, including ex vivo expansion of autologous and allogenic NK cells, checkpoint receptor blockade, and the use of memory-like NK cells and CAR-NK cells, for treatment of hematological malignancies.

Influence of Preformed Antibodies in Liver Transplantation

The significance of human leukocyte antigen (HLA) matching and preformed donor-specific antibodies (DSAs) in liver transplantation remains unclear. The aim of this study was to analyze the presence of DSAs in a large cohort of 810 liver recipients undergoing liver transplant to determine the influence on acute (AR) or chronic liver rejection (CR), graft loss and allograft survival. DSAs were identified using complement dependent cytotoxicity crossmatch (CDC-CM) and multiplexed solid-phase-based flow cytometry assay (Luminex). CDC-CM showed that a 3.2% of liver transplants were positive (+CDC-CM) with an AR frequency of 19.2% which was not different from that observed in negative patients (-CDC-CM, 22.3%). Only two patients transplanted with +CDC-CM (7.6%) developed CR and suffered re-transplant. +CDC-CM patients showed a significantly lower survival rate compared to -CDC-CM patients (23.1% vs. 59.1%, p = 0.0003), developing allograft failure within the first three months (p < 0.00001). In conclusion, we have demonstrated a relationship between the presence of preformed DSAs and the low graft liver survival, indicating the important role and the potential interest of performing this analysis before liver transplantation. Our results could help to detect patients with an increased risk of graft loss, a better choice of liver receptors as well as the establishment of individualized immunosuppressive regimens.

Selection of unrelated donors and cord blood units for hematopoietic cell transplantation: guidelines from the NMDP/CIBMTR

Allogeneic hematopoietic cell transplantation involves consideration of both donor and recipient characteristics to guide the selection of a suitable graft. Sufficient high-resolution donor-recipient HLA match is of primary importance in transplantation with adult unrelated donors, using conventional graft-versus-host disease prophylaxis. In cord blood transplantation, optimal unit selection requires consideration of unit quality, cell dose and HLA-match. In this summary, the National Marrow Donor Program (NMDP) and the Center for International Blood and Marrow Transplant Research, jointly with the NMDP Histocompatibility Advisory Group, provide evidence-based guidelines for optimal selection of unrelated donors and cord blood units.

iNKT cells and hematopoietic stem cell transplantation: Two-phase activation of iNKT cells may improve outcome

Invariant natural killer T cells (iNKT) produce large amounts of different cytokines which can influence differentiation, polarization and activation of immune cells, particularly NK and T cells. iNKT have been shown to suppress GvHD and promote anti-tumor and anti-pathogen immunity. There are highly specific and safe synthetic ligands such as alpha-galactosylceramide (α-GalCer) and C20:2 which activate iNKT cells toward relatively Th1 and Th2 pathways, respectively. Bone marrow transplantation (BMT) or 'hematopoietic stem cell transplantation' (HSCT) is effective for leukemia and lymphoma through 'graft-versus-leukemia' (GVL) immunity. However, frequent serious complications include graft-versus-host-disease (GVHD), opportunistic infections and relapse. Both GVHD and GVL are mediated by T cells. Manipulating iNKT by different lipid analogues in early and late phases after transplantation may suppress GVHD and graft rejection and enhance GVL effect, as well as resistance to opportunistic infections and so, could be a novel and effective strategy for improving HSCT outcome.

Natural Killer Immunotherapy for Minimal Residual Disease Eradication Following Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia

The most common cause of death in patients with acute myeloid leukemia (AML) who receive allogeneic hematopoietic stem cell transplantation (allo-HSCT) is AML relapse. Therefore, additive therapies post allo-HSCT have significant potential to prevent relapse. Natural killer (NK)-cell-based immunotherapies can be incorporated into the therapeutic armamentarium for the eradication of AML cells post allo-HSCT. In recent studies, NK cell-based immunotherapies, the use of adoptive NK cells, NK cells in combination with cytokines, immune checkpoint inhibitors, bispecific and trispecific killer cell engagers, and chimeric antigen receptor-engineered NK cells have all shown antitumor activity in AML patients. In this review, we will discuss the current strategies with these NK cell-based immunotherapies as possible therapies to cure AML patients post allo-HSCT. Additionally, we will discuss various means of immune escape in order to further understand the mechanism of NK cell-based immunotherapies against AML.

Recipient ADAMTS13 Single-Nucleotide Polymorphism Predicts Relapse after Unrelated Bone Marrow Transplantation for Hematologic Malignancy

Relapse remains a major obstacle to the survival of patients with hematologic malignancies after allogeneic hematopoietic stem cell transplantation. A disintegrin-like and metalloprotease with a thrombospondin type 1 motif (ADMATS13), which cleaves von Willebrand factor multimers into less active fragments, is encoded by the ADAMTS13 gene and has a functional single-nucleotide polymorphism (SNP) rs2285489 (C > T). We retrospectively examined whether ADAMTS13 rs2285489 affected the transplant outcomes in a cohort of 281 patients who underwent unrelated human leukocyte antigen (HLA)-matched bone marrow transplantation for hematologic malignancies. The recipient ADAMTS13 C/C genotype, which putatively has low inducibility, was associated with an increased relapse rate (hazard ratio [HR], 3.12; 95% confidence interval [CI], 1.25–7.77; P = 0.015), resulting in a lower disease-free survival rate in the patients with a recipient C/C genotype (HR, 1.64; 95% CI, 1.01–2.67; P = 0.045). Therefore, ADAMTS13 rs2285489 genotyping in transplant recipients may be a useful tool for evaluating pretransplantation risks.

Adenosinergic signaling as a target for natural killer cell immunotherapy

Purinergic signaling through adenosine plays a key role in immune regulation. Hypoxia-driven accumulation of extracellular adenosine results in the generation of an immunosuppressive niche that fuels tumor development. Such immunometabolic modulation has shown to be a promising therapeutic target through blockade of adenosine receptors which mediate adenosine's immunosuppressive function, or cancer-associated ectonucleotidases CD39 and CD73 that catalyze the synthesis of adenosine. Adenosinergic signaling heavily implicates natural killer cells through both direct and indirect effects on their cytolytic activity, expression of cytotoxic granules, interferon-γ, and activating receptors. Continuing work has uncovered multiple checkpoints linked to adenosine within the purinergic signaling cascade as contributing to immune evasion from NK cell effector function. Here, we discuss these checkpoints and the recent body of work that focuses on adenosinergic signaling as a target for natural killer cell of cancer.

Major Histocompatibility Mismatch and Donor Choice for Second Allogeneic Bone Marrow Transplantation

Large alternative donor pools provide the potential for selecting a different donor for a second allogeneic (allo) bone or marrow transplant (BMT). As HLA disparity may contribute to the graft-versus-tumor effect, utilizing new mismatched haplotype donors may potentially improve the antitumor activity for relapsed hematologic malignancies despite a previous alloBMT. Data from patients who received a second alloBMT for relapsed hematologic malignancies at Johns Hopkins were analyzed. Outcomes were compared between patients who received a second allograft with the same MHC composition and those who received an allograft with a new mismatched haplotype. Loss of heterozygosity analysis was performed for patients with acute myeloid leukemia (AML) whose first allograft was haploidentical. Between 2005 and 2015, 40 patients received a second BMT for a relapsed hematologic malignancy. The median follow-up is 750 (range, 26 to 2950) days. The median overall survival (OS) in the cohort is 928 days (95% confidence interval [CI], 602 to not reached [NR]); median event-free survival (EFS) for the cohort is 500 days (95% CI, 355 to NR). The 4-year OS is 40% (95% CI, 25% to 64%), and the 4-year EFS is 36% (95% CI, 24% to 55%). The cumulative incidence of nonrelapsed mortality by 2 years was 27% (95% CI, 13% to 42%). The cumulative incidence of grade 3 to 4 acute graft-versus-host disease (GVHD) at 100 days was 15% (95% CI, 4% to 26%); the cumulative incidence of extensive chronic GVHD at 2 years was 22% (95% CI, 9% to 36%). The median survival was 552 days (95% CI, 376 to 2950+) in the group who underwent transplantation with a second allograft that did not harbor a new mismatched haplotype, while it was not reached in the group whose allograft contained a new mismatched haplotype (hazard ratio [HR], .36; 95% CI, .14 to .9; P = .02). EFS was also longer in the group who received an allograft containing a new mismatched haplotype, (NR versus 401 days; HR, .50; 95% CI, .22 to 1.14; P = .09). Although the allograft for this patient's second BMT contained a new mismatched haplotype, AML nevertheless relapsed a second time. Second BMTs are feasible and provide a reasonable chance of long-term survival. An allograft with a new mismatched haplotype may improve outcomes after second BMTs for relapsed hematologic malignancies.

Natural Killer Cells from Patients with Recombinase-Activating Gene and Non-Homologous End Joining Gene Defects Comprise a Higher Frequency of CD56bright NKG2A+++ Cells, and Yet Display Increased Degranulation and Higher Perforin Content

Mutations of the recombinase-activating genes 1 and 2 (RAG1 and RAG2) in humans are associated with a broad range of phenotypes. For patients with severe clinical presentation, hematopoietic stem cell transplantation (HSCT) represents the only curative treatment; however, high rates of graft failure and incomplete immune reconstitution have been observed, especially after unconditioned haploidentical transplantation. Studies in mice have shown that Rag^−/− natural killer (NK) cells have a mature phenotype, reduced fitness, and increased cytotoxicity. We aimed to analyze NK cell phenotype and function in patients with mutations in RAG and in non-homologous end joining (NHEJ) genes. Here, we provide evidence that NK cells from these patients have an immature phenotype, with significant expansion of CD56^bright CD16^−/int CD57⁻ cells, yet increased degranulation and high perforin content. Correlation was observed between in vitro recombinase activity of the mutant proteins, NK cell abnormalities, and in vivo clinical phenotype. Addition of serotherapy in the conditioning regimen, with the aim of depleting the autologous NK cell compartment, may be important to facilitate engraftment and immune reconstitution in patients with RAG and NHEJ defects treated by HSCT.

Killer Immunoglobulin-Like Receptor Allele Determination Using Next-Generation Sequencing Technology

The impact of natural killer (NK) cell alloreactivity on hematopoietic stem cell transplantation (HSCT) outcome is still debated due to the complexity of graft parameters, HLA class I environment, the nature of killer cell immunoglobulin-like receptor (KIR)/KIR ligand genetic combinations studied, and KIR⁺ NK cell repertoire size. KIR genes are known to be polymorphic in terms of gene content, copy number variation, and number of alleles. These allelic polymorphisms may impact both the phenotype and function of KIR⁺ NK cells. We, therefore, speculate that polymorphisms may alter donor KIR⁺ NK cell phenotype/function thus modulating post-HSCT KIR⁺ NK cell alloreactivity. To investigate KIR allele polymorphisms of all KIR genes, we developed a next-generation sequencing (NGS) technology on a MiSeq platform. To ensure the reliability and specificity of our method, genomic DNA from well-characterized cell lines were used; high-resolution KIR typing results obtained were then compared to those previously reported. Two different bioinformatic pipelines were used allowing the attribution of sequencing reads to specific KIR genes and the assignment of KIR alleles for each KIR gene. Our results demonstrated successful long-range KIR gene amplifications of all reference samples using intergenic KIR primers. The alignment of reads to the human genome reference (hg19) using BiRD pipeline or visualization of data using Profiler software demonstrated that all KIR genes were completely sequenced with a sufficient read depth (mean 317× for all loci) and a high percentage of mapping (mean 93% for all loci). Comparison of high-resolution KIR typing obtained to those published data using exome capture resulted in a reported concordance rate of 95% for centromeric and telomeric KIR genes. Overall, our results suggest that NGS can be used to investigate the broad KIR allelic polymorphism. Hence, these data improve our knowledge, not only on KIR⁺ NK cell alloreactivity in HSCT but also on the role of KIR⁺ NK cell populations in control of viral infections and diseases.

The recipient CCR5 variation predicts survival outcomes after bone marrow transplantation

The chemokine receptor CCR5 plays roles in the trafficking of effector cells towards the site of inflammation. We retrospectively examined the impact of the CCR5 variation (rs1800023, -2086A>G) on transplant outcomes in a cohort of 329 patients who underwent unrelated HLA-matched bone marrow transplantation (BMT) for hematologic malignancies through the Japan Marrow Donor Program. A multivariate analysis showed that the recipient CCR5 -2086A/A genotype was significantly associated with a lower relapse rate but not with the development of graft-versus-host disease (GVHD) or transplant-related mortality, thereby resulting in better disease-free and overall survival rates than other variations. The donor CCR5 -2086A/A genotype was associated with a lower incidence of grades 3-4 acute GVHD, which did not improve the survival outcomes. These findings suggest that the recipient CCR5 -2086A/A genotype affects the induction of the graft-versus-tumor effect without augmenting the development of GVHD. CCR5 genotyping in transplant recipients may therefore be a useful tool for evaluating pretransplantation risks.

Related haploidentical donors are a better choice than matched unrelated donors: Counterpoint

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