Effect of missing killer-immunoglobulin-like receptor ligand in recipients undergoing HLA full matched, non-T-depleted sibling donor transplantation: a single institution experience of 151 Asian patients

Increased donor inhibitory KIR with known HLA interactions provide protection from relapse following HLA matched unrelated donor HCT for AML

Killer immunoglobulin-like receptor (KIR) and KIR-ligand (KIRL) interactions play an important role in natural killer cell-mediated graft versus leukemia effect (GVL) after hematopoietic cell transplant (HCT) for AML. Accounting for known KIR-KIRL interactions may identify donors with optimal NK cell-mediated alloreactivity and GVL. A retrospective study of 2359 donor-recipient pairs (DRP) who underwent unrelated donor (URD) HCT for AML was performed. KIR-KIRL combinations were determined and associations with clinical outcomes examined. Relapse risk was reduced in DRP with both higher inhibitory KIR-KIRL (iKIR) and missing KIRL (mKIR) scores, with HR 0.86 (P = 0.01) & HR 0.84 (P = 0.02) respectively. The iKIR and mKIR score components were summed to give a maximal inhibitory KIR ligand (IM-KIR) score for each donor, which if it was 5, as opposed to <5, was also associated with a lower relapse risk, SHR 0.8 (P = 0.004). All IM = 5 donors possess KIR Haplotype B/x. Transplant-related mortality was increased among those with IM-KIR = 5, HR, 1.32 (P = 0.01). In a subset analysis of those transplanted with 8/8 HLA-matched DRP, anti-thymocyte globulin recipients with IM-KIR = 5, had a lower relapse rate HR, 0.61 (p = 0.001). This study demonstrates that HLA-matched unrelated donors with the highest inhibitory KIR content confer relapse protection, albeit with increased TRM. These donors all have KIR haplotype B. Clinical trials utilizing donors with a higher iKIR content in conjunction with novel strategies to reduce TRM should be considered for URD HCT in recipients with AML to optimize clinical outcomes.

Influence of KIR and NK Cell Reconstitution in the Outcomes of Hematopoietic Stem Cell Transplantation

Natural killer (NK) cells play a significant role in immune tolerance and immune surveillance. Killer immunoglobin-like receptors (KIRs), which recognize human leukocyte antigen (HLA) class I molecules, are particularly important for NK cell functions. Previous studies have suggested that, in the setting of hematopoietic stem cell transplantation (HSCT), alloreactive NK cells from the donor could efficiently eliminate recipient tumor cells and the residual immune cells. Subsequently, several clinical models were established to determine the optimal donors who would exhibit a graft-vs. -leukemia (GVL) effect without developing graft-vs. -host disease (GVHD). In addition, hypotheses about specific beneficial receptor-ligand pairs and KIR genes have been raised and the favorable effects of alloreactive NK cells are being investigated. Moreover, with a deeper understanding of the process of NK cell reconstitution post-HSCT, new factors involved in this process and the defects of previous models have been observed. In this review, we summarize the most relevant literatures about the impact of NK cell alloreactivity on transplant outcomes and the factors affecting NK cell reconstitution.

The impact of donor full-length KIR2DS4 in the development of acute and chronic GVHD after unrelated allogeneic HSCT

BACKGROUND

Killer Ig-like receptor 2DS4 (KIR2DS4) is the most prevalent activating killer Ig-like receptor gene. It is divergent and encodes either full-length or deleted allele variants. The studies of donor killer KIR2DS4 in unrelated allogeneic hematopoietic stem cell transplantations were limited.

METHODS

KIR and HLA genotyping were determined in 75 pairs of Chinese pediatric hematologic malignancy patients.

RESULTS

Among the 75 donor-recipient pairs, 77.3% (58/75) of the donors were positive for full-length KIR2DS4 and 22.7% (17/75) were negative. Patients who had donors positive for full-length KIR2DS4 had higher cumulative incidence of aGVHD than patients whose donor negative for full-length KIR2DS4 (86.2% versus 76.5%, P = .038). Multivariate analysis showed full-length KIR2DS4 was the significant factor for I-IV aGVHD (HR = 2.166, 95% CI: 1.01-4.26, P = .025). Subgroup analysis showed that AML and CML patients who received donors negative for full-length KIR2DS4 have a higher cumulative incidences of cGVHD (75% vs 62%, P = .008). There were no significant effects of full-length KIR2DS4 on overall survival (P = .13), relapse-free survival (P = .14), CMV reactivation (P = .52), and relapse (HR = 0.38, 95% CI: 0.09-1.6, P = .1875).

CONCLUSIONS

Our findings indicated a significant correlation of donor full-length KIR2DS4 on aGVHD and cGVHD. These results suggested that combining KIR and HLA genotyping may help make a better sense of transplants in these patients.

Donor KIR Genotype Impacts on Clinical Outcome after T Cell-Depleted HLA Matched Related Allogeneic Transplantation for High-Risk Pediatric Leukemia Patients

Preliminary data suggest that ex vivo T cell-depleted matched related donor (MRD) hematopoietic stem cell transplantation (HSCT) is feasible and confers a clinically beneficial reduction in graft-versus-host disease. Classically, T cell-depleted grafts were associated with reduction of the graft-versus-leukemia (GVL) effect because of delayed T cell immune reconstitution. However, natural killer (NK) cell alloreactivity is also critical for an early GVL effect as well as for lymphocyte immune reconstitution. Here, we study the role of NK cells in MRD T cell-depleted HSCT, which is still poorly understood. Given that MRD ligands for inhibitory killer cell immunoglobulin-like receptors (KIRs) are matched, we focused on activating KIR receptors. We retrospectively analyzed KIR genotyping in patients and MRDs in 40 ex vivo T cell-depleted pediatric HSCTs. The log-rank test and Cox proportional risk test were performed to correlate genotype with clinical outcome (relapse rate, disease-free survival, and overall survival) and immune reconstitution. The statistical analysis revealed poorer overall survival when donors have a KIR-B content score of ≥2, a best/better subtype, or present the KIR2DS1 gene. The patient's relapse rate was higher when donors present the KIR2DL5A gene, as well as a poorer probability of disease-free survival when the donor is classified with a best/better subtype. Regarding immune reconstitution, donor KIR haplotype A or the presence of inhibitory KIR genes promote best recovery of T lymphocytes, whereas donor KIR haplotype B or the presence of activating KIR genes confer better expansion of NK cells. These findings suggest that the selection of MRDs with an inhibitory KIR phenotype improve T cell expansion as well as the clinical outcome after pediatric ex vivo T cell-depleted HSCT.

Killer immunoglobulin-like receptor (KIR) and KIR-ligand genotype do not correlate with clinical outcome of renal cell carcinoma patients receiving high-dose IL2

NK cells play a role in many cancer immunotherapies. NK cell activity is tightly regulated by killer immunoglobulin-like receptor (KIR) and KIR-ligand interactions. Inhibitory KIR-ligands have been identified as HLA molecules, while activating KIR-ligands are largely unknown. Individuals that have not inherited the corresponding KIR-ligand for at least one inhibitory KIR gene are termed the "KIR-ligand missing" genotype, and they are thought to have a subset of NK cells that express inhibitory KIRs for which the corresponding KIR-ligand is missing on autologous tissue, and thus will not be inhibited through KIR-ligand recognition. In some settings where an anticancer immunotherapeutic effect is likely mediated by NK cells, individuals with a KIR-ligand missing genotype have shown improved clinical outcome compared to individuals with an "all KIR-ligands present" genotype. In addition, patients receiving hematopoietic stem cell transplants for leukemia may do better if their donor has more activating KIR genes (i.e., KIR haplotype-B). In a recent multi-institution clinical trial of patients with metastatic renal cell carcinoma receiving high-dose IL2 (HD-IL2), 25 % of patients showed a complete or partial tumor response to this therapy. We genotyped KIR and KIR-ligand genes for these patients (n = 107) and tested whether KIR/KIR-ligand genotypes correlated with patient clinical outcomes. In these analyses, we did not find any significant association of KIR/KIR-ligand genotype (either KIR-ligand missing or the presence of KIR haplotype-B) with patient outcome in response to the HD-IL2 therapy.

Synergistic effect of KIR ligands missing and cytomegalovirus reactivation in improving outcomes of haematopoietic stem cell transplantation from HLA-matched sibling donor for treatment of myeloid malignancies

The goal of this study was to evaluate the influence of KIR-HLA genotypes on the outcome of patients undergoing treatment for haematological malignancies by non-T-depleted lymphocyte haematopoietic stem cell transplantation (HSCT) from HLA-matched sibling donors. The prospective study was conducted at the Center of Hematology, University of Campinas, and 50 patients and their donors were followed up from 2008 to 2014. KIR and HLA class I genes were genotyped and patients grouped based on the presence of KIR ligands combined with KIR genotype of their respective donors. Patients with all KIR ligands present (n=13) had a significantly higher (p=0.04) incidence of acute graft-versus-host-disease (GVHD) than patients with one or more KIR ligands missing (n=37). The overall survival following transplantation of patients with myeloid malignancies (n=27) was significantly higher (p=0.035) in the group with one or more KIR ligands missing (n=18) than in the group with all ligands present (n=9). Presence of KIR2DS2 was associated with a worsening of HSCT outcome while reactivation of cytomegalovirus (CMV) infection improved the outcome of patients with one or more KIR ligands missing. Our results indicate that KIR-HLA interactions affect the outcome of the HLA-matched transplantation, particularly in patients with myeloid malignancies.

The effect of missing KIR ligands, activating KIR genotype and haplotype on the outcome of T-cell-replete hematopoietic stem cell transplantation from HLA-identical siblings in Thai patients

This study was a retrospective analysis of Thai patients undergoing T-replete hematopoietic stem cell transplant from human leukocyte antigen (HLA)-identical sibling donors. We investigated 66 patients, including 40 patients with acute myeloid leukemia (AML), 12 patients with acute lymphoblastic leukemia and 14 patients with chronic myeloid leukemia. Killer cell immunoglobulin-like receptor (KIR) genes and HLA ligands were typed by polymerase chain reaction-sequence specific oligonucleotide probes. We analyzed the effect of the number of missing KIR ligands (Bw4, C1 and C2) on clinical outcomes. A beneficial effect of missing KIR ligand was not observed in both univariate and multivariate analysis. When we analyzed the effect of specific missing KIR ligand on clinical outcomes, there was a trend that patients with missing A11 ligand had lower relapse rate (P = 0.076). Therefore, we also conducted the analysis by including the group with missing KIR ligands of Bw4, C1, C2 and A11. Patients with two or more than two missing KIR ligands had a trend for better clinical outcome including reduced relapse (P = 055) and statistically significant in terms of reduced acute graft-vs-host disease (aGVHD) rate (P = 0.013). In multivariate analysis, patients with two or more than two missing KIR ligands had a statistically significant better clinical outcome in terms of reduced aGVHD rate (HR = 0.155, 95%CI = 0.040-0.605, P = 0.007). The association between clinical outcome with KIR haplotypes, centromeric B haplotype and activating KIR was not observed here. Although the sample size in this study is rather limited, these data can later be subjected to meta-analysis to help reach the conclusion of the usefulness of this additional promising KIR genotyping in various hematopoietic stem cell transplantation types.

KIR genotypic diversity in Portuguese and analysis of KIR gene allocation after allogeneic hematopoietic stem cell transplantation

The diversity of killer-cell immunoglobulin-like receptors (KIR) genes was evaluated in Portuguese and the observed genotypic profiles were found related to the ones reported in European populations. The KIR repertoire after hematopoietic stem cell transplantation is determined by these gene frequencies and the KIR group B motifs are the less common. We estimated donor-KIR/recipient-ligand interactions in transplants with related donors and unrelated donors found in a local registry or from abroad. A large fraction of transplants had all three ligands of inhibitory receptors, and therefore, in theory were not prone to natural killer cell (NK) mediated alloreactivity. Furthermore, the distribution of KIR alloreactive interactions was found independent of the donor-recipient genetic proximity, probably because of different gene segregation and comparable KIR frequencies in the donor pools.

Adoptive immunotherapy with polyclonal T cells and natural killer cells for hematological malignancies: current status and future prospects

SUMMARY Adoptive cellular therapy with polyclonal T cells and natural killer cells are immunotherapeutic modalities being studied in solid tumors and hematological malignancies to treat disease and prevent relapse. These include unexpanded polyclonal T cells, short-term activation by cytokine into lymphokine-activated killer cells, longer term expansion by cytokine stimulation giving rise to cytokine-induced killer cells or expansion under costimulation with beads expressing anti-CD3 and anti-CD28. Similarly natural killer cells can be given with or without activation and expansion. Here we review the published work and clinical trials involving each cell type in the autologous, matched allogeneic, haploidentical and nontransplant settings, comparing and contrasting each cell type and discussing their potential applications.

Clinical production and therapeutic applications of alloreactive natural killer cells

Recent advances have improved our understanding of natural killer (NK) cell-mediated alloreactivity after hematopoietic cell transplantation (HCT) or with adoptive transfer. NK cells contribute to a graft-versus-leukemia effect and may play a role in preventing graft-versus-host disease or controlling infectious diseases after allogeneic HCT. New discoveries in NK cell biology, including characterization of NK cell receptors and their interactions with self-HLA molecules and a better understanding of the mechanism of NK cell education have led to the development of novel strategies to exploit NK cell alloreactivity against tumors. While early studies using autologous NK cells lacked efficacy, the use of adoptively transferred NK cells to treat hematopoietic malignancies has been expanding. The production of allogeneic donor NK cells requires efficient removal of T- and B cells from clinical-scale leukapheresis collections. The goal of this chapter is to review NK cell biology, NK cell receptors, the use of NK cells as therapy and then to discuss the clinical decisions resulting in our current good manufacturing practices processing and activation of human NK cells for therapeutic use.

Bone marrow may be the preferable graft source in recipients homozygous for HLA-C group 2 ligands for inhibitory killer Ig-like receptors

HLA class I molecules participate in natural killer cell regulation by acting as ligands for inhibitory killer cell Ig-like receptors (KIRs). One individual may express one or more inhibitory KIR lacking the corresponding HLA ligand. The role of this 'missing KIR ligand' constellation in hematopoietic SCT (HSCT) remains controversial and depends on incompletely defined transplant variables. We have retrospectively analyzed the effects of missing HLA-C group 1/2 and Bw4 KIR ligands in the recipients on the outcome in 382 HSCT, comparing 118 BMT to 264 PBSC transplants (PBSCT). In the multivariate Cox analysis of PBSCT, poor PFS was observed in homozygous HLA-C group 2 (C2/2) recipients (risk ratio (RR), 1.59; P=0.026). In contrast, C2 homozygosity was not unfavorable after BMT (RR, 0.68; P=0.16). C2 homozygous recipients (n=68) had better PFS after BMT than after PBSCT (RR, 0.17; P=0.001), due to fewer relapses (RR, 0.27; P=0.018). Missing Bw4 favorably influenced PFS after BMT (RR, 0.56; P=0.04), but not after PBSCT. These data suggest opposite effects of missing KIR ligands in BMT vs PBSCT. Larger studies are required to reassess whether BMT should be preferred to PBSCT as an option for C2/C2 recipients.

Natural killer cells and tumor control

PURPOSE OF REVIEW

After hematopoietic cell transplantation (HCT) donor-derived natural killer (NK) cells kill tumor cells to prevent relapse and mediate other beneficial clinical effects including control of infections without inducing graft-vs.-host disease (GVHD). Understanding the determinants of NK cell alloreactivity and function will support improvements in the design of HCT and adoptive cellular therapies.

RECENT FINDINGS

Refinements to the model of NK cell education or licensing have been made which will inform strategies to develop functional alloreactive NK cells for therapeutic use. Differences in NK cell function have been shown to be dependent on the nature of the stimuli. Recent advances have been made in our understanding of the role of activating NK receptors on education and outcome after HCT. The use of adoptively transferred NK cells to treat hematopoietic malignancies has been expanding. New approaches to modulate target sensitivity to NK cell-mediated killing are under development.

SUMMARY

NK cells play an important role in the therapeutic efficacy of HCT, with effects on control of infections, GVHD, engraftment and relapse prevention. Recent advances in our understanding of NK cell biology will support improvements in our ability to exploit NK cells to treat cancer.