A defined donor activating natural killer cell receptor genotype protects against leukemic relapse after related HLA-identical hematopoietic stem cell transplantation

Poliovirus receptor-based chimeric antigen receptor T cells combined with NK-92 cells exert potent activity against glioblastoma

BACKGROUND

Poliovirus receptor interacts with 3 receptors: T-cell immunoglobulin immunoreceptor tyrosine-based inhibitory motif, CD96, and DNAX accessory molecule 1, which are predominantly expressed on T cells and natural killer (NK) cells. Many solid tumors, including IDH wild-type glioblastoma, have been reported to overexpress poliovirus receptor, and this overexpression is associated with poor prognosis. However, there are no preclinical or clinical trials investigating the use of cell-based immunotherapies targeting poliovirus receptor in IDH wild-type glioblastoma.

METHODS

We analyzed poliovirus receptor expression in transcriptome sequencing databases and specimens from IDH wild-type glioblastoma patients. We developed poliovirus receptor targeting chimeric antigen receptor T cells using lentivirus. The antitumor activity of chimeric antigen receptor T cells was demonstrated in patient-derived glioma stem cells, intracranial and subcutaneous mouse xenograft models.

RESULTS

We verified poliovirus receptor expression in primary glioma stem cells, surgical specimens from IDH wild-type glioblastoma patients, and organoids. Accordingly, we developed poliovirus receptor-based second-generation chimeric antigen receptor T cells. The antitumor activity of chimeric antigen receptor T cells was demonstrated in glioma stem cells and xenograft models. Tumor recurrence occurred in intracranial xenograft models because of antigen loss. The combinational therapy of tyrosine-based inhibitory motif extracellular domain-based chimeric antigen receptor T cells and NK-92 cells markedly suppressed tumor recurrence and prolonged survival.

CONCLUSIONS

Poliovirus receptor-based chimeric antigen receptor T cells were capable of killing glioma stem cells and suppressing tumor recurrence when combined with NK-92 cells.

Clinical impact of KIR haplotypes in 10/10 HLA-matched unrelated donor-recipient pairs undergoing allogeneic hematopoietic stem cell transplantation

To evaluate the impact of killer immunoglobulin-like receptor (KIR) genotyping in allogeneic hematopoietic stem cell transplantation for myeloid disorders at our institution, retrospective KIR genotyping was performed on 77 patients and their 10/10 matched unrelated donors. In a multivariate model including donor age, HLA-DPB1 permissiveness, and presence of donor KIR B/x, an association with overall survival was observed (p = .047). Within the model, increasing donor age increased risk (RR 1.03 [1.00-1.06]/year, p = .046), while donor KIR and HLA-DPB1 permissiveness were not associated with risk (RR 0.51 [0.26-1.03] and RR 0.68 [0.34-1.36]). Grouping recipients by conditioning regimen or limiting the analysis to recipients of peripheral blood stem cells, no association between donor KIR and survival or relapse was identified. No significant associations were observed between overall survival, relapse, grade III-IV acute, or chronic graft versus host disease and presence of KIR B (B/x), quantity of donor KIR B haplotype motifs, or centromeric KIR type (all p > .05).

The Influence of KIR Gene Polymorphisms and KIR-ligand Binding on Outcomes in Hematologic Malignancies following Haploidentical Stem Cell Transplantation: A Comprehensive Review

Natural killer (NK) cell behavior and function are controlled by a balance between negative or positive signals generated by an extensive array of activating and inhibiting receptors, including killer cell immunoglobulin-like receptor (KIR) proteins, main components of the innate immune system that contribute to initial responses against viral infected-transformed cells through generation of the release of cytokines and cytotoxicity. What is certain is that KIRs are genetically polymorphic and the extent of KIRs diversity within the individuals may have the potential outcomes for hematopoietic stem cell transplantation (HSCT). In this regard, recent studies suggest that KIR is as imperative as its ligand (HLA) in stem cell transplantation for malignant diseases. However, unlike HLA epitope mismatches, which are well-known causes of NK alloreactivity, a complete understanding of KIR genes' role in HSCT remains unclear. Because of genetic variability in KIR gene content, allelic polymorphism, and cell-surface expression among individuals, an appropriate selection of donors based on HLA and KIR profiles is crucial to improve outcomes of stem cell transplantation. In addition, the impact of the KIR/HLA interaction on HSCT outcomes needs to be investigated more comprehensively. The present work aimed to review the NK cell regeneration, KIR gene polymorphisms, and KIRligand binding on outcomes in hematologic malignancies following haploidentical stem cell transplantation. Comprehensive data gathered from the literature can provide new insight into the significance of KIR matching status in transplantations.

Natural killer cells in antitumour adoptive cell immunotherapy

Natural killer (NK) cells comprise a unique population of innate lymphoid cells endowed with intrinsic abilities to identify and eliminate virally infected cells and tumour cells. Possessing multiple cytotoxicity mechanisms and the ability to modulate the immune response through cytokine production, NK cells play a pivotal role in anticancer immunity. This role was elucidated nearly two decades ago, when NK cells, used as immunotherapeutic agents, showed safety and efficacy in the treatment of patients with advanced-stage leukaemia. In recent years, following the paradigm-shifting successes of chimeric antigen receptor (CAR)-engineered adoptive T cell therapy and the advancement in technologies that can turn cells into powerful antitumour weapons, the interest in NK cells as a candidate for immunotherapy has grown exponentially. Strategies for the development of NK cell-based therapies focus on enhancing NK cell potency and persistence through co-stimulatory signalling, checkpoint inhibition and cytokine armouring, and aim to redirect NK cell specificity to the tumour through expression of CAR or the use of engager molecules. In the clinic, the first generation of NK cell therapies have delivered promising results, showing encouraging efficacy and remarkable safety, thus driving great enthusiasm for continued innovation. In this Review, we describe the various approaches to augment NK cell cytotoxicity and longevity, evaluate challenges and opportunities, and reflect on how lessons learned from the clinic will guide the design of next-generation NK cell products that will address the unique complexities of each cancer.

Donor activating killer cell immunoglobulin-like receptors genes correlated with Epstein-Barr virus reactivation after haploidentical haematopoietic stem cell transplantation

Natural killer (NK) cells exert anti-viral effects after haematopoietic stem cell transplantation (HSCT). The balance between inhibition and activation of NK cells determined by the inherited repertoire of killer cell immunoglobulin-like receptors (KIR) genes may influence Epstein-Barr virus (EBV) reactivation after transplantation. To evaluate the relative contributions of KIR genotypes to EBV reactivation, we prospectively enrolled 300 patients with malignant haematological disease who were suitable for haploidentical HSCT. Univariate analysis showed that donors with KIR2DS1, KIR2DS3 or KIR3DS1 genes were associated with an increased risk of EBV reactivation [hazard ratio (HR) 1·86, 95% confidence interval (CI) 1·19-2·9, P = 0·0067; HR 1·78, 95% CI 1·07-2·97, P = 0·027; HR 1·86, 95% CI 1·19-2·91, P = 0·0065 respectively]. Multivariate analysis revealed that the presence of KIR2DS1, KIR2DS3 or KIR3DS1 genes was associated with increased EBV reactivation after HSCT. This effect was more evident in the absence of the cognate ligands for the corresponding activating receptors. Our present data firstly showed that donors with activating KIR genes, specifically activating KIR2DS1, KIR2DS3 and KIR3DS1, had an increased risk of EBV reactivation. Precaution for patients whose donors carry activating genes will help prevent EBV reactivation and improve patient prognosis after HSCT.

NK Cell-Based Immunotherapy and Therapeutic Perspective in Gliomas

Glioma is the most common malignant primary brain tumor diagnosed in adults. Current therapies are unable to improve its clinical prognosis, imposing the need for innovative therapeutic approaches. The main reason for the poor prognosis is the great cell heterogeneity of the tumor and its immunosuppressive microenvironment. Development of new therapies that avoid this immune evasion could improve the response to the current treatments. Natural killer (NK) cells are an intriguing candidate for the next wave of therapies because of several unique features that they possess. For example, NK cell-based immunotherapy causes minimal graft-versus-host disease. Cytokine release syndrome is less likely to occur during chimeric antigen receptor (CAR)-NK therapy, and CAR-NK cells can kill targets in a CAR-independent manner. However, NK cell-based therapy in treating glioma faces several difficulties. For example, CAR molecules are not sufficiently well designed so that they will thoroughly release functioning NK cells. Compared to hematological malignancies, the application of many potential NK cell-based therapies in glioma lags far behind. Here, we review several issues of NK cells and propose several strategies that will improve the efficacy of NK cell-based cancer immunotherapy in the treatment of glioma.

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.

Dynamic mRNA expression of donor-derived activating KIR genes and their significant effects on clinical outcome after haematopoietic stem cell transplantation

Numerous reports suggest that activating killer immunoglobulin-like receptors (aKIRs) of natural killer (NK) cells, in addition to inhibitory KIRs (iKIRs), play a prognostic role after allogeneic haematopoietic stem cell transplantation (allo-HSCT). We aimed to investigate the association between the dynamic expression of KIRs on NK cells and the outcomes, particularly regarding graft-versus-host disease (GvHD). This study retrospectively enrolled 260 pairs of donors and recipients who had undergone allo-HSCT without in-vitro T cell depletion. The mRNA transcription level of KIRs was determined by quantitative real-time polymerase chain reaction (RT-qPCR). The levels of aKIR transcripts were decreased more than those of iKIRs during the occurrence of GvHD. The transcription levels of KIR2DS2 and KIR2DS4 in the patients developing GvHD, compared with those who were at a tolerance state, showed the most significant decrease in the month at their peak transcription levels (p = 0.03, p = 0.002). Significantly decreased expression of KIR2DS1 (p = 0.02), KIR2DS3 (p = 0.04) and KIR2DS5 (p = 0.04) in the GvHD group was observed when the transcription level reached a maximum. High expression of KIR3DS1 was associated with superior overall survival (OS) (p < 0.001). The expression of KIR2DS4 in the KIR genotype Bx group decreased more during GvHD, particularly at 3M (p = 0.02). These findings suggest that KIR genes are potential post-HSCT biomarkers and dynamic changes in the KIR transcription levels can be detected to better predict the occurrence and evaluate the treatment of GvHD after transplantation.

The role of KIR positive NK cells in diseases and its importance in clinical intervention

Natural killer (NK) cells are essential for the elimination of the transformed and cancerous cells. Killer cell immunoglobulin-like receptors (KIRs) which expressed by T and NK cells, are key regulator of NK cell function. The KIR and their ligands, MHC class I (HLA-A, B and C) molecules, are highly polymorphic and their related genes are located on 19 q13.4 and 6 q21.3 chromosomes, respectively. It is clear that particular interaction between the KIRs and their related ligands can influence on the prevalence, progression and outcome of several diseases, like complications of pregnancy, viral infection, autoimmune diseases, and hematological malignancies. The mechanisms of immune signaling in particular NK cells involvement in causing pathological conditions are not completely understood yet. Therefore, better understanding of the molecular mechanism of KIR-MHC class I interaction could facilitate the treatment strategy of diseases. The present review focused on the main characteristics and functional details of various KIR and their combination with related ligands in diseases and also highlights ongoing efforts to manipulate the key checkpoints in NK cell-based immunotherapy.

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.

Killer Immunoglobulin-Like Receptor-Ligand Interactions Predict Clinical Outcomes following Unrelated Donor Transplantations

Killer immunoglobulin-like receptor (KIR) and KIR ligand (KIRL) interactions play an important role in natural killer (NK) cell-mediated graft-versus-leukemia effect following hematopoietic cell transplantation (HCT). However, there is considerable heterogeneity in the KIR gene and KIRL content in individuals, making it difficult to estimate the full clinical impact of NK cell reconstitution following HCT. Here we present a novel adaptive mathematical model designed to quantify these interactions to better assess the influence of NK cell-mediated alloreactivity on transplant outcomes. Ninety-eight HLA- matched unrelated donor (URD) HCT recipients were studied retrospectively. The KIR-KIRL interactions were quantified using a system of matrix equations. Unit values were ascribed to each KIR-KIRL interaction, and the directionality of interactions was denoted by either a positive (activating) or negative (inhibition) symbol; these interactions were then summed. The absolute values of both the missing KIRL and inhibitory KIR-KIRL interactions were significantly associated with overall survival and relapse. These score components were initially used to develop a weighted score (w-KIR score) and subsequently a simplified, nonweighted KIR-KIRL interaction score (IM-KIR score). Increased w-KIR score and IM-KIR score were predictive of all-cause mortality and relapse (w-KIR score: hazard ratio [HR], .37 [P = .001] and .44 [P = .044], respectively; IM-KIR score: HR, .5 [P = .049] and .44 [P = .002], respectively). IM-KIR score was also associated with NK cell reconstitution post-HCT. KIR-KIRL interactions as reflected by the w-KIR and IM-KIR scores influence both relapse risk and survival in recipients of HLA-matched URD HCT with hematologic malignancies.

NK Cells in the Treatment of Hematological Malignancies

Natural killer (NK) cells have the innate ability to kill cancer cells, however, tumor cells may acquire the capability of evading the immune response, thereby leading to malignancies. Restoring or potentiation of this natural antitumor activity of NK cells has become a relevant therapeutic approach in cancer and, particularly, in hematological cancers. The use of tumor-specific antibodies that promote antibody-dependent cell-mediated cytotoxicity (ADCC) through the ligation of CD16 receptor on NK cells has become standard for many hematologic malignancies. Hematopoietic stem cell transplantation is another key therapeutic strategy that harnesses the alloreactivity of NK cells against cancer cells. This strategy may be refined by adoptive transfer of NK cells that may be previously expanded, activated, or redirected (chimeric antigen receptor (CAR)-NK cells) against cancer cells. The antitumor activity of NK cells can also be boosted by cytokines or immunostimulatory drugs such as lenalidomide or pomalidomide. Finally, targeting immunosubversive mechanisms developed by hematological cancers and, in particular, using antibodies that block NK cell inhibitory receptors and checkpoint proteins are novel promising therapeutic approaches in these malignant diseases.

Certain Killer Immunoglobulin-Like Receptor (KIR)/KIR HLA Class I Ligand Genotypes Influence Natural Killer Antitumor Activity in Myelogenous Leukemia but Not in Acute Lymphoblastic Leukemia: A Case Control Leukemia Association Study

Objective:

Natural killers (NK) cell function is mainly controlled by the expression of killer immunoglobulin-like receptors (KIRs) and their ligation with the corresponding ligands. The objective of this study was to investigate the putative association of KIRs, HLA class I ligands, and KIR/ligand combinations with rates of development of acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML).

Materials and Methods:

The KIR/HLA I genotypes of 82 patients with leukemia (ALL, n=52; AML, n=17; and CML, n=13) were determined by PCR-SSP method and compared with genotypes of healthy controls (n=126).

Results:

KIR genotype frequency differed significantly between myelogenous leukemia patients and healthy controls for KIR2DL5A (17.6% vs. 47.7%, p=0.02), KIR3DS1 (17.6% vs. 47.6%, p=0.02), and KIR2DS4*001 (36.6% vs. 20.2%, p=0.017). The incidence of homozygous HLA-BBw4 (31.0% vs. 12.5%, p=0.042) and HLA-Bw4Thr80 Thr80 (13.0% vs. 1.2%, p=0.01) was significantly elevated in myeloid leukemia patients compared to healthy controls. KIR/HLA class I ligand profile KIR3DS1(+)/L (-) was decreased and KIR3DL2(+)/HLA-A3/11(-) was increased among myeloid leukemia cases compared to controls.

Conclusion:

These data suggest that the activity of NK cells as determined by inherited KIR/HLA class I ligand polymorphisms influences the susceptibility to myelogenous leukemia, but not to lymphoblastic leukemia. Additionally, the KIR genotype characterized by the absence of the inhibitory KIR2DL2 and the activating KIR2DS2 and KIR2DS3 (ID2) was found at a lower frequency in patients compared to controls, which confirmed the need for complex analysis based on all possible KIR/HLA class I ligand polymorphism combinations.

Immunophenotypic, cytotoxic, proteomic and genomic characterization of human cord blood vs. peripheral blood CD56Dim NK cells

Unrelated cord blood (CB) is an excellent alternative as an allogeneic donor source for stem cell transplantation. CB transplantation is associated with lower incidence of severe acute graft versus host disease (GVHD) and chronic GVHD but similar rates of malignant relapse compared with other unrelated donor cell transplants. NK cells are critical innate immune components and the comparison of CB vs. peripheral blood (PB) NK cells is relatively unknown. NK cell receptor expression, cell function, and maturation may play a role in the risk of relapse after CB transplant. We investigated CB vs. PB NK cell subset cytotoxicity, function, receptor expression, and genomic and proteomic signatures. The CB CD56^dim compared with PB CD56^dim demonstrated significantly increased expression of NKG2A and NKG2D, respectively. CB vs. PB CD56^dim NK cells had significantly decreased in vitro cytotoxicity against a variety of non-Hodgkin lymphoma targets. Various proteins were significantly under- and over-expressed in CB vs. PB CD56^dim NK cells. Microarray analyses and qRT-PCR in CB vs. PB CD56^dim demonstrated significantly increased expression of genes in cell regulation and development of apoptosis, respectively. In summary, CB vs. PB CD56^dim NK cells appear to be earlier in development, have decreased functional activity, and increased capacity for programmed cell death, suggesting that CB NK cells require functional and maturational stimulation to achieve similar functional levels as PB CD56^dim NK cells.

Contribution of NK cells to immunotherapy mediated by PD-1/PD-L1 blockade

Checkpoint blockade immunotherapy targeting the PD-1/PD-L1 inhibitory axis has produced remarkable results in the treatment of several types of cancer. Whereas cytotoxic T cells are known to provide important antitumor effects during checkpoint blockade, certain cancers with low MHC expression are responsive to therapy, suggesting that other immune cell types may also play a role. Here, we employed several mouse models of cancer to investigate the effect of PD-1/PD-L1 blockade on NK cells, a population of cytotoxic innate lymphocytes that also mediate antitumor immunity. We discovered that PD-1 and PD-L1 blockade elicited a strong NK cell response that was indispensable for the full therapeutic effect of immunotherapy. PD-1 was expressed on NK cells within transplantable, spontaneous, and genetically induced mouse tumor models, and PD-L1 expression in cancer cells resulted in reduced NK cell responses and generation of more aggressive tumors in vivo. PD-1 expression was more abundant on NK cells with an activated and more responsive phenotype and did not mark NK cells with an exhausted phenotype. These results demonstrate the importance of the PD-1/PD-L1 axis in inhibiting NK cell responses in vivo and reveal that NK cells, in addition to T cells, mediate the effect of PD-1/PD-L1 blockade immunotherapy.

KIR Donor Selection: Feasibility in Identifying better Donors

We previously reported that acute myelogenous leukemia (AML) transplants using killer cell immunoglobulin-type receptor (KIR) B haplotype better or best (≥2 B activating gene loci ± Cen B/B) unrelated donors (URDs) yield less relapse and better survival. In this prospective trial we evaluated 535 AML searches from 14 participating centers with centralized donor KIR genotyping for donor selection. This represented 3% to 48% of all AML searches (median 20%) per center, totaling 3 to 172 patients (median 22) per center. Donor KIR genotype was reported at a median of 14 days after request (≤26 days for 76% of searches). In 535 searches, 2080 donors were requested for KIR genotyping (mean 4.3 per search); and a median of 1.8 (range, 0 to 4.5) per search were KIR typed. Choosing more donors for confirmatory HLA and KIR haplotype identification enriched the likelihood of finding KIR better or best donors. The search process identified a mean of 30% KIR better or best donors; the success ranged from 24% to 38% in the 11 centers enrolling ≥8 patients. More donors requested for KIR genotyping increased the likelihood of identifying KIR better or best haplotype donors. Of the 247 transplants, 9.3% used KIR best, 19% used KIR better, and 48% used KIR neutral donors while 24% used a non-KIR-tested donor. KIR genotyping did not delay transplantation. The time from search to transplant was identical for transplants using a KIR-genotyped versus a non-KIR-genotyped donor. Prospective evaluation can rapidly identify KIR favorable genotype donors, but choosing more donors per search would substantially increase the likelihood of having a KIR best or better donor available for transplantation. Transplant centers and donor registries must both commit extra effort to incorporate new characteristics (beyond HLA, age, and parity) into improved donor selection. Deliberate efforts to present additional genetic factors for donor selection will require novel procedures.

Activating KIR Haplotype Influences Clinical Outcome Following HLA-Matched Sibling Hematopoietic Stem Cell Transplantation

Natural killer cells are thought to influence the outcome of hematopoietic stem cell transplant (HSCT), impacting on relapse, overall survival, graft versus host disease and the control of infection, in part through the complex interplay between the large and genetically diverse killer immunoglobulin-like receptor (KIR) family and their ligands. This study examined the relationship between KIR gene content and clinical outcomes including the control of opportunistic infections such as cytomegalovirus in the setting of human leucocyte antigen (HLA)-matched sibling HSCT in an Australian cohort. The presence of the KIR B haplotype which contain more activating receptors in the donor, in particular centromeric B haplotype genes (Cen-B), was associated with improved overall survival of patients with acute myeloid leukemia (AML) undergoing sibling HSCT and receiving myeloablative conditioning. Donor Cen-B haplotype was also associated with reduced acute graft versus host disease grades II-IV whereas donor telomeric-B haplotype was associated with decreased incidence of CMV reactivation. In contrast, we were not able to demonstrate a reduced rate of relapse when the donor had KIR Cen-B, however relapse with a donor Cen-A haplotype was a competing risk factor to poor overall survival. Here we show that the presence of donor activating KIR led to improved outcome for the patient, potentially through reduced relapse rates and decreased incidence of acute GvHD translating to improved overall survival. This article is protected by copyright. All rights reserved.

NK cell therapy for hematologic malignancies

Natural killer (NK) cells are part of the innate immune system and represent the first line of defense against infections and tumors. In contrast to T cells, NK cells do not require prior antigen sensitization to induce cytotoxicity and do not cause graft-versus-host disease. These, along with other advantages, make NK cells an attractive candidate for adoptive cellular therapy. Herein, we describe the mechanisms of NK cell cytotoxicity, which is governed by an intricate balance between various activating and inhibitory receptors, including the killer cell immunoglobulin-like receptors (KIRs). We illustrate the advantages of NK alloreactivity as demonstrated in various types of hematopoietic stem cell transplants (HSCT), such as haploidentical, human leukocyte antigen-matched related or unrelated donor and umbilical cord blood transplant. We elaborate on different models used to predict NK cell alloreactivity in these studies, which are either based on the absence of the ligands for inhibitory KIRs, presence of activating NK cell receptors and KIR genes content in donors, or a combination of these. We will review clinical studies demonstrating anti-tumor efficacy of NK cells used either as a stand-alone immunotherapy or as an adjunct to HSCT and novel genetic engineering strategies to improve the anti-tumor activity of NK cells.

The effect of killer cell immunoglobulin-like receptor genotype on outcome of hematopoietic stem cell transplantation from matched sibling

The alloreactivity of natural killer (NK) cell after allogeneic hematopoietic stem cell transplantation (AHSCT) is regulated by the interaction between donor killer immunoglobulin-like receptors (KIRs) and recipient human leukocyte antigen (HLA)-class I molecules. The aim was to identify KIR genes, haplotypes and their HLA-class I ligands and to investigate their association with transplantation outcome. The study included 65 patient/donor pairs who received AHSCT from HLA-matched identical siblings. KIR genotyping was done for donors using reverse sequence specific oligonucleotide probes (rSSO) coupled with luminex technology, while HLA-C genotyping was performed in patients using rSSO strip assay. In multivariate analysis, KIR2DS4 was associated with significant reduced incidence of relapse (p = .002). A trend towards reduced incidence of relapse was also observed with more than two KIR B motifs (p = .09), whereas a significant increased relapse was associated with homozygous HLA-C2 ligand compared to combined C1/C2 and C1/C1 (p = .04). Activating KIR2DS3 was associated with rapid leukocyte engraftment (p = .02). While, KIR 2DL5 was associated with decreased CMV infection (p = .03) and better platelets engraftment (p = .05). KIR genes, haplotypes and HLA-C alleles have an impact on HSCT outcome. Better selection of donors with favorable KIR genotype can improve HLA-matched sibling HSCT outcome especially for AML patients.

KIR3DS1-Mediated Recognition of HLA-*B51: Modulation of KIR3DS1 Responsiveness by Self HLA-B Allotypes and Effect on NK Cell Licensing

Several studies described an association between killer-cell immunoglobulin-like receptor (KIR)/HLA gene combinations and clinical outcomes in various diseases. In particular, an important combined role for KIR3DS1 and HLA-B Bw4-I80 in controlling viral infections and a higher protection against leukemic relapses in donor equipped with activating KIRs in haplo-HSCT has been described. Here, we show that KIR3DS1 mediates positive signals upon recognition of HLA-B*51 (Bw4-I80) surface molecules on target cells and that this activation occurs only in Bw4-I80^neg individuals, including those carrying particular KIR/HLA combination settings. In addition, killing of HLA-B*51 transfected target cells mediated by KIR3DS1⁺/NKG2A⁺ natural killer (NK) cell clones from Bw4-I80^neg donors could be partially inhibited by antibody-mediated masking of KIR3DS1. Interestingly, KIR3DS1-mediated recognition of HLA-B*51 could be better appreciated under experimental conditions in which the function of NKG2D was reduced by mAb-mediated blocking. This experimental approach may mimic the compromised function of NKG2D occurring in certain viral infections. We also show that, in KIR3DS1⁺/NKG2A⁺ NK cell clones derived from an HLA-B Bw4-T80 donor carrying 2 KIR3DS1 gene copy numbers, the positive signal generated by the engagement of KIR3DS1 by HLA-B*51 resulted in a more efficient killing of HLA-B*51-transfected target cells. Moreover, in these clones, a direct correlation between KIR3DS1 and NKG2D surface density was detected, while the expression of NKp46 was inversely correlated with that of KIR3DS1. Finally, we analyzed KIR3DS1⁺/NKG2A⁺ NK cell clones from a HLA-B Bw4^neg donor carrying cytoplasmic KIR3DL1. Although these clones expressed lower levels of surface KIR3DS1, they displayed responses comparable to those of NK cell clones derived from HLA-B Bw4^neg donors that expressed surface KIR3DL1. Altogether these data suggest that, in particular KIR/HLA combinations, KIR3DS1 may play a role in the process of human NK cell education.

HLA-C KIR-Ligands Determine the Impact of Anti-Thymocyte Globulin (ATG) on Graft versus Host and Graft versus Leukemia Effects Following Hematopoietic Stem Cell Transplantation

Rabbit anti-thymocyte globulins (ATGs) are widely used for the prevention of acute and chronic graft versus host disease (aGVHD, cGVHD) following allogeneic hematopoietic stem cell transplantation (HSCT). However, most prospective and retrospective studies did not reveal an overall survival (OS) benefit associated with ATG. Homozygosity for human leukocyte antigen (HLA)-C group 1 killer-cell immunoglobulin-like receptor ligands (KIR-L), i.e. C1/1 KIR-L status, was recently shown to be a risk factor for severe aGVHD. Congruously, we have previously reported favorable outcomes in C1/1 recipients after ATG-based transplants in a monocentric analysis. Here, within an extended cohort, we test the hypothesis that incorporation of ATG for GVHD prophylaxis may improve survival particularly in HSCT recipients with at least one C1 KIR-ligand. Retrospectively, 775 consecutive allogeneic (excluding haploidentical) HSCTs were analyzed, including peripheral blood and bone marrow grafts for adults with hematological diseases at two Austrian HSCT centers. ATG-Fresenius/Grafalon, Thymoglobuline, and alemtuzumab were applied in 256, 87, and 7 transplants, respectively (subsequently summarized as "ATG"), while 425 HSCT were performed without ATG. Median follow-up of surviving patients is 48 months. Adjusted for age, disease-risk, HLA-match, donor and graft type, sex match, cytomegalovirus serostatus, conditioning intensity, and type of post-grafting GVHD prophylaxis, Cox regression analysis of the entire cohort (n = 775) revealed a significant association of ATG with decreased non-relapse mortality (NRM) (risk ratio (RR), 0.57; p = 0.001), and overall mortality (RR, 0.71; p = 0.014). Upon stratification for HLA-C KIR-L, the greatest benefit for ATG emerged in C1/1 recipients (n = 291), by reduction of non-relapse (RR, 0.34; p = 0.0002) and overall mortality (RR, 0.50; p = 0.003). Less pronounced, ATG decreased NRM (RR, 0.60; p = 0.036) in HLA-C group 1/2 recipients (n = 364), without significantly influencing overall mortality (RR, 0.70; p = 0.065). After exclusion of higher-dose ATG-based transplants, serotherapy significantly improved both NRM (RR, 0.54; p = 0.019; n = 322) and overall mortality (RR, 0.60; p = 0.018) in C1/2 recipients as well. In both, C1/1 (RR, 1.70; p = 0.10) and particularly in C1/2 recipients (RR, 0.94; p = 0.81), there was no statistically significant impact of ATG on relapse incidence. By contrast, in C2/2 recipients (n = 121), ATG neither reduced NRM (RR, 1.10; p = 0.82) nor overall mortality (RR, 1.50; p = 0.17), but increased the risk for relapse (RR, 4.38; p = 0.02). These retrospective findings suggest ATG may provide a survival benefit in recipients with at least one C1 group KIR-L, by reducing NRM without significantly increasing the relapse risk.

The impact of KIR2DS4 gene on clinical outcome after hematopoietic stem cell transplantation

Killer cell immunoglobulin-like receptors (KIR) are a family of inhibitory/activating receptors expressed on NK cells. Interactions of KIR receptors with KIR ligands have been shown to modify hematopoietic stem cell transplantation (HSCT) outcome. The aim of this research was to determine the KIR2DS4 allele variants distribution among 111 patients with different hematological malignancy who underwent HSCT and their donors, and to evaluate KIR2DS4 alleles' impact on HSCT outcome. The KIR gene frequency analysis showed a significantly higher incidence of full-length KIR2DS4 alleles among patients. The impact of KIR2DS4 alleles on transplantation outcomes revealed that donors' full-length KIR2DS4 alleles is associated with lower overall survival rates, higher risk of GVHD and higher relapse incidence. The expression of full-length KIR2DS4 allele variants may contribute to a worse clinical outcome after HSCT. KIR typing for KIR2DS4 could be used as an additional criterion for selecting suitable donors in cases when more than one HLA identical donor is identified for a specific patient.

Can we make a better match or mismatch with KIR genotyping?

Natural killer (NK) cell function is regulated by a fine balance between numerous activating and inhibitory receptors, of which killer-cell immunoglobulin-like receptors (KIRs) are among the most polymorphic and comprehensively studied. KIRs allow NK cells to recognize downregulation or the absence of HLA class I molecules on target cells (known as missing-self), a phenomenon that is commonly observed in virally infected cells or cancer cells. Because KIR and HLA genes are located on different chromosomes, in an allogeneic environment such as after hematopoietic stem cell transplantation, donor NK cells that express an inhibitory KIR for an HLA class I molecule that is absent on recipient targets (KIR/KIR-ligand mismatch), can recognize and react to this missing self and mediate cytotoxicity. Accumulating data indicate that epistatic interactions between KIR and HLA influence outcomes in several clinical conditions. Herein, we discuss the genetic and functional features of KIR/KIR-ligand interactions in hematopoietic stem cell transplantation and how these data can guide donor selection. We will also review clinical studies of adoptive NK cell therapy in leukemia and emerging data on the use of genetically modified NK cells that could broaden the scope of cancer immunotherapy.

Natural killer cells in malignant hematology: A primer for the non-immunologist

Natural killer cells were first described over 40years ago, but the last 15years has shown tremendous progress in our understanding of their biology and our ability to manipulate them for clinical therapeutic effect. Despite the increased understanding by clinicians and scientists investigating these cells, their biology remains a confusing subject for many because of the wide array of receptors, complex interactions, multiple models of predicting function, and contradictory data in the literature. While they are microscopically indistinguishable from T cells and share many of the same effector functions, their mechanisms of target recognition are completely distinct from yet complimentary to T cells. In this review we provide a basic understanding of NK cell biology and HLA recognition as compared and contrasted to T cells using a metaphor of border patrol and passports. We conclude with a summary of the evidence for NK cell effects in hematologic malignancies and describe new advances in NK cell immunotherapy aimed at improving these effects.

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.

Donor KIR B Genotype Improves Progression-Free Survival of Non-Hodgkin Lymphoma Patients Receiving Unrelated Donor Transplantation

Donor killer immunoglobulin-like receptor (KIR) genotypes are associated with relapse protection and survival after allotransplantation for acute myelogenous leukemia. We examined the possibility of a similar effect in a cohort of 614 non-Hodgkin lymphoma (NHL) patients receiving unrelated donor (URD) T cell-replete marrow or peripheral blood grafts. Sixty-four percent (n = 396) of donor-recipient pairs were 10/10 allele HLA matched and 26% were 9/10 allele matched. Seventy percent of donors had KIR B/x genotype; the others had KIR A/A genotype. NHL patients receiving 10/10 HLA-matched URD grafts with KIR B/x donors experienced significantly lower relapse at 5 years (26%; 95% confidence interval [CI], 21% to 32% versus 37%; 95% CI, 27% to 46%; P = .05) compared with KIR A/A donors, resulting in improved 5-year progression-free survival (PFS) (35%; 95% CI, 26% to 44% versus 22%; 95% CI, 11% to 35%; P = .007). In multivariate analysis, use of KIR B/x donors was associated with significantly reduced relapse risk (relative risk [RR], .63, P = .02) and improved PFS (RR, .71, P = .008). The relapse protection afforded by KIR B/x donors was not observed in HLA-mismatched transplantations and was not specific to any particular KIR-B gene. Selecting 10/10 HLA-matched and KIR B/x donors should benefit patients with NHL receiving URD allogeneic transplantation.

Killer-cell immunoglobulin-like receptor genes and ligands and their role in hematologic malignancies

Natural killer (NK) cells are considered crucial for the elimination of emerging tumor cells. Effector NK-cell functions are controlled by interactions of inhibitory and activating killer-cell immunoglobulin-like receptors (KIRs) on NK cells with human leukocyte antigen (HLA) class I ligands on target cells. KIR and HLA are highly polymorphic genetic systems segregating independently, creating a great diversity in KIR/HLA gene profiles in different individuals. There is an increasing evidence supporting the relevance of KIR and HLA ligand gene background for the occurrence and outcome of certain cancers. However, the data are still controversial and the mechanisms of receptor-ligand mediated NK-cell action remain unclear. Here, the main characteristics and functions of KIRs and their HLA class I ligands are reviewed. In addition, we review the HLA and KIR correlations with different hematological malignancies and discuss our current understanding of the biological significance and mechanisms underlying these associations.

The role of NK cells in HIV-1 protection: autologous, allogeneic or both?

Natural killer (NK) cells specialize in killing virally infected- or tumor cells and are part of the innate immune system. The activational state of NK cells is determined by the balance of incoming activating and inhibitory signals mediated by receptor-ligand binding with the target cell. These receptor-ligand bonds mainly consist of the killer immunoglobulin-like receptors (KIR), which are expressed at the cell surface of NK cells, and their ligands: the highly variable human leukocyte antigen -class I molecules (HLA). Absence of an inhibitory receptor-ligand bond lowers the NK cell activation threshold, whereas an activating receptor-ligand bond stimulates the cell, potentially overcoming this threshold and triggering NK cell activation. NK cells influence the course of infection as well as the acquisition of HIV-1. Several lines of evidence relate the activating NK cell receptor KIR3DS1, in the presence or absence of its putative ligand HLA-Bw4, with slower disease progression as well as resistance to HIV-1 infection. Overall, resistance to HIV-1 infection predominantly correlates with activating KIR/HLA profiles, consisting of e.g. activating KIRs, group B haplotypes, or inhibitory KIRs in absence of their ligands. Such a conclusion is less evident for studies of HIV-1 disease progression, with studies reporting beneficial as well as detrimental effects of activating KIR/HLA genotypes. It is likely that KIR/HLA association studies are complicated by the complexity of the KIR and HLA loci and their mutual interactions, as well as by additional factors like route of HIV exposure, immune activation, presence of co-infections, and the effect of anti-HIV-1 antibodies. One newly discovered NK cell activation pathway associated with resistance to HIV-1 infection involves the presence of an iKIR/HLA mismatch between partners. The absence of such an iKIR/HLA bond renders donor-derived allogeneic HIV-1 infected cells vulnerable to NK cell responses during HIV-1 transmission. Therefore, theoretically, HIV-1 would be eliminated before it has the chance to infect the autologous cells in the recipient. While this “alloreactive” NK cell mechanism is especially relevant to HIV transmission in monogamous couples, it would be interesting to investigate how it could influence resistance to HIV in other settings. The objective of this review is to summarize the knowledge about these autologous and alloreactive NK cell responses with regard to HIV-1 outcome.

[Genes of killer cell immunoglobulin-like receptors and their HLA ligands after allogeneic hematopoietic stem cell transplantation in myeloid leukemia patients]

AIM

To study the impact of the genes of donor killer cell immunoglobulin-like receptors (KIR) and HLA-KIR ligands on overall (OS) and event-free survival (EFS) rates in patients with myeloid leukemia after transplantation with allogeneic hematopoietic stem cells (allo-HSCT) from HLA-identical related and HLA-compatible unrelated donors.

SUBJECTS AND METHODS

The investigation enrolled 29 patients who had undergone allo-HSCT from KIR-genotyped donors at the Department of Bone Marrow Transplantation, Hematology Research Center (see symbol) in 2010-2013. OS and EFS rates after allo-HSCT were calculated using the Kaplan-Meier method.

RESULTS

The main predictor of recurrence and survival in patients after allo-HSCT was a recurrence-risk group the patient belonged to before transplantation. The standard-risk group patients whose donors had telomeric gene-content motifs of KIR-B haplotypes had higher EFS rates than those whose donors lacked these genes. The standard-risk patients homozygous for HLA-1 alleles (i.e. without HLA-C2 ligand) tended to have higher EFS rates, so did the patients without HLA-Bw4 ligand.

CONCLUSION

The donors having telomeric gene-content motifs of KIR-B haplotypes are more preferred for allo-HSCT for patients with myeloid leukemia as the presence of donor telomeric KIR-B genes increases EFS rates in standard-risk patients.

Impact of "Killer Immunoglobulin-Like Receptor /Ligand" Genotypes on Outcome following Surgery among Patients with Colorectal Cancer: Activating KIRs Are Associated with Long-Term Disease Free Survival

Approximately 30 % of patients with stage II/III colorectal cancer develop recurrence following surgery. How individual regulation of host mediated anti-tumor cytotoxicity is modified by the killer-cell immunoglobulin-like receptor (KIRs) genotype is essential for prediction of outcome. We analyzed the frequency of KIR and KIR ligand Human Leukocyte Antigen Class I genotypes, and their effects on recurrence and disease-free survival (DFS). Out of randomly selected 87 colorectal cancer patients who underwent R0 resection operations between 2005 and 2008, 29 patients whose cancers progressed within a median five-year follow-up period were compared with 58 patients with no recurrence within the same time period. Recurrent cases shared similar tumor stages with non-recurrent cases, but had different localizations. We used DNA isolated from pathological archival lymphoid and tumor tissues for KIR and KIR ligand (HLA-C, group C1, group C2, and HLA-A-Bw4) genotyping. Among cases with recurrence, KIR2DL1 (inhibitory KIR) and A-Bw4 (ligand for inhibitory KIR3DL1) were observed more frequently (p=0.017 and p=0.024); and KIR2DS2 and KIR2DS3 (both activating KIRs) were observed less frequently (p=0.005 and p=0.043). Similarly, in the non-recurrent group, inhibitory KIR-ligand combinations 2DL1-C2 and 2DL3-C1 were less frequent, while the activating combination 2DS2-C1 was more frequent. The lack of KIR2DL1, 2DL1-C2, and 2DL3-C1 improved disease-free survival (DFS) (100% vs. 62.3%, p=0.05; 93.8% vs. 60.0%, p=0.035; 73.6% vs. 55.9%, p=0.07). The presence of KIR2DS2, 2DS3, and 2DS2-C1 improved DFS (77.8% vs. 48.5%, p=0.01; 79.4% vs. 58.5%, p=0.003; 76.9% vs. 51.4%, p=0.023). KIR2DS3 reduced the risk of recurrence (HR=0.263, 95% CI = 0.080-0.863, p=0.028). The number of activating KIRs are correlated strongly with DFS, none/ one/ two KIR : 54/77/98 months (p=0.004). In conclusion the inheritance of increasing numbers of activating KIRs and lack of inhibitory KIRs, independent of tumor localization or stage, is associated with long-term DFS.

Impact of KIR and HLA Genotypes on Outcomes after Reduced-Intensity Conditioning Hematopoietic Cell Transplantation

Natural killer cells are regulated by killer cell immunoglobulin-like receptor (KIR) interactions with HLA class I ligands. Several models of natural killer cell reactivity have been associated with improved outcomes after myeloablative allogeneic hematopoietic cell transplantation (HCT), but this issue has not been rigorously addressed in reduced-intensity conditioning (RIC) unrelated donor (URD) HCT. We studied 909 patients undergoing RIC-URD HCT. Patients with acute myeloid leukemia (AML, n = 612) lacking ≥ 1 KIR ligands experienced higher grade III to IV acute graft-versus-host disease (GVHD) (HR, 1.6; 95% CI, 1.16 to 2.28; P = .005) compared to those with all ligands present. Absence of HLA-C2 for donor KIR2DL1 was associated with higher grade II to IV (HR, 1.4; P = .002) and III to IV acute GVHD (HR, 1.5; P = .01) compared with HLA-C2(+) patients. AML patients with KIR2DS1(+), HLA-C2 homozygous donors had greater treatment-related mortality compared with others (HR, 2.4; 95% CI, 1.4 to 4.2; P = .002) but did not experience lower relapse. There were no significant associations with outcomes for AML when assessing donor-activating KIRs or centromeric KIR content or for any donor-recipient KIR-HLA assessments in patients with myelodysplastic syndrome (n = 297). KIR-HLA combinations in RIC-URD HCT recapitulate some but not all KIR-HLA effects observed in myeloablative HCT.

Acute GVHD in patients receiving IL-15/4-1BBL activated NK cells following T-cell-depleted stem cell transplantation

Natural killer (NK) cells can enhance engraftment and mediate graft-versus-leukemia following allogeneic hematopoietic stem cell transplantation (HSCT), but the potency of graft-versus-leukemia mediated by naturally reconstituting NK cells following HSCT is limited. Preclinical studies demonstrate that activation of NK cells using interleukin-15 (IL-15) plus 4-1BBL upregulates activating receptor expression and augments killing capacity. In an effort to amplify the beneficial effects of NK cells post-HSCT, we conducted a first-in-human trial of adoptive transfer of donor-derived IL-15/4-1BBL-activated NK cells (aNK-DLI) following HLA-matched, T-cell-depleted (1-2 × 10(4) T cells/kg) nonmyeloablative peripheral blood stem cell transplantation in children and young adults with ultra-high-risk solid tumors. aNK-DLI were CD3(+)-depleted, CD56(+)-selected lymphocytes, cultured for 9 to 11 days with recombinant human IL-15 plus 4-1BBL(+)IL-15Rα(+) artificial antigen-presenting cells. aNK-DLI demonstrated potent killing capacity and displayed high levels of activating receptor expression. Five of 9 transplant recipients experienced acute graft-versus-host disease (GVHD) following aNK-DLI, with grade 4 GVHD observed in 3 subjects. GVHD was more common in matched unrelated donor vs matched sibling donor recipients and was associated with higher donor CD3 chimerism. Given that the T-cell dose was below the threshold required for GVHD in this setting, we conclude that aNK-DLI contributed to the acute GVHD observed, likely by augmenting underlying T-cell alloreactivity. This trial was registered at www.clinicaltrials.gov as #NCT01287104.

α-1-Antitrypsin (AAT)-modified donor cells suppress GVHD but enhance the GVL effect: a role for mitochondrial bioenergetics

Hematopoietic cell transplantation is curative in many patients. However, graft-versus-host disease (GVHD), triggered by alloreactive donor cells, has remained a major complication. Here, we show an inverse correlation between plasma α-1-antitrypsin (AAT) levels in human donors and the development of acute GVHD in the recipients (n = 111; P = .0006). In murine models, treatment of transplant donors with human AAT resulted in an increase in interleukin-10 messenger RNA and CD8(+)CD11c(+)CD205(+) major histocompatibility complex class II(+) dendritic cells (DCs), and the prevention or attenuation of acute GVHD in the recipients. Ablation of DCs (in AAT-treated CD11c-DTR donors) decreased CD4(+)CD25(+)FoxP3(+) regulatory T cells to one-third and abrogated the anti-GVHD effect. The graft-versus-leukemia (GVL) effect of donor cells (against A20 tumor cells) was maintained or even enhanced with AAT treatment of the donor, mediated by an expanded population of NK1.1(+), CD49B(+), CD122(+), CD335(+) NKG2D-expressing natural killer (NK) cells. Blockade of NKG2D significantly suppressed the GVL effect. Metabolic analysis showed a high glycolysis-high oxidative phosphorylation profile for NK1.1(+) cells, CD4(+)CD25(+)FoxP3(+) T cells, and CD11c(+) DCs but not for effector T cells, suggesting a cell type-specific effect of AAT. Thus, via altered metabolism, AAT exerts effective GVHD protection while enhancing GVL effects.

Aerosol interleukin-2 induces natural killer cell proliferation in the lung and combination therapy improves the survival of mice with osteosarcoma lung metastasis

BACKGROUND

We have previously shown that aerosol interleukin-2 (IL-2) increased the number of intravenously injected human natural killer (NK) cells in the lungs. In this study we investigated whether this increase was secondary to NK cell proliferation and determined the site of the proliferation.

MATERIALS AND METHODS

Nude mice with osteosarcoma lung metastases were injected with NK cells and treated with aerosol IL-2 or aerosol PBS. BrdU was injected prior to euthanasia to identify proliferating NK cells. The percentage of proliferating NK cells in the lung, bone marrow, spleen, and liver was determined using flow cytometry. Survival studies for mice with osteosarcoma lung metastasis treated with aerosol PBS, aerosol IL-2 alone, aerosol PBS plus NK cells, and aerosol IL-2 plus NK cells were also performed.

RESULTS

Treatment with aerosol IL-2 induced the proliferation of injected NK cells in the lung. Aerosol IL-2 did not increase the proliferation of NK cells in the spleen and liver. Treatment with aerosol IL-2 and aerosol IL-2 plus NK cells increased the overall survival of mice with osteosarcoma lung metastasis.

CONCLUSION

Aerosol IL-2 increases lung NK cell numbers by stimulating local NK cell proliferation. Aerosol IL-2's effect on NK cell proliferation is organ specific, which makes it ideal for the specific targeting of lung metastasis. Aerosol IL-2 plus NK cell therapy induced metastatic regression and increased overall survival demonstrating the potential of this therapeutic approach for patients with osteosarcoma.

KIR haplotype B donors but not KIR-ligand mismatch result in a reduced incidence of relapse after haploidentical transplantation using reduced intensity conditioning and CD3/CD19-depleted grafts

Natural killer (NK)-cell alloreactivity after allogeneic hematopoietic cell transplantation (HCT) is influenced by the interaction of killer-cell immunoglobulin-like receptors (KIRs) on donor NK cells and human leukocyte antigen (HLA) class I ligands on recipient cells. We investigated the influence of donor KIR haplotype and KIR-ligand mismatch (MM) on relapse in 57 patients with hematologic malignancies receiving haploidentical HCT after reduced intensity conditioning and graft CD3/CD19 depletion. Of the 57 donors, 17 had KIR haplotype A (29.8 %) and 40 had KIR haplotype B (70.2 %). A KIR-ligand MM was found in 34 of 57 patients (59.6 %). There was no difference between donor KIR haplotypes in non-relapse mortality (NRM, p = 0.200) but had a significantly reduced incidence of relapse for patients with a haplotype B donor (p = 0.001). In particular, patients in partial remission (PR) benefited more from a haplotype B graft (p = 0.008) than patients in complete remission (CR, p = 0.297). Evaluating KIR-ligand MM cumulative incidences of relapse (p = 0.680) or NRM (p = 0.579), we found no significant difference. In conclusion, in the setting of reduced intensity conditioning (RIC) and CD3/CD19-depleted haploidentical HCT, we could not confirm the positive data with KIR-ligand MM but observed a significant lower risk of relapse with a KIR haplotype B donor.

Improving the outcome of leukemia by natural killer cell-based immunotherapeutic strategies

Blurring the boundary between innate and adaptive immune system, natural killer (NK) cells are widely recognized as potent anti-leukemia mediators. Alloreactive donor NK cells have been shown to improve the outcome of allogeneic stem-cell transplantation for leukemia. In addition, in vivo transfer of NK cells may soon reveal an important therapeutic tool for leukemia, if tolerance to NK-mediated anti-leukemia effects is overcome. This will require, at a minimum, the ex vivo generation of a clinically safe NK cell product containing adequate numbers of NK cells with robust anti-leukemia potential. Ideally, ex vivo generated NK cells should also have similar anti-leukemia potential in different patients, and be easy to obtain for convenient clinical scale-up. Moreover, optimal clinical protocols for NK therapy in leukemia and other cancers are still lacking. These and other issues are being currently addressed by multiple research groups. This review will first describe current laboratory NK cell expansion and differentiation techniques by separately addressing different NK cell sources. Subsequently, it will address the mechanisms known to be responsible for NK cell alloreactivity, as well as their clinical impact in the hematopoietic stem cells transplantation setting. Finally, it will briefly provide insight on past NK-based clinical trials.

Chimerism in children with primary immunodeficiencies is influenced by number of activating killer cell immunoglobulin-like receptor genes in the donor and/or killer cell immunoglobulin-like receptor ligand mismatch

BACKGROUND

Stem cell transplantation (SCT) is a curative treatment for children with primary immunodeficiencies.

METHODS

The present retrospective analysis describes the long-term outcomes at a median follow-up of 9 years of 29 patients with immunodeficiency after SCT; 5 sibling and 24 alternative donor transplantations. T-cell engraftment emphazed on thymic dependent signal-joint T-cell receptor excision circles (sjTREC) generation and donor chimerism in relation to killer cell immunoglobulin-like receptor genes and their ligands.

RESULTS

All children except two were reconstituted successfully from grafted material, including 9 and 18 cases of mixed chimerism (MC) and complete chimerism (CC), respectively. Univariate analyses showed that the number of activating KIR genes or HLA-C1/C2 ligand mismatches (P = .048) and possibly transplantation from an alternative donor (P = .054) facilitated CC development. Multivariate analysis showed that the presence of donor KIR haplotype B or incompatibility within C1/C2 ligands (relative risk, 6.1; 95% confidence interval, 1.08-34.69; P = .025) were significantly associated with the development of CC.

CONCLUSIONS

These results suggested that the donor-activating KIR gene repertoire affected successful engraftment.

Effect of donor KIR2DL1 allelic polymorphism on the outcome of pediatric allogeneic hematopoietic stem-cell transplantation

PURPOSE

Killer-cell immunoglobulin-like receptors (KIRs) that regulate natural-killer cells are highly polymorphic. Some KIR2DL1 alleles encode receptors that have stronger signaling function than others. We tested the hypothesis that the clinical outcomes of allogeneic hematopoietic stem-cell transplantation (HSCT) could be affected by donor KIR2DL1 polymorphism.

PATIENTS AND METHODS

All 313 pediatric patients received allogeneic HSCT at a single institution. Donor KIR2DL1 functional allele typing was retrospectively performed using single nucleotide polymorphism assay.

RESULTS

Patients who received a donor graft containing the functionally stronger KIR2DL1 allele with arginine at amino acid position 245 (KIR2DL1-R(245)) had better survival (P = .0004) and lower cumulative incidence of disease progression (P = .001) than those patients who received a donor graft that contained only the functionally weaker KIR2DL1 allele with cysteine at the same position (KIR2DL1-C(245)). The effect of KIR2DL1 allelic polymorphism was similar in patients with acute myeloid leukemia or acute lymphoblastic leukemia among all allele groups (P ≥ .71). Patients who received a KIR2DL1-R(245)-positive graft with HLA-C receptor-ligand mismatch had the best survival (P = .00003) and lowest risk of leukemia progression (P = .0005) compared with those who received a KIR2DL1-C(245) homozygous graft.

CONCLUSION

Donor KIR2DL1 allelic polymorphism affects recipient outcomes after allogeneic HSCT. These findings have substantial implications for prognostication and donor selection.

Dissecting graft-versus-leukemia from graft-versus-host-disease using novel strategies

The intrinsic anti-leukemic effect of allogeneic hematopoietic cell transplantation (HCT) is dependent on genetic disparity between donor and recipient, intimately associated with graft-versus-host disease (GVHD), and mediated by lymphocytes contained in or derived from the donor hematopoietic cell graft. Three decades of intense effort have not identified clinical strategies that can reliably separate the graft-versus-leukemia (GVL) effect from the alloimmune reaction that drives clinical GVHD. For patients who require HCT and for whom two or more human leukocyte antigen (HLA)-A, -B, -C, and -DRB1-matched donor candidates can be identified, consideration of donor and recipient genotype at additional genetic loci both within and outside the major histocompatibility complex may offer the possibility of selecting the donor [candidate(s)] that poses the lowest probability of GVHD and the highest probability of a potent GVL effect. Strategies for engineering conventional donor lymphocyte infusion also hold promise for prevention or improved treatment of post-transplant relapse. The brightest prospects for selectively enhancing the anti-leukemic efficacy of allogeneic HCT, however, are likely to be interventions that are designed to enhance specific antitumor immunity via vaccination or adoptive cell transfer, rather than those that attempt to exploit donor alloreactivity against the host. Adoptive transfer of donor-derived T cells genetically modified for tumor-specific reactivity, in particular, has the potential to transform the practice of allogeneic HCT by selectively enhancing antitumor immunity without causing GVHD.

Inhibitory KIR/HLA incompatibility between sexual partners confers protection against HIV-1 transmission

Killer immunoglobulin-like receptors (KIRs) regulate natural killer (NK) cells in a human leukocyte antigen (HLA)-dependent manner. KIR/HLA mismatched hematopoietic stem cell transplants induce alloreactive NK cells, which prevent leukemia relapse. Certain KIR/HLA combinations protect against HIV-1 infection, but the effect of KIR/HLA mismatches between sexual partners has never been investigated. In this study, we analyzed the effect of allogeneic KIR/HLA combinations on HIV-1 transmission in a West African population of HIV-1-discordant and concordant couples. HIV-1-discordant couples were characterized by recipient partners with homozygous KIR2DL2, and by a mismatched recipient partner KIR2DL1/HLA-C2 with index partner HLA-C1/C1 combination expected to allow licensed missing self NK cell killing of index partners' cells. HIV-1-concordant couples on the other hand were characterized by KIR2DL3 homozygous recipient partners with HLA-C1/C2 bearing index partners, resulting in a matched KIR/HLA combination expected to inhibit NK cell killing. In vitro cocultures of healthy donor-derived NK cells and HIV-1 patient-derived CD4(+) T cells confirmed the involvement of these allogeneic KIR/HLA combinations in NK cell-mediated CD4(+) T-cell killing. Our data suggest that KIR/HLA incompatibility between sexual partners confers protection against HIV-1 transmission and that this may be due to alloreactive NK cell killing of the HIV-1-infected partner's cells.

Role of KIR3DS1 in human diseases

The function of natural killer (NK) cells is controlled by several activating and inhibitory receptors, including the family of killer-immunoglobulin-like receptors (KIRs). One distinctive feature of KIRs is the extensive number of various haplotypes generated by the gene content within the KIR gene locus as well as by highly polymorphic members of the KIR gene family, namely KIR3DL1/S1. Within the KIR3DL1/S1 gene locus, KIR3DS1 represents a conserved allelic variant and displays other unique features in comparison to the highly polymorphic KIR3DL1 allele. KIR3DS1 is present in all human populations and belongs to the KIR haplotype group B. KIR3DS1 encodes for an activating receptor featuring the characteristic short cytoplasmic tail and a positively charged residue within the transmembrane domain, which allows recruitment of the ITAM-bearing adaptor molecule DAP12. Although HLA class I molecules are thought to represent natural KIR ligands, and HLA-Bw4 molecules serve as ligands for KIR3DL1, the ligand for KIR3DS1 still needs to be identified. Despite the lack of formal evidence for an interaction of KIR3DS1 with HLA-Bw4-I80 or any other HLA class I subtype to date, a growing number of associations between the presence of KIR3DS1 and the outcome of viral infections have been described. Especially, the potential protective role of KIR3DS1 in combination with HLA-Bw4-I80 in the context of HIV-1 infection has been studied intensively. In addition, a number of recent studies have associated the presence or absence of KIR3DS1 with the occurrence and outcome of some malignancies, autoimmune diseases, and graft-versus-host disease (GVHD). In this review, we summarize the present knowledge regarding the characteristics of KIRD3S1 and discuss its role in various human diseases.

Targeting natural killer cells and natural killer T cells in cancer

Natural killer (NK) cells and natural killer T (NKT) cells are subsets of lymphocytes that share some phenotypical and functional similarities. Both cell types can rapidly respond to the presence of tumour cells and participate in antitumour immune responses. This has prompted interest in the development of innovative cancer therapies that are based on the manipulation of NK and NKT cells. Recent studies have highlighted how the immune reactivity of NK and NKT cells is shaped by the environment in which they develop. The rational use of these cells in cancer immunotherapies awaits a better understanding of their effector functions, migratory patterns and survival properties in humans.

Use of NK cell activity in cure by transplant

Analogous to T cells, Natural Killer (NK) cells may facilitate engraftment, combat infection, and control cancer in bone marrow or haematopoietic stem cell transplantation (HSCT); however, NK cells do not cause graft-versus-host disease. Killer immunoglobulin-like receptors (KIRs) regulate NK cell function, and recent data suggest that KIR is as important as its ligand (human leucocyte antigen; HLA) in HSCT for both malignant and non-malignant conditions. Because there is substantial variability in KIR gene content, allelic polymorphism, and cell-surface expression among people, careful selection of donors based on HLA and KIR is essential to optimize HSCT outcomes. Furthermore, NK cells may be used for adoptive immunotherapy after HSCT in place of conventional donor lymphocyte infusion, as part of pre-transplant cytoreductive therapy, or as an independent therapeutic agent in high-risk leukaemia in place of sibling donor HSCT.