CD19-chimeric antigen receptor-invariant natural killer T cells transactivate NK cells and reduce alloreactivity.

Invariant natural killer T (iNKT) cells are a small fraction of T lymphocytes with strong cytotoxic and immunoregulatory properties. We previously showed that human culture-expanded iNKT cells prevent alloreactivity and lyse primary leukemia blasts. Here, iNKT cells have several advantages over T cells based on their immunoregulatory capabilities. Since chimeric antigen receptors (CARs) increase the benefit of immune effector cells, they play a crucial role in improvement of cytotoxic abilities of novel cellular therapeutics such as iNKT cells. In the present study, we investigated transactivation of NK cells and prevention of alloreactivity through iNKT cells transduced with a CD19-directed CAR. iNKT cells were isolated by magnetic cell separation from peripheral blood mononuclear cells and transduced with a CD19-CAR retrovirus. Transduction efficiency, purity and cell subsets were measured by flow cytometry. Transactivation and cytotoxicity assays have been established to investigate the ability of CD19-CAR-iNKT cells to transactivate primary NK cells. A mixed lymphocyte reaction (MLR) was performed to explore the inhibition of alloreactive CD3+ T cells by CD19-CAR-iNKT cells. CD19-CAR-iNKT cells are able to transactivate NK cells independent of cell contact: The expression of activation marker CD69 was significantly increased and also production of the proinflammatory cytokine interferon-gamma was higher in NK cells pretreated with CD19-CAR-iNKT cells. Consequently, the cytotoxic activity of such NK cells was significantly increased being able to lyse leukemia cells more effectively than without prior transactivation. Adding CD19-CAR-iNKT cells to an MLR resulted in a decreased expression of the T cell activation marker CD25 on alloreactive CD3+ T lymphocytes stimulated with HLA mismatched dendritic cells. Also, the proliferation of alloreactive CD3+ T lymphocytes was significantly reduced in this setting. We demonstrate that CD19-CAR-iNKT cells keep their immunoregulatory properties despite transduction with a CAR making them an attractive effector cell population for application after allogeneic hematopoietic cell transplantation. By transactivating NK cells, increasing their cytotoxic activity and suppressing alloreactive T cells, they might further improve outcomes through prevention of both relapse and graft-versus-host disease.

Delayed drug hypersensitivity reactions: How p-i transforms pharmacology into immunology.

Delayed drug hypersensitivity reactions (dDHRs) are iatrogenic diseases, which are mostly due to non-covalent interactions of a drug with the immune receptors HLA and/or TCR causing T-cell activation. This is also known as pharmacological interaction with immune receptors or p-i. P-i activation differs from classical antigen-driven immune reactions: a) drug binding induces structural changes in TCR-HLA proteins which make them look like allo-like TCR-HLA-complexes, able to elicit allo-like stimulations of T cells with cytotoxicity and IFNγ production, notably without the involvement of innate immunity; b) drug binding to TCR and/or HLA can increase the affinity of TCR-HLA interactions, which may affect signaling and IL-5 production by CD4+ T cells, and thus contribute to eosinophilia commonly found in dDHRs or induce oligoclonal T cell expansions; c) Both, antigen and p-i stimulations can induce eosinophil- or neutrophil-rich inflammations; but these stimulations should be distinguished as their underlying mechanism and development differ; and d) p-i stimulation can - like graft versus host reactions - result in long-lasting T-cell activations, which can lead to viremia, occasional autoimmunity, or a new syndrome characterized by multiple drug hypersensitivity (MDH). In summary, dDHRs are not allergic reactions but represent peculiar T-cell activations, similar to allo-like stimulations. Understanding and considering the p-i mechanism is needed for preventive measures and optimal treatments of dDHR. In addition, it may help to understand TCR signaling, alloreactivity, and may even open a new way of specific immune stimulations.

Alloreactive memory CD4 T cells promote transplant rejection by engaging DCs to induce innate inflammation and CD8 T cell priming.

Alloreactive memory T cells have been implicated as central drivers of transplant rejection. Perplexingly, innate cytokines, such as IL-6, IL-1ß, and IL-12, are also associated with rejection of organ transplants. However, the pathways of innate immune activation in allogeneic transplantation are unclear. While the role of microbial and cell death products has been previously described, we identified alloreactive memory CD4 T cells as the primary triggers of innate inflammation. Memory CD4 T cells engaged MHC II-mismatched dendritic cells (DCs), leading to the production of innate inflammatory cytokines. This innate inflammation was independent of several pattern recognition receptors and was primarily driven by TNF superfamily ligands expressed by alloreactive memory CD4 T cells. Blocking of CD40L and TNFα resulted in dampened inflammation, and mice genetically deficient in these molecules exhibited prolonged survival of cardiac allografts. Furthermore, myeloid cell and CD8 T cell infiltration into cardiac transplants was compromised in both CD40L- and TNFα-deficient recipients. Strikingly, we found that priming of naive alloreactive CD8 T cells was dependent on licensing of DCs by memory CD4 T cells. This study unravels the key mechanisms by which alloreactive memory CD4 T cells contribute to destructive pathology and transplant rejection.

Pretransplant, Th17 dominant alloreactivity in highly sensitized kidney transplant candidates.

Introduction: Sensitization to donor human leukocyte antigen (HLA) molecules prior to transplantation is a significant risk factor for delayed access to transplantation and to long-term outcomes. Memory T cells and their cytokines play a pivotal role in shaping immune responses, thereby increasing the risk of allograft rejection among highly sensitized patients. This study aims to elucidate the precise contribution of different CD4+ memory T cell subsets to alloreactivity in highly sensitized (HS) kidney transplant recipients. Methods and results: Stimulation of peripheral blood mononuclear cells (PBMC) with various polyclonal stimulating agents to assess non-specific immune responses revealed that HS patients exhibit elevated immune reactivity even before kidney transplantation, compared to non-sensitized (NS) patients. HS patients' PBMC displayed higher frequencies of CD4+ T cells expressing IFNγ, IL4, IL6, IL17A, and TNFα and secreted relatively higher levels of IL17A and IL21 upon stimulation with PMA/ionomycin. Additionally, PBMC from HS patients stimulated with T cell stimulating agent phytohemagglutinin (PHA) exhibited elevated expression levels of IFNγ, IL4 and, IL21. On the other hand, stimulation with a combination of resiquimod (R848) and IL2 for the activation of memory B cells demonstrated higher expression of IL17A, TNFα and IL21, as determined by quantitative real-time PCR. A mixed leukocyte reaction (MLR) assay, employing third-party donor antigen presenting cells (APCs), was implemented to evaluate the direct alloreactive response. HS patients demonstrated notably higher frequencies of CD4+ T cells expressing IL4, IL6 and IL17A. Interestingly, APCs expressing recall HLA antigens triggered a stronger Th17 response compared to APCs lacking recall HLA antigens in sensitized patients. Furthermore, donor APCs induced higher activation of effector memory T cells in HS patients as compared to NS patients. Conclusion: These results provide an assessment of pretransplant alloreactive T cell subsets in highly sensitized patients and emphasize the significance of Th17 cells in alloimmune responses. These findings hold promise for the development of treatment strategies tailored to sensitized kidney transplant recipients, with potential clinical implications.

Combination cell therapy leads to clonal deletion of donor-specific T cells in kidney transplant recipients.

BACKGROUND: Induction of donor-specific tolerance is a promising approach to achieve long-term graft patency in transplantation with little to no maintenance immunosuppression. Changes to the recipient's T cell receptor (TCR) repertoire are understood to play a pivotal role in the establishment of a robust state of tolerance in chimerism-based transplantation protocols. METHODS: We investigated changes to the TCR repertoires of patients participating in an ongoing prospective, controlled, phase I/IIa trial designed to evaluate the safety and efficacy of combination cell therapy in living donor kidney transplantation. Using high-throughput sequencing, we characterized the repertoires of six kidney recipients who also received bone marrow from the same donor (CKBMT), together with an infusion of polyclonal autologous Treg cells instead of myelosuppression. FINDINGS: Patients undergoing combination cell therapy exhibited partial clonal deletion of donor-reactive CD4+ T cells at one, three, and six months post-transplant, compared to control patients receiving the same immunosuppression regimen but no cell therapy (p = 0.024). The clonality, R20 and turnover rates of the CD4+ and CD8+ TCR repertoires were comparable in both groups, showing our protocol caused no excessive repertoire shift or loss of diversity. Treg clonality was lower in the case group than in control (p = 0.033), suggesting combination cell therapy helps to preserve Treg diversity. INTERPRETATION: Overall, our data indicate that combining Treg cell therapy with CKBMT dampens the alloimmune response to transplanted kidneys in humans in the absence of myelosuppression. FUNDING: This study was funded by the Vienna Science and Technology Fund (WWTF).

Future directions in haploidentical hematopoietic stem cell transplantation.

Outcomes of haploidentical hematopoietic stem cell transplantation (haplo-SCT) have improved over time. Graft failure and graft-versus-host disease (GVHD), which were important complications in major human leukocyte antigen (HLA)-disparity stem cell transplantation, have significantly decreased. These improvements have led to an exponential increase in the use of haploidentical donors for transplantation, as well as in the number of publications evaluating haplo-SCT outcomes. Many studies focused on factors important in donor selection, novel conditioning regimens or GVHD prophylaxis, the impact of donor-specific anti-HLA antibodies (DSA), as well as strategies to prevent disease relapse post-transplant. DSA represents an important limitation and multimodality desensitization protocols, including plasma exchange, rituximab, intravenous immunoglobulin and donor buffy coat infusion, can contribute to the successful engraftment in patients with high DSA levels and is currently the standard therapy for highly allosensitized individuals. With regards to donor selection, younger donors are preferred due to lower risk of complications and better transplant outcomes. Moreover, recent studies also showed that younger haploidentical donors may be a better choice than older-matched unrelated donors. Improvement of disease relapse remains a top priority, and several studies have demonstrated that higher natural killer (NK) cell numbers early post-transplant are associated with improved outcomes. Prospective studies have started to assess the role of NK cell administration in decreasing post-transplant relapse. These studies suggest that the incorporation of other cell products post-transplant, including the administration of chimeric antigen receptor T-cells, should be explored in the future.

The role and novel use of natural killer cells in graft-versus-leukemia reactions after allogeneic transplantation.

Allogeneic hematopoietic cell transplantation (HCT) has transformed over the past several decades through enhanced supportive care, reduced intensity conditioning (RIC), improved human leukocyte antigen (HLA) typing, and novel graft-versus-host disease (GVHD)-prevention and treatment strategies. Most notably, the implementation of post-transplantation cyclophosphamide (PTCy) has dramatically increased the safety and availability of this life-saving therapy. Given reductions in nonrelapse mortality (NRM) with these advances, the HCT community has placed even greater emphasis on developing ways to reduce relapse - the leading cause of death after HCT. When using RIC HCT, protection from relapse relies predominantly on graft-versus-leukemia (GVL) reactions. Donor lymphocyte infusion (DLI), adoptive cellular therapy, checkpoint inhibition, and post-HCT maintenance strategies represent approaches under study that aim to augment or synergize with the GVL effects of HCT. Optimizing donor selection algorithms to leverage GVL represents another active area of research. Many of these strategies seek to harness the effects of T cells, which for decades were felt to be the primary mediators of GVL and the focus of investigation in relapse reduction. However, there is growing interest in capitalizing on the ability of natural killer (NK) cells to yield potent anti-tumor effects. A potential advantage of NK cell-based approaches over T cell-mediated is the potential to reduce NRM in addition to relapse. By decreasing infection, without increasing the risk of GVHD, NK cells may mitigate NRM, while still yielding relapse reduction through identification and clearance of cancer cells. Most T cell-focused relapse-prevention strategies must weigh the benefits of relapse reduction against the increased risk of NRM from GVHD. In contrast, NK cells have the potential to reduce both, potentially tipping the scales significantly in favor of survival. Here, we will review the role of NK cells in GVL, optimization of NK cell match or mismatch, and burgeoning areas of research in NK cell therapy such as adoptive transfer and chimeric antigen receptor (CAR) NK cells.

Tissue-resident memory T cells in human kidney transplants have alloreactive potential.

The extent to which tissue-resident memory T (TRM) cells in transplanted organs possess alloreactivity is uncertain. This study investigates the alloreactive potential of TRM cells in kidney explants from 4 patients who experienced severe acute rejection leading to graft loss. Alloreactive T cell receptor (TCR) clones were identified in pretransplant blood samples through mixed lymphocyte reactions, followed by single-cell RNA and TCR sequencing of the proliferated recipient T cells. Subsequently, these TCR clones were traced in the TRM cells of kidney explants, which were also subjected to single-cell RNA and TCR sequencing. The proportion of recipient-derived TRM cells expressing an alloreactive TCR in the 4 kidney explants varied from 0% to 9%. Notably, these alloreactive TCRs were predominantly found among CD4+ and CD8+ TRM cells with an effector phenotype. Intriguingly, these clones were present not only in recipient-derived TRM cells but also in donor-derived TRM cells, constituting up to 4% of the donor population, suggesting the presence of self-reactive TRM cells. Overall, our study demonstrates that T cells with alloreactive potential present in the peripheral blood prior to transplantation can infiltrate the kidney transplant and adopt a TRM phenotype.

The balance between memory and regulatory cell populations in kidney transplant recipients with operational tolerance.

Donor-reactive memory cells represent a barrier to long-term kidney graft survival. A better understanding of regulatory mechanisms that counterbalance alloreactive memory responses may help to identify patients with operational tolerance. This prospective study investigated the equilibrium between memory T-cell subsets and regulatory T or B cells (Tregs, Bregs) in peripheral blood of kidney transplant recipients with operational tolerance (N = 8), chronic rejection (N = 8), and different immunosuppressive treatment regimens (N = 81). Patients on hemodialysis and healthy individuals served as controls (N = 50). In addition, the expression of Treg- and Breg-associated molecule genes was analyzed. Patients with chronic rejection showed a disrupted memory T-cell composition with a significantly higher frequency of circulating CD8+ terminally differentiated effector memory (TEMRA) T cells than patients with operational tolerance, patients on hemodialysis, or healthy controls (P < 0.001). Low frequency of CD8+ TEMRA and high frequency of Tregs and transitional Bregs were found in operationally tolerant patients. Consequently, operationally tolerant patients showed, as compared to all other transplant recipients with different immunosuppressive regiments, the lowest ratios between CD8+ TEMRA T cells and Tregs or Bregs (for both P < 0.001). Moreover, a specific peripheral blood transcription pattern was found in operationally tolerant patients with an increased expression of Breg- and Treg-associated genes CD22 and FoxP3 and a decreased FcγRIIA/FcγRIIB transcript ratio (for all P < 0.001). In conclusion, monitoring the balance between circulating CD8+ TEMRA T cells and regulatory cell subsets and their transcripts may help to distinguish transplant recipients with operational tolerance from recipients at risk of graft loss.

Cord Blood-Derived Multipotent Stem Cells Ameliorate in Vitro/in Vivo Alloreactive Responses, and This Effect Is Associated with Exosomal Microvesicles in Vitro.

Human cord blood derived-multipotent stem cells (CB-SCs) have been found to have immunomodulatory capabilities that can result in inhibition of immune activation. Clinically, when used to interact with apheresed peripheral blood mononuclear cells (PBMCs) before reinfusion, they can counteract inflammation and restore immune balance in patients with autoimmune diseases, including alopecia areata and type 1 diabetes. The present study aimed to explore the potential application of CB-SCs to control donor alloreactive responses involved in allogeneic hematopoietic cell transplantation, which often results in acute graft-versus-host disease (GVHD). Phenotypically, we demonstrated that CB-SCs express CD45, CD11b, and CD9 markers on the cell surface; express Oct3/4, a transcription factor for embryonic stem cells; are negative for CD3, CD14, and CD34 expression; and have low expression of HLA-DR. In an allogeneic mixed lymphocyte culture (MLC) using human CD4 T cell enriched PBMCs and allogeneic myeloid derived dendritic cells, direct coculture with CB-SCs decreased CD4 T cell proliferation and activation, as evidenced by a marked decrease in the expression of the late activation markers CD25 and HLA-DR and a reduction of the PKH26 cell proliferation membrane lipophilic marker. Cytokine profiling of MLC supernatants revealed decreased concentrations of inflammatory proteins, including IFN-γ, IL-17, IL-13, IL-2, IL-6, and MIP1-α, along with marked increases in IL-1RA, IP-10, and MCP-1 concentrations in the presence of CB-SCs. Furthermore, transwell MLC experiments revealed that a soluble component was partially responsible for the immunomodulatory effects of CB-SCs. In this regard, exosomal microvesicles (EVs) positive for CD9, CD63, and CD81 were found in CB-SC-derived, ultrafiltered, and ultracentrifuged culture supernatants. CB-SC-EVs inhibited T cell proliferation in allogeneic MLC, suggesting a potential mode of action in allogeneic responses. Finally, CB-SCs were evaluated for their cellular therapy potential in vivo and found to ameliorate the development of GVHD responses in a xenogeneic human PBMC-induced NSG mouse model. Taken together, our results indicate that CB-SCs can directly and indirectly attenuate alloreactive CD4 T cell activation and proliferation in vitro with a potentially related EV mode of action and may have potential as a cellular therapy to control donor T cell-mediated GVHD responses in vivo.

Development of optimized cytotoxicity assays for assessing the antitumor potential of CAR-T cells.

CAR-T cells are T cells expressing a chimeric antigen receptor (CAR) rendering them capable of killing tumor cells after recognition of a target antigen. CD19 CAR-T cells have revolutionized the treatment of hematological malignancies. Their function is typically assessed by cytotoxicity assays using human allogeneic cell lines expressing the target antigen CD19 such as Nalm-6. However, an alloreactive reaction is observed with these cells, leading to a CD19-independent killing. To address this issue, we developed a fluorescence microscopy-based potency assay using murine target cells to provide an optimized cytotoxicity assay with enhanced specificity towards CD19. Murine NIH/3T3 (3T3) fibroblast-derived cell line and EL4 T-cell lymphoma-derived cell line were used as targets (no xenoreactivity was observed after coculture with human T cells). 3T3 and EL4 cells were engineered to express eGFP (enhanced Green Fluorescent Protein) and CD19 or CD22 using retroviral vectors. CD19 CAR-T cells and non-transduced (NT) control T cells were produced from several donors. After 4 h or 24 h, alloreactive cytotoxicity against CD19+ Nalm-6-GFP cells and CD19- Jurkat-GFP cells was observed with NT or CAR-T cells. In the same conditions, CAR-T but not NT cells specifically killed CD19+ but not CD19- 3T3-GFP or EL4-GFP cells. Both microscope- and flow cytometry-based assays revealed as sensitive as impedance-based assay. Using flow cytometry, we could further determine that CAR-T cells had mostly a stem cell-like memory phenotype after contact with EL4 target cells. Therefore, CD19+ 3T3-GFP or EL4-GFP cells and fluorescence microscopy- or flow cytometry-based assays provide convenient, sensitive and specific tools to evaluate CAR-T cell function with no alloreactivity.

TCR Sequencing in Mouse Models of Allorecognition Unveils the Features of Directly and Indirectly Activated Clonotypes.

Allorecognition is known to involve a large number of lymphocytes carrying diverse T-cell receptor repertoire. Thus, one way to understand allorecognition and rejection mechanisms is via high-throughput sequencing of T-cell receptors. In this study, in order to explore and systematize the properties of the alloreactive T-cell receptor repertoire, we modeled direct and indirect allorecognition pathways using material from inbred mice in vitro and in vivo. Decoding of the obtained T-cell receptor genes using high-throughput sequencing revealed some features of the alloreactive repertoires. Thus, alloreactive T-cell receptor repertoires were characterized by specific V-gene usage patterns, changes in CDR3 loop length, and some amino acid occurrence probabilities in the CDR3 loop. Particularly pronounced changes were observed for directly alloreactive clonotypes. We also revealed a clustering of directly and indirectly alloreactive clonotypes by their ability to bind a single antigen; amino acid patterns of the CDR3 loop of alloreactive clonotypes; and the presence in alloreactive repertoires of clonotypes also associated with infectious, autoimmune, and tumor diseases. The obtained results were determined by the modeling of the simplified allorecognition reaction in inbred mice in which stimulation was performed with a single MHCII molecule. We suppose that the decomposition of the diverse alloreactive TCR repertoire observed in humans with transplants into such simple reactions will help to find alloreactive repertoire features; e.g., a dominant clonotype or V-gene usage pattern, which may be targeted to correct the entire rejection reaction in patients. In this work, we propose several technical ways for such decomposition analysis, including separate modeling of the indirect alloreaction pathway and clustering of alloreactive clonotypes according to their ability to bind a single antigen, among others.

KIR2DS4 and Its Variant KIR1D in KIR-AA Genotype Donors Showed Differential Survival Impact in Patients with Lymphoid Disease after HLA-Matched Unrelated Hematopoietic Stem Cell Transplantation.

Previous studies have illustrated associations between the presence of activating killer cell immunoglobulin-like receptor (KIR) genes and lower susceptibility to hematologic malignancies in humans. In addition, favorable hematopoietic stem cell transplantation (HSCT) outcomes have been reported in patients who received transplants from donors with KIR genotypes dominant for activating KIR receptors. However, the association of activating KIR genes on an allelic level with disease and their impact on HSCT outcome has been little investigated to date. To this end, we genotyped a large transplantation cohort for KIR 2 Ig domains and short cytoplasmic tail 4 (KIR2DS4) polymorphisms and investigated their association with disease. We next investigated the impact of KIR-AA genotype donor KIR2DS4 polymorphisms (AA/KIR2DS4 versus AA/ KIR 1 Ig domain [KIR1D]) on clinical outcomes of HSCT in myeloid versus lymphoid patient subgroups. Among 2810 transplantation donor-recipient pairs, 68.8% (n = 1934) were 10/10 HLA-matched and 31.2% (n = 876) were 9/10 HLA-matched. The distribution of KIR1D was equal in patients and donors (P = .205). Multivariate analysis in 10/10 HLA-matched patients with lymphoid disease showed improved HSCT outcomes when they received grafts from AA/KIR1D donors (overall survival: hazard ratio [HR], .62, P = .002; disease free survival: HR, .70, P = .011; graft-versus-host disease-free and relapse-free survival: HR, .67, P = .002; nonrelapse mortality: HR, .55, P < .001). This effect was not seen in either 9/10 HLA-matched patients with lymphoid disease or patients with myeloid disease. Our study indicates that the presence of KIR1D alleles is not associated with disease in patients, and, interestingly, using grafts from AA/KIR1D donors translated into beneficial survival outcomes in 10/10 HLA-matched patients with lymphoid disease.

Structural basis of the TCR-pHLA complex provides insights into the unconventional recognition of CDR3ß in TCR cross-reactivity and alloreactivity.

Evidence shows that some class I human leucocyte antigen (HLA) alleles are related to durable HIV controls. The T18A TCR, which has the alloreactivity between HLA-B∗42:01 and HLA-B∗81:01 and the cross-reactivity with different antigen mutants, can sustain long-term HIV controls. Here the structural basis of the T18A TCR binding to the immunodominant HIV epitope TL9 (TPQDLNTML180-188) presented by HLA-B∗42:01 was determined and compared to T18A TCR binding to the TL9 presented by the allo-HLA-B∗81:01. For differences between HLA-B∗42:01 and HLA-B∗81:01, the CDR1α and CDR3α loops adopt a small rearrangement to accommodate them. For different conformations of the TL9 presented by different HLA alleles, not like the conventional recognition of CDR3s to interact with peptide antigens, CDR3ß of the T18A TCR shifts to avoid the peptide antigen but intensively recognizes the HLA only, which is different with other conventional TCR structures. Featured sequence pairs of CDR3ß and HLA might account for this and were additionally found in multiple other diseases indicating the popularity of the unconventional recognition pattern which would give insights into the control of diseases with epitope mutating such as HIV.

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.

Genetic engineering strategies to enhance antitumor reactivity and reduce alloreactivity for allogeneic cell-based cancer therapy.

The realm of cell-based immunotherapy holds untapped potential for the development of next-generation cancer treatment through genetic engineering of chimeric antigen receptor (CAR)-engineered T (CAR-T) cell therapies for targeted eradication of cancerous malignancies. Such allogeneic "off-the-shelf" cell products can be advantageously manufactured in large quantities, stored for extended periods, and easily distributed to treat an exponential number of cancer patients. At current, patient risk of graft-versus-host disease (GvHD) and host-versus-graft (HvG) allorejection severely restrict the development of allogeneic CAR-T cell products. To address these limitations, a variety of genetic engineering strategies have been implemented to enhance antitumor efficacy, reduce GvHD and HvG onset, and improve the overall safety profile of T-cell based immunotherapies. In this review, we summarize these genetic engineering strategies and discuss the challenges and prospects these approaches provide to expedite progression of translational and clinical studies for adoption of a universal cell-based cancer immunotherapy.

Comparison of NK alloreactivity prediction models based on KIR-MHC interactions in haematopoietic stem cell transplantation.

The biological processes underlying NK cell alloreactivity in haematopoietic stem cell transplantation (HSCT) remain unclear. Many different models to predict NK alloreactivity through KIR and MHC genotyping exist, raising ambiguities in its utility and application for clinicians. We assessed 27 predictive models, broadly divided into six categories of alloreactivity prediction: ligand-ligand, receptor-ligand, educational, KIR haplotype-based, KIR matching and KIR allelic polymorphism. The models were applied to 78 NGS-typed donor/recipient pairs undergoing allogeneic HSCT in genoidentical (n=43) or haploidentical (n=35) matchings. Correlations between different predictive models differed widely, suggesting that the choice of the model in predicting NK alloreactivity matters. For example, two broadly used models, educational and receptor-ligand, led to opposing predictions especially in the genoidentical cohort. Correlations also depended on the matching fashion, suggesting that this parameter should also be taken into account in the choice of the scoring strategy. The number of centromeric B-motifs was the only model strongly correlated with the incidence of acute graft-versus-host disease in our set of patients in both the genoidentical and the haploidentical cohorts, suggesting that KIR-based alloreactivity, not MHC mismatches, are responsible for it. To our best knowledge, this paper is the first to experimentally compare NK alloreactivity prediction models within a cohort of genoidentical and haploidentical donor-recipient pairs. This study helps to resolve current discrepancies in KIR-based alloreactivity predictions and highlights the need for deeper consideration of the models used in clinical studies as well as in medical practice.

Donor selection for adoptive immunotherapy with NK cells in AML patients: Comparison between analysis of lytic NK cell clones and phenotypical identification of alloreactive NK cell repertoire.

Natural killer (NK) cell-based adoptive immunotherapy in leukemia patients is an emerging field of interest based on clinical evidence of efficacy and safety. Elderly acute myeloid leukemia (AML) patients have been successfully treated with NK cells from HLA-haploidentical donors, especially when high amounts of alloreactive NK cells were infused. The aim of this study was comparing two approaches to define the size of alloreactive NK cells in haploidentical donors for AML patients recruited in two clinical trials with the acronym "NK-AML" (NCT03955848), and "MRD-NK". The standard methodology was based on the frequency of NK cell clones capable of lysing the related patient-derived cells. The alternative approach consisted of the phenotypic identification of freshly derived NK cells expressing, as inhibitory receptors, only the inhibitory KIR(s) specific for the mismatched KIR-Ligand(s) (HLA-C1, HLA-C2, HLA-Bw4). However, in KIR2DS2+ donors and HLA-C1+ patients, the unavailability of reagents staining only the inhibitory counterpart (KIR2DL2/L3) may lead to an underestimated identification of the alloreactive NK cell subset. Conversely, in the case of HLA-C1 mismatch, the alloreactive NK cell subset could be overestimated due to the ability of KIR2DL2/L3 to recognize with low-affinity also HLA-C2. Especially in this context, the additional exclusion of LIR1-expressing cells might be relevant to refine the size of the alloreactive NK cell subset. We could also associate degranulation assays, using as effector cells IL-2 activated donor peripheral blood mononuclear cells (PBMC) or NK cells upon co-culture with the related patient target cells. The donor alloreactive NK cell subset always displayed the highest functional activity, confirming its identification accuracy by flow cytometry. Despite the phenotypic limitations and considering the proposed corrective actions, a good correlation was shown by the comparison of the two investigated approaches. In addition, the characterization of receptor expression on a fraction of NK cell clones revealed expected but also few unexpected patterns. Thus, in most instances, the quantification of phenotypically defined alloreactive NK cells from PBMC can provide data similar to the analysis of lytic clones, with several advantages, such as a shorter time to achieve the results and, perhaps, higher reproducibility/feasibility in many laboratories.

Effect of lethal total body irradiation on bone marrow chimerism, acute graft-versus-host disease, and tumor engraftment in mouse models: impact of different radiation techniques using low- and high-energy X-rays.

PURPOSE: Effects of X­ray energy levels used for myeloablative lethal total body irradiation (TBI) delivery prior to bone marrow transplantation (BMT) in preclinical mouse models were examined. MATERIALS AND METHODS: In mouse models, single-fraction myeloablative TBI at a lethal dose was delivered using two different X­ray devices, either low (160 kV cabinet irradiator) or high energy (6 MV linear accelerator), before semi-allogeneic hematopoietic stem-cell transplantation (HSCT) to ensure bone marrow (BM) chimerism, graft-versus-host disease (GVHD), and tumor engraftment. Recipient mice were clinically followed for 80 days after bone marrow transplantation (BMT). Flow cytometry was performed to assess donor chimerism and tumor engraftment in recipient mice. RESULTS: Both X­ray irradiation techniques delivered a 10 Gy single fraction of TBI, presented a lethal effect, and could allow near-complete early donor chimerism on day 13. However, low-energy irradiation increased T cells' alloreactivity compared to high-energy irradiation, leading to clinical consequences for GVHD and tumor engraftment outcomes. The alloreactive effect differences might be attributed to the distinction in inflammatory status of irradiated recipients at donor cell infusion (D0). Delaying donor cell administration (D1 after lethal TBI) attenuated T cells' alloreactivity and clinical outcomes in GVHD mouse models. CONCLUSION: Different X­ray irradiation modalities condition T cell alloreactivity in experimental semi-allogeneic BMT. Low-energy X­ray irradiator induces a post-TBI inflammatory burst and exacerbates alloreactive reactions. This technical and biological information should be considered in interpreting GVHD/ graft-versus-leukemia effect results in mice experimental models of BMT.

[Medication adherence in renal transplantation: Evaluation, predictive factors and impact on humoral alloreactivity]. / Adhésion médicamenteuse en greffe rénale : évaluation, facteurs prédictifs et impact sur l'allo-réactivité humorale.

OBJECTIVES: The aims of this study were to assess medication adherence to immunosuppressive treatment in kidney transplanted patients, to identify predictive factors of medication non-adherence and to analyse its impact on the development of Donor Specific Antibodies (DSA) de novo, biomarkers of rejection in transplant recipients. METHODS: A cross-sectional single-centre study was conducted to assess medication adherence to immunosuppressive treatment with the BAASIS (Basel Assessment of Adherence Scale for Immunosuppressives) self-report questionnaire. Univariate and multivariate analyses were performed to determine non-adherence predictive factors and its role in the development of DSA de novo. RESULTS: A total of 212 renal transplanted patients completed the BAASIS questionnaire: 36,3 % were non-adherent to their immunosuppressive treatment. Patient's age and taking azathioprine were independent predictors of non-adherence and "married or living together" family status was a protective factor in the multivariate analysis. Medication non-adherence was associated with DSA de novo development in the multivariate model and it multiplied their risk of development by 3. CONCLUSIONS: This study, which detected a large proportion of patients who did not adhere to immunosuppressive treatment, highlighted non-adherence predictors and showed the association between non-adherence and development of DSA de novo. In case of non-adherent behavior, it is crucial to set up a personalised support for patients with a multidisciplinary approach of therapeutic education, in which the clinical pharmacist has a role.