Several studies suggest that harnessing natural killer (NK) cell reactivity mediated through killer cell immunoglobulin-like receptors (KIRs) could reduce the risk of relapse after allogeneic hematopoietic cell transplantation. Based on one promising model, information on KIR2DS1 and KIR3DL1 and their cognate ligands can be used to classify donors as KIR-advantageous or KIR-disadvantageous. This study was aimed at externally validating this model in unrelated donor hematopoietic cell transplantation. The impact of the predictor on overall survival (OS) and relapse incidence was tested in a Cox regression model adjusted for patient age, a modified disease risk index, Karnofsky performance status, donor age, HLA match, sex match, cytomegalovirus match, conditioning intensity, type of T-cell depletion, and graft type. Data from 2222 patients with acute myeloid leukemia or myelodysplastic syndrome were analyzed. KIR genes were typed by using high-resolution amplicon-based next-generation sequencing. In univariable analyses and subgroup analyses, OS and the cumulative incidence of relapse of patients with a KIR-advantageous donor were comparable to patients with a KIR-disadvantageous donor. The adjusted hazard ratio from the multivariable Cox regression model was 0.99 (Wald test, P = .93) for OS and 1.04 (Wald test, P = .78) for relapse incidence. We also tested the impact of activating donor KIR2DS1 and inhibition by KIR3DL1 separately but found no significant impact on OS and the risk of relapse. Thus, our study shows that the proposed model does not universally predict NK-mediated disease control. Deeper knowledge of NK-mediated alloreactivity is necessary to predict its contribution to graft-versus-leukemia reactions and to eventually use KIR genotype information for donor selection.

HLA molecules are key restrictive elements to present intracellular antigens at the crossroads of an effective T-cell response against SARS-CoV-2. To determine the impact of the HLA genotype on the severity of SARS-CoV-2 courses, we investigated data from 6,919 infected individuals. HLA-A, -B, and -DRB1 allotypes grouped into HLA supertypes by functional or predicted structural similarities of the peptide-binding grooves did not predict COVID-19 severity. Further, we did not observe a heterozygote advantage or a benefit from HLA diplotypes with more divergent physicochemical peptide-binding properties. Finally, numbers of in silico predicted viral T-cell epitopes did not correlate with the severity of SARS-CoV-2 infections. These findings suggest that the HLA genotype is no major factor determining COVID-19 severity. Moreover, our data suggest that the spike glycoprotein alone may allow for abundant T-cell epitopes to mount robust T-cell responses not limited by the HLA genotype.

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Results from registry studies suggest that harnessing Natural Killer (NK) cell reactivity mediated through Killer cell Immunoglobulin-like Receptors (KIR) could reduce the risk of relapse after allogeneic Hematopoietic Cell Transplantation (HCT). Several competing models have been developed to classify donors as KIR-advantageous or disadvantageous. Basically, these models differ by grouping donors based on distinct KIR–KIR–ligand combinations or by haplotype motif assignment. This study aimed to validate different models for unrelated donor selection for patients with Myelodysplatic Syndromes (MDS) or secondary Acute Myeloid Leukemia (sAML). In a joint retrospective study of the European Society for Blood and Marrow Transplantation (EBMT) and the Center for International Blood and Marrow Transplant Research (CIBMTR) registry data from 1704 patients with secondary AML or MDS were analysed. The cohort consisted mainly of older patients (median age 61 years) with high risk disease who had received chemotherapy-based reduced intensity conditioning and anti-thymocyte globulin prior to allogeneic HCT from well-matched unrelated stem cell donors. The impact of the predictors on Overall Survival (OS) and relapse incidence was tested in Cox regression models adjusted for patient age, a modified disease risk index, performance status, donor age, HLA-match, sex-match, CMV-match, conditioning intensity, type of T-cell depletion and graft type. KIR genes were typed using high-resolution amplicon-based next generation sequencing. In univariable and multivariable analyses none of the models predicted OS and the risk of relapse consistently. Our results do not support the hypothesis that optimizing NK-mediated alloreactivity is possible by KIR-genotype informed selection of HLA-matched unrelated donors. However, in the context of allogeneic transplantation, NK-cell biology is complex and only partly understood. KIR-genes are highly diverse and current assignment of haplotype motifs based on the presence or absence of selected KIR genes is over-simplistic. As a consequence, further research is highly warranted and should integrate cutting edge knowledge on KIR genetics, and NK-cell biology into future studies focused on homogeneous groups of patients and treatment modalities.

Despite recent advances, allogeneic hematopoietic stem cell transplantation (allo-HSCT) continues to be accompanied by a high rate of morbidity and mortality. Several scores have been developed to predict outcome after allo-HSCT. The recently revised Pretransplant Assessment of Mortality (PAM) score is based on patient age, donor type, disease risk, cytomegalovirus (CMV) serostatus of patient and donor, and forced expiratory volume in 1 second (FEV). The aim of this study was to analyze the predictive power of the PAM score in an independent large cohort of patients with acute myelogenous leukemia (AML). We selected adult patients with AML who underwent a first allo-HSCT at the University Hospital of Dresden, a tertiary care hospital with a large transplantation program. All adult patients treated between January 1, 2003, and July 1, 2015, were included. The PAM score was calculated as described previously. Overall survival (OS), cumulative incidence of relapse (CIR), and nonrelapse mortality (NRM) after allo-HSCT were analyzed. Age, AML type, sex match, CMV match, donor type, European Leukemia Net risk classification, type of conditioning, disease stage, and PAM score as a continuous variable were selected a priori for multivariate Cox regression analyses. A total of 544 patients met the inclusion criteria. The median patient age was 57 years. With a median follow-up of 47 months (range, 1 to 161 months), the estimated OS for the whole cohort at 4 years was 43%, with a CIR of 30% and an NRM of 31%. The probability of OS at 4 years was 65% for patients with a PAM score of 0, 52% in those with a PAM score of 1, 33% in those with a PAM score of 2, and 22% in those with a PAM score of 3 (P < .001, log-rank test). Both the CIR and NRM increased with higher PAM scores (P = .005 and P < .001, respectively, Gray test). In multivariate analysis, age (hazard ratio [HR], 1.02 per year; P = .004), disease stage (primary induction failure versus first complete remission (CR1); HR, 1.5; P = .03), and the PAM score (HR 1.04; P = .03) had a significant impact on OS. This is the first independent validation of the revised PAM score allowing for simple and valid estimation of transplantation outcomes. It can serve as an important tool in counseling patients with AML, as well as in designing future trials.