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Cytomegalovirus (CMV) reactivation in cord blood transplantation (CBT) may result in the proliferation and maturation of natural killer (NK) cells. Similarly, a mismatch of the killer cell immunoglobulin-like receptor (KIR)-ligand induces NK cell activation. Therefore, if CMV reactivation occurs in the presence of KIR-ligand mismatch, it might improve CBT outcomes. We assessed the difference in the effect of CMV reactivation in the presence of KIR-ligand mismatch on disease relapse in the graft-versus-host direction. A total of 2840 patients with acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, and chronic myeloid leukemia were analyzed. Among those with a HLA-Bw4/A3/A11 (KIR3DL-ligand) mismatch, CMV reactivation up to 100 days following CBT had a favorable impact on relapse (18.9% vs. 32.9%, P = 0.0149). However, this effect was not observed in cases without the KIR3DL-ligand mismatch or in those with or without a HLA-C1/C2 (KIR2DL-ligand) mismatch. The multivariate analysis suggested that CMV reactivation had a favorable effect on relapse only in cases with a KIR3DL-ligand mismatch (hazard ratio 0.54, P = 0.032). Moreover, the interaction effect between CMV reactivation and KIR3DL-ligand mismatch on relapse was significant (P = 0.039). Thus, our study reveals the association between KIR-ligand mismatches and CMV reactivation, which will enhance CBT outcomes.

Graft failure (GF) is a life-threatening complication after allogeneic stem cell transplantation. Although salvage cord blood transplantation (CBT) is a curative therapy for GF, the optimal immunosuppression after salvage CBT remains unknown. Using nationwide registration data, we compared the transplant outcomes of patients who developed GF and underwent salvage CBT using immunosuppressants, including calcineurin (CNI) alone (n = 177); CNI plus methotrexate (CNI+MTX, n = 150); and CNI plus mycophenolate mofetil (CNI+MMF, n = 161). The CNI+MMF group, in comparison with the CNI+MTX and CNI alone groups, demonstrated better neutrophil recovery at 30 days (62.7 vs. 42.7 vs. 53.1%, P < 0.001); better overall survival (OS) at 12 months (48.4 vs. 33.5 vs. 28.3%, P < 0.001); and lower non-relapse mortality (NRM) at 12 months (35.2 vs. 53.9 vs. 56.5%, P < 0.001). On multivariate analysis, CNI+MMF had the best neutrophil recovery (hazard ratio (HR), 1.71; P < 0.001) and OS (HR, 0.64; P = 0.002) and the lowest NRM (HR, 0.53; P < 0.001). Hemorrhage was relatively less frequent in the CNI+MMF group. CNI+MMF can be a promising immunosuppressant regimen after salvage CBT for GF, with better engraftment and survival outcomes, compared with CNI alone and CNI+MTX.

Cytomegalovirus (CMV) infection is a major complication during allogeneic stem cell transplantation (allo-SCT). However, mechanisms of adaptive immunity that drive this remain unclear. To define early immunological responses to CMV after transplantation, we using next-generation sequencing to examine the repertoire of T-cell receptors in CD8 + /CMV pp65 tetramer + cells (CMV-CTLs) in peripheral blood samples obtained from 16 allo-SCT recipients with HLA-A*24:02 at the time of CMV reactivation. In most patients, TCR beta repertoire of CMV-CTLs was highly skewed (median Inverse Simpson's index: 1.595) and, 15 of 16 patients shared at least one TCR-beta clonotype with ≥ 2 patients. The shared TCRs were dominant in 12 patients and, two clonotypes were shared by about half of the patients. Similarity analysis showed that CDR3 sequences of shared TCRs were more similar than unshared TCRs. TCR beta repertoires of CMV-CTLs in 12 patients were also analyzed after 2-4 weeks to characterize the short-term dynamics of TCR repertoires. In ten patients, we observed persistence of prevailing clones. In the other two patients, TCR repertoires became more diverse, major clones declined, and new private clones subsequently emerged. These results provided the substantive clue to understand the immunological behavior against CMV reactivation after allo-SCT.

There are few reports on allogeneic hematopoietic stem cell transplantation (allo-HSCT) for adult B-cell acute lymphoblastic leukemia (B-ALL) harboring t(1;19)(q23;p13.3). We used nationwide registry data of Japan for 2003-2016 to evaluate transplant outcomes and clarified prognostic factors among adult allo-HSCT recipients with B-ALL harboring t(1;19)(q23;p13.3) (n = 125). Compared with cytogenetically normal (CN) B-ALL patients (n = 1057), their 3-year overall survival (OS) rates were comparable (55.4% for t(1;19) and 54.4% for CN; P = 0.76). Considering only patients in first complete hematological remission (CR1), the 3-year OS rates remained comparable (70.5% for t(1;19) and 67.8% for CN; P = 0.86). For t(1;19) patients in CR1, minimal residual disease (MRD) at transplantation was associated with relatively worse outcomes. The 3-year OS rates were 43.6% for patients with MRD and 77.4% for those without it (P = 0.016). The 3-year relapse rates were 54.5% for patients with MRD and 12.8% for those without it (P < 0.001). Multivariate analyses revealed that MRD at transplantation was a significant risk factor for OS and relapse. In the high-intensity chemotherapy era, t(1;19)(q23;p13.3) did not have a poorer posttransplant prognosis than the normal karyotype. However, even for patients in CR1, MRD at transplantation was associated with comparatively worse OS and higher relapse rates.