Jun Kato

Pre‐engraftment syndrome (PES) is a unique complication of cord blood transplantation (CBT) whose risk factors and impact on transplant outcomes remain controversial. Using a nationwide database in Japan, we analyzed a total of 3734 patients who underwent single‐unit CBT. PES occurred in 18.3% of patients, and risk factors for PES included a higher hematopoietic cell transplantation‐specific comorbidity index, first transplantation, myeloablative conditioning (MAC), lower total nucleated cell (TNC) dose, and graft‐versus‐host disease (GVHD) prophylaxis regimens excluding tacrolimus with methotrexate. Patients who developed PES had significantly higher incidences of grade II–IV acute GVHD (53.1% vs. 31.3%, p < 0.001) and chronic GVHD (27.2% vs. 21.7%, p = 0.002) compared to those without PES. Landmark analysis with multivariable adjustment revealed that PES was independently associated with increased non‐relapse mortality (NRM, hazard ratio [HR] 1.46; 95% CI 1.22–1.75; p < 0.001), reduced relapse incidence (HR 0.78; 95% CI 0.63–0.96; p = 0.020), and a trend toward inferior overall survival (OS, HR 1.13; 95% CI 0.98–1.30; p = 0.088). Moreover, patients who experienced both PES and acute GVHD had the highest 2‐year NRM (31.7%; 95% CI 26.0%–37.6%) and the lowest 2‐year OS (55.9%; 95% CI 50.0%–62.4%), compared with those who experienced either PES (NRM 20.7%; OS 65.0%) or acute GVHD (NRM 19.5%; OS 62.8%) ( p < 0.001), highlighting the combined effects of these complications. This study, the largest to date on PES, demonstrates its clinical significance as an early complication with lasting effects on transplant outcomes.

Clinically significant cytomegalovirus infection (csCMVi) is frequently observed after allogeneic hematopoietic stem cell transplantation (HSCT) and prophylaxis with letermovir is commonly adopted. However, the clinical benefit of letermovir prophylaxis according to graft sources has not been sufficiently elucidated. We retrospectively analyzed 2194 recipients of HSCT who were CMV-seropositive (236 with letermovir prophylaxis and 1958 without prophylaxis against CMV). csCMVi was significantly less frequent in patients with letermovir prophylaxis than in those without (23.7% vs 58.7% at 100 days after HSCT, P < .001) and the same trend was seen when recipients of bone marrow (BM), peripheral blood stem cell (PBSC), or cord blood (CB) transplantation were separately analyzed. In recipients of BM, nonrelapse mortality (NRM) was significantly lower in the letermovir group at 6 months after HSCT (5.0% vs 14.9%, P = .018), and the same trend was observed in recipients of PBSCs (14.7% vs 24.8%, P = .062); however, there was no statistical significance at 1 year (BM, 21.1% vs 30.4%, P = .67; PBSCs, 21.2% vs 30.4%, P = .096). In contrast, NRM was comparable between recipients of CB with and without letermovir prophylaxis throughout the clinical course (6 months, 23.6% vs 24.3%, P =.92; 1 year, 29.3% vs 31.0%, P = .77), which was confirmed by multivariate analyses. In conclusion, the impact of letermovir prophylaxis on NRM and csCMVi should be separately considered according to graft sources.

Corynebacterium amycolatum is a part of the normal skin flora and has been underestimated as a pathogen. However, in recent years, the species has gained recognition as an important pathogen causing severe infections, particularly in immunocompromised patients. Nevertheless, identifying these organisms at the species level is difficult in routine clinical microbiology, leading to limited knowledge of their clinical manifestations in infectious diseases. In this study, we report a rare case of multiple subcutaneous abscesses in a patient with severe neutropenia, wherein C.amycolatum was identified as the causative organism through genotyping tests. This case highlights the importance of this organism as an aetiological agent of severe skin infections in patients with compromised immune systems.

Calcineurin inhibitors (CNIs), used as immunosuppressants, have revolutionized transplantation medicine with their strong suppressive activity on alloreactive T lymphocytes; however, they may also cause various adverse effects, including an increased risk for infection and nephrotoxicity. Regulatory T (Treg) cells can complement the deleterious side effects of CNIs with their effective Ag-specific suppressive activities. However, several studies have shown that CNIs suppress Treg cell differentiation. Therefore, an understanding of the mechanisms by which CNIs suppress Treg cell differentiation, as well as an approach for promoting the differentiation of Treg cells in the presence of CNIs, has significant clinical value. In this article, we report that the nuclear orphan receptor Nr4a1 plays a pivotal role in Treg cell differentiation in the presence of CNIs. Unlike that of its family members, Nr4a2 and Nr4a3, the expression of Nr4a1 was not suppressed by CNI treatment, thereby mediating Treg cell differentiation in the presence of CNIs. In a mouse allogeneic graft-versus-host disease model, Nr4a1 mediated tolerance by promoting Treg cell differentiation in mice administered cyclosporine A, prolonging the survival of recipients. Furthermore, activation of Nr4a1 via its agonist partially restored Treg cell differentiation, which was suppressed by cyclosporine A treatment. Finally, we found that the rs2701129 single-nucleotide polymorphism, which was shown to downregulate NR4A1 expression, showed a trend toward a higher incidence of chronic graft-versus-host disease in patients undergoing hematopoietic stem cell transplantation. Therefore, our study will be of clinical significance because we demonstrated the role of Nr4a1 in Treg cell differentiation in the presence of CNIs. Key Points Nr4a1 plays crucial roles in Treg cell differentiation in the presence of CNIs. Nr4a1 deficiency impairs the induction of T cell tolerance in the presence of CNIs.

Pretransplant measurable residual disease (MRD) has been shown to be associated with relapse incidence following allogeneic hematopoietic cell transplantation (HCT) for acute myeloid leukemia (AML). However, it remains less clear whether pretransplant MRD status affects transplant outcomes in core binding factor AML (CBF-AML). We retrospectively evaluated the effect of pretransplant MRD, which was measured by a polymerase chain reaction of RUNX1-RUNX1T1 or CBFB-MYH11 fusion transcripts, on transplant outcomes for a cohort of 959 adult patients with t(8;21) or inv(16) AML treated by allogeneic HCT during complete remission (CR), between 2000 and 2018. Multivariate analysis showed the absence of pretransplant MRD was significantly associated with lower relapse (hazard ratio [HR], 0.46; P < 0.001), treatment failure (HR, 0.66; P = 0.004), and overall mortality (HR, 0.72; P = 0.037) among patients with t(8;21). However, pretransplant MRD negativity was not associated with relapse (HR, 0.73; P = 0.420), treatment failure (HR, 0.64; P = 0.063), or overall mortality (HR, 0.69; P = 0.149) among patients with inv(16). In subgroup analysis, pretransplant MRD status significantly affected relapse and LFS only in patients with t(8;21) undergoing allogeneic HCT during CR2. In conclusion, our data demonstrate the different prognostic values of pretransplant MRD for CBF-AML, highlighting the need to develop effective therapeutic strategies for such MRD-positive patients.