Delayed platelet recovery (DPR) despite prompt neutrophil engraftment is frequently observed after allogeneic hematopoietic stem cell transplantation (HSCT). However, few studies have evaluated the risk factors and long-term outcome. Therefore, we retrospectively analysed 219 adult patients who underwent their first allogenic HSCT with neutrophil engraftment. Of these 219 patients, 50 (22.8%) had DPR that was defined as relapse-free survival at day 60 after HSCT without primary platelet recovery despite neutrophil engraftment. The results of a multivariate analysis showed that a high-risk underlying disease (odds ratio [OR], 2.38; 95% confidence interval [CI], 1.04-5.48; P = .041) and human leukocyte antigen-mismatched HSCT (OR, 2.63; 95% CI, 1.28-5.43; P = .009) were associated with an increased risk of DPR. In univariate analyses, the occurrence of DPR was significantly associated with inferior overall survival, high nonrelapse mortality, and a low incidence of chronic graft-versus-host disease (GVHD), despite a comparable relapse rate. In multivariate analyses, DPR was associated with inferior overall survival (hazard ratio [HR], 2.00; 95% CI, 1.23-3.27; P = .005) and a low incidence of chronic GVHD (HR, 0.42; 95% CI, 0.22-0.78; P = .002). In conclusion, DPR was a strong predictor of shorter survival but also less frequent chronic GVHD.

We previously reported that the T-cell receptor (TCR) repertoire of human T-cell lymphotropic virus type 1 (HTLV-1) Tax-specific CD8 cytotoxic T cells (Tax-CTLs) was highly restricted and a particular amino acid sequence motif, the PDR motif, was conserved among HLA-A*24:02-positive (HLA-A*24:02) adult T-cell leukemia/lymphoma (ATL) patients who had undergone allogeneic hematopoietic cell transplantation (allo-HSCT). Furthermore, we found that donor-derived PDR CTLs selectively expanded in ATL long-term HSCT survivors with strong CTL activity against HTLV-1. On the other hand, the TCR repertoires in Tax-CTLs of asymptomatic HTLV-1 carriers (ACs) remain unclear. In this study, we directly identified the DNA sequence of complementarity-determining region 3 (CDR3) of the TCR-β chain of Tax-CTLs at the single-cell level and compared not only the TCR repertoires but also the frequencies and phenotypes of Tax-CTLs between ACs and ATL patients. We did not observe any essential difference in the frequencies of Tax-CTLs between ACs and ATL patients. In the single-cell TCR repertoire analysis of Tax-CTLs, 1,458 Tax-CTLs and 140 clones were identified in this cohort. Tax-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was exclusively observed in all ACs and ATL patients. However, there was no correlation between PDR CTL frequencies and HTLV-1 proviral load (PVL). In conclusion, we have identified, for the first time, a unique amino acid sequence, PDR, as a public TCR-CDR3 motif against Tax in HLA-A*24:02 HTLV-1-infected individuals. Further investigations are warranted to elucidate the role of the PDR CTL response in the progression from carrier state to ATL. ATL is an aggressive T-cell malignancy caused by HTLV-1 infection. The HTLV-1 regulatory protein Tax aggressively promotes the proliferation of HTLV-1-infected lymphocytes and is also a major target antigen for CD8 CTLs. In our previous evaluation of Tax-CTLs, we found that a unique amino acid sequence motif, PDR, in CDR3 of the TCR-β chain of Tax-CTLs was conserved among ATL patients after allo-HSCT. Furthermore, the PDR Tax-CTL clones selectively expanded and showed strong cytotoxic activities against HTLV-1. On the other hand, it remains unclear how Tax-CTL repertoire exists in ACs. In this study, we comprehensively compared Tax-specific TCR repertoires at the single-cell level between ACs and ATL patients. Tax-CTLs showed highly restricted TCR repertoires with a strongly biased usage of BV7, and PDR, the unique motif in TCR-β CDR3, was conserved in all ACs and ATL patients, regardless of clinical subtype in HTLV-1 infection.

Co-expression of MYC and BCL2 proteins in diffuse large B-cell lymphoma (DLBCL), or 'double-expressor lymphoma' (DEL), results in poor patient prognosis, but the significance of DEL when aggressive treatments are applied remains uncertain. We performed a retrospective analysis of 40 patients with de novo DLBCL, who were categorized as being at high/high-intermediate risk according to the age-adjusted International Prognostic Index. Patients underwent an R-Double-CHOP regimen, a dose-intensified immunochemotherapy with or without consolidative high-dose chemotherapy followed by autologous stem cell transplantation. According to immunohistochemical analysis, 10 (25%) patients were categorized as having DEL, showing positivity for MYC (≥40%) and BCL2 (≥50%). The 3 year progression-free survival and overall survival of the DEL group were significantly worse compared with those of the non-DEL group (30% vs. 63%, p = 0.019 and 40% vs. 82%, p = 0.006, respectively). These results suggest that advanced DEL may need discrete treatment strategies.

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