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Fluoroquinolone prophylaxis’s (FQ-P) usefulness in patients with neutropenia is controversial. In recent decades, Italian epidemiological data has shown worrisome rates of FQ resistance. A single-center cohort study on 136 autologous stem cell transplantations (ASCTs) and 223 allogeneic hematopoietic stem cell transplantations (allo-HSCTs) was performed from January 2018 to December 2020. Piperacillin/tazobactam was the first-line therapy for febrile neutropenia (FN). Since February 2019, FQ-P has been omitted. We evaluated the day +30 posttransplant cumulative incidence function (CIF) of gram-negative bacteria pre-engraftment bloodstream infections (PE-BSIs) and any changes in antimicrobial resistance, FN, and infection-related mortality (IRM). In ASCTs, ≥1 FN episode occurred in 74.3% of transplants, without differences among groups (P = .66). CIF of gram-negative bacteria PE-BSI was 10.1%, with a significant difference according to FQ-P (0% [LEVO-group] vs 14.1% [NO-LEVO-group], P = .016). CIF of IRM was 0% in both groups. In allo-HSCTs, ≥1 FN episode occurred in 96.4% of transplants, without differences among groups (P = .72). CIF of gram-negative bacteria PE-BSI was 28%, significantly higher without FQ-P (14.7% [LEVO-group] vs 34.4% [NO-LEVO-group], P = .003). CIF of IRM was 5%, superimposable in both groups (P = .62). Comparing antimicrobial resistance among gram-negative bacteria of allo-HSCT setting, in the group without FQ-P, a significantly higher proportion of pathogens was susceptible to piperacillin/tazobactam (71% vs 30%, P = .026), FQ (49% vs 10%, P = .03), and carbapenems (95% vs 50%, P = .001). FQ-P discontinuation increased gram-negative bacteria PE-BSI but did not impact IRM, both in the ASCT and allo-HSCT settings; importantly, it concurred to significantly decrease antimicrobial resistance in gram-negative bacteria.

Human Herpesvirus-6 (HHV-6) can reactivate after allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT), and may lead to severe symptoms. HHV-6-specific immune responses after HSCT are largely unexplored. We conducted a prospective observational study on 208 consecutive adult patients who received allo-HSCT, to investigate HHV-6 reactivations and specific immune responses. IFN-γ-producing HHV-6-specific T cells were quantified by ELISpot assay. "HHV-6 reactivation" occurred in 63% of patients, at a median of 25 days (range 3-538) from allo-HSCT. Only 40% of these presented a "clinically relevant infection", defined according to center guidelines by the presence of classical HHV-6 End-Organ Diseases (EOD), based on European-Conference-on-Infections-in-Leukaemia (ECIL) guidelines, and other possible HHV6-related EODs. By multivariate analysis, we identified risk factors for HHV-6 reactivation: previous allo-HSCT (Hazard Ratio, HR=2.89; p-value4 days after the first viremia detection, predicted clinically relevant infections (p-value

Fluoroquinolone prophylaxis (FQ-P) usefulness in neutropenic patients is controversial. In recent decades, Italian epidemiological data has shown worrisome rates of FQ resistance. A single-center cohort study on 136 autologous stem cell transplantations (ASCTs) and 223 allogeneic hematopoietic stem cell transplantations (allo-HSCTs) was performed from Jan-2018 to Dec-2020. Piperacillin/tazobactam was the first-line therapy for febrile neutropenia (FN). Since Feb-2019, FQ-P was omitted. We evaluated the day +30 post-transplant cumulative incidence function (CIF) of Gram-negative bacteria pre-engraftment blood-stream infections (PE-BSIs) and any changes in antimicrobial resistance, FN and infection-related mortality (IRM). In ASCTs, ≥1 FN episode occurred in 74.3% of transplants, without differences among groups [p=0.66]. CIF of Gram-negative bacteria PE-BSI was 10.1% with a significant difference according to FQ-P [0% (LEVO-group) versus 14.1% (NO-LEVO-group), p=0.016]. CIF of IRM was 0% in both groups. In allo-HSCTs, ≥1 FN episode occurred in 96.4% of transplants, without differences among groups [p=0.72]. CIF of Gram-negative bacteria PE-BSI was 28% and it was significantly higher without FQ-P [14.7% (LEVO-group) versus 34.4% (NO-LEVO-group), p=0.003]. CIF of IRM was 5%, superimposable in both groups [p=0.62]. Comparing antimicrobial resistance among Gram-negative bacteria in the setting of allo-HSCT, in the group without FQ-P a significantly higher proportion of pathogens was susceptible to piperacillin/tazobactam (71% versus 30%, p=0.026), FQ (49% versus 10%, p=0.03) and carbapenems (95% versus 50%, p=0.001). FQ-P discontinuation increased Gram-negative bacteria PE-BSI, but it did not impact IRM, both in ASCT and allo-HSCT setting; importantly, it concurred to decrease significantly antimicrobial resistance in Gram-negative bacteria.

Post-transplant cyclophosphamide (PTCy) has emerged as a promising graft-versus-host disease (GvHD) prophylaxis in allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, no studies have reported the efficacy of a GvHD prophylaxis based on PTCy with sirolimus (Sir-PTCy) in patients with acute myeloid leukemia (AML). In this retrospective study, we analyze the use of sirolimus in combination with PTCy, with or without mycophenolate mofetil (MMF), on 242 consecutive adult patients with AML undergoing a myeloablative first allo-HSCT from different donor types, in three European centers between January 2017 and December 2020. Seventy-seven (32%) patients received allo-HSCT from HLA-matched sibling donor, 101 (42%) from HLA-matched and mismatched unrelated donor, and 64 (26%) from haploidentical donor. Except for neutrophil and platelet engraftment, which was slower in the haploidentical cohort, no significant differences were observed in major transplant outcomes according to donor type in univariate and multivariate analysis. GvHD prophylaxis with Sir-PTCy, with or without MMF, is safe and effective in patients with AML undergoing myeloablative allo-HSCT, resulting in low rates of transplant-related mortality, relapse/progression, and acute and chronic GvHD in all donor settings.

After allogeneic hematopoietic stem cell transplantation (HSCT), the emergence of circulating cytomegalovirus (CMV)- specific T cells correlates with protection from CMV reactivation, an important risk factor for non-relapse mortality. However, functional assays measuring CMV-specific cells are time-consuming and often inaccurate at early time-points. We report the results of a prospective single-center, non-interventional study that identified the enumeration of Dextramerpositive CMV-specific lymphocytes as a reliable and early predictor of viral reactivation. We longitudinally monitored 75 consecutive patients for 1 year after allogeneic HSCT (n=630 samples). The presence of ≥0.5 CMV-specific CD8+ cells/mL at day +45 was an independent protective factor from subsequent clinically relevant reactivation in univariate (P

Incidence and outcome of infections after allogeneic hematopoietic stem cell transplantation (HSCT) with post-transplant cyclophosphamide (PT-Cy) as graft-versus-host disease (GVHD) prophylaxis are largely unknown. Study aims were to estimate the incidence of pre-engraftment bloodstream infections (PE-BSIs) and viral infections (VIs; cytomegalovirus [CMV], adenovirus [ADV], human herpes virus 6 [HHV6], and BK-polyomavirus hemorrhagic-cystitis [BKPyV-HC]), their predictive factors, and infection-related mortality (IRM) after HSCT with PT-Cy. We analyzed 235 patients: 62%, 21%, and 17% received haploidentical (haplo), matched-unrelated donor (MUD), and matched-related donor, respectively. Overall, 72 patients had 77 PE-BSI episodes at a median time of 13 days after HSCT: cumulative incidence function (CIF) at 28 days was 32%, without differences among donor types (P = .988). By multivariate analysis, CIF of PE-BSI was higher in patients with severe neutropenia before HSCT (adjusted hazard ratio [AHR] = 2.90) and in multidrug-resistant Gram-negative bacteria rectal carriers (AHR = 2.68). IRM at 30 days was 5%, without differences by donor type (P = .106). Overall, 208 patients experienced ≥1 VIs (first occurrence among CMV, HHV6, ADV, BKPyV-HC) at a median time of 20 days after HSCT: CIF at 90 days was 91%, significantly higher in MUD and haplo (P = .0089). By multivariate analysis, also acute GVHD grade ≥2 (AHR = 1.32) and host/donor CMV-serology mismatch (positive/positive versus negative/negative: AHR = 2.95, positive/negative versus negative/negative: AHR = 2.41, negative/positive versus negative/negative: AHR = 2.35) affected VIs occurrence. IRM at 180 days was 8%, without differences among donor types (P = .106). In conclusion, study results did not show a significant impact of donor type on PE-BSI incidence; conversely, MUD and haploidentical transplants retained a higher occurrence of VIs in the early phase after HSCT.

Correlation between risk of graft-versus-host disease (GvHD) and CD3+ counts within the peripheral blood stem cell graft has recently been reported in the setting of post-transplant cyclophosphamide (PT-Cy). We aimed to investigate the benefit of the addition of a single dose of anti-T lymphocyte globulin (ATLG 5 mg/kg) to PT-Cy in this setting. Starting in 2019, all patients receiving PBSC transplant containing CD3+ counts above 300 × 106/kg (study group) received a post-transplant dose of ATLG in addition to standard PT-Cy. The study was designed as a real-life analysis and included all consecutive Hematopoietic Stem Cell Transplantation (HSCT) recipients according to the above-mentioned inclusion criterion (n = 21), excluding cord blood and bone marrow donors. Using a 1:2 matched-pair analysis, we compared the outcomes with a historical population who received PT-Cy only (control group). We found a delayed platelet engraftment (29% vs. 45% at 30 days, p = 0.03) and a non-significant trend toward higher risk of poor graft function (29% vs. 19%, p = 0.52). The addition of ATLG impacted long-term immune reconstitution on the CD4+ subsets, but this did not translate into higher rate of relapse or viral infection. Acute GvHD was not significantly impacted, but 1-year cumulative incidence of chronic GvHD was significantly lower in the study group (15% vs. 41%, p = 0.04). Survival outcomes were comparable. In conclusion PT-Cy and ATLG was overall safe and translated into a low rate of chronic GvHD incidence.

Background. Median age of occurrence of acute myeloid leukemias (AML) and myelodisplastc syndromes (MDS) is 65 years and older. Nevertheless, the use of allogeneic stem cell transplant (allo-HCT) has been historically limited to younger population, namely due to excess in non-relapse-mortality (NRM) in olders. Methods. In the present study, we analyzed all consecutive patients aged ≥ 65y diagnosed with AML (71, 81%) or MDS (19, 19%) who received transplants from adult donors at our center from January 2005 to December 2019. Results. Median age was 68.29y (65.02-76.54), 26pts (29%) aged ≥ 70y. Thirty-three (37%) pts received a HLA-matched donor. Conditioning regimen was myeloablative in 46pts (51%). The 3-year overall survival (OS) was 53+/-6%, and disease free survival (DFS) 45+/-6% (Figure 1). Day-100 and 3-year NRM was 17+/-2% and 29+/-2%, respectively. The 3-year CI of relapse was 22+/-2%. Day-100 CI of aGvHD was 21+/-2% for grade II-IV, 14+/-1% for grade III-IV. The 3-year CI of cGvHD was 35+/-3%, extensive 20+/-2%. In multivariate analysis, the Karnofsky Performance Status (KPS) < 90% was associated with lower OS (HR: 2.999, CI: 1.477- 6.691; p=0.002), DFS (HR: 3.155, CI: 1.593 - 6.250; p=0.001) and higher NRM (HR: 2.997, CI: 1.344-6.682; p=0.041). HCT-CI ≥ 3 was also associated with higher NRM (HR: 2.949, CI: 1.166-7.462, p=0.022,). Diagnosis of MDS and receiving a matched donor with PTCy were associated with longer OS (HR: 0.3440, CI: 0.1029-0.915; p=0.033; HR: 0.197, CI: 0.042-0.934; p=0.041).Conclusions. Age alone should not limit transplant eligibility for AML and MDS. KPS and HCT-CI proved to be useful for patient selection among the elderly. The use of HLA-matched donors with PTCy improved OS compared to ATG in our consecutive series.

Objectives To evaluate ceftazidime/avibactam (C/A) and ceftolozane/tazobactam (C/T) use in haematological patients with febrile neutropenia receiving high-dose chemotherapy and haematopoietic stem cell transplantation (HSCT). Methods A retrospective study was conducted to assess C/A and C/T efficacy through infection-related mortality (IRM) and bacteraemia clearance for carbapenem-resistant Gram-negative bacteria (CR-GNB) pre-engraftment blood-stream infections (PE-BSIs) between January–December 2018. Results Seventy patients underwent allogeneic HSCT: C/A and C/T were dispensed in 13% and 3%, respectively. C/A was administered as definite therapy for carbapenem-resistant Klebsiella pneumoniae (CR-Kp) PE-BSI in four carriers (bacteraemia clearance in 5 days), empirical therapy for a clinically documented infection in two patients (one carrier with pneumonia and one non-carrier with shock) and empirical therapy for fever of unknown origin in three CR-Kp carriers. C/T was administered as definite therapy for carbapenem-resistant Pseudomonas aeruginosa (CR-Pa) intra-abdominal infection in one carrier and empirical therapy for a clinically documented infection (pneumonia) in one non-carrier. Among patients without PE-BSIs and with Gram-positive bacteria PE-BSIs, IRM was 0% at +30 days; conversely, it was 30% in GNB PE-BSIs (two CR-Kp and one CR-Pa C/T-resistant). Thirty-nine patients underwent autologous HSCT: C/A and C/T were administered, respectively, as definite therapy for CR-Kp PE-BSI in one carrier (bacteraemia clearance in 3 days) and for Pa PE-BSI (three strains, one CR-Pa) in one non-carrier (bacteraemia clearance in 2 days). Overall, IRM at +30 days was 0%. Conclusions Monitoring multidrug-resistant GNB colonisation enabled selection of carriers who benefit from prompt administration of new antibiotics, improving HSCT outcomes in a high-risk population. C/A and C/T were effective in bacteraemia clearance; unfortunately, multidrug-resistant GNB PE-BSIs were still a burden to IRM.

Febrile neutropenia and sepsis are common and life-threatening complications in hematological diseases. This study was performed retrospectively in 514 patients treated for febrile neutropenia at our institute, to investigate the clinical usefulness of a molecular tool, LightCycler® SeptiFast test (SF), to promptly recognize pathogens causing sepsis in hematological patients. We collected 1837 blood samples of 514 consecutive hematological patients. The time of processing is short. Overall, 757 microorganisms in 663 episodes were detected by molecular test and standard blood cultures (BC): 73.6% Gram-positive bacteria, 23.9% Gram-negative bacteria, and 2.5% fungal species. This large analysis demonstrated a significant episode-to episode agreement (71.9%) between the two methods, higher in negative samples (89.14%), and a specificity of 75.89%. Clinical variables that gave a statistically significant contribution to their concordance were absolute neutrophil count, ongoing antimicrobial therapy, timing of test execution, and organ localization of infection. The large analysis highlights the potential of molecular-based assays directly performed on blood samples, especially if implementing the detection of antibiotic resistance genes, which was lacking in the used study.

Infections are a major cause of morbidity and mortality in hematological patients. We prospectively tested a new molecular assay (Verigene®) in 79 consecutive hematological patients, with sepsis by gram-negative bacteria. A total of 82 gram-negative microorganisms were isolated by blood cultures, of which 76 cases were mono-microbial. Considering the bacteria detectable by the system, the concordance with standard blood cultures was 100%. Resistance genes were detected in 20 of the isolates and 100% were concordant with the phenotypic antibiotic resistance. Overall, this new assay correctly identified 66/82 of all the gram-negative pathogens, yielding a general sensitivity of 80.5%, and providing information on genetic antibiotic resistance in a few hours. This new molecular assay could ameliorate patient management, resulting in a more rational use of antibiotics.

Introduction: Cytomegalovirus (CMV) reactivation and disease are important risk factors after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and strongly affect morbidity and mortality after transplant. CMV-specific T cell reconstitution controls CMV reactivation and protects against serious adverse events but a protective level of CMV-specific T cell response or standardized method for its monitoring have not been yet determined. Methods: We designed a prospective, single-center observational study to assess if the kinetic and quality of CMV specific T-cell reconstitution impact the incidence and severity of CMV reactivations. We have enrolled 84 consecutive patients affected by hematological malignancies receiving allo-HSCT followed by Cyclophosphamide and Rapamycin between December 2017 and February 2019. Here we report preliminary data on the first 61 patients. Patients received allo-HSCT from family (siblings=10; HLA haploidentical=24), unrelated HLA-matched (n= 24) donors or cord blood (CB, n=3). The CMV serostatus of host (H) and donor (D) pairs was: H+/D+(n=40, 65%), H+/D-(n=20, 33%) and H-/D+ (n=1, 2%); H-/D-(7% of the overall transplanted population at our center) were excluded. CMV DNAemia was assessed weekly in whole blood (WB). Absolute numbers of polyclonal and CMV-specific T cells were quantified by flow cytometry using Troucount™Tubes (BD) and Dextramer®CMV-Kit (Immudex), respectively, in the graft and fresh WB at days -7, +30, +45, +60, +90, +120, +150, +180 and +360. Dextramer CMV kit includes reagents for the identification of CMV-specific lymphocytes restricted for several HLA class I molecules: A*01:01/*02:01/*03:01/*24:02 and B*07:02/*08:01/*35:01. These alleles allowed the longitudinal evaluation of 54 out of 61 (89%) patients. Results: At a median follow-up of 226 days post-HSCT, 31 (57%) patients experienced a CMV-related clinically relevant event (CRE, median +63 days), including 8 patients (15%) with CMV disease (median +59 days). Univariate analyses showed that the incidence of CMV clinically-relevant reactivation (CRE) was influenced by H/D CMV serostatus (0.90 in H+/D- versus 0.44 in H+/D+pairs, p=0.015) and by previous acute Graft-versus-Host Disease (aGvHD) requiring systemic immunosuppression (0.82 in aGvHD grade II-IV versus 0.52 in aGvHD grade 0-I, p=0.051). The disease status at transplant, the donor type (HLA-matched versus HLA-haploidentical/CB donors), donor's or host's age did not significantly affect the probability to develop CRE. For each time-point, we compared the absolute number of CMV-specific lymphocytes in patients experiencing or not a subsequent CRE. Our data demonstrate that higher levels of CMV-specific CD8+T cells in the donor apheresis and at +45 days after allo-HSCT are associated with reduced risk of subsequent CRE (median CMV-specific CD8+cells/kg in the apheresis=5x103in CRE-positive patients (CRE+) and 5x105in CRE-negative patients (CRE-), p=0.012; median CMV-specific CD8+at +45 days=0.14 cells/μL in CRE+and 1.21 cells/μL in CRE-, p=0.034). Furthermore, patients with any Dextramer positivity at +45 days displayed a lower incidence of CRE compared with subjects who were negative (CRE probability: 0.5 vs 1.0, p=0.003). Conversely, the absolute number of neither polyclonal CD3+CD8+T lymphocytes nor total CD3+T cells correlate with subsequent CRE. Taking advantage of the HLA mismatched-HSCT setting, we then dissected CMV-specific T-cell response according to HLA restriction elements (H/D=shared n=45, D-restricted n=14, H-restricted n=11). In H+/D+pairs, we observed a fast and similar kinetic of reconstitution of CMV-specific lymphocytes restricted by H/D and D HLAs. Conversely, in H+/D-pairs, we detected only CMV-specific CD8+lymphocytes restricted for H/D haplotypes. Host-restricted cells remained undetectable for the first 180 days after HSCT. Conclusion: Early after allo-HSCT and in the donor apheresis, the level of CMV-specific CD8+T cells measured by Dextramer staining differs in patients experiencing or not subsequent CRE. Furthermore, our findings indicate that CMV reactivations can prime H/D-restricted T cells presumably educated in the donor thymus; conversely, D- and H-restricted donor-derived lymphocytes have not yet undergone neither cross-priming nor thymic education respectively. Disclosures Brix: Immudex: Employment. Bonini:Kite/Gilead: Consultancy; Intellia Therapeutics: Consultancy; Intellia Therapeutics: Research Funding; Novartis: Consultancy; GSK: Consultancy; Allogene: Consultancy; Molmed: Consultancy; TxCell: Consultancy; -: Patents & Royalties: Adoptive T cell therapy field.

Haploidentical stem cell transplantation with T cell-replete grafts and post-transplant cyclophosphamide (PTCy) is increasingly used with encouraging outcome. Natural killer (NK) cell alloreactivity, predicted by missing killer cell immunoglobulin-like receptor (KIR) ligands in the recipient that are present in their donor improves outcome of T cell-depleted haploidentical transplants. We explored the role of KIR ligand mismatching in 444 acute leukemia patients after T cell-replete transplants with PTCy. Thirty-seven percent of all patients had KIR ligand mismatching. Patients were in first remission (CR1) (39%), second remission (CR2) (26%), or active disease (35%). Stem cell source was peripheral blood (PBSC, 46%) or bone marrow (54%). The 2-year relapse, non-relapse mortality (NRM), and survival rates were 36.0% (95% confidence interval (CI), 31.4–40.7), 23.9% (20.0–28.0), and 45.9% (40.8–51.0), respectively. Multivariate analysis identified acute myeloid leukemia compared with acute lymphoblastic leukemia (hazard ratio (HR) 0.55, P = 0.002), female gender (HR 0.72, P = 0.04), and good performance status (HR 0.71, P = 0.04) as factors associated with better survival, while advanced age (HR 1.13, P = 0.04), active disease (HR 3.38, P < 0.0001), and KIR ligand mismatching (HR 1.41, P = 0.03) as associated with worse survival. KIR ligand mismatching was associated with a trend for higher relapse but not with graft-versus-host disease or NRM. The KIR ligand-mismatching effect was more prominent in patients given PBSC. In conclusion, there is no evidence that KIR ligand mismatching results in better outcome in the PTCy setting.

Multidrug-resistant Gram-negative bacteria (MDR-GNB) are an emerging cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). Three-hundred forty-eight consecutive patients transplanted at our hospital from July 2012 to January 2016 were screened for a pretransplant MDR-GNB colonization and evaluated for clinical outcomes. A pretransplant MDR-GNB colonization was found in 16.9% of allo-HSCT and in 9.6% of auto-HSCT recipients. Both in auto- and in allo-HSCT, carriers of a MDR-GNB showed no significant differences in overall survival (OS), transplant-related mortality (TRM), or infection-related mortality (IRM) compared with noncarriers. OS at 2 years for carriers compared with noncarriers was 85% versus 81% (P =.262) in auto-HSCT and 50% versus 43% (P =.091) in allo-HSCT. TRM at 2 years was 14% versus 5% (P =.405) in auto-HSCT and 31% versus 25% (P =.301) in allo-HSCT. IRM at 2 years was 14% versus 2% (P =.142) in auto-HSCT and 23% versus 14% (P =.304) in allo-HSCT. In multivariate analysis, only grade III to IV acute graft-versus-host disease was an independent factor for reduced OS (P

Introduction: Hematopoietic Stem Cell Transplantation (HSCT) from unrelated donors (UD) is a curative therapy for many hematologic malignancies. HLA matching plays a major role in determining HSCT outcome but the relative role of incompatibilities at the different HLA loci is still debated. In particular, over 80% of UD-HSCT are performed across HLA-DPB1 mismatches (mm): a number of previous studies have devised immunogenetic models to elucidate the impact of HLA-DPB1 mm on HSCT outcome, but a comparative analysis of these models in a recent and well-characterized cohort is lacking. Methods: We selected 422 adult patients (pts) who received an 8/8 (HLA-A, B, -C and -DRB1) allele level-matched UD-HSCT from 2012 to 2015: of them, 382 (90%) had a mm at one or both HLA-DPB1 alleles. We classified functional HLA-DPB1 matching by four models, on the basis of: I) differential immunogenicity of alleles belonging to 3 groups of T-cell epitopes (TCE), as defined by functional studies (Zino, Blood, 2004) and refined by in silico prediction (Crivello, BBMT 2015); II) a similar model subdividing allelles in 4 TCE groups (TCE4, Crocchiolo, Blood 2009); III) differences in "delta functional distance" scores between the alleles of donor and pt, based on 12 polymorphic AA in HLA-DPB1 exon 2 (Crivello, Blood 2016); IV) mismatches in the rs9277534 single-nucleotide polymorphism in the HLA-DPB1 3′ UTR region, predicted on the basis of the DPB1 genotype (Schöne, Hum Immunol 2018), and previously shown to be associated to the expression levels of HLA-DPB1 molecules (HLAexp, Petersdorf, NEJM 2015). Indication for HSCT was acute leukemia (55%), lymphoma and multiple myeloma (29%), myelodysplastic and myeloproliferative syndromes (16%). According to EBMT score definition, 45% of pts were in early, 26% in intermediate, and 29% in advanced disease status. Conditioning regimens were myeloablative (64%) or reduced intensity (36%). Peripheral blood was the preferred stem cell source (81%). Graft-versus-host disease (GvHD) prophylaxis was based on anti-thymocyte globulin (ATG) in 91% of pts, mostly associated with cyclosporine and methotrexate (81%). Median follow-up was 3.2 y. Results: Among the four models adopted to classify functional HLA-DPB1 matching, the TCE4 provided the best results in predicting mm that were permissive (P) or non permissive (NP) for HSCT outcomes. By this model, P mismatched pairs (N=135) had a significantly superior 3-y overall survival (OS) and Graft-versus host disease and Relapse-Free Survival (GRFS) compared to NP pairs (N=247) (60±8% vs 49±7%, p .05; and 36±8% vs 29±5%, p .04). This was associated with a higher transplant-related mortality (TRM), 30±6% in NP mm and 21±6% in P mm, p .09 and a higher 3-y CI of extensive cGvHD in NP mm (12±4%) compared to P (4±2%), p .01 (Figure 1). No effect was found for relapse incidence. Cox multivariate analysis (adjusted for pt age, donor/host gender and CMV, disease status, Sorror score, conditioning intensity, stem cell source, ATG use, HLA matching on 5 loci, center effect), showed that a NP mm compared to P mm was associated with higher hazards for OS (HR 1.6, p .01), GRFS (HR 1.4, p .02), TRM (HR 1.9, p .01), cGvHD (HR 1.6, p .03) and extensive cGvHD (HR 3.6, p Of the 382 transplants with HLA-DPB1 mismatches, 229 had unidirectional mismatches in GvH direction and thus could be classified by the HLAexp model. The predicted expression level of the mismatched allele in the patient was associated with 100-d CI of grade≥2 aGvHD: 32±10% in high expression (N=76) versus 16±6% in low expression (N=153) mismatched alleles, p No significant associations with clinical outcomes were found for the "delta functional distance" or the TCE3 model, respectively. Conclusions: Our study provides further proof that functional HLA-DPB1 matching is crucially associated to UD-HSCT outcome also in recent transplants, and suggest that, at least in the cohort under analysis, mainly composed of Italian pts transplanted using an ATG-based prophylaxis, the TCE4 model appears superior to other models in stratifying risk groups and predicting survival. Figure. Figure. Disclosures Patriarca: Medac: Other: Travel, accommodations, expenses; Jazz: Other: Travel, accommodations, expenses; Celgene: Other: Advisory Role; Travel, accommodations, expenses; Janssen: Other: Advisory role; MSD Italy: Other: Advisory Role. Rambaldi:Italfarmaco: Consultancy; Roche: Consultancy; Omeros: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Amgen Inc.: Consultancy. Fleischhauer:GENDX: Research Funding. Vago:GENDX: Research Funding; Moderna TX: Research Funding.

The use of posttransplant cyclophosphamide (PT-Cy) as graft-versus-host disease (GVHD) prophylaxis has revolutionized haploidentical hematopoietic stem cell transplantation (HSCT), allowing safe infusion of unmanipulated T cell-replete grafts. PT-Cy selectively eliminates proliferating alloreactive T cells, but whether and how it affects natural killer (NK) cells and their alloreactivity is largely unknown. Here we characterized NK cell dynamics in 17 patients who received unmanipulated haploidentical grafts, containing high numbers of mature NK cells, according to PT-Cy-based protocols in 2 independent centers. In both series, we documented robust proliferation of donor-derived NK cells immediately after HSCT. After infusion of Cy, a marked reduction of proliferating NK cells was evident, suggesting selective purging of dividing cells. Supporting this hypothesis, proliferating NK cells did not express aldehyde dehydrogenase and were killed by Cy in vitro. After ablation of mature NK cells, starting from day 15 after HSCT and favored by the high levels of interleukin-15 present in patients' sera, immature NK cells (CD62L+NKG2A+KIR-) became highly prevalent, possibly directly stemming from infused hematopoietic stem cells. Importantly, also putatively alloreactive single KIR+ NK cells were eliminated by PT-Cy and were thus decreased in numbers and antileukemic potential at day 30 after HSCT. As a consequence, in an extended series of 99 haplo-HSCT with PT-Cy, we found no significant difference in progression-free survival between patients with or without predicted NK alloreactivity (42% vs 52% at 1 year, P = NS). Our data suggest that the majority of mature NK cells infused with unmanipulated grafts are lost upon PT-Cy administration, blunting NK cell alloreactivity in this transplantation setting.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the most powerful therapy preventing relapse in patients with adverse cytogenetics acute myeloid leukemia (AML) in first complete remission (CR1). In the absence of a matched related donor, potential alternatives include 10/10, 9/10 HLA-matched unrelated (UD) or haploidentical (Haplo) donors. We analyzed clinical outcomes of patients undergoing T-cell repleted Haplo (n = 74), 10/10 UD (n = 433) and 9/10 UD HSCT (n = 123) from 2007 to 2015, reported to the EBMT Registry. Adverse risk AML was defined according to the 2017 ELN cytogenetic risk classification. The 2-year nonrelapse mortality was 19% for Haplo, 18% for 10/10 UD and 18% for 9/10 UD (P = .9). The relapse incidence was not significantly affected by donor source, with a 2-year incidence of 27% for Haplo HSCT, 39% for 10/10 UD and 37% for 9/10 UD SCT (P = .3). We show comparable probabilities of leukemia-free survival (LFS) and overall survival (OS) at 2 years among Haplo HSCT, 10/10 UD SCT and 9/10 UD SCT (53% and 59%, 43% and 50%, 44% and 50%, respectively, P = .5 for both parameters). The type of donor was not significantly associated with either acute or chronic graft-vs.-host disease incidence. Using multivariable Cox model, Haplo HSCT recipients experienced comparable OS and LFS to 10/10 and 9/10 UD. In the present series of adverse cytogenetics AML patients in CR1, Haplo HSCT recipients had comparable outcomes to those of 10/10 and 9/10 UDs, suggesting that all these types of HSCT may be considered a valid option in this high risk population.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with unmanipulated grafts is increasingly adopted for high-risk acute leukemia, with acute graft-versus-host disease (aGVHD) prophylaxis based on antithymocyte globulin (ATG) or posttransplant cyclophosphamide (PTCy) as main platforms. No consensus exists on selection criteria over several haploidentical donors. We evaluated the impact of donor-recipient antigenic and allelic HLA-A, -B, -C, and -DRB1 mismatches on mismatched haplotype on outcomes of 509 unmanipulated haplo-HSCTs performed for acute leukemia under a PTCy (N = 313) or ATG (N = 196) regimen. An antigenic but not allelic mismatch at the HLA-DRB1 locus was an independent risk factor for grade ≥2 aGVHD in PTCy (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.2-4.0; P = .02) but not in ATG regimens (HR, 1.3; 95% CI, 0.4-3.4; P = .6). Moreover, the hazards of aGVHD were significantly associated with other factors influencing alloreactivity, including peripheral blood as stem cell source (HR, 2.2; 95% CI, 1.4-3; P < .01), reduced-intensity conditioning (HR, 0.6; 95% CI, 0.4-0.9; P = .04), and female donors (HR, 1.8; 95% CI, 1-3.2; P = .05), in PTCy but not ATG regimens. No significant associations were found between cumulative number of HLA mismatches and GVHD, or between HLA-matching status and other study end points including transplant-related mortality, disease-free survival, and relapse. Based on these data, the role of HLA mismatching on unshared haplotype appears not to be sufficiently prominent to justify its consideration in haploidentical donor selection. However, the role of HLA matching in haploidentical HSCT might be modulated by GVHD prophylaxis, calling for further investigations in this increasingly relevant field.

Introduction: HLA molecules play an important role for immunoreactivity in allogeneic hematopoietic stem cell transplantation (HSCT). To elucidate the effect and the potential identification of "permissive" and "non permissive" I and II class HLA mismatching (mm) loci on the early and long term transplant outcome, we conducted a retrospective/prospective observational analysis on 1789 patients transplanted with unmanipulated haematopoietic stem cells from a volunteer unrelated donor (URD). Methods Between January 2012 to December 2015, 1789 adult patients with a median age of 49 years (18-70) affected by haematological malignant diseases, performed an unrelated HSCT, coordinated by the Italian Bone Marrow Donor Registry (IBMDR). All patients have been typed by high resolution (HR) HLA typing for HLA-A/B/C/DRB1/DQB1 loci, at the start of the donor's search process. Patient and donor characteristics are shown in Table 1. As conditioning regimen and GVHD prophylaxis, 71% of patients received a myeloablative conditioning and 76% a combination of anti-Thymoglobuline, Cyclosporine and Metotrexate short course. Total Body Irradiation was part of conditioning regimen in 14% of cases and PBSC was used as stem cell source in 80% of transplants. Median follow for survivors was 38 months (1-76). Regarding to the allelic compatibility, 890 (50%) of donor/recipient (D/R) pairs were 10/10 HLA matched, 677 (38%) showed 1 mm for A, B, C, DRB1 or DQB1 in 249, 141, 173, 2 and 112 cases, respectively and 222 (12%) received HSCT from a 8/10 or less HLA matched donor. Results: Overall 90% and 79% of patients achieved PMN and PLTS engraftment within 30 and 90 days, respectively. Probabilities of 3-y Overall Survival (3-yr OS), Progression Free Survival (3-yr PFS), and Graft Relapse Free Survival (3-yr GRFS) were 52%, 42%, and 30%, respectively. The 3-y CI of Transplant Related Mortality (TRM) was 26%, with a 100-days CI of acute GVHD ≥2 of 26%, whereas the 3-yr CI of chronic GVHD was 30%, of which 10% extensive. Cox multivariate analysis showed that, compared to 10/10 HLA-matched HSCT, 9/10 and ≤8/10 HLA-matched HSCT were associated with worse outcomes in terms of OS (HR 1.16, p=0.04 and HR 1.3, p=0.007, respectively), GRFS (HR 1.2, p=0.005 and HR 1.2, p=0.07, respectively), TRM (HR 1.3, p=0.007 and HR 1.6, p 5%: the presence of A02:01 in the patient's HLA, after adjustment for HLA matching at the other loci and other clinical variables known to affect HSCT outcome, was associated with significant higher risk of TRM (HR 1.9, p= 0.03) and worst OS (HR 1.7, p=0.04). Patient's age > 49 years (p10 HSCT/year) is associated with reduced TRM (HR 0.8, p=0.0001), HSCT from female donor to male recipient was associated with higher risk of extensive cGvHD (HR 1.4, p=0.03), and CMV negative/negative status versus other combinations had protective effect on development of grade 3-4 aGVHD (HR 0.56, p=0.04). Conclusions: Our large cohort data of homogeneously treated 1789 URD transplants, show that 10/10 HLA matching remains a significantly favorable prognostic factor for OS, TRM, GRFS and acute/chronic GVHD, whereas there are no significant differences between 8/10 and 9/10 matching transplants. Moreover, the HLA A02:01 as single mm seems to play a "non permissive" role. Finally the Italian origin of recipient and donor is related to a reduced development of GVHD probably due to the matching of the extended MHC haplotypes in individuals of the same geographic origin. Disclosures Rambaldi: Amgen Inc.: Consultancy; Pfizer: Consultancy; Celgene: Consultancy; Omeros: Consultancy; Roche: Consultancy; Novartis: Consultancy; Italfarmaco: Consultancy. Vago:Moderna TX: Research Funding; GENDX: Research Funding. Patriarca:Janssen: Other: Advisory role; Jazz: Other: Travel, accommodations, expenses; Medac: Other: Travel, accommodations, expenses; Celgene: Other: Advisory Role; Travel, accommodations, expenses; MSD Italy: Other: Advisory Role.

Introduction Allogeneic stem cell transplantation (HCT) survivors are at a relevant risk of developing long-term complications such as chronic GvHD (cGvHD), which importantly affects their quality of life and increases their morbidity and mortality. Being able to early identify high risk patients would enable us to tailor preventive strategies. Current approach on prophylaxis of GvHD is lacking of predictive biomarkers that could guide patient-tailoring of drugs choice, tapering and treatment schedules. Immune system is the cause of cGvHD but is also a target of it, and cGvHD patients are characterized by lymphoid hypocellularity. Moreover, immune reconstitution (IR) is a good candidate biomarker being it an easily-available and reproducible parameter. We investigated IR variables as predictive biomarker of cGvHD. Methods A standardized follow-up of HCT-survivors is applied at our center. We analyzed 307 adult patients consecutively undergoing first allogeneic HCT transplant between July 2012 and December 2016 at our Institution. A written consent was given for the use of medical records for research in accordance with the Declaration of Helsinki. Median follow-up for surviving patients was 2.8 years (range 1.1-5.5). We prospectively collected IR data of our entire cohort at specific time-points (+30, +60, +90, +180, +365 days) and followed patients up recording events. IR variables were CD3+, CD3+CD4+, CD3+CD8+, CD19+, CD56+ cell counts, measured by flow-citometry, and immunoglobulins IgG, IgA and IgM levels, measured by immunoturbidimetric assays. Time as a continuous parameter could not be studied since the number of events would have been too low for the analysis. For this reason, a series of landmark analyses were performed at 3, 6 and 12 months post-HCT in order to identify predictive factors of cGvHD, transplant-related mortality (TRM), progression-free survival (PFS) and overall survival (OS) for patients alive and in good conditions at the beginning of each time interval. Factors predicting cGvHD incidence and survival endpoints were studied using multivariate analysis by Cox regression model. Variables included in the model were patient and donor age and Sorror-Comorbidity Index (according to median values), disease-related index, type of donor, stem cell source, IR values at the timepoint according to landmark cut-off for cell counts and median values for immunoglobulin levels. A backward stepwise procedure was used for variable selection with a p-value Results Chronic-GvHD of any grade and severity was diagnosed in 111 patients. Immune recovery in our cohort was in line with the current knowledge: CD3+CD8+ and NK (CD56+) cells normalized first, followed by CD3+ and CD3+CD4+ cell. B cells (CD19+) took at least 1 year to normalize in terms of absolute counts. IgM levels were the first to rise among immunoglobulins, followed by IgG and then IgA which can also be subnormal for a long time after transplant. Results of multivariate analysis are shown in Table 1. Single lymphocyte subset counts did not prove to be associated to cGvHD onset significantly; conversely, immunoglobulins were strongly predictive of cGvHD in our multivariate model. Median time to GvHD onset was 198 days, thus the most important analysis was the one performed at +90 days as the majority of patients had still not developed cGvHD. IgG, IgA and IgM at +90 days from HCT below the median value were found before the onset of GvHD and could predict its onset. This data were confirmed on the analysis at later time-points in which low IgG levels predicted cGvHD diagnosis. Conclusions Day-90 low immunoglobulin levels predict cGvHD, confirming that subclinical immune dysregulation mechanisms could be already present before overt clinical onset of cGvHD symptoms. Early prediction of subsequent cGvHD will be operationally translated into patient-tailored preventive measures. Disclosures Bonini: Intellia Therapeutics: Research Funding.

Introduction Allogeneic stem cell transplantation (allo-HCT) survivors are at a defined relevant risk of developing long-term complications: the prevalence of chronic health conditions approaches 75% among HCT survivors. The endocrine system is one of the most frequent targets of complications, providing justification for a long-term and continuous follow-up (LTFU) to assure a timely and appropriate treatment. The aim of our study is to evaluate the incidence of endocrinopathies in survivors in respect of sex, age, donor type, conditioning regimen and GvHD occurrence. Methods A standardized LTFU is applied at our center. We here analyze data consecutively collected in an Institutional database, starting from 2006, including 402 adult patients (pts) who underwent an allo-HCT between 1992 and 2016 at our Institution. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. We considered for the analysis pts with an overall survival >/=1y. We reviewed pts chapters with a focus on occurrence, management and treatment of diabetes, thyroid disfunctions, dyslipidemia and osteopenia / osteoporosis: diagnosis and follow-up were performed according to guidelines for long-term HCT survivors. Results With a median follow-up of 7y (r 2-25y) 328 pts were evaluable; donor was a match unrelated donor in 107 cases, HLA identical sibling in 88, haploidentical relative in 129 and cord blood in 4. The 5y-incidence of diabetes type 2 was 3%, with a median time after allo-HCT of 1138 days (r 5-4181 days); 13/22 developed diabetes after diagnosis of GvHD (median time 884 days, r 30-3753 days). All pts received indication for diet modification, 11 pts were treated with insulin and 8 pts with metformin. Thyroid disfunction was documented in 38 pts (5y-incidence 8,5%): 2 pts were diagnosed with hyperthyroidism and treated with methimazole or radioiodine treatment. Hypothyroidism was documented in 36 pts (median time after allo-HSCT 799 days, r 65-5021 days). Thirteen pts developed hypothyroidism following the diagnosis of GvHD (median time 1236 days, r 166-3540 days). Only 2 pts did not receive a specific treatment, while all the others received substitutive therapy with levothyroxine. Furthermore 1 pt was diagnosed with a papillary thyroid cancer. The 5y-incidende of dyslipidemia was 30% with a median time after allo-HSCT of 1433 days (r 366-7629), 47 pts developed dyslipidemia after the diagnosis of GVHD (median time 1425 days, r 134-7403 days). Diet-therapy was recommended to all the pts, 29 pts received a statin-based pharmacological treatment, 20 pts a polyenoic-fatty-acids based treatment, while a nutraceutical compound was given in 13 pts. Osteopenia was documented in 120 pts (median time after allo-HSCT 994 days, range 31-6605 days) with a 5y-incidence of 36%. Seventy-nine pts presented osteopenia after diagnosis of GvHD (median time after GvHD diagnosis 707 days, r 13-6379 days). Eight pts did not receive a specific treatment. Two pts received treatment with biphosphonates plus oral vitamin D and calcium supplementation, the 110 remaining pts received oral vitamin D +/- calcium supplementation only. Sixty-four pts developed osteoporosis (median time after allo-HSCT 1000 days, r 60-8836 days), the 5y-incidence was 26%. Forty-four pts developed osteoporosis following the diagnosis of GvHD (median time 724 days, r 28-8280 days). Only 4 pts did not receive any specific therapy; 31 pts received therapy with bisphosphonates, 2 pts denosumab and 27 pts oral vitamin D and calcium supplementation. In univariate analysis no relationship between host sex, age at transplant, TBI exposure, donor or history of GvHD and development of diabetes, thyroid disfunction and dyslipidemia was outlined. Otherwise, osteopenia development was strongly associated with GvHD occurrence and osteoporosis was strongly associated with age, sex and GvHD occurrence (table 1). Conclusions Allo-HCT survivors are at relevant risk of endocrinopathies after transplantation, providing justification for specific monitoring to individualize treatment and follow-up. Of note, classical transplant-related variables are not enough to justify the occurrence of endocrinological disfunction: a further deeper evaluation of a misdiagnosed donor-mediated autoimmune predisposition will be essential. Disclosures Bonini: Intellia Therapeutics: Research Funding.

Introduction: Post transplant cyclophosphamide (PT-Cy) has recently emerged as a very promising pharmacological strategy to overcome human leukocyte antigen (HLA) barriers in the setting of haploidentical hematopoietic cell transplant (HCT). We recently reported a promising preliminary experience on the use of PT-Cy and sirolimus as graft-versus-host disease (GVHD) prophylaxis in matched allo-HSCT (Greco R et al, Blood 2016). Herein we describe long-term outcomes of matched allogeneic HSCT, using treosulfan-based conditioning, and GVHD prophylaxis with PT-Cy and sirolimus. Methods: In our center, we collected 104 adult patients (pts) receiving matched HSCT for high-risk hematological malignancies, mainly acute myeloid leukemia (n=43). Donor was matched related (MRD) for 45 pts, 10/10 matched unrelated (MUD) for 39 pts and 9/10 MUD for 20 pts. Median age was 48 years (range 19-78). At HSCT, 51% of patients were not in complete remission (CR), 39% were in CR1 and 11% in subsequent CR. Graft source was mainly PBSCs (95%). All pts received a conditioning regimen based on treosulfan and fludarabine; 89% received an intensified conditioning with the addition of melphalan. All pts received PT-Cy (50 mg/kg/day) on days 3 and 4. Sirolimus was given from day 5, and withdrawn 3 months after HSCT. Mycophenolate mofetil (MMF) was added from day 5 to day 30, only in MUD. All patients were treated according to current institutional programs upon written informed consent for transplant procedures. Results: Median follow up was over 16 months (range 3-51). Median CD34+ and CD3+ cell doses were 5.6x10^6/Kg (range, 1.5-10.9) and 2.0x10^8/Kg (range, 0.2-8.0), respectively. All the recipients of allo-HSCT experienced a sustained donor cell engraftment. The cumulative incidence of grades II-IV and III-IV acute GVHD at 100 days was 21% and 9%, respectively. The cumulative incidence of chronic GVHD was 25% at 2 years; we observed severe chronic GVHD only in 4% of pts. The cumulative incidences of relapse and non-relapse mortality (NRM) were 33% and 8% at 2 years, respectively. Two-year overall survival (OS) was 67% and progression free survival (PFS) 59%. The composite end point of GVHD-free/relapse-free survival (GRFS) was 52% at 2 years, in which events include grade 3-4 acute GVHD, systemic therapy-requiring chronic GVHD, relapse, or death. There was a longer OS, 2-year OS was 77% (p = 0.05), and a trend towards higher PFS and GRFS, 63% (p=0.07) and 58% (p=0.06) respectively, for pts with CR status at HSCT. We did not found a significant effect of HLA-matching (9/10 versus 10/10) or donor type (related versus unrelated) on major transplant outcomes (NRM, PFS, GRFS, relapse, acute and chronic GvHD). Conclusion: These outcomes confirmed that matched allogeneic HSCT using treosulfan-based chemotherapy, PT-Cy and sirolimus, is associated with low NRM and acceptable severe GVHD, providing relevant long-term survival in high-risk diseases. A randomized trial comparing this strategy with other kind of in-vivo T-cell depletion (i.e. ATG) is warranted. Disclosures Vago: Moderna TX: Research Funding; GENDX: Research Funding.

Background The aim of the study was to estimate the cumulative incidence of pre-engraftment blood stream infections (PE-BSI), its predictive factors and the infection-related mortality (IRM) after hematopoietic cell transplantation (HCT) from any donor type, with post-transplant cyclophosphamide (PT-Cy). Methods Retrospective cohort study on 235 adults who underwent peripheral blood HCT from every donor type with PT-Cy platform, from 2013 to 2017 at San Raffaele Scientific Institute. The Poisson regression was used to estimate the crude incidence rate (IR) of PE-BSI. The Fine-Gray competing risk model was applied to estimate the cumulative incidence function (CIF) of the first PE-BSI and its predictive factors and of IRM. Results Patients’ characteristics are reported in Table 1. During 5,316 person-days of follow-up (PDFU), 77 PE-BSI episodes occurred in 72 patients: IR = 1.45 per 100-PDFU [95% confidence interval (95% CI) 1.13–1.77]. The median time to PE-BSI was 13 days (IQR: 7–17) and the estimated CIF at 28 days was 32% (95% CI: 26–39%); no differences in CIF according to donor type [30% vs. 34% vs. 32% in match-related, match-unrelated and haploidentical donor, respectively; Gray’s test: P = 0.968]. Among the 87 isolated pathogens, 60% were Gram-positive bacteria (GPB), 39% Gram-negative bacteria (GNB) and 1% nontuberculous mycobacteria. CIFs of GNB and GPB PE-BSI by type of donor are shown in Figure 1. By multivariate analysis (Table 2), after adjustment for age, sex, year of HCT, donor type and disease phase at HCT, the CIF of any PE-BSI was higher in subjects with absolute neutrophils count ≤500 for ≥7 days before HCT [adjusted hazard ratio (AHR) = 2.90] and in multi-drug resistant (MDR) GNB rectal carriers before HCT [AHR = 2.68]. These covariates were confirmed as independent factors also for GNB PE-BSI. Overall, IRM at 30 days was 5% (95% CI: 2–8%) with no differences by donor type (Gray’s test: P = 0.106). Conclusion HCT with PT-Cy platform showed a 32% of cumulative incidence of PE-BSI at 28 days and donor type did not affect its occurrence, which was conversely increased by prolonged and severe neutropenia and MDR GNB rectal carriage before HCT. Haploidentical setting did not retain a higher IRM at 30 days than match-related and match-unrelated donors. Disclosures All authors: No reported disclosures.

Human herpesvirus 6 (HHV-6) is increasingly recognized as a potentially life-threatening pathogen in allogeneic hematopoietic stem cell transplantation (alloSCT). We retrospectively evaluated 54 adult patients who developed positivity to HHV-6 after alloSCT. The median time from alloSCT to HHV-6 reactivation was 34 days. HHV-6 was present in plasma samples from 31 patients, in bone marrow (BM) of 9 patients, in bronchoalveolar lavage fluid and liver or gut biopsy specimens from 33 patients, and in cerebrospinal fluid of 7 patients. Twenty-nine patients developed acute graft-versus-host disease (GVHD), mainly grade III-IV, and 15 had concomitant cytomegalovirus reactivation. The median absolute CD3+ lymphocyte count was 207 cells/µL. We reported the following clinical manifestations: fever in 43 patients, skin rash in 22, hepatitis in 19, diarrhea in 24, encephalitis in 10, BM suppression in 18, and delayed engraftment in 11. Antiviral pharmacologic treatment was administered to 37 patients; nonetheless, the mortality rate was relatively high in this population (overall survival [OS] at 1 year, 38% ± 7%). A better OS was significantly associated with a CD3+ cell count ≥200/µL at the time of HHV-6 reactivation (P = .0002). OS was also positively affected by the absence of acute GVHD grade III-IV (P = .03) and by complete disease remission (P = .03), but was not significantly influenced by steroid administration, time after alloSCT, type of antiviral prophylaxis, plasma viral load, or organ involvement. Although HHV-6 detection typically occurred early after alloSCT, better T cell immune reconstitution seems to have the potential to improve clinical outcomes. Our findings provide new insight into the interplay between HHV-6 and the transplanted immune system.

To the editor: Graft-versus-host disease (GVHD), both acute and chronic, is still a leading cause of nonrelapse mortality after transplantation.[1][1] High-dose, posttransplantation cyclophosphamide (PTCy) is an attractive approach for in vivo allodepletion across the HLA barrier in allogeneic