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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.

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.

Post-transplantation cyclophosphamide (PTCy) has emerged as a promising graft-versus-host-disease (GVHD) prophylaxis in the setting of allogeneic hematopoietic stem cell transplantation (HSCT) from haploidentical donors and more recently in matched donor transplants. Herein, we describe our real-life experience on 249 adult patients undergoing allogeneic HSCT, from HLA-matched related (MRD), HLA-matched unrelated (MUD), or mismatched related donors (MMRD). Patients received unmanipulated peripheral blood stem cells (PBSCs), using a GVHD prophylaxis with PTCy and sirolimus. Mycophenolate mofetil was added in MUD or MMRD. In the HLA-matched donor group (MRD, n = 48, MUD, n = 50), the cumulative incidence of grades II-IV and III-IV acute GvHD was 23% and 9% at 100 days, respectively. The cumulative incidence of chronic GvHD was 25% at 2 years, severe only for 5% of the patients. The cumulative incidences of relapse and transplant-related mortality (TRM) were 31% and 9% at 2 years, respectively. The 2-year overall survival (OS) was 72% and progression-free survival (PFS) 60%; the composite endpoint of GvHD/relapse-free survival (GRFS) was 52% at 2 years. In the haploidentical donor group (n = 151), we documented a cumulative incidence of grades II-IV and III-IV acute GVHD of 35% and 20% at 100 days, respectively, and a cumulative incidence of chronic GvHD of 39% at 2 years. We observed severe chronic GVHD in 15% of the patients. The cumulative incidence of relapse and TRM was 32% and 25% at 2 years, respectively. The 2-year OS was 48%, whereas PFS was 43%; GRFS was 28% at 2 years. However, more patients in the haploidentical group presented high/very high disease risk index (DRI) and higher HCT-comorbidity index. In patients classified in the low-intermediate DRI, 2-year GRFS was 53% in MRD, 65% in MUD, and 46% in haploidentical HSCT (P = .33). Sirolimus-PTCy platform deserves further investigation as an alternative to calcineurin-inhibitor–based GVHD prophylaxis for all donor sources. In patients presenting a low-intermediate DRI, this strategy translates in relevant survival independently from the transplant source.

HLA molecules are important for immunoreactivity in allogeneic hematopoietic stem cell transplantation (HSCT). The Gruppo Italiano Trapianto di Cellule Staminali e Terapie Cellulari, Italian Bone Marrow Donor Registry, and Associazione Italiana di Immunogenetica e Biologia dei Trapianti promoted a retrospective observational study to evaluate HLA matching and the impact of allelic HLA mismatching and non-HLA factors on unrelated Italian HSCT outcomes. From 2012 to 2015, 1788 patients were enrolled in the study. The average donor age was 29 years and the average recipient age was 49 years. As a conditioning regimen, 71% of the patients received myeloablative conditioning. For GVHD prophylaxis, 76% received either antithymocyte or anti-T lymphocyte globulin, cyclosporine A, and methotrexate. Peripheral blood was the stem cell source in 80%. The median duration of follow-up was 53 months. Regarding HLA matching, 50% of donor-recipient pairs were 10/10 matched, 38% had 1 mismatch, and 12% had 2 or more mismatches. A total of 302 pairs shared Italian origin. Four-year overall survival (OS), progression-free survival, GVHD-free relapse-free survival, and relapse rates were 49%, 40%, 22%, and 34%, respectively. The 4-year NRM was 27%, and the 100-day cumulative incidence of grade ≥II acute GVHD (aGVHD) was 26%. In multivariate analysis, 9/10 and ≤8/10 HLA allele-matched pairs were associated with worse OS (P = .04 and. 007, respectively), NRM (P = .007 and P < .0001, respectively), and grade III-IV aGVHD (P = .0001 and. 01, respectively). Moreover, the incidences of grade II-IV aGVHD (P = .001) and chronic GVHD (P = .002) were significantly lower in Italian pairs. In conclusion, 10/10 HLA matching is a favorable prognostic factor for unrelated HSCT outcome in the Italian population. Moreover, the presence of 2 HLA-mismatched loci was associated with a higher NRM (P < .0001) and grade II-IV aGVHD (P = .006) and a poorer OS (P = .001) compared with 1 HLA-mismatched locus in early or intermediate disease phases. Finally, we found that Italian donor and recipient origin is a favorable prognostic factor for GVHD occurrence.

CMV represents one of the most serious life-threatening complications of allogeneic stem cell transplantaion (allo-SCT). Pre-emptive treatment is highly effective, but toxicity and repetitive reactivation of CMV represent a major challenge in the clinical practice. The use of anti-CMV specific immunoglobulins (Megalotect) is controversial. We retrospectively collected data on 92 patients submitted to allo-SCT for hematological malignancies, in whom Megalotect was used either for prophylaxis (n=14) or with pre-emptive therapy (n=78). All the patients were considered at high-risk of developing CMV reactivation and CMV disease. The treatment was well tolerated, with no reported infusion reactions, nor other adverse events. None of the 14 cases treated with Megalotect as prophylaxis developed CMV reactivation. 51/78 (65%) patients who received Megalotect during pre-emptive treatment achieved complete clearance of CMV viremia, and 14/51 patients (29%) developed a breakthroug CMV infection. 7/78 patients (9%) developed CMV disease. The projected 1-year OS, 1-year TRM and 1-year RR is 74%, 15% and 19%, respectively. No differences were observed in terms of OS, TRM and RR by comparing patients who achieved a complete response after treatment versus those who did not.. These retrospective data suggest that Megalotect is safe and well tolerated. When used as prophylaxis, no CMV reactivation was recorded. We have no conclusive data regarding its efficacy in reducing the cumulative dose of anti-CMV specific drugs in the pre-emptive setting. Further prospective trials are warrented to identify the best setting of patients who can benefit from Megalotect alone or in addition to anti-CMV specific drugs.

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.

Carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) infections are an emerging cause of death after hematopoietic stem cell transplantation (HSCT). In allogeneic transplants, mortality rate may rise up to 60%. We retrospectively evaluated 540 patients receiving a transplant from an auto- or an allogeneic source between January 2011 and October 2015. After an Institutional increase in the prevalence of KPC-Kp bloodstream infections (BSI) in June 2012, from July 2012, 366 consecutive patients received the following preventive measures: (i) weekly rectal swabs for surveillance; (ii) contact precautions in carriers (iii) early-targeted therapy in neutropenic febrile carriers. Molecular typing identified KPC-Kp clone ST512 as the main clone responsible for colonization, BSI and outbreaks. After the introduction of these preventive measures, the cumulative incidence of KPC-Kp BSI (P=0.01) and septic shocks (P=0.01) at 1 year after HSCT was significantly reduced. KPC-Kp infection-mortality dropped from 62.5% (pre-intervention) to 16.6% (post-intervention). Day 100 transplant-related mortality and KPC-Kp infection-related mortality after allogeneic HSCT were reduced from 22% to 10% (P=0.001) and from 4% to 1% (P=0.04), respectively. None of the pre-HSCT carriers was excluded from transplant. These results suggest that active surveillance, contact precautions and early-targeted therapies, may efficiently control KPC-Kp spread and related mortality even after allogeneic HSCT.

Haploidentical hematopoietic stem cell transplantation (HSCT) performed using bone marrow (BM) grafts and post-transplantation cyclophosphamide (PTCy) has gained much interest for the excellent toxicity profile after both reduced-intensity and myeloablative conditioning. We investigated, in a cohort of 40 high-risk hematological patients, the feasibility of peripheral blood stem cells grafts after a treosulfan-melphalan myeloablative conditioning, followed by a PTCy and sirolimus-based graft-versus-host disease (GVHD) prophylaxis (Sir-PTCy). Donor engraftment occurred in all patients, with full donor chimerism achieved by day 30. Post-HSCT recovery of lymphocyte subsets was broad and fast, with a median time to CD4 > 200/mu L of 41 days. Cumulative incidences of grade II to IV and III-IV acute GVHD were 15% and 7.5%, respectively, and were associated with a significant early increase in circulating regulatory T cells at day 15 after HSCT, with values < 5% being predictive of subsequent GVHD occurrence. The 1-year cumulative incidence of chronic GVHD was 20%. Nonrelapse mortality (NRM) at 100 days and 1 year were 12% and 17%, respectively. With a median follow-up for living patients of 15 months, the estimated 1-year overall and disease-free survival (DFS) was 56% and 48%, respectively. Outcomes were more favorable in patients who underwent transplantation in complete remission (1-year DFS 71%) versus patients who underwent transplantation with active disease (DFS, 34%; P = .01). Overall, myeloablative haploidentical HSCT with peripheral blood stem cells (PBSC) and Sir-PTCy is a feasible treatment option: the low rates of GVHD and NRM as well as the favorable immune reconstitution profile pave the way for a prospective comparative trial comparing BM and PBSC in this specific transplantation setting. (C) 2015 American Society for Blood and Marrow Transplantation.

Introduction Allogeneic hematopoietic cell transplantation (HCT) is an effective therapeutic option for high-risk hematological malignancies; 80% of those who survive the first 2 years are expected to become long-term survivors. The prevalence of chronic health conditions approaches 75% among HCT survivors and that for severe or life-threatening conditions exceeds 20%. Patients and Methods A standardized follow-up of HCT survivors is applied at our Center, according to Jacie Standards. Here we report the analysis of data collected between July 2014 and July 2015 in 260 adult patients (pts) who underwent an HCT between 1992 and 2014. Data on 7 items - selected to monitor relevant comorbidities - were prospectively collected in our Institutional database. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. Results Pts characteristics are reported in table 1, median time of follow-up 4.4y (r1-22), cumulative follow-up 1404y; 13 pts deceased during the time of observation (6 due to disease relapse, 2 to late major infection, 2 to second cancer, 1 to GvHD, 1 to myocardial infarction, 1 unknown). - chronic Graft-versus-Host-Disease (c-GvHD): at a median follow-up of 43 months (r 16 months - 21 years) 84 (32%) pts are presenting c-GvHD features. According to NIH 2014 consensus criteria 23 cases were classified as mild, 32 moderate, 29 severe. Median number of involved organs 2 (r1-5), 39 pts were experiencing skin lesions, 55 eyes, 28 mouth, 19 joint and fascia, 18 lungs. Topical therapy was the treatment of choice for mild cases, while moderate and severe were treated with systemic therapy. The partnership with the lung specialist and the ophthalmologist was crucial for the management of lung and eyes GvHD. - Late infectious manifestation: 38 (15%) pts present late infection, 2 pts deceased due to major events. Of note pneumonia was reported in 12 pts, Varicella Zoster virus reactivation in 7, CMV late reactivation in 4 pts. - Second cancer screening was performed according to international guidelines. The incidence of new cases is 10% (26 pts) and 11 pts are actually under work-up for suspicious lesions. Non-melanoma skin cancer was the most frequent diagnosis (13 cases); 3 pts were diagnosed with cervix cancer, 2 with lung cancer. The prevalence of second cancer in our population is 18% (47 cases). All pts were treated according to standard for general population, 45/47 are alive. - Cardiovascular diseases were frequently observed in our setting: hypertension was documented in 36 pts, arterial diseases in 10 pts, cardiomyopathy in 28 pts. Overall 27% of pts were diagnosed with cardiovascular comorbidities. - Metabolic syndrome (MS) is reported as a very common complication in long-term survivors: 65 (25%) pts were presenting features of MS (3/5 among hypertension, dyslipidemia, raised fasting glucose, and central obesity). A concomitant thyroid dysfunction - requiring hormonal replacement - was present in 27/65 pts. - Secondary hemosiderosis was documented (with MRI and blood parameters) and treated in 39 pts (15%) - 8 pts received deferasirox while phlebotomy was used in 31. - Osteoporosis and bone loss were evaluated measuring bone mineral density using dual-energy X-ray absorptiometry; osteopenia was detected in 81 pts and osteoporosis in 42 (47%). Pts were evaluated in conjunction with the endocrinologist and treated according to the fracture risk score. According to donor source no difference were observed (Chi-square test - p ns) except for higher incidence of moderate/severe GvHD incidence in HLA identical sibling (p 0.0097) as compared to alternative donors. Discussion HCT survivors are at a defined relevant risk of developing long-term complications that have a direct impact on the morbidity and mortality.A multidisciplinary active screening within routine HCT long-term follow-up care is mandatory to enhance early diagnosis/treatment and overall outcome. The next challenge will be to enhance the primary prevention to reduce the incidence of preventable comorbidities. Table 1. patients characteristics N (range) Pts 260 Age At transplant 48y (10 - 76) At follow-up 54y (20 - 82) Male / Female 169 / 91 Diagnosis AML / ALL 106 / 33 MDS 27 HD / NHL 23 / 29 MM 14 CML 8 CLL 5 SAA / EPN 4 / 1 Others 10 Status at transplant CR / PD 169 / 91 Donor Haploidentical 100 HLA identical Sibling 76 Match Unrelated Donor 82 Cord Blood 2 Disclosures Bonini: MolMed S.p.A: Consultancy.

Background Optimization of pre-transplant risk assessment is a crucial issue to improve the allo-HSCT decision making process. Actually 3 major algorithms are in use in clinical practice: the EBMT risk score, the Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) score and - more recently introduced - the refined Disease Risk Index (DRI). DRI was defined to calibrate HSCT outcome across studies and centers. It was developed as a tool to assign patients into risk groups based on disease type and status at the time of transplantation. The aim of the DRI is to provide a robust tool that can be used for prognostication, for the analysis and interpretation of retrospective data, whether conducted in single-center, multicenter, or registry settings, or within the context of the federally mandated center outcome reporting. The DRI can also be used for the stratification of patients entering prospective HCT clinical trials. DRI is not a fixed tool but instead it was conceived to be refined by the transplant community as new information becomes available. Here we are presenting the results of a retrospective study designed to evaluate the 3 aforementioned score in stratification and prognostication of transplant outcome after a haploidentical HSCT (haplo-HSCT). Patients and Methods We included 220 adult patients (pts - 138 male, 82 female) who underwent a haplo-HSCT for hematologic malignancies, between 2006 and 2014 and were reported to our Institutional database. Risk assessment score and outcome analysis included all consecutive pts receiving an haplo-HSCT as 1st allogeneic transplantation. Pts receiving haplo-HSCT as 2nd or 3rd HSCT were excluded from the present analysis. Median age was 49 years (range, 15-77). The cohort included a broad representation of diseases (138/220 acute leukemia, 30 Hodgkin lymphoma); 62 pts were in complete remission at transplant, 158 were presenting active disease. Conditioning regimens mostly rely upon the combination of treosulfan plus fludarabine (201/220) and total body irradiation (range 200 - 400 cGy) was utilized in 52 patients. GVHD prophylaxis consisted mostly of an mTor inhibitor (rapamycin) combined with mycophenolate mofetil. The majority of patients received peripheral blood stem cells from a family haploidentical donor as stem cell source, while only 4 patients received bone marrow transplant. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. Results The median follow-up for survivors was 37 months (r 6-107). The overall survival (OS) at 2-y was 35% and the transplant related mortality at 100-days 23%. The 2y OS according to EBMT / HCT-CI / DRI risk score are reported in table 1.a and figure 1. The evaluation of the HCT-CI impact after DRI stratification was able to show a significant difference in outcome showing better survival for pts with low DRI score and low HCT-CI score as expected (table 1.b). Discussion Refined DRI score and HCT-CI score predict survival after haplo-HSCT. The integrated application of refined DRI and HCT-CI may improve the definition of transplant eligibility for pts candidate to allogeneic HSCT form alternative donors including family haploidentical source. Table 1a. EBMT score 0-3 % pts 4-5 %pts > 5 %pts p 51% 17 34% 51 27% 32 0.07 HCT-CI score 0-2 3-4 >/= 5 48% 59 36% 31 0% 10 0.0001 DRI score Low-Intermediate High Very-High 61% 32 27% 51 5% 17 0.0001 Table 1b. HCT-CI 0-4 HCT-CI >/=5 p DRILow-Intermediate 64% 0% 0.0001 DRIHigh-Very High 29% 0% Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Human herpesvirus type 6 (HHV-6) is increasingly recognized as an opportunistic and potentially life-threatening pathogen in recipients of allogeneic hematopoietic stem cell transplantation (AlloSCT). HHV-6 is a member of the beta herpesvirus subfamily (genus Roseolovirus). HHV-6 infection is recognized as the cause of a febrile disease and exanthem subitum in early childhood. Approximately 60% of solid organ transplant and 40% of patients after alloSCT experienced HHV-6 reactivation. Reported clinical manifestations of HHV-6 infection in transplanted patients are skin rash, interstitial pneumonia, bone marrow suppression and encephalitis. Moreover, some clinical reports suggest that HHV-6 can facilitate the occurrence of severe clinical complications of alloSCT, increasing transplant-related mortality. METHODS: From January 2009 to February 2013, we retrospectively evaluated 54 consecutive adult patients (median age 50 years) who developed positivity to HHV-6 after alloSCT for high-risk hematological malignancies. Stem cell donors were family haploidentical (37), HLA identical sibling (8), unrelated volunteer (6), cord blood (3). The viral load was determined by quantitative PCR (Nanogen Advanced Diagnostic S.r.L) in cell-free body fluids such as plasma, bronchoalveolar lavage (BAL), cerebrospinal fluid (CSF), bone marrow (BM) aspirates or in gastrointestinal biopsies. RESULTS: Median time from alloSCT to HHV-6 reactivation was 34 days (range: 0-705). Thirty-one patients presented HHV-6 positive in plasma, 9/54 in BM, 33/54 in gut biopsies or BAL, 7/54 in CSF. At the time of viral positivity all pts were receiving acyclovir as viral prophylaxis except five. Twenty-nine patients had acute graft versus host disease (GvHD). Twenty-two out of these twenty-nine patients experienced a grade III-IV acute GvHD, requiring high dose steroids in twenty-six cases. A concomitant CMV positivity was detected in 15/54 patients. The median absolute count of CD3+ lymphocytes was 207 cells/mcl. In 52/54 cases we reported HHV-6 clinical manifestations: fever (43), skin rash (22), hepatitis (19), diarrhoea (24), encephalitis (10), BM suppression (18), delayed engraftment (11). HHV-6 positivity led to antiviral pharmacological treatment in 37/54 cases, using as first choice therapy foscarnet. Amongst the total fifty-four patients with documented HHV-6 positivity thirty-one solved the clinical event. However the mortality rate was relatively high in this population (overall survival (OS) ±SE at 1 year after HHV-6 reactivation was 38% ± 7%), mainly related to severe infections or GvHD. A better OS is significantly associated with CD3+ cells ≥200/mcl at the time of HHV-6 reactivation (fig 1) (OS at 1 year 63% compared to 11% for patients with CD3 CONCLUSIONS: This retrospective study confirms a correlation of HHV-6 with high morbidity and mortality rates after alloSCT, thus suggesting a regular HHV-6 monitoring in alloSCT recipients. The regular monitoring of HHV-6 DNA, using a real-time PCR assay, may be useful for identifying active HHV-6 infection and for the introduction of a pre-emptive treatment, possibly reducing the incidence of the most severe clinical complications. Despite HHV-6 detection typically occurred early after alloSCT, a better immune reconstitution has the potential to improve clinical outcome. Figure 1: Overall survival after alloSCT in HHV-6 positive patients: green line showed patients with more than 200/mcl CD3+ cells, blue line the ones with less than 200/mcl CD3+ cells at HHV-6 reactivation. P value is provided by Log Rank test. Figure 1:. Overall survival after alloSCT in HHV-6 positive patients: green line showed patients with more than 200/mcl CD3+ cells, blue line the ones with less than 200/mcl CD3+ cells at HHV-6 reactivation. P value is provided by Log Rank test. Disclosures Bonini: MolMed S.p.A.: Consultancy.