Immune reconstitution and cytomegalovirus infection after allogeneic stem cell transplantation: the important impact of in vivo T cell depletion

Prognostic factors in haploidentical transplantation with post-transplant cyclophosphamide for acute myeloid leukemia

BACKGROUND AIMS

Haploidentical hematopoietic stem cell transplantation (haplo-HCT) is an appropriate option when an HLA-matched related or unrelated donor is not available. Haplo-HCT using post-transplant cyclophosphamide (PTCy) is being increasingly performed worldwide due to its effective suppression of GVHD and its safety.

METHODS

We conducted a large nationwide cohort study to retrospectively analyze 366 patients with acute myeloid leukemia undergoing haplo-HCT with PTCy between 2010 and 2019 and to identify prognostic factors.

RESULTS

A multivariate Cox analysis revealed that an older recipient age (≥60 years), a male donor to a male recipient, a cytomegalovirus IgG-negative donor to a cytomegalovirus IgG-positive recipient, a poor cytogenetic risk, a noncomplete remission status at the time of transplantation, and a history of HCT were independently associated with worse overall survival (OS). Based on each hazard ratio, these factors were scored (1-2 points) and stratified by their total score into three groups: favorable (0-1 points), intermediate (2-3 points), and poor (4 points or more) groups, and 2-year OS rates were 79.9%, 49.2%, and 25.1%, respectively (P < 0.001).

CONCLUSIONS

The present study revealed significant prognostic factors in haplo-HCT with PTCy, and a scoring system based on these factors may be used to predict outcomes.

Comparing the Outcomes of Matched and Mismatched Unrelated Allogeneic Hematopoietic Stem Cell Transplantation with Different Anti-Thymocyte Globulin Formulations: A Retrospective, Double-Centre Experience on Behalf of the Polish Adult Leukemia Group

Despite notable advancements in immunotherapy in the past decades, allogeneic hematopoietic stem cell transplantation (allo-HCT) remains a promising, potentially curative treatment modality. Only a limited number of studies have performed a direct comparison of two prevalent rabbit anti-thymocyte globulin (r-ATG) formulations-specifically, Thymoglobuline (ATG-T, formerly Genzyme) and Grafalon (ATG-G, formerly Fresenius). The primary objective of our retrospective analysis was to compare the outcomes of adult patients undergoing matched or mismatched unrelated donor (MUD/MMUD) allo-HCT, with a graft-versus-host disease (GvHD) prophylaxis based on either ATG-T or ATG-G. A total of 87 patients who had undergone allo-HCT between 2012 and 2022 were included. We observed no significant differences between ATG-T and ATG-G concerning the occurrence of acute graft-versus-host disease (aGvHD), regardless of its severity. Conversely, chronic graft-versus-host disease (cGvHD) occurred less frequently in the ATG-T group compared to the ATG-G group (7.5% vs. 38.3%, p = 0.001). The negative impact of ATG-G on cGvHD was confirmed by multivariate analysis (HR 8.12, 95% CI 2.06-32.0, p = 0.003). Patients treated with ATG-T manifested a higher incidence of cytomegalovirus (CMV) reactivations (70% vs. 31.9%, p < 0.001), with a shorter time between transplant and CMV (<61 days, 77.8% vs. 33.3%, p = 0.008) and a higher median CMV copy number (1000 vs. 0, p = 0.004). Notably, despite a higher occurrence of CMV reactivations in the ATG-T cohort, most patients were asymptomatic compared to ATG-G (85.7% vs. 43.8%, p = 0.005). By multivariate analysis, only aGvHD had an influence on CMV reactivations (HR 0.18, 95% CI 0.04-0.75, p = 0.019). Finally, we observed no significant differences in terms of 5-year overall survival (OS) and 3-year relapse-free survival (RFS) while comparing ATG-T and ATG-G (32.0% vs. 40.3%, p = 0.423; 66.7% vs. 60.4%, p = 0.544, respectively).

Updates in hematopoietic cell transplant and cellular therapies that enhance the risk for opportunistic infections

BACKGROUND

Infectious disease physicians may be asked to evaluate and manage a variety of infections in immunocompromised hosts undergoing hematopoietic cell transplant (HCT) and cellular therapies. Over the last decade, several advances in cellular therapy have occurred, with implications for the types of infectious complications that may be seen.

AIMS

The purpose of this review is to update the infectious disease physician on newer advances in HCT and cellular therapy, including haploidentical transplant, expanding indications for transplant in older individuals and children, and chimeric antigen receptor T-cells. We will review how these advances might influence infectious disease complications following HCT. We will also provide a perspective that infectious disease physicians can use to evaluate the degree of immune suppression in an individual patient to help determine the type of infections that may be encountered.

Comparison of Different Rabbit Anti-Thymocyte Globulin Formulations in the Prophylaxis of Graft-Versus-Host Disease: A Systematic Review

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative treatment modality, frequently used for patients suffering from haematological malignancies. In the last two decades, there have been multiple randomised controlled trials (RCTs), review articles, and meta-analyses addressing the efficacy of rabbit anti-thymocyte globulin (r-ATG) as a graft-versus-host disease (GvHD) prophylaxis. Nevertheless, only a few aimed to compare the effectiveness of different r-ATG formulations. Since the last article we retrieved comparing different r-ATGs in GvHD prophylaxis dates back to 2017, we performed a systematic literature review of articles published since 2017 to this day, utilising PubMed, Scopus, Cochrane, and MEDLINE, with the main endpoints being prophylaxis of acute GvHD (aGvHD) and chronic GvHD (cGvHD). We subjected to scrutiny a total of five studies, of which four compared the differences between Thymoglobulin (ATG-T) and Grafalon (ATG-G), and one discussed the impact of ATG-T dose. Overall, cGvHD, aGvHD grades II-IV, TRM, OS, NRM, LFS, relapse, overall infections, and EBV reactivation do not seem to be affected by the type of utilised rATG. However, data on aGvHD grades III-IV, GRFS, moderate-severe cGvHD, and CMV reactivation is conflicting. Through our research, we sought to summarise the most recent findings concerning r-ATGs in allo-HCT, and provide insight into the differences between the targets and origin of various ATG formulations.

Diagnostic stewardship to limit repeat plasma cytomegalovirus viral load testing

BACKGROUND

Frequent serial monitoring of plasma cytomegalovirus (CMV) viral load caused unnecessary budgets for laboratory testing without changes in treatment. We aimed to implement diagnostic stewardship to limit CMV viral load testing at appropriate intervals.

METHODS

A quasi-experimental study was performed. To avoid unnecessary plasma CMV viral load testing, the inpatient electronic pop-up reminder was launched in 2021. In cases with plasma CMV viral load testing was ordered in intervals of less than five days, telephone interview and feedback were performed. Pre-post intervention data was compared in terms of clinical and monetary outcomes. The rate of plasma CMV viral load testing performed in intervals of less than five days was compared between 2021 and 2019 using the Poisson regression model.

RESULTS

After the protocol implementation, there was a significant decrease in the rate of plasma CMV viral load test orders in intervals of less than five days from 17.5% to 8.0% [incidence rate ratio 0.40, p < 0.001]. There was no statistically significant difference in the incidence of CMV DNAemia and CMV disease (p = 0.407 and 0.602, respectively). As a result, the hospital could save the costs of plasma CMV viral load testing per 1,000 patients performed with intervals of less than five days from 2,646,048.11 to 1,360,062.89 Thai Baht.

CONCLUSIONS

The diagnostic stewardship program is safe and helpful in reducing unnecessary plasma CMV viral load testing and costs.

Immunotherapy with CD25/CD71-allodepleted T cells to improve T-cell reconstitution after matched unrelated donor hematopoietic stem cell transplant: a randomized trial

BACKGROUND AIMS

Delayed immune reconstitution is a major challenge after matched unrelated donor (MUD) stem cell transplant (SCT). In this randomized phase 2 multi-center trial, Adoptive Immunotherapy with CD25/71 allodepleted donor T cells to improve immunity after unrelated donor stem cell transplant (NCT01827579), the authors tested whether allodepleted donor T cells (ADTs) can safely be used to improve immune reconstitution after alemtuzumab-based MUD SCT for hematological malignancies.

METHODS

Patients received standard of care or up to three escalating doses of ADTs generated through CD25+/CD71+ immunomagnetic depletion. The primary endpoint of the study was circulating CD3+ T-cell count at 4 months post-SCT. Twenty-one patients were treated, 13 in the ADT arm and eight in the control arm.

RESULTS

The authors observed a trend toward improved CD3+ T-cell count at 4 months in the ADT arm versus the control arm (230/µL versus 145/µL, P = 0.18), and three ADT patients achieved normal CD3+ T-cell count at 4 months (>700/µL). The rates of significant graft-versus-host disease (GVHD) were comparable in both cohorts, with grade ≥2 acute GVHD in seven of 13 and four of eight patients and chronic GVHD in three of 13 and three of eight patients in the ADT and control arms, respectively.

CONCLUSIONS

These data suggest that adoptive transfer of ADTs is safe, but that in the MUD setting the benefit in terms of T-cell reconstitution is limited. This approach may be of more use in the context of more rigorous T-cell depletion.

The Ten Most Common Questions on Cytomegalovirus Infection in Hematopoietic Stem Cell Transplant Patients

With the rising number of patients undergoing hematopoietic stem cell transplantation (HSCT), clinicians are more likely to encounter infectious complications in immunocompromised hosts, particularly cytomegalovirus (CMV) infection. Besides the high mortality of CMV end-organ disease, patients with detectable CMV viremia may have worse outcomes and decreased survival even in the absence of end-organ disease. In view of the implications on morbidity and mortality, clinicians should maintain a high index of suspicion and initiate antiviral drugs promptly when CMV infection is confirmed. High-risk patients should be identified in order to provide optimal management. Additionally, novel antiviral agents with a good safety profile and minor adverse events are now available for prophylaxis in high-risk patients and for treatment of resistant or refractory CMV infection. The following review provides concise, yet comprehensive, guidance on the burden and risk factors of CMV in this population, as well as an update on the latest evidence for the management of CMV infection.

Immunoprofiling reveals cell subsets associated with the trajectory of cytomegalovirus reactivation post stem cell transplantation

Human cytomegalovirus reactivation is a major opportunistic infection after allogeneic haematopoietic stem cell transplantation and has a complex relationship with post-transplant immune reconstitution. Here, we use mass cytometry to define patterns of innate and adaptive immune cell reconstitution at key phases of human cytomegalovirus reactivation in the first 100 days post haematopoietic stem cell transplantation. Human cytomegalovirus reactivation is associated with the development of activated, memory T-cell profiles, with faster effector-memory CD4⁺ T-cell recovery in patients with low-level versus high-level human cytomegalovirus DNAemia. Mucosal-associated invariant T cell levels at the initial detection of human cytomegalovirus DNAemia are significantly lower in patients who subsequently develop high-level versus low-level human cytomegalovirus reactivation. Our data describe distinct immune signatures that emerged with human cytomegalovirus reactivation after haematopoietic stem cell transplantation, and highlight Mucosal-associated invariant T cell levels at the first detection of reactivation as a marker that may be useful to anticipate the magnitude of human cytomegalovirus DNAemia.

Human cytomegalovirus is a major cause of morbidity and mortality in transplant patients and multiple immune cells types are critical during infection and reactivation. Here the authors assess the immune cell compartments of haematopoietic stem cell recipients in the early period post transplantation and identify key features of effector memory CD4⁺ T cells and mucosal associated invariant T cells in this context.

Risk factors and outcomes of cytomegalovirus infection in children post cord blood transplantation with focus on impact of graft-versus-host disease and immunosuppressants

Cytomegalovirus (CMV) infection remains an important cause of morbidity and mortality post cord blood transplantation (CBT). It has been suggested that the graft-versus-host disease (GVHD) and immunosuppressants have an impact on CMV infection. This study evaluated the incidence, outcomes, and risk factors of CMV infection, while focusing on GVHD and the use of immunosuppressants, in 103 children who had received CBT. Among the patients, 92.2% were positive for CMV serology, while CMV antigenemia was observed in 68.9% and CMV disease developed in 26.2%. CMV enterocolitis was the most common, followed by retinitis and pneumonia. Patients with positive CMV serology and grade II to IV GVHD were independently associated with CMV antigenemia. Recurrent CMV antigenemia was observed significantly more frequently in patients with extensive chronic GVHD. Patients with CMV disease showed significantly worse overall survival, relapse-free survival, and non-relapse mortality than those without CMV disease. In conclusion, CMV infection is common post-CBT in countries with a high rate of CMV seropositivity in the general population and is related to worse outcomes. GVHD severity is associated with the development and recurrence of CMV infection. Thus, efforts need to be made to prevent CMV infection in children post-CBT.

Letermovir Prophylaxis and Cytomegalovirus Reactivation in Adult Hematopoietic Cell Transplant Recipients with and without Acute Graft Versus Host Disease

Simple Summary

Cytomegalovirus (CMV) infection and graft versus host disease (GVHD) both contribute to increased morbidity and mortality following allogeneic hematopoietic cell transplantation (allo-HCT). Since the development of GVHD can increase a patient’s risk of developing CMV infection post-allo-HCT, the aim of our retrospective study was to assess the effectiveness of letermovir prophylaxis in preventing CMV infection in these patients at high risk for CMV reactivation. Letermovir is an antiviral approved for the prevention of CMV infection. This study demonstrated that patients with GVHD had significantly fewer CMV infections when they received letermovir prophylaxis compared to patients who did not receive letermovir.

Abstract

Cytomegalovirus (CMV) is the most clinically significant infection after allogeneic hematopoietic-cell transplantation (allo-HCT) and is associated with increased mortality. The risk for CMV reactivation increases with graft versus host disease (GVHD). GVHD contributes to significant morbidity and mortality and is treated with immunosuppressive therapies that can further increase CMV infection risk. Prophylaxis with letermovir, an oral antiviral approved to prevent CMV, has been shown to decrease the incidence of CMV infection post-allo-HCT in patients at high risk of CMV reactivation, but there is a lack of data confirming this benefit in patients with GVHD. In this single-center, retrospective study, we assessed the incidence of clinically significant CMV infection (CS-CMVi) in allo-HCT patients who received letermovir prophylaxis (n = 119) and who developed aGVHD compared to a control group (n = 143) who did not receive letermovir. Among aGVHD patients, letermovir prophylaxis decreased CS-CMVi in patients with aGVHD (HR 0.08 [95% CI 0.03–0.27], p < 0.001), reduced non-relapsed mortality (p = 0.04) and improved overall survival (p = 0.04). This data suggests that letermovir prophylaxis improves outcomes by preventing CS-CMVi in patients with aGVHD.

The impact of different doses of antithymocyte globulin conditioning on immune reconstitution upon hematopoietic stem cell transplantation

INTRODUCTION

Anti-thymocyte globulin (ATG) is used prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for graft-versus-host disease (GVHD) prophylaxis. Two different ATG doses (7.5 or 10 mg/kg) were evaluated in comparison with a group without ATG therapy.

METHODS

We retrospectively analyzed 132 patients who were transplanted with HSCT without ATG (non-ATG), or who received 7.5 mg/kg ATG (ATG-7.5) or 10 mg/kg ATG (ATG-10) prior to transplantation. The immune cells (CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells) were examined in peripheral blood every three months post-HSCT for 12 months.

RESULTS

Compared with non-ATG group, combined ATG-7.5/ATG-10 groups had significantly lower CD3⁺CD4⁺ T cells and higher CD3⁺CD8⁺ T cells at 3, 6, 9, 12 months post-HSCT; thus, displaying a lower CD4/CD8 ratio in the ATG groups compared to non-ATG group. The ratio of CD19⁺ B cells was statistically lower (at 3rd month, p = .014; at 6th month, p = .025) in combined ATG-7.5/ATG-10 groups at 3 and 6 months post-HSCT, but not at 9 and 12 months after HSCT. The ratios of CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells were similar between the ATG-7.5 and ATG-10 groups at all examined time points. The overall survival (OS), progression-free survival (PFS), relapse and acute GVHD (aGVHD) were comparable among recipients without ATG therapy and with ATG-7.5 or/and ATG-10 therapies. Multivariate analysis revealed that immune cells ratios were not independent factors affecting prognosis.

CONCLUSION

The ATG therapy at higher and lower doses led to a delayed reconstitution of T cells and the inversion of CD4/CD8 ratio for at least one year after HSCT.

American Society for Transplantation and Cellular Therapy Series: #3-Prevention of Cytomegalovirus Infection and Disease After Hematopoietic Cell Transplantation

The Practice Guidelines Committee of the American Society for Transplantation and Cellular Therapy partnered with its Transplant Infectious Disease Special Interest Group to update its 2009 compendium-style infectious diseases guidelines for the care of hematopoietic cell transplant (HCT) recipients. A new approach was taken with the goal of better serving clinical providers by publishing each standalone topic in the infectious disease series as a concise format of frequently asked questions (FAQ), tables, and figures. Adult and pediatric infectious disease and HCT content experts developed and answered FAQs. Topics were finalized with harmonized recommendations that were made by assigning an A through E strength of recommendation paired with a level of supporting evidence graded I through III. The third topic in the series focuses on the prevention of cytomegalovirus infection and disease in HCT recipients by reviewing prophylaxis and preemptive therapy approaches; key definitions, relevant risk factors, and diagnostic monitoring considerations are also reviewed.

Posttransplant cyclophosphamide is associated with increased cytomegalovirus infection: a CIBMTR analysis

Prior studies suggest increased cytomegalovirus (CMV) infection after haploidentical donor transplantation with posttransplant cyclophosphamide (HaploCy). The role of allograft source and posttransplant cyclophosphamide (PTCy) in CMV infection is unclear. We analyzed the effect of graft source and PTCy on incidence of CMV infection, and effects of serostatus and CMV infection on transplant outcomes. We examined patients reported to the Center for International Blood and Marrow Transplantation Research between 2012 and 2017 who had received HaploCy (n = 757), matched related (Sib) with PTCy (SibCy, n = 403), or Sib with calcineurin inhibitor-based prophylaxis (SibCNI, n = 1605). Cumulative incidences of CMV infection by day 180 were 42%, 37%, and 23%, respectively (P < .001). CMV disease was statistically comparable. CMV infection risk was highest for CMV-seropositive recipients (R+), but significantly higher in PTCy recipients regardless of donor (HaploCy [n = 545]: hazard ratio [HR], 50.3; SibCy [n = 279]: HR, 47.7; SibCNI [n = 1065]: HR, 24.4; P < .001). D+/R- patients also had increased risk for CMV infection. Among R+ or those developing CMV infection, HaploCy had worse overall survival and nonrelapse mortality. Relapse was unaffected by CMV infection or serostatus. PTCy was associated with lower chronic graft-versus-host disease (GVHD) overall, but CMV infection in PTCy recipients was associated with higher chronic GVHD (P = .006). PTCy, regardless of donor, is associated with higher incidence of CMV infection, augmenting the risk of seropositivity. Additionally, CMV infection may negate the chronic GVHD protection of PTCy. This study supports aggressive prevention strategies in all receiving PTCy.

The time-dependent effects of early-onset Epstein-Barr viremia on adult acute leukemia patients following allo-HSCT with ATG-containing MAC regimen

Epstein-Barr virus (EBV) viremia is a common complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The purpose of this study was to evaluate the impacts of early-onset EBV viremia in acute leukemia (AL) patients who underwent allo-HSCT with anti-thymocyte globulin (ATG)-containing myeloablative conditioning (MAC) regimen. Two hundred and ninety-six patients were included between January 2013 and December 2015. In 126 patients (42.6%) who developed early-onset EBV viremia, with a median time of 48 (range 18~99) days after allo-HSCT. The cumulative incidence of EBV viremia at 30 and 90 days after allo-HSCT were 4.1 and 39.9%, respectively. Prognostic analysis showed that the adjusted overall survival in early-EBV^pos group was significantly lower than early-EBV^neg group within the first 26.7 months after allo-HSCT [hazard ratio (HR), 1.63, P = 0.012], but significantly higher than those afterward (after 26.7 months: HR 0.11, P = 0.035); for the adjusted event-free survival, early-EBV^pos group was significantly inferior in early-EBV^pos group within the first 10.8 months after transplantation (HR: 1.55, P = 0.042), and this adverse effect was not detected any more after 10.8 months (HR: 0.58, P = 0.107). Compared with early-EBV^neg group after adjusting by aGVHD and CMV viremia, HR for death from transplant-related mortality was 2.78-fold higher in patients with early-EBV viremia in piecewise constant Cox analysis (P = 0.006), and this adverse effect was not detected any more after the cut-point time (HR: 0.67, P = 0.361). No differences in terms of relapse and relapse mortality were observed between early-EBV^pos and early-EBV^neg group (P > 0.05). In conclusion, the impacts on transplant outcomes of early-EBV viremia were time-dependent, which may help to optimize management strategies for early-EBV viremia after allo-HSCT, especially in AL patients with ATG-containing MAC regimen.

Cytomegalovirus (CMV) management in allogeneic hematopoietic cell transplantation: Pre-transplant predictors of survival, reactivation, and spontaneous clearance

BACKGROUND

Cytomegalovirus (CMV) reactivation is a frequent complication after allogeneic hematopoietic cell transplant (alloHCT).

METHOD

We analyzed 159 alloHCT recipients with 4409 quantitative CMV viral loads to determine pre-transplant predictors of CMV reactivation, clinically significant CMV infection (cs-CMVi, defined as CMV viral load >1000 IU/mL), CMV disease, kinetics of spontaneous clearance of CMV, and survival using a standardized pre-emptive therapy approach to identify at-risk groups to target prevention strategies.

RESULTS

Cs-CMVi was most common in D-/R+ unrelated donor transplants (URD). Spontaneous CMV clearance occurred in 26% of patients who reached a viral load of 56-137 IU/mL, 6% at 138-250 IU/mL and in one patient >250 IU/mL. Median time between the first CMV reactivation (>56 IU/mL) and a viral load >250 IU/mL was 13 days, whereas the time from the first viral load >250 IU/mL to reach a vial load >1000 IU/mL was 4 days. Cs-CMVi was associated with a significant increase in non-relapse mortality (NRM) on multivariate analysis.

CONCLUSIONS

Overall, this study indicates that D-/R+ URD recipients are at high-risk for cs-CMVi- and CMV-related mortality, and are potential candidates for targeted CMV prophylaxis. Spontaneous clearance of CMV beyond a viral load of 250 IU/mL is uncommon, suggesting that this could be used as an appropriate threshold to initiate pre-emptive therapy.

Rabbit ATG/ATLG in preventing graft-versus-host disease after allogeneic stem cell transplantation: consensus-based recommendations by an international expert panel

This collaborative initiative aimed to provide recommendations on the use of polyclonal antithymocyte globulin (ATG) or anti-T lymphocyte globulin (ATLG) for the prevention of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HSCT). A comprehensive review of articles released up to October, 2018 was performed as a source of scientific evidence. Fourteen clinically relevant key questions to the domains indication, administration, and post-transplant management were developed and recommendations were produced using the Delphi technique involving a Panel of 14 experts. ATG/ATLG was strongly recommended as part of myeloablative conditioning regimen prior to matched or mismatched unrelated bone marrow or peripheral blood allogeneic HSCT in malignant diseases to prevent severe acute and chronic GvHD. ATG/ATLG was also recommended prior to HLA-identical sibling peripheral HSCT with good but lesser bulk of evidence. In reduced intensity or nonmyeloablative conditioning regimens, ATG/ATLG was deemed appropriate to reduce the incidence of acute and chronic GvHD, but a higher risk of relapse should be taken into account. Recommendations regarding dose, application, and premedication were also provided as well as post-transplant infectious prophylaxis and vaccination. Overall, these recommendations can be used for a proper and safe application of polyclonal ATG/ATLG to prevent GvHD after allogeneic HSCT.

Outcome of autoimmune cytopenia after hematopoietic cell transplantation in primary immunodeficiency

BACKGROUND

Post hematopoietic cell transplantation (HCT) autoimmune cytopenia (AIC) is a potentially life-threatening complication, but studies focusing on large cohorts of patients transplanted for primary immunodeficiency are lacking.

OBJECTIVES

This study sought to determine the incidence, risk factors, and outcomes of post-HCT AIC and B-lymphocyte function following rituximab.

METHODS

We retrospectively studied 502 children with primary immunodeficiency who were transplanted at our center between 1987 and 2018.

RESULTS

Thirty-six patients (9%) developed post-HCT AIC, with a median onset of 6.5 months post-HCT. On univariate analysis, pre-HCT AIC, mismatched donor, alemtuzumab, anti-thymocyte antiglobulin, and acute and chronic graft versus host disease were significantly associated with post-HCT AIC. After multivariate analysis, alemtuzumab (subdistribution hazard ratio, 9.0; 95% CI, 1.50-54.0; P = .02) was independently associated with post-HCT AIC. Corticosteroid and high-dose intravenous immunoglobulin achieved remission in 50% (n = 18), additional rituximab led to remission in 25% (n = 9), and the remaining 25% were treated with a combination of various modalities including sirolimus (n = 5), bortezomib (n = 3), mycophenolate mofetil (n = 2), splenectomy (n = 2), and second HCT (n = 3). The mortality of post-HCT AIC reduced from 25% (4 of 16) prior to 2011 to 5% (1 of 20) after 2011. The median follow-up of 5.8 years (range, 0.4 to 29.1 years) showed that 26 of 30 survivors (87%) were in complete remission, and 4 were in remission with ongoing sirolimus and low-dose steroids. Of the 17 who received rituximab, 7 had B-lymphocyte recovery, 5 had persistent low B-lymphocyte count and remained on intravenous immunoglobulin replacement, 2 had second HCT, and 3 died.

CONCLUSIONS

The frequency of post HCT AIC in our cohort was 9%, and the most significant risk factors for its occurrence were the presence of graft versus host disease and the use of alemtuzumab.

The Evolution of T Cell Depleted Haploidentical Transplantation

Work on bone marrow transplantation from haploidentical donor has been proceeding for over 20 years all over the world and new transplant procedures have been developed. To control both graft rejection and graft vs. host disease, some centers have preferred to enhance the intensity of the conditioning regimens and the post-transplant immune suppression in the absence of graft manipulation; others have concentrated on manipulating the graft in the absence of any additional post-transplant immune suppressive agent. Due to the current high engraftment rates, the low incidence of graft-vs.-host disease and regimen related mortality, transplantation from haploidentical donors have been progressively offered even to elderly patients. Overall, survivals compare favorably with reports on transplants from unrelated donors. Further improvements will come with successful implementation of strategies to enhance post-transplant immune reconstitution and to prevent leukemia relapse.

The Graft-Versus-Leukemia Effect in AML

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the most established and commonly used cellular immunotherapy in cancer care. It is the most potent anti-leukemic therapy in patients with acute myeloid leukemia (AML) and is routinely used with curative intent in patients with intermediate and poor risk disease. Donor T cells, and possibly other immune cells, eliminate residual leukemia cells after prior (radio)chemotherapy. This immune-mediated response is known as graft-versus-leukemia (GvL). Donor alloimmune responses can also be directed against healthy tissues, which is known as graft-versus-host disease (GvHD). GvHD and GvL often co-occur and, therefore, a major barrier to exploiting the full immunotherapeutic benefit of donor immune cells against patient leukemia is the immunosuppression required to treat GvHD. However, curative responses to allo-SCT and GvHD do not always occur together, suggesting that these two immune responses could be de-coupled in some patients. To make further progress in successfully promoting GvL without GvHD, we must transform our limited understanding of the cellular and molecular basis of GvL and GvHD. Specifically, in most patients we do not understand the antigenic basis of immune responses in GvL and GvHD. Identification of antigens important for GvL but not GvHD, and vice versa, could impact on donor selection, allow us to track GvL immune responses and begin to specifically harness and strengthen anti-leukemic immune responses against patient AML cells, whilst minimizing the toxicity of GvHD.

Characteristics of graft-versus-host disease occurring after alemtuzumab-containing allogeneic stem cell transplants: incidence, organ involvement, risk factors and survival

T-cell depletion with alemtuzumab represents an effective form of graft-versus-host disease (GVHD) prophylaxis after allogeneic haematopoietic stem cell transplantation (allo-HSCT); however, little is known regarding the impact of in vivo alemtuzumab on either the incidence or clinical characteristics of acute and chronic GVHD. We therefore studied 201 consecutive adult patients who received an alemtuzumab-based, reduced-intensity conditioned (RIC) allograft. With a median follow-up of 24 months, the cumulative incidence of classic acute and late acute (persistent, recurrent and late onset) GVHD grades II-IV (grades III-IV) was 34% (13%) and 20% (8%) respectively; the cumulative incidence of classic chronic GVHD and overlap syndrome were 4% and 7% respectively. A previous diagnosis of classic acute GVHD is a risk factor for chronic GVHD (hazard ratio 10·91, 95% confidence interval 2·35-50·63, P = 0·0023) while late onset acute GVHD is not a risk factor for later development of chronic GVHD. Unrelated donor transplant is a risk factor for the development of classic acute GVHD but not for late onset or chronic GVHD. In conclusion, this study describes a distinctive pattern of GVHD following alemtuzumab-RIC allografts, identifies the risk factors for GVHD development and provides prognostic information of patients with GVHD.

Deleterious Effect of Steroids on Cytomegalovirus Infection Rate after Allogeneic Stem Cell Transplantation Depends on Pretransplant Cytomegalovirus Serostatus of Donors and Recipients

This study examined the impact of prednisone (PDN) on cytomegalovirus (CMV) infection after allogeneic stem cell transplantation (allo-SCT) according to donor and recipient CMV serostatus. Seventy-five patients underwent allo-SCT from June 2010 to July 2012. The risk of CMV infection according to donor and recipient serostatus was defined as follows: high risk (HR; D-/R+), intermediate risk (IR; D+/R+ and D+/R-), and low risk (D-/R-). Forty-five patients (60%) developed CMV infection, and 46 patients (61%) received steroids (PDN ≥ 1 mg/kg/day) to treat acute graft-versus-host disease. CMV infection was more common in those treated with steroids than in those not treated with steroids (70% versus 44%, respectively, P < .05). Overall, 40% of patients had recurrent CMV infection (50% PDN versus 24% no PDN, P < .05). Steroids had no impact on the incidence of CMV infection or its recurrence in HR patients; however, steroids did prolong the need for antiviral treatment. The incidence of CMV infection in IR patients was higher in those receiving PDN (80% PDN versus 41% no PDN, P = .01); recurrence rates were also higher (55% PDN versus 18% no PDN, P = .02). We analyzed CMV-specific immune reconstitution in the first 22 patients of the series and observed that patients on steroids had lower levels of CMV-specific lymphocytes TCD8 (P < .05 on days +60, +100, and +180) and that CMV-specific immune reconstitution (defined as lymphocytes CD8/IFN ≥ 1 cell/µL) was achieved later (after day +100 post-SCT) in the steroid group.

Principles of alemtuzumab immunoablation in hematopoietic cell transplantation for non-malignant diseases in children: A review

Alemtuzumab is a humanized mAb targeted to CD52. Alemtuzumab is highly immunosuppressive with the ability to deplete T and B cells (in addition to other immune cell lines). A growing understanding of the PKs, dosing, and timing of administration of alemtuzumab has allowed for the study of its use as a conditioning agent for allogeneic HCT. The highly immunosuppressive properties of the drug are particularly appealing in the setting of non-malignant HCT, where GVHD provides no clinical benefit and relapse of malignancy is not applicable. In addition, the degree of immune suppression achieved with alemtuzumab has allowed for a reduction in the intensity of myeloablative cytotoxic agents included in some HCT conditioning regimens, allowing for fewer acute and late toxicities. This review paper will provide a comprehensive summary of the mechanism of action, PKs, dosing, and timing of alemtuzumab, a brief description of its use in various allogeneic HCT protocols for non-malignant conditions and a summary of the data regarding its use for GVHD therapy. The goal of this review was to provide an understanding as to how alemtuzumab might be safely incorporated into HCT conditioning regimens for children with non-malignant disease, allowing for expanded access to curative HCT therapy.

The Role of Anti-Thymocyte Globulin or Alemtuzumab-Based Serotherapy in the Prophylaxis and Management of Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplant is an established treatment modality for hematologic and non-hematologic diseases. However, it is associated with acute and long-term sequelae which can translate into mortality. Graft-versus-host disease (GVHD) remains a glaring obstacle, especially with the advent of reduced-intensity conditioning. Serotherapy capitalizes on antibodies which target T cells and other immune cells to mitigate this effect. This article focuses on the utility of two such agents: anti-thymocyte globulin (ATG) and alemtuzumab. ATG has demonstrated benefit in prophylaxis against GVHD, especially in the chronic presentation. However, there is limited impact of ATG on overall survival and it has little utility in the treatment context. There may be an initial improvement, particularly in skin manifestations, but no substantial benefit has been elicited. Alemtuzumab has shown benefit in both prophylaxis and treatment of GVHD, but at the consequence of a more profound immunosuppressive phase, mandating aggressive viral prophylaxis. There remains heterogeneity in the doses and regimens of the agents, with no standardized protocol in place. Furthermore, it seems that once steroid-refractory GVHD has been established, there is little that can be offered to offset the ultimately dismal outcome. Here we present a systematic overview of ATG- or alemtuzumab-based serotherapy in the prophylaxis and management of GVHD.

In-vivo or ex-vivo T cell depletion or both to prevent graft-versus-host disease after hematopoietic stem cell transplantation

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) represents a widely accepted therapeutic strategy for the treatment of hematologic disorders which are otherwise considered incurable. Alloreactive T cells infused with the stem cell inoculum may generate graft-versus-host disease (GVHD) representing one the most relevant obstacles to the successful outcome of patients receiving allogeneic HSCT. Areas covered: In this review, the authors provide an overview of the most recent approaches of T-cell depletion (TCD) including ex-vivo αβ+ TCD and in-vivo TCD with anti-thymocyte globulin (ATG). Expert opinion: Ex vivo depletion of donor T-cells prevents both acute and chronic GVHD without the need for any additional posttransplant immunological prophylaxis either in haploidentical HSCT and HLA matched transplants. Three prospective trials evaluating the efficacy of ATG in matched unrelated donor transplant recipients demonstrated that ATG reduces the incidence of both acute and chronic GVHD without a significant increase of relapse rate, and similar results have been reported in the setting of blood stem cell grafts from matched sibling donors.

Possible Impact of Cytomegalovirus-Specific CD8+ T Cells on Immune Reconstitution and Conversion to Complete Donor Chimerism after Allogeneic Stem Cell Transplantation

Complete donor chimerism is strongly associated with complete remission after allogeneic stem cell transplantation (allo-SCT) in patients with hematologic malignancies. Donor-derived allo-immune responses eliminate the residual host hematopoiesis and thereby mediate the conversion to complete donor chimerism. Recently, cytomegalovirus (CMV) reactivation was described to enhance overall T cell reconstitution, to increase graft-versus-host disease incidence, and to reduce the leukemia relapse risk. However, the link between CMV and allo-immune responses is still unclear. Here, we studied the relationship between CMV-specific immunity, overall T cell reconstitution, and residual host chimerism in 106 CMV-seropositive patients transplanted after reduced-intensity conditioning including antithymocyte globulin. In accordance with previous reports, the recovery of CMV-specific cytotoxic T cells (CMV-CTLs) was more frequent in CMV-seropositive recipients (R) transplanted from CMV-seropositive than from seronegative donors (D). However, once CMV-CTLs were detectable, the reconstitution of CMV-specific CTLs was comparable in CMV R+/D- and R+/D+ patients. CD3⁺ and CD8⁺ T cell reconstitution was significantly faster in patients with CMV-CTLs than in patients without CMV-CTLs both in the CMV R+/D- and R+/D+ setting. Moreover, CMV-CTL numbers correlated with CD3⁺ and CD8⁺ T cell numbers in both settings. Finally, presence of CMV-CTLs was associated with low host chimerism levels 3 months after allo-SCT. In conclusion, our data provide a first indication that CMV-CTLs in CMV-seropositive patients might trigger the reconstitution of T cells and allo-immune responses reflected by the conversion to complete donor chimerism.

Early and Long-Term Impaired T Lymphocyte Immune Reconstitution after Cord Blood Transplantation with Antithymocyte Globulin

Immune reconstitution is crucial to the success of allogeneic hematopoietic stem cell transplantation. Umbilical cord blood transplantation (UCBT) has been associated with delayed immune reconstitution. We characterized the kinetics and investigated the risk variables affecting recovery of the main lymphocyte subsets in 225 consecutive pediatric and adult patients (males, n = 126; median age, 15; range, .3 to 60; interquartile range, 4 to 35) who underwent myeloablative single UCBT between 2005 and 2015 for malignant and nonmalignant disorders. Low CD4⁺ and CD8⁺ T cell counts were observed up to 12 months after UCBT. In contrast, B and natural killer cells recovered rapidly early after transplantation. In a multivariate regression model, factors favoring CD4⁺ T cell recovery ≥ 200 cells/µL were lower dose antithymocyte globulin (ATG) (hazard ratio [HR], 3.93; 95% confidence interval [CI], 2.3 to 5.83; P = .001), negative recipient cytomegalovirus (CMV) serostatus (HR, 3.76; 95% CI, 1.9 to 5.74; P = .001), and younger age (HR, 2.61; 95% CI, 1.01 to 3.47; P = .03). Factors favoring CD8⁺ T cell recovery ≥ 200 cells/µL were lower dose ATG (HR, 3.03; 95% CI, 1.4 to 5.1; P = .03) and negative recipient CMV serostatus (HR, 1.9; 95% CI, 1.63 to 2.15; P = .01). Our results demonstrate the significant negative impact of ATG on lymphocyte recovery. A reduction of the dose or omission of ATG could improve immune reconstitution and perhaps reduce opportunistic infections after UCBT.

Immunity to Infections after Haploidentical Hematopoietic Stem Cell Transplantation

The advantage of using a Human Leukocyte Antigen (HLA)-mismatched related donor is that almost every patient who does not have an HLA-identical donor or who urgently needs hematopoietic stem cell transplantation (HSCT) has at least one family member with whom shares one haplotype (haploidentical) and who is promptly available as a donor. The major challenge of haplo-HSCT is intense bi-directional alloreactivity leading to high incidences of graft rejection and graft-versus-host disease (GVHD). Advances in graft processing and pharmacologic prophylaxis of GVHD have reduced these risks and have made haplo-HSCT a viable alternative for patients lacking a matched donor. Indeed, the haplo-HSCT has spread to centers worldwide even though some centers have preferred an approach based on T cell depletion of G-CSF-mobilized peripheral blood progenitor cells (PBPCs), others have focused on new strategies for GvHD prevention, such as G-CSF priming of bone marrow and robust post-transplant immune suppression or post-transplant cyclophosphamide (PTCY). Today, the graft can be a megadose of T-cell depleted PBPCs or a standard dose of unmanipulated bone marrow and/or PBPCs. Although haplo-HSCT modalities are based mainly on high intensity conditioning regimens, recently introduced reduced intensity regimens (RIC) showed promise in decreasing early transplant-related mortality (TRM), and extending the opportunity of HSCT to an elderly population with more comorbidities. Infections are still mostly responsible for toxicity and non-relapse mortality due to prolonged immunosuppression related, or not, to GVHD. Future challenges lie in determining the safest preparative conditioning regimen, minimizing GvHD and promoting rapid and more robust immune reconstitution.

Infectious diseases in allogeneic haematopoietic stem cell transplantation: prevention and prophylaxis strategy guidelines 2016

Infectious complications after allogeneic haematopoietic stem cell transplantation (allo-HCT) remain a clinical challenge. This is a guideline provided by the AGIHO (Infectious Diseases Working Group) of the DGHO (German Society for Hematology and Medical Oncology). A core group of experts prepared a preliminary guideline, which was discussed, reviewed, and approved by the entire working group. The guideline provides clinical recommendations for the preventive management including prophylactic treatment of viral, bacterial, parasitic, and fungal diseases. The guideline focuses on antimicrobial agents but includes recommendations on the use of vaccinations. This is the updated version of the AGHIO guideline in the field of allogeneic haematopoietic stem cell transplantation utilizing methods according to evidence-based medicine criteria.

Rapid reconstitution of CD4 T cells and NK cells protects against CMV-reactivation after allogeneic stem cell transplantation

BACKGROUND

Epstein-Barr virus and Cytomegalovirus reactivations frequently occur after allogeneic stem cell transplantation (SCT).

METHODS

Here we investigated the role of immune cell reconstitution in the onset and subsequent severity of EBV- and CMV-reactivation. To this end, 116 patients were prospectively sampled for absolute T cell (CD4 and CD8), B-cell (CD19) and NK-cell (CD16 and CD56) numbers weekly post-SCT during the first 3 months and thereafter monthly until 6 months post-SCT. Viral load was monitored in parallel.

RESULTS

In contrast to the general belief, we found that early T-cell reconstitution does not play a role in the onset of viral reactivation. CMV reactivation in the first 7 weeks after SCT however resulted in higher absolute CD8(+) T-cell numbers 6 months post-SCT in patients with high-level reactivation, many of which were CMV-specific. Interestingly, rapid reconstitution of CD4(+) T-cells, as well as NK cells and the presence of donor KIR3DL1, are associated with the absence of CMV-reactivation after SCT, suggestive of a protective role of these cells. In contrast, EBV-reactivations were not affected in any way by the level of immune reconstitution after SCT.

CONCLUSION

In conclusion, these data suggest that CD4(+) T-cells and NK cells, rather than CD8(+) T-cells, are associated with protection against CMV-reactivation.

Matched unrelated donor transplants-State of the art in the 21st century

Hematopoietic stem cell transplantation (HSCT) is the therapy of choice in many hematological malignant and non-malignant diseases by using human leukocyte antigen (HLA)-matched siblings as stem cell source but only one third of the patients will have HLA-matched siblings. Hence, physicians rely on the availability of matched unrelated donors (URD). The possibility of finding a matched URD is now more than 70% due to continuous expansion of URD registries around the world. The use of URD in adult patients is steadily increasing and in the last 8 years has superseded the numbers of matched sibling donor transplants and has become the most commonly used stem cell source. There is also an increasing trend to use peripheral blood (PB) stem cells rather than bone marrow (BM) stem cells. Outcomes following URD transplants depend mainly upon the indication and urgency of transplant, age and comorbidities of recipients, cytomegalovirus (CMV) matching/mismatching between donor and the recipient, and degree of HLA matching. In some studies outcome of unrelated stem cell transplants in terms of treatment-related mortality (TRM), disease-free survival (DFS), and overall survival (OS) is comparable to sibling donors.

Treatment of CMV infection after allogeneic hematopoietic stem cell transplantation

Despite a remarkable reduction in the past decades, cytomegalovirus (CMV) disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients remains a feared complication, still associated with significant morbidity and mortality. Today, first line treatment of CMV infection/reactivation is still based on dated antiviral compounds Ganciclovir (GCV), Foscarnet (FOS) and Cidofovir (CDF) with their burdensome weight of side effects. Maribavir (MBV), Letermovir (LMV) and Brincidofovir (BDF) are three new promising anti-CMV drugs without myelosuppressive properties or renal toxic effects that are under investigation in randomized phase II and III trials. Adoptive T-cell therapy (ATCT) in CMV infection possesses a strong rationale, demonstrated by several proof of concept studies; its feasibility is currently under investigation by clinical trials. ATCT from third-party and naïve donors could meet the needs of HSCT recipients of seronegative donors and cord blood grafts. In selected patients such as recipients of T-cell depleted grafts, ATCT, based on CMV-specific host T-cells reconstitution kinetics, would be of value in the prophylactic and/or preemptive CMV treatment. Vaccine-immunotherapy has the difficult task to reduce the incidence of CMV reactivation/infection in highly immunocompromised HSCT patients. Newer notions on CMV biology may represent the base to flush out the Troll of transplantation.

Naive Donor NK Cell Repertoires Associated with Less Leukemia Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Acute and latent human CMV cause profound changes in the NK cell repertoire, with expansion and differentiation of educated NK cells expressing self-specific inhibitory killer cell Ig-like receptors. In this study, we addressed whether such CMV-induced imprints on the donor NK cell repertoire influenced the outcome of allogeneic stem cell transplantation. Hierarchical clustering of high-resolution immunophenotyping data covering key NK cell parameters, including frequencies of CD56(bright), NKG2A(+), NKG2C(+), and CD57(+) NK cell subsets, as well as the size of the educated NK cell subset, was linked to clinical outcomes. Clusters defining naive (NKG2A(+)CD57(-)NKG2C(-)) NK cell repertoires in the donor were associated with decreased risk for relapse in recipients with acute myeloid leukemia and myelodysplastic syndrome (hazard ratio [HR], 0.09; 95% confidence interval [CI]: 0.03-0.27; p < 0.001). Furthermore, recipients with naive repertoires at 9-12 mo after hematopoietic stem cell transplantation had increased disease-free survival (HR, 7.2; 95% CI: 1.6-33; p = 0.01) and increased overall survival (HR, 9.3; 95% CI: 1.1-77, p = 0.04). Conversely, patients with a relative increase in differentiated NK cells at 9-12 mo displayed a higher rate of late relapses (HR, 8.41; 95% CI: 6.7-11; p = 0.02), reduced disease-free survival (HR, 0.12; 95% CI: 0.12-0.74; p = 0.02), and reduced overall survival (HR, 0.07; 95% CI: 0.01-0.69; p = 0.02). Thus, our data suggest that naive donor NK cell repertoires are associated with protection against leukemia relapse after allogeneic HSCT.

Differential impact of two doses of antithymocyte globulin conditioning on lymphocyte recovery upon haploidentical hematopoietic stem cell transplantation

Background

In vivo depletion of host T cells with antithymocyte globulin (ATG) is a common strategy for preventing graft-versus-host disease in allogeneic hematopoietic stem cell transplantation (HSCT). The total dose of ATG in conditioning regimens appears to be an important factor that influences the outcome in recipients of transplants. However, the optimal ATG dosage has not been established to date. It remains unclear whether, in the setting of haploidentical HSCT (haploHSCT), different doses of ATG might exert differential influences on the recovery of lymphocyte subpopulations.

Methods

This retrospective study analyzed lymphocyte recovery and its correlation to viral infection in two groups of patients that received different doses of ATG before haploHSCT. We performed flowcytometry to determine immunophenotypes of CD19⁺ B cells and CD3⁺, CD4⁺, CD8⁺, CD4⁺CD45RA⁺, CD4⁺CD45RO⁺, CD4⁺CD28⁺, CD8⁺CD28⁺, and CD4⁻CD8⁻ T cells.

Results

We found that, compared to 6 mg/kg, 10 mg/kg ATG significantly hampered the recoveries of CD4⁺, CD4⁺CD45RA⁺, and CD4⁺CD45RO⁺ T cells in the first 2 months following haploHSCT. Similarly, compared to 6 mg/kg, the 10 mg/kg dose of ATG negatively influenced the recoveries of CD4⁻CD8⁻ and CD8⁺CD28⁺ T cells; recovery was delayed for 6 and 12 months after transplantation, respectively. Moreover, we showed that an increase in Epstein-Barr virus (EBV) infections, associated with the higher dose of ATG, was correlated with the delayed recovery of CD4⁻CD8⁻ double negative T cells.

Conclusions

The present study revealed a differential impact of different ATG conditioning doses on the recoveries of T cell subpopulations post-haploHSCT. This study was the first to connect the recovery of CD4⁻CD8⁻ T cells to the risk of EBV infection after HSCT. These findings will facilitate optimization of the ATG conditioning dosage and improve the outcome of patients with leukemia that receive haploHSCT.

Reactivation of Human Herpes Virus-6 After Pediatric Stem Cell Transplantation: Risk Factors, Onset, Clinical Symptoms and Association With Severity of Acute Graft-Versus-Host Disease

BACKGROUND AND METHODS

To study clinical symptoms, timing and consequences of human herpesvirus-6 (HHV-6) reactivation after pediatric allogeneic stem cell transplantation (SCT), HHV-6 was investigated by plasma polymerase chain reaction in a cohort of 106 pediatric SCT recipients.

RESULTS

HHV-6 viremia was detected post-SCT in 48% of the patients with a median time of onset at 20 days after SCT. In week 3 and 4 post-SCT, HHV-6 is the most common infectious agent detected. In up to 30% of the patients with fever of unknown origin, HHV-6 was the only detected infectious agent to explain fever. Patients transplanted with an unrelated donor or receiving serotherapy were at increased risk of HHV-6 reactivation. The onset of HHV-6 reactivation coincided with the appearance of lymphocytes and monocytes in peripheral blood. Treatment with alemtuzumab (MabCampath) delayed both lymphocyte and monocyte engraftment and, concomitantly, onset of HHV-6 reactivation was delayed in those cases. HHV-6 reactivation was not associated with an increased incidence of acute graft-versus-host disease (GvHD). However, progression to grade II-IV GvHD was in 9 of 10 patients associated with HHV-6 reactivation before GvHD (P = 0.006) and HHV-6 was the only infection with such an association.

CONCLUSIONS

HHV-6 frequently reactivates after pediatric SCT around the time of mononuclear cell engraftment and is associated with an increased severity of GvHD. HHV-6 may explain fever of unknown origin in 30% of the patients early after SCT. Assessment of HHV-6 reactivation in patients early after SCT can be instrumental for clinical decision making.

High proportions of regulatory T cells in PBSC grafts predict improved survival after allogeneic haematopoietic SCT

Regulatory T cells (Tregs) modulate immune responses and improve survival in murine transplant models. However, whether the Treg content of allogeneic cell grafts influences the outcome in human haematopoietic stem cell (HSC) transplantation is not well established. In a prospective study of 94 adult allogeneic PBSC transplants (60% unrelated; 85% reduced intensity conditioning), the median Treg (CD3(+)CD4(+)CD25(+)FOXP3(+)CD127(dim/-)) dose transplanted was 4.7 × 10(6)/kg, with Tregs accounting for a median of 2.96% of CD4(+) T cells. Patients transplanted with grafts containing a Treg/CD4(+) T-cell ratio above the median had a 3-year overall survival of 75%, compared with 49% in those receiving grafts with a Treg/CD4(+) T-cell ratio below the median (P=0.02), with a 3-year non-relapse mortality of 13% and 35%, respectively (P=0.02). In multivariate analysis, a high graft Treg/CD4(+) T-cell ratio was an independent predictor of lower non-relapse mortality (hazard ratio (HR), 0.30; P=0.02), improved overall survival (HR, 0.45; P=0.03) and improved sustained neutrophil (HR, 0.52; P=0.002), platelet (HR, 0.51; P<0.001) and lymphocyte (HR, 0.54; P=0.009) recovery. These data support the hypothesis that the proportion of Tregs in allogeneic HSC grafts influences clinical outcome and suggest that Treg therapies could improve allogeneic HSC transplantation.

Transfusion in CMV seronegative T-depleted allogeneic stem cell transplant recipients with CMV-unselected blood components results in zero CMV transmissions in the era of universal leukocyte reduction: a U.K. dual centre experience

OBJECTIVES

To establish rates of cytomegalovirus (CMV) transmission with use of CMV-unselected (CMV-U), leukocyte-reduced blood components transfused to CMV-seronegative patient/CMV-seronegative donor (CMV neg/neg) allogeneic stem cell transplantation (SCT) recipients including those receiving T-depleted grafts.

BACKGROUND

CMV infection remains a major cause of morbidity following SCT. CMV-seronegative SCT recipients are particularly at risk of transfusion transmitted CMV (TT-CMV) and until recently they have received blood components from CMV-seronegative donors with significant resource implications. Although leukocyte reduction of blood components is reported to minimise risk of TT-CMV, its efficacy in high-risk situations, such as in T-depleted transplant recipients, is unknown.

METHODS

We retrospectively analysed the incidence of TT-CMV in CMV neg/neg allogeneic SCT recipients transfused with CMV-U, leukocyte-reduced blood components in two transplantation centres in the UK. Patients were monitored for CMV infection by weekly CMV polymerase chain reaction testing. Leukocyte reduction of blood components was in accordance with current UK standards.

RESULTS

Among 76 patients, including 59 receiving in vivo T-depletion, no episodes of CMV infection were detected. Patients were transfused with 1442 CMV-unselected, leukocyte-reduced components, equating to 1862 donor exposures.

CONCLUSIONS

Our findings confirm the safety of leukocyte reduction as a strategy in preventing TT-CMV in high-risk allogeneic SCT recipients.

The use of ATG abrogates the antileukemic effect of cytomegalovirus reactivation in patients with acute myeloid leukemia receiving grafts from unrelated donors

Several studies provided evidence of a consistent antileukemic effect induced by cytomegalovirus (CMV) replication in acute myeloid leukemia (AML) patients receiving allogeneic hematopoietic stem cell transplantation (HSCT), however the use of antithymocyte globulin (ATG) as graft-versus-host disease prophylaxis, may potentially abrogate the protective effect of CMV infection. To address this issue, we retrospectively analyzed the risk of relapse in a cohort of 101 patients with AML who received grafts from an unrelated donor after a conditioning regimen including ATG. The cumulative incidence of CMV reactivation, evaluated by RT qPCR, was 59% at 12 months, and 93% of CMV reactivations occurred within the first 100 days post HSCT. The 5-year cumulative incidence of relapse in patients with CMV reactivation was 29% compared with 37% for patients without CMV reactivation, and the only factor associated with a reduced 5-year cumulative incidence of relapse was the disease status at HSCT (P < 0.001). In the multivariable model adverse cytogenetics (HR 2.42, 95% CI 1.02-5.72; P = 0.044) and acute GVHD (HR 3.36, 95% CI 1.32-8.54; P =  0.011) were independent risk factors for reducing overall survival (OS), while the presence of chronic GVHD was associated with a better OS (HR 0.37, 95% CI 0.15-0.89; P = 0.027). CMV replication was not an independent risk factor for OS (HR 1.06, 95% CI 0.07-15.75; P = 0.965). In Conclusion, the results of present study suggest that relapse prevention in patients with AML receiving T-cell depleted HSCT using ATG do not benefit from CMV reactivation.

Hyperexpansion of Functional Viral-Specific CD8+ T Cells in Lymphopenia-Associated MCMV Pneumonitis

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in immunocompromised hosts, many of whom undergo significant periods of lymphopenia. However, the impact of lymphopenia and subsequent immune reconstitution on T cell responses and pulmonary pathology are poorly understood. Using a model of primary murine CMV infection in mice treated with cyclophosphamide (CY), the relationship of CD8+ T cell reconstitution to pneumonitis pathology was studied. Female BALB/c mice were infected with murine CMV (MCMV) with/without CY on day 1 post-infection. Lung pathology and viral specific T cell responses were assessed on days 7-28. T cell lymphocyte subsets, effector responses, and MCMV specificity were assessed at baseline and after in vitro stimulation of cells with immediate-early peptide pp89. CY treatment of MCMV-infected mice resulted in interstitial pneumonitis not seen with MCMV alone. Compared to MCMV alone, on day 14, MCMV/CY mice had greater number of CD8+ T cells, a fourfold increase in absolute number of pp89 tetramer-specific CD8+ cells, and an eightfold increase in MCMV specific T cell effector responses (IFN-γ; p<0.001). This expansion was preceded by transient lymphopenia, increased viral titers, and, most strikingly, a 10-fold increased proliferative capacity in MCMV/CY mice. In the setting of CY-associated lymphopenia, concurrent MCMV infection alters immune reconstitution toward a hyperexpanded MCMV-specific CD8+ effector T cell pool that correlates with significant lung immunopathology.

Impact of ABO blood group mismatch in alemtuzumab-based reduced-intensity conditioned haematopoietic SCT

The impact of ABO incompatibility on clinical outcomes following haematopoietic SCT (HSCT) remains controversial. This retrospective study assessed the effect of ABO mismatch on transplant outcomes and transfusion requirements in 594 patients undergoing reduced-intensity conditioned (RIC) HSCT with alemtuzumab in three UK transplant centres. We found no significant effects of minor, major or bidirectional ABO mismatch on overall survival, relapse-free survival, nonrelapse mortality or relapse incidence. Although the rate of acute GVHD was unaffected by ABO mismatch, the incidence of extensive chronic GVHD was higher in patients with minor and major mismatch compared with those who were ABO matched (hazard ratio (HR) 1.74, P=0.032 for minor, HR 1.69 P=0.0036 for major mismatch). Red cell and platelet transfusion requirements in the first 100 days post transplant did not differ by ABO mismatch. In this large UK series, ABO mismatch in RIC HSCT has no clinically significant effect on survival outcomes but appears to modify susceptibility to extensive chronic GVHD.

Impact of serotherapy on immune reconstitution and survival outcomes after stem cell transplantations in children: thymoglobulin versus alemtuzumab

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is strongly affected by the kinetics of reconstitution of the immune system. This study compared the effects of antithymocyte globulin (ATG) and alemtuzumab on various outcome parameters after HSCT. The study cohort consisted of 148 children, with a median age of 9.6 years (range, .4 to 19.0), who underwent HSCT for malignant and benign hematological disorders in a single HSCT unit. Conditioning included ATG (n = 110) or alemtuzumab (n = 38). Cox proportional hazard regression analysis showed that alemtuzumab significantly delayed the recovery of CD3(+) T cells and CD4(+)as well as CD8(+) T cell subsets (P ≤ .001) and natural killer (NK) cells (P = .008) compared with ATG. In both ATG- and alemtuzumab-treated patients, shorter drug exposure lead to significantly faster recovery of T cells. Alemtuzumab was associated with lower donor chimerism 3 and 6 months after transplantation and a higher risk of disease relapse (P = .001). The overall survival and event-free survival risks were significantly lower for alemtuzumab-treated patients (P = .020 and P < .001, respectively). Patients who received alemtuzumab showed a trend to lower risk of acute graft-versus-host disease, more human adenovirus, and less Epstein-Barr virus reactivations compared with patients who received ATG. These data indicate that children treated with alemtuzumab as part of the conditioning regimen have a slower T cell and NK cell reconstitution compared with those treated with ATG, which compromises the overall and event-free survival. Prolonged length of lympholytic drug exposure delayed the T cell recovery in both ATG- and alemtuzumab-treated patients. Therefore, we recommend detailed pharmacokinetic/pharmacodynamic (PK/PD) analyses in a larger cohort of patients to develop an algorithm aiming at optimization of the serotherapy containing conditioning regimen.

Improving cytomegalovirus-specific T cell reconstitution after haploidentical stem cell transplantation

Cytomegalovirus (CMV) infection and delayed immune reconstitution (IR) remain serious obstacles for successful haploidentical stem cell transplantation (haplo-SCT). CMV-specific IR varied according to whether patients received manipulated/unmanipulated grafts or myeloablative/reduced intensity conditioning. CMV infection commonly occurs following impaired IR of T cell and its subsets. Here, we discuss the factors that influence IR based on currently available evidence. Adoptive transfer of donor T cells to improve CMV-specific IR is discussed. One should choose grafts from CMV-positive donors for transplant into CMV-positive recipients (D+/R+) because this will result in better IR than would grafts from CMV-negative donors (D−/R+). Stem cell source and donor age are other important factors. Posttransplant complications, including graft-versus-host disease and CMV infection, as well as their associated treatments, should also be considered. The effects of varying degrees of HLA disparity and conditioning regimens are more controversial. As many of these factors and strategies are considered in the setting of haplo-SCT, it is anticipated that haplo-SCT will continue to advance, further expanding our understanding of IR and CMV infection.

The impact of T-cell depletion techniques on the outcome after haploidentical hematopoietic SCT

Several T-cell depletion (TCD) techniques are used for haploidentical hematopoietic SCT (HSCT), but direct comparisons are rare. We therefore studied the effect of in vitro TCD with graft engineering (CD34 selection or CD3/CD19 depletion, 74%) or in vivo TCD using alemtuzumab (26%) on outcome, immune reconstitution and infections after haploidentical HSCT. We performed a retrospective multicenter analysis of 72 haploidentical HSCT in Switzerland. Sixty-seven patients (93%) had neutrophil engraftment. The 1-year OS, TRM and relapse incidence were 48 (36-60)%, 20 (11-33)% and 42 (31-57)%, respectively, without differences among the TCD groups. In vivo TCD caused more profound lymphocyte suppression early after HSCT, whereas immune recovery beyond the second month was comparable between the two groups. Despite anti-infective prophylaxis, most patients experienced post-transplant infectious complications (94%). Patients with in vivo TCD had a higher incidence of CMV reactivations (54% vs 28%, P=0.015), but this did not result in a higher TRM. In conclusion, TCD by graft engineering or alemtuzumab are equally effective for haploidentical HSCT.

CMV serostatus still has an important prognostic impact in de novo acute leukemia patients after allogeneic stem cell transplantation: a report from the Acute Leukemia Working Party of EBMT

We analyzed the prognostic impact of donor and recipient cytomegalovirus (CMV) serostatus in 16,628 de novo acute leukemia patients after allogeneic stem cell transplantation (allo-SCT). Compared with CMV-seronegative recipients who underwent allograft from a CMV-seronegative donor, cases of CMV seropositivity of the donor and/or the recipient showed a significantly decreased 2-year leukemia-free survival (44% vs 49%, P < .001) and overall survival (50% vs 56%, P < .001), and increased nonrelapse mortality (23% vs 20%, P < .001). Both groups showed a comparable relapse incidence and 2-year probability of graft-versus-host disease. The negative prognostic effects of CMV seropositivity of the donor and/or the recipient (vs CMV seronegativity of both) were significantly stronger for acute lymphoblastic leukemia (ALL) than for acute myeloid leukemia (AML), resulting in a markedly reduced 2-year overall survival (46% vs 55% for ALL compared with 52% vs 56% for AML). The important prognostic impact of donor/recipient CMV serostatus remained in a multivariate Cox regression analysis including the other prognostic variables. We conclude that donor and/or recipient CMV seropositivity is still associated with an adverse prognosis in de novo acute leukemia patients after allo-SCT despite the implementation of sophisticated strategies for prophylaxis, monitoring, and (preemptive) treatment of CMV.