Donor cytomegalovirus seropositivity and the risk of leukemic relapse after reduced-intensity transplants

Cytomegalovirus: an unlikely ally in the fight against blood cancers?

Cytomegalovirus (CMV) infection is a potentially fatal complication in patients receiving haematopoietic stem cell transplantation (HSCT), but recent evidence indicates that CMV has strong anti-leukaemia effects due in part to shifts in the composition of natural killer (NK) cell subsets. NK cells are the primary mediators of the anti-leukaemia effect of allogeneic HSCT, and infusion of allogeneic NK cells has shown promise as a means of inducing remission and preventing relapse of several different haematological malignancies. The effectiveness of these treatments is limited, however, when tumours express human leucocyte antigen (HLA)-E, a ligand for the inhibitory receptor NKG2A, which is expressed by the vast majority of post-transplant reconstituted and ex-vivo expanded NK cells. It is possible to enhance NK cell cytotoxicity against HLA-Epos malignancies by increasing the proportion of NK cells expressing NKG2C (the activating receptor for HLA-E) and lacking the corresponding inhibitory receptor NKG2A. The proportion of NKG2Cpos /NKG2Aneg NK cells is typically low in healthy adults, but it can be increased by CMV infection or ex-vivo expansion of NK cells using HLA-E-transfected feeder cells and interleukin (IL)-15. In this review, we will discuss the role of CMV-driven NKG2Cpos /NKG2Aneg NK cell expansion on anti-tumour cytotoxicity and disease progression in the context of haematological malignancies, and explore the possibility of harnessing NKG2Cpos /NKG2Aneg NK cells for cancer immunotherapy.

Impact of cytomegalovirus reactivation on relapse and survival in patients with acute leukemia who received allogeneic hematopoietic stem cell transplantation in first remission

Cytomegalovirus (CMV)-reactivation is associated with graft-vs-leukemia (GVL) effect by stimulating natural-killer or T-cells, which showed leukemia relapse prevention after hematopoietic stem cell transplantation (HSCT). We enrolled patients with acute myeloid leukemia (n = 197) and acute lymphoid leukemia (n = 192) who underwent allogeneic-HSCT in first remission. We measured RQ-PCR weekly to detect CMV-reactivation and preemptively used ganciclovir (GCV) when the titer increased twice consecutively, but GCV was sometimes delayed in patients without significant graft-vs-host disease (GVHD) by reducing immunosuppressive agents. In the entire group, CMV-reactivation showed poor overall survival (OS). To evaluate subsequent effects of CMV-reactivation, we excluded early relapse and deaths within 100 days, during which most of the CMV-reactivation occurred. Untreated CMV-reactivated group (n = 173) showed superior OS (83.8% vs. 61.7% vs. 74.0%, p < 0.001) with lower relapse rate (10.1% vs 22.1% vs. 25.5%, p = 0.004) compared to GCV-treated CMV-reactivated group (n = 122) and CMV-undetected group (n = 42). After excluding chronic GVHD, untreated CMV-reactivated group still showed lower relapse rate (9.4% vs. 24.1% vs. 30.2%, p = 0.006). Multivariate analysis showed adverse-risk karyotype and patients in other than untreated CMV-reactivated group were independent factors for relapse prediction. Our data showed possible GVL effect of CMV-reactivation and minimizing antiviral therapy may benefit for relapse prevention in acute leukemia.

Differential requirements for myeloid leukemia IFN-γ conditioning determine graft-versus-leukemia resistance and sensitivity

The graft-versus-leukemia (GVL) effect in allogeneic hematopoietic stem cell transplantation (alloSCT) is potent against chronic phase chronic myelogenous leukemia (CP-CML), but blast crisis CML (BC-CML) and acute myeloid leukemias (AML) are GVL resistant. To understand GVL resistance, we studied GVL against mouse models of CP-CML, BC-CML, and AML generated by the transduction of mouse BM with fusion cDNAs derived from human leukemias. Prior work has shown that CD4+ T cell-mediated GVL against CP-CML and BC-CML required intact leukemia MHCII; however, stem cells from both leukemias were MHCII negative. Here, we show that CP-CML, BC-CML, and AML stem cells upregulate MHCII in alloSCT recipients. Using gene-deficient leukemias, we determined that BC-CML and AML MHC upregulation required IFN-γ stimulation, whereas CP-CML MHC upregulation was independent of both the IFN-γ receptor (IFN-γR) and the IFN-α/β receptor IFNAR1. Importantly, IFN-γR-deficient BC-CML and AML were completely resistant to CD4- and CD8-mediated GVL, whereas IFN-γR/IFNAR1 double-deficient CP-CML was fully GVL sensitive. Mouse AML and BC-CML stem cells were MHCI+ without IFN-γ stimulation, suggesting that IFN-γ sensitizes these leukemias to T cell killing by mechanisms other than MHC upregulation. Our studies identify the requirement of IFN-γ stimulation as a mechanism for BC-CML and AML GVL resistance, whereas independence from IFN-γ renders CP-CML more GVL sensitive, even with a lower-level alloimmune response.

Low incidence of severe cGvHD and late NRM in a phase II trial of thymoglobulin, tacrolimus and sirolimus for GvHD prevention

Chronic GvHD (cGvHD) is the leading cause of late non-relapse mortality (NRM) and morbidity after allogeneic hematopoietic stem cell transplant (AHSCT). We analyzed the late effects of a phase II trial testing the efficacy of intermediate dose rabbit anti-thymocyte globulin (Thymoglobulin Thymo) in combination with tacrolimus and sirolimus (TTS) in 47 patients (pts) for the prevention of acute and chronic GvHD after unrelated AHSCT. The median follow-up was 45.2 months. The cumulative incidence of NIH severe cGvHD at 48 months was 6.4% with no new occurrences past 6 months for the entire follow-up period. The overall cumulative incidence of cGvHD was 44.7%. Out of 20 pts who are alive and disease-free at the last follow-up, only 4 pts continue to need systemic immune suppression. We observed low late NRM with only 3 transplant-related deaths after 6 months post transplant. At 4 years of follow-up, the overall cumulative incidence of NRM and disease relapse was 27.7% and 30.0%, respectively. PFS and overall survival (OS) at 4 years were 42 and 47%. At long term follow-up, TTS was associated with low incidence of severe cGvHD and late NRM.

Latent cytomegalovirus infection enhances anti-tumour cytotoxicity through accumulation of NKG2C+ NK cells in healthy humans

Cytomegalovirus (CMV) infection markedly expands NKG2C+/NKG2A- NK cells, which are potent killers of infected cells expressing human leucocyte antigen (HLA)-E. As HLA-E is also over-expressed in several haematological malignancies and CMV has been linked to a reduced risk of leukaemic relapse, we determined the impact of latent CMV infection on NK cell cytotoxicity against four tumour target cell lines with varying levels of HLA-E expression. NK cell cytotoxicity against K562 (leukaemia origin) and U266 (multiple myeloma origin) target cells was strikingly greater in healthy CMV-seropositive donors than seronegative donors and was associated strongly with target cell HLA-E and NK cell NKG2C expression. NK cell cytotoxicity against HLA-E transfected lymphoma target cells (221.AEH) was ∼threefold higher with CMV, while NK cell cytotoxicity against non-transfected 721.221 cells was identical between the CMV groups. NK cell degranulation (CD107a(+) ) and interferon (IFN)-γ production to 221.AEH cells was localized almost exclusively to the NKG2C subset, and antibody blocking of NKG2C completely eliminated the effect of CMV on NK cell cytotoxicity against 221.AEH cells. Moreover, 221.AEH feeder cells and interleukin (IL)-15 were found to expand NKG2C(+) /NKG2A(-) NK cells preferentially from CMV-seronegative donors and increase NK cell cytotoxicity against HLA-E(+) tumour cell lines. We conclude that latent CMV infection enhances NK cell cytotoxicity through accumulation of NKG2C(+) NK cells, which may be beneficial in preventing the initiation and progression of haematological malignancies characterized by high HLA-E expression.

Human Cytomegalovirus Infection Enhances NK Cell Activity In Vitro

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Background

Occurring frequently after solid organ and hematopoietic stem cell transplantation, cytomegalovirus (CMV) replication remains a relevant cause of mortality and morbidity in affected patients. Despite these adverse effects, an increased alloreactivity of natural killer (NK) cells after CMV infection has been assumed, but the underlying physiopathological mechanisms have remained elusive.

Methods

We used serial analyses of NK cells before and after CMV infection in kidney transplant recipients as an in vivo model for CMV primary infection to explore the imprint of CMV infection using every patient as their own control: We analyzed NK cell phenotype and function in 47 CMV seronegative recipients of CMV seropositive kidney grafts, who developed CMV primary infection posttransplant. Seronegative recipients of seronegative kidney grafts served as controls.

Results

We observed a significant increase of NKG2C expressing NK cells after CMV infection (mean increase, 17.5%; 95% confidence interval [95% CI], 10.2-24.9, P < 0.001), whereas cluster of differentiation (CD)57 expressing cells decreased (mean decrease, 14.1%; 95% CI, 8.0-20.2; P < 0.001). Analysis of killer immunoglobulin-like receptor (KIR) expression showed an increase of cells expressing KIR2DL1 as their only inhibitory KIR in patients carrying the cognate ligand HLA-C2 (mean increase, 10.0%; 95% CI, 1.7-18.3; P = 0.018). In C2-negative individuals, KIR2DL1 expression decreased (mean decrease, 3.9%; 95% CI, 1.6-6.2; P = 0.001). As for activating KIR, there was no conclusive change pattern.

Most importantly, we observed a significantly higher NK cell degranulation and IFNγ production in response to different target cells (target K562, CD107a: mean increase, 9.9%; 95% CI, 4.8-15.0; P < 0.001; IFNγ: mean increase, 6.6%; 95% CI, 1.6-11.1; P < 0.001; target MRC-5, CD107a: mean increase, 6.9%; 95% CI, 0.7-13.1; P = 0.03; IFNγ: mean increase, 4.8%; 95% CI, 1.7-7.8; P = 0.002).

Conclusions

We report evidence for an increased function of NK cells induced by CMV infection. This increased in vitro functionality was seen in NKG2C-positive and NKG2C-negative subsets, arguing for an NKG2C independent mechanism of action.

Cytomegalovirus pre-emptive therapy after hematopoietic stem cell transplantation in the era of real-time quantitative PCR: comparison with recipients of solid organ transplants

BACKGROUND

Cytomegalovirus (CMV) continues to be an important complication of hematopoietic stem cell transplantation and solid organ transplantation.

METHODS

In this study, 314 patients who underwent hematopoietic stem cell transplantation between January 2003 and October 2011 were tested serially for CMV DNA by real-time quantitative polymerase chain reaction (qPCR) for 90 days post transplantation. Patients with CMV viremia >3000 genomes/mL (equivalent to 2520 IU/mL) received pre-emptive therapy and were compared with previously published data from solid organ transplant (SOT) patients monitored and treated in exactly the same way.

RESULTS

After stem cell transplant (SCT), 48% of patients developed at least 1 episode of viremia. The median duration of a viremic episode was 25 days and the peak viral load (VL) was 4784 genomes/mL whole blood (equivalent to 4019 IU/mL). The data demonstrated that recipients with positive CMV serostatus were at increased risk of developing viremia, with 0% of donor-negative/recipient-negative (D-R-), 3.7% of D+R-, 79.5% of D-R+, and 74.2% of D+R+ groups developing viremia over follow-up (adjusted hazard ratio for D+R- vs. D+R+ group 0.03; 95% confidence interval 0.004, 0.18; P = 0.0013). In contrast with SOT patients, where 58/74 (78%) D+R- patients had viremia, a low risk of CMV infection was seen after stem cell transplantation (1/27; 3.7%).

CONCLUSION

As both groups of patients, the previously published SOT patients and the present hematopoietic SCT patients, were monitored using the same protocol and qPCR assay with pre-emptive therapy administered at the same VL cutoffs, the distinct differences seen cannot be explained by differences in testing or management and thus emphasize distinct aspects of the natural history of CMV infection post transplant in these 2 patient groups.

Therapeutic strategies for cytomegalovirus in allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) remains a major cause of morbidity and mortality in allogeneic hematopoietic cell transplantation. Advances in surveillance of cytomegalovirus reactivation using sensitive techniques and a preemptive strategy to treat virus reactivation has reduced incidence of cytomegalovirus end organ disease. However, severe immunosuppression associated with extensive T-cell depletion resulting from graft-versus-host disease prevention for cases of mismatched or others such as haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) and graft-versus-host disease therapy itself create clinical challenges in managing cytomegalovirus infection. Novel anticytomegalovirus therapies including newer pharmacologic interventions, vaccines, and adoptive cellular therapies to restore anticytomegalovirus immunity appear promising and are expected to continue to shape our treatment armamentarium. Eradication of CMV disease altogether, rather than simply suppressing viremia, should be the ultimate desirable goal.

Single-agent GVHD prophylaxis with posttransplantation cyclophosphamide after myeloablative, HLA-matched BMT for AML, ALL, and MDS

High-dose, posttransplantation cyclophosphamide (PTCy) reduces severe graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (alloBMT), but the impact of PTCy on long-term, disease-specific outcomes is unclear. We conducted a retrospective study of 209 consecutive adult patients transplanted for acute myeloid leukemia (AML, n = 138), myelodysplastic syndrome (n = 28), or acute lymphoblastic leukemia (ALL, n = 43) using PTCy as sole GVHD prophylaxis after myeloablative conditioning and HLA-matched-related or -unrelated T-cell-replete allografting. At alloBMT, 30% of patients were not in morphologic complete remission. The cumulative incidences of grades II to IV and III to IV acute GVHD at 100 days and chronic GVHD at 2 years were 45%, 11%, and 13%, respectively. Forty-three percent of patients did not require immunosuppression for any reason beyond PTCy. At 3 years, relapse cumulative incidence was 36%, disease-free survival was 46%, survival free of disease and chronic GVHD was 39%, and overall survival was 58%. Lack of remission at alloBMT, adverse cytogenetics, and low allograft nucleated cell dose were associated with inferior survival for AML patients. Minimal residual disease but not t(9;22) was associated with inferior outcomes for ALL patients. The ability to limit posttransplantation immunosuppression makes PTCy a promising transplantation platform for the integration of postgrafting strategies to prevent relapse.

Vaccine therapy for cytomegalovirus in the setting of allogeneic hematopoietic cell transplantation

Passive immunization against CMV is desirable to minimize or perhaps eliminate complications related to CMV disease. In allogeneic hematopoietic cell transplantation (allo-HCT), the major challenge facing a successful anti-CMV vaccine is inducing immunity in an immunocompromised host. To date, only one CMV vaccine, ASP0113, has been evaluated in a randomized, placebo-controlled Phase II study. ASP0113 is a bivalent product containing two plasmids that encode CMV glycoprotein B and tegument phosphoprotein 65, respectively. Although there was no significant difference in rate of initiation of anti-CMV therapy, rates of CMV viremia were lower in the ASP0113 group when measured by a central laboratory. Also, time-to-first episode of viremia was longer in subjects receiving ASP0113. These findings paved the way for an ongoing placebo-controlled Phase III study aiming at enrolling 500 subjects. Results of this Phase III trial, especially if it meets clinically meaningful endpoints, will ultimately determine the role of anti-CMV vaccine strategies in allo-HCT.

CMV reactivation after allogeneic HCT and relapse risk: evidence for early protection in acute myeloid leukemia

The association between cytomegalovirus (CMV) reactivation and relapse was evaluated in a large cohort of patients with acute myeloid leukemia (AML) (n = 761), acute lymphoblastic leukemia (ALL) (n = 322), chronic myeloid leukemia (CML) (n = 646), lymphoma (n = 254), and myelodysplastic syndrome (MDS) (n = 371) who underwent allogeneic hematopoietic cell transplantation (HCT) between 1995 and 2005. In multivariable models, CMV pp65 antigenemia was associated with a decreased risk of relapse by day 100 among patients with AML (hazard ratio [HR] = 0.56; 95% confidence interval [CI], 0.3-0.9) but not in patients with ALL, lymphoma, CML, or MDS. The effect appeared to be independent of CMV viral load, acute graft-versus-host disease, or ganciclovir-associated neutropenia. At 1 year after HCT, early CMV reactivation was associated with reduced risk of relapse in all patients, but this did not reach significance for any disease subgroup. Furthermore, CMV reactivation was associated with increased nonrelapse mortality (HR = 1.31; 95% CI, 1.1-1.6) and no difference in overall mortality (HR = 1.05; 95% CI, 0.9-1.3). This report demonstrates a modest reduction in early relapse risk after HCT associated with CMV reactivation in a large cohort of patients without a benefit in overall survival.

Early human cytomegalovirus replication after transplantation is associated with a decreased relapse risk: evidence for a putative virus-versus-leukemia effect in acute myeloid leukemia patients

The impact of early human cytomegalovirus (HCMV) replication on leukemic recurrence was evaluated in 266 consecutive adult (median age, 47 years; range, 18-73 years) acute myeloid leukemia patients, who underwent allogeneic stem cell transplantation (alloSCT) from 10 of 10 high-resolution human leukocyte Ag-identical unrelated (n = 148) or sibling (n = 118) donors. A total of 63% of patients (n = 167) were at risk for HCMV reactivation by patient and donor pretransplantation HCMV serostatus. In 77 patients, first HCMV replication as detected by pp65-antigenemia assay developed at a median of 46 days (range, 25-108 days) after alloSCT. Taking all relevant competing risk factors into account, the cumulative incidence of hematologic relapse at 10 years after alloSCT was 42% (95% confidence interval [CI], 35%-51%) in patients without opposed to 9% (95% CI, 4%-19%) in patients with early pp65-antigenemia (P < .0001). A substantial and independent reduction of the relapse risk associated with early HCMV replication was confirmed by multivariate analysis using time-dependent covariate functions for grades II to IV acute and chronic graft-versus-host disease, and pp65-antigenemia (hazard ratio = 0.2; 95% CI, 0.1-0.4, P < .0001). This is the first report that demonstrates an independent and substantial reduction of the leukemic relapse risk after early replicative HCMV infection in a homogeneous population of adult acute myeloid leukemia patients.

Cytomegalovirus in hematopoietic stem cell transplant recipients

This article examines the clinical manifestations of and risk factors for cytomegalovirus (CMV). Prevention of CMV infection and disease are also explored. Antiviral resistance and management of CMV are examined.

Children with acute leukemia: a comparison of outcomes from allogeneic blood stem cell and bone marrow transplantation

BACKGROUND

The relative merits of peripheral blood stem-cell transplantation (PBSCT) versus bone marrow transplantation (BMT) for children with standard and high-risk hematologic malignancies remain unclear. In a retrospective study, we compared allogeneic PBSCT (n = 30) with BMT (n = 110) in children with acute leukemia between January 2001 and September 2006.

PROCEDURE

Median age for PBSCT was 9 years versus 8 years for BMT. Descriptive statistics were used to summarize the demographic and medical variables. The unadjusted probabilities of disease-free survival were estimated using the Kaplan-Meier method. The association of graft-source and time to each of the study endpoints was estimated by Cox's regression model and the occurrence of graft-versus-host disease (GvHD) was included as a time-dependent covariate.

RESULTS

Time to neutrophil engraftment and platelet independence was faster after PBSCT than BMT (neutrophils 15.0 days vs. 17.0 days, P < 0.001; platelets, 21.0 days vs. 27.0 days, P = 0.034). The cumulative incidence of grades II-IV acute GvHD at 100 days was 10.4% (SE 5.6%) after PBSCT and 15.1% (SE 3.5%) after BMT (P = NS). The cumulative incidence of chronic GvHD was 13.8% (SE 6.3%) after PBSCT and 11.3% (SE 3.1%) after BMT (P = NS). One-year disease-free survival was 37.9% (SE 9.0%) for PBSCT recipients versus 65.1% (SE 4.6%) after BMT (P = 0.005) but this difference was not sustained in multivariate analysis. Thus, only disease risk and pre-transplant CMV seropositivity were significant predictors of disease-free survival.

CONCLUSIONS

We conclude that PBSCT for children produces faster engraftment without increased risk of acute or chronic GvHD.

Cytomegalovirus in hematopoietic stem cell transplant recipients

This article examines the clinical manifestations of and risk factors for cytomegalovirus (CMV). Prevention of CMV infection and disease are also explored. Antiviral resistance and management of CMV are examined.

Impact of cytomegalovirus (CMV) reactivation after umbilical cord blood transplantation

This study investigated the impact of pretransplant cytomegalovirus (CMV) serostatus and posttransplant CMV reactivation and disease on umbilical cord blood transplant (UCBT) outcomes. Between 1994 and 2007, 332 patients with hematologic malignancies underwent UCBT and 54% were CMV seropositive. Pretransplant recipient CMV serostatus had no impact on acute or chronic graft-versus-host disease (aGVHD, cGVHD), relapse, disease-free survival (DFS), or overall survival (OS). There was a trend toward greater day 100 treatment-related mortality (TRM) in CMV-seropositive recipients (P=.07). CMV reactivation occurred in 51% (92/180) of patients with no difference in myeloablative (MA) versus reduced-intensity conditioning (RIC) recipients (P=.33). Similarly, reactivation was not influenced by the number of UCB units transplanted, the degree of HLA disparity, the CD34(+) or CD3(+) cell dose, or donor killer cell immunoglobulin-like receptor (KIR) gene haplotype. Rapid lymphocyte recovery was associated with CMV reactivation (P=.02). CMV reactivation was not associated with aGVHD (P=.97) or cGVHD (P=.65), nor did it impact TRM (P=.88), relapse (P=.62), or survival (P=.78). CMV disease occurred in 13.8% of the CMV-seropositive patients, resulting in higher TRM (P=.01) and lower OS (P=.02). Thus, although recipient CMV serostatus and CMV reactivation have little demonstrable impact on UCB transplant outcomes, the development of CMV disease remains a risk, associated with inferior outcomes.

Donor and recipient CMV serostatus and outcome of pediatric allogeneic HSCT for acute leukemia in the era of CMV-preemptive therapy

In the era of cytomegalovirus (CMV)-preemptive therapy, it is unclear whether CMV serostatus of donor or recipient affects outcome of allogeneic hematopoietic stem cell transplantation (HSCT) among children with leukemia. To investigate, consecutive patients aged 0-18 who underwent primary HSCT for acute leukemia in 1997-2007 (HLA-matched sibling or unrelated donor, myeloablative conditioning, unmanipulated bone marrow or peripheral blood, preemptive therapy, no CMV prophylaxis) were followed retrospectively through January 2008. Treatment failure (relapse or death) was analyzed using survival-based proportional hazards regression. Competing risks (relapse and nonrelapse mortality, NRM) were analyzed using generalized linear models of cumulative incidence-based proportional hazards. Excluding 4 (2.8%) patients lacking serostatus of donor or recipient, there were 140 subjects, of whom 50 relapsed and 24 died in remission. Pretransplant CMV seroprevalence was 55.7% in recipients, 57.1% in donors. Thirty-five (25.0%) grafts were from seronegative donor to seronegative recipient (D-/R-). On univariate analysis, D-/R- grafts were associated with shorter relapse-free survival (RFS) than other grafts (median 1.06 versus 3.15 years, P < .05). Adjusted for donor type, diagnosis, disease stage, recipient and donor age, female-to-male graft, graft source, and year, D-/R- graft was associated with relapse (hazards ratio 3.15, 95% confidence interval 1.46-6.76) and treatment failure (2.45, 1.46-4.12) but not significantly with NRM (2.00, 0.44-9.09). In the current era, children who undergo allogeneic HSCT for acute leukemia have reduced risk of relapse and superior RFS when recipient and/or donor is CMV-seropositive before transplantation. However, no net improvement in RFS would be gained from substituting seropositive unrelated for seronegative sibling donors.

Vascular Endothelial Growth Factor and Activin-A Serum Levels Following Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation is frequently complicated by syndromes characterized by a disruption of the endothelial integrity such as graft-versus-host disease or liver toxicity. Vascular endothelial growth factor and activin-A, a member of the transforming growth factor beta (TGF-beta) superfamily, are important for endothelial integrity and tissue repair. We retrospectively measured endogenous vascular endothelial growth factor and activin-A serum levels in 70 patients following allogeneic stem cell transplantation. Vascular endothelial growth factor serum levels were significantly decreased within the first 2 weeks after the transplant and returned to pre transplant levels by day +15. Activin-A serum levels were significantly elevated from day +7 with peak levels reached on day +10. By using the median value as cutoff high vascular endothelial growth factor levels on day +15 were associated with significantly better overall survival, less liver toxicity, faster neutrophil recovery, and a trend towards less severe acute graft-versus-host disease. No correlation was found between activin-A serum levels and survival, liver toxicity, neutrophil recovery, or graft-versus-host disease. Monitoring of vascular endothelial growth factor levels following allogeneic hematopoietic stem cell transplantation might help to identify patients with a very high risk for early transplant-related complications.

Impact of natural killer cell dose and donor killer-cell immunoglobulin-like receptor (KIR) genotype on outcome following human leucocyte antigen-identical haematopoietic stem cell transplantation

To define the role of quantitative graft composition and donor killer-cell immunoglobulin-like receptor (KIR) genotype in clinical outcome following unmanipulated peripheral blood stem cell transplantation (PBSCT) from human leucocyte antigen (HLA)-identical siblings, 43 consecutive transplants for haematological malignancies were analysed retrospectively. Twenty-four patients underwent myeloablative conditioning and 19 received busulphan/fludarabine-based reduced intensity conditioning (RIC). In patients with acute myelogenous leukaemia or myelodysplastic syndrome (AML/MDS; n = 18), no relapse occurred following transplants meeting both a high (above median) natural killer (NK) cell count and missing HLA-ligand(s) to donor's KIR(s), compared to all other AML/MDS patients (0% versus 44%; P = 0.049). Missing HLA-B and/or HLA-C ligand combined with missing HLA-A3/11 (KIR3DL2 unblocked) predicted for reduced relapse incidence regardless of diagnosis or conditioning type (P = 0.028). Moreover, in AML/MDS patients, this constellation predicted superior overall survival (OS) (P = 0.046). Transplants with more than two different activating donor KIRs were associated with an increased risk for non-relapse mortality (NRM), both by univariate and multivariate analysis. Quantitative graft composition had a significant impact exclusively in RIC transplants. Here, a trend towards reduced relapse incidence was found in patients receiving high numbers of NK cells (16% versus 54%; P = 0.09). In patients receiving high versus low T cell numbers, OS was superior (83% versus 37%; P = 0.01), due mainly to reduced NRM (0% versus 33%; P = 0.046). By multivariate analysis, relapse risk was decreased significantly in patients receiving high NK cell numbers (P = 0.039). These data suggest that both the number of transplanted NK cells and the donor KIR genotype play a role in graft-versus-malignancy mechanisms in HLA-identical PBSCT.