Mixed Chimerism In Patients Research Articles

Age Impacts Risk of Mixed Chimerism Following Reduced-Intensity Conditioning Hematopoietic Cell Transplantation for Non-Severe Combined Immune Deficiency Inborn Errors of Immunity

Alemtuzumab, fludarabine, and melphalan containing-reduced intensity conditioning (RIC) is commonly used in patients undergoing allogeneic hematopoietic cell transplantation (HCT) for definitive treatment of high-risk inborn errors of immunity (IEI). Although survival is favorable, there is an increased risk of mixed chimerism leading to secondary graft failure. This study evaluated factors associated with the risk of developing mixed chimerism, particularly the influence of age in patients undergoing allogeneic HCT for non-severe combined immune deficiency (SCID) IEI who received a uniform RIC regimen that included intermediate schedule alemtuzumab, fludarabine, and melphalan. We hypothesized that age would impact the incidence of mixed chimerism. We retrospectively reviewed records of patients who underwent HCT for non-SCID IEI with a uniform RIC regimen that included intermediate schedule alemtuzumab (1 mg/kg divided over days -14 to -10), fludarabine (150 mg/m2 or 5 mg/kg if weight <10 kg divided over days -9 to -4), and melphalan (140 mg/m2 or 4.7 mg/kg if weight <10 kg on day -3) between 2010 and 2020 at our institution. Mixed chimerism was defined as <95% donor chimerism on 2 or more consecutive occasions in whole blood. Ninety-three patients who underwent RIC-HCT for non-SCID IEI using intermediate schedule alemtuzumab, fludarabine, and melphalan were categorized into 3 groups: age <1 year, age 1 to 5 years, and age >5 years. Forty-nine patients (52.7%) developed mixed chimerism, at a median of 34 days post-HCT (range, 10 to 1396 days). Mixed chimerism developed in 88.9% (n=16/18) of the age <1 year group, in 57.1% (n=20/35) of the age 1 to 5 years group, and in 35% (n =14/40) of the age >5 years group. Patients age <5 years were significantly more likely to develop mixed chimerism (χ2(3,N=93)=14.8; P=.001). We observed a significantly increased cumulative incidence of developing mixed chimerism associated with age <1 year (P=.0002). Competing risk regression analysis showed a 3-fold higher risk of developing mixed chimerism for age <1 year (subdistribution hazard ratio (HR), 3.05; 95% confidence interval [CI], 1.11 to 8.38; P=.031,) compared to age >5 years and a significantly decreased risk of mixed chimerism in patients who developed acute GVHD prior to any intervention (OR, .24; 95% CI, .09 to .65; P=.005) There were no significant associations between mixed chimerism and graft source, graft type, CD34+ or CD3+ cell dose, HLA match, or underlying disease (hemophagocytic lymphohistiocytosis [HLH] versus non-HLH). Additionally, the need for secondary intervention was evaluated; 27 patients (29.0%) required 1 or more secondary interventions (donor lymphocyte infusion, CD34 boost, or second HCT). Patients age <1 year with mixed chimerism were significantly more likely than patients age >5 years to require secondary intervention for mixed chimerism (P=.004). Our study demonstrates that age <5 years, especially age <1 year, is associated with an increased risk of developing mixed chimerism in patients undergoing RIC-HCT for non-SCID IEI using intermediate-schedule alemtuzumab, fludarabine, and melphalan. Our data suggest tailoring regimen intensity based on age to reduce the incidence of mixed chimerism. Children age <5 years, particularly those age <1 year, require a higher-intensity regimen. Possible strategies include adding thiotepa or using a busulfan-based reduced toxicity regimen.

Can novel methods replace the gold standard chimerism method after allogeneic hematopoietic stem cell transplantation?

After hematopoietic stem cell transplantation, chimerism assay is a useful approach to monitor the success of the transplant and to select the appropriate treatment strategy, such as donor leukocyte infusion or immunosuppressive drug dosage. Short tandem repeat PCR is the method that has been accepted as the gold standard for chimerism. However, it has not yet been sufficient to detect mixed chimerism in patients with minimal residual disease. Simultaneously, recent years have been marked by developing sensitive, high-throughput, and accurate molecular genetic assays. These novel methods have subsequently been adapted for the analysis of post-transplant chimerism. In this review, we discuss the technical features of both novel and conventional gold standard chimerism assays. We also discuss their advantages and disadvantages.

Long-term survival with mixed chimerism in patients with AML and MDS transplanted after conditioning with targeted busulfan, fludarabine, and thymoglobulin.

We evaluated long-term outcome in 40 patients with MDS or AML, transplanted from related or unrelated donors following conditioning with targeted busulfan (Bu, over 4 days), fludarabine (Flu, 120 [n = 23] or 250 [n = 17] mg/m2) and thymoglobulin (THY). Compared to 95 patients conditioned with Bu/Cyclophosphamide (Cy) without THY, BuFluTHY-conditioned patients had lower rates of chronic graft-vs.-host disease (GVHD). Adjusted hazard ratios (HR) for BuFlu(120)THY and BuFlu(250)THY-conditioned patients were 1.60 (95% confidence interval (CI) 0.66-3.86) and 1.87 (0.68-5.11), respectively, for relapse; 0.77 (0.30-1.99) and 1.32 (0.54-3.23) for non-relapse mortality; 0.81 (0.42-1.57) and 1.38 (0.72-2.57) for overall mortality; and 0.78 (0.30-2.05) and 1.62 (0.63-4.41) for relapse or death (failure for relapse-free survival). At one year, 45% of BuFlu(120 or 250)THY-conditioned patients had mixed CD3+ chimerism compared to 0% with BuCy (p < 0.0001). None of 7 patients with long-term mixed chimerism had chronic GVHD; two relapsed, five remained stable mixed chimeras. THY is effective in reducing chronic GVHD, and long-term mixed T-cell chimerism can be compatible with relapse-free survival. However, Thy may also be associated with an increased risk of relapse and, dose-dependent, with non-relapse mortality.

Lymphohematopoietic graft-versus-host responses promote mixed chimerism in patients receiving intestinal transplantation.

In humans receiving intestinal transplantation (ITx), long-term multilineage blood chimerism often develops. Donor T cell macrochimerism (≥4%) frequently occurs without graft-versus-host disease (GVHD) and is associated with reduced rejection. Here we demonstrate that patients with macrochimerism had high graft-versus-host (GvH) to host-versus-graft (HvG) T cell clonal ratios in their allografts. These GvH clones entered the circulation, where their peak levels were associated with declines in HvG clones early after transplant, suggesting that GvH reactions may contribute to chimerism and control HvG responses without causing GVHD. Consistently, donor-derived T cells, including GvH clones, and CD34+ hematopoietic stem and progenitor cells (HSPCs) were simultaneously detected in the recipients' BM more than 100 days after transplant. Individual GvH clones appeared in ileal mucosa or PBMCs before detection in recipient BM, consistent with an intestinal mucosal origin, where donor GvH-reactive T cells expanded early upon entry of recipient APCs into the graft. These results, combined with cytotoxic single-cell transcriptional profiles of donor T cells in recipient BM, suggest that tissue-resident GvH-reactive donor T cells migrated into the recipient circulation and BM, where they destroyed recipient hematopoietic cells through cytolytic effector functions and promoted engraftment of graft-derived HSPCs that maintain chimerism. These mechanisms suggest an approach to achieving intestinal allograft tolerance.

Mixed chimerism after allogeneic hematopoietic stem cell transplantation for severe aplastic anemia

ABSTRACT Background: Mixed chimerism (MC) frequently occurs in patients with severe aplastic anemia (SAA) after allogeneic hematological stem cell transplantation (allo-HSCT). Methods A retrospective study on 287 patients with SAA who underwent allo-HSCT between October 2012 and January 2020 was conducted to explore the outcomes, risk factors and treatment options for MC. Among 287 AA patients who excluded Fanconi anemia (FA), Congenital dyskeratosis (DKC), Paroxysmal nocturnal hemoglobinuria (PNH), etc.112 underwent matched sibling donor (MSD)-HSCT, 91 matched unrelated donor-HSCT and 84 haploidentical-HSCT. Patients were divided into the following 4 groups: group 1: Donor chimerism (DC); group 2: MC without cytopenia; group 3: MC with cytopenia; group 4: secondary graft failure (SGF). Results Compared with the other three groups, SGF predicted a poor prognosis of SAA (P< 0.001). In addition, SGF was associated with the early (within 3 months after transplantation) presence of MC and the high levels of MC. Uni- and multivariate logistic regression analysis showed that donor/recipient sex-mismatching and CTX + ATG regimen were high-risk factors for MC. Of note, in MC patients with cytopenia (group 3), the effective response rate reached 55% (6/11) following enhanced immunosuppression combined with cellular therapy, while only one of the four was effective who received enhanced immunosuppression alone. Conclusion SGF was associated with poor prognosis, early presence of MC and increased levels of recipient chimerism. The donor/recipient sex-mismatching and CTX + ATG regimen based MSD-HSCT were risk factors for MC. Cellular therapy could improve the effective response rate of patients with progressive MC.

Does Mixed Chimerism After Allogeneic Hematopoietic Cell Transplantation in Pediatric Patients With Fanconi Anemia Impact on Outcome?

Fanconi anemia (FA) cells are characterized by genomic instability, which places FA patients at risk for malignancies such as leukemia and oropharyngeal/urogenital cancers. The risk of development of leukemia is theoretically eliminated after hematopoietic cell transplantation (HCT). Mixed chimerism (MC) in FA patients might have a unique implication because the persistent existence of FA cells might give rise to a malignant clone. We have studied a large population of FA patients who underwent allogeneic HCT at our institution and report here the outcome according to chimerism status. Patients with FA who had evidence of progressive bone marrow failure and were blood products-transfusion dependent (packed red blood cells, platelets, or both) were included in the study. Those who had myelodysplasia (MDS) or an abnormal clone or evidence of leukemia were excluded. All but 3 patients had normal renal and cardiac function at the time of transplantation. In total, 160 patients with FA underwent allogeneic HCT at our center from January 1995 to December 2017; mean age at HCT was 8.4. Chimerism data at last follow-up visit were available on 97 patients who are the subjects of this analysis (no day +100 chimerism data on one of them). On day +100, 46 patients (47.9%) had full chimerism (FC) and 50 (52.1%) had MC, whereas at last follow-up 50 (51.5%) exhibited FC and the remaining 47 (48.5%) had MC. Cumulative incidence of all grades acute graft-versus-host disease (GVHD) was 13.4% and that of grade III to IV GVHD was 4.1%. Chronic GVHD was seen in eight (8.0%) patients. Incidence of severe acute GVHD (grade ≥ III) and that of chronic GVHD were not significantly associated with FC or MC measured at day +100 (P values=.347 and .254, respectively), nor at the last follow-up. Graft failure occurred in 2 patients; both from the MC at day +100 group. No graft failures occurred in the FC at day +100 group (P value=1.00). At a median follow-up of 83.8 months (95% confidence interval, 51.0-116.6; range, 19.3-181.1 months) the cumulative probability of overall survival (OS) at 5 years was 95.7% ± 2.1%. Mean follow-up time in our cohort was 90.7 months. Five-year overall survival was not significantly associated with FC or MC evaluated at day +100 (95.7% ± 3.0% versus 95.6% ± 3.1%, P value=.908) nor at the last follow-up (96.0% ± 2.8% versus 95.4% ± 3.2%, P value = .925). No patient in either group developed MDS/leukemia during the follow-up period. We conclude that mixed chimerism in patients with FA appears to have no adverse effect on outcome in our follow-up period. A longer follow-up period is needed, however, to confirm the validity of this statement.

Mixed Chimerism after Allogeneic Hematopoietic Stem Cell Transplantation in Patients with β Thalassemia: Impact on Outcome and Risk Factors

Background: Hematopoietic stem cell transplantation (HSCT) is the most effective curative option for patients with thalassemia major(TM). Early post-transplant mixed chimerism (MC) has known to be a predictor of secondary graft rejection. However, the impact of the persisting mixed chimerism on transplant outcome remains controversial. Recently Thiotepa(TT) has been decreased to reduce toxicity.There was no data available on reduced intensity conditioning on mixed chimersim in a large group of patients with thalassemia to date. Aims: To assess risk factors of mixed chimerism and to evaluate possible correlations between mixed chimerism and the development of complications after HSCT, in terms of graft versus host disease (GVHD) development, OS, TFS and GR. Patients and methods: From December2008 until December 2019, 618 patients with TM underwent HSCT at our center with median age of 6 (1-23) and median follow up time of 70 months(1-135), from HLA-identical sibling donors (SD) (n=212; 34.3%), unrelated donors (UD, n=313; 50.6%),sibling Cord blood(CB, n=49,7.9%)and parent donors (PD, n=44,7.1%). Source of graft were 538 (87.1%) from peripheral stem cells, 32(5.2%) from bone marrow and 48(7.8%)from sibling cord blood. Cy+Bu+Flu+TT+ATG conditioning regimen was used in 416 pts while a reduced conditioning regimen Cy+Bu+Flu+ATG was used for 167pts and Cy+Bu+Flu for the other 35 pts. Results Overall Survival (OS), Thalassemia-Free survival (TFS), Transplantation-related mortality (TRM) and graft rejection (GR) for the entire group were 94.8%, 92.7% ,5.2% and 2.4% respectively. MC was presented in 70 pts with 52 male and 18 female, defined as the presence of &amp;gt;5% residual recipient cells. Cumulative incidence of MC was 12.4% (Figure1). 5 pts had secondary graft failure and another 5 patients persisting MC post-transplant refractory to DLI following a second HSCT. There were two deaths ineffective to DLI and one die of idiopathic pneumonia and one of hemolytic uremic syndrome. The median MC present time was 4 months (1-59 months).No significant difference was observed in OS and Thalassemia-Free survival (TFS) between MC and PC pts. The cumulative probability of OS, TFS between MC pts and FC pts was 97.1% vs. 94.4% (P=0.343) and 89.6% vs. 93.2% (P=0.272). However, the incidence of MC was significantly associated with the development of graft failure/rejection. Graft failure occurred in 5 pts in the MC group vs.7 pts in the full donor chimerism (PC) group, the corresponding incidence were 7.6% vs. 1.6 % respectively. (P =0.001, Figure 2). Acute GVHD incidence was much lower in MC pts than in PC pts (2.9% vs. 12.7%, P=0.022, Figure 3 A), whereas MC pts had significantly higher chronic GVHD(16.8% vs. 4.2%, P=0.000 Figure 3 B). 2 of 70 MC pts developed I-II aGVHD. No MC pts develop II-IV aGVHD. MC patients were unlikely to have severe acute GVHD. MC was associated with an increased risk of chronic GVHD, mostly were DLI derived Patients receiving stem cells from cord blood of matched sibling donors had a high risk of MC.MC incidence of stem cell source from peripheral blood(PB), bone marrow(BM), cord blood (CB)were 10.6%, 10%, 34.2% respectively.(P=0.000, Figure 4). Unrelated donors had a lower risk of MC than sibling donors. Incidence of MC from unrelated donors was 9.5% vs. 16.1% from sibling donors (P=0.007, Figure 5) Intravenous Thiotepa (TT) in combination with Busulfan (Bu) , cyclophosphamide (Cy) anti-thymocyte globulin(ATG) on HSCT could reduce the risk of MC. The corresponding incidence of MC in Cy+Bu+Flu+TT+ATG, Cy+Bu+Flu+ATG, Cy+Bu+Flu conditioning regimen were 9.2%,15.9%,40.9% resepectively(P=0.000, Figure 6). There was also a significant difference in chimerism based on donor-recipient gender pairing (P = 0.041): male grafts into male patients having the greatest risk of MC and female grafts into female patients having the least. Patients who under 9 years old had a higher risk of MC than that of pts&amp;gt;9 years old (P=0.018, Figure 7), Summary: Our results show that patients who presented mixed chimerism showed a similar post-transplant outcome in OS and TFS but was associated with higher risk of graft failue.Patients receiving stem cells from CB had a high risk of MC than from PBSC. Reduced nonmyeloablative approach capable of achieving allogeneic mixed hematopoietic chimerism. Our data suggests that Cy+Bu+Flu+TT+ATG is a preferred conditioning regimenfor TM patients could reduce the risk of mixed chimerism. Disclosures No relevant conflicts of interest to declare.

Alemtuzumab Controls Acute GVHD and Mixed Chimerism Risks in Pediatric Patients with HLH Undergoing Stem Cell Transplantation: A Correlative Biology Study from the CTN 1204 Richi Trial

A reduced intensity conditioning regimen consisting of alemtuzumab, fludarabine, and melphalan has been shown to be associated with superior survival in patients with hemophagocytic lymphohistiocytosis, but is complicated by a high risk of mixed chimerism and secondary graft failure. We hypothesized that peri-transplant alemtuzumab levels impact the risks of both acute GVHD and mixed chimerism in patients with HLH undergoing RIC HCT. We tested this hypothesis in a companion correlative biology study to the Blood and Marrow Transplant Clinical Trials Network (CTN) prospective 1204 trial, Reduced-Intensity Conditioning for Children and Adults with Hemophagocytic Syndromes or Selected Primary Immune Deficiencies. The HCT RIC regimen included alemtuzumab (mg/kg subcutaneous, maximum cumulative dose of 90mg, divided over days −14 through −10), fludarabine (150mg/m2 or 5mg/kg in patients Our cohort was 74% male with a median age of 2.1 years (range 0.4-18.9). Nine patients (39%) developed acute GVHD not associated with donor lymphocyte infusion (DLI). Acute GVHD was associated with lower Day 0 alemtuzumab levels. Sixty-seven percent of patients with Day 0 levels 0.67μg/ml (p=0.0078) (Figure 1). Seventeen patients (74%) developed mixed chimerism, defined as whole blood donor chimerism Alemtuzumab level at day 0 significantly impacts the risks of acute GVHD and mixed chimerism. Studies to test precision dosing strategies to target peri-transplant levels of alemtuzumab to appropriate therapeutic ranges are underway, and future implementation may lead to improved outcomes.

Donor Lymphocyte Infusions Used to Treat Mixed-Chimeric and High-Risk Patient Populations in the Relapsed and Nonrelapsed Settings after Allogeneic Transplantation for Hematologic Malignancies Are Associated with High Five-Year Survival if Persistent Full Donor Chimerism Is Obtained or Maintained

Mixed chimerism (MC), a persistent or increasing number of host cells after allogeneic hematopoietic stem cell transplantation (HSCT), is a predictor of disease relapse. Donor lymphocyte infusions (DLI) have the potential to enhance the graft-versus-malignancy (GVM) effect, reducing the risk of relapse in patients with MC. Hence, in addition to utilizing DLI in the relapsed setting, there is a motivation to pursue pre-emptive DLI for patients in complete remissions after HSCT. To assess the safety and efficacy of DLI, records of 86 patients who received DLI between 2003 and 2015 at a single institution were studied retrospectively. Patients who received DLI included 50 patients with relapsed/residual (RR) disease, 29 patients with emerging MC without detectable disease, and 7 patients in an “other” cohort who had neither RR disease nor emerging MC after HSCT. DLI were administered using a dose-escalation protocol. After DLI, 93% of MC patients converted to full donor chimerism (FDC). Nonrelapsed patients (MC and other) reported high overall survival (OS) at 1 and 5 years (83% at 1 year, 70% at 5 years for MC; 86% at 1 year, 69% at 5 years for other) and was statistically superior to 5-year OS for RR patients (nonrelapsed 69% versus RR 28%; P = .00032). Improved survival correlated with successful conversion to FDC after DLI for RR and MC cohorts: 71% 2-year OS for patients converted to FDC versus 13% for patients who failed to achieve FDC (P < .0001). DLI for nonrelapsed patients was associated with a superior 5-year progression-free survival (PFS) of 71% compared with 18% 5-year PFS in the RR group (P < .0001). Relapse/progressive disease was the most frequent cause of death (41%). Seven MC (24%), 2 other (29%), and 39 RR patients (78%) relapsed or did not respond after DLI. Overall, 6 patients (7%) died of graft-versus-host disease after DLI. Our results demonstrate a successful dose-escalation approach for nonrelapsed patients that correlated with high survival and a high rate of achieving FDC in MC and RR populations. DLI remain a viable option to boost the GVM effect in the relapsed setting and may pre-emptively protect against relapse in MC populations after HSCT.

Donor Lymphocyte Infusions Used to Treat Mixed Chimerism in Relapsed and Non-Relapsed Patient Populations after Allogeneic Transplant for Hematologic Malignancies Are Associated with High 5-Year Survival If Persistent Full Donor Chimerism Is Obtained

BackgroundMixed chimerism, a persistent or increasing number of host cells, after allogeneic hematopoietic stem cell transplant (allo-HSCT) is a predictor of disease relapse. Donor lymphocyte infusion (DLI) has the potential to enhance the graft vs. malignancy effect and reduce the risk of relapse in patients with mixed chimerism (MC) and in patients at high-risk (HR) for relapse. Hence, there is a motivation to utilize DLI for patients with hematologic malignancies while in complete remission (CR) after transplant to prevent disease relapse. To assess the safety and efficacy of DLI after allo-HSCT, in both the relapsed and non-relapsed settings, records of 88 patients receiving DLI between 2003 and 2015 at a single institution were retrospectively reviewed.Patients & MethodsMedian age at time of transplant was 53 (range, 18-68 years). Fifty-four patients received allo-HSCT from related donors (RD) and 34 patients received allo-HSCT from matched unrelated donors (MUD). Reasons for DLI were relapsed/residual disease (n=52, 59%), MC with no evidence of disease (n=29, 33%), and HR with no evidence of disease (n=7, 8%). 44 of 52 relapsed/residual disease patients received treatment before DLI (41 chemotherapy, 4 other, 7 no treatment). 17/52 patients (33%) were treated within 6 months of transplant, the rest after 6 months.DLI was administered according to a dose-escalating protocol in 4-8 week intervals. Starting dose varied based on donor and disease status: 1.0x107 CD3+ cells/kg for relapse/residual RD, 3.0x106 CD3+ cells/kg for relapse/residual MUD, 3.0x106 CD3+ cells/kg for MC/HR RD and 1.0x106 CD3+ cells/kg for MC/HR MUD. Endpoints to discontinue DLI included: full donor chimerism (FDC), remission, GvHD development, disease progression, or lack of further donor cells.ResultsMedian interval from transplant to DLI was 195 days (range, 50-2026 days) and median number of DLI infusions was 2 (range, 1-7 infusions). From first DLI, 1 year overall survival (OS) rates were 52%, 83%, and 86% for relapse/residual, MC, and HR populations respectively. 5 year OS rates were 27%, 70%, and 71%, respectively. Cumulative incidence of acute GvHD grade III-IV and extensive chronic GvHD was 33% (29/88 patients). Six patients died of GvHD-related toxicities (7%).In the relapsed setting, 31/52 patients (60%) responded to DLI with disease control, of whom 12/52 (23%) had durable remissions/disease control while 19/52 (36.5%) eventually relapsed or had disease progression. Thirty-four patients had MC at the time of relapse, and 20/34 patients (59%) returned to FDC after DLI. All 14 patients who did not re-establish FDC after DLI relapsed or had disease progression. Relapse/disease progression remained the most frequent cause of death in the relapsed/residual population, 56%. The 1-year OS was 29% for those who relapsed within 6 months of transplant, 64% for those who relapsed beyond 6 months. The 5 year OS was 18% for those relapsed within 6 months, 33% for those who relapsed beyond 6 months.DLI induced FDC in 27/29 patients (93%) in the MC population, with durable FDC and ongoing CR in 22/29 patients (76%). Seven MC patients (24%) relapsed after DLI. In the HR population, DLI was protective against relapse in 5 patients while 2 patients (29%) relapsed after DLI.ConclusionsNinety three percent of MC patients in the non-relapsed setting achieved FDC after DLI, with a 24% relapse rate over five years. Further, pre-emptive DLI in patients with MC or HR is associated with a 70% 5 year OS. These results suggest a clinically meaningful effect of pre-emptive and prophylactic DLI in MC and HR patient populations. For patients with MC, both relapsed and non-relapsed, achieving FDC after DLI is essential for disease control. All 17 patients in both populations that did not achieve FDC had non-durable responses or no responses to DLI with subsequent disease progression. Fifteen of the 17 patients who did not achieve FDC after DLI died due to disease progression, while the remaining 2 underwent a second allo-HSCT. DLI for HR was associated with significant rates of acute >grade II and extensive chronic GvHD. In this population, development of GvHD may not be the optimal endpoint, in order to limit GvHD-attributable mortality. [Display omitted] DisclosuresAkard:Ariad, BMS, Celgene, Gilead, Novartis, Takeda: Speakers Bureau.

Pre-Emptive Immunotherapy for Clearance of Molecular Disease in Childhood Acute Lymphoblastic Leukemia after Transplantation

Monitoring of minimal residual disease (MRD) or chimerism may help guide pre-emptive immunotherapy (IT) with a view to preventing relapse in childhood acute lymphoblastic leukemia (ALL) after transplantation. Patients with ALL who consecutively underwent transplantation in Frankfurt/Main, Germany between January 1, 2005 and July 1, 2014 were included in this retrospective study. Chimerism monitoring was performed in all, and MRD assessment was performed in 58 of 89 patients. IT was guided in 19 of 24 patients with mixed chimerism (MC) and MRD and by MRD only in another 4 patients with complete chimerism (CC). The 3-year probabilities of event-free survival (EFS) were .69 ± .06 for the cohort without IT and .69 ± .10 for IT patients. Incidences of relapse (CIR) and treatment-related mortality (CITRM) were equally distributed between both cohorts (without IT: 3-year CIR, .21 ± .05, 3-year CITRM, .10 ± .04; IT patients: 3-year CIR, .18 ± .09, 3-year CITRM .13 ± .07). Accordingly, 3-year EFS and 3-year CIR were similar in CC and MC patients with IT, whereas MC patients without IT experienced relapse. IT was neither associated with an enhanced immune recovery nor an increased risk for acute graft-versus-host disease. Relapse prevention by IT in patients at risk may lead to the same favorable outcome as found in CC and MRD-negative-patients. This underlines the importance of excellent MRD and chimerism monitoring after transplantation as the basis for IT to improve survival in childhood ALL.

Peripheral blood late mixed chimerism in leucocyte subpopulations following allogeneic stem cell transplantation for childhood malignancies: does it matter?

The impact of persistent mixed chimerism (MC) after haematopoietic stem cell transplantation (HSCT) remains unclarified. We investigated the incidence of MC in peripheral blood beyond day +50 after HSCT and its impact on rejection, chronic graft-versus-host disease (c-GvHD) and relapse in 161 children receiving allogeneic HSCT for haematological malignancies. The 1-year incidence of late MC was 26%. Spontaneous conversion to complete donor chimerism (CC) occurred in 43% of patients as compared to 62% after donor lymphocyte infusions. No graft rejection occurred. The 1-year incidence of c-GvHD was 20±7% for MC, and 18±4% for CC patients (P=0·734). The 3-year cumulative incidence of relapse (CIR) according to chimerism status at days +50 and +100 was 22±4% for CC patients vs. 22±8% for MC patients (day +50; P=0·935) and 21±4% vs. 20±7% (day +100; P=0·907). Three-year CIRs in patients with persistent MC and patients with CC/limited MC were comparable (8±7% vs. 19±4%; P=0·960). HSCT for acute leukaemia or myelodysplastic syndrome as secondary malignancies (hazard ratio (HR) 4·7; P=0·008), for AML (HR 3·0; P=0·02) and from mismatched donors (HR 3·1; P=0·03) were independent factors associated with relapse. Our data suggest that late MC neither protects from c-GvHD nor does it reliably predict impending disease relapse.

Excellent outcome with a high proportion of mixed chimerism in patients with severe aplastic anemia treated with partially T-cell-depleted peripheral hematopoietic stem cell transplants.

Excellent outcome with a high proportion of mixed chimerism in patients with severe aplastic anemia treated with partially T-cell-depleted peripheral hematopoietic stem cell transplants

Alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following alemtuzumab, fludarabine, and melphalan RIC HCT

AbstractReduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) with alemtuzumab, fludarabine, and melphalan is an effective approach for patients with nonmalignant disorders. Mixed chimerism and graft-versus-host-disease (GVHD) remain limitations on success. We hypothesized that higher levels of alemtuzumab at day 0 would result in a low risk of acute GVHD, a higher risk of mixed chimerism, and delayed early lymphocyte recovery and that alemtuzumab level thresholds for increased risks of these outcomes would be definable. We collected data from 105 patients to examine the influence of peritransplant alemtuzumab levels on acute GVHD, mixed chimerism, and lymphocyte recovery. The cumulative incidences of initial grades I-IV, II-IV, and III-IV acute GVHD in patients with alemtuzumab levels ≤0.15 vs ≥0.16 μg/mL were 68% vs 18% (P < .0001), 47% vs 13% (P = .0002), and 32% vs 8%, respectively (P = .005). The cumulative incidence of mixed chimerism in patients with an alemtuzumab level ≤0.15 μg/mL was 21%, vs 42% with levels of 0.16 to 4.35 μg/mL, and 100% with levels >4.35 μg/mL (P = .003). Patients with alemtuzumab levels ≤0.15 or 0.16 to 0.56 μg/mL had higher lymphocyte counts at day +30 and higher T-cell counts at day +100 compared with patients with levels ≥0.57 μg/mL (all P < .05). We conclude that peritransplant alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following RIC HCT with alemtuzumab, fludarabine, and melphalan. Precision dosing trials are warranted. We recommend a day 0 therapeutic range of 0.2 to 0.4 μg/mL.

Mixed Chimerism at Three Months after Allogeneic Hematopoietic Stem Cell Transplantation Is a Significant Predictor of Disease Relapse in High-Risk Acute Myeloid Leukemia Patients in First Complete Remission

Background:Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potential curative strategy for high-risk acute myeloid leukemia (AML) patients. However, the risk for disease recurrence following allo-HSCT remains significant and associated with poor outcomes. The ability to predict relapse before detectable morphologic recurrence may allow for preemptive interventions, such as immune modulation, donor lymphocyte infusion (DLI), or initiation of hypomethylating agents, to potentially augment graft-versus-leukemia effect. Post-transplantation peripheral blood chimerism analysis, represents a potential tool to predict disease recurrence, although a validated consensus on the use of this technique in the post-allo-HSCT follow-up has not been established yet and its precise role in this setting remains unclear. The aim of our study is to evaluate the impact of chimerism evaluation 3 months after allo-HSCT in AML patients who were in first complete remission (CR1) before transplantation and remained in clinical and morphological CR at day 90 post-transplantation, on overall survival (OS) and relapse incidence.Patients and methods:We evaluated 194 AML patients who received allo-HSCT at our center between January 2006 and December 2014 and for whom chimerism follow-up has been performed at 3 months. There were 103 (53%) males and 91 (47%) females with a median age of 43 years (range: 18-67). Patients were classified according to the European LeukemiaNet classification for cytogenetic and molecular biology markers (Dohner et al. Blood 2010), accordingly, 64% patients were unfavorable and 36% were in intermediate II risk group. At allo-HSCT, all patients were in CR1; 136 (70%) received a full intensity conditioning (MAC) and 58 (30%) received a reduced intensity conditioning (RIC). HSC donors were 72 (37%) HLA identical siblings (44 BM and 36 PBSC), 54 (28%) 10/10 HLA matched unrelated donors (35 BM and 19 PBSC), 33 (17%) 9/10 HLA mismatched unrelated donors (16 BM and 17 PBSC) and 35 (18%) double cord blood units (only 7 were 6/6 HLA matched). Chimerism analysis was performed on marrow and/or blood samples every month following allo-HSCT using polymerase chain reaction (PCR) based on informative polymorphic short tandem repeat, a mixed chimerism was defined by having 5% or more of recipient cells.Results:At day 90 after transplantation, all patients remained in clinical and cytological CR at time of chimerism evaluation, 155 (80%) had a full donor chimersim (FDC) and 39 (20%) had a mixed chimerism (MC) ranging from 65% to 95% of donor cells. Among patients with MC, 9 (23%) received increasing doses of DLI (5 of them reached FDC at 6 months), while 20 (51%) could not receive DLI (7 because transplanted from cord blood, and 13 because of the presence of GVHD), the rest of patients were left with a transient MC and regained FDC during follow-up.After a median follow-up of 34 months (range: 4-96) for the surviving patients, the median OS in patients with FDC was not reached with a 3 years probability of 62% (95% CI: 58-66), and for patients with MC, it was 18 months (12-24) with a 3 years probability of 32% (95% CI: 23-41), (p=0.01). Twenty-two patients in the MC group have progressed during the follow-up and 17 among them died from disease progression. The cumulative incidence of relapse at 3 years was 25% (95% CI: 21-29) for FDC patients and it was 70% (95% CI: 62-80) for MC patients, (p<0.001). The impact of mixed chimerism was still valid in multivariate analysis after including patient age, type of donor, HSC source and risk group, and was independent from the intensity of the conditioning regimen with a Hazard Ratio of 4.7, and a 95% CI: 2.6-8.4, p<0.001.Conclusion:We demonstrated that chimerism evaluation at day 90 after allo-HSCT is an independent predictor of disease relapse in patients who remain in CR at that time and significantly impacts on long term survival. The standardization of this evaluation may lead to the identification of patients with high-risk of relapse risk suggesting the need of early preemptive intervention. [Display omitted] DisclosuresNicolini:Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Ariad Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Long-Term Stable Mixed Chimerism in Patients Undergoing HSCT for Non-Malignant Disorders

Long-Term Stable Mixed Chimerism in Patients Undergoing HSCT for Non-Malignant Disorders

Chimerism Patterns of Long-Term Stable Mixed Chimeras Posthematopoietic Stem Cell Transplantation in Patients with Nonmalignant Diseases: Follow-Up of Long-Term Stable Mixed Chimerism Patients

Long-term stable mixed chimerism (MC) is a rare phenomenon after hematopoietic stem cell transplantation (HSCT) characterized by 5% to 95% residual recipient hematopoietic cells. The underlying mechanisms of MC are largely unknown. In this study we compared full donor chimerism with long-lasting stable MC for a median of 9.5 years (range, 5 to 16.5) post-HSCT in patients with nonmalignant diseases. Several factors significantly associated with the likelihood of stable MC development were identified by univariate analysis, eg, younger donor age, sibling donor, and conditioning regimen. Despite a limited patient cohort, our multivariate analysis could confirm that a sibling donor was associated with stable MC development. Furthermore, development of acute-graft-versus-host disease and blood stream infection was significantly more prevalent in the full donor chimerism patient group. Additionally, significant fluctuations in the recipient-to-donor chimerism ratio decreased over time after HSCT in MC patients.

Persistent mixed chimerism in patients with severe combined immunodeficiency after cord blood transplantation

Persistent mixed chimerism in patients with severe combined immunodeficiency after cord blood transplantation

Chimerism patterns of long-term stable mixed chimeras post-HSCT in patients with non-malignant diseases

Event Abstract Back to Event Chimerism patterns of long-term stable mixed chimeras post-HSCT in patients with non-malignant diseases Arwen Stikvoort1, 2*, Jens Gertow1, 2, Mikael Sundin3, 4, Mats Remberger1, 2, Jonas Mattsson1, 2 and Michael Uhlin1, 2 1 Karolinska Institutet, Laboratory Medicine, Sweden 2 Karolinska University Hospital, Centre for Allogeneic Stem Cell Transplantation (CAST), Sweden 3 Karolinska Institutet, Clinical Sciences, Intervention and Technology (CLINTEC), Sweden 4 Karolinska University Hospital, Astrid Lindgren Children’s Hospital, Sweden Introduction. Long-term stable mixed chimerism (MC) is a rare phenomenon after hematopoietic stem cell transplantation (HSCT) characterized by 5-95% residual recipient hematopoietic cells. The mechanisms directing hematopoietic recovery to MC in some patients and to full donor chimerism (DC) in others are poorly understood. In this study we compared DC patients with long-lasting stable MC patients for a median of 9.5 years (range 5 – 16.5) post-HSCT in patients with non-malignant diseases. Methods. Chimerism analysis was performed for all patients at regular intervals post-HSCT on peripheral blood samples. The cell lineages analysed were T-lymphocytes (CD3), B-lymphocytes (CD19) and myeloid cells (CD33). Results. Several factors significantly associated with the likelihood of stable MC development were identified by univariate analysis, e.g. younger donor age, sibling donor and conditioning regimen. Despite a limited patient cohort, our multivariate analysis could confirm that a sibling donor was associated with stable MC development. Furthermore, development of acute-graft-vs.-host disease (aGvHD) and blood stream infection (BSI) was significantly more prevalent in the DC patient group. Additionally, significant fluctuations in the recipient:donor chimerism ratio decreased over time after HSCT in MC patients. Discussion. Sibling donor cells are a closer HLA and minor histocompatibility antigen match than unrelated donor cells and as thus will be less prone to induce immune-mediated killing of recipient cells. Additionally, milder conditioning regimens may also stimulate MC development. Furthermore, MC was not linked to a worse prognosis, as both aGvHD and BSI development were more prevalent in the DC group. Keywords: Hematopoietic Stem Cell Transplantation, Graft vs Host Disease, Sepsis, mixed chimerism, chimerism analysis Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Adaptive Immunity Citation: Stikvoort A, Gertow J, Sundin M, Remberger M, Mattsson J and Uhlin M (2013). Chimerism patterns of long-term stable mixed chimeras post-HSCT in patients with non-malignant diseases. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00513 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 May 2013; Published Online: 22 Aug 2013. * Correspondence: Ms. Arwen Stikvoort, Karolinska Institutet, Laboratory Medicine, Stockholm, Sweden, arwen.stikvoort@ki.se Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Arwen Stikvoort Jens Gertow Mikael Sundin Mats Remberger Jonas Mattsson Michael Uhlin Google Arwen Stikvoort Jens Gertow Mikael Sundin Mats Remberger Jonas Mattsson Michael Uhlin Google Scholar Arwen Stikvoort Jens Gertow Mikael Sundin Mats Remberger Jonas Mattsson Michael Uhlin PubMed Arwen Stikvoort Jens Gertow Mikael Sundin Mats Remberger Jonas Mattsson Michael Uhlin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Preemptive immunotherapy in childhood acute myeloid leukemia for patients showing evidence of mixed chimerism after allogeneic stem cell transplantation

AbstractPrevious studies have shown that children with acute myeloid leukemia (AML) who developed mixed chimerism (MC) were at high risk for relapse after allogeneic stem-cell transplantation (allo-SCT). We investigated the feasibility of intensified preemptive immunotherapy in children receiving allo-SCT for AML. Eighty-four children were registered in our trial from May 2005 to April 2009; of these, 71 fulfilled the inclusion criteria and were treated according to the study protocol. Serial and semiquantitative analyses of posttransplantation chimerism were performed. Defined immunotherapy approaches were considered in MC patients. Continuous complete chimerism (CC) was observed in 51 of 71 patients. MC was detected in 20 patients and was followed by immunotherapy in 13. Six of 13 MC patients returned to CC without toxicity and remained in long-term remission. Overall, the probability of event-free survival (pEFS) was 66% (95% confidence interval [95% CI] = 53%-76%) for all patients and 46% (95% CI = 19%-70%) in MC patients with intervention; however, this number increased to 71% (95% CI = 26%-92%) in 7 of 13 MC patients on immunotherapy who were in remission at the time of transplantation. All MC patients without intervention relapsed. These results suggest that MC is a prognostic factor for impending relapse in childhood AML, and that preemptive immunotherapy may improve the outcome in defined high-risk patients after transplantation.