Quantitative chimerism: an independent acute leukemia prognosis indicator following allogeneic hematopoietic SCT

Human amniotic epithelial stem cell is a cell therapy candidate for preventing acute graft-versus-host disease

Graft-versus-host disease (GVHD), an immunological disorder that arises from donor T cell activation through recognition of host alloantigens, is the major limitation in the application of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Traditional immunosuppressive agents can relieve GVHD, but they induce serious side effects. It is highly required to explore alternative therapeutic strategy. Human amniotic epithelial stem cells (hAESCs) were recently considered as an ideal source for cell therapy with special immune regulatory property. In this study, we evaluated the therapeutic role of hAESCs in the treatment of GVHD, based on our previous developed cGMP-grade hAESCs product. Humanized mouse model of acute GVHD (aGVHD) was established by injection of huPBMCs via the tail vein. For prevention or treatment of aGVHD, hAESCs were injected to the mice on day -1 or on day 7 post-PBMC infusion, respectively. We showed that hAESCs infusion significantly alleviated the disease phenotype, increased the survival rate of aGVHD mice, and ameliorated pathological injuries in aGVHD target organs. We demonstrated that hAESCs directly induced CD4+ T cell polarization, in which Th1 and Th17 subsets were downregulated, and Treg subset was elevated. Correspondingly, the levels of a series of pro-inflammatory cytokines were reduced while the levels of the anti-inflammatory cytokines were upregulated in the presence of hAESCs. We found that hAESCs regulated CD4+ subset polarization in a paracrine mode, in which TGFβ and PGE2 were selectively secreted to mediate Treg elevation and Th1/Th17 inhibition, respectively. In addition, transplanted hAESCs preserved the graft-versus-leukemia (GVL) effect by inhibiting leukemia cell growth. More intriguingly, hAESCs infusion in HSCT patients displayed potential anti-GVHD effect with no safety concerns and confirmed the immunoregulatory mechanisms in the preclinical study. We conclude that hAESCs infusion is a promising therapeutic strategy for post-HSCT GVHD without compromising the GVL effect. The clinical trial was registered at www.clinicaltrials.gov as #NCT03764228.

Laboratory methods of monitoring disease response after allogeneic haematopoietic stem cell transplantation for myelofibrosis

The era of molecular prognostication in myelofibrosis has allowed comprehensive assessment of disease risk and informed decisions regarding allogeneic haematopoietic stem cell transplantation (HSCT). However, monitoring disease response after transplantation is difficult, and limited by disease and sample-related factors. The emergence of laboratory techniques sensitive enough to monitor measurable residual disease is promising in predicting molecular and haematological relapse and guiding management. This paper summarises the existing literature regarding methods for detecting and monitoring disease response after HSCT in myelofibrosis and explores the therapeutic use of measurable residual disease (MRD) assays in transplant recipients. Laboratory assessment of disease response in myelofibrosis post-allogeneic transplant is limited by disease and treatment characteristics and by the sensitivity of available conventional molecular assays. The identification of MRD has prognostic implications and may allow early intervention to prevent relapse. Further applicability is limited by mutation-specific assay variability, a lack of standardisation and sample considerations.

Ultrasensitive chimerism enhances measurable residual disease testing after allogeneic hematopoietic cell transplantation

Increasing mixed chimerism (reemerging recipient cells) after allogeneic hematopoietic cell transplant (allo-HCT) can indicate relapse, the leading factor determining mortality in blood malignancies. Most clinical chimerism tests have limited sensitivity and are primarily designed to monitor engraftment. We developed a panel of quantitative polymerase chain reaction assays using TaqMan chemistry capable of quantifying chimerism in the order of 1 in a million. At such analytic sensitivity, we hypothesized that it could inform on relapse risk. As a proof-of-concept, we applied our panel to a retrospective cohort of patients with acute leukemia who underwent allo-HCT with known outcomes. Recipient cells in bone marrow aspirates (BMAs) remained detectable in 97.8% of tested samples. Absolute recipient chimerism proportions and rates at which these proportions increased in BMAs in the first 540 days after allo-HCT were associated with relapse. Detectable measurable residual disease (MRD) via flow cytometry in BMAs after allo-HCT showed limited correlation with relapse. This correlation noticeably strengthened when combined with increased recipient chimerism in BMAs, demonstrating the ability of our ultrasensitive chimerism assay to augment MRD data. Our technology reveals an underappreciated usefulness of clinical chimerism. Used side by side with MRD assays, it promises to improve identification of patients with the highest risk of disease reoccurrence for a chance of early intervention.

Validation of next-generation sequencing-based chimerism testing for accurate detection and monitoring of engraftment in hematopoietic stem cell transplantation

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is a life-saving treatment for various hematological disorders. The success of allo-HSCT depends on the engraftment of donor cells and the elimination of recipient cells monitored through chimerism testing. We aimed to validate a next-generation sequencing (NGS)-based chimerism assay for engraftment monitoring and to emphasize the importance of including the most prevalent cell subsets in proficiency testing (PT) programs. We evaluated the analytical performance of NGS-based chimerism testing (AlloSeq-HCT and CareDx) with a panel of targeted 202 informative single-nucleotide polymorphisms (SNPs) (i.e., linearity and precision, analytical sensitivity and specificity, system accuracy, and reproducibility). We further compared the performance of our NGS panel with conventional short tandem repeat (STR) analysis in unfractionated whole blood and cell-subset-enriched CD3 and CD66. Our NGS-based chimerism monitoring assay has an impressive detection limit (0.3% host DNA) for minor alleles and analytical specificity (99.9%). Pearson's correlation between NGS- and STR-based chimerism monitoring showed a linear relationship with a slope of 0.8 and r = 0.973. The concordance of allo-HSCT patients using unfractionated whole blood, CD3, and CD66 was 0.95, 0.96, and 0.54, respectively. Utilization of CD3+ cell subsets for mixed chimerism detection yielded an average of 7.3 ± 7-fold higher donor percentage detection compared to their corresponding unfractionated whole blood samples. The accuracy of the NGS assay achieved a concordance of 98.6% on blinded external quality control STR samples. The reproducibility series showed near 100% concordance with respect to inter-assay, inter-tech, inter-instrument, cell flow kits, and AlloSeq-HCT software versions. Our study provided robust validation of NGS-based chimerism testing for accurate detection and monitoring of engraftment in allo-HSCT patients. By incorporating the cell subsets (CD3 and CD66), the sensitivity and accuracy of engraftment monitoring are significantly improved, making them an essential component of any PT program. Furthermore, the implementation of NGS-based chimerism testing shows potential to streamline high-volume transplant services and improve clinical outcomes by enabling early relapse detection and guiding timely interventions.

Optimizing Donor Chimerism Threshold for Next Generation Sequencing Monitoring of Measurable Residual Disease Post-Allogeneic Stem Cell Transplant for Myeloid Neoplasms

BACKGROUND

Next-Generation Sequencing (NGS) is used to monitor genetically-measurable residual disease (gMRD) following allogeneic stem cell transplant (aSCT). It is unknown whether an upper limit of chimerism exists such that gMRD NGS testing can be safely forgone.

METHODS

We reviewed 61 AML and 24 MDS patients between 2016-2020 with at least 1 NGS panel before and after aSCT. Donor chimerism was quantified. Logistic regression characterized which factors predicted gMRD. Receiver operator curves (ROC) determined the optimal chimerism threshold for which gMRD would not be detected. Data from an additional 22 patients with follow-up NGS testing in 2022, was also analyzed to validate our proposed threshold.

RESULTS

Donor chimerism (OR= 0.38, 95% CI[0.10,0.62], p=0.02), as expected, was a significant predictor of gMRD. Age, gender, conditioning regimen, presence of a related donor, and diagnosis were not associated with gMRD. A chimerism threshold of 92.5% optimized sensitivity (97.7) and specificity (95.4) such that values >92.5% strongly predicted absence of gMRD (AUC= .986). The validation cohort demonstrated similar strongly predictive capability (AUC= .974) with appropriate sensitivity (100%) and specificity (90.9%).

CONCLUSION

NGS monitoring of gMRD is redundant at chimerism values greater than a more conservative threshold of 92.5% after stem cell transplant.

Incomplete chimerism following myeloablative and anti-thymocyte globulin-conditioned hematopoietic cell transplantation is a risk factor for relapse and chronic graft-versus-host disease

BACKGROUND AIMS

The value of routine chimerism determination after myeloablative hematopoietic cell transplantation (HCT) is unclear, particularly in the setting of anti-thymocyte globulin (ATG)-based graft-versus-host disease (GVHD) prophylaxis.

METHODS

Blood samples were collected at 3 months post-HCT from 558 patients who received myeloablative conditioning and ATG-based GVHD prophylaxis. Chimerism was assessed using multiplex polymerase chain reaction of short tandem repeats in sorted T cells (CD3+) and leukemia lineage cells (CD13+CD33+ for myeloid malignancies and CD19+ for B-lymphoid malignancies). ATG exposure was determined using a flow cytometry-based assay. The primary outcomes of interest were relapse and chronic GVHD (cGVHD).

RESULTS

Incomplete (<95%) T-cell chimerism and leukemia lineage chimerism were present in 17% and 4% of patients, respectively. Patients with incomplete T-cell chimerism had a significantly greater incidence of relapse (36% versus 22%, subhazard ratio [SHR] = 2.03, P = 0.001) and lower incidence of cGVHD (8% versus 25%, SHR = 0.29, P < 0.001) compared with patients with complete chimerism. In multivariate modeling, patients with high post-transplant ATG area under the curve and any cytomegalovirus (CMV) serostatus other than donor/recipient seropositivity (non-D+R+) had an increased likelihood of incomplete T-cell chimerism. Patients with incomplete leukemia lineage chimerism had a significantly greater incidence of relapse (50% versus 23%, SHR = 2.70, P = 0.011) and, surprisingly, a greater incidence of cGVHD (45% versus 20%, SHR = 2.64, P = 0.003).

CONCLUSIONS

High post-transplant ATG exposure and non-D+R+ CMV serostatus predispose patients to incomplete T-cell chimerism, which is associated with an increased risk of relapse. The increased risk of cGVHD with incomplete B-cell/myeloid chimerism is a novel finding that suggests an important role for recipient antigen-presenting cells in cGVHD pathogenesis.

Impact on outcomes of mixed chimerism of bone marrow CD34+ sorted cells after matched or haploidentical allogeneic stem cell transplantation for myeloid malignancies

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT), proposed to patients with high-risk myeloid malignancies, may ultimately fail because of disease relapse. Bone marrow (BM) CD34⁺ cells in Allo-HSCT recipients can be either re-emerging recipient malignant cells or donor cells attesting of hematopoietic reconstitution. In this context, investigating donor/recipient chimerism in the population of BM CD34⁺ sorted cells (BM-CD34⁺SC) was performed in 261 Allo-HSCT recipients (matched n = 145, haploidentical n = 65, matched unrelated n = 51) with myeloid malignancies. BM-CD34⁺SC chimerism was compared to that of whole peripheral blood (PB) cells as well as other Allo-HSCT-related parameters, and impact on relapse and survival was assessed. Thresholds of 98% donor cells for PB and 90% for BM-CD34⁺SC were found to allow relapse prediction. This was completed by the application of machine learning tools to explore the predictive value of these parameters in multidimensional models with repeated iterations. BM-CD34⁺SC mixed chimerism stood out with all these methods as the most robust predictor of relapse with a significant impact on disease-free and overall survivals even after haploidentical Allo-HSCT and/or PTCY administration. This marker therefore appears to be of great interest for the decision of preemptive treatment to avoid post-transplant relapse.

Living Donor Liver Transplantation for Hepatic Venoocclusive Disease/Sinusoidal Obstruction Syndrome Originating from Hematopoietic Stem Cell Transplantation

Background

Venoocclusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), is a life-threatening hematopoietic stem cell transplantation (HSCT) complication. Cases of mild and moderate VOD/SOS are self-limiting; however, the mortality for severe VOD/SOS has reached 80%. Recently, defibrotide became available and has been used for VOD/SOS; however, the outcome for patients with severe VOD/SOS is not satisfactory, and liver transplantation is attempted in these severe cases.

Method

We describe a case of living donor liver transplantation (LDLT) for acute liver failure secondary to VOD/SOS that originates from HSCT.

Result

Liver regeneration after LDLT was impaired, and several infections were developed before liver regeneration completion. Our patient suffered sepsis and finally died of multiorgan failure.

Conclusion

Severe VOD/SOS originating from HSCT is associated with a very poor prognosis. The liver transplantation outcome for VOD/SOS has not been satisfied, but it may provide long-term survival if successful. We considered liver transplantation as a therapeutic option, especially in cases where sufficient graft volume is secured, considering impaired liver regeneration under bone marrow suppression after HSCT.

The Interaction of HLA-C1/KIR2DL2/L3 Promoted KIR2DL2/L3 Single-Positive/NKG2C-Positive Natural Killer Cell Reconstitution, Raising the Incidence of aGVHD after Hematopoietic Stem Cell Transplantation

NKG2C+ natural killer (NK) cell plays a vital role in CMV infection control after hematopoietic stem cell transplantation (HSCT). However, the modulation on NKG2C+ NK cell reconstitution is still unclear. NK cell education is affected by the interactions of HLA-I/killer immunoglobulin receptor (KIR). Our aim is to figure out which HLA-I/KIR interaction plays a dominant role in NKG2C+ NK education. Based on allogeneic haploidentical HSCT, we investigated the expansion and function of single KIR positive NKG2C+ NK cells via the interaction of KIR with both donor HLA and recipient HLA at days 30, 90, and 180 after HSCT. KIR2DL2/L3 single-positive/NKG2C⁺ cells were significantly expanded compared with KIR2DL1 or KIR3DL1 single-positive/NKG2C⁺ cells when donors and recipients were both HLA-C1/C1 or HLA-C1C1BW4 (p < 0.05), with higher NKp30 expression (p < 0.05). Moreover, the proportion of single KIR positive NK cells increased in both NKG2C⁺/NKG2A^- NK cells and conventional NKG2C^-/NKG2A^- NK cells over time. We also observed that increased proportion of KIR2DL2/L3 single-positive/NKG2C⁺ NK cells correlated with higher incidence of acute graft-versus-host disease (aGVHD). Our study allows a better understanding of HLA-I/KIR interaction in the NKG2C+ NK cell education after HSCT.

Analysis of Subset Chimerism for MRD-Detection and Pre-Emptive Treatment in AML

Allogeneic hematopoietic stem cell transplantation (alloHCT) represents the only potentially curative treatment in high-risk AML patients, but up to 40% of patients suffer from relapse after alloHCT. Treatment of overt relapse poses a major therapeutic challenge and long-term disease control is achieved only in a minority of patients. In order to avoid post-allograft relapse, maintenance as well as pre-emptive therapy strategies based on MRD-detection have been used. A prerequisite for the implementation of pre-emptive therapy is the accurate identification of patients at risk for imminent relapse. Detection of measurable residual disease (MRD) represents an effective tool for early relapse prediction in the post-transplant setting. However, using established MRD methods such as multicolor flow cytometry or quantitative PCR, sensitive MRD monitoring is only applicable in about half of the patients with AML and advanced MDS undergoing alloHCT. Donor chimerism analysis, in particular when performed on enriched leukemic stem and progenitor cells, e.g. CD34+ cells, is a sensitive method and has emerged as an alternative option in the post alloHCT setting. In this review, we will focus on the current strategies for lineage specific chimerism analysis, results of pre-emptive treatment using this technology as well as future developments in this field.

Chimerism analysis for clinicians: a review of the literature and worldwide practices

This review highlights literature pertinent to chimerism analysis in the context of hematopoietic cell transplantation (HCT). We also conducted a survey of testing practices of program members of CIBMTR worldwide. Questions included testing methods, time points, specimen type, cell lineage tested and testing indications. Recent literature suggests that detection of low level mixed chimerism has a clinical utility in predicting relapse. There is also increasing recognition of HLA loss relapse to potentially guide rescue decisions in cases of relapse. These developments coincide with wider access to high sensitivity next generation sequencing (NGS) in clinical laboratories. Our survey revealed a heterogeneity in practices as well as in findings and conclusions of published studies. Although the most commonly used method is STR, studies support more sensitive methods such as NGS, especially for predicting relapse. There is no conclusive evidence to support testing chimerism in BM over PB, particularly when using a high sensitivity testing method. Periodic monitoring of chimerism especially in diagnoses with a high risk of relapse is advantageous. Lineage specific chimerism is more sensitive than whole blood in predicting impending relapse. Further studies that critically assess how to utilize chimerism testing results will inform evidence based clinical management decisions.

Donor NKG2C homozygosity contributes to CMV clearance after haploidentical transplantation

Cytomegalovirus (CMV) infection remains an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Several investigators have reported that adaptive NKG2C+ NK cells persistently expand during CMV reactivation. In our study, two cohorts were enrolled to explored the relationships among the NKG2C genotype, NKG2C+ NK cell reconstitution, and CMV infection. Multivariate analysis showed that donor NKG2C gene deletion was an independent prognostic factor for CMV reactivation and refractory CMV reactivation. Furthermore, the quantitative, qualitative reconstitution and anti-CMV function of adaptive NKG2C+ NK cells after transplantation was significantly lower in patients grafted with NKG2Cwt/del donor cells than in those grafted with NKG2Cwt/wt donor cells. The quantitative reconstitution of NKG2C+ NK cells at day 30 after transplantation was significantly lower in patients with treatment-refractory CMV reactivation than in those in the no-CMV-reactivation and CMV-reactivation groups. In humanized CMV-infected mice, we found that compared with those from NKG2Cwt/del donors, adaptive NKG2C+ NK cells from NKG2Cwt/wt donors induced earlier and stronger expansion of NKG2C+ NK cells and earlier and stronger CMV clearance in vivo. In conclusion, donor NKG2C homozygosity contributes to CMV clearance by promoting the quantitative and qualitative reconstruction of adaptive NKG2C+ NK cells after haploidentical allo-HSCT.

Donor Chimerism Study by Single Nucleotide Polymorphism using SYBR green based Real Time PCR

Objective:

To optimize and evaluate a real time PCR of Single Nucleotide Polymorphism by SYBR Green method for detection of donor chimerism after haematopoietic stem cell transplantation.

Methods:

This descriptive study was conducted at Genetic Resource Centre (GRC) Lab Rawalpindi from Oct 2017 - Dec 2019. A total of twenty patients of post haematopoietic stem cell transplant with various haematological disorders were studied to see the status of donor chimerism by using SNP real time PCR using SYBR Green method and short tandem repeat PCR. These patients had undergone allogeneic HSCT from HLA-matched sibling donors at Pakistan Institute of Medical Science and Armed Forces Bone Marrow Transplant Centre.

Results:

Real time PCR using SYBR Green was able to detect significant amount of chimerism in all 20 patients having undergone HSCT. Regarding precision of the real time PCR assay the mean value of donor chimerism was 94.1% (SD 3.96) and by STR PCR it was 95.1% (SD 1.41). The assay was found to be sensitive with a detection limit of <1%.

Conclusion:

Our results demonstrate that SNP analysis by SYBR Green real time PCR may be used for the evaluation of chimerism status in patients having undergone HSCT with a sensitivity of <1%. Hence donor chimerism by this sensitive method can be used in monitoring of chimerism in post-transplant patients with various haematological disorders.

Intensive monitoring of minimal residual disease and chimerism after allogeneic hematopoietic stem cell transplantation for acute leukemia in children

Posttransplant leukemia detection before overt relapse is key to the success of immunotherapeutic interventions, as they are more efficient when leukemia burden is low. However, optimal schedule and monitoring methods are not well defined. We report the intensive bone marrow monitoring of minimal residual disease (MRD) using flow cytometry (FC) and nested reverse transcription polymerase chain reaction (RT-PCR) whenever a fusion transcript allowed it and chimerism by PCR at 11 timepoints in the first 2 years after transplant. Seventy-one transplants were performed in 59 consecutive children, for acute myeloid (n = 38), lymphoid (n = 31), or mixed-phenotype (n = 2) leukemia. MRD was monitored in 62 cases using FC (n = 58) and/or RT-PCR (n = 35). Sixty-seven percent of leukemia recurrences were detected before overt relapse, with a detection rate of 89% by RT-PCR and 40% by FC alone. Increased mixed chimerism was never the first evidence of recurrence. Two patients monitored by RT-PCR relapsed without previous MRD detection, one after missed scheduled evaluation and the other 4.7 years post transplant. Among the 22 cases with MRD detection without overt relapse, 19 received therapeutic interventions. Eight (42%) never relapsed. In conclusion, intensive marrow monitoring by RT-PCR effectively allows for early detection of posttransplant leukemia recurrence.

A practical guide to chimerism analysis: Review of the literature and testing practices worldwide

BACKGROUND AND PURPOSE

Currently there are no widely accepted guidelines for chimerism analysis testing in hematopoietic cell transplantation (HCT) patients. The objective of this review is to provide a practical guide to address key aspects of performing and utilizing chimerism testing results. In developing this guide, we conducted a survey of testing practices among laboratories that are accredited for performing engraftment monitoring/chimerism analysis by either the American Society for Histocompatibility & Immunogenetics (ASHI) and/or the European Federation of Immunogenetics (EFI). We interpreted the survey results in the light of pertinent literature as well as the experience in the laboratories of the authors.

RECENT DEVELOPMENTS

In recent years there has been significant advances in high throughput molecular methods such as next generation sequencing (NGS) as well as growing access to these technologies in histocompatibility and immunogenetics laboratories. These methods have the potential to improve the performance of chimerism testing in terms of sensitivity, availability of informative genetic markers that distinguish donors from recipients as well as cost.

SUMMARY

The results of the survey revealed a great deal of heterogeneity in chimerism testing practices among participating laboratories. The most consistent response indicated monitoring of engraftment within the first 30 days. These responses are reflective of published literature. Additional clinical indications included early detection of impending relapse as well as identification of cases of HLA-loss relapse.

How I treat measurable (minimal) residual disease in acute leukemia after allogeneic hematopoietic cell transplantation

Although allogeneic hematopoietic cell transplantation (allo-HCT) is currently the standard curative treatment of acute leukemia, relapse remains unacceptably high. Measurable (minimal) residual disease (MRD) after allo-HCT may be used as a predictor of impending relapse and should be part of routine follow-up for transplanted patients. Patients with MRD may respond to therapies aiming to unleash or enhance the graft-versus-leukemia effect. However, evidence-based recommendations on how to best implement MRD testing and MRD-directed therapy after allo-HCT are lacking. Here, I describe our institutional approach to MRD monitoring for preemptive MRD-triggered intervention, using patient scenarios to illustrate the discussion.

Donor and host coexpressing KIR ligands promote NK education after allogeneic hematopoietic stem cell transplantation

The rate and extent of natural killer (NK)-cell education after hematopoietic cell transplantation correlates with leukemia control. To study the effect of donor and host HLA on NK-cell reconstitution, single killer-cell immunoglobulin-like receptor (KIR)+ NK cells (exhibiting KIR2DL1, KIR2DL2/KIR2DL3, or KIR3DL1 as their sole receptor) were grouped into 4 groups based on the interaction between donor/host HLA and donor inhibitory KIR in 2 cohorts (n = 114 and n = 276, respectively). On days 90 to 180 after transplantation, the absolute number and responsiveness against K562 cells (CD107a or interferon-γ expression) of single-KIR+ NK cells were higher in pairs where donor and host HLA both expressed ligands for donor inhibitory KIRs than in pairs where 1 or both of the donor and recipient HLA lacked at least 1 KIR ligand. NK-cell responsiveness was tuned commensurate with the number of inhibitory receptors from the donor. When both donor and host expressed the 3 major KIR ligands (HLA-C1, HLA-C2, and HLA-Bw4), NK cells expressing 3 inhibitory receptors (KIR2DL1/2DL3/3DL1) reached the maximum responsiveness against K562 cells compared with those NK cells expressing only 1 or 2 inhibitory receptors. When donor and host HLA both expressed all ligands for donor inhibitory KIRs, patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) showed the lowest recurrence rate after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). In conclusion, this study demonstrates that when both donors and hosts present all the KIR ligands for donor KIRs, reconstituted NK cells achieve better functional education and contribute to least relapse among patients. This observation study was registered at www.clinicaltrials.gov as #NCT02978274.

Expanded clinical-grade membrane-bound IL-21/4-1BBL NK cell products exhibit activity against acute myeloid leukemia in vivo

BACKGROUND

Adoptive NK cell infusion is a promising immunotherapy for acute myeloid leukemia (AML) patients. The aim of this study was to test the activity of clinical-grade membrane-bound IL-21/4-1BBL-expanded NK cell products against AML in vivo.

METHODS

Fresh peripheral blood mononuclear cells (PBMCs) were incubated with equal numbers of irradiated membrane-bound IL-21/4-1BBL-expressing K562 cells for 2-3 weeks to induce clinical-grade NK cell expansion.

RESULTS

Expansion for 2 and 3 weeks produced ∼4 and 8 × 10⁹ NK cells from 2 × 10⁷ PBMCs. The production of CD107a and TNF-α in NK cell products in response to AML cell lines and primary blasts was higher than that observed in resting NK cells. The 2-week expanded NK cell products were xenografted into immunodeficient mice with leukemia and were persistently found in the BM, spleen, liver, lung, and peripheral blood for at least 13 days; furthermore, these expanded products reduced the AML burden in vivo. Compared with matched AML patients with persistent or relapsed minimal residual disease (MRD⁺ ) who underwent regular consolidation therapy, MRD⁺ patients who underwent NK treatment had better overall survival and showed no major adverse events.

CONCLUSIONS

Clinical-grade mbIL-21/4-1BBL-expanded NK cells exhibited antileukemic activity against AML in vitro and in vivo.

Impact of early chimerism status on clinical outcome in children with acute lymphoblastic leukaemia after haematopoietic stem cell transplantation

Background

The significance of very early chimerism assessment before day + 28, which is considered the moment of engraftment, is still unclear. In this retrospective study, we evaluated the clinical impact of very early chimerism on the clinical outcome after allogeneic haematopoietic stem cell transplantation (allo-HSCT) in children with acute lymphoblastic leukaemia (ALL).

Methods

The study group included 38 boys and 18 girls. Very early chimerism was evaluated on days + 7, + 14, + 21 and + 28 after the transplant. Short tandem repeat polymerase chain reaction (STR PCR) was used to analyse chimerism.

Results

Overall survival (OS) and event-free survival (EFS) were 84 and 80%, respectively. The OS in the group of 24 patients with complete donor chimerism on day + 14 was 83%, and it did not differ statistically compared to the 32 patients with mixed chimerism on day + 14 (OS was 84%). In our cohort of patients, the matched unrelated donor, male gender of donor, number of transplanted cells above 4.47 × 10⁶ kg and no serotherapy with anti-thymocyte globulin (ATG) were statistically related to a higher level of donor chimerism. The immunophenotypes of disease, age of patient at time HSCT, recipient sex, stem cell source (peripheral blood/bone marrow) and conditioning regimen had no impact on early chimerism. Acute graft versus host disease grades II-IV was diagnosed in 23 patients who presented with donor chimerism levels above 60% on day 7.

Conclusions

The data presented in this study provide valuable insight into the analysis of very early chimerism in children with ALL treated with HSCT.

Quantitative chimerism in CD3-negative mononuclear cells predicts prognosis in acute myeloid leukemia patients after hematopoietic stem cell transplantation

Relapse is a major complication of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (SCT). The objective of our study was to evaluate chimerism monitoring on the CD3-negative mononuclear cells by RQ-PCR to predict relapse of patients allografted for AML and to compare its performance with WT1 quantification. A cohort of 100 patients undergoing allogenic SCT for AML was retrospectively analyzed in a single institution. Patients without complete chimerism, defined as less than 0.01% of recipient's DNA in CD3-negative cells, had a significantly higher risk of relapse and a lower overall survival (p < 0.001). An increase in the percentage of recipient DNA in CD3-negative cells was associated with an increased risk of relapse (p < 0.001) but not with overall survival. Comparable performances between monitoring of CD3-negative cell chimerism and WT1 expression to predict relapse was observed up to more than 90 days before hematological relapse, with sensitivity of 82% and 78%, respectively, and specificity of 100% for both approaches. Quantitative specific chimerism of the CD3-negative mononuclear fraction, enriched in blastic cells, is a new and powerful tool for monitoring measurable residual disease and could be used for AML patients without available molecular markers.

Highly sensitive chimerism detection in blood is associated with increased risk of relapse after allogeneic hematopoietic cell transplantation in childhood leukemia

Analysis of chimerism in blood post-HCT using STR-PCR is routinely applied in parallel with quantification of MRD to predict relapse of leukemia. RQ-PCR chimerism is 10- to 100-fold more sensitive, but clinical studies in children are sparse. We analyzed IMC in blood samples following transplantation for acute lymphoblastic or myeloid leukemia in 56 children. IMC was defined as a minimum increase of (a) 0.1% or (b) 0.05% recipient DNA between two samples. The risk of relapse was higher in children with IMC of both 0.1% and 0.05% compared to children without IMC (HR 12.8 [95% CI: 3.9-41.4; P < .0001] and 7.6 [95% CI: 2.2-26.9; P < .01], respectively). The first IMC was detected at a median of 208 days prior to relapse. The 5-year cumulative incidence of relapse for children with a single IMC was 45.5% (CI 12.3-74.4) and 41.0% (14.2-66.6) for IMC above 0.1% and 0.05%, respectively. However, in 47 and 38 children never attaining IMC > 0.1% and >0.05%, 10 and 8 children relapsed, respectively. In a landmark analysis, no association was found between IMC prior to 90 days post-HCT and subsequent relapse by either classification of IMC and AUC for RQ-PCR chimerism was 54.2% (95 CI 27.7- 84.8). Although limited by a retrospective design, these results indicate that monitoring of RQ-PCR chimerism in peripheral blood may have a role in early detection of relapse in acute childhood leukemia.

Current Trends in Applications of Circulatory Microchimerism Detection in Transplantation

Primarily due to recent advances of detection techniques, microchimerism (the proportion of minor variant population is below 1%) has recently gained increasing attention in the field of transplantation. Availability of polymorphic markers, such as deletion insertion or single nucleotide polymorphisms along with a vast array of high sensitivity detection techniques, allow the accurate detection of small quantities of donor- or recipient-related materials. This diagnostic information can improve monitoring of allograft injuries in solid organ transplantations (SOT) as well as facilitate early detection of relapse in allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the present review, genetic marker and detection platform options applicable for microchimerism detection are discussed. Furthermore, current results of relevant clinical studies in the context of microchimerism and SOT or allo-HSCT respectively are also summarized.

The consensus on the monitoring, treatment, and prevention of leukemia relapse after allogeneic hematopoietic stem cell transplantation in China

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important curative therapy for patients with leukemia. However, relapse remains the leading cause of death after transplantation. In recent years, substantial progress has been made by Chinese physicians in the field of establishment of novel transplant modality, patient selection, minimal residual disease (MRD) monitoring, and immunological therapies, such as modified donor lymphocyte infusion (DLI) and chimeric antigen receptor T (CART) cells, as well as MRD-directed intervention for relapse. Most of these unique systems are distinct from those in the Western world. In this consensus, we reviewed the efficacy of post-HSCT relapse management practice from available Chinese studies on behalf of the HSCT workgroup of the Chinese Society of Hematology, Chinese Medical Association, and compared these studies withthe consensus or guidelines outside China. We summarized the consensus on routine practices of post-HSCT relapse management in China and focused on the recommendations of MRD monitoring, risk stratification directed strategies, and modified DLI system. This consensus will likely contribute to the standardization of post-HSCT relapse management in China and become an inspiration for further international cooperation to refine global practices.

Donor-Specific Anti-Human Leukocyte Antigen Antibodies Predict Prolonged Isolated Thrombocytopenia and Inferior Outcomes of Haploidentical Hematopoietic Stem Cell Transplantation

Prolonged isolated thrombocytopenia (PT) after allogeneic stem cell transplantation (allo-SCT) has a great impact on transplant outcome. In this study, we performed a retrospective analysis to investigate the association of donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) with PT in 394 patients who underwent unmanipulated haploidentical blood and marrow transplantation (HBMT). For HLA antibody positive samples with a median fluorescent intensity (MFI) > 500, DSAs were further examined. A total of 390 patients (99.0%) achieved sustained myeloid engraftment. Of the 394 cases tested, 45 (11.4%) were DSA positive. The cumulative incidence of PT in this cohort of patients was 9.9 ± 1.5%. The incidence of PT was higher in patients with a MFI ≥ 1000 compared with those with a MFI < 1000 (16.8 ± 6.4% versus 7.4 ± 1.4%, P = 0.05). Multivariate analysis showed that the presence of DSAs (MFI ≥ 1000) was correlated to PT (hazard ratio (HR) 3.262; 95% confidence interval (CI), 1.339-7.946; P = 0.009) and transplant-related mortality (HR 2.320; 95% CI, 1.169-4.426; P = 0.044). Our results, for the first time, suggest an association of DSAs with PT after unmanipulated HBMT. It would help screen out the suitable donor and guide intervention. This indicated that DSAs should be incorporated in the algorithm for unmanipulated HBMT.

Allogeneic Hematopoietic Cell Transplantation in Multiple Myeloma: Focus on Longitudinal Assessment of Donor Chimerism, Extramedullary Disease, and High-Risk Cytogenetic Features

Although generally not applied as first-line treatment of multiple myeloma, allogeneic hematopoietic cell transplantation (allo-SCT) can still be chosen as ultimate escalation approach in high-risk patients, preferentially within the framework of clinical trials. In this study, we investigated whether decreasing donor chimerism (DC) is predictive for relapse. In addition, we comprehensively determined the impact of several other disease- and treatment-related factors on outcome. One hundred fifty-five multiple myeloma patients whose DC status was followed serially by the short tandem repeat-based techniques at a single lab were included in this retrospective study. Outcome variables were studied in univariate and multivariable analyses. Available were 2.324 DC samples (median, 12 per patient). Loss of full DC was associated with shorter progression-free survival (PFS) (HR, 1.7; 95% CI, 1.1 to 2.6) but did not impact overall survival. Two-thirds of patients with International Myeloma Working Group-defined relapses still displayed a full DC in peripheral blood or bone marrow. Extramedullary manifestations were observed in 33% of patients, accounting for the discrepancy between DC analysis and the actual disease status. In multivariable analysis, the 2 most relevant variables for an unfavorable PFS were progressive disease before allo-SCT (HR, 3.0; 95% CI, 1.5 to 5.9) and allo-SCT at least the second relapse (HR, 2.8; 95% CI, 1.5 to 4.9), whereas for overall survival progressive disease or partial response before allo-SCT had the strongest negative effects (HR, 4.2; 95% CI, 1.9 to 9, and HR, 2.0; 95% CI, 1.0 to 3.8, respectively). Adverse cytogenetics such as del17p, t(4,14) or amp(1q21) were not associated with shorter survival after allo-SCT. Extensive DC sampling beyond robust engraftment does not appear to provide additional information helpful for disease management in most patients and is challenged by a significant incidence of extramedullary disease. In our series, allo-SCT overcame unfavorable cytogenetics.

CTLA-4 polymorphisms and haplotype correlate with survival in ALL after allogeneic stem cell transplantation from related HLA-haplotype-mismatched donor

Background

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been established as an effective treatment for patients with hematological malignancies. Disease relapse remains a major cause of transplant failure. T cell homeostasis is critical to determine the potency of the GVT effect. Recent studies have shown the association of the CTLA-4 polymorphisms with the outcome after HLA-identical sibling allogeneic HSCT.

Methods

In this study, we focused on four CTLA-4 polymorphisms, and analyzed the impact of donor genotypes and haplotypes on the conditions of 152 acute leukemia patients (ALL 83) after related HLA-haplotype- mismatched transplantation. The four SNP genotypes (−1661, −318, CT60 and +49) were determined by TaqMan SNP genotyping assays.

Results

ALL recipients of donors with +49 GG showed significantly lower OS (67.7 vs. 90.3 %, P = 0.015) than those with GA+AA. Multivariate analyses showed that +49 GG was an independent risk factor for OS (HR: 0.306, 95 % CI 0.111–0.842, P = 0.022) .23 ALL patients receiving mDLI showed significantly lower OS with +49 GG donor than those with GA+AA (30.0 vs. 83.1 %, P = 0.003). The haplotype analysis revealed only three haplotypes in the donor population −1661/−318/CT60/+49 i.e., ACGG, ACAA and GTGA, the frequencies were 64.1, 19.4 and 16.5 %, respectively. Donors with and without the ACGG/ACGG haplotype had the same effect on transplant outcomes as those with +49 GG and +49 GA+AA.

Conclusion

In summary, the CTLA-4 +49 GG and the haplotype ACGG/ACGG reduced the overall survival in ALL after allo-HSCT from the related HLA-haplotype-mismatched donor, knowledge of the CTLA-4 polymorphism and haplotype may provide useful information for donor selection and individual application of immunosuppressive agents and immunotherapy.

Reduced-intensity conditioning with fludarabine and busulfan for allogeneic hematopoietic cell transplantation in elderly or infirm patients with advanced myeloid malignancies

We report a retrospective single-center analysis of 112 consecutive patients that underwent allogeneic hematopoietic cell transplantation (HCT) after reduced-intensity conditioning (RIC) with fludarabine (FLU) and busulfan (BU) for the treatment of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and myeloproliferative syndrome (MPS) from 2005 to 2014. Three-year event-free survival (EFS) and overall survival (OS) were 46 and 58 %, respectively. Patients ≥60 years of age showed a similar outcome compared to younger patients (3-year OS 55 vs. 61 %, p = 0.96; 3-year EFS 46 vs. 46 %, p = 0.82). Cumulative incidence of non-relapse mortality (NRM) at 3 years adjusted for relapse as competing risk was 25 % for patients aged <60 years and 15 % for older patients (p = 0.15). Infusions of higher CD34(+) blood stem cell doses were associated with a significantly better outcome in the elderly subgroup (3-year OS 82 vs. 39 %, p = 0.007). Moreover, complete donor chimerism at day +100 was associated with a significantly improved survival (3-year OS 69 vs. 23 %, p = 0.003). In conclusion, our data suggest that RIC with FLU/BU enables long-term disease-free survival even in an elderly patient population. Age has no negative impact on the outcome of allogeneic HCT, and decision for transplant should be based on disease risk and performance status rather than age alone.