Real-time quantitative Y chromosome-specific PCR (QYCS-PCR) for monitoring hematopoietic chimerism after sex-mismatched allogeneic stem cell transplantation

The mythological chimera and new era of relapse prediction post-transplant

Allogeneic hemopoietic stem cell transplantation is the treatment of choice for high-risk or relapsed acute leukemia. However, unfortunately, relapse post-transplant continues to be the most common cause of treatment failure with 20-80% of patients relapsing based on disease risk and status at transplant. Advances in molecular profiling of different hematological malignancies have enabled us to monitor low level disease before and after transplant and develop a more personalized approach to the management of these disease including early detection post-transplant. While, in general, detectable disease by morphology remains the gold standard to diagnosing relapse, multiple approaches have allowed detection of cancer cells earlier, using peripheral blood-based methods with sensitivities as high as 1:10⁶, together called minimal/measurable residual disease (MRD) detection. However, a in significant number of patients with acute leukemia where no such molecular markers exist it remains challenging to detect early relapse. In such patients who receive transplantation, chimerism monitoring remains the only option. An increase in mixed chimerism in post allogeneic HCT patients has been correlated with relapse in multiple studies. However, chimerism monitoring, while commonly accepted as a tool for assessing engraftment, has not been routinely used for relapse detection, at least in part because of the lack of standardized, high sensitivity, reliable methods for chimerism detection. In this paper, we review the various methods employed for MRD and chimerism detection post-transplant and discuss future trends in MRD and chimerism monitoring from the viewpoint of the practicing transplant physician.

Influence of Fetomaternal Microchimerism on Maternal NK Cell Reactivity against the Child’s Leukemic Blasts

Persistence of fetal cells in the circulation of the mother (fetal microchimerism, FM) is associated with increased survival and reduced relapse of children with leukemia receiving a haploidentical hematopoietic stem cell transplantation (hHSCT). NK cells play an important role in maternal tolerance towards the unborn child. In this study, 70 mother–child pairs were prospectively analyzed for the occurrence of FM, KIR genotype and HLA-C type. We found that occurrence and level of FM were influenced by three maternal genetic factors: presence of an HLA-C1 allele, absence of KIR2DL3 and presence of a cen-B/B motif. Furthermore, an HLA-C match between mother and child favored persistence of FM. NK cells from FM⁺ mothers showed a 40% higher specific degranulation against their filial leukemic blasts than NK cells from FM⁻ mothers, suggesting the presence of educated maternal NK cells. Nevertheless, cytotoxicity of parental NK cells against filial leukemic blasts was independent of KIR genetics (haplotype, B content score, centromeric and telomeric KIR gene regions) and independent of FM, indicating that additional immune effector mechanisms contribute to the beneficial effect of persisting FM in hHSCT.

Risk factors for outcome after allogeneic stem cell transplantation in patients with advanced phase CML

Allogeneic hematopoietic stem-cell transplantation (HSCT) remains the only curative option for patients with advanced chronic myeloid leukemia (CML). However, outcome is dismal and of short follow-up. The objective of the study was to determine long-term outcome and risk factors in patients with a history of CML Blast Crisis (BC; n = 96) or accelerated phase (n = 51) transplanted between 1990 and 2018. At transplant, patients had a median age of 39 (range 7–76) years and were in ≥CP2 (n = 70), in AP (n = 40) or in BC (n = 37) with a diagnosis-HSCT interval of median 1.9 (range 0.3–24.4) years. Overall survival (OS) amounted 34% (95% CI 22–46) and progression-free survival (PFS) 26% (95% CI 16-36) at 15 years. Adverse risk factors for OS and PFS were low CD34⁺ count in the graft, donor age (>36 years) and BC. Cumulative incidence of Non-Relapse Mortality (NRM) was 28% (95% CI 18–38) and of relapse (RI) 43% (95% CI 33–53) at 15 years. PB-HSCT and HSCT after 2008 were favorable prognostic factors for NRM, while family donor and patient age >39 years were independently associated with higher RI. HSCT resulted in long-term OS in patients with advanced CML. OS was improved in non-BC patients, with donors ≤36 years and with higher CD34⁺ dose in the graft.

Chimeric status of biological samples after HSCT for personal identification: Y-STR based DNA analysis in sex mismatch cases

Identification of an individual is the prime object in forensic case works both in civil or criminal situations like paternity/maternity disputes, sexual assaults, murder, mass disaster victims etc. STR analysis has already proved its potential to give accurate results. In addition to autosomal chromosomes, sex determination at many times is crucial in forensic situations, especially in situations like rape cases or in cases of missing persons. The chances of wrong interpretations may arise due to false detection (or non-detection) of STR fragments overall or only at amelogenin-specific fragments, in situation like mutations, intersex conditions, trans-sexualism etc., due to natural or artificial chimersim. The forensic relevance of the possible misinterpretation of STR's or amelogenin should never be underestimated. The present study was carried out to identify an individual using Y-STR in sex mismatch patients who received hematopoietic stem cell transplantation. Hematopoietic stem cell transplantation is a method to replace patient's stem cell with the stem cell donated by the donor preferably biological related in order to cure malignant and non malignant diseases. This study enrolled ten female patients of HSCT. Samples were collected as pre and post transplant after 15 days, 30 days, 60 days, and 90 days of time interval from sex mismatch patient (female) and from donor (male) and chimeric status of the patient was analyzed using Y-STR markers (23 loci). Results demonstrated that donor genotype existed in blood and buccal swab of the recipient but no genetic profile existed for Y-STR in hair follicle of the recipient. This study suggests that only hair follicle out of three biological samples tested serves as reliable source of recipient's origin after HSCT for accurate personal identification especially in forensic situations.

Accurate In-Vivo Quantification of CD19 CAR-T Cells after Treatment with Axicabtagene Ciloleucel (Axi-Cel) and Tisagenlecleucel (Tisa-Cel) Using Digital PCR

Immunotherapy with CD19-specific chimeric antigen receptor (CAR-) T cells has shown excellent efficacy in relapsed/refractory B-cell cancers. The in vivo expansion and persistence of CAR-T cells after infusion are important response- and toxicity-determining variables, but diagnostic tools are largely missing. We showed previously for axi-cel that digital PCR (dPCR) is excellently suited to monitoring CAR-T cells in vivo. Here, we aimed to develop an analogous dPCR assay for tisa-cel. To do so, we cloned and sequenced the CAR construct from the lentiviral tisa-cel vector and designed primers and Black hole quencher (BHQ) probes complimentary to sequences present in the FMC63 scFv part of axi-cel (assay A), tisa-cel (T), and both constructs (U = “universal”). In conjunction with excellent specificity, all assays have a detection limit of one single CAR copy, corresponding to a sensitivity of approximately 1 in 5000 cells (0.02%) for 100 ng genomic DNA (for one vector copy per transduced cell). The new universal assay was first validated using patient samples previously quantified with the axi-cel-specific dPCR and thereafter applied to quantify and monitor adoptively transferred axi-cel and tisa-cel T cells in post-infusion samples (peripheral blood, bone marrow, liquor, and ascites). Actual CAR-T counts per µl were calculated, taking into account vector copy and peripheral blood mononuclear cell (PBMC) numbers, and showed very good correlation with flow cytometry results. We conclude that our novel dPCR assay is optimally suited to monitoring tisa-cel and axi-cel CAR-T cells in real-time in various body fluids.

Digital PCR Assays for Precise Quantification of CD19-CAR-T Cells after Treatment with Axicabtagene Ciloleucel

Treatment with axicabtagene ciloleucel (Axi-cel) CD19-CAR-T (chimeric antigen receptor T) cells has been approved for refractory/relapsed diffuse large B cell lymphoma (DLBCL) and primary mediastinal large B cell lymphoma (PMBCL). Because treatment success as well as side effects might depend on CAR-T cell expansion in vivo, we aimed at developing digital PCR (dPCR) assays for detection and quantification of CAR-T cells. To this end, we cloned and sequenced the complete cDNA of the CAR construct. We designed different combinations of primers and dual-labeled hydrolysis probes located in various CAR regions. Three combinations were successfully tested on CAR-positive and -negative cells in duplex reactions with a reference gene (REF) to concomitantly assess cell numbers. All assays demonstrated excellent specificity and reproducibility with neglectable inter-assay variations. For all three assays, almost perfect correlation between the two dPCRs (Axi-cel versus REF) was observed, and the limit of detection was one single CAR-transduced cell corresponding to a sensitivity of 0.01% for 100 ng genomic DNA. After cross-validation, we used one assay to monitor Axi-cel CAR-T numbers in patients. CAR-T expansion and contraction followed the expected kinetics with median peak value of 11.2 Axi-cel CAR-T cells/μL at 11.3 days (median). Clinically, we observed only two partial responses (PRs) in the five patients with CAR-T cell peak numbers below median, whereas four of the five patients with comparatively good expansion showed clinical responses (two complete responses [CRs] and two PRs) on day 30. In conclusion, we established a novel dPCR assay for the sensitive detection of transgenic CAR-T cells, which should be very useful in the context of Axi-cel treatment.

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.

Personalized Chimerism Test that Uses Selection of Short Tandem Repeat or Quantitative PCR Depending on Patient's Chimerism Status

Chimerism testing is used to monitor engraftment and risk of relapse after allogeneic hematopoietic stem cell transplantation for hematologic malignancies. Although short tandem repeat (STR) method is widely used among clinical laboratories, quantitative PCR (qPCR) provides better sensitivity (0.1%) than STR (1% to 5%) but is less accurate than STR for patients in mixed chimerism. qPCR chimerism allows evaluation of residual recipient cells as a surrogate of measurable residual disease. To achieve higher sensitivity and accuracy, we applied qPCR or STR based on patient chimerism status (recipient alleles <5% or ≥5%, respectively). Of the 230 patients tested by STR in a 1-year period, excluding 10 deceased patients, 30 qPCR markers were genotyped and 167 patients converted to qPCR chimerism (76%), including eight patients undergoing multiple-donor transplantation. STR was continued on 53 patients (24%) for the following reasons: mixed chimerism (n = 23), lack of donor or pretransplantation DNA (n = 22), and insufficient qPCR informative markers [8 of 60 patients with related donors (13.3%)]. qPCR detected residual recipient chimerism in 85.5% of patients with complete chimerism by STR (<5% recipient). Selecting STR or qPCR testing based on each patient's chimerism status facilitates sensitive and accurate chimerism testing in clinical settings. In addition, we discuss clinical relevance of chimerism testing for measurable residual disease detection in various hematologic malignancies.

[Donor chimerism and minimal residual disease monitoring in leukemia patients after allo-HSCT]

In present research the comparative analysis of donor chimerism (DC) using different tests was performed to improve the diagnostic tool in patients with malignant hematological disorders after allo-HSCT. The RBC antigen typing, identification of ABO blood type and quantitative analysis of InDel-, STR-, Y-polymorphisms were carried out for detection of DC. In addition, the expression of well-known oncogenes and CD-markers for monitoring MRD was evaluated to predict relapse and clinical outcome. According to our research, the analysis of InDel polymorphism using AlleleSEQR-PCR is more sensitive test for estimation of DC as compared with other assays. Moreover, the sensitivity of AlleleSEQR-PCR may be increased after isolation of the CD34 cell population in bone marrow. Nevertheless, observation of high levels in DC (³95%) in some leukemia patients (ALL, Ph+, bcr-abl/p190+) during first 6 months after HSCT cannot exclude the possibility of relapse. Thus, the combined monitoring of both DC (InDel) and MRD (oncogenes, WT1 and CD-markers) is a more advisable and useful test in managing hematologic malignancies and predicting relapse risk after allo-HSCT.

Digital PCR Panel for Sensitive Hematopoietic Chimerism Quantification after Allogeneic Stem Cell Transplantation

Accurate and sensitive determination of hematopoietic chimerism is a crucial diagnostic measure after allogeneic stem cell transplantation to monitor engraftment and potentially residual disease. Short tandem repeat (STR) amplification, the current “gold standard” for chimerism assessment facilitates reliable accuracy, but is hampered by its limited sensitivity (≥1%). Digital PCR (dPCR) has been shown to combine exact quantification and high reproducibility over a very wide measurement range with excellent sensitivity (routinely ≤0.1%) and thus represents a promising alternative to STR analysis. We here aimed at developing a whole panel of digital-PCR based assays for routine diagnostic. To this end, we tested suitability of 52 deletion/insertion polymorphisms (DIPs) for duplex analysis in combination with either a reference gene or a Y-chromosome specific PCR. Twenty-nine DIPs with high power of discrimination and good performance were identified, optimized and technically validated. We tested the newly established assays on retrospective patient samples that were in parallel also measured by STR amplification and found excellent correlation. Finally, a screening plate for initial genotyping with DIP-specific duplex dPCR assays was designed for convenient assay selection. In conclusion, we have established a comprehensive dPCR system for precise and high-sensitivity measurement of hematopoietic chimerism, which should be highly useful for clinical routine diagnostics.

Relapse assessment following allogeneic SCT in patients with MDS and AML

Options to pre-emptively treat impending relapse of myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML) after allogeneic haematopoietic stem cell transplantation (allo-SCT) continuously increase. In recent years, the spectrum of diagnostic methods and parameters to perform post-transplant monitoring in patients with AML and MDS has grown. Cytomorphology, histomorphology, and chimaerism analysis are the mainstay in any panel of post-transplant monitoring. This may be individually combined with multiparameter flow cytometry (MFC) for the detection of residual cells with a leukaemia phenotype and quantitative real-time polymerase chain reaction (RQ-PCR) to assess gene expression, e.g., of WT1 or the residual mutation load (e.g., in case of an NPM1 mutation). Data evaluating the aforementioned methods alone or in combination are discussed in this review with particular emphasis on data pointing towards their suitability to steer pre-emptive post-transplant interventions such as immunotherapy, chemotherapy or therapy with demethylating agents.

HY immune tolerance is common in women without male offspring

Background

Sex difference is an established risk factor for hematopoietic stem cell transplantation (HSCT)-related complications like graft versus host disease (GVHD). CD8^pos cytotoxic T cells specific for Y chromosome-encoded minor Histocompatibility antigens (HY) play an important role therein. Prior to HSC donation, female donors may encounter HY antigens through fetomaternal or transmaternal cell flow, potentially leading to the induction of HY-specific cytotoxic or regulatory immune responses. Whether HY priming occurs independent of parity, and whether HY priming is dependent on the presence of male microchimerism, is as yet unknown.

Methods

We investigated the presence of HY-specific regulatory T cells (Treg) and male microchimerism in 45 healthy women with a fully documented pregnancy and family history. HY peptide-induced linked suppression, a commonly reported functional feature of CD4^pos and CD8^pos Treg, was measured by trans vivo Delayed Type Hypersensitivity testing. As source of HY antigens, male microchimerism was analyzed by real-time PCR and defined by the presence of male DNA in at least one purified leukocyte cell type.

Results

HLA class I or class II restricted HY-specific Treg were detected in 26/42 (62%) women eligible for analysis. The prevalence of HY-specific Treg was significantly higher in women who had never given birth to sons than in women with male offspring (p = 0.004). Male microchimerism could be detected in 24 out of 45 (53%) women but did not correlate with the presence of HY specific Treg.

Conclusions

HY-specific Treg in women with male offspring have been described previously. Here we show for the first time that, in fact, HY specific Treg are more common in nulliparous women and in parous women with female offspring. Their presence is independent of the presence of male microchimerism. Whether HY-specific Treg presence in female stem cell grafts might decrease the GVHD incidence in male HSCT recipients needs to be investigated.

Molecular typing methods for minor histocompatibility antigens

Minor histocompatibility (H) antigen mismatching leads to clinically relevant alloimmune reactivity. Depending on the tissue expression pattern of the involved minor H antigens, the immune response may either cause graft-versus-host disease and a graft-versus-tumor effect or lead to only a graft-versus-leukemia effect. Thus, identification of recipient-donor pairs with minor H antigen mismatches has clinical importance. This chapter describes molecular typing methods for molecular typing of minor H antigens.

Outcome of allogeneic SCT in patients with chronic myeloid leukemia in the era of tyrosine kinase inhibitor therapy

The introduction of tyrosine kinase inhibitors (TKIs) for chronic myeloid leukemia (CML) led to a dramatic change in the role of allogeneic stem cell transplantation (SCT) with a rapid decline in the number of patients receiving SCT in first chronic phase (CP1). We evaluated 68 consecutive patients in all phases of CML (male/female = 39:29, 27 in CP1), who received SCT from related/unrelated donors (related/unrelated = 23:45) under myeloablative or reduced intensity conditioning (MAC/RIC = 45:23). Forty-eight patients (71 %) received TKIs pre-SCT, 20 patients post-SCT (29 %). Overall survival (OS) of CP1 patients achieved a plateau of 85 % at 10 months. Relapse-free survival (RFS) of CP1 patients was 85 % at 1 and 2 years, and 81 % at 5 years. Multivariate analysis showed adverse OS and RFS for patients transplanted >CP1 (hazard ratio (HR) = 6.61 and 4.62) and those who had grade III-IV aGvHD (HR = 2.45 and 1.82). Patients with advanced CML had estimated OS of 65 and 47 %; and RFS of 41 and 32 % at 1 and 2 years respectively. Therefore, for patients with advanced CML phases, allogeneic SCT provides an acceptable chance of cure. Transplant research should focus on improving conditioning regimens and post-SCT management for this subgroup of CML patients.

Acute GVHD is a strong predictor of full donor CD3+ T cell chimerism after reduced intensity conditioning allogeneic stem cell transplantation

The monitoring of chimerism is a standard procedure to assess engraftment and achievement of full donor lymphoid cells after reduced intensity conditioning (RIC) stem cell transplantation (Allo-SCT). However, there is no consensus on when and how often to monitor post-transplant chimerism. We retrospectively analyzed our experience regarding the impact of acute graft versus host disease (GVHD) for the prediction of allograft chimerism. One-hundred-and-fifteen patients transplanted between 2001 and 2010 were identified. This group included 57 females and 58 males with a median age of 50 years (range: 26-68). Patients evaluated in this study were adult patients with hematologic malignancies, who received transplants from an HLA-matched sibling donor or matched unrelated donor (MUD) at allele level so-called 10/10, and received the RIC regimen including fludarabine/busulfan and anti-thymoglobulin (ATG). Mixed T-cell chimerism was defined as between 5 and 94% recipient cells, and full chimerism was defined as the presence of more than 95% donor T-cell chimerism (TCC). Full donor TCC was achieved in 93 patients (81%) at a median of 77 days (range: 30-120) post-transplant. The cumulative incidence of Grade 2-4 GVHD in our population was 25% (95% CI 17-34). The analysis of the population of patients with acute GVHD grade ≥2 showed that at day 120 after Allo-SCT they all had a total full donor TCC. On the other hand, 78 (68%) patients without acute GVHD grade ≥2 presented with mixed chimerism (p = 0.002) on day 120 post-transplant. Interestingly, patients who received ATG 5 mg/kg obtained a higher probability of complete chimerism compared with those receiving 2.5 mg/kg (p = 0.03). In conclusion, our study demonstrates that acute GVHD was predictive of full donor TCC after RIC Allo-SCT. Therefore, our data may challenge the concept of the frequent or close monitoring of donor chimerism in some patients with ongoing acute GVHD. However, chimerism testing could represent an attractive modality for minimal residual disease detection or for impeding relapse warranting further prospective studies.

Impact of high-risk cytogenetics and achievement of molecular remission on long-term freedom from disease after autologous-allogeneic tandem transplantation in patients with multiple myeloma

Within a prospective protocol, the incidence and impact of achievement of molecular remission (mCR) and high-risk cytogenetics was investigated in 73 patients with multiple myeloma (MM) after autologous (auto)-allogeneic (allo) tandem stem cell transplantation (SCT). After induction chemotherapy, patients received melphalan 200 mg/m(2) before undergoing auto-SCT, followed 3 months later by melphalan 140 mg/m(2) and fludarabine 180 mg/m(2) before allo-SCT. Sixteen patients had high-risk cytogenetic features, defined by positive FISH for del(17p13) and/or t(4;14). Overall, 66% of the patients achieved CR or near-CR, and 41% achieved mCR, which was sustained negative (at least 4 consecutive samples negative) in 15 patients (21%), with no significant difference in incidence between the patients with high-risk cytogenetics and others (P = .70). After a median follow-up of 6 years, overall 5-year progression-free survival was 29%, with no significant difference between del 17p13/t(4;14)-harboring patients and others (24% versus 30%; P = .70). The 5-year progression-free survival differed substantially according to the achieved remission: 17% for partial remission, 41% for CR, 57% for mCR, and 85% for sustained mCR. These results suggest that auto-allo tandem SCT may overcome the negative prognostic effect of del(17p13) and/or t(4;14) and that achievement of molecular remission resulted in long-term freedom from disease.

The fate of donor osteocytes in fine particulate bone powders during repair of bone defects in experimental rats

The aim of the study was to investigate the fate of donor osteocytes in fine particulate bone powders during repair of bone defects in experimental rats. The iliac bone of male inbred DA rats was harvested and used as the larger bone grafts and also prepared as fine particulate (granulated) bone powders (300-500μm size particles) for transplantation into radial defects in female rats. The presence and relative amounts of genes specific to the sex-determining region of the Y-chromosome (Sry) originating from the bone grafts were evaluated by polymerase chain reaction and by in situ hybridization, respectively. Additional samples were evaluated histologically. In the larger bone grafts, the expression of Sry decreased relatively early, disappeared by 1 week, reappeared at 4 weeks and continued to increase with time. In the fine particulate bone powders, Sry was detected all the time and its expression was statistically greater than in the larger bone grafts at each time point. Both bone grafts provided donor cells to repair the defects. The donor cells seemed to function differently between the two groups. The fine particulate bone powders contained more living osteocytes in comparison with the larger bone grafts and may accelerate the healing of bone defects compared with conventional autografts.

Sex chromosome changes after sex-mismatched allogeneic bone marrow transplantation can mislead the chimerism analysis

A 12-year-old male with pre-B-cell acute lymphoblastic leukemia with cryptic BCR/ABL rearrangement underwent sex-mismatched allogeneic bone marrow transplantation (allo-BMT). Contradictory results were provided by various chimerism analyses 3 months later. Y-chromosome-specific quantitative polymerase chain reaction and sex chromosome-specific interphase fluorescence in situ hybridization (i-FISH) showed complete donor chimerism. Analysis of autosomal short tandem repeats (A-STR), BCR/ABL i-FISH test, and X-STR haplotype indicated relapse. Metaphase-FISH and combined BCR/ABL and sex chromosome-specific i-FISH patterns revealed loss of the Y-chromosome and duplication of the X-chromosome in the host cells. Sex chromosome changes after allo-BMT can cause significant difficulties in chimerism analysis.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: report from the Committee on Disease-Specific Methods and Strategies for Monitoring Relapse following Allogeneic Stem Cell Transplantation. Part I: Methods, acute leukemias, and myelodysplastic syndromes

Relapse has become the major cause of treatment failure after allogeneic stem cell transplantation. Outcome of patients with clinical relapse after transplantation generally remains poor, but intervention prior to florid relapse improves outcome for certain hematologic malignancies. To detect early relapse or minimal residual disease, sensitive methods such as molecular genetics, tumor-specific molecular primers, fluorescein in situ hybridization, and multiparameter flow cytometry (MFC) are commonly used after allogeneic stem cell transplantation to monitor patients, but not all of them are included in the commonly employed disease-specific response criteria. The highest sensitivity and specificity can be achieved by molecular monitoring of tumor- or patient-specific markers measured by polymerase chain reaction-based techniques, but not all diseases have such targets for monitoring. Similar high sensitivity can be achieved by determination of donor chimerism, but its specificity regarding detection of relapse is low and differs substantially among diseases. Here, we summarize the current knowledge about the utilization of such sensitive monitoring techniques based on tumor-specific markers and donor cell chimerism and how these methods might augment the standard definitions of posttransplant remission, persistence, progression, relapse, and the prediction of relapse. Critically important is the need for standardization of the different residual disease techniques and to assess the clinical relevance of minimal residual disease and chimerism surveillance in individual diseases, which in turn, must be followed by studies to assess the potential impact of specific interventional strategies.

Screening and monitoring of MPL W515L mutation with real-time PCR in patients with myelofibrosis undergoing allogeneic-SCT

Monitoring of minimal residual disease (MRD) after allogeneic (allo)-SCT for myelofibrosis (MF) allows recognizing the depth of remission and thus guides application of appropriate therapeutic interventions. MPL W515L/K mutations, which are detected in 5-10% of JAK2V617F-negative patients, may be useful for this purpose. Using a highly sensitive quantitative PCR method, we tested 90 patients with MF who underwent allo-SCT for the presence of MPL W515L/K mutations. Two patients with primary MF were found to harbor MPLW515L while no patient was positive for MPLW515K mutation. Both patients were JAK2V617F negative and cleared the mutation rapidly after allo-SCT and remained negative for a median follow-up of 19 months. The results of molecular monitoring correlated well with other remission parameters such as normalization of peripheral blood counts and morphology and complete donor chimerism. We conclude that MPLW515L can be cleared after allo-SCT and hence may be used as an MRD marker in a proportion of JAK2V617F-negative MF patients.

Characterisation of extramedullary relapse in patients with chronic myeloid leukemia in advanced disease after allogeneic stem cell transplantation

Recently, higher extramedullary relapse rates following allogeneic stem cell transplantation (SCT) in myeloid malignancies were reported e.g. because of selection of poor-risk patients. We analysed five consecutive patients with post-transplant extramedullary relapse of chronic myeloid leukemia (CML) out of a total of 24 patients (21%) undergoing allo-SCT. All five patients with extramedullary relapse had clonal evolution and a history of blast phase (BP). In particular, 56% of the patients in BP had extramedullary relapse with no extramedullary relapse in patients with chronic/accelerated phase. Most frequent manifestation sites were the skeletal system, the muscles/subcutaneous tissue and the central nervous system. In one case chloroma was mimicking myositis of the lower limbs. Combined approaches were performed including irradiation (n = 4), chemotherapy (n = 2), IM (n = 2), dasatinib (n = 4), nilotinib (n = 1), a novel aurora-kinase-inhibitor (n = 1), donor lymphocytes (n = 2) or a second allo-SCT (n = 2). Transient response was achieved in one case, stable partial remissions in two cases, whereas two cases were refractory. Research should focus on prospective studies aiming to improve treatment of extramedullary relapse in stem cell recipients with CML with a special focus on the role of second generation tyrosine kinase inhibitors.

Bone marrow mesenchymal stromal cells remain of recipient origin after allogeneic SCT and do not harbor the JAK2V617F mutation in patients with myelofibrosis

The close association of the myeloproliferative neoplasms with the activating non-receptor tyrosine kinase JAK2V617F mutation is well established. To further clarify the pathomechanisms of this mutation in patients with myelofibrosis, we performed screening with quantitative real-time PCR for the respective mutation in in vitro expanded bone marrow (BM) mesenchymal stromal cells (MSCs) and compared the results with BM/peripheral blood (PB). Eight patients with primary/secondary myelofibrosis were investigated before (n = 4) or after allogeneic stem cell transplantation (n = 4). All patients had systemic evidence of the JAK2V617F mutation in BM/PB (mutation ratios 0.2-23.5) at the time of investigation in contrast to negative results in the MSCs (n = 7) or a very low (0.004) mutation ratio (n = 1) which was probably due to hematopoietic contamination. The four patients post-transplant had systemic donor chimerism between 96.5 and 100% in BM/PB, while MSCs showed no evidence of donor-specific alleles. In conclusion, in myelofibrosis, the JAK2V617F mutation is restricted to hematopoietic cells, and cannot explain the stromal alterations being observed in this disorder. Further, the MSCs remain of recipient origin after allogeneic SCT, which might contribute to the increased risk of graft dysfunction or failure in myelofibrosis patients after allogeneic transplantation.

Naturally acquired tolerance and sensitization to minor histocompatibility antigens in healthy family members

Bidirectional cell transfer during pregnancy frequently leads to postpartum persistence of allogeneic cells and alloimmune responses in both the mother and in her offspring. The life-long consequences of naturally acquired alloimmune reactivity are probably of importance for the outcome of allogeneic stem cell transplantation. We investigated the presence of CD8(pos) minor histocompatibility (H) antigen-specific cytotoxic T lymphocytes (T(CTL)) and CD8(pos) minor H antigen-specific T regulator cells (T(REG)) in peripheral blood cells obtained from 17 minor H antigen-disparate mother-offspring pairs. Absence of minor H antigen-specific T(REG), as marked by the feasibility to expand T(CTL) from isolated tetramer(pos) populations, was observed in 6 mothers and 1 son. The presence of minor H alloantigen-specific T(REG) was observed in 4 mothers and 5 sons. These T(REG) were detected within isolated tetramer(dim) staining fractions and functioned in a CTLA-4-dependent fashion. Our study indicates that both T(CTL) and T(REG) mediated alloimmunity against minor H antigens may be present in healthy female and male hematopoietic stem cell donors, potentially influencing graft-versus-host reactivity in different ways.

Post-transplant immunotherapy with donor-lymphocyte infusion and novel agents to upgrade partial into complete and molecular remission in allografted patients with multiple myeloma

OBJECTIVE

To investigate post-transplant immunotherapy with escalating donor-lymphocyte infusions (DLI) and novel agents (thalidomide, bortezomib, and lenalidomide) to target complete remission (CR).

MATERIALS AND METHODS

Thirty-two patients with multiple myeloma who achieved only partial remission after allogeneic stem cell transplantation were treated with DLI. If no CR was achieved, one of the novel agents was added to target CR.

RESULTS

CR defined either by European Group for Blood and Marrow Transplantation criteria, flow cytometry, or molecular methods as assessed by patient-specific immunoglobulin H-polymerase chain reaction or plasma cell chimerism polymerase chain reaction was accomplished in 59%, 63%, and 50% of patients, respectively. Achievement of CR resulted in improved 5-year progressive-free and overall survival, according to European Group for Blood and Marrow Transplantation criteria (53% vs 35%; p=0.03 and 90% vs 62%; p=0.06), flow cytometry (74% vs 15%; p=0.001 and 100% vs 52%; p=0.1), or molecular methods (84% vs 38%; p=0.001 and 100% vs 71%; p=0.03).

CONCLUSIONS

Our finding demonstrates the clinical relevance of posttransplantation therapies to upgrade remission, and of remission's depth for long-term survival in myeloma patients.

Quantitative monitoring of NPM1 mutations provides a valid minimal residual disease parameter following allogeneic stem cell transplantation

BACKGROUND

Minimal residual disease (MRD) diagnostics in acute myeloid leukemia (AML) gain increasing importance after allogeneic stem cell transplantation (SCT). Nucleophosmin (NPM1) mutations, with their high frequency in AML, were suggested to represent suitable MRD markers, but so far no study has evaluated their usefulness in the posttransplantation period.

MATERIALS AND METHODS

We evaluated the validity of this MRD marker in the posttransplantation period in a cohort of 13 patients with an NPM1A mutation (NPM1Amut). For this most frequent NPM1A subtype, quantitative real-time polymerase chain reaction (qPCR) was retrospectively performed on bone marrow/peripheral blood samples that had been taken before and after SCT.

RESULTS

NPM1Amut was retrospectively followed up in 13 patients who received 14 transplantations. One-hundred and thirty-nine qPCR analyses were performed (median: 7 time points; median follow-up: 216 days; range, 35-1825 days). After SCT, 10 of 14 NPM1Amut cases (71%) became PCR-negative, of which four achieved stable remissions. All four patients (29%) who remained NPM1Amut-positive after SCT relapsed. In all nine relapse cases, increases of NPM1Amut were seen that preceded morphological relapse and the decrease of molecular chimerism with mean intervals of 24 days (range, 12-38 days) and 15 days (range, 1-36 days), respectively.

CONCLUSIONS

Quantitative assessment of NPM1Amut seems to provide a reliable MRD marker in the posttransplantation period, predicting relapse earlier than morphology or molecular chimerism, which should be confirmed in larger studies.

Minimal residual disease diagnostics in myeloid malignancies in the post transplant period

Allogeneic SCT is important in myelodysplastic syndrome, the BCR-ABL-negative chronic myeloproliferative diseases (CMPDs) and in poor-risk AML. Techniques to monitor the minimal residual disease, for example, by PCR or immunophenotyping gain increasing importance in the post transplantation period as basis for improved and earlier therapeutic interventions in impending relapse. Recent markers such as the NPM1 mutations in AML or the JAK2V617F mutation in the CMPD can be exactly quantified by real-time PCR and were evaluated for their prognostic value in the post transplantation phase and for their utility to plan adoptive immunotherapy in case of molecular relapse. With respect to chimerism, new and very sensitive methods were introduced, for example, quantitative assessment of genetic polymorphisms by real-time PCR, but also methods here are still highly individualized. Only in CML, where SCT focuses now on poor-risk cases or cases of tyrosine kinase inhibitor failure, follow-up schedules are standardized. Standardization of the different diagnostic techniques and of the intervals in the post transplantation period is urgently needed also in other myeloid malignancies and should be focus of future studies.

Isolation of mouse hepatocytes for transplantation: a comparison between antegrade and retrograde liver perfusion

We compared antegrade with retrograde liver perfusion when isolating mouse hepatocytes for hepatocyte transplantation. Male mouse hepatocytes were isolated by different perfusion methods and transplanted into the spleen of congeneic female mice. Retrograde perfusion yielded a larger number of cells (4.90 x 10(7)) than antegrade (4.09 x 10(7), p < 0.05), but hepatocytes obtained by antegrade perfusion gave higher engraftment efficiency (p < 0.05). More of the transplanted hepatocytes could be recovered from recipient liver with antegrade perfusion than with retrograde perfusion (p < 0.05). Our results indicate that hepatocytes isolated by antegrade perfusion gave a higher engraftment efficiency.

Molecular typing methods for minor histocompatibility antigens

Minor histocompatibility (H) antigens crucially affect the outcome of human leukocyte antigen-matched allogeneic stem cell transplantation. The number of molecularly identified minor H antigens is rapidly increasing. In parallel, clinical implementation of minor H antigens for immunotherapy has gained significant interest. It is therefore timely to type stem cell transplant recipients and their donors for minor H antigens. Here, we summarize all the currently known methodologies for minor H antigen typing on the genomic and on the RNA level.

Donor cell leukemia: a critical review

Approximately 40 cases of DCL have been reported in the literature; cases have been reported after allografts from bone marrow, peripheral blood and cord blood. The study of these cases may provide new insights into the mechanisms of leukemogenesis. Some data suggest that the prevalence of this complication has been under-estimated. Most cases of DCL have occurred following transplantation for leukemia, but there have also been cases reported after transplantation for non-malignant conditions. Various mechanisms have been proposed to explain how DCL arise and are briefly discussed. Additional studies are needed to define with more detail both the true prevalence of this complication and its precise pathogenetic mechanism.

Flow cytometry with anti HLA-antibodies: a simple but highly sensitive method for monitoring chimerism and minimal residual disease after HLA-mismatched stem cell transplantation

Transplantation of HLA-mismatched stem cells may allow determination of chimerism status of single cells by differential expression of HLA molecules. Monoclonal antibodies against HLA antigens can be used to determine the HLA type of sub-populations by standard flow cytometry. Blood samples from 23 patients transplanted from HLA-mismatched family donors were monitored using HLA-specific antibodies. Suitable antibodies could be found for all donor recipient pairs by using differences in HLA Bw4 and Bw6 groups or other serological antigens. Pretransplant controls of donor and recipient were used to correct for variable fluorescence intensities of the antibodies and sub-populations. Owing to the high sensitivity, cell populations with a minimum frequency of 0.1% were detectable. Flow-cytometric analysis was confirmed by chimerism analysis of immunomagnetically isolated T cells by standard PCR technique. In addition to chimerism evaluation, HLA antibodies improved the detection of leukemic cells after transplantation with aberrant phenotype. In conclusion, flow cytometry using antibodies against HLA antigens is an interesting tool for determination of chimerism and minimal residual disease after HLA-mismatched transplantation. Information about the chimerism status is given on a single-cell level and allows fast and convenient analysis of sub-populations.

Monitoring of the JAK2-V617F mutation by highly sensitive quantitative real-time PCR after allogeneic stem cell transplantation in patients with myelofibrosis

The JAK2-V617F mutation occurs in about 50% of patients with myelofibrosis and might be a reliable marker to monitor residual disease after allogeneic stem cell transplantation. We describe a new, highly sensitive (>or= 0.01%) real-time polymerase chain reaction (PCR) to monitor and quantify V617F-JAK2-positive cells after dose-reduced allogeneic stem cell transplantation. After 22 allogeneic stem cell transplantation procedures in 21 JAK2-positive patients with myelofibrosis, 78% became PCR negative. In 15 of 17 patients (88%), JAK2 remained negative after a median follow-up of 20 months. JAK2 negativity was achieved after a median of 89 days after allograft (range, 19-750 days). A significant inverse correlation was seen for JAK2 positivity and donor-cell chimerism (r:-0.91, P<.001). Four of 5 patients who never achieved JAK2 negativity fulfilled during the entire follow-up all criteria for complete remission recently proposed by the International Working Group, suggesting a major role for JAK2 measurement to determine depths of remission. In one case, residual JAK2-positive cells were successfully eliminated by donor lymphocyte infusion. In conclusion, allogeneic stem cell transplantation after dose-reduced conditioning induces high rates of molecular remission in JAK2-positive patients with myelofibrosis, and quantification of V617F-JAK2 mutation by real-time PCR allows the detection of minimal residual disease to guide adoptive immunotherapy.

Quantitative analysis of chimerism after allogeneic stem cell transplantation by real-time polymerase chain reaction with single nucleotide polymorphisms, standard tandem repeats, and Y-chromosome-specific sequences

We compared the results of chimerism analyses with real-time SNP-PCR to those obtained by the classical STR-PCR method in 135 hematopoietic stem cell transplantation recipients. Using 10 different SNP gene loci, the SNP-PCR method was able to discriminate patient from donor cells in 125 of 135 cases (93%), whereas the use of 11 different STR gene loci with the STR-PCR analysis using agarose or polyacrylamide gel resolution resulted in accurate donor-host discrimination in all patients. Of the 470 analyzed samples we found in 74% concordant results for both chimerism methods. In all 26% discordant cases the SNP-chimerism method showed mixed chimerism (MC), whereas the STR-method found complete chimerism (CC). As a consequence, the SNP-PCR chimerism analysis method detected a MC prior to the occurrence of relapse significantly earlier than the STR-PCR chimerism method (120 vs. 30 days, P < 0.007). The probability of relapses was significantly higher in patients with increasing MC (70%) compared to 30% in patients with CC (P < 0.00001) associated with a significantly shorter overall survival in patients with increasing MC. The multivariate Cox model showed that chimerism analsis with SNP-PCR was the only significant risk factor predicting relapse (RR 6.08, P < 0.0001).Furthermore, we analyzed the chimerism status in male recipients with a female donor in 580 samples of 134 patients using quantitative real-time PCR of Y-chromosome-specific sequences and compared the results with interphase XY-fluorescent in situ hybridization (FISH). MC without signs of relapse was detected in 35% of samples using quantitative real-time PCR of Y-chromosome-specific sequences. The detected Y-DNA amounts were low compared to the amounts detected in 104 samples of 42 patients with leukemic relapse at the time of analysis (P < 0.0001). Quantitative real-time PCR of Y-chromosome-specific sequences detected therefore an increasing MC with high residual host DNA amounts approximately 143 days (mean) prior to the occurrence of relapse. By comparing the results of Y-chromosome PCR with the XY-FISH analysis we found concordant results in 73% in patients with myeloablative regimens. The XY-FISH could detect 12 relapses, whereas the Y-chromosome PCR detect 36 relapses by MC (P < 0.005). Residual host cells gradually decreased during the posttransplant period from a mean of 5.4 ng (first months) to 0.5 ng (above 5 years) without evidence of relapses. The probability of relapses was significantly higher in patients with increasing MC (100%) compared to 8% in patients with CC (P < 0.00001) associated with a significantly shorter overall survival in patients with increasing MC. The multivariate Cox model showed that chimerism analysis of Y-chromosome-specific sequences is an important risk factor for relapse (RR 17.0, P < 0.0001). We conclude that the use of real-time SNP or Y-PCR may be superior to the STR-PCR or interphase XY-FISH methods in detecting patients who are at high risk for relapse after transplant.

Reduced-toxicity conditioning with treosulfan, fludarabine and ATG as preparative regimen for allogeneic stem cell transplantation (alloSCT) in elderly patients with secondary acute myeloid leukemia (sAML) or myelodysplastic syndrome (MDS)

We investigated a dose-reduced conditioning regimen consisting of treosulfan and fludarabine followed by allogeneic stem cell transplantation (SCT) in 26 patients with secondary AML or MDS. Twenty patients were transplanted from matched or mismatched unrelated donors and six from HLA-identical sibling donors. The median age of the patients was 60 years (range, 44-70). None of the patients was eligible for a standard myeloablative preparative regimen. No graft-failure was observed, and leukocyte and platelet engraftment were observed after a median of 16 and 17 days, respectively. Acute graft-versus-host disease (GvHD) grade II-IV was seen in 23% and severe grade III GvHD in 12% of the patients. No patients experienced grade IV acute GvHD. Chronic GvHD was noted in 36% of the patients, which was extensive disease in 18%. The 2-year cumulative incidence of relapse was 21%. The relapse rate was higher in patients beyond CR1 or with intermediate two or high risk MDS (P = 0.02). The treatment-related mortality at day 100 was 28%. The 2-year estimated overall and disease-free survival was 36-34%, respectively. No difference in survival was seen between unrelated and related SCT.

Kinetics of plasma-cell chimerism after allogeneic stem cell transplantation by highly sensitive real-time PCR based on sequence polymorphism and its value to quantify minimal residual disease in patients with multiple myeloma

OBJECTIVE

To investigate lineage-specific chimerism of plasma cells after allogeneic transplantation by real-time PCR based on bi-allelic sequence polymorphism or, in case of female-to-male transplantation, on the detection of the DFFRY gene and to determine its value to quantify minimal residual disease in myeloma patients.

METHODS

Forty-eight samples from bone marrow samples and peripheral blood from 34 nonmyeloma patients were analyzed at different times after transplantation. Sixty-two samples from 22 myeloma patients were analyzed at different times after allogeneic stem cell transplantation, and results were compared with immunofixation and, in some cases, with PCR data using patient-specific primers.

RESULTS

The median chimerism for T cells at day +100 was greater than 99.9% and remained stable on day +180 and 1 year after transplantation. In contrast, the median donor plasma cell chimerism at day +100 was 95.5%, at day +180 98.6%, at day +360 99.8%, and 2 or more years after transplantation greater than 99.9%. Sensitivity of real-time PCR using human short insertion/deletion polymorphisms (SIDP) was 10(-4) and in case of Y-PCR 10(-5). Sequential monitoring of donor plasma cell chimerism showed that increasing and stable chimerism were associated with ongoing remission in 15 out of 16 samples (93%), and decreases in chimerism predicted relapse in 5 out of 6 patients.

CONCLUSION

We conclude that plasma cell chimerism after allogeneic stem cell transplantation is delayed in comparison to T-cell chimerism. Sequential quantitative measurement of plasma cells after allogeneic stem cell transplantation with highly sensitive real-time PCR allows monitoring of residual host-tumor cells in patients with multiple myeloma and allows guiding adoptive immunotherapy strategies to enhance remission status and to prevent clinical relapse.

Monitoring minimal residual disease by quantification of genomic chromosomal breakpoint sequences in acute leukemias with MLL aberrations

An estimated 10% of acute leukemias carry mixed-lineage leukemia (MLL) fusion genes. Approximately 50 different fusion partners of the MLL gene have already been molecularly identified. These leukemias are commonly regarded as high-risk cases and are treated accordingly with intensified therapy regimens, including hematopoietic stem cell transplantation. However, a subset of patients may achieve long-term remissions with conventional therapy. Monitoring minimal residual disease (MRD) is undoubtedly of great value in clinical decision making, also in the pre- and post-transplant setting. Here, we describe a novel method for detecting MRD in leukemias with MLL aberrations. The method is based on monitoring patient-specific chromosomal breakpoint DNA sequences. This has several advantages over other methods that are based either on detecting specific RNA molecules of MLL fusion genes or on surrogate markers. An accurate and absolute quantification of the MRD level is possible. No reference to housekeeping genes is necessary and the target structure is much more stable than any mRNA fusion transcript.

The difficulty of eliminating donor leukocyte microchimerism in rat recipients bearing established organ allografts

BACKGROUND

Unequivocal eradication of donor leukocyte microchimerism from recipients of long-surviving organ transplants has never been reported. Here we describe a drastic attempt to accomplish this objective.

METHODS

In control experiments, a rank order of microchimerism and of associated donor specific nonreactivity was produced in Brown-Norway (BN) rats by transplantation of Lewis (LEW) liver, bone marrow cell (BMC) and heart allografts under a brief course of tacrolimus. The degree of microchimerism at 60 and 110 days was estimated with semiquanitative immunocytochemical and PCR techniques. Tolerance at 110 days was assessed in the different control groups by challenge transplantation of naïve LEW hearts. In parallel experimental groups, an attempt was made to eliminate microchimerism from the BN recipients. The animals were submitted at 60 days to 9.5-Gy total body irradiation (TBI), reconstituted immediately with naïve BN BMC, and tested for donor specific nonreactivity by LEW heart transplantation at 110 days.

RESULTS

After the TBI-reconstitution at 60 days, microchimerism was undetectable in BMC recipients at 110 days, significantly reduced in heart recipients, and least affected in liver recipients. Except in liver recipients, abrogation of LEW-specific nonreactivity was demonstrated by rejection of the priming grafts, or by rejection of the challenge heart grafts, and by in vitro immune assay.

CONCLUSIONS

It is difficult to eliminate microchimerism in organ recipients once the donor cells have settled into tissue niches.

Morphology of the bone marrow after stem cell transplantation

In many haematological conditions the only curative option is stem cell (SCT) or bone marrow (BM) transplantation. Little information exists about BM morphology following non-ablative engraftment. During the pretransplantation period and depending on the kind of pretreatment, there may be hypoplasia, residual disease and varying degrees of fibrosis. In the post-transplantation period, after 1-3 weeks of transfusion-dependent pancytopenia, the first signs of successful engraftment are indicated by the recurrence of neutrophils, monocytes and erythrocytes in the peripheral blood. In the BM there is slow regeneration of erythropoiesis, followed by the other lineages of haematopoiesis and increase in reticulin fibres or even a resolution of fibrosis. Diagnostic problems arise when neoplastic lympho- or haematopoiesis are maintained following transplantation. Moreover, there may be a significant graft versus tumour response reaction or an already relapsing disease needing aggressive treatment. On the other hand, a conspicuous dyshaematopoiesis should not be mistaken as representing a myelodysplastic syndrome. The presence of granulomas being treatment-related or a manifestation of intercurrent granulomatous disease has to be considered. More advanced knowledge of the histological features of regenerating BM will certainly aid the recognition of relapsing disease and is needed for the adequate reporting of post-transplant alterations associated with a successful or failing engraftment.

Kinetics of dendritic cell chimerism and T cell chimerism in allogeneic hematopoietic stem cell recipients

Dendritic cells (DC) as potent antigen-presenting cells (APC) and T cells as effector cells play an essential role in the pathophysiology of both graft-versus-host (GvH) and graft-versus-leukemia (GvL) reactions after transplantation. Therefore, we determined the kinetics of DC and T-cell chimerism establishment after allogeneic hematopoietic cell transplantation (AHCT) in a group of 144 patients, using fluorescence-activated cell sorting (FACS) or magnetic cell sorting (MACS) followed by FISH or STR-PCR analysis for chimerism evaluation. In all, three cell lines investigated (CD3(+) T cells, CD11c(+) DC1 and CD123(+) DC2), we found a rapid and consistent establishment of complete donor chimerism (CDC) in over 70% of all patients during the first 6 weeks after AHCT. The rate of patients with CDC increased significantly over time within the first year after transplantation. A related donor (P=0.004) as well as an underlying lymphatic leukemia (P=0.03) were found to be significantly associated with development of MC in T cells. No significant correlation between DC or T cell chimerism and GvHD or relapse was detected. Our results thus demonstrate a fast and stable CDC in DC1, DC2 and T cells after AHCT that continuously increases over time in nearly all patients.

Comparison between antithymocyte globulin and alemtuzumab and the possible impact of KIR-ligand mismatch after dose-reduced conditioning and unrelated stem cell transplantation in patients with multiple myeloma

We compared antithymocyte globulin (ATG) with alemtuzumab in 73 patients with multiple myeloma, who underwent reduced conditioning with melphalan/fludarabine, followed by allogeneic stem cell transplantation from human leucocyte antigen-matched or -mismatched unrelated donors. The ATG group had more prior high-dose chemotherapies (P < 0.001), while bone marrow was used more as the stem cell source in the alemtuzumab group (P < 0.001). Alemtuzumab resulted in faster engraftment of leucocytes (P = 0.03) and platelets (P = 0.02) and in a lower incidence of acute graft versus host disease (GvHD) grades II-IV (24% vs. 47%, P = 0.06). More cytomegalovirus (CMV) seropositive patients in the alemtuzumab group experienced CMV reactivation (100% vs. 47%, P = 0.001). The cumulative incidence of treatment-related mortality at 2 years was 26% [95% confidence interval (CI) = 12-37%] for ATG vs. 28% (95% CI = 15-55%) for alemtuzumab, P = 0.7. There was no significant difference in the estimated 2-year overall and progression-free survival between ATG and alemtuzumab: 54% (95% CI: 39-75%) vs. 45% (95% CI: 28-73%) and 30% (95% CI: 16-55%) vs. 36% (95% CI: 20-62%) respectively. In multivariate analysis, treatment with alemtuzumab had a higher risk for relapse (hazard ratio: 2.37; P = 0.05) while killer immunoglobulin-like receptor (KIR)-ligand mismatch was protective for relapse (P < 0.0001). We conclude that alemtuzumab produced less acute GvHD, but higher probability of relapse. The data implicated a major role of KIR-ligand mismatched transplantation in multiple myeloma.

Male cell microchimerism in normal and diseased female livers from fetal life to adulthood

Male microchimerism is frequent in the adult female liver and is attributed to fetal cells originating from previous male offspring. It has never been studied in pregnant women, female children, or fetuses. We examined its frequency and cellular nature in normal and diseased female livers from fetal life to adulthood. Forty-six liver samples from 29 women, 6 female children, and 11 female fetuses were screened for the Y chromosome via polymerase chain reaction (PCR) assay and fluorescent in situ hybridization (FISH). The X chromosome was used as an internal control. A third PCR assay was used for Y genotyping. The Y chromosome was detected in 5 of 6 children, 7 of 11 fetuses, 3 of 9 women with normal liver, 7 of 10 women with chronic hepatitis C, 5 of 6 women with acute liver disease during pregnancy with male offspring, and 2 of 4 nonpregnant women with fulminant hepatitis. In positive samples, the mean XY/XX ratio was 0.012 (+/-0.004). In women, male microchimerism was correlated with previous male offspring. Male hepatocytes, detected via FISH combined with anti-hepatocyte immunohistochemistry, were observed only in fetuses (4/9) and in postpartem women (4/6). Y genotypes were different from each other in 4 of 5 female livers. In conclusion, male liver microchimerism is frequent in normal and diseased female livers. The presence of male cells in the liver of female children and fetuses is probably due to the transplacental transmission of fetal cells preexisting in the mother and acquired either from previous pregnancy with male offspring or during the mother's own fetal life.