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One of the pre-requisites for forensic DNA analysis is the fact that all nucleated cells of a person carry the same genetic information. However, this is not the case for individuals who have received an allogeneic hematopoietic stem cell or bone marrow transplantation, as all new cells formed by the bone marrow no longer show the genetic information of the recipient but that of the donor, while all other cells still carry the original information before transplantation. Thus, STR typing of a blood sample after successful transplantation yields a DNA profile that differs from the recipient’s original profile and corresponds to the donor genotype instead. Evidence from a routine case suggests that transplanted individuals may show donor alleles in skin swabs, as well. In order to examine this issue more closely, various skin swabs from 28 patients who have received an allogeneic hematopoietic stem cell transplantation were examined in this study. Swabs from the right and left palm, the back of the hand, one of the two upper arms, and the neck were collected from each person. Ninety-one of the 140 resulting swabs delivered useful results. All of those samples showed mixtures of recipient and donor DNA with different mixture ratios and the proportions of donor and recipient alleles revealed inter- and intra-individual differences. Those results were discussed with respect to graft versus host disease.

We retrospectively compared the incidence of virus infections and outcome in the context of immune reconstitution in two different HLA-haploidentical transplantation (haplo-HSCT) settings. The first was a combined T-cell-replete and T-cell-deplete approach using antithymocyte globulin (ATG) prior to transplantation in patients with hematological diseases (cTCR/TCD group, 28 patients; median age 31 years). The second was a T-cell-replete (TCR) approach using high-dose posttransplantation cyclophosphamide (TCR/PTCY group, 27 patients; median age 43 years). The incidence of herpesvirus infection was markedly lower in the TCR/PTCY (22 %) than in the cTCR/TCD group (93 %). Recovery of CD4+ T cells on day +100 was faster in the TCR/PTCY group. CMV reactivation was 30 % in the TCR/PTCY compared to 57 % in the cTCR/TCD group, and control with antiviral treatment was superior after TCR/PTCY transplantation (100 vs 50 % cTCR/TCD). Twenty-five percent of the patients in the cTCR/TCD group but no patient in the TCR/PTCY group developed PTLD. While 1-year OS was not different (TCR/PTCY 59 % vs cTCR/TCD 39 %; p = 0.28), virus infection-related mortality (VIRM) was significantly lower after TCR/PTCY transplantation (1-year VIRM, 0 % TCR/PTCY vs 29 % cTCR/TCD; p = 0.009). On day +100, predictors of better OS were lymphocytes >300/μl, CD3+ T cells >200/μl, and CD4+ T cells >150/μl, whereas the application of steroids >1 mg/kg was correlated with worse outcome. Our results suggest that by presumably preserving antiviral immunity and allowing fast immune recovery of CD4+ T cells, the TCR approach using posttransplantation cyclophosphamide is well suited to handle the important issue of herpesvirus infection after haplo-HSCT.

Prognosis is poor for patients with biologically aggressive Non-Hodgkin lymphoma (NHL), refractory to chemotherapy or relapsed after autologous transplantation, especially when no disease control before allogeneic transplantation is achieved. In 16 patients (median age 53, median prior regimes 5) with relapsed or refractory non-remission NHL, we analysed retrospectively the efficacy of a sequential therapy comprising clofarabine re-induction followed by a reduced-intensity conditioning with fludarabine, CY and melphalan, and T-cell-replete HLA-haploidentical transplantation. High-dose CY was utilized post-transplantation. All patients engrafted. Early response (day +30) was achieved in 94%. Treatment-related grade III-IV toxicity occurred in 56%, most commonly transient elevation of transaminases (36%), while there was a low incidence of infections (19% CMV reactivation, 19% invasive fungal infection) and GVHD (GVHD: acute III-IV: 6%; mild chronic: 25%). One-year non-relapse mortality was 19%. After a median follow-up of 21 months, estimated 1- and 2-year PFS was 56 and 50%, respectively, with 11 patients (69%) still alive after 2 years. In summary, sequential therapy is feasible and effective and provides an acceptable toxicity profile in high-risk non-remission NHL. Presumably, cytotoxic reinduction with clofarabine provides enough remission time for the graft-versus lymphoma effect of HLA-haploidentical transplantation to kick in, even in lymphomas that are otherwise chemo-refractory.

Introduction: Monitoring of minimal residual disease (MRD) is commonly used after allogeneic stem cell transplantation (SCT) in acute myeloid leukemia (AML) patients. Flow cytometry of leukemia-associated aberrant immunophenotypes (LAIP) and chimerism analyses are frequently used tools to monitor MRD. These methods have lower sensitivities and lower relapse detection rates in contrast to molecular markers monitored by quantitative RT-PCR. However, their clinical implications are still limited and only little evidence of single molecular markers is available. We report on a retrospective study of 144 patients with molecular MRD markers transplanted at the Ludwig-Maximilans-University Hospital of Munich-Grosshadern, and analyzed the prognostic values of molecular MRD Monitoring after SCT, baseline risk factors, and follow-up (FU) markers (e.g. chimerism analyses and LAIP). Patients and Methods: Between January 2000 and August 2012, 495 AML patients underwent SCT at our institution. 164 patients had molecular MRD markers and 144 patients had at least one sample with quantitative results prior and/or after SCT, and were included into the analyses. At transplantation, patients had a median age of 48 years (range, 18 -73), and 49 patients were in complete remission, while 95 patients were in a more advanced status of their disease (>CR2). 106 patients received SCT from a HLA matched (10/10) and 38 patients from a HLA mismatched donor. Grafts were obtained either from related (n=60) or unrelated (n=84) donors. Most patients received reduced intensity conditioning (n=142). In 338 bone marrow samples MRD was monitored prior to SCT, on day +30 and on day +100. During the FU period after day +100, MRD was monitored at individual intervals in 429 peripheral blood samples. Quantitative RT-PCR was performed for NPM1 mutation (n=52), MLL-PTD (n=31), RUNX1-RUNX1T1 (n=12), CBFß-MYH11 (n=14), MLL rearrangements (n=20), MDS-EVI1/EVI1 (n=10), and DEK-CAN (n=5). Sensitivities of the different RT-PCRs assays ranged between 10-4 and 10-6. Results: After a median FU of 41 months (range, 4 – 115), 43 patients (30%) relapsed. The MRD levels monitored by RT-PCR prior to SCT and on day +30 after SCT showed no significant impact on relapse-free survival (RFS) and overall survival (OS). At day +100 after SCT, MRD positivity was strongly associated with worse RFS (HR 3.1, p=0.001) and OS (HR 3.2, p=0.004). This was also reflected in a cumulative two-year incidence of relapse of 61% for MRD positive patients versus 15% for MRD negative patients (p Conclusions: Molecular MRD monitoring after SCT might be a useful tool to identify AML patients at high risk for relapse, in contrast to other FU markers, e.g. chimerism analyses and LAIP. In particular, MRD positivity on day +100 after SCT and the switch to MRD positivity during the FU period were significantly associated with worse RFS. As perspective, the individual molecular MRD course might be used as prognostic factor for the guidance of treatment post SCT. Patients with MRD positivity on day +100 after SCT or with a switch to MRD positivity in the FU period may be considered for donor lymphocyte infusions (DLI) or chemotherapeutic interventions, such as hypomethylating agents. Disclosures Subklewe: AMGEN Inc.: Research Funding.

Allogeneic hematopoietic stem cell transplantation (HSCT) has become a valuable therapeutic option for malignant and non-malignant hematological diseases. Engraftment of donor cells is confirmed by repetitive testing for donor chimerism. Since the underlying malignant disease is host derived, the decrease of donor chimerism might precede or indicate the imminent relapse, enabling early intervention and presumably better outcome. STR-assay (Short-Tandem-Repeats-Assay) and XY-FISH (XY based Fluorescence in Situ Hybridization) respectively are routinely performed after HSCT. Furthermore CD34+ cell- chimerism and quantification of minimal residual disease in patients with informative markers might be used to detect early relapse. In this prospective, non-interventional study we evaluated the accuracy, reliability and feasibility of a qPCR based commercially available assay (Allele SEQR® Chimerism Assay, Abbott). In addition, the early detection of hematological relapse was analyzed as a clinical readout. Between May 2011 and January 2013 95 patients received allogeneic HSCT for MDS or acute leukemia (AML = 84) at our transplantation unit and were therefore included in our analysis. According to our local standard bone marrow samples were collected at standardized time points including days 30, 90, 180. The qPCR based Allele SEQR® Chimerism Assay consists of two parts: screening for discriminating, informative markers and subsequent actual quantification of the host DNA. For assay validation 68 patients were suitable. In all patient/donor pairs at least one informative marker could be found and quantitative results could be achieved. In 65/68 pairs (95.6%) even ≥ 2 markers could be identified, however, among 28 related donors three (10.7%) only revealed one discriminating marker. The sensitivity of the assay was proven by means of artificially spiked DNA samples mimicking an amount of 0.1%, 0.05% and 0.01% of “host“ DNA respectively. Testing was performed with 100ng/well patient DNA. The overall time needed for testing was less than four hours. We identified 61 patients with at least two samples in cytomorphological complete remission (CR) after allogeneic HSCT. The overall hematological relapse rate in our cohort was 23% until March 2014. To enable relapse prediction we quantified donor chimerism in CR samples. Scoring for suspicious results by the increase of host chimerism by at least one percent point, but not less than one third as compared to previous testing, was highly predictive for imminent relapse (overall relapse rate 86% vs. 15%, p= The evaluated qPCR approach proved as a fast and highly sensitive tool for chimerism monitoring after HSCT. It may allow an early detection or exclusion of imminent relapse, enabling chimerism triggered therapy. In perspective we will validate this assay for peripheral blood samples, allowing more convenient and frequent testing. Disclosures Reibke: Abbott molecular Germany: Research Funding.