ALBERT

Description: In the last years, focus of regenerational studies has pointed on mesenchymal stem cells (MSC) and their ability to differentiate into several mesenchymal tissues. MSC have been shown to play a pivotal role in the microenvironment of bone marrow cells and in the modulation of immune response as they can suppress lymphocytic proliferation in vitro. Moreover, some animal studies have suggested they could favor the proliferation of malignant cell clones in solid tumor models. Their role in hematological malignancies, however, remains to be further elucidated and little is known about the influence of MSC in the development and maintenance of the malignant clone in chronic myeloid leukemia (CML). This disease is characterized by the presence of the Philadelphia (Ph) chromosome, a fusion product generated by the reciprocal translocation between chromosomes 9 and 22. Previous reports showed that hepatocytes precursors, found in the liver of CML patients carry the Ph translocation. Our intent was to elucidate whether MSC isolated from patients with CML in different stages of the disease originate from the malignant clone. To this purpose bone marrow aspirates of 11 patients with CML were obtained after informed consent. Five patients were analyzed at diagnosis, two after allogenic stem cell transplantation, three on treatment with the tyrosine kinase inhibitor imatinib and one on treatment with interferon alpha in combination with hydroxyurea. MSC were then generated as previously described. Briefly, cells were isolated by density gradient methods, resuspended in RPMI1640 medium containing 10% fetal bovine serum and plated in culture flasks to adhere. After 4–5 weeks of culture cells were collected and characterized by the expression of several surface markers in a fluorescence activated cell sorter (FACS). The presence of the Ph chromosome was assessed by both fluorescence in situ hybridization (FISH) and polymerase chain reaction (nested PCR). Moreover whole bone marrow was analyzed and results compared with those obtained in the MSC population. MSC showed a typical morphological pattern, growing to confluence after a few weeks of culture and appearing as an adherent, spindle shaped cell layer. In FACS they stained positive for SH2 and SH3 and did not express CD34, CD45 and CD14. MSC were then analyzed by FISH using probes for BCR-ABL. We could not detect the Ph translocation in any of the analyzed patients, though it was present at variuos levels in the remnant bone marrow cells. Results did not change, if expression of BCR-ABL was measured by high sensitivity RT-PCR. Our results showh that MSC of patients with CML are Philadelphia negative irrespective of the stage of disease and the treatment given, suggesting that these cells are not involved in the development of the malignancy. However, their interactions with leukemic cells as well as their role in the immune response against the tumor remains to be further characterized.

Description: NK-cells have been shown to play a pivotal role in haploidentical hematopoietic cell transplantation (HHCT) for engraftment, GvL effects and to combat infectious complications. Different strategies have been employed to hasten NK-cell recovery after HHCT. Here we compare the immune recovery of 17 patients after CD34 selected HHCT receiving additional adoptive CD3-depleted CD56-enriched NK cells 2 days after HHCT (adoptive NK-cells), with 18 patients receiving CD3/CD19 depleted grafts (CD3/CD19) for HHCT. Transplantations were performed at two different institutions with a median follow-up of 〉1 year. Conditioning consisted of 12 Gy TBI, thiotepa (10mg/kg), fludarabine (150 mg/m2) and OKT3 (day −4 to +2) in the group receiving CD34 selected grafts and adoptive NK-cell transfusions. All patients in the CD3/CD19 group received conditioning with fludarabine (150–200 mg/m2), thiotepa (10 mg/kg), melphalan (120 mg/m2) and OKT-3 (day −5 to +14). No postgrafting immunosuppression was used in both groups. Seven out of the 17 patients in the adoptive NK-cell group received IL-2 activated NK cells. Median age was 37 years in the adoptive NK-cell group compared to 40 years in the CD3/CD19 group. Diagnoses in the adoptive NK-cell group included AML (n=10), ALL (n=3), CML (n=2), and Hodgkin’s disease (n=1) and MDS (n=1). Diagnoses in the CD3/CD19 group were AML (n=10), ALL (n=5), NHL (n=1), CML (n=1) and multiple myeloma (n=1). The grafts contained a median of 12.5x10E6 CD34+ cells/kg and 1.1×10E4 CD3+ cells/kg in the CD34 selected group versus 9.2×10E6 CD34+cells/kg and 2.3×10E4 CD3+cells/kg in the CD3/CD19 group. The number of transferred CD56+ cells was 8.3×10E6/kg in the adoptive NK-cell group and 7.2×10E7/kg cells in the CD3/CD19 group. Hematopoietic recovery was similar in both groups. Among the patients receiving adoptive NK-cells we observed a striking difference in immune recovery between the patients receiving IL2-activated and those treated with non-activated NK cells: patients receiving activated NK cells showed significantly lower numbers of NK- and T cells during the first months post transplant (p=

Description: Background: In vivo T cell depletion with ATG or Alemtuzumab is effective to reduce the incidence of graft-versus host disease (GVHD) caused by alloreactive T cells. However, there is also a potential impact of these substances on the function of natural killer (NK) cells who are the predominant cells in peripheral blood in the early phase after hematopoietic stem cell transplantation (HSCT) and mediate beneficial graft-versus-tumor activity. Using a novel flow cytometric assay, which detects the lytic granule membrane protein CD107a as a marker for NK cell degranulation, we investigated the effect of T cell depletion with ATG and Alemtuzumab on NK cell function in the early phase after HSCT. Methods: PBMCs of 34 patients (pts) at day +30 after allogeneic HSCT and of 16 healthy donors were coincubated at 37°C for 3 h with the NK sensitive cell line HL60. In each tube, containing 400μl effector/target suspension (2x106 cells), 20μl of PE-Cy5 conjugated anti-CD107a monoclonal antibody was added prior to incubation. After the first 1 h 10μl of the secretion inhibitor 2 mM monensin was added. At the end of coincubation cells were stained with mAbs (CD56, CD3) for flow cytometry. The percentage of CD107a expressing NK cells was assessed and the absolute number of degranulating NK cells/μl was calculated. Results: Treatment Characteristics: Fourteen pts received ATG, ten pts were treated with Alemtuzumab and ten patients did not receive T cell depletion. The source of donor was: MRD 12 and MUD 22. NK cell count: The median NK cell count was: 250/μl in healthy individuals, 250/μl in pts without T cell depletion, 400/μl in pts with ATG and 100/μl in pts receiving Alemtuzumab (p

Description: Objective: Most tumors express antigens which, when presented by MHC molecules, can be recognized by cytotoxic T-lymphocytes. These tumor-associated-antigens (TAA) are considered to be key determinants in the graft-versus-tumor effect after allogeneic hematopoietic cell transplantation (HCT) and are therefore potential candidates for tumor vaccination. Unfortunately only small numbers of TAA have been isolated to date. In this project we looked for immunogenic peptides presented by bcr/abl+ cells of an HLA-A32 CML patient. Methods: Leukemia-specific mixed lymphocyte leukemia cell cultures (MLLC) were generated by co-culturing irradiated bcr/abl+ cells from the patient with peripheral blood mononuclear cells (PBMC) from the HLA-identical, related stem cell donor. The cultures were re-stimulated once per week with irradiated leukemic cells and IL-2. A cDNA library was constructed from bcr/abl+ leukemic cells in pcDNA3.1 and divided into pools of 100 cDNAs. 293T cells were then co-transfected with each pool together with the appropriate HLA-cDNA and tested 48 h later in an IFN-gamma Elispot assay using CD8+ sorted MLLC cells. Positive cDNA pools were divided into sub-pools of 10 colonies and re-screened. Positive sub-pools were finally separated into single clones and screened again. The entire open reading frame of NM23-H2 was amplified by PCR, cloned into an expression vector and transfected together with HLA-A32 cDNA into 293T cells to confirm reactivity in the Elispot assay. The immunogenicity of synthetic peptides was determined by direct loading of HLA-A32 expressing APCs. Peptides (10cg) were also tested in the ELISPOT assays with CD8+ sorted PBMC of the patients at different time points after HCT. Results: An MLLC responder cell population recognized bcr/abl+ cells (CD14+, CD34+ subpopulations and EBV) without recognising bcr/abl− cells (CD4+ and CD8+ T cells or PHA blasts). The reaction was completely blocked by two monoclonal antibodies against HLA class I antigens. Screening of the cDNA library identified 3 HLA-A32 restricted positive single clones, all of which were 600 bp long. Sequencing revealed each to be identical to NM23-H2 (An NDP kinase and transcriptional activator of c-myc) without any mutations or translocations. Although no anchors for HLA-A32 have yet been defined, two viral peptides known to be restricted by HLA-A32 have tryptophan at position 9. Three Nm23 peptides which share this feature (NM23-H270–78, NM23-H2125–133, NM23-H2141–149) were identified, synthesized and tested in the ELISPOT assay. Of these, only the Nm23-H270–78 (SGPVVAMVW) generated a positive reaction. Specific recognition of SGPVVAMVW was half-maximal at a concentration of 1 nM. Subsequently, we looked for reactivity against the peptide in vivo, stimulating CD8+ sorted PBMC at different time points after HCT. While no reaction was detectable either before or up to 3 months after HCT, positive reactions were observed thereafter. Conclusion: Peptide Nm2370–78 derived from NM23-H2, is immunogenic and a potential candidate for specific immunotherapy of CML patients.

Description: The induction of a graft versus leukaemia (GvL) effect following allogenic hematopoietic stem cell transplantation (HSCT) is critical for the outcome in patients with hematological malignancies. Tumor-specific antigens as WT-1 are expressed on leukemic blasts and are major targets of the GvL effect. Therefore the generation of a WT-1 specific immune response through peptide vaccination could enhance the antileukemic effects after HSCT. In a phase I study five HLA A*0201 positive patients with high-risk AML (median age 64 yrs, range 33–67yrs) were vaccinated with the WT-1 derived peptide RMFPNAPYL (126–134) beginning at day 21 after HSCT. The vaccination protocol consisted in four biweekly vaccinations with the peptide in a dose of 0,2mg administered i.d. and s.c. with 1mg of keyhole limpet hemocyanin (KLH) as adjuvant. Concomitantly, patients received daily doses of GM-CSF (75μg/d) for four days beginning two days before vaccination. After the first four cycles, vaccine was administered monthly. When patients showed signs of GvHD or infection vaccination was discontinued. WT-1-specific T cell responses were monitored in peripheral blood using tetramer analysis. No severe acute toxicity attributable to the vaccination was observed. In all patients a local inflammatory response at the site of injection was detected, which resolved fast after ending of the vaccination cycle. In some patients a systemic inflammatory response with fever and increase of the leukocyte count were observed, which also resolved a few days after vaccination. Three patients achieved a complete remission of the AML after transplantation and did not relapse. One patient developed an intraneural relapse of the AML in the N. medianus of the left arm, which was successfully treated by irradiation. Though, she did not show a relapse in the bone marrow and maintains a full donor chimerism in bone marrow and peripheral blood 600 days after transplantation. One patient relapsed and died four months after transplantation. Two patients developed a grade I GvHD of the skin shortly after the first vaccination. Therefore vaccination was discontinued and resumed two weeks after resolution of the GvHD. No GvHD signs were observed after the subsequent vaccination cycles. One patient developed a grade III GvHD of the skin and gut after the 3rd vaccination. In this patient GvHD proved to be resistant to the common immunosuppressive agents and the patients died of septicaemia four months after transplant. One patient developed a three-system grade IV GvHD after the 2nd vaccination. Vaccination was then resumed after resolution of the GvHD. He unfortunately died in complete remission because of systemic aspergillosis ten months after transplant. In three patients WT-1 specific T cell responses were monitored in peripheral blood at different time points prior and after vaccination by tetramer analysis. Prior to vaccination none of the patients showed a positive response to WT1. In all these patients CD8+/WT1-specific T cells were detected after one (1/3, 0,66% tetramer binding CD8+ cells) or two vaccinations (2/3, 0,99% and 0,81% tetramer binding CD8+ cells, respectively). In accordance with our observations, WT1 vaccination could contribute to the maintenance of a complete remission in patients with high-risk AML after HSCT. However, it could enhance GvH reactions because of the adjuvants used. Therefore further clinical observations in a larger number of patients are needed.

Description: Background: Recent data suggest that NK cell mediated antibody dependent cellular cytotoxicity (ADCC) is a major mechanism of action of the anti-CD20 monoclonal antibody (mAb) rituximab and the anti-CD52 mAb alemtuzumab, which are frequently applied in patients with non-Hodgkin’s lymphoma and chronic lymphocytic leukemia. However, the exact mechanisms leading to NK cell activation are not completely understood and the cytotoxic subpopulation of peripheral blood NK cells mediating ADCC remains to be defined. In order to quantify and characterize the NK cells mediating ADCC, we used a novel flow cytometric assay, which detects the lytic granule membrane protein CD107a as a marker for NK cell degranulation. Methods: PBMCs from healthy individuals were coincubated at 37°C for 3 h with different human leukemia and lymphoma cell lines. In each tube, containing 200μl effector/target suspension (4x105 cells), 15μl of PE-Cy5 conjugated anti-CD107a monoclonal antibody was added prior to incubation. To assess antibody dependent cellular cytotoxicity (ADCC) saturating concentrations (10μg/ml) of rituximab or alemtuzumab were used. After the first 1 h 5μl of the secretion inhibitor 2 mM monensin was added. At the end of coincubation cells were stained with mAbs (CD56, CD3, NKG2D, CD69, CD94, NKp30, NK46) for flow cytometry. NK cell-mediated cytotoxicity (specific lysis) was analyzed by flow cytometric detection of propidium iodide uptake. Results: After coincubation with NK sensitive K562 cells up to 6% of CD56+ cells expressed CD107a, indicating that a subpopulation of NK cells releases cytotoxic granules after contact with these target cells. In contrast, coincubation with NK-resistant leukemia cells (ML2, EHEB, DAUDI, RAJI, AM0-1, YT-1) was not followed by an increased surface expression of CD107a. However, when rituximab was added to CD20+ lymphoma or leukemia cells (EHEB, DAUDI, RAJI) we observed that up to 15% of NK cells expressed CD107a after coincubation. In contrast no increased CD107a surface expression was observed when rituximab was added to the CD20− cell lines AMO-0 and YT-1, which excludes unspecific NK cell activation. When alemtuzumab was added to the CD52+ cell lines AMO-1, DAUDI, EHEB, RAJI and YT-1, surface expression of CD107a on NK cells was increased considerably. The majority of degranulating NK cells had the phenotype: CD56dim, CD69+, NKG2D+, NKp30−, NKp46− and CD94−. Furthermore we found that the CD107a assay can also visualize ADCC under clinical conditions as we observed increased numbers of NK cells degranulating in response to CD20+ lymphoma cell lines in patients with non-Hodgkin’s lymphoma treated with rituximab. The number of degranulating NK cells was closely related to the concentration of rituximab and the effector:target ratio, showing a maximum at a ratio of 1:1 and concentrations above 5μg/ml. CD107a surface expression and specific lysis demonstrated a strong positive correlation (r2 = 0.99), confirming that NK cell cytotoxicity can be assessed by this method. Conclusion: The CD107a assay represents a promising new method not only for assessment of natural cytotoxicity on a single cell level but also for determination of ADCC in vitro and in patients treated with mAb. In clinical practice, it may help to find optimal doses and time schedules for the treatment with different mAbs.

Description: To improve the antileukemic effectiveness of haploidentical stem cell transplantation (HSCT) and strengthen the cell mediated immune response, we have adoptively transferred high numbers of alloreactive donor NK cells during the early phase after transplantation. In addition, we activated the transferred NK-cell population ex vivo in short term cultures with high doses of IL-2 in order to enhance the antileukemic activity and inhibit the occurrence of severe GvHD. Method: In a phase-II study, 17 patients (10 AML, 1 MDS, 1 HD, 2 CML, 3 ALL, median age 37 yrs, range 17–48 yrs) were transplanted in late phases of their disease (6 pts. as 2nd transplantation) and received purified NK cells from their haploidentical donors at day +2 after HSCT. Conditioning consisted of 12 Gy fTBI, Thiotepa (10mg/kg), Fludarabine (5 x 30 mg/qm) and OKT3 (day −4 to +2). NK cells were isolated from the CD34- fraction using an automated two-step procedure of CD3+ depletion and subsequent CD56+ selection. Seven patients received activated NK cells and 10 patients received unstimulated NK cells. Cells were activated by 16h incubation with IL-2 (500U/1x107 cells). Results: After selection and subsequent overnight activation of the NK cells with IL-2 (7 out of 17 patients), a mean number of 8.3 x 106/kg CD56+CD3− NK cells was transferred at day 2 after transplantation. The purity was 76%, due to contaminating CD56+ monocytes. The mean number of contaminating CD3+ cells in the transfused NK product was 2.1 x 104/kg. Activation of donor NK cells with IL-2 resulted in an increase of cytotoxic activity, when cells were tested against target cell lines. No differences in yield or number of contaminating T cells were observed between IL-2 activated and not activated NK cells. No severe acute toxicity attributable to NK cell infusion was observed in both groups of patients. Comparing the rate of high-grade GvHD revealed an interesting result. Whereas only one patient developed GvHD ≥ grade II after treatment with IL-2 activated NK cells, seven out of ten patients showed GvHD ≥ grade II after transfer of non-activated NK cells (p

Description: Abstract 2370 Regardless of the treatment applied, the outcome for patients with refractory hematological malignancies is extremely poor. For haploidentical stem cell transplantation (haploSCT), which has been evaluated especially in high-risk AML patients lacking an HLA-identical donor, registry data show an overall survival below 10% for AML not transplanted in remission. In order to improve immune competence and to reduce the risk of relapse, we have combined the early transfer of NK cells with the haploSCT approach. PATIENTS AND METHODS: Twenty-five patients (AML = 16, ALL = 5, CML = 2, Hodgkin = 1, MDS = 1) received a haploSCT followed by transfer of purified CD56+CD3-NK cells at day +2. Conditioning consisted of total body irradiation, thiotepa, fludarabine, and OKT3. NK cells were isolated from the CD34- fraction using an automated two-step procedure of CD3+ depletion and subsequent CD56+ selection. No other immunosuppression was routinely delivered. RESULTS: Patients received a mean of 13.3 × 106 CD34+ cells/kg (range 6.12–26.97) with 2.89 × 104/kg (0.95-7.4) contaminating CD3+ cells. A mean of 9.8 × 106 CD56+CD3- NK cells/kg (range 1.61–32.2) was adoptively transferred. Most of the patients developed early GVHD of the skin (median onset day=12), which promptly resolved after short term treatment with steroids and CSA. The main cause of death consisted of infections (n = 10), chronic GvHD (n= 2), and relapse (n = 4). After a median follow-up of 1442 days (3.9 years) (range 0.1 to 7.1 years) 9 of 25 patients are alive and in complete remission resulting in a 2-year overall survival (OS) estimate of 29%. Out of 16 high-risk patients with AML, 10 had refractory or active disease prior to transplantation. For a matched pair analysis, these patients were matched for age, disease status, conditioning regimen and year of transplantation using the EBMT database. AML patients treated with haploSCT plus NK cell transfer had a superior 2-year overall survival (40 vs 11%, 95% CI) in comparison to matched controls with haploSCT only (p=0.02) CONCLUSIONS: HaploSCT plus NK cells is feasible and shows promising survival rates for a group of patients lacking other treatment options. Best results were achieved in patients with AML not only in remission but also with refractory disease. Disclosures: No relevant conflicts of interest to declare.

Description: Background: After allogeneic SCT, NK cell mediated cytotoxicity is an important defense mechanism against residual tumor cells and viral infections. Using a novel flow cytometric assay, which detects the lytic granule membrane protein CD107a as a marker for NK cell degranulation, we investigated the effect of in vivo T cell depletion and the type of conditioning on NK cell function in the early phase after transplantation. Methods: At day +30 and day +90 after allogeneic SCT with regular (n=14) and dose reduced conditioning (n=8), PBMCs were coincubated at 37°C for 3 h with the NK sensitive cell line HL60. 20μl of PE-Cy5 conjugated anti-CD107a monoclonal antibody (moAb) was added to each tube containing 400μl effector/target cell suspension (2x106 cells, E:T ratio 1:1) prior to incubation. After 1 hour, 10μl of monensin (2mM) was added. After incubation for 3 hours, the cells were stained with conjugated moAb (CD56, CD16, CD3) for flow cytometry. The percentage of CD107a expressing NK cells was assessed and the absolute number of degranulating NK cells /μl was calculated. Results were compared to values from 15 healthy controls. Results: Twenty two patients (pts.) were investigated. Fourteen pts. received a conventional conditioning regimen and eight a reduced intensity conditioning. T cell depletion was applied in 15/22 pts. (ATG n=12, alemtuzumab n=2, 1 OKT-3 n=1). The type of donor included MRD (n=7) and MUD (n=15). At day +30, the proportion of NK cells with cytotoxic activity (indicated by the mean percentage of degranulating CD107a+/CD56+ cells) was significantly reduced as compared to normal donors (2.6% vs. 5.6%, p

Description: Background: It is hypothesized that enhanced graft-versus-leukemia activity of natural killer (NK) cells contributes to the clinical efficacy of non-myeloablative allogeneic hemotopoietic stem cell transplantation (HSCT). We compared NK cell cytotoxic activity after transplantation with full and reduced dose regimens with normal values obtained from healthy volunteers. Methods&Material: Using a flow cytometric assay that detects CD107a expression after coincubation with leukemia cell lines as a marker for NK cell degranulation we prospectively quantified and characterized NK cells mediating anti-tumor activity in patients after HSCT. Mononuclear cells (MNC) were isolated from peripheral blood of 17 healthy individuals and 31 patients transplanted with G-CSF mobilized peripheral blood stem cells at day +30. MNC were incubated with leukemia cell lines HL60 and K562 (effector/target ratio 1:1) and expression of CD107a was measured after 3 hours. The absolute number of degranulating (CD107a+) NK cells was calculated. Results: Thirty one patients (five with ALL, four with NHL, one with Aplastic Anemia and 21 with AML) were enrolled, of whome 22 were transplanted from a matched related donor, seven from a matched unrelated donor, and two from a haploidentical donor. Nine patients had been transplanted after conditioning with 2 Gy TBI only, whereas 22 patients had received various conventional dose regimens. NK cell counts at day +30 after HSCT with conventional conditioning were comparable to normal values, but percentage and number of degranulating cells were significantly reduced (2.4% and 7/μl vs. 6.2% and 18/μl; p