Hu8F4-CAR T cells with mutated Fc spacer segment improve target-specificity and mediate anti-leukemia activity in vivo

Hu8F4 is a T cell receptor (TCR)-like antibody with high affinity for leukemia-associated antigen PR1/HLA-A2 epitope. Adapted into a chimeric antigen receptor (CAR) format, Hu8F4-CAR is comprised of the Hu8F4 scFv, the human IgG1 CH2CH3 extracellular spacer domain, a human CD28 costimulatory domain, and the human CD3ζ signaling domain. We have demonstrated high efficacy of Hu8F4-CAR-T cells against PR1/HLA-A2-expressing cell lines and leukemic blasts from AML patients in vitro. Previous studies have shown that modification of the Fc domains of IgG4 CH2CH3 spacer regions can eliminate activation-induced cell death and off-target killing mediated by mouse Fc gamma receptor (FcgR)-expressing cells. We generated Hu8F4-CAR(PQ) with mutated Fc receptor binding sites on the CH2 domain of Hu8F4-CAR to prevent unwanted interactions with FcgR-expressing cells in vivo. The primary human T cells transduced with Hu8F4-CAR(PQ) can specifically lyse HLA-A2+ PR1-expressing leukemia cell lines in vitro. Furthermore, both adult donor-derived and cord blood-derived Hu8F4-CAR(PQ)-T cells are active and can eliminate U937 leukemia cells in NSG mice. Herein, we demonstrate that modification of the IgG1-based spacer can eliminate Fc receptor-binding-induced adverse effects and Hu8F4-CAR(PQ)-T cells can kill leukemia in vivo.

Third-Party BK Virus-Specific Cytotoxic T Lymphocyte Therapy for Hemorrhagic Cystitis Following Allotransplantation

PURPOSE

BK virus-associated hemorrhagic cystitis (BKV-HC) is a common complication of allogenic hematopoietic stem cell transplantation (AHSCT), particularly in recipients of alternative donor transplants, which are being performed in increasing numbers. BKV-HC typically results in painful hematuria, urinary obstruction, and renal dysfunction, without a definitive therapeutic option.

METHODS

We performed a clinical trial (ClinicalTrials.gov identifier: NCT02479698) to assess the feasibility, safety, and efficacy of administering most closely HLA-matched third-party BKV-specific cytotoxic T lymphocytes (CTLs), generated from 26 healthy donors and banked for off-the-shelf use. The cells were infused into 59 patients who developed BKV-HC following AHSCT. Comprehensive clinical assessments and correlative studies were performed.

RESULTS

Response to BKV-CTL infusion was rapid; the day 14 overall response rate was 67.7% (40 of 59 evaluable patients), which increased to 81.6% among evaluable patients at day 45 (40 of 49 evaluable patients). No patient lost a previously achieved response. There were no cases of de novo grade 3 or 4 graft-versus-host disease, graft failure, or infusion-related toxicities. BKV-CTLs were identified in patient blood samples up to 3 months postinfusion and their in vivo expansion predicted for clinical response. A matched-pair analysis revealed that, compared with standard of care, after accounting for prognostic covariate effects, treatment with BKV-CTLs resulted in higher probabilities of response at all follow-up timepoints as well as significantly lower transfusion requirement.

CONCLUSION

Off-the-shelf BKV-CTLs are a safe and effective therapy for the management of patients with BKV-HC after AHSCT.

Abstract 1516: Deep profiling of T-cell repertoire and tumor heterogeneity in chronic lymphocytic leukemia patients following allogeneic T-cell therapy

Chemotherapy/ targeted therapy are both known to trigger evolution of treatment resistant clones that can lead to relapse. Allogeneic stem cell transplant (alloSCT) for refractory Chronic Lymphocytic Leukemia (CLL) patients is associated with better outcomes. We hypothesized that allogeneic T-cell immunotherapies, including alloSCT and donor lymphocyte infusion (DLI) would impact tumor evolution through the application of selective immunologic pressure with reciprocal changes in the T-cell compartment. Here, we tested a cohort of 24 heavily pre-treated CLL patients treated. Treatments consisted of alloSCT alone, or with follow-up DLI, which are two established mediators of effective Graft versus Leukemia (GVL). Our cohort included 11 patients who relapsed (denoted as non-responder, NR) after alloSCT and 13 patients who had complete response (CR) after alloSCT, with 11/13 patients showing durable CR with a median post-transplant overall survival (OS) of 9.8 years. We mapped the evolutionary trajectories of tumor cells by whole exome sequencing (WES) of sort purified CLL in post-transplant relapsed patients. To investigate changes in immune repertoire and gene expression post-transplant, CD3 positive T-cells from peripheral blood and bone marrows of CLL patients at complete donor chimerism were analyzed both at bulk and at the single cell level. We found evidence of subclonal leukemic evolution in the majority of our CLL patient cohort after nonmyeloablative HLA-matched alloSCT. Different patterns of CLL evolution were observed, and these changes included putative CLL drivers in every case. In all of the 11 patients with longitudinal post-alloSCT samples available, we observed branched CLL evolution in 4 patients, linear evolution in 4 patients, and no evolution in 3 patients. These data suggest that differential sensitivity of leukemic subclones to allogeneic T cell killing may underlie the branched and linear evolution that we observed, and therefore can shape leukemic subclonal architecture after transplant. Of note, we found that clonal CLL was more responsive to alloSCT in comparison to CLL with subclonal disease architecture.To identify T-cells with GVL potential, we first cataloged potential neoantigens by screening mutated regions in CLL with in silico HLA binding prediction models. Neoantigen specific T-cells were then sorted from longitudinal peripheral blood samples using tetramers, followed by identification of GVL specific TCR in both bulk and single cell setting. We were able to identify T-cells that coevolved with specific tumorigenic lesions in a subset of CLL patients. Taken together, our results suggest that donor-derived antigen-specific T-cells mediate clonal selection of CLL with concurrent changes in allogeneic T-cells, and that these changes can be monitored in longitudinal patient samples.

Citation Format: Celine Kerros, John P. Miller, Xizeng Mao, Haven R. Garber, Hannah C. Beird, Jianhua Zhang, Jason Roszik, Paul Leonard, Li Zhao, Sahil Seth, Pei Lin, Huandong Sun, William G. Wierda, Issa F. Khouri, Karen Clise-Dwyer, Andrew Futreal, Shoudan Liang, Koppikar Priya, Jeffrey Molldrem. Deep profiling of T-cell repertoire and tumor heterogeneity in chronic lymphocytic leukemia patients following allogeneic T-cell therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1516.

Rapid ex vivo expansion of highly enriched human invariant natural killer T cells via single antigenic stimulation for cell therapy to prevent graft-versus-host disease

BACKGROUND AIMS

CD1d-restricted invariant natural killer (iNK) T cells are rare regulatory T cells that may contribute to the immune-regulation in allogeneic stem cell transplantation (ASCT). Here, we sought to develop an effective strategy to expand human iNK T cells for use in cell therapy to prevent graft-versus-host disease (GVHD) in ASCT.

METHODS

Human iNK T cells were first enriched from peripheral blood mononuclear cells (PBMCs) using magnetic-activated cell sorting separation, then co-cultured with dendritic cells in the presence of agonist glycolipids, alpha-galactosylceramide, for 2 weeks.

RESULTS

The single antigenic stimulation reliably expanded iNK T cells to an average of 2.8 × 10⁷ per 5 × 10⁸ PBMCs in an average purity of 98.8% in 2 weeks (N = 24). The expanded iNK T cells contained a significantly higher level of CD4⁺ and central memory phenotype (CD45RA^-CD62L⁺) compared with freshly isolated iNK T cells, and maintained their ability to produce both Th-1 (interferon [IFN]γ and tumor necrosis factor [TNF]α) and Th-2 type cytokines (interleukin [IL]-4, IL-5 and IL-13) upon antigenic stimulation or stimulation with Phorbol 12-myristate 13-acetate/ionomycin. Interestingly, expanded iNK T cells were highly autoreactive and produced a Th-2 polarized cytokine production profile after being co-cultured with dendritic cells alone without exogenous agonist glycolipid antigen. Lastly, expanded iNK T cells suppressed conventional T-cell proliferation and ameliorated xenograft GVHD (hazard ratio, 0.1266; P < 0.0001).

CONCLUSION

We have demonstrated a feasible approach for obtaining ex vivo expanded, highly enriched human iNK T cells for use in adoptive cell therapy to prevent GVHD in ASCT.

Abstract 5612: Evaluating the cytotoxic effectiveness of a novel TCR-like bispecific T cell engager targeting the PR1/HLA-A2 leukemia antigen

Overall 5-year survival rates of myeloid leukemia patients remain low at &lt;30%, and new therapies for these patients are desperately needed. PR1 (VLQELNVTV) is a human leukocyte antigen (HLA)-A2 restricted peptide derived from serine proteases proteinase-3 and neutrophil elastase, which are aberrantly expressed in myeloid leukemia blasts, including acute myelogenous leukemia (AML). PR1 was shown to be immunogenic in myeloid malignancies, and we have conducted preclinical development and humanization of a T cell receptor-like monoclonal antibody (h8F4) that targets the leukemia-associated PR1/HLA-A2 complex and eliminates AML xenografts by antibody-dependent cellular cytotoxicity (ADCC) following repeat dosing. To improve the potency of h8F4, we have developed a bispecific T cell-engaging antibody that targets PR1/HLA-A2 on leukemia and CD3 on neighboring T cells. Here we demonstrate successful production and purification of the h8F4 bispecific antibody. Utilizing flow cytometry, we confirm PR1/HLA-A2 and CD3-specific binding characteristics, T cell activation in the presence of PR1/HLA-A2, and importantly AML target cell cytotoxicity after h8F4 bispecific antibody engagement with healthy donor effector T cells. Cytotoxicity assays were performed with both AML cell lines and primary patient AML blasts serving as target cells and health donor PBMC as a source of effector T cells at an E:T ratio of 2:1. Results indicate up to 60% leukemia-specific lysis with 2nM h8F4 bispecific antibody after only 18 hours of incubation. In vivo data also confirm significant elimination of the leukemia cell line U937 (as evidenced by % leukemia cells detected in peripheral blood) in an NSG-U937 AML xenograft mouse model when compared to control groups treated with effector cells alone. Mice were infused with 5,000 leukemia cells followed by 3 million normal healthy donor PBMC. These infusions were followed by a week of daily h8F4 bispecific antibody injections (20ng/injection). Both bioluminescence and flow cytometry analysis two weeks following the final injection show a marked difference between the h8F4 bispecific antibody treatment group and controls, with a 1.5-fold reduction in circulating leukemia cells and an overall increase in survival. In conclusion, these studies demonstrate the therapeutic potential of a novel bispecific antibody targeting the PR1/HLA-A2 leukemia-associated antigen. This bispecific antibody appears to increase the potency of h8F4 with rapid elimination of AML compared to h8F4, and our studies justify potential development as a treatment option for patients with high-risk AML.

Citation Format: Amanda Cernosek Herrmann, Jin Seon Im, Hong He, Sergueeva Anna, Sijie Lu, Jeffrey Molldrem. Evaluating the cytotoxic effectiveness of a novel TCR-like bispecific T cell engager targeting the PR1/HLA-A2 leukemia antigen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5612.

Concise review: umbilical cord blood transplantation: past, present, and future

Allogeneic hematopoietic stem cell transplantation is an important treatment option for fit patients with poor-risk hematological malignancies; nevertheless, the lack of available fully matched donors limits the extent of its use. Umbilical cord blood has emerged as an effective alternate source of hematopoietic stem cell support. Transplantation with cord blood allows for faster availability of frozen sample and avoids invasive procedures for donors. In addition, this procedure has demonstrated reduced relapse rates and similar overall survival when compared with unrelated allogeneic hematopoietic stem cell transplantation. The limited dose of CD34-positive stem cells available with single-unit cord transplantation has been addressed by the development of double-unit cord transplantation. In combination with improved conditioning regimens, double-unit cord transplantation has allowed for the treatment of larger children, as well as adult patients with hematological malignancies. Current excitement in the field revolves around the development of safer techniques to improve homing, engraftment, and immune reconstitution after cord blood transplantation. Here the authors review the past, present, and future of cord transplantation.

Abstract 646: Bi-specific T-cell engaging antibody activates T-cells to target the tumor associated antigen PR1

Acute (AML) and chronic (CML) myeloid leukemia together account for approximately 50% of newly diagnosed leukemias. Both AML and advanced CML have dismal survival outcomes but are susceptible to immunotherapy. We discovered PR1 (VLQELNVTV) as an effective human leukocyte antigen (HLA)-A2 restricted peptide and have targeted it in clinical trials using PR1 peptide vaccine. PR1 is derived from the serine proteases proteinase-3 and neutrophil elastase which are highly expressed in myeloid leukemia blasts. PR1 was shown to be immunogenic in myeloid malignancies, and we are currently developing several PR1 targeting therapies. We have completed the development and humanization of a T-cell receptor-like monoclonal antibody (h8F4) that targets PR1/HLA-A2 and eliminates primary human AML xenografts in NSG mice. To improve the efficacy of h8F4, we have developed a bi-specific T-cell engaging (BiTE) antibody that targets leukemia PR1/HLA-A2 and the T-cell receptor CD3. This would enhance the anti-leukemia immune response by bringing the T-cell in close proximity to the leukemia cell, and by further activating the T-cells to eliminate the target leukemia. Here we demonstrate successful construction and expression of the h8F4 BiTE in CHO cells. The antibody was purified from cell culture supernatant via Ni-NTA column chromatography, and identity was confirmed using western blot analysis. Next, flow cytometry was used to test the binding specificities of each targeting region of the BiTE antibody. The h8F4 BiTE antibody showed increased binding to T2 cells pulsed with PR1 peptide compared with T2 pulsed with irrelevant CMV peptide pp65 (MFI=627 and 72.4, respectively). In addition, the h8F4 BiTE demonstrated 6.8 fold higher binding to wild type Jurkat cells, which express CD3, in comparison with the CD3-lacking mutant Jurkat cell line J.RT3-T3.5. These results indicate that both regions of the h8F4 BiTE can efficiently recognize their intended targets. Next, we investigated whether h8F4 BiTE engagement with both PR1/HLA-A2 on T2 cells and CD3 on healthy donor PBMC could activate T-cells. We show with flow cytometry that upon 24h incubation in the presence of h8F4 BiTE and T2 cells pulsed with PR1 peptide, both CD4 and CD8 T-cells increase their surface expression of CD69 (21 fold in CD4; 10.3 fold in CD8), CD25 (35 fold in CD4; 3.5 fold in CD8) and CD71 (26.6 fold in CD4; 640 fold in CD8) compared to co-incubation in the absence of BiTE protein. In conclusion, this study shows that we have successfully developed a h8F4 BiTE which recognizes both the CD3 on T cells and PR1/HLA-A2 complexes on myeloid leukemia. Furthermore, the h8F4 BiTE can activate multiple T-cell subsets from healthy donor PBMC as early as 24h following co-incubation with PR1-pulsed T2 cells. This novel BiTE antibody could provide a safer and more potent treatment option for patients with aggressive myeloid leukemias that will improve upon currently available highly toxic standard therapies.

Citation Format: Amanda Herrmann, Jin Im, Sijie Lu, Jeffrey Molldrem. Bi-specific T-cell engaging antibody activates T-cells to target the tumor associated antigen PR1. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 646. doi:10.1158/1538-7445.AM2014-646

PR1-specific cytotoxic T lymphocytes expanded from cord blood are functional in vitro (VAC11P.1002)

Introduction Neutrophil elastase (NE) and proteinase 3 (P3) are serine proteases often found overexpressed in myeloid leukemic cells. PR1 is a nine amino acid, HLA-A2 restricted peptide derived from NE and P3. The frequency of PR1-specific T cells (PR1-CTL) is very low in healthy adult peripheral blood (0.0005 to 0.05% of CD8+ T cells), but much higher in umbilical cord blood (UCB) (0.007 to 0.345% of CD8+ T cells, N=57). We have previously shown sort-purified UCB PR1-CTL to be active against AML in a murine model. We now investigate the potential of UCB PR1-CTL to undergo expansion while maintaining the anti-leukemic properties of the cells. Methods HLA-A*0201 transfected K562 cells were loaded with PR1 peptide and irradiated with 3000 cGy. UCB mononuclear cells were stimulated with K562/A2/PR1 cells once a week for three weeks. CD8+ T cells were then negatively isolated from the expanded population by magnetic beads and underwent intracellular cytokine staining. Results Prior to expansion, the median percentage of PR1-CTL in the 9 UCB units tested was 0.211% (0.00%-0.348%) of CD8+ T cells. After stimulation this percentage increased to 0.958% (0.346%-2.1%). The expanded UCB PR1-CTL was of memory phenotype (CD45RA-/CCR7-). In addition, expanded UCB PR1-CTL produced both IFN-γ and TNF-α in response to PR1 peptide-loaded T2 cells. Conclusion PR1-CTL can be expanded from UCB and these expanded cells produce cytokines in a specific manner in response PR1-peptide loaded targets.

PR1-CTL directly sort-purified from umbilical cord blood lymphocytes reduce human AML in vivo. (P4360)

Adoptive transfer of leukemia specific CTL could prove to be a valuable tool in the prevention and/or treatment of relapse after SCT. In line with this, we chose to examine the use of PR1-specific CTL derived from UCB as a means of adoptive immunotherapy for leukemia. PR1, a 9 amino acid, HLA-A2-restricted self-peptide is well established as a dominant LAA. While cells specific for PR1 are present in the peripheral blood of healthy adults at extremely low frequencies (0.0005 to 0.05% of CD8+ T cells), we have found that the frequency of PR1-CTL in UCB is significantly higher ranging from 0.007 to 0.345% (mean 0.117%; n=57) of CD8+ cells. We hypothesized that these cells could be isolated directly from UCB via cell sorting and used in the prevention or treatment of leukemia. CD8 enriched cells were sorted and then activated ex vivo with anti-CD3/anti-CD28/IL-2. Sorted, activated cells were infused into a cohort of NSG mice with established leukemia. In three separate, but comparable, experiments the frequency of leukemia cells in the bone marrow of mice receiving PR1-specific CTL was reduced by 27% (range 21%-32%) compared to those receiving no treatment, and 23% (range 4%-47%) compared to those receiving non-specific CD8+ cells. The reduction of leukemia cells in the blood was even more pronounced with a 47% (range 45%-61%) decrease compared to the level seen in mice receiving PBS alone, and 58% (range 48%-68%) compared to mice receiving non-specific CD8+ cells.

A high frequency of naïve PR1-specific CD8+ T cells in umbilical cord blood and fetal thymus suggest incomplete central tolerance to the hematopoietic self-antigen PR1. (46.24)

Tolerance to self-antigens is established primarily in the thymus by negative selection. We have evidence that central tolerance to the HLA-A2 restricted self-peptide, PR1, is incomplete. The frequency of PR1-CTL in umbilical cord blood (UCB) is significantly higher than that seen in the peripheral blood of healthy adults. Investigation in fetal thymic tissue (FT) showed that PR1 is expressed on the surface of thymic dendritic cells (DC) but not thymic epithelial cells. The level of PR1 expression on FT DC is similar to that on UCB DC and healthy adult DC. Comparisons of antigen-specific cells in FT and UCB demonstrated pp65-CTL frequencies were comparable, yet PR1- and WT1-CTL percentages were lower in UCB than in FT. PR1-specific cells, in contrast to pp65- and WT1-specific cells, were found at a higher frequency within CD8 single positive (SP) thymocytes versus CD4+CD8+ double positive (DP) cells, suggesting that PR1-specific SP thymocytes have a survival advantage relative to WT1- and pp65-specific SP thymocytes. In response to PR1 peptide-loaded T2 cells, DP PR1-CTL undergo apoptosis to a greater degree than SP PR1-CTL, implying that higher frequencies of SP PR1-CTL in FT could be due, in part, to a lower susceptibility of SP PR1-CTL to apoptosis. Our data suggest that PR1 expression by DC in the thymus is insufficient for complete central tolerance to PR1 and PR1-specific SP thymocytes may have a survival advantage over other self and viral antigen-specific thymocytes.

Abstract 801: Uptake of exogenous neutrophil elastase by breast cancer cells: A novel link between innate immunity, inflammation and breast cancer immunity

Introduction: High level of neutrophil elastase (NE) in tumor tissue from breast cancer (BrCa) patients is associated with poor metastasis-free survival. Modest endogenous expression of NE in some BrCa cell lines has also been observed. However, because the major source of NE is from azurophil granules of activated neutrophils, we hypothesized that breast cancer cells may take up soluble NE released by abundant inflammatory cells in the tumor microenvironment.

Methods: Endogenous NE expression was evaluated in MCF7, HER18, MDA-MB-231 (231) and MDA-MB-453 BrCa cell lines by western blot analysis and RT-PCR. Uptake of soluble NE was quantified by flow cytometry by intracellular staining of NE-pulsed BrCa and compared to non-specific uptake of OVA. Dose and time course experiments were performed. Confocal immunoflourescence microscopy was used to confirm uptake and demonstrate subcellular localization of NE. BrCa cells were also co-incubated with activated neutrophils to determine if they were able to take up cell-associated NE.

Results: Western blot analysis of BrCa cell lysates showed no NE protein expression in all 4 cell lines. Furthermore, RT-PCR with NE-specific primers demonstrated no NE mRNA expression in the 4 BrCa cell lines. However, BrCa cells pulsed with 5 to 25 μg/ml of soluble NE took up NE in a time and dose dependent manner, consistent with a receptor-mediated mechanism. Maximal intracellular uptake of NE by 231 cells occurred by 24 hours when NE accumulated at comparable levels to that of HL60 leukemia cells that express high levels of NE (987 vs 1300 MFI, p=ns). Uptake was enzyme-independent because it was not affected by alpha-1-antitrypsin, a protease inhibitor. Confocal microscopy demonstrated that NE accumulates in membrane bound compartments by 20 minutes after uptake, whereas there was no significant uptake of OVA by BrCa cells. Similarly, after co-incubation of 231 cells with activated neutrophils, significant uptake of NE was detected (p&lt;.001).

Conclusions: These data show that BrCa cells do not express NE but the cells take up extracellular NE by a receptor-mediated enzyme-independent mechanism. This establishes a novel link between NE, a naturally secreted mediator of inflammation and cell growth, and BrCa. Because neutrophils are the major source of NE and chronic inflammation by tumor-infiltrating neutrophils is associated with positive tumor growth, this suggests NE could mediate growth control of BrCa.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 801. doi:10.1158/1538-7445.AM2011-801

Abstract 788: Uptake and cross-presentation of the leukemia associated antigens neutrophil elastase (NE) and proteinase-3 (P3) increases susceptibility of solid tumors to PR1-targeted immunotherapy

We have shown that the HLA-A2-restricted nonapeptide PR1 (VLQELNVTV) is a leukemia-associated peptide derived from P3 and NE. Furthermore, immunologic and clinical responses to PR1 peptide vaccination occur in patients with acute (AML), chronic (CML) myeloid leukemia and myelodysplastic syndrome. We have also shown that PR1 expression results from NE and P3 cross-presentation by B-cells and dendritic cells. Because NE and P3 are present in lung and breast cancer tumor tissue, we investigated whether uptake of NE and P3 might result in PR1 expression on solid tumors, which could induce susceptibility of non-hematopoietic tumors to PR1-targeted immunotherapy. We studied melanoma, breast, ovarian and lung cancer cell lines to determine whether NE and P3 are cross-presented. Using flow cytometry, we show that numerous malignant cell lines take up 5 to 10 °g/ml of soluble NE and P3 and was dose- and time-dependent, consistent with a receptor-mediated mechanism. In addition to soluble NE and P3, uptake of granulocyte-associated NE and P3 was also demonstrated; however, uptake of soluble NE and P3 were 3- and 2-fold higher, when compared to granulocyte-associated proteins. Within 4 hours of uptake, confocal microscopy showed that soluble P3 localized to endosomes and lysosomes, suggesting the possibility of lysosomal degradation of P3, a common pathway for MHC-I processing of cross-presented proteins. With the use of 8F4, a monoclonal antibody that is specific for a PR1/HLA-A2 conformational epitope, we show that PR1/HLA-A2 is expressed by 12-hours on P3- and NE-pulsed HLA-A2+ melanoma and breast cancer cell lines. Because 8F4 mediates complement-dependent cytotoxicity (CDC) of AML, we studied whether PR1 expression induced susceptibility of P3- and NE-pulsed tumor cells to killing by 8F4 and PR1-CTL. Twelve hours after pulsing the HLA-A2+ breast cancer cell lines MDA-MB-453 and MDA-MB-231 with P3 or NE, up to 40% and 60% of pulsed breast cancer cells were lysed by PR1-CTL and 8F4, respectively. We conclude that PR1 is cross-presented by solid tumors following receptor-mediated uptake of soluble NE and P3 at concentrations observed in tumors and inflammatory sites. Importantly, this cross-presentation increased susceptibility of embryological distinct tumors to PR1-specific immunotherapy. Together, these data suggest that cross-presentation of extracellular inflammatory proteins that are normally not expressed in the tumor may be a mechanism shared by many tumors, which could be exploited by immunotherapy strategies targeting these proteins.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 788. doi:10.1158/1538-7445.AM2011-788

Aberrantly expressed neutrophil elastase (ELA2) in the nucleus and cytoplasm of acute lymphocytic leukemia (ALL) cells cleaves cyclin E (CCNE) into low-molecular-weight forms (LMWFs) yielding novel HLA-A2 restricted determinants (50.28)

We reported that CCNE-specific CTL elicited from healthy donors (HDs) kill ALL and CML cells, which aberrantly express CCNE. Further, 5 LMWFs of CCNE1 are present only in malignant cells and constitutively active to promote cell division. In addition, we showed ELA2-specific CTL also kill AML and CML, and ELA2 is normally expressed only in myeloid cells. To determine whether ELA2 might be aberrantly expressed in ALL and whether ELA2 cleaves CCNE to LMWF’s, we first found CCNE of LMWF to be overexpressed by western blot of cell lysates from ALL, but not from ALL in remission or HD B-cells. ELA2 added to ALL lysates increased LMWF’s and was inhibited by the ELA2 inhibitor elafin. Subcellular fractionation and co-immunoprecipitation showed ELA2 to be aberrantly associated with CCNE in nucleus, cytoplasm, and membrane-bound organelles in ALL, but not normal bone marrow cells. Because determinants recognized by CCNE-CTL are also found in the LMWFs and lysis of leukemia correlates with target protein overexpression, we studied the effect of induced CCNE expression on target susceptibility to cytolysis. While normal PBMC were not killed, PHA or α-CD3/28 stimulated PBMC were killed by CCNE-CTL, although non-specifically. We conclude that in ALL, aberrant expression of the myeloid protein ELA2 results in mistrafficking of ELA2 to cytoplasm and nucleus, thus mediating CCNE cleavage to LMWF’s and increasing susceptibility to CCNE-CTL killing. This shows novel tumor antigen interaction that may cooperatively reverse CTL tolerance.

In vivo expansion of LMP 1- and 2-specific T-cells in a patient who received donor-derived EBV-specific T-cells after allogeneic stem cell transplantation

Immunotherapy approaches with antigen-specific cytotoxic T lymphocytes (CTLs) have provided safe and effective prophylaxis and treatment of Epstein-Barr virus (EBV)-associated lymphomas arising after bone marrow transplantation. EBV is also associated with other malignancies including approximately 40% of cases of Hodgkin's disease, making this tumor another potential target for EBV-targeted immunotherapy. This study describes a patient with multiple relapsed EBV positive Hodgkin's Disease who received both autologous and allogeneic EBV CTL lines. After multiple chemotherapeutic and radiotherapy regimens including two autologous stem cell transplants, he received two doses of gene-marked autologous EBV-specific CTL which resulted in disease stabilization for 6 months. The gene-marked EBV-CTL persisted for 12 months in the peripheral blood after which he proceeded to unrelated donor stem cell transplant followed by immunotherapy with donor-derived EBV-specific CTL. Despite low levels of donor chimerism, the patient remains in complete remission 5 years post-allogeneic SCT. Comparison of the autologous and the donor-derived CTL lines showed that the donor line had specificity for two tumor-associated EBV antigens, latent membrane protein (LMP)1 and 2 compared to the autologous line, which only had specificity for LMP2 epitopes. Following infusion of the donor-derived CTL, functional analyses showed that T-cells reactive with both LMP1 and LMP2 epitopes expanded in the peripheral blood, suggesting that strategies to increase their frequency may result in a broader cytotoxic response against EBV+ Hodgkin tumors.

Ex vivo expanded umbilical cord blood T cells maintain naive phenotype and TCR diversity

BACKGROUND

Umbilical cord blood (CB) is a promising source of hematopoietic stem cells for allogeneic transplantation. However, delayed engraftment and impaired immune reconstitution remain major limitations. Enrichment of donor grafts with CB T cells expanded ex vivo might facilitate improved T-cell immune reconstitution post-transplant. We hypothesized that CB T cells could be expanded using paramagnetic microbeads covalently linked to anti-CD3 and anti-CD28 Ab.

METHODS

CB units were divided into three fractions: (1) cells cultured without beads, (2) cells cultured with beads and (3) cells cultured with beads following CD3+ magnetic enrichment. All fractions were cultured for 14 days in the presence of IL-2 (200 IU/mL).

RESULTS

A mean 100-fold expansion (range 49-154) of total nucleated cells was observed in the CD3+ magnetically enriched fraction. Following expansion, CB T cells retained a naive and/or central memory phenotype and contained a polyclonal TCR diversity demonstrated by spectratyping.

DISCUSSION

Our data provide evidence that naive and diverse CB T cells may be expanded ex vivo and warrant additional studies in the setting of human CB transplantation.

Prognostic factors for outcomes of patients with refractory or relapsed acute myelogenous leukemia or myelodysplastic syndromes undergoing allogeneic progenitor cell transplantation

Allogeneic progenitor cell transplantation is the only curative therapy for patients with refractory acute myelogenous leukemia or myelodysplastic syndromes. To identify prognostic factors in these patients, we performed a retrospective analysis of transplantation outcomes. Patients were selected if they had undergone an allogeneic transplantation between January 1988 and January 2002 and were not in remission or first untreated relapse at the time of transplantation. A total of 135 patients were identified. The median age was 49.5 years (range, 19-75 years). At the time of transplantation, 39.3% of patients had not responded to induction therapy, 37% had not responded to first salvage therapy, and 23.7% were beyond first salvage. Forty-one patients (30%) received unrelated donor progenitor cells. Eighty patients (59%) received either a reduced-intensity or a nonmyeloablative regimen. A total of 104 (77%) of 135 patients died, with a median survival time of 4.9 months (95% confidence interval, 3.9-6.6 months). The median progression-free survival was 2.9 months (95% confidence interval, 2.5-4.2 months). A Cox regression analysis showed that Karnofsky performance status, peripheral blood blasts, and tacrolimus exposure during the first 11 days after transplantation were predictive of survival. These data support the use of allogeneic transplantation for patients with relapsed or refractory acute myelogenous leukemia/myelodysplastic syndromes and suggest that optimal immune suppression early after transplantation is essential for long-term survival even in patients with refractory myeloid leukemias.

HLA-DR4 predicts haematological response to cyclosporine in T-large granular lymphocyte lymphoproliferative disorders

T-cell large granular lymphocytic lymphoproliferative disease (T-LGL) is often associated with life-threatening cytopenias. Twenty-five subjects with anaemia and/or neutropenia caused by T-LGL were treated with cyclosporin A (CSA) 5-10 mg/kg/d for at least 3 months. Eighteen patients survived between 35 and 77 months after starting treatment. Fourteen patients [56%; 95% confidence interval (CI) 35-76%] responded to CSA with sustained improvement in the neutrophil count or transfusion independence. Seven had complete normalization of blood counts, and four achieved a durable response only after the addition of erythropoietin. Sustained response required continued low-dose CSA. In a multivariate analysis, HLA-DR4 was highly predictive of CSA responsiveness (odds ratio 18; 95% CI 1.8-184). T-LGL subtype, LGL counts after therapy, lymphocytic marrow infiltration and bone marrow cellularity did not significantly affect the probability of response. We conclude that CSA is effective in inducing haematological responses in HLA-DR4-positive patients and that T-LGL is likely to have an immune pathogenesis.

T-cell large granular lymphocyte leukemia is characterized by massive TCRBV-restricted clonal CD8 expansion and a generalized overexpression of the effector cell marker CD57

INTRODUCTION

Large granular lymphocyte leukemia (LGL) is a clonal lymphoproliferative disease of CD8+ T cells expressing the CD57 activation marker. It is, however, unknown whether the CD57+ population represents the LGL clone or not. We previously demonstrated that the clone can be found in both CD8+CD57+ and CD8+CD57- cells, indicating that the LGL clone also resides in the CD57- fraction.

MATERIALS AND METHODS

Here, we quantified the extent of the clonal CD8 expansion in LGL using T-cell receptor Vbeta (TCRBV)-specific monoclonal antibodies, and determined whether the CD4 population also contained skews. Furthermore, dominant TCRBV populations were assessed for clonal status using T-cell receptor-gamma (TCRG) PCR on genomic DNA.

RESULTS

We show that the dominant TCRBV in LGL contains CD57+ and CD57- cells. Molecular analysis of CD8+CD57+ and CD8+CD57- subfractions of the dominant TCRBV by TCRG PCR demonstrates that indeed both fractions are clonal, and that the clone is absent from the dominant TCRBV-negative population. Furthermore, we show that CD57 overexpression is not restricted to the LGL clone, but a general phenomenon in CD8 cells of LGL patients.

CONCLUSION

We therefore conclude that the primary characteristic of LGL is a clonal expansion of CD8 cells, with a concomitant upregulation of CD57 on this clone and uninvolved cells.

Nonmyeloablative preparative regimens for allogeneic hematopoietic transplantation. Biology and current indications

High-dose myeloablative therapy with allogeneic hematopoietic transplantation is an effective treatment for hematologic malignancies, but this approach is associated with a high risk of complications. The use of relatively nontoxic, nonmyeloablative, or reduced-intensity preparative regimens still allows engraftment and the generation of graft-vs-malignancy effects, is potentially curative for susceptible malignancies, and reduces the risk of treatment-related morbidity. Two general strategies along these lines have emerged, based on the use of (1) immunosuppressive chemotherapeutic drugs, usually a purine analog in combination with an alkylating agent, and (2) low-dose total body irradiation, alone or in combination with fludarabine (Fludara).

Fludarabine/melphalan conditioning for allogeneic transplantation in patients with multiple myeloma

The purpose of the study was to determine the feasibility and efficacy of a reduced intensity conditioning regimen of fludarabine and melphalan for allogeneic transplantation in patients with multiple myeloma. From August 1996 to December 2000, 22 patients received a reduced intensity conditioning regimen with fludarabine and melphalan. Median age was 51 years (range, 45-64), median time from initial therapy to transplant was 36 months (range, 3-135 months). Disease phase prior to transplant was primary refractory in two patients, refractory relapse in 11 patients, sensitive relapse in eight patients and initial remission consolidation in one patient. The median number of prior therapies was five (range, 1-7), and median beta 2 microglobulin prior to transplant was 3.0 mg/l (range, 1.0-7.3). All patients received unmanipulated grafts from either HLA matched sibling donors (n = 13) or matched unrelated donors (n = 9). Eighteen patients received fludarabine 30 mg/m(2) for 4 days with melphalan 140 mg/m(2) as a single dose and four patients received fludarabine 25 mg/m(2) for 5 days with melphalan 90 mg/m(2) daily for 2 days. All 21 patients evaluable for engraftment achieved a neutrophil count of >0.5 x 10(9)/l after a median of 12 days (range, 9-24), 18 patients achieved platelet transfusion independence after a median of 14 days (range, 8-47). All engrafting patients had 100% donor cell engraftment. Seven patients achieved a complete remission. Six patients are currently alive with a median follow-up of 15 months (range, 10-47 months). The actuarial survival and progression-free survival is 30 +/- 11% and 19 +/- 9% at 2 years. Non-relapse mortality at 100 days was 19 +/- 10% and 40 +/- 10% at 1 year. Fludarabine/melphalan combinations are feasible and allow consistent engraftment of allogeneic progenitor cells from both related and unrelated donors in patients with multiple myeloma and should be explored in patients with less advanced disease.

HLA-DR15 (DR2) is overrepresented in myelodysplastic syndrome and aplastic anemia and predicts a response to immunosuppression in myelodysplastic syndrome

The extent and importance of autoimmune mechanisms in myelodysplastic syndrome (MDS) and the role of immunosuppression in the treatment of this disease are not well defined. We report overrepresentation of HLA-DR2 and its serologic split HLA-DR15 in both MDS and aplastic anemia (AA). Four clinically and ethnically defined patient groups were analyzed. The HLA-DR15 antigen frequencies among North American white MDS patients (n = 72) and AA patients (n = 59), who received immunosuppressive treatment at the National Institutes of Health (NIH), were 36% and 42%, respectively. These antigen frequencies were significantly higher than that of the control population of 240 North American white NIH blood donors typed for HLA antigens by the same molecular technique (HLA-DR15, 21.3%, P =.01 for MDS, P <.001 for AA). Among North American white patients reported in the International Bone Marrow Transplant Registry (IBMTR), 30% of 341 MDS patients and 33% of 364 AA patients were positive for HLA-DR2. These antigen frequencies were higher than those reported for the general North American white population (HLA-DR2, 25.3%, P =.089 for MDS, P =.01 for AA). The DR15 and DR2 frequencies were significantly increased in MDS refractory anemia (RA) (P =.036 and P =.01, respectively) but not MDS refractory anemia with excess blasts. In the NIH MDS patients, HLA-DR15 was significantly associated with a clinically relevant response to antithymocyte globulin (ATG) or cyclosporine immunosuppression (multivariate analysis, P =.008). In MDS with RA, DR15 may be useful as a guide to pathophysiology, prognosis, and treatment.

Diagnostic utility of flow cytometric immunophenotyping in myelodysplastic syndrome

The myelodysplastic syndromes (MDSs) are characterized by bilineage or trilineage dysplasia. Although diagnostic criteria are well established for MDS, a significant number of patients have blood and bone marrow findings that make diagnosis and classification difficult. Flow cytometric immunophenotyping is an accurate and highly sensitive method for detection of quantitative and qualitative abnormalities in hematopoietic cells. Flow cytometry was used to study hematopoietic cell populations in the bone marrow of 45 patients with straightforward MDS. The results were compared with those obtained in a series of patients with aplastic anemia, healthy donors, and patients with a history of nonmyeloid neoplasia in complete remission. The immunophenotypic abnormalities associated with MDS were defined, and the diagnostic utility of flow cytometry was compared, with morphologic and cytogenetic evaluations in 20 difficult cases. Although morphology and cytogenetics were adequate for diagnosis in most cases, flow cytometry could detect immunophenotypic abnormalities in cases when combined morphology and cytogenetics were nondiagnostic. It is concluded that flow cytometric immunophenotyping may help establish the diagnosis of MDS, especially when morphology and cytogenetics are indeterminate. (Blood. 2001;98:979-987)

Nonmyeloablative preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic transplantation is an effective therapy for a range of malignancies. High doses of myelosuppressive chemotherapy or radiation have been used in preparative regimens with the goal of preventing graft rejection and eradicating malignancy. Much of the benefit of transplantation, however, results from graft-versus-malignancy effects, mediated by donor immunocompetent cells. An alternative approach is to utilize less toxic, nonmyeloablative preparative regimens to achieve engraftment and allow graft-versus-malignancy effects to develop. This strategy reduces the risk of treatment-related mortality and allows transplantation for elderly or medically infirm patients not eligible for myeloablative therapy. Nonmyeloablative preparative regimens appear promising in diagnoses sensitive to graft-versus-malignancy effects and provide a platform for further development of cellular immunotherapy. Controlled clinical trials are warranted to define the role of nonmyeloablative allogeneic transplants in a range of hematologic malignancies and selected solid tumors.

Melphalan and purine analog-containing preparative regimens: reduced-intensity conditioning for patients with hematologic malignancies undergoing allogeneic progenitor cell transplantation

A reduced-intensity preparative regimen consisting of melphalan and a purine analog was evaluated for allogeneic transplantation in 86 patients who had a variety of hematologic malignancies and were considered poor candidates for conventional myeloablative therapies because of age or comorbidity. Seventy-eight patients received fludarabine 25 mg/m(2) daily for 5 days in combination with melphalan 180 mg/m(2) (n = 66) or 140 mg/m(2) (n = 12). Eight patients received cladribine 12 mg/m(2) continuous infusion for 5 days with melphalan 180 mg/m(2). The median age was 52 years (range, 22-70 years). Disease status at transplantation was either first remission or first chronic phase in 7 patients, untreated first relapse or subsequent remission in 16 patients, and refractory leukemia or transformed chronic myelogenous leukemia in 63 patients. Nonrelapse mortality rates on day 100 were 37.4% for the fludarabine/melphalan combination and 87.5% for the cladribine/melphalan combination. The median percentage of donor cells at 1 month in 75 patients was 100% (range, 0%-100%). The probability of grade 2-4 and 3-4 acute graft-versus-host disease was 0.49 (95% CI, 0.38-0.60) and 0.29 (95% CI, 0.18-0.41), respectively. Disease-free survival at 1 year was 57% for patients in first remission or chronic phase and 49% for patients with untreated first relapse or in a second or later remission. On multivariate analysis the strongest predictor for disease-free survival was a good or intermediate risk category. In summary, fludarabine/melphalan combinations are feasible in older patients with associated comorbidities, and long-term disease control can be achieved with reduced-intensity conditioning in this population.

Cryofibrinogenemia and skin necrosis in a patient with diffuse large cell lymphoma after high-dose chemotherapy and autologous stem cell transplantation

A 34-year-old woman with diffuse mediastinal B cell large cell lymphoma presented 60 days after high-dose chemotherapy and autologous stem cell transplantation, and post-transplant immunotherapy with interleukin-2, with skin necrosis in the ears and extremities. Extensive work-up revealed the presence of cryofibrinogenemia and associated thrombotic vasculopathy. The patient was successfully treated with corticosteroids and therapeutic plasma exchange. However, she had recurrence of large cell lymphoma a few weeks later and died of progressive disease. Cryfibrinogenemia and skin necrosis may have occurred secondary to the imminent relapse, or as a rare complication of high-dose chemotherapy or treatment with interleukin-2.

High-dose ifosfamide and etoposide with filgrastim for stem cell mobilization in patients with advanced ovarian cancer

High-dose chemotherapy combined with autologous peripheral blood stem cell transplantation has shown promise as treatment for recurrent or persistent epithelial ovarian cancer. We evaluated the stem cell mobilization regimen of high-dose ifosfamide plus etoposide in 32 patients with epithelial ovarian cancer, who had a positive second-look laparatomy or recurrent disease. Ifosfamide was given at 10 g/m2 by continuous i.v. from days 1 to 3. Etoposide was given at 150 mg/m2 every 12 h for six doses on days 1-3. Filgrastim was given at 10 microg/kg/d s.c. from day 5 until the completion of peripheral blood stem cell harvest. Fourteen of 32 patients had measurable or evaluable disease before mobilization therapy and were assessed for response. In nine (64%) of the 14 patients, treatment response was demonstrated, and these patients received a second cycle of mobilization therapy. The target CD34+ cell dose (>8 x 106 cells/kg) was achieved with a median of one apheresis (range 1-5). A median of 25.1 (range 8.0-122.5) x 106 CD34+ cells/kg body weight was collected. Non-hematologic toxicity was limited to grade 2 renal dysfunction in one patient and grade 2 hepatic dysfunction in three patients. In this patient group, high-dose ifosfamide plus etoposide with filgrastim support was well tolerated, lead to successful stem cell harvest and had antitumor activity.

Myelodysplastic syndrome and aplastic anemia: distinct entities or diseases linked by a common pathophysiology?

It is often difficult to distinguish myelodysplastic syndrome (MDS) from severe aplastic anemia (SAA) because both can present with profoundly hypocellular bone marrows. The distinction matters because although both conditions are complicated by pancytopenia, the risk of progression to acute leukemia is much greater in MDS. This chapter reexamines the relationship between SAA and MDS. The clinical and morphological features and pathophysiology of AA (including moderate and severe forms of acquired AA) are compared with MDS and hypoplastic MDS, with particular reference to new observations implicating autoimmune processes in both conditions. SAA and hypoplastic MDS (HMDS) are discussed in the light of these findings and attempts to separate nonevolving bone marrow failure syndromes from marrow failure progressing to acute leukemia are reviewed. The weight of evidence supports a common pathophysiology and, more speculatively, a common etiology for at least some forms of AA and MDS.

High-dose corticosteroid therapy for diffuse alveolar hemorrhage in allogeneic bone marrow stem cell transplant recipients

In a series of 74 patients with hematological malignancies undergoing allogeneic bone marrow or peri- pheral blood stem cell transplants from an HLA-identical sibling donor, four developed diffuse alveolar hemorrhage (DAH) between days 0 and 23 post transplant. Diagnosis was made by the radiographic finding of diffuse bilateral lung opacities, and bloody lavage fluid on bronchoscopy. Two patients required mechanical ventilatory support. They were treated with methylprednisolone 0.25-1.5 g/day for at least 4 days with slow tapering thereafter. All patients showed an immediate response and two became long-term survivors with normal respiratory function. Two had a relapse of DAH, developed acute respiratory distress syndrome (ARDS) and died with multi-organ failure. Risk factors for DAH were one or more courses of intensive chemotherapy pretransplant vs no treatment or low-dose chemotherapy (4/4 DAH vs 23/70 no DAH; P = 0.015), and second transplants (2/2 DAH vs 1/70 with no DAH; P = 0.006). These results indicate that DAH is life-threatening but is potentially reversible by prompt treatment with high doses of steroids.

Allogeneic hematopoietic transplantation as adoptive immunotherapy. Induction of graft-versus-malignancy as primary therapy

An immune-mediated graft-versus-malignancy effect is important to prevent relapse after allogeneic bone marrow transplant for a range of hematologic malignancies and potentially some solid tumors. Graft-versus-leukemia (GVL) effects as seen in response to donor lymphocyte infusions have been most prominent against indolent malignancies including chronic myelogenous leukemia, chronic lymphocytic leukemia, and low-grade lymphoma. Acute myelogenous leukemia and multiple myeloma may also respond. An alternative strategy for allogeneic transplantation is to avoid the toxicity of high-dose chemoradiotherapy and use a relatively nontoxic, nonablative preparative regimen to achieve engraftment, allowing subsequent infusion of additional donor lymphocytes to mediate GVL. Fludarabine-based nonablative chemotherapy agents, using standard dose combinations, produce moderate myelosuppression but are sufficiently immunosuppressive to allow engraftment of an allogeneic hematopoietic transplant and generation of graft-versus-malignancy effects.

Carmustine, etoposide, cytarabine and melphalan as a preparative regimen for allogeneic transplantation for high-risk malignant lymphoma

BACKGROUND

The combination of carmustine, etoposide, cytarabine and melphalan (BEAM) is an effective autologous transplantation preparative regimen for lymphoma and has little toxicity, but the feasibility and tolerance of BEAM as a preparative regimen for allogeneic transplantation has not been established.

PATIENTS AND METHODS

Thirty adults with primary refractory or recurrent intermediate- or low-grade lymphoma were treated on a prospective phase II study with carmustine 300 mg/m2 i.v. day -6, etoposide 200 mg/m2 i.v. followed by cytarabine 200 mg/m2 i.v. twice daily days -5 to -2, melphalan 140 mg/m2 i.v. day -1, and marrow or blood stem cells from an HLA-identical donor on day 0. Tacrolimus and methotrexate were used to prevent graft-vs.-host disease (GVHD).

RESULTS

Median time from transplantation was 20 mos (range 6-32 months). Median maximal regimen-related toxicity grade was 2, and four patients (13%) had a grade 3-4 regimen-related toxicity. Two patients had idiopathic interstitial pneumonitis. One patient had primary graft failure, and a second had autologous reconstitution documented at three months posttransplant. Grades 2-4 acute GVHD occurred in 31%, grades 3-4 in 16%, and chronic GVHD in 54%. Day-100 survival was 70%. Twenty-three patients achieved a complete response. The two-year relapse rate was 23%, survival was 48%, and disease-free survival (DFS) was 42%.

CONCLUSIONS

BEAM supports engraftment of allogeneic transplants and is a tolerable preparative regimen for allogeneic transplantation for lymphoma.

Reinventing bone marrow transplantation: reducing toxicity using nonmyeloablative, preparative regimens and induction of graft-versus-malignancy

Bone marrow transplantation was initially developed as a means to deliver supralethal doses of chemotherapy and radiation for treatment of malignancies. Myelosuppression is the dose-limiting toxicity for many chemotherapy drugs and whole-body radiation. Many malignancies exhibit a steep dose-response relationship to chemotherapy or radiotherapy. Bone marrow transplantation allows escalation of doses beyond those levels which produce severe bone marrow toxicity. Doses of many agents, particularly alkylating agents and whole body radiation, can be increased three- to fivefold above their conventional maximally tolerated dose. Marrow transplantation was considered a supportive care modality to restore hematopoiesis. It has become clear, however, that the high dose therapy does not eradicate the malignancy in many patients, and that the therapeutic benefit of allogeneic marrow transplantation is largely related to an associated immune-mediated graft-versus-malignancy effect.

Donor-recipient polymorphism of the proteinase 3 gene: a potential target for T-cell alloresponses to myeloid leukemia

The curative effect of allogeneic bone marrow transplantation (BMT) is in part due to an alloresponse of donor lymphocytes against recipient leukemia termed the graft versus leukemia (GvL) effect. To identify target antigens for the GvL response on leukemia cells, we looked for polymorphism of proteinase 3, a primary granule protein overexpressed in myeloid leukemias. The study was carried out in 10 patients with hematologic diseases and their HLA-identical marrow donors. By polymerase chain reaction (PCR)-single strand conformation polymorphism assay, followed by direct sequencing of the PCR products, we found seven DNA polymorphisms. One of them encodes for either an isoleucine or a valine at position 119 of the amino acid sequence. Peptides that span the polymorphic site, at amino acids 115-124, were shown to bind in vitro to the HLA-A2 molecule. We screened 23 HLA-A2 patients with myeloid leukemia and their HLA-identical donors for this polymorphism. No relapse was found in the group of 4 evaluable patients who possessed at least one allele absent in their donor, whereas 7 of the 15 remaining evaluable patients relapsed. These data support the possibility that T-cell responses to allelic differences of proteinase 3 could be used as a basis for designing leukemia-specific adoptive T-cell therapy in acute and chronic myeloid leukemias.

A technique for dual determination of cytotoxic and helper lymphocyte precursor frequency by a miniaturized dye release method

Helper (HTLPf) and cytotoxic (CTLPf) lymphocyte precursor frequency assays are increasingly used in bone marrow stem cell and organ transplant compatibility testing. Current techniques require large cell numbers and radioisotopes. To improve the technique, we developed a miniaturized fluorescent read-out combined HTLPf/CTLPf limiting dilution assay. The assay requires only 5 x 10(6) stimulators, 2 x 10(6) responders and 0.24 x 10(6) target cells in Terasaki plates (40 microl/well). For the HTLPf, culture supernatants from each well were assayed for IL-2 production. The IL-2-dependent proliferation of the mouse 9.12 cell line was detected by a semi-automated fluorescent dye technique. After addition of rhIL-2 (recombinant human IL-2) on days 3 and 7, CTLPs were detected on day 10 by measuring the lysis of dye-labeled targets. Results were comparable to standard radioisotope-based techniques. The assay had a coefficient of variation of approximately 30%. The assay detected helper CD4 cells, pure cytotoxic CD8, helper CD8 cells and helper/cytotoxic CD8 cells. Discrimination was demonstrated between HLA-matched related and non-related pairs. The ease of testing and small cell numbers required should facilitate further evaluation of HTLPf and CTLPf for compatibility testing in unrelated donor transplantation and monitoring immune responses following adoptive transfer of lymphocytes.

Polymorphism in CD33 and CD34 genes: a source of minor histocompatibility antigens on haemopoietic progenitor cells?

Following bone marrow stem cell transplantation allo-responses against haemopoietic progenitor cells (HPC), causing graft rejection and graft-versus-leukaemia effects, can be induced by donor T cells recognizing peptides derived from polymorphic endogenous proteins present in HPC. Since CD33 and CD34 are both expressed on HPC, we looked for genetic polymorphisms that might be the source of minor histocompatibility antigens (mHA) on such cells. Bone marrow from 14 donors and their HLA-identical recipients undergoing BMT for haematological malignancies were studied. Using non-radioactive single-strand conformation polymorphism analysis (cold SSCP) of complementary DNA encoding CD33 and CD34, three DNA polymorphisms, two in CD33 and one in CD34 were found and sequenced. Two were in non-coding regions, but in CD33, ATA or ATG at codon 183 resulted in an Ile or Met in the protein sequence. Nonapeptides derived from both alleles were predicted to bind to HLA A68.1. Thus two alleles of CD33 protein exist that could be mHA. With an alternate allele frequency of < 10%, allo-responses against CD33 would be uncommon after marrow transplantation. However, donors homozygous for this allele could be used to generate cytotoxic T cells against the frequent CD33 allele, for adoptive therapy of leukaemia.

Specific depletion of alloreactive T cells in HLA-identical siblings: a method for separating graft-versus-host and graft-versus-leukaemia reactions

Accumulating evidence indicates that alloreactive donor T cells confer both graft-versus-host (GVH) and graft-versus-leukaemia (GVL) reactivity following allogeneic bone marrow transplantation. We have developed a method to deplete alloreactive donor T cells with an immunotoxin targeting the alpha chain of the IL-2 receptor. In patients with chronic myeloid leukaemia and their HLA-identical sibling donors, we measured donor helper T-lymphocyte precursor frequencies (HTLPf) against recipient peripheral blood mononuclear cells (PBMNC; donor versus host), recipient leukaemia cells (donor versus leukaemia) and third-party PBMNC, before and after the depletion. In seven pairs there was a 4.3-fold reduction of donor-versus-host HTLPf (P=0.017), without a significant change in the donor frequencies against third party (P=0.96). In eight further donor-recipient pairs, immunotoxin-depleted donor versus patient PBMNC HTLPf 4.5-fold (mean 1/155,000 before and 1/839,000 after depletion, P=0.007). There was a smaller non-significant 1.8-fold reduction in donor-versus-leukaemia HTLPf from 1/192,000 to 1/334,000 (P=0.19). These results suggest that selective T-cell depletion can significantly deplete donor anti-host reactivity while conserving anti-leukaemia reactivity in HLA-matched donor-recipient pairs.

T cell-depleted bone marrow transplantation and delayed T cell add-back to control acute GVHD and conserve a graft-versus-leukemia effect

Thirty-eight patients with hematological malignancies, received T cell-depleted marrow transplants (BMT) and cyclosporine to prevent acute graft-versus-host disease (aGVHD), followed by delayed add-back of donor lymphocytes to prevent leukemia relapse. In 26 patients scheduled for donor T cell add-back of 2 x 10(6) cells/kg on day 30 and 5 x 10(7) cells/kg on day 45 (schedule 1), the overall probability of grade > or = II aGVHD developing was 31.5%, with a 15.5% probability of aGVHD occurring after T cell add-back. In 12 patients receiving 10(7) donor T cells/kg on day 30 (schedule 2), the probability of grade > or = II aGVHD was 100%. The incidence of grade III-IV aGVHD was higher in schedule 2 than in schedule 1 (P=0.02). Of 24 evaluable patients, 10 (46%) developed chronic GVHD which was limited in eight and extensive in two. Current disease-free survival for 18 patients at standard risk for relapse (chronic myeloid leukemia (CML) in chronic or accelerated phase, acute myeloid leukemia in remission) vs 20 patients with more advanced leukemia or multiple myeloma were respectively 72% vs 12% (P < 0.01) with a 29% vs 69% probability of relapse (P=0.08). In 12 CML patients surviving more than 3 months, PCR analysis of the BCR/ABL transcript showed that minimal residual disease after T cell add-back was transient except in two patients who developed hematological relapse. Results indicate that the risk of acute GVHD is low following substantial T cell doses, transfused 45 days after transplant, using cyclosporine prophylaxis. Furthermore a graft-versus-leukemia effect was conserved.