Catalina Ramos

Differences in the Phenotype, Cytokine Gene Expression Profiles, and In Vivo Alloreactivity of T Cells Mobilized with Plerixafor Compared with G-CSF

Plerixafor (Mozobil) is a CXCR4 antagonist that rapidly mobilizes CD34+ cells into circulation. Recently, plerixafor has been used as a single agent to mobilize peripheral blood stem cells for allogeneic hematopoietic cell transplantation. Although G-CSF mobilization is known to alter the phenotype and cytokine polarization of transplanted T cells, the effects of plerixafor mobilization on T cells have not been well characterized. In this study, we show that alterations in the T cell phenotype and cytokine gene expression profiles characteristic of G-CSF mobilization do not occur after mobilization with plerixafor. Compared with nonmobilized T cells, plerixafor-mobilized T cells had similar phenotype, mixed lymphocyte reactivity, and Foxp3 gene expression levels in CD4+ T cells, and did not undergo a change in expression levels of 84 genes associated with Th1/Th2/Th3 pathways. In contrast with plerixafor, G-CSF mobilization decreased CD62L expression on both CD4 and CD8+ T cells and altered expression levels of 16 cytokine-associated genes in CD3+ T cells. To assess the clinical relevance of these findings, we explored a murine model of graft-versus-host disease in which transplant recipients received plerixafor or G-CSF mobilized allograft from MHC-matched, minor histocompatibility–mismatched donors; recipients of plerixafor mobilized peripheral blood stem cells had a significantly higher incidence of skin graft-versus-host disease compared with mice receiving G-CSF mobilized transplants (100 versus 50%, respectively, p = 0.02). These preclinical data show plerixafor, in contrast with G-CSF, does not alter the phenotype and cytokine polarization of T cells, which raises the possibility that T cell–mediated immune sequelae of allogeneic transplantation in humans may differ when donor allografts are mobilized with plerixafor compared with G-CSF.

Conditioning with rabbit versus horse ATG dramatically alters clinical outcomes in identical twins with severe aplastic anemia transplanted with the same allogeneic donor

Severe aplastic anemia (SAA) is a rare disorder leading to bone marrow failure, which if left untreated, is invariably fatal. Conventional therapies with immunosuppressive therapy or allogeneic hematopoietic stem cell transplantation (HSCT) are highly effective. HSCT can offer a greater outcome in younger patients who have an available HLA match-related donor. Recent studies showing the addition of antithymocyte globulin (ATG) to the conditioning regimen improves engraftment and reduces the risk of graft-versus-host disease (GVHD).There are currently two ATG preparations in the USA, equine (or horse) and rabbit ATG. These agents are pharmacologically distinct, having significant differences in their pharmacokinetics and in vivo immunosuppressive effects [N Engl J Med 365(5):430–438, 2011]. Here, we report a case of two monozygotic twins with constitutional SAA that evolved to myelodysplastic syndrome (MDS) who both underwent allogeneic peripheral blood stem cell transplantation (PBSC) from the same single HLA antigen mismatched sibling donor with the only difference in the transplant regimen being the type of ATG used in the preparative regimen; one twin received horse ATG and the other received rabbit ATG during conditioning. This report emphasizes that dramatic differences in donor T cell chimerism and clinical outcomes including GVHD can occur as a consequence of the type of ATG that is utilized in the transplant conditioning regimen. These differences highlight that these agents should not be considered interchangeable drugs when used in this setting.

Rapid donor T-cell engraftment increases the risk of chronic graft-versus-host disease following salvage allogeneic peripheral blood hematopoietic cell transplantation for bone marrow failure syndromes

The risk of graft‐rejection after allogeneic hematopoietic cell transplantation using conventional cyclophosphamide‐based conditioning is increased in patients with bone marrow failure syndromes (BMFS) who are heavily transfused and often HLA‐alloimmunized. Fifty‐six patients with BMFS underwent fludarabine‐based reduced‐intensity conditioning and allogeneic peripheral blood progenitor cell (PBPC) transplantation at a single institution. The conditioning regimen consisted of intravenous cyclophosphamide, fludarabine, and equine antithymocyte globulin. Graft‐versus‐host disease (GVHD) prophylaxis included cyclosporine A alone or in combination with either mycophenolate mofetil or methotrexate. To reduce the risk of graft‐rejection/failure, unmanipulated G‐CSF mobilized PBPCs obtained from an HLA‐identical or single HLA‐antigen mismatched relative were transplanted rather than donor bone marrow. Despite a high prevalence of pretransplant HLA‐alloimmunization (41%) and a heavy prior transfusion burden, graft‐failure did not occur with all patients having sustained donor lympho‐hematopoietic engraftment. The cumulative incidence of grade II–IV acute‐GVHD and chronic‐GVHD was 51.8% and 72%, respectively; with 87.1% surviving at a median follow‐up of 4.5 years. A multivariate analysis showed pretransplant alloimmunization and rapid donor T‐cell engraftment (≥95% donor by day 30) were both significantly (P < 0.05) associated with the development of chronic‐GVHD (adjusted HR 2.13 and 2.99, respectively). These data show fludarabine‐based PBPC transplantation overcomes the risk of graft‐failure in patients with BMFS, although rapid donor T‐cell engraftment associated with this approach appears to increase the risk of chronic‐GVHD. (Clinicaltrials.gov identifier: NCT00003838). Am. J. Hematol. 88:874–882, 2013.

Allogeneic transplantation using CD34+selected peripheral blood progenitor cells combined with non-mobilized donor T cells for refractory severe aplastic anaemia

Allogeneic haematopoietic stem cell transplantation is curative for severe aplastic anaemia (SAA) unresponsive to immunosuppressive therapy. To reduce chronic graft‐versus‐host disease (GVHD), which occurs more frequently after peripheral blood stem cell (PBSC) transplantation compared to bone‐marrow transplantation (BMT), and to prevent graft rejection, we developed a novel partial T‐cell depleted transplant that infuses high numbers of granulocyte colony‐stimulating factor‐mobilized CD34+ selected PBSCs combined with a BMT‐equivalent dose of non‐mobilized donor T‐cells. Fifteen patients with refractory SAA received cyclophosphamide, anti‐thymocyte globulin and fludarabine conditioning, and were transplanted with a median 8 × 106 CD34+ cells/kg and 2 × 107 non‐mobilized CD3+ T‐cells/kg from human leucocyte antigen‐matched sibling donors. All achieved sustained engraftment with only two developing acute and two developing chronic GVHD. With a 3·5‐year median follow‐up, 86% of patients survived and were transfusion‐independent. When compared to a retrospective cohort of 56 bone‐marrow failure patients that received the identical transplant preparative regimen and GVHD prophylaxis with the exception that the allograft contained unmanipulated PBSCs, partial T‐cell depleted transplant recipients had delayed donor T‐cell chimerism and relative reduction of 75% in the incidence of acute grade II‐IV GVHD (13% vs. 52%; P = 0·010) and of 82% in chronic GVHD (13% vs. 72%; P = 0·0004). In multivariate analysis, partial T‐cell depleted transplants remained significantly associated with a reduced risk of GVHD. In conclusion, for patients with refractory SAA, this novel transplant strategy achieves excellent engraftment and survival when compared to unmanipulated PBSC transplants and dramatically reduces the incidence of both acute and chronic GVHD.

Durable remission of mantle cell lymphoma relapsing a third time after allogeneic hematopoietic stem cell transplantation treated with rituximab, bortezomib, donor lymphocytes, and pegylated interferon.

Although there has been noteworthy progress in the treatment of mantle cell lymphoma (MCL) over the past decade,1 disease relapse after dose-intensive chemotherapy or autologous stem cell transplantation remains problematic.2-4 Allogeneic hematopoietic stem cell transplantation (allo-HCT) is capable of curing patients with relapsed MCL, including those with disease progression after autologous stem cell transplantation.3 Disease remission after allo-HCT is attributable to the cytoreductive effects of dose-intensive conditioning and to donor T-cellemediated graft-versus-tumor effects.3-8 Even when patients relapse after an allo-HCT, donor lymphocyte infusions (DLIs) leading to graft-versus-MCL effects can still induce long-term disease remission in a subset of patients. However, for patients relapsing after DLI, long-term disease control is rare because tumors frequently develop mechanisms to evade donor immunity. We report a patient with MCL with multiple relapses after reduced-intensity conditioning (RIC) allo-HCT and DLIs who achieved a fourth disease remission that is ongoing more than 3 years after the last relapse after treatment with a combination of rituximab/bortezomib, pegylated interferon (PEG-IFN), and a ninth DLI. This case suggests that graft-versus-tumor (GVT) effects can still be bolstered years after an allogeneic transplant, even in patients who have relapsed multiple times, by DLIs whose efficacy may be enhanced by combination with interferon (IFN)-based cytokine treatment.