Early viral reactivation despite excellent immune reconstitution following haploidentical Bone marrow transplant with post-transplant cytoxan for sickle cell disease.

BACKGROUND: Haploidentical bone marrow transplant (haplo-BMT) offers near universal donor availability as a curative modality for individuals with severe sickle cell disease (SCD). However, the required intense immunodepletion is associated with increased infectious complications. A paucity of data exists on immune reconstitution following haplo-BMT for SCD. METHODS: A multi-institution learning collaborative was developed in the context of a phase II clinical trial of a non-myeloablative, related haplo-BMT with post-transplant cyclophosphamide for SCD. We report results from a cohort of 23 patients for whom immune reconstitution data up to one year were available. RESULTS: Median age was 14.8 years. Out of 23, 18 participants received pre-conditioning with azathioprine, hydroxyurea, and hypertransfusions. 70% (16/23) of participants had multiple indications for haplo-BMT. We observed excellent immune reconstitution of CD4, CD8, CD19, and CD56 cellular subsets by 6 months post transplant. Engraftment rate and event-free survival in this cohort were 100% and 96%, respectively. 70% (16/23) of patients had at least one viral reactivation or infection, including CMV 35% (8/23), HHV-6 22% (5/23), and polyoma virus 17% (4/23), with no cases of post-transplant lymphoproliferative disease. CONCLUSION: Further prospective studies are needed to better characterize immune reconstitution and the immunologic basis for increased viral reactivation following haplo-BMT with post-transplant cyclophosphamide for SCD.

Haploidentical Bone Marrow Transplantation with Post-Transplantation Cyclophosphamide Plus Thiotepa Improves Donor Engraftment in Patients with Sickle Cell Anemia: Results of an International Learning Collaborative.

Curative therapy for individuals with severe sickle cell disease (SCD) who lack an HLA-identical sibling donor has been frustratingly elusive. In with the goal of improving engraftment while minimizing transplantation-related morbidity, a multi-institutional learning collaborative was developed in the context of a Phase II clinical trial of nonmyeloablative, related HLA-haploidentical (haplo) bone marrow transplantation (BMT) with post-transplantation cyclophosphamide. All eligible participants had hemoglobin SS, and 89% (16 of 18) had an identifiable donor. The median patient age was 20.9 years (IQR, 12.1 to 26.0 years), and the most common indication for transplantation was overt stroke (in 69%; 11 of 16). In the first 3 patients, the conditioning regimen consisted of antithymocyte globulin, fludarabine, cyclophosphamide, and low-dose total body irradiation. Graft-versus-host disease (GVHD) prophylaxis included post-transplantation cyclophosphamide, mycophenolate mofetil, and sirolimus. Primary graft rejection occurred in 2 of the 3 patients (67%), which triggered the study-stopping rule. To reduce graft rejection risk, thiotepa was added to the conditioning regimen, and then 15 patients (including 2 with previous graft rejection) underwent haplo-BMT with this thiotepa-augmented conditioning regimen. At a median follow-up of 13.3 months (interquartile range [IQR], 3.8 to 23.1 months), 93% (14 of 15) had >95% stable donor engraftment at 6 months, with 100% overall survival. The median time to neutrophil engraftment (>500) was 22 days (IQR, 19 to 27 days), and that for platelet engraftment (>50 x 109/L) was 28 days (IQR, 27 days to not reached). Two patients had grade III-IV acute GVHD, 1 patient had mild chronic GVHD, and 86% of patients (6 of 7) were off immunosuppression therapy by 1-year post-transplantation. Our data suggest that haplo-BMT with post-transplantation cyclophosphamide and thiotepa improves donor engraftment without significantly increasing morbidity or mortality and could dramatically expand curative options for individuals with SCD.

Elucidation of the EP defect in Diamond-Blackfan anemia by characterization and prospective isolation of human EPs.

Diamond-Blackfan anemia (DBA) is a disorder characterized by a selective defect in erythropoiesis. Delineation of the precise defect is hampered by a lack of markers that define cells giving rise to erythroid burst- and erythroid colony-forming unit (BFU-E and CFU-E) colonies, the clonogenic assays that quantify early and late erythroid progenitor (EEP and LEP) potential, respectively. By combining flow cytometry, cell-sorting, and single-cell clonogenic assays, we identified Lin(-)CD34(+)CD38(+)CD45RA(-)CD123(-)CD71(+)CD41a(-)CD105(-)CD36(-) bone marrow cells as EEP giving rise to BFU-E, and Lin(-)CD34(+/-)CD38(+)CD45RA(-)CD123(-)CD71(+)CD41a(-)CD105(+)CD36(+) cells as LEP giving rise to CFU-E, in a hierarchical fashion. We then applied these definitions to DBA and identified that, compared with controls, frequency, and clonogenicity of DBA, EEP and LEP are significantly decreased in transfusion-dependent but restored in corticosteroid-responsive patients. Thus, both quantitative and qualitative defects in erythroid progenitor (EP) contribute to defective erythropoiesis in DBA. Prospective isolation of defined EPs will facilitate more incisive study of normal and aberrant erythropoiesis.

Single-cell profiling of human bone marrow progenitors reveals mechanisms of failing erythropoiesis in Diamond-Blackfan anemia.

Ribosome dysfunction underlies the pathogenesis of many cancers and heritable ribosomopathies. Here, we investigate how mutations in either ribosomal protein large (RPL) or ribosomal protein small (RPS) subunit genes selectively affect erythroid progenitor development and clinical phenotypes in Diamond-Blackfan anemia (DBA), a rare ribosomopathy with limited therapeutic options. Using single-cell assays of patient-derived bone marrow, we delineated two distinct cellular trajectories segregating with ribosomal protein genotypes. Almost complete loss of erythroid specification was observed in RPS-DBA. In contrast, we observed relative preservation of qualitatively abnormal erythroid progenitors and precursors in RPL-DBA. Although both DBA genotypes exhibited a proinflammatory bone marrow milieu, RPS-DBA was characterized by erythroid differentiation arrest, whereas RPL-DBA was characterized by preserved GATA1 expression and activity. Compensatory stress erythropoiesis in RPL-DBA exhibited disordered differentiation underpinned by an altered glucocorticoid molecular signature, including reduced ZFP36L2 expression, leading to milder anemia and improved corticosteroid response. This integrative analysis approach identified distinct pathways of erythroid failure and defined genotype-phenotype correlations in DBA. These findings may help facilitate therapeutic target discovery.

Hemophagocytic lymphohistiocytosis responding to withdrawal of gluten: a case report.

BACKGROUND: This is the first documented case of a patient with hemophagocytic lymphohistiocytosis in association with coeliac disease. There was complete clinical and biochemical remission of hemophagocytic lymphohistiocytosis following the introduction of a gluten-free diet. CASE PRESENTATION: A 7-year-old white girl presented with fevers and maculopapular rash with a recent history of tonsillitis. Blood tests revealed thrombocytopenia (64×109/L), anemia (80 g/L), hypofibrinogenemia (1 g/L), and hyperferritinemia (71,378 µg/L). A bone marrow revealed evidence of hemophagocytosis, but the results of tests for the genetic or familial-associated hemophagocytic lymphohistiocytosis syndromes were negative. The results of screening tests for known secondary causes were negative. She was diagnosed as having hemophagocytic lymphohistiocytosis and following treatment with the hemophagocytic lymphohistiocytosis-2004 protocol these symptoms, in addition to the biochemical and hematological markers, completely resolved. She presented again 10 months later with fever, rash, and biochemical abnormalities suggestive of hemophagocytic lymphohistiocytosis. Her tissue transglutaminase was markedly raised and the results of blood tests revealed a genetic susceptibly to coeliac disease in the form of HLA-DQ2 positivity. She commenced a gluten-free diet and there was complete symptomatic and biochemical response without any further chemotherapy. She had further episodic rashes, each associated with the accidental intake of gluten. CONCLUSIONS: This is to the best of our knowledge the first documented case of hemophagocytic lymphohistiocytosis in association with coeliac disease. No other secondary cause found; she initially responded to chemoimmunotherapy specific for hemophagocytic lymphohistiocytosis but relapsed within a few months of cessation of treatment and then achieved complete remission on gluten withdrawal alone.