Transplantation for bone marrow failure: current issues.

The preferred treatment of idiopathic aplastic anemia (AA) is allogeneic hematopoietic stem cell transplantation (HSCT) from a human leukocyte antigen (HLA)-identical sibling donor. Transplantation from a well-matched unrelated donor (MUD) may be considered for patients without a sibling donor after failure of immunosuppressive therapy, as may alternative transplantation (mismatched, cord blood or haplo-identical HSCT) for patients without a MUD. HSCT may also be contemplated for congenital disorders in cases of pancytopenia or severe isolated cytopenia. Currently, HSCT aims are not only to cure patients but also to avoid long-term complications, notably chronic graft-versus-host disease (GVHD), essential for a good quality of life long term. This paper summarizes recent advances in HSCT for idiopathic and inherited AA disorders. The effect of age on current transplantation outcomes, the role of transplantation in paroxysmal nocturnal hemoglobinuria, and the prevention of GVHD are also discussed. Emerging strategies regarding the role of up-front unrelated donor and alternative donor HSCT in idiopathic AA, along with advances in the treatment of clonal evolution in Fanconi anemia, are also examined.

Consenso español para el diagnóstico y tratamiento de la hemoglobinuria paroxística nocturna / Spanish consensus statement for diagnosis and treatment of paroxysmal nocturnal haemoglobinuria

La hemoglobinuria paroxística nocturna (HPN) es una enfermedad clonal de las células progenitoras hematopoyéticas originada por la mutación adquirida del gen fosfatidil-inositol-glicano del grupo A, situado en el brazo corto del cromosoma X. Se caracteriza por anemia hemolítica intravascular, tendencia a la trombosis y un componente variable de insuficiencia medular. Otras complicaciones derivadas de la hemólisis son disfagia, disfunción eréctil, dolores abdominales, astenia e insuficiencia renal crónica (un 65% de los pacientes). La enfermedad afecta por igual a ambos sexos y puede aparecer a cualquier edad, con una mayor incidencia en la tercera década de la vida. Actualmente, el diagnóstico se basa en la detección de poblaciones celulares con marcadores asociados al déficit de glucosil-fosfatidil-inositol mediante citometría de flujo. Durante años, el pilar terapéutico de la HPN hemolítica era el soporte transfusional. Un gran avance en el tratamiento ha sido la aprobación del anticuerpo monoclonal humanizado eculizumab, que bloquea la proteína C5 del complemento impidiendo su activación, y por tanto, la hemólisis. Diversos estudios han confirmado que el tratamiento con eculizumab evita o disminuye el requerimiento transfusional, reduce la probabilidad de trombosis, mejora la sintomatología asociada y la calidad de vida de los pacientes con HPN, mostrando un aumento de la supervivencia. Este rápido avance en el conocimiento de la enfermedad y su tratamiento hace necesario adaptar y homogeneizar las directrices de actuación clínica en el manejo de pacientes con HPN (AU)

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired clonal disorder of the haematopoietic progenitor cells due to a somatic mutation in theX-linked phosphatidylinositol glycan class A gene. The disease is characterized by intravascular haemolytic anaemia, propensity to thromboembolic events and bone marrow failure. Other direct complications of haemolysis include dysphagia, erectile dysfunction, abdominal pain, asthenia and chronic renal failure (65% of patients). The disease appears more often in the third decade of life and there is no sex or age preference. Detection of markers associated with glucosyl phosphatidyl inositol deficit by flow cytometry is currently used in the diagnosis of PNH. For years, transfusions have been the mainstay of therapy for PNH. A breakthrough in treatment has been the approval of the humanized monoclonal antibody eculizumab, which works by blocking the C5 complement protein, preventing its activation and therefore haemolysis. Several studies have confirmed that treatment with eculizumab avoids or decreases the need for transfusions, decreases the probability of thrombosis, improves the associated symptomatology and the quality of life in patients with PNH, showing an increase in survival. Because of rapid advances in the knowledge of the disease and its treatment, it may become necessary to adapt and standardize clinical guidelines for the management of patients with PNH (AU)

Paroxysmal nocturnal hemoglobinuria: a complement-mediated hemolytic anemia.

Paroxysmal nocturnal hemoglobinuria is manifests with a chronic hemolytic anemia from uncontrolled complement activation, a propensity for thrombosis and marrow failure. The hemolysis is largely mediated by the alternative pathway of complement. Clinical manifestations result from the lack of specific cell surface proteins, CD55 and CD59, on PNH cells. Complement inhibition by eculizumab leads to dramatic clinical improvement. While this therapeutic approach is effective, there is residual complement activity resulting from specific clinical scenarios as well as from upstream complement components that can account for suboptimal responses in some patients. Complement inhibition strategies are an area of active research.

OCH ameliorates bone marrow failure in mice via downregulation of T-bet expression.

The aim of this study is to evaluate the immune mechanism of OCH in the treatment of AA (also named bone marrow failure, BMF) induced in mice. OCH at a dose of 400 µg/kg was injected intraperitoneally (I.P.) prior to the induction of BMF. Our study showed that the incidence of BMF was 100% in BMF group and 13% in OCH treatment group. Significant higher level of IL-4 and lower level of IFN-γ were observed in OCH group than that in BMF group (P < 0.05) as well as untreated group over BMF (P < 0.05). However, there was no significant difference between OCH and untreated group. Compared with untreated, the expression level of T-bet in OCH and BMF was all significantly higher. However, T-bet expression level was lower in OCH than in BMF. In addition, OCH treatment increased NKT cell fractions of bone marrow and the colonies of CFU-GM. In conclusion, treatment of OCH prior to the induction of BMF could prevent the incidence of BMF possibly through downregulating T-bet expression leading to the transition of immune response from Th1 to Th2, suggesting OCH might be a new therapeutic approach in the treatment of BMF or AA.

Gene therapy cures the anemia and lethal bone marrow failure in a mouse model of RPS19-deficient Diamond-Blackfan anemia.

Diamond-Blackfan anemia is a congenital erythroid hypoplasia caused by functional haploinsufficiency of genes encoding ribosomal proteins. Mutations involving the ribosomal protein S19 gene are detected in 25% of patients. Enforced expression of ribosomal protein S19 improves the overall proliferative capacity, erythroid colony-forming potential and erythroid differentiation of hematopoietic progenitors from ribosomal protein S19-deficient patients in vitro and in vivo following xenotransplantation. However, studies using animal models are needed to assess the therapeutic efficacy and safety of the viral vectors. In the present study we have validated the therapeutic potential of gene therapy using mouse models of ribosomal protein S19-deficient Diamond-Blackfan anemia. Using lentiviral gene transfer we demonstrated that enforced expression of ribosomal protein S19 cures the anemia and lethal bone marrow failure in recipients transplanted with ribosomal protein S19-deficient cells. Furthermore, gene-corrected ribosomal protein S19-deficient cells showed an increased pan-hematopoietic contribution over time compared to untransduced cells without signs of vector-mediated toxicity. Our study provides a proof of principle for the development of clinical gene therapy to cure ribosomal protein 19-deficient Diamond-Blackfan anemia.

Type 1 interferons suppress accelerated osteoclastogenesis and prevent loss of bone mass during systemic inflammatory responses to Pneumocystis lung infection.

HIV infection causes loss of CD4(+) T cells and type 1 interferon (IFN)-producing and IFN-responsive dendritic cells, resulting in immunodeficiencies and susceptibility to opportunistic infections, such as Pneumocystis. Osteoporosis and bone marrow failure are additional unexplained complications in HIV-positive patients and patients with AIDS, respectively. We recently demonstrated that mice that lack lymphocytes and IFN a/b receptor (IFrag(-/-)) develop bone marrow failure after Pneumocystis lung infection, whereas lymphocyte-deficient, IFN α/ß receptor-competent mice (RAG(-/-)) had normal hematopoiesis. Interestingly, infected IFrag(-/-) mice also exhibited bone fragility, suggesting loss of bone mass. We quantified bone changes and evaluated the potential connection between progressing bone fragility and bone marrow failure after Pneumocystis lung infection in IFrag(-/-) mice. We found that Pneumocystis infection accelerated osteoclastogenesis as bone marrow failure progressed. This finding was consistent with induction of osteoclastogenic factors, including receptor-activated nuclear factor-κB ligand and the proapoptotic factor tumor necrosis factor-related apoptosis-inducing ligand, in conjunction with their shared decoy receptor osteoprotegerin, in the bone marrow of infected IFrag(-/-) mice. Deregulation of this axis has also been observed in HIV-positive individuals. Biphosphonate treatment of IFrag(-/-) mice prevented bone loss and protected loss of hematopoietic precursor cells that maintained activity in vitro but did not prevent loss of mature neutrophils. Together, these data show that bone loss and bone marrow failure are partially linked, which suggests that the deregulation of the receptor-activated nuclear factor-κB ligand/osteoprotegerin/tumor necrosis factor-related apoptosis-inducing ligand axis may connect the two phenotypes in our model.

Recurrence of paroxysmal cold hemoglobinuria in a boy after physical cooling for fever.

Hemolysis and hemoglobinuria after direct exposure to cold has rarely been reported in paroxysmal cold hemoglobinuria (PCH). The authors describe a 2.5-year-old boy with PCH (Donath-Landsteiner autoimmune hemolytic anemia), in whom 16 days after presentation, the hemoglobinuria and hemolysis recurred, when he was subjected to physical cooling, as a means to control fever associated with hospital-acquired croup. The hemolysis resolved with warmth, and administration of dexamethasone. PCH should be suspected in children with hemolytic anemia and positive direct antiglobulin test for complement. Avoidance of cold in the recovery period is imperative to prevent recurrences, whereas a short course of corticosteroids may be of benefit in suppressing the antibody production.

Aortic valve bypass for aortic stenosis in a patient with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired bone marrow disorder characterized by hemolytic anemia, neutropenia, thrombocytopenia, hemoglobinuria, and venous thrombosis. Cardiopulmonary bypass-induced complement activation may be associated with exacerbation of hemolysis in patients with PNH undergoing cardiac operations. We describe a 77-year-old man with PNH and critical symptomatic aortic stenosis who underwent successful aortic valve bypass operation without cardiopulmonary bypass as an alternative to conventional aortic valve replacement.

Eculizumab prevents intravascular hemolysis in patients with paroxysmal nocturnal hemoglobinuria and unmasks low-level extravascular hemolysis occurring through C3 opsonization.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria is an acquired hemolytic anemia characterized by intravascular hemolysis which has been demonstrated to be effectively controlled with eculizumab. However, lactate dehydrogenase levels remain slightly elevated and haptoglobin levels remain low in some patients suggesting residual low-level hemolysis. This may be due to C3-mediated clearance of paroxysmal nocturnal hemoglobinuria red blood cells through the reticuloendothelial system. DESIGN AND METHODS: Thirty-nine samples from patients not treated with eculizumab and 31 samples from patients treated with eculizumab were obtained (for 17 of these 31 samples there were also samples taken prior to eculizumab treatment). Membrane bound complement was assessed by flow cytometry. Direct antiglobulin testing was carried out using two methods. Lactate dehydrogenase was assayed to assess the degree of hemolysis. RESULTS: Three of 39 patients (8%) with paroxysmal nocturnal hemoglobinuria not on eculizumab had a positive direct antiglobulin test, while the test was positive in 21 of 31 (68%) during eculizumab treatment. Of these 21 patients who had a positive direct antiglobulin test during eculizumab treatment, 17 had been tested prior to treatment; only one was positive. Flow cytometry using anti-C3 monoclonal antibodies was performed on the 21 direct antiglobulin test-positive, eculizumab-treated patients; the median proportion of C3-positive total red blood cells was 26%. Among the eculizumab-treated patients, 16 of the 21 (76.2%) with a positive direct antiglobulin test received at least one transfusion compared with one of ten (10.0%) of those with a negative test (P<0.01). Among the eculizumab-treated patients, the mean hemoglobin value for the 21 with a positive direct antiglobulin test was 9.6+/-0.3 g/dL, whereas that in the ten patients with a negative test was 11.0+/-0.4 g/dL (P=0.02). CONCLUSIONS: These data demonstrate a previously masked mechanism of red cell clearance in paroxysmal nocturnal hemoglobinuria and suggests that blockade of complement at C5 allows C3 fragment accumulation on some paroxysmal nocturnal hemoglobinuria red cells, explaining the residual low-level hemolysis occurring in some eculizumab-treated patients.

A novel approach to preventing the hemolysis of paroxysmal nocturnal hemoglobinuria: both complement-mediated cytolysis and C3 deposition are blocked by a monoclonal antibody specific for the alternative pathway of complement.

The clinical hallmark of paroxysmal nocturnal hemoglobinuria (PNH) is chronic intravascular hemolysis that is a consequence of unregulated activation of the alternative pathway of complement (APC). Intravascular hemolysis can be inhibited in patients by treatment with eculizumab, a monoclonal antibody that binds complement C5 thereby preventing formation of the cytolytic membrane attack complex of complement. However, in essentially all patients treated with eculizumab, persistent anemia, reticulocytosis, and biochemical evidence of hemolysis are observed; and in a significant proportion, their PNH erythrocytes become opsonized with complement C3. These observations suggest that PNH patients treated with eculizumab are left with clinically significant immune-mediated hemolytic anemia because the antibody does not block APC activation. With a goal of improving PNH therapy, we characterized the activity of anti-C3b/iC3b monoclonal antibody 3E7 in an in vitro model of APC-mediated hemolysis. We show that 3E7 and its chimeric-deimmunized derivative H17 block both hemolysis and C3 deposition on PNH erythrocytes. The antibody is specific for the APC C3/C5 convertase because classical pathway-mediated hemolysis is unaffected by 3E7/H17. These findings suggest an approach to PNH treatment in which both intravascular and extravascular hemolysis can be inhibited while preserving important immune functions of the classical pathway of complement.