Catherine S. Manno

Successful transduction of liver in hemophilia by AAV-Factor IX and limitations imposed by the host immune response

We have previously shown that a single portal vein infusion of a recombinant adeno-associated viral vector (rAAV) expressing canine Factor IX (F.IX) resulted in long-term expression of therapeutic levels of F.IX in dogs with severe hemophilia B. We carried out a phase 1/2 dose-escalation clinical study to extend this approach to humans with severe hemophilia B. rAAV-2 vector expressing human F.IX was infused through the hepatic artery into seven subjects. The data show that: (i) vector infusion at doses up to 2 × 1012 vg/kg was not associated with acute or long-lasting toxicity; (ii) therapeutic levels of F.IX were achieved at the highest dose tested; (iii) duration of expression at therapeutic levels was limited to a period of ∼8 weeks; (iv) a gradual decline in F.IX was accompanied by a transient asymptomatic elevation of liver transaminases that resolved without treatment. Further studies suggested that destruction of transduced hepatocytes by cell-mediated immunity targeting antigens of the AAV capsid caused both the decline in F.IX and the transient transaminitis. We conclude that rAAV-2 vectors can transduce human hepatocytes in vivo to result in therapeutically relevant levels of F.IX, but that future studies in humans may require immunomodulation to achieve long-term expression*.

Evidence for gene transfer and expression of factor IX in haemophilia B patients treated with an AAV vector.

Pre-clinical studies in mice and haemophilic dogs have shown that introduction of an adeno-associated viral (AAV) vector encoding blood coagulation factor IX (F.IX) into skeletal muscle results in sustained expression of F.IX at levels sufficient to correct the haemophilic phenotype. On the basis of these data and additional pre-clinical studies demonstrating an absence of vector-related toxicity, we initiated a clinical study of intramuscular injection of an AAV vector expressing human F.IX in adults with severe haemophilia B. The study has a dose-escalation design, and all patients have now been enrolled in the initial dose cohort (2×1011 vg/kg). Assessment in the first three patients of safety and gene transfer and expression show no evidence of germline transmission of vector sequences or formation of inhibitory antibodies against F.IX. We found that the vector sequences are present in muscle by PCR and Southern-blot analyses of muscle biopsies and we demonstrated expression of F.IX by immunohistochemistry. We observed modest changes in clinical endpoints including circulating levels of F.IX and frequency of F.IX protein infusion. The evidence of gene expression at low doses of vector suggests that dose calculations based on animal data may have overestimated the amount of vector required to achieve therapeutic levels in humans, and that the approach offers the possibility of converting severe haemophilia B to a milder form of the disease.

CD8 + T-cell responses to adeno-associated virus capsid in humans

Hepatic adeno-associated virus (AAV)-serotype 2 mediatedgene transfer results in transgene product expression that is sustained in experimental animals but not in human subjects. We hypothesize that this is caused by rejection of transduced hepatocytes by AAV capsid–specific memory CD8+ T cells reactivated by AAV vectors. Here we show that healthy subjects carry AAV capsid–specific CD8+ T cells and that AAV-mediated gene transfer results in their expansion. No such expansion occurs in mice after AAV-mediated gene transfer. In addition, we show that AAV-2 induced human T cells proliferate upon exposure to alternate AAV serotypes, indicating that other serotypes are unlikely to evade capsid-specific immune responses.

Dose of Prophylactic Platelet Transfusions and Prevention of Hemorrhage

BACKGROUND We conducted a trial of prophylactic platelet transfusions to evaluate the effect of platelet dose on bleeding in patients with hypoproliferative thrombocytopenia. METHODS We randomly assigned hospitalized patients undergoing hematopoietic stem-cell transplantation or chemotherapy for hematologic cancers or solid tumors to receive prophylactic platelet transfusions at a low dose, a medium dose, or a high dose (1.1x10(11), 2.2x10(11), or 4.4x10(11) platelets per square meter of body-surface area, respectively), when morning platelet counts were 10,000 per cubic millimeter or lower. Clinical signs of bleeding were assessed daily. The primary end point was bleeding of grade 2 or higher (as defined on the basis of World Health Organization criteria). RESULTS In the 1272 patients who received at least one platelet transfusion, the primary end point was observed in 71%, 69%, and 70% of the patients in the low-dose group, the medium-dose group, and the high-dose group, respectively (differences were not significant). The incidences of higher grades of bleeding, and other adverse events, were similar among the three groups. The median number of platelets transfused was significantly lower in the low-dose group (9.25x10(11)) than in the medium-dose group (11.25x10(11)) or the high-dose group (19.63x10(11)) (P=0.002 for low vs. medium, P<0.001 for high vs. low and high vs. medium), but the median number of platelet transfusions given was significantly higher in the low-dose group (five, vs. three in the medium-dose and three in the high-dose group; P<0.001 for low vs. medium and low vs. high). Bleeding occurred on 25% of the study days on which morning platelet counts were 5000 per cubic millimeter or lower, as compared with 17% of study days on which platelet counts were 6000 to 80,000 per cubic millimeter (P<0.001). CONCLUSIONS Low doses of platelets administered as a prophylactic transfusion led to a decreased number of platelets transfused per patient but an increased number of transfusions given. At doses between 1.1x10(11) and 4.4x10(11) platelets per square meter, the number of platelets in the prophylactic transfusion had no effect on the incidence of bleeding. (ClinicalTrials.gov number, NCT00128713.)

Guidelines for assessing appropriateness of pediatric transfusion

R ecent advances in donor screening, blood testing before transfusion, and modifications made to collected components, with irradiation as an example, make the blood supply safer than ever before. Nonetheless, blood components should only be transfused when risks and benefits have been carefully weighed.1-5 Particular consideration is required when transfusing preterm infants, the most heavily transfused patient group in the tertiary care setting, with the greatest potential for longevity.6-9 Recent data have demonstrated that transfusion practices vary tremendously, particularly in preterm infants.10 Establishing criteria for appropriate transfusion practice is important to ensure that clear-cut benefits are derived from the administration of this sometimes limited resource. In addition, the Joint Commission for the Accreditation of Health Care Organizations requires review of the appropriateness of all transfusions to correct transfusion practices that deviate from standard practice and that the use of blood and blood components be reviewed on a continuing basis, as part of a required performance-improvement function.11 Review for under-transfusion should also be considered. This paper has been written to help transfusion services and transfusion committees have a starting point to establish their own audit guidelines. References are included for each institution to evaluate as they embark upon this process. Transfusion medicine specialists who are not well versed in the special needs of neonates, as well as generalists who direct the transfusion service but lack specific expertise, can use this document and its references to initiate guideline development. These guidelines, representing the opinions of the authors and incorporating evidence-based data where it exists, have been designed to facilitate uniform transfusion practice whenever possible. Elements of transfusion practice, which should also be reviewed, include the documentation of informed consent as well as completion of transfusion records.11,12 Transfusion practice guidelines should not serve as medical indications for transfusion, nor can they be all inclusive. The appropriateness for most of these transfusion guidelines has been demonstrated in published reports. It should be pointed out that neonatal transfusion medicine is an evolving discipline. Because of the fragile clinical status of these small patients, it is difficult to design randomized controlled trials with enough statistical power to produce ironclad data. A great majority of the papers written about neonatal transfusion are practice oriented and derived by consensus. Therefore, adapting published literature to be used when creating transfusion audit guidelines for neonates should be done on an individualized basis.13-15 In certain selected clinical situations, transfusion events that deviate from the proposed guidelines may be considered appropriate. Scientific data, as well as a review of the patient’s chart, can be helpful in evaluating the appropriateness of transfusion events that deviate from guidelines.16,17 Physicians should clearly document, in writing, the indication for each transfusion administered and perform an assessment of the efficacy of the transfusion (e.g., relief of symptoms of anemia, cessation of bleeding). Parental informed consent, a process that includes delineating risks, benefits, and alternatives to transfusion, must be obtained in accordance with all applicable local, state, and national regulatory requirements. ObABBREVIATIONS: DIC = disseminated intravascular coagulation; ECMO = extracorporeal membrane oxygenation; ITP = idiopathic thrombocytopenic purpura; PCC = prothrombin complex concentrates; TA-GVHD = transfusion-associated GVHD; UCB = umbilical cord blood; WB = whole blood.

Treatment with sirolimus results in complete responses in patients with autoimmune lymphoproliferative syndrome

We hypothesized that sirolimus, an mTOR inhibitor, may be effective in patients with autoimmune lymphoproliferative syndrome (ALPS) and treated patients who were intolerant to or failed other therapies. Four patients were treated for autoimmune cytopenias; all had a rapid complete or near complete response. Two patients were treated for autoimmune arthritis and colitis, demonstrating marked improvement. Three patients had complete resolution of lymphadenopathy and splenomegaly and all patients had a reduction in double negative T cells, a population hallmark of the disease. Based on these significant responses, we recommend that sirolimus be considered as second‐line therapy for patients with steroid‐refractory disease.

Modern management of haemophilic arthropathy

Currently available factor concentrates for treatment of patients with haemophilia are virally inactivated or are made by recombinant technology and their broad use in developed nations has resulted in the dramatic elimination of the treatment‐related viral illnesses that decimated the haemophilia community in the late 20th century. The major morbidity experienced by patients with haemophilia today is joint disease, a result of repeated bleeding episodes into joint spaces. Although administration of factor concentrates to prevent bleeding has been demonstrated to prevent haemophilic joint disease when applied assiduously, repeated bleeding episodes induce synovitis that is irreversible and may progress despite subsequent prophylaxis. Surgical and nuclear medicine interventions are available to reduce the pain of haemophilic arthropathy and to reduce further bleeding episodes. Patients with high titre inhibitors are at great risk for the development of joint disease and present the greatest therapeutic challenges when joint surgery is needed.

Recombinant human erythropoietin reduces the need for erythrocyte and platelet transfusions in pediatric patients with sarcoma: A randomized, double-blind, placebo-controlled trial

OBJECTIVE To evaluate the effect of recombinant human erythropoietin (EPO) and iron supplementation on transfusion requirements in pediatric patients with sarcoma who were receiving chemotherapy, we performed a double-blind, placebo-controlled, randomized trial. METHODS Twenty-four pediatric patients with malignant solid tumors were randomly assigned to receive either placebo (saline solution) or EPO for a 16-week study period. The starting dose was 150 IU/kg per dose three times a week and was escalated by 50 IU/kg per dose increments monthly until packed red blood cell (PRBC) transfusion independence was achieved or a dosage of 300 IU/kg per dose was reached. Iron supplementation was prescribed at a dose of 6 mg of elemental iron per kilogram daily. The primary study end point was the comparison of PRBC transfusion requirements in the two groups. RESULTS Of 24 patients, 20 were evaluable for response. The median PRBC transfusion requirement during the 16-week period was 23 ml/kg in EPO-treated patients versus 80 ml/kg in placebo patients (p = 0.02). The median number of single-donor platelet units transfused was zero in the EPO-treated patients compared with four in the placebo group (p = 0.005). No statistical difference in the intensity of bone marrow suppression was seen, as measured by the median number of complete blood cell counts with an absolute neutrophil count of < 1000 cells/microliter. CONCLUSIONS Treatment with EPO and iron significantly reduces PRBC transfusions in pediatric patients receiving concomitant chemotherapy for malignant sarcomas. A decrease in the number of platelet transfusions was also seen and deserves further study.

Diagnosis and Management of Iron-induced Heart Disease in Cooley's Anemia

Abstract: Patients with homozygous β‐thalassemia are chronically transfused and, if not assiduously chelated, are at risk for cardiac dysfunction. Available data suggest that even in optimally chelated patients, cardiac pathology is abnormal secondary to iron deposition, fibrosis, hypertrophy, and the structural effects of chronic anemia. Evidence of myopericarditis may also be found. Cardiac performance is usually only subtly affected, primarily with diastolic abnormalities not routinely detected on echocardiograms or nuclear scan. In poorly chelated patients, severe heart failure occurs and is easily predictable but invariably fatal, despite treatment with diuretics, vasodilators, inotropes, and antiarrhythmics. Based on successful prevention of heart failure with ACE inhibitors in other forms of cardiomyopathy, we suggest multicenter trials to explore methods to stabilize cardiac function in patients at risk for iron‐induced heart disease. Long‐term adverse effects of iron deposition, diastolic dysfunction, and abnormal hormone regulation need to be quantitated in patients reaching their third and fourth decades when the potential for ischemic cardiac disease could compound cardiac dysfunction.

Identifying autoimmune lymphoproliferative syndrome in children with Evans syndrome: a multi-institutional study

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of abnormal lymphocyte survival caused by dysregulation of the Fas apoptotic pathway. Clinical manifestations of ALPS include autoimmune cytopenias, organomegaly, and lymphadenopathy. These findings overlap with Evans syndrome (ES), defined by presence of at least 2 autoimmune cytopenias. We hypothesized a subset of patients with ES have ALPS and tested 45 children at 22 institutions, measuring peripheral blood double-negative T cells (DNTs) and Fas-mediated apoptosis. ALPS was diagnosed in 47% of patients tested. Markedly elevated DNTs (> or = 5%) were a strong predictor of ALPS (positive predictive value = 94%), whereas no patients with DNTs less than 2.5% had ALPS on apoptosis testing. Severity of cytopenias and elevated immunoglobulin levels also predicted ALPS. This is the largest published series describing children with ES and documents a high rate of ALPS among pediatric ES patients. These data suggest that children with ES should be screened for ALPS with DNTs.