J. Nathan Hagstrom

Long-term correction of canine hemophilia B by gene transfer of blood coagulation factor IX mediated by adeno-associated viral vector

Hemophilia B is a severe X-linked bleeding diathesis caused by the absence of functional blood coagulation factor IX, and is an excellent candidate for treatment of a genetic disease by gene therapy. Using an adeno-associated viral vector, we demonstrate sustained expression (>17 months) of factor IX in a large-animal model at levels that would have a therapeutic effect in humans (up to 70 ng/ml, adequate to achieve phenotypic correction, in an animal injected with 8.5 × 1012 vector particles/kg). The five hemophilia B dogs treated showed stable, vector dose-dependent partial correction of the whole blood clotting time and, at higher doses, of the activated partial thromboplastin time. In contrast to other viral gene delivery systems, this minimally invasive procedure, consisting of a series of percutaneous intramuscular injections at a single timepoint, was not associated with local or systemic toxicity. Efficient gene transfer to muscle was shown by immunofluorescence staining and DNA analysis of biopsied tissue. Immune responses against factor IX were either absent or transient. These data provide strong support for the feasibility of the approach for therapy of human subjects.

Prevalence of the factor V Leiden mutation in children and neonates with thromboembolic disease

Abstract Objective: Resistance to activated protein C (APC) has been identified as a risk factor for thrombotic disease in adults. In over 90% of cases, the basis for the APC resistance is a mutation in the coagulation factor V gene (factor V Leiden) that renders the protein more resistant to inactivation by APC. We sought to determine the prevalence of the factor V Leiden (FVL) mutation in neonates and children who had experienced an arterial or venous thromboembolic event. Study design: We retrospectively analyzed the clinical records of 33 neonates and 52 children with thromboembolic disease. Screening for the FVL mutation was performed by DNA analysis, allowing for identification of patients as normal, heterozygous, or homozygous. Results: Of the 85 patients studied, 12 (14.1%) were heterozygous for FVL; none were homozygous. Of the 47 patients who had arterial central nervous system events, 8 (17%) were positive for the FVL mutation, including 6 of 22 (27%) neonates. Of those patients who had a venous thrombosis, 4 of 32 (12.5%) were FVL positive. None of the 85 patients had protein C deficiency, 3.5% had protein S deficiency, 1.2% had antithrombin III deficiency, and 16.5% had anti-phospholipid antibodies. Conclusion: These data suggest that the FVL mutation plays a role in the development of arterial and venous thrombotic events in neonates and children. (J Pediatr 1998;133:777-81)

Use of Low-Dose Ketamine Infusion For Pediatric Patients With Sickle Cell Disease-Related Pain: A Case Series.

ObjectivesSickle cell disease-related pain is difficult to treat adequately. Pain secondary to vasoocclusive episodes (VOE) may be unresponsive to high-dose intravenous opiates. Alternative treatment options for VOE are needed. We sought to review our experience with low-dose ketamine for children hospitalized with VOE. MethodsRetrospective medical chart reviews were conducted for hospitalized patients treated with ketamine for sickle cell VOE. Data gathered included vital signs, pain scores, opiate utilization, and adverse events. ResultsFive children and adolescents received a low-dose ketamine infusion for the treatment of sickle cell-related pain. Four received the infusion in addition to opiates (delivered via patient controlled analgesia) as a rescue intervention after several days of inadequate pain relief and 1 patient received ketamine in place of opiates. Two of the 5 patients achieved what seems to be clinically significant pain control with a low-dose ketamine infusion, whereas 1 additional patient had significant reduction in opiate utilization. DiscussionFurther research into ketamine for vasoocclusive pain is warranted.

Identification of risk factors for an unsuccessful transition from pediatric to adult sickle cell disease care

A successful transition from pediatric to adult sickle cell disease (SCD) care is paramount to continued improvements in survival. In order to enhance transition success, our pediatric SCD transition process was modified to include combined adult and pediatric provider clinics that incorporated participation by our local SCD community‐based organization. All children ages 16 and over participated in this newly‐formed transition program.

Retrospective evaluation of pain assessment and treatment for acute vasoocclusive episodes in children with sickle cell disease.

This study was conducted to assess the care of pediatric patients hospitalized for sickle cell disease‐related vasoocclusive episodes (VOE). The aim of this research was to illustrate the course of pain scores and methods of therapeutic intervention during hospitalization.

Gene therapy for treatment of inherited haematological disorders

Gene therapy, a molecular medicine based on vector-mediated transfer of therapeutic genes, holds promise for a cure of monogenetic inherited diseases. In recent years, tremendous progress has been reported in the treatment of haematological disorders: clinical trials in severe combined immune deficiencies have been successful by using retroviral vectors to express target genes in haematopoietic stem cells, which after transplantation efficiently reconstituted the immune system concomitant with substantial improvement in the clinical status of patients. Conversely, unexpected adverse events were also encountered. In other work, progress towards clinical studies on ex vivo gene transfer for Fanconi anaemia and haemoglobinopathies has been made. Each approach features a unique treatment strategy and also faces various impediments to success. In the case of the X-linked bleeding disorder haemophilia, several Phase I/II clinical trials were conducted, including in vivo administration of viral vectors to skeletal muscle and liver. Adeno-associated viral gene transfer of coagulation Factor IX has been documented in human subjects, reaching therapeutic levels after infusion into a hepatic blood vessel. However, sustained expression of therapeutic levels (as shown in large animal models of haemophilia) has not yet been achieved in humans. In general, long-term follow-up will be important for assessment of the safety of all existing gene therapy strategies.

Do Children with Sickle Cell Disease Receive Disparate Care for Pain in the Emergency Department

BACKGROUND There may be disparities in pain management practice in the emergency department (ED) for sickle cell disease patients (SCD) with vaso-occlusive episodes (VOE). OBJECTIVES To compare pain management practice for children who presented to the ED with VOE to those with isolated long bone fractures (LBF). METHODS Children who presented with a VOE or a LBF to a childrens hospital ED during 2005 were included. A retrospective medical chart review was conducted for each patient visit. Data collected included demographics, pain scores, time from triage to analgesia, and analgesic intervention. RESULTS Seventy-seven patients with SCD had 152 visits to the ED for pain, and 219 patients had 221 visits for LBF. Fifty-five patients (108 visits) with SCD and 123 patients (124 visits) with LBF received opiates. Subsequent analysis was done on these groups. Patients with SCD were older, less likely to be male and more likely to be African-American than the LBF group. Patients with SCD had higher triage pain scores (7.7 ± 2.5 vs. 6.7 ± 3.0, p = 0.005) and spent less time in the waiting room (7.4 ± 9.0 vs. 12.1 ± 26.8 min, p = 0.10), were given higher initial opiate doses (0.09 ± 0.03 vs. 0.07 ± 0.03 mg/kg morphine, p < 0.001); however, time from triage to analgesic intervention did not differ (69.0 ± 42.6 vs. 70.4 ± 57.1 min, p = 0.92). CONCLUSIONS No disparities in care for children with sickle cell pain were identified. More timely administration of opiates needs to be encouraged, assuming other factors such as time of day, ED census, and acuity permit.

Gene Therapy for Hereditary Hematological Disorders

The year 2000 saw the first successful treatment of a genetic disorder by gene therapy. Pediatric patients with X-linked severe combined immunodeficiency disorder (SCID-X1) received autologous CD34+ hematopoietic cells following ex vivo gene transfer using a retroviral vector, with subsequent demonstration of improved immune responses. A number of preclinical and clinical studies have been conducted with the aim of developing gene therapy for hemophilia, Fanconi anemia, sickle cell disease, β-thalassemia, chronic granulomatous disease, and other inherited hematological disorders. The greatest advances in novel approaches toward treatment of hematological disorders have been made in hemophilia, with 3 current phase I clinical trials ongoing. Two trials are investigating the safety and feasibility of utilizing either an ex vivo, non-viral gene transfer technique or an intravenous infusion of a retroviral vector to treat adults with severe hemophilia A (factor VIII deficiency). The third study involves intramuscular administration of an adeno-associated viral (AAV) vector for expression of factor IX in adult patients with hemophilia B. Results from this study and from preclinical studies preceding the trial demonstrate that it is possible to safely administer high doses of a viral vector in vivo.

PREVALENCE OF THE FACTOR V LEIDEN MUTATION IN CHILDREN AND NEONATES WITH THROMBOEMBOLIC DISEASE. ▴ 917

OBJECTIVE Resistance to activated protein C (APC) has been identified as a risk factor for thrombotic disease in adults. In over 90% of cases, the basis for the APC resistance is a mutation in the coagulation factor V gene (factor V Leiden) that renders the protein more resistant to inactivation by APC. We sought to determine the prevalence of the factor V Leiden (FVL) mutation in neonates and children who had experienced an arterial or venous thromboembolic event. STUDY DESIGN We retrospectively analyzed the clinical records of 33 neonates and 52 children with thromboembolic disease. Screening for the FVL mutation was performed by DNA analysis, allowing for identification of patients as normal, heterozygous, or homozygous. RESULTS Of the 85 patients studied, 12 (14.1%) were heterozygous for FVL; none were homozygous. Of the 47 patients who had arterial central nervous system events, 8 (17%) were positive for the FVL mutation, including 6 of 22 (27%) neonates. Of those patients who had a venous thrombosis, 4 of 32 (12.5%) were FVL positive. None of the 85 patients had protein C deficiency, 3.5% had protein S deficiency, 1.2% had antithrombin III deficiency, and 16.5% had anti-phospholipid antibodies. CONCLUSION These data suggest that the FVL mutation plays a role in the development of arterial and venous thrombotic events in neonates and children.