Auto CD34+PBSC, transduced with a lentiviral vector encoding the B domain deleted from of human coagulation factor VIII for Hemophilia A

Hemophilia is typically treated within the first few years after birth by replacement of missing factors by transfusion and when needed, splenic or bone marrow transplantation. Immunomodulators such as interferon alpha may also be used. The long term prognosis is determined by the degree of bleeding tendency in the affected person and is inversely related to the level of activity of factor VIII in the body.

There are about one million cases of hemophilia in the United States, about 3.5 million hemophilia A and one million hemophilia B cases, making it the second most common genetic blood disease in the United States.

Hemophilia B is the most common hemophilia and an X-linked recessive disease that is characterized by an absence of blood clotting. Treatment for hemophilia A is limited in scope to correction of bleeding events in children and adults. Older patients, especially those over 50 years of age, are susceptible to bleeding into joints, muscles, and the skin. Older patients also develop hemodilution, which may make them more susceptible to bruising and excessive bleeding. Hemophilia B occurs about as often in males as females.\n

Hemophilia can be prevented by gene and FVIII transfusion. Hemophilia may be effectively treated by FVIII replacement therapy. Heparin can be used to prevent thrombosis, especially for infants without anticoagulation therapy.

There are various types of hemophilia which lead to different symptoms and signs. Genetic traits and environmental factors (exposure to trauma and trauma-related exposures) are thought to contribute to the expression of these traits. Exposure to blood products in utero may play a role. Hemophiliac babies are screened for hemophilia a, in the form of an immunological technique to detect antibodies found in babies of homozygous carriers of the factor VIII gene. These antibodies would persist postnatally, as the child would be exposed to blood products later in life through prophylaxis. If the child has the gene, he or she will be affected by the disease.

Signs of hemophilia a include bleeding tendencies and clotting factors. They may include prolonged bleeding time, bleeding time after surgery, petechiae from trauma, or bruising from surgery. An infant with a history of bleeding problems or bruising from trauma should be assessed by hematologist, which may be necessary for hemostatic factors. There are no standard bleeding time tests for hemophilia a; however, the following tests should be done to help determine the severity of the clotting deficiencies:\n1. Coagulation factor tests\n2. Immunoassay for von Willebrand factor (vWF)\n3.

Autologous CD34(+) pbsc(+) PBMC transduced by a lentiviral vector encoding the b domain deleted from of human coagulation factor viii resulted in durable, safe and efficient hematopoietic recovery from an immunodeficient patient with hemophilia a.

The data suggest that hbF-viii vector/CD34 can be used alone or with other drug treatments; however, it cannot be recommended as a stand-alone treatment for treatment of thrombocytopaenia\n.

A gene therapy approach in which CD34+ PBPCs are genetically engineered with the b domain deleted from Factor VIII has been successfully developed. As shown in several animal models, gene transfer into these cells resulted in functional recovery after a transfusion by the treated CD34+ cells in hemophilic mice. Moreover, in vitro, transduced CD34+ PBPCs have been found to proliferate in the presence of hemophilus factor. In addition, gene therapy with CD34+ PBPCs could be safely administered without undue toxicity. Results from a recent clinical trial constitute further proof of concept to develop a feasible and safe gene therapy protocol for the treatment of hemophilic patients.

The present data suggest that the CD34(+):p(bpdc) vector containing the B domain from FVIII improves HXQOL compared to FVIII as evidenced by the effect on the K-6 score. Further investigations of this strategy to address these deficits may therefore have great therapeutic promise.

This approach may provide an efficient and highly effective treatment of hematologic malignancies with low risk of toxic side effects. Recent findings suggest that the use of an RNAi-mediated strategy to selectively silence the gene encoding Pbsc on the gene-transduced CD34+ cells might allow the elimination of leukemic CD34+ cells without interference with normal hematopoiesis.