title: Hematopoietic stem-cell gene therapy of hemophilia A incorporating a porcine factor VIII transgene and nonmyeloablative conditioning regimens.
abstract: Insufficient expression of factor VIII (fVIII) is a major hurdle in the development of successful nucleic acid treatments for hemophilia. However, we recently showed that under myeloablative and reduced-intensity total body irradiation (TBI) conditioning, transplantation of hematopoietic stem cells (HSCs) transduced with recombinant retroviruses containing B domain-deleted porcine fVIII (BDDpfVIII) sequences provides curative fVIII levels in a hemophilia A mouse model. In the current study, we tested BDDpfVIII activity after nonmyeloablative conditioning with busulfan, cyclophosphamide, or fludarabine and immunosuppressive agents CTLA4-Ig + anti-CD40L or anti-(murine)thymocyte serum (ATS). ATS is similar in action to anti-(human)thymocyte globulin (ATG), which is used clinically with busulfan in bone marrow transplantations to increase donor cell engraftment. Mice conditioned with busulfan + ATS and that received a transplant of BDDpfVIII-transduced stem-cell antigen 1-positive cells exhibited moderate levels of donor cell chimerism (between 20% and 60%) and achieved sustained fVIII levels more than 1 U/mL. Similar results were observed in mice preimmunized with human fVIII and conditioned with 5 Gy TBI + ATS or busulfan + ATS. These data demonstrate that it is possible to achieve sufficient fVIII expression after transplantation of BDDpfVIII-transduced HSCs following low-toxicity pretransplantation conditioning with targeted immunosuppression, potentially even in the context of preexisting inhibitors.
authors.affiliation: Department of Pediatrics, Aflac Cancer Center and Blood Disorders Service, Emory University and Children's Healthcare of Atlanta, GA, USA.
authors.forename: Lucienne M
authors.initials: LM
authors.lastname: Ide
authors.forename: Bagirath
authors.initials: B
authors.lastname: Gangadharan
authors.forename: Kuang-Yueh
authors.initials: KY
authors.lastname: Chiang
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Doering
authors.forename: H Trent
authors.initials: HT
authors.lastname: Spencer
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002066:Busulfan / Q000627:therapeutic use; D003520:Cyclophosphamide / Q000627:therapeutic use; D005169:Factor VIII / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods*; D006467:Hemophilia A / Q000628:therapy*; D006801:Humans; D051379:Mice; D013552:Swine; D019076:Transgenes; D019172:Transplantation Conditioning / Q000379:methods*; D014740:Vidarabine / Q000031:analogs & derivatives / Q000627:therapeutic use; D014916:Whole-Body Irradiation
chemical_list: D000970:Antineoplastic Agents; D003520:Cyclophosphamide; D005169:Factor VIII; D014740:Vidarabine; D002066:Busulfan; C024352:fludarabine