title: Syngeneic transplantation of hematopoietic stem cells that are genetically modified to express factor VIII in platelets restores hemostasis to hemophilia A mice with preexisting FVIII immunity.
abstract: Although genetic induction of factor VIII (FVIII) expression in platelets can restore hemostasis in hemophilia A mice, this approach has not been studied in the clinical setting of preexisting FVIII inhibitory antibodies to determine whether such antibodies would affect therapeutic engraftment. We generated a line of transgenic mice (2bF8) that express FVIII only in platelets using the platelet-specific alphaIIb promoter and bred this 2bF8 transgene into a FVIII(null) background. Bone marrow (BM) from heterozygous 2bF8 transgenic (2bF8(tg+/-)) mice was transplanted into immunized FVIII(null) mice after lethal or sublethal irradiation. After BM reconstitution, 85% of recipients survived tail clipping when the 1100-cGy (myeloablative) regimen was used, 85.7% of recipients survived when 660-cGy (nonmyeloablative) regimens were used, and 60% of recipients survived when the recipients were conditioned with 440 cGy. Our further studies showed that transplantation with 1% to 5% 2bF8(tg+/-) BM cells still improved hemostasis in hemophilia A mice with inhibitors. These results demonstrate that the presence of FVIII-specific immunity in recipients does not negate engraftment of 2bF8 genetically modified hematopoietic stem cells, and transplantation of these hematopoietic stem cells can efficiently restore hemostasis to hemophilic mice with preexisting inhibitory antibodies under either myeloablative or nonmyeloablative regimens.
authors.affiliation: Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA. qizhen.shi@bcw.edu
authors.forename: Qizhen
authors.initials: Q
authors.lastname: Shi
authors.forename: Scot A
authors.initials: SA
authors.lastname: Fahs
authors.forename: David A
authors.initials: DA
authors.lastname: Wilcox
authors.forename: Erin L
authors.initials: EL
authors.lastname: Kuether
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Morateck
authors.forename: Nicole
authors.initials: N
authors.lastname: Mareno
authors.forename: Hartmut
authors.initials: H
authors.lastname: Weiler
authors.forename: Robert R
authors.initials: RR
authors.lastname: Montgomery
mesh_terms: D000818:Animals; D001681:Biological Assay; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D005169:Factor VIII / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*; D015316:Genetic Therapy; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D006467:Hemophilia A / Q000235:genetics* / Q000628:therapy; D006487:Hemostasis; D007109:Immunity; D007114:Immunization; D051379:Mice; D019653:Myeloablative Agonists / Q000494:pharmacology; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014170:Transformation, Genetic; D019076:Transgenes; D019172:Transplantation Conditioning; D014185:Transplantation, Isogeneic
chemical_list: D019653:Myeloablative Agonists; D005169:Factor VIII