title: Stem cell selection in vivo using foamy vectors cures canine pyruvate kinase deficiency.
abstract: BACKGROUND
  Hematopoietic stem cell (HSC) gene therapy has cured immunodeficiencies including X-linked severe combined immunodeficiency (SCID-X1) and adenine deaminase deficiency (ADA). For these immunodeficiencies corrected cells have a selective advantage in vivo, and low numbers of gene-modified cells are sufficient to provide therapeutic benefit. Strategies to efficiently transduce and/or expand long-term repopulating cells in vivo are needed for treatment of diseases that require higher levels of corrected cells, such as hemoglobinopathies. Here we expanded corrected stem cells in vivo in a canine model of a severe erythroid disease, pyruvate kinase deficiency.
  
  
  RESULTS
  We used a foamy virus (FV) vector expressing the P140K mutant of methylguanine methyltransferase (MGMTP140K) for in vivo expansion of corrected hematopoietic repopulating cells. FV vectors are attractive gene transfer vectors for hematopoietic stem cell gene therapy since they efficiently transduce repopulating cells and may be safer than more commonly used gammaretroviral vectors. Following transplantation with HSCs transduced ex vivo using a tri-cistronic FV vector that expressed EGFP, R-type pyruvate kinase, and MGMTP140K, we were able to increase marking from approximately 3.5% to 33% in myeloid long-term repopulating cells resulting in a functional cure.
  
  
  CONCLUSIONS
  Here we describe in one affected dog a functional cure for a severe erythroid disease using stem cell selection in vivo. In addition to providing a potential cure for patients with pyruvate kinase deficiency, in vivo selection using foamy vectors with MGMTP140K has broad potential for several hematopoietic diseases including hemoglobinopathies.
authors.affiliation: Clinical Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA.
authors.forename: Grant D
authors.initials: GD
authors.lastname: Trobridge
authors.forename: Brian C
authors.initials: BC
authors.lastname: Beard
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wu
authors.forename: Christina
authors.initials: C
authors.lastname: Ironside
authors.forename: Punam
authors.initials: P
authors.lastname: Malik
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Kiem
mesh_terms: D000208:Acute Disease; D000746:Anemia, Hemolytic, Congenital Nonspherocytic / Q000201:enzymology / Q000235:genetics / Q000628:therapy*; D000818:Animals; D015254:DNA Modification Methylases / Q000235:genetics* / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D004285:Dogs; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D009154:Mutation; D011770:Pyruvate Kinase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D015323:Pyruvate Metabolism, Inborn Errors / Q000201:enzymology / Q000235:genetics / Q000628:therapy*; D016092:Spumavirus / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D014161:Transduction, Genetic; D019076:Transgenes; D016896:Treatment Outcome; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D025521:Tumor Suppressor Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D011770:Pyruvate Kinase; D045643:DNA Repair Enzymes