title: Mixed hematopoietic molecular chimerism results in permanent transgene expression from retrovirally transduced hepatocytes in mice.
abstract: BACKGROUND
  Cytotoxic immune elimination of transduced hepatocytes may limit gene therapy for inherited liver diseases. Using beta-galactosidase as a marker gene, we studied whether creation of mixed beta-galactosidase molecular hematopoietic chimerism could induce tolerance to beta-galactosidase-transduced hepatocytes.
  
  
  METHODS
  Molecular hematopoietic chimerism was established in irradiated recipient mice by transplantation of either a mixture of wild-type and beta-galactosidase-transgenic bone marrow or autologous bone marrow stem cells that were transduced with beta-galactosidase lentiviral vectors. After transplantation, mice were hepatectomized and injected with beta-galactosidase recombinant retroviruses to transduce regenerating hepatocytes. We monitored the presence of beta-galactosidase-expressing hepatocytes as well as the appearance of anti-beta-galactosidase antibodies during the time.
  
  
  RESULTS
  In control animals, anti-beta-galactosidase antibodies and cytotoxic T-lymphocyte (CTL) response developed as early as 3 weeks after gene transfer. Transduced hepatocytes disappeared concomitantly. In bone marrow transplanted mice, tolerance could be observed in a significant proportion of animals. Tolerance resulted in permanent liver transgene expression and was absent unless a chimerism above 1% was achieved, demonstrating a threshold effect.
  
  
  CONCLUSIONS
  Creation of a molecular hematopoietic chimerism can result in transgene tolerance and evade immune rejection of retrovirally transduced hepatocytes. This strategy may be useful for hepatic inherited diseases in which the transgene product behaves as a non-self protein.
authors.affiliation: Biothérapies Hépatiques, CIC-INSERM 04, IMAD, CHU Hôtel-Dieu, 44093 Nantes cedex 01, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Pichard
authors.forename: Marta
authors.initials: M
authors.lastname: Bellodi-Privato
authors.forename: Jérôme
authors.initials: J
authors.lastname: Gournay
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferry
mesh_terms: D000818:Animals; D016026:Bone Marrow Transplantation; D002478:Cells, Cultured; D046528:Chimerism; D005696:Galactosidases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression; D006413:Hematopoietic System; D022781:Hepatocytes / Q000378:metabolism*; D016086:Lentivirus / Q000235:genetics* / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016133:Polymerase Chain Reaction; D014161:Transduction, Genetic; D019076:Transgenes
chemical_list: D005696:Galactosidases