title: Improved induction of immune tolerance to factor IX by hepatic AAV-8 gene transfer.
abstract: Gene therapy for hemophilia B has been shown to result in long-term expression and immune tolerance to factor IX (F.IX) after in vivo transduction of hepatocytes with adeno-associated viral (AAV-2) vectors in experimental animals. An optimized protocol was effective in several strains of mice with a factor 9 gene deletion (F9(-/-)). However, immune responses against F.IX were repeatedly observed in C3H/HeJ F9(-/-) mice. We sought to establish a gene transfer protocol that results in sustained expression without a requirement for additional manipulation of the immune system. Compared with AAV-2, AAV-8 was more efficient in transgene expression and induction of tolerance to F.IX in three different strains of wild-type mice. At equal vector doses, AAV-8 induced transgene product-specific regulatory CD4(+)CD25(+)FoxP3(+) T cells at significantly higher frequency. Moreover, sustained correction of hemophilia B in C3H/HeJ F9(-/-) mice without antibody formation was documented in all animals treated with > or =4 x 10(11) vector genomes (VG)/kg and in 80% of mice treated with 8 x 10(10) VG/kg. Therefore, it is possible to develop a gene transfer protocol that reliably induces tolerance to F.IX largely independent of genetic factors. A comparison with other studies suggests that additional parameters besides plateau levels of F.IX expression contributed to the improved success rate of tolerance induction.
authors.affiliation: Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Mario
authors.initials: M
authors.lastname: Cooper
authors.forename: Sushrusha
authors.initials: S
authors.lastname: Nayak
authors.forename: Brad E
authors.initials: BE
authors.lastname: Hoffman
authors.forename: Cox
authors.initials: C
authors.lastname: Terhorst
authors.forename: Ou
authors.initials: O
authors.lastname: Cao
authors.forename: Roland W
authors.initials: RW
authors.lastname: Herzog
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D000229:Dependovirus / Q000235:genetics*; D005164:Factor IX / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000008:administration & dosage / Q000235:genetics; D002836:Hemophilia B / Q000235:genetics / Q000276:immunology / Q000628:therapy; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D007074:Immunoglobulin G / Q000096:biosynthesis; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D013997:Time Factors; D019076:Transgenes / Q000235:genetics
chemical_list: D007074:Immunoglobulin G; D005164:Factor IX