title: Induction of Immune Tolerance to Foreign Protein via Adeno-Associated Viral Vector Gene Transfer in Mid-Gestation Fetal Sheep.
abstract: A major limitation to adeno-associated virus (AAV) gene therapy is the generation of host immune responses to viral vector antigens and the transgene product. The ability to induce immune tolerance to foreign protein has the potential to overcome this host immunity. Acquisition and maintenance of tolerance to viral vector antigens and transgene products may also permit repeat administration thereby enhancing therapeutic efficacy. In utero gene transfer (IUGT) takes advantage of the immunologic immaturity of the fetus to induce immune tolerance to foreign antigens. In this large animal study, in utero administration of AAV6.2, AAV8 and AAV9 expressing green fluorescent protein (GFP) to ~60 day fetal sheep (term: ~150 days) was performed. Transgene expression and postnatal immune tolerance to GFP and viral antigens were assessed. We demonstrate 1) hepatic expression of GFP 1 month following in utero administration of AAV6.2.GFP and AAV8.GFP, 2) in utero recipients of either AAV6.2.GFP or AAV8.GFP fail to mount an anti-GFP antibody response following postnatal GFP challenge and lack inflammatory cellular infiltrates at the intramuscular site of immunization, 3) a serotype specific anti-AAV neutralizing antibody response is elicited following postnatal challenge of in utero recipients of AAV6.2 or AAV8 with the corresponding AAV serotype, and 4) durable hepatic GFP expression was observed up to 6 months after birth in recipients of AAV8.GFP but expression was lost between 1 and 6 months of age in recipients of AAV6.2.GFP. The current study demonstrates, in a preclinical large animal model, the potential of IUGT to achieve host immune tolerance to the viral vector transgene product but also suggests that a single exposure to the vector capsid proteins at the time of IUGT is inadequate to induce tolerance to viral vector antigens.
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Marcus G
authors.initials: MG
authors.lastname: Davey
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: John S
authors.initials: JS
authors.lastname: Riley
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Abigail
authors.initials: A
authors.lastname: Andrews
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Alec
authors.initials: A
authors.lastname: Tyminski
authors.affiliation: Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
authors.forename: Maria
authors.initials: M
authors.lastname: Limberis
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Pogoriler
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Emily
authors.initials: E
authors.lastname: Partridge
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Aliza
authors.initials: A
authors.lastname: Olive
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Holly L
authors.initials: HL
authors.lastname: Hedrick
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: Alan W
authors.initials: AW
authors.lastname: Flake
authors.affiliation: Center for Fetal Research, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America.
authors.forename: William H
authors.initials: WH
authors.lastname: Peranteau
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D036022:Capsid Proteins / Q000276:immunology*; D000229:Dependovirus / Q000235:genetics*; D005260:Female; D005333:Fetus / Q000276:immunology*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000276:immunology*; D007108:Immune Tolerance / Q000276:immunology*; D056724:Immunity, Humoral / Q000276:immunology; D008099:Liver / Q000378:metabolism; D011247:Pregnancy; D012756:Sheep / Q000196:embryology*; D013997:Time Factors; D019076:Transgenes
chemical_list: D000906:Antibodies; D036022:Capsid Proteins; D049452:Green Fluorescent Proteins