title: Epitope mapping of human anti-adeno-associated virus type 2 neutralizing antibodies: implications for gene therapy and virus structure.
abstract: Recombinant adeno-associated virus type 2 (AAV) is a common vector used in human gene therapy protocols. We characterized the humoral immune response to AAV and observed that 80% of normal human subjects have anti-AAV antibodies and that 18% have neutralizing antibodies. To analyze the effect of neutralizing antibodies on AAV readministration, we attempted to deliver recombinant AAV expressing human factor IX (AAV-hFIX) intraportally into the livers of mice which had been preexposed to AAV and shown to harbor a neutralizing antibody response. While all naive control mice expressed hFIX following administration of AAV-hFIX, none of the mice with preexisting immunity expressed hFIX, even after transient immunosuppression at the time of the second administration with anti-CD4 or anti-CD40L antibodies. This suggests that preexisting immunity to AAV, as measured by a neutralizing antibody response, may limit AAV-mediated gene delivery. Using human sera in an enzyme-linked immunosorbent assay for AAV and a capsid peptide scan library to block antibody binding, we mapped seven regions of the AAV capsid containing immunogenic epitopes. Using pools of these peptides to inhibit the binding of neutralizing antibodies, we have identified a subset of six peptides which potentially reconstitute a single neutralizing epitope. This information may allow the design of reverse genetic approaches to circumvent the preexisting immunity that can be encountered in some individuals.
authors.affiliation: Department of Preclinical Biology and Immunology, Cell Genesys Inc., Foster City, California 94404, USA.
authors.forename: M
authors.initials: M
authors.lastname: Moskalenko
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: van Roey
authors.forename: B A
authors.initials: BA
authors.lastname: Donahue
authors.forename: R O
authors.initials: RO
authors.lastname: Snyder
authors.forename: J G
authors.initials: JG
authors.lastname: McArthur
authors.forename: S D
authors.initials: SD
authors.lastname: Patel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology*; D002461:Cell Line, Transformed; D000229:Dependovirus / Q000276:immunology*; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D005164:Factor IX / Q000235:genetics; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000276:immunology*; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins; D005164:Factor IX; D001616:beta-Galactosidase