title: Cross-presentation of adeno-associated virus serotype 2 capsids activates cytotoxic T cells but does not render hepatocytes effective cytolytic targets.
abstract: Liver toxicity observed in a clinical trial of adeno-associated virus serotype 2 (AAV2) delivered systemically to patients with hemophilia was ascribed to killing of vector-transduced hepatocytes by capsid-specific T cells. This study evaluated the biology of T cell activation in response to AAV capsids in murine models. CD8(+) T cell epitopes were mapped to capsids from AAV2, AAV7, and AAV8. A tetramer generated in response to a dominant capsid epitope in BALB/c mice was shared between these AAV serotypes. Administration of AAV2 vector resulted in the activation of capsid-specific CD8(+) T cells as evidenced by binding to tetramer and production of capsid-induced interferon-gamma expression this was not observed with the AAV7 and AAV8 vectors. CD8(+) T cells specific to AAV2 capsids demonstrate functional cytolytic activity in vivo to peptide-loaded target cells. The frequency of capsid-specific T cells was much higher in liver than in blood or spleen. The performance of liver-directed AAV-mediated gene transfer was not diminished in animals with high levels of pre-existing capsid-specific T cells. We conclude that cross-presentation of AAV capsids does result in activation of cytotoxic T lymphocytes (CTLs) in a serotype-specific manner; however, there is no evidence that vector-transduced hepatocytes are targets for CTL effector activity.
authors.affiliation: Gene Therapy Program, Department of Pathology and Laboratory Medicine, Division of Transfusion Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Joanita
authors.initials: J
authors.lastname: Figueredo
authors.forename: Roberto
authors.initials: R
authors.lastname: Calcedo
authors.forename: Jianping
authors.initials: J
authors.lastname: Lin
authors.forename: James M
authors.initials: JM
authors.lastname: Wilson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002213:Capsid / Q000276:immunology*; D002465:Cell Movement; D045142:Cross-Priming; D003601:Cytotoxicity Tests, Immunologic; D000229:Dependovirus / Q000235:genetics / Q000276:immunology*; D018604:Epitope Mapping; D018984:Epitopes, T-Lymphocyte / Q000737:chemistry / Q000276:immunology; D005822:Genetic Vectors / Q000235:genetics / Q000276:immunology*; D022781:Hepatocytes / Q000276:immunology*; D008099:Liver / Q000166:cytology / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014161:Transduction, Genetic
chemical_list: D018984:Epitopes, T-Lymphocyte