title: Cytotoxic T lymphocyte responses to transgene product, not adeno-associated viral capsid protein, limit transgene expression in mice.
abstract: The use of adeno-associated viral (AAV) vectors for gene replacement therapy is currently being explored in several clinical indications. However, reports have suggested that input capsid proteins from AAV-2 vector particles may result in the stimulation of cytotoxic T lymphocyte (CTL) responses that can result in a loss of transduced cells. To explore the impact of anti-AAV CTLs on AAV-mediated transgene expression, both immunocompetent C57BL=6 mice and B cell-deficient muMT mice were immunized against the AAV2 capsid protein (Cap) and were injected intravenously with an AAV-2 vector encoding alpha-galactosidase (alpha-Gal). C57BL=6 mice, which developed both CTL and neutralizing antibody responses against Cap, failed to show any detectable alpha-Gal expression. In contrast, serum alpha-Gal levels comparable to those of naive mice were observed in muMT mice despite the presence of robust CTL activity against Cap, indicating that preexisting Cap-specific CTLs did not have any effect on the magnitude and duration of transgene expression. The same strategy was used to assess the impact of CTLs against the alpha-Gal transgene product on AAV-mediated gene delivery and persistence of transgene expression. Preimmunization of muMT mice with an Ad=alpha-Gal vector induced a robust CTL response to alpha-Gal. When these mice were injected with AAV2=alpha-Gal vector, initial levels of alpha-Gal expression were reduced by more than 1 log and became undetectable by 2 weeks postinjection. Overall, our results indicate that CTLs against the transgene product as opposed to AAV capsid protein are more likely to interfere with AAV transgene expression.
authors.affiliation: Department of Immunotherapy Research, Genzyme, Framingham, MA 01701, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Siders
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Shields
authors.forename: Johanne
authors.initials: J
authors.lastname: Kaplan
authors.forename: Michael
authors.initials: M
authors.lastname: Lukason
authors.forename: Lisa
authors.initials: L
authors.lastname: Woodworth
authors.forename: Sam
authors.initials: S
authors.lastname: Wadsworth
authors.forename: Abraham
authors.initials: A
authors.lastname: Scaria
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000229:Dependovirus / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015316:Genetic Therapy; D005822:Genetic Vectors; D007121:Immunocompetence; D016867:Immunocompromised Host; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D019076:Transgenes / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D000519:alpha-Galactosidase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D036022:Capsid Proteins; D010455:Peptides; D000519:alpha-Galactosidase