title: Role of antigen-specific regulatory CD4+CD25+ T cells in tolerance induction after neonatal IP administration of AAV-hF.IX.
abstract: Neonatal AAV8-mediated Factor IX (F.IX) gene delivery was applied as a model for exploring mechanisms of tolerance induction during immune ontogeny. Intraperitoneal delivery of AAV8/ Factor IX (hF.IX) during weeks 1-4 of life, over a 20-fold dose range, directed stable hF.IX expression, correction of coagulopathy in F.IX-null hemophilia B mice, and induction of tolerance to hF.IX; however, only primary injection at 1-2 days of life enabled increasing AAV8-mediated hF.IX expression after re-administration, due to the absence of anti-viral capsid antibodies. Adoptive splenocyte transfer from tolerized mice demonstrated induction of CD4(+)CD25(+) T regulatory (T(reg)) populations that specifically suppressed anti-hF.IX antibody responses, but not responses to third party antigen. Induction of hF.IX antibodies was only observed in tolerized mice after in vivo CD4(+)CD25(+) cell depletion and hF.IX challenge. Thus, primary injection of AAV during a critical period in the first week of life does not elicit antiviral responses, enabling re-administration of AAV and augmentation of hF.IX levels. Expansion of hF.IX-specific CD4(+)CD25(+) T(regs) has a major role in tolerance induction early in immune ontogeny. Neonatal gene transfer provides a useful approach for defining the ontogeny of immune responses and may suggest approaches for inducing tolerance in the context of genetic therapies.
authors.affiliation: Department of Medicine, University of California, San Francisco, CA, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Shi
authors.forename: R
authors.initials: R
authors.lastname: Falahati
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Flebbe-Rehwaldt
authors.forename: K M L
authors.initials: KM
authors.lastname: Gaensler
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D000229:Dependovirus / Q000235:genetics* / Q000276:immunology; D005164:Factor IX / Q000235:genetics* / Q000276:immunology; D005260:Female; D015316:Genetic Therapy; D002836:Hemophilia B / Q000235:genetics / Q000276:immunology / Q000628:therapy*; D006801:Humans; D007108:Immune Tolerance; D016219:Immunotherapy, Adoptive; D007274:Injections, Intraperitoneal; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D037182:T-Cell Antigen Receptor Specificity; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D019076:Transgenes
chemical_list: D053645:Interleukin-2 Receptor alpha Subunit; D005164:Factor IX