title: Transgene expression levels and kinetics determine risk of humoral immune response modeled in factor IX knockout and missense mutant mice.
abstract: Immune responses leading to antibody-mediated elimination of the transgenic protein are a concern in gene replacement for congenital protein deficiencies, for which hemophilia is an important model. Although most hemophilia B patients have circulating non-functional but immunologically crossreactive factor IX (FIX) protein (CRM+ phenotype), inciting factors for FIX neutralizing antibody (inhibitor) development have been studied in crossreactive material-negative (CRM-) animal models. For this study, determinants of FIX inhibitor development were compared in hemophilia B mice, in which circulating FIX protein is absent (CRM- factor IX knockout (FIXKO) model) or present (CRM+ missense R333Q-hFIX model) modeling multiple potential therapies. The investigations compare for the first time different serotypes of adeno-associated virus (AAV) vectors (AAV2 and AAV1), each at multiple doses, in the setting of two different FIX mutations. The comparisons demonstrate in the FIXKO background (CRM- phenotype) that neither vector serotype nor vector particle number independently determine the inhibitor trigger, which is influenced primarily by the level and kinetics of transgene expression. In the CRM+ missense background, inhibitor development was never stimulated by AAV gene therapy or protein therapy, despite the persistence of lymphocytes capable of responding to FIX with non-inhibitory antibodies. This genotype/phenotype is strongly protective against antibody formation in response to FIX therapy.
authors.affiliation: The Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7220, USA.
authors.forename: T-P
authors.initials: TP
authors.lastname: Zhang
authors.forename: D-Y
authors.initials: DY
authors.lastname: Jin
authors.forename: R M
authors.initials: RM
authors.lastname: Wardrop
authors.forename: T
authors.initials: T
authors.lastname: Gui
authors.forename: R
authors.initials: R
authors.lastname: Maile
authors.forename: J A
authors.initials: JA
authors.lastname: Frelinger
authors.forename: D W
authors.initials: DW
authors.lastname: Stafford
authors.forename: P E
authors.initials: PE
authors.lastname: Monahan
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000276:immunology*; D003429:Cross Reactions; D005164:Factor IX / Q000235:genetics* / Q000276:immunology; D015870:Gene Expression; D015316:Genetic Therapy / Q000009:adverse effects* / Q000379:methods; D005822:Genetic Vectors / Q000235:genetics*; D006467:Hemophilia A / Q000097:blood / Q000276:immunology / Q000628:therapy; D006801:Humans; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008954:Models, Biological; D020125:Mutation, Missense; D012306:Risk; D014161:Transduction, Genetic / Q000379:methods; D019076:Transgenes
chemical_list: D001323:Autoantibodies; D005164:Factor IX