title: The impact of minimally oversized adeno-associated viral vectors encoding human factor VIII on vector potency in vivo.
abstract: Recombinant adeno-associated viral (rAAV) vectors containing oversized genomes provide transgene expression despite low efficiency packaging of complete genomes. Here, we characterized the properties of oversized rAAV2/8 vectors (up to 5.4 kb) encoding human factor VIII (FVIII) under the transcriptional control of three liver promoters. All vectors provided sustained production of active FVIII in mice for 7 months and contained comparable levels of vector genomes and complete expression cassettes in liver. Therefore, for the 5.4 kb genome size range, a strong expression cassette was more important for FVIII production than the vector genome size. To evaluate the potency of slightly oversized vectors, a 5.1 kb AAVrh8R/FVIII vector was compared to a 4.6 kb (wild-type size) vector with an identical expression cassette (but containing a smaller C1-domain deleted FVIII) for 3 months in mice. The 5.1 kb vector had twofold to threefold lower levels of plasma FVIII protein and liver vector genomes than that obtained with the 4.6 kb vector. Vector genomes for both vectors persisted equally and existed primarily as high molecular weight concatemeric circular forms in liver. Taken together, these results indicate that the slightly oversized vectors containing heterogeneously packaged vector genomes generated a functional transgene product but exhibited a twofold to threefold lower in vivo potency.
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Sirkka
authors.initials: S
authors.lastname: Kyostio-Moore
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Berthelette
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Piraino
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Cathleen
authors.initials: C
authors.lastname: Sookdeo
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Bindu
authors.initials: B
authors.lastname: Nambiar
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Jackson
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Brenda
authors.initials: B
authors.lastname: Burnham
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Catherine R
authors.initials: CR
authors.lastname: O'Riordan
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Seng H
authors.initials: SH
authors.lastname: Cheng
authors.affiliation: Gene Therapy, Sanofi Genzyme , Framingham, Massachusetts, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Armentano