Abstract Number: PB1102
Meeting: ISTH 2020 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia Gene Therapy
Background: Liver-directed gene therapy with adeno-associated viral (AAV) vectors delivering a clotting factor transgene into hepatocytes has shown successful results in adults with hemophilia. However, because of their non-integrating nature, AAV are diluted during liver growth, thus challenging their use in pediatric patients. We developed lentiviral vectors (LV), which integrate in the host cell genome, and showed efficient in vivo hepatocyte gene transfer in preclinical models (mice, dogs, non-human primates).
Aims: In view of a potential use of LV in pediatric patients, we treated 3 2-4 month-old hemophilia B puppies by systemic administration of LV and showed long-term efficacy for up to 3.5 years, after an initial decrease of factor IX (FIX) activity.
Methods: Longitudinal studies in mice treated as newborns with LV-luciferase showed stable total signal over time, which decreases around 3 weeks if normalized on mouse weight, similarly to what observed in dogs.
Results: By contrast, newborn mice treated with LV-GFP showed a continuous increase in size of GFP+ clusters of cells by 3D imaging, showing local proliferation and long-term maintenance of transduced hepatocytes, thus suggesting a decrease in transgene expression per cell rather than reduction of targeted hepatocytes during growth. We confirmed the same pattern in LV-FIX treated newborn mice, while administration in 2-week old mice resulted in stable and 3-fold higher FIX output compared to mice treated as neonates. We evaluated clonal proliferation of LV-transduced and untransduced hepatocytes in Alb-Cre/Rosa26-Confetti mice during growth and showed that only a fraction of cells generates continuously growing clusters, while the others appear quiescent.
Conclusions: Our data show that timing of LV administration impacts on gene therapy efficacy and suggest that different hepatocyte subpopulations contribute to liver growth. Our work will provide a rationale for the application of LV-mediated liver gene therapy to pediatric patients in order to guarantee life-long transgene maintenance.
[Human Factor IX expression after intravenous administration of lentiviral vector at the indicated age.]
To cite this abstract in AMA style:
Milani M, Starinieri F, Canepari C, Liu T, Moalli F, Ambrosi G, Plati T, Biffi M, Covino C, Nichols T, Iannacone M, Peters R, Naldini L, Cantore A. Investigating the Stability of Lentiviral Vector Targeted Liver Cells during Post-Natal Growth for in Vivo Gene Therapy of Hemophilia [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/investigating-the-stability-of-lentiviral-vector-targeted-liver-cells-during-post-natal-growth-for-in-vivo-gene-therapy-of-hemophilia/. Accessed September 29, 2023.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/investigating-the-stability-of-lentiviral-vector-targeted-liver-cells-during-post-natal-growth-for-in-vivo-gene-therapy-of-hemophilia/