B1 - Metabolic Diseases (including Diabetes)
1082: Determinants of AAV Persistence in a Mouse Model of Glycogen Storage Disease Type III
Type: Poster Session
Poster Board Number: 1082
Presentation Details
Session Title: Thursday Posters: Metabolic Diseases
Liver-directed gene transfer with Adeno-associated viral (AAV) vectors demonstrated long-term efficacy in a large number of clinical trials and relevant preclinical animal models (D’Avola D, 2016; Weber ND, 2023). However, transgene expression loss was reported for some individuals without any evident correlation with the development of an immune response (Konkle BA, 2021) suggesting that other mechanisms might be responsible of this phenomenon. Importantly, this loss of transgene expression is poorly recapitulated by the current rodent models, since long-term expression is usually achieved in mouse liver in absence of significant liver damage (Ronzitti G, 2016).
In this study, we hypothesized that subclinical liver conditions, such as fibrosis or hepatocyte metabolic impairment, may have an impact on the persistence of AAV liver gene transfer. To model such conditions, we used a mouse model of glycogen storage disease type III (GSDIII), which displays features of chronic liver damage as well as a mild progressive fibrosis.
The relatively low level of fibrosis observed in this model did not impact gene transfer efficacy at short-term while, at long-term efficacy loss was observed with a kinetic similar to the one observed in humans. Importantly, the reduction of CpG dinucleotides in the transgene sequence and in the promoter of the expression cassette resulted in longer transgene expression stability and correction of the metabolic phenotype in the majority of the AAV-treated GSDIII mice. Interestingly, despite this optimization some of the mice showed robust transgene expression loss associated with transcriptional inactivation that was further characterized.
Among mechanisms potentially affecting vector stability and persistence over time, we showed that hepatocytes proliferation, if not corrected, can lead to transgene expression loss due to AAV dilution starting from three months after treatment. Interestingly, in the same experimental setup, we identified differential methylation of the promoter sequence occurring specifically in GSDIII mice suggesting a deregulation of the epigenetic mechanisms in this mouse strain.
Finally, adaptive immune responses triggered by the capsid or by the transgene were investigated highlighting an enrichment of non-conventionally activated effector/memory CD8+ T cells and an increase of CD8+ T cell infiltrates in the liver of Agl-/- mice one month after vector injection. The characterization of the role of these T cell infiltrates in the loss of correction observed over time is still undergoing in our model.
In conclusions, our work suggests the involvement of multiple mechanisms in the long-term persistence of AAV genome and transgene expression in the mouse GSDIII liver. These findings support the hypothesis that the variable efficacy and long-term persistence observed in the clinical trials may be related to the presence of an underlying subclinical metabolic impairment, proliferation associated with fibrosis and/or the presence of a pro-immunogenic environment. These mechanisms should be investigated in patients enrolled in liver-targeted gene therapy clinical trials to better understand their contribution in humans and improve the outcome of liver gene therapy.
Plain Language Summary
Liver AAV-based gene therapies have shown impressive preclinical and clinical results. Despite this efficacy, many clinical trials faced limitations, related to long-term efficacy supporting the study of the mechanisms mediating transgene expression loss after liver gene transfer. Here we used a mouse model of glycogen storage disease type III (GSDIII), which displayed features of chronic liver damage, to study in detail the mechanisms impacting transgene expression after AAV-mediated liver gene transfer. In GSDIII mice, a loss of transgene expression was observed over time, reminiscent of what was described in some of the patients undergoing liver gene transfer. The identification of the mechanisms responsible for this loss of expression represents a step forward to the improvement of the outcome of liver gene therapy in humans.
Justine Nozi1,2, Hanadi Saliba1,2, Youssef Krimi Benchekroun1,2, Jeremy Rouillon1,2, Gianni Tavella1,2, Valle Montalvo-Romeral1,2, Bérangère Bertin1,2, Louisa Jauze1,2, Helene Jammes3,4, Alice Jouneau3,4, Coralie Pecquet1,2, Louis Bergantz1,2, Andrés F. Muro5, Giulia Bortolussi5, Sylvain Fisson1,2, Nathalie Daniele1, Laetitia Van Wittenberghe1, David A. Gross1,2, Tiziana La Bella1,2, Antoine Gardin1,2, Giuseppe Ronzitti1,2
1GENETHON, Evry, France,2Université Paris-Saclay, Univ Evry, Inserm, Genethon, Integrare Research Unit UMR_S951, Evry, France,3Université Paris Saclay, UVSQ, INRAE, BREED, Jouy en Josas, France,4Ecole Nationale Vétérinaire d'Alfort, BREED, Maisons-Alfort, France,5International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy"
Find This Session