Abstract Details

B3 - Lysosomal Storage Diseases

49: Rescue of Lysosomal Acid Lipase Deficiency in Mice by AAV Liver Gene Transfer

Type: Oral Abstract Session

Presentation Details

Session Title: Lysosomal Storage Disorders






Lysosomal acid lipase deficiency (LAL-D) is an autosomal recessive disorder caused by mutation in LIPA gene resulting in fatal lipid accumulation in liver and spleen. The most severe form, if not treated, results in premature death within the first year of life due to hepatic insufficiency. Weekly administration of the enzyme replacement therapy (ERT) is the only available supportive treatment. Although life-saving, ERT is not curative and may be associated with development of neutralizing antibodies decreasing treatment efficacy.
To develop a curative treatment for LAL-D, we first characterized a new lal^-/- mouse model, generated by deleting the exon 4 of the LIPA gene, and then assessed an in vivo gene therapy. We confirmed the loss of LAL activity and the accumulation of lipids in liver and spleen which leads to an increase in organ weight, in liver transaminase and dyslipidaemia (HDL). Lal^-/- mice display a dysregulation of the haematological compartment, with an inflammatory profile: increase of granulocytes, monocytes, and platelets. We also have new promising data using imaging flow cytometry to investigate the number of lipid droplets in blood cells as a novel method to easily assess disease burden.
For gene therapy, we targeted the liver by systemically injecting 3-month-old lal^-/- male mice using the AAV-8 serotype encoding the hLIPA gene under the control of hepatocyte-specific human α1-antitrypsin (hAAT) promoter. Transduced hepatocytes would both produce LAL to correct their own metabolic impairment and secrete the enzyme in bloodstream to cross-correct affected tissues. We conducted an 3-months follow-up study of 4 different AAV-8 doses: 5X10¹¹ vg/kg; 1X10¹² vg/kg; 3X10¹² vg/kg; 1X10¹³ vg/kg. Starting from two weeks after injection, we increased LAL activity in plasma and we observed a therapeutic effect with decrease of hepatic transaminases and normalization of haematological parameter. At 3-months post-injection, we evaluated vector biodistribution, enzymatic activity and tissue correction by histological staining and cholesterol/triglycerides quantification. As expected, AAV-treated lal^-/- mice displayed efficient hepatocyte transduction and LAL expression proportional to the injected doses. Noteworthy, all AAV doses were sufficient to reduce or correct hepatosplenomegaly and lipid accumulation with 3X10¹² vg/kg being the best compromise between AAV dose and disease correction.
With this minimal corrective dose, we assessed phenotype correction in lal^-/- mice at 1-, 3-, and 8- months post-injection. Firstly, AAV administration extended survival, improved body weight, and stably normalize haematological parameters, hepatosplenomegaly, lipid accumulation and tissues architectures along the 8-months follow-up. Secondly, using liver transcriptomic analysis, we observed a previously unreported impairment of mitochondria, which was confirmed by biochemical analysis and fully corrected by gene therapy. To further decrease vector dose, we engineered a novel LIPA cDNA to improve LAL expression and secretion by optimizing the codon usage and changing its signal peptide sequence and we are currently evaluating its therapeutic benefit in vivo. Finally, we are testing this strategy in lal^-/- human liver organoids.
Overall, our in vivo gene therapy strategy represents an effective approach to achieve stable LAL expression and correct LAL-D disease opening the possibility of developing a curative treatment to improve patients’ life expectancy and quality.

Plain Language Summary

Lysosomal acid lipase deficiency (LAL-D) is an autosomal recessive disorder caused by mutation in LIPA gene, which results in fat accumulation in liver and spleen leading to multi-organ failure. The most severe form of LAL-D, if not treated, results in premature death within the first year of life due to failure to thrive and hepatic insufficiency. To develop a curative treatment for LAL-D, we assessed a gene therapy treatment based on the in vivo administration of an AAV vector encoding LIPA cDNA. Transduced hepatocytes would both produce lysosomal acid lipase to correct their own metabolic impairment and secrete the enzyme in bloodstream to cross-correct affected tissues. AAV administration extended survival, improved body weight, and stably normalize haematological parameters, hepatosplenomegaly, lipid accumulation and tissues architectures along the 8-months follow-up. Overall, our in vivo gene open the possibility of developing a curative treatment to improve LAL-D patients’ life expectancy and quality.

Marine Laurent^1,2, Rim Harb^1,2, Christine Jenny^1,2, Julie Oustelandt¹, Francesca Landini³, Guillaume Core^1,2, Anaïs Brassier⁴, Laetitia Van Wittenberghe1^1,2, Dagmar Kratky⁵, Giuseppe Ronzitti^1,2, Mario Amendola<sup>1,2

1</sup>UMRS_951 Genethon, Evry, France,²Genethon, Evry, France,³Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy,⁴Necker-Enfants-Malades University Hospital, Paris, France,⁵Division of Molecular Biology and Biochemistry, Medicine University of Graz, Graz, Austria"