Liver-specific gene therapy based on self-complementary adeno-associated virus for lysosomal acid lipase deficiency

Lysosomal acid lipase deficiency is a rare, autosomal-recessive disorder caused by inactivating mutations of the lysosomal acid lipase gene and accumulation of cholesteryl esters and triglycerides in lysosomes. Treatment with recombinant lysosomal acid lipase is effective, but involves safety risks and the production of neutralizing antibodies. In the current study, we examined gene therapy with a liver-specific, self-complementary adeno-associated virus 8 (P6-13/rscAAV8) that encodes the human lysosomal acid lipase.

Two age cohorts of C57BL/6J mice with homozygous lysosomal acid lipase deletion were included. A young cohort (9 weeks of age; n = 8 per dose group, four males and four females) received a single intravenous administration of P6-13/rscAAV8 at 0.6, 2, or 6 × 10¹² viral genomes per kg (vg/kg). An old cohort (28 weeks of age; n = 4 per dose group, all males) received P6-13/rscAAV8 at 1 or 6 × 10¹² vg/kg. Control mice received a non-coding vector encoding green fluorescent protein.

In the young cohort, the treatment restored expression of enzyme activity, normalized lipid profiles and body weight, mitigated enlargement of the liver and spleen, and reduced steatosis, inflammation, and fibrosis in the liver. These effects were associated with rescue of autophagic flux and mitochondrial function, as well as reduction of endoplasmic reticulum stress. Notably, the observed effects were much weaker when gene therapy with the same dose was conducted in the old cohort.

These findings suggest that P6-13/rscAAV8, when delivered early enough, may mitigate or even prevent the pathology of lysosomal acid lipase deficiency.