Preclinical Enzyme Replacement Therapy with a Recombinant β-Galactosidase-Lectin Fusion for CNS Delivery and Treatment of GM1-Gangliosidosis

Abstract

GM1-gangliosidosis is a catastrophic, neurodegenerative lysosomal storage disease caused by a deficiency of lysosomal β-galactosidase (β-Gal). The primary substrate of the enzyme is GM1-ganglioside (GM1), a sialylated glycosphingolipid abundant in nervous tissue. Patients with GM1-gangliosidosis present with massive and progressive accumulation of GM1 in the central nervous system (CNS), which leads to mental and motor decline, progressive neurodegeneration, and early death. No therapy is currently available for this lysosomal storage disease. Here, we describe a proof-of-concept preclinical study toward the development of enzyme replacement therapy (ERT) for GM1-gangliosidosis using a recombinant murine β-Gal fused to the plant lectin subunit B of ricin (mβ-Gal:RTB). We show that long-term, bi-weekly systemic injection of mβ-Gal:RTB in the β-Gal−/− mouse model resulted in widespread internalization of the enzyme by cells of visceral organs, with consequent restoration of enzyme activity. Most importantly, β-Gal activity was detected in several brain regions. This was accompanied by a reduction of accumulated GM1, reversal of neuroinflammation, and decrease in the apoptotic marker caspase 3. These results indicate that the RTB lectin delivery module enhances both the CNS-biodistribution pattern and the therapeutic efficacy of the β-Gal ERT, with the potential to translate to a clinical setting for the treatment of GM1-gangliosidosis.

Therapeutic developments for neurodegenerative GM1 gangliosidosis

“…Condori et al fused β-gal with plant lectin ricin toxin B-subunit (RTB), which binds cell-surface glycolipids/proteins that contain galactose/galactosamine (Cho and Jin, 2021), leading to a reduction of GM1 ganglioside levels in GM1-patient fibroblasts (Condori et al, 2016). IV injections of β-gal: RTB in GM1-affected mice led to moderate increases in neural β-gal activity (<10% normal) compared to untreated controls (Weesner et al, 2022). Similarly, injecting β-gal fused with a mouse transferrin monoclonal antibody twice a week for 17 weeks in GM1-affected mice led to functional improvements, despite negligible neural β-gal activity or ganglioside clearance (Przybilla et al, 2021).…”

Neuraminidase 1 regulates the cellular state of microglia by modulating the sialylation of Trem2

“…The PM fractions of 4-month-old WT and Neu1 -/hippocampi were isolated as previously described. 80 Mice were euthanized by CO2; hippocampi were isolated and homogenized in a 2-mL Kontes Dounce Homogenizer (Kimble) in 1 mL homogenizer solution.…”

A mouse systems genetics approach reveals common and uncommon genetic modifiers of hepatic lysosomal enzyme activities and glycosphingolipids

“…In the sphingolipidoses, a subset of LSDs, glycosphingolipids (GSLs), accumulate in late endocytic organelles (late endosomes/lysosomes) and participate in their pathological cascades 9 . Current treatments for LSDs include substrate reduction therapy (SRT), which aims to reduce the rate of biosynthesis of stored substrates 5,16,17 , and enzyme replacement therapies (ERT) aimed at replacing a deficient enzyme 18,19 . Emerging treatments include gene and cell therapies [20][21][22] and chaperones for improving enzyme folding and trafficking 23 .…”