Cross-species efficacy of enzyme replacement therapy for CLN1 disease in mice and sheep

Abstract

CLN1 disease is a fatal neurodegenerative lysosomal storage disorder resulting from mutations in the CLN1 gene encoding the soluble lysosomal enzyme, palmitoyl-protein thioesterase-1 (PPT1). Therapies for CLN1 disease have proven challenging because of the aggressive disease course and the need to treat widespread areas of the brain and spinal cord. Indeed, gene therapy has proven less effective for CLN1 disease than for other similar lysosomal enzyme deficiencies. We therefore tested the efficacy of enzyme replacement therapy (ERT) by delivering monthly infusions of recombinant human PPT1 (rhPPT1) in PPT1-deficient mice (Cln1 −/− ), and CLN1 R151X sheep to assess scale up for translation. In Cln1 −/− mice, intracerebroventricular rhPPT1 delivery was the most effective route of administration, resulting in therapeutically relevant CNS levels of PPT1 activity. rhPPT1 treated-mice had improved motor function, reduced disease-associated pathology, and diminished neuronal loss. In CLN1 R151X sheep, intracerebroventricular infusions resulted in widespread rhPPT1 distribution and positive treatment effects measured by quantitative structural magnetic resonance imaging and neuropathology. These findings demonstrate the feasibility and therapeutic efficacy of intracerebroventricular rhPPT1 enzyme replacement therapy. This represents a key step towards clinical testing of ERT in children with CLN1 disease and highlights the importance of a cross-species approach to developing a successful treatment strategy.

Reduction of Neuroinflammation and Seizures in a Mouse Model of CLN1 Batten Disease using the Small Molecule Enzyme Mimetic, N-Tert-Butyl Hydroxylamine

“…In CLN1, progressive neuroinflammation can be characterized by increased numbers of glial fibrillary acidic protein (GFAP)-expressing astrocytes [36][37][38]. NtBuHA treatment has been shown to reduce GFAP-reactive cells in Cln1 -/mice at 6 months [26].…”

“…Viral-mediated gene therapies have shown promise for the treatment of CLN1 across several studies and treatment paradigms [20][21][22]52,53], and several important recent advancements in viral vector technology are working toward realizing the safe systemic delivery of a blood-brain barrier (BBB)-penetrant virus to achieve robust, widespread transduction of CNS cell-types [55,56]. Further, ERT has proven effective in Cln1 -/mice [37,57,58], with the most promising results coming from studies utilizing intracerebroventricular or intrathecal administration that allows intact enzyme to bypass the BBB [37,58]. However, the clinical application of both gene therapy and ERT approaches remains limited by a need to optimize the delivery (i.e., achieve widespread expression of the functional enzyme) and suppress potential adverse events [54].…”

Severe Central Nervous System Demyelination in Sanfilippo Disease

“…For the analysis of spinal cord, adjacent one-in-forty-eight series of 40 µm coronal sections from each mouse were stained on slides using a modified immunofluorescence protocol [28,29].…”

“…To quantify microgliosis (CD68-positive activated microglia) and myelination (MBP immunoreactivity), semiautomated thresholding image analysis was performed as described previously [28,29]. This involved collecting slide-scanned images at 10x magnification (Zeiss Axio Scan Z1 Fluorescence Slide Scanner) from each animal.…”

<strong>Recent Advances in the Genomic Resources for Sheep</strong>

“…The new highly contiguous ARS-UI_Ramb_v2.0 reference genome and associated annotation, provides a research tool that can inform studies designed to identify alleles encoding human physiological processes and diseases. One recent example, is the novel sheep model of CLN1 disease, in which gene editing was used to insert a disease-causing PPT1 (R151X) human mutation into the orthologous sheep locus (Eaton et al, 2019;Nelvagal et al, 2022). High-throughput CRISPR/Cas9 knock-out libraries, such as those available for pigs e.g., Yu et al, (2022), will help considerably with identifying novel alleles for genome editing in both human and farmed animal studies but at present a lack of suitable primary cell lines for sheep is a barrier to progress.…”