title: Intracerebroventricular gene therapy that delays neurological disease progression is associated with selective preservation of retinal ganglion cells in a canine model of CLN2 disease.
abstract: CLN2 disease is one of a group of lysosomal storage disorders called the neuronal ceroid lipofuscinoses (NCLs). The disease results from mutations in the TPP1 gene that cause an insufficiency or complete lack of the soluble lysosomal enzyme tripeptidyl peptidase-1 (TPP1). TPP1 is involved in lysosomal protein degradation, and lack of this enzyme results in the accumulation of protein-rich autofluorescent lysosomal storage bodies in numerous cell types including neurons throughout the central nervous system and the retina. CLN2 disease is characterized primarily by progressive loss of neurological functions and vision as well as generalized neurodegeneration and retinal degeneration. In children the progressive loss of neurological functions typically results in death by the early teenage years. A Dachshund model of CLN2 disease with a null mutation in TPP1 closely recapitulates the human disorder with a progression from disease onset at approximately 4 months of age to end-stage at 10-11 months. Delivery of functional TPP1 to the cerebrospinal fluid (CSF), either by periodic infusion of the recombinant protein or by a single administration of a TPP1 gene therapy vector to the CSF, significantly delays the onset and progression of neurological signs and prolongs life span but does not prevent the loss of vision or modest retinal degeneration that occurs by 11 months of age. In this study we found that in dogs that received the CSF gene therapy treatment, the degeneration of the retina and loss of retinal function continued to progress during the prolonged life spans of the treated dogs. Eventually the normal cell layers of the retina almost completely disappeared. An exception was the ganglion cell layer. In affected dogs that received TPP1 gene therapy to the CSF and survived an average of 80 weeks, ganglion cell axons were present in numbers comparable to those of normal Dachshunds of similar age. The selective preservation of the retinal ganglion cells suggests that while TPP1 protein delivered via the CSF may protect these cells, preservation of the remainder of the retina will require delivery of normal TPP1 more directly to the retina, probably via the vitreous body.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, USA. Electronic address: whitingre@health.missouri.edu.
authors.forename: Rebecca E H
authors.initials: REH
authors.lastname: Whiting
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, USA. Electronic address: jensenc@health.missouri.edu.
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Jensen
authors.affiliation: Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, USA. Electronic address: pearcej@missouri.edu.
authors.forename: Jacqueline W
authors.initials: JW
authors.lastname: Pearce
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, USA. Electronic address: gillespiel@health.missouri.edu.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Gillespie
authors.affiliation: Division of Biological Sciences, University of Missouri, Columbia, USA. Electronic address: debdn2@mail.missouri.edu.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Bristow
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, USA. Electronic address: katzm@health.missouri.edu.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Katz
mesh_terms: D000626:Aminopeptidases / Q000008:administration & dosage / Q000235:genetics / Q000627:therapeutic use*; D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000473:pathology; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000008:administration & dosage / Q000235:genetics / Q000627:therapeutic use*; D004195:Disease Models, Animal; D018450:Disease Progression; D004285:Dogs; D004596:Electroretinography; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000134:cerebrospinal fluid; D057967:Infusions, Intraventricular; D009472:Neuronal Ceroid-Lipofuscinoses / Q000628:therapy*; D009900:Optic Nerve / Q000166:cytology; D012025:Reflex, Pupillary / Q000502:physiology; D012162:Retinal Degeneration / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D057057:Serine Proteases / Q000008:administration & dosage / Q000235:genetics / Q000627:therapeutic use*; D000091346:Tripeptidyl-Peptidase 1
chemical_list: D000091346:Tripeptidyl-Peptidase 1; D057057:Serine Proteases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C000717267:TPP1 protein, human
keywords: Gene therapy; Neuronal ceroid lipofuscinosis; Optic nerve; Retinal degeneration