Lentiviral-mediated gene correction of mucopolysaccharidosis type IIIA

Donald S Anson,Peter R Clements,Belinda Thomas,Kylie Dunning,Ainslie Roberts,Sharon Byers,Enzo Ranieri,Rachel Koldej,Chantelle Mcintyre

doi:10.1186/1479-0556-5-1

Abstract

BackgroundMucopolysaccharidosis type IIIA (MPS IIIA) is the most common of the mucopolysaccharidoses. The disease is caused by a deficiency of the lysosomal enzyme sulphamidase and results in the storage of the glycosaminoglycan (GAG), heparan sulphate. MPS IIIA is characterised by widespread storage and urinary excretion of heparan sulphate, and a progressive and eventually profound neurological course. Gene therapy is one of the few avenues of treatment that hold promise of a sustainable treatment for this disorder.MethodsThe murine sulphamidase gene cDNA was cloned into a lentiviral vector and high-titre virus produced. Human MPS IIIA fibroblast cultures were transduced with the sulphamidase vector and analysed using molecular, enzymatic and metabolic assays. High-titre virus was intravenously injected into six 5-week old MPS IIIA mice. Three of these mice were pre-treated with hyperosmotic mannitol. The weight of animals was monitored and GAG content in urine samples was analysed by polyacrylamide gel electrophoresis.ResultsTransduction of cultured MPS IIIA fibroblasts with the sulphamidase gene corrected both the enzymatic and metabolic defects. Sulphamidase secreted by gene-corrected cells was able to cross correct untransduced MPS IIIA cells. Urinary GAG was found to be greatly reduced in samples from mice receiving the vector compared to untreated MPS IIIA controls. In addition, the weight of treated mice became progressively normalised over the 6-months post-treatment.ConclusionLentiviral vectors appear promising vehicles for the development of gene therapy for MPS IIIA.

Highlights

Mucopolysaccharidosis type IIIA (MPS IIIA) is the most common of the mucopolysaccharidoses
The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders that arise from deficiencies in the catabolism of glycosaminoglycans (GAG) [1]
MPS IIIA results from a genetically determined deficiency of sulphamidase, a lysosomal enzyme which normally catalyses the cleavage of N-linked sulphate from glucosamine residues at the nonreducing terminus of heparan sulphate

Summary

Introduction

Mucopolysaccharidosis type IIIA (MPS IIIA) is the most common of the mucopolysaccharidoses. The disease is caused by a deficiency of the lysosomal enzyme sulphamidase and results in the storage of the glycosaminoglycan (GAG), heparan sulphate. Affected patients usually present by 2– 3 years of age with a range of symptoms related to CNS pathology. MPS IIIA results from a genetically determined deficiency of sulphamidase, a lysosomal enzyme which normally catalyses the cleavage of N-linked sulphate from glucosamine residues at the nonreducing terminus of heparan sulphate. As this represents an obligatory step in the degradation of heparan sulphate, elevated levels of heparan sulphate fragments are found in tissues and in the urine. MPS IIIA results in the secondary storage of GM2 and GM3 gangliosides in the CNS

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Conclusion