Long-term Amelioration of Feline Mucopolysaccharidosis VI After AAV-mediated Liver Gene Transfer

Mucopolysaccharidosis VI (MPS VI) is caused by deficient arylsulfatase B (ARSB) activity resulting in lysosomal storage of glycosaminoglycans (GAGs). MPS VI is characterized by dysostosis multiplex, organomegaly, corneal clouding, and heart valve thickening. Gene transfer to a factory organ like liver may provide a lifetime source of secreted ARSB. We show that intravascular administration of adenoassociated viral vectors (AAV) 2/8-TBG-felineARSB in MPS VI cats resulted in ARSB expression up to 1 year, the last time point of the study. In newborn cats, normal circulating ARSB activity was achieved following delivery of high vector doses (6 x 10(13) genome copies (gc)/kg) whereas delivery of AAV2/8 vector doses as low as 2 x 10(12) gc/kg resulted in higher than normal serum ARSB levels in juvenile MPS VI cats. In MPS VI cats showing high serum ARSB levels, independent of the age at treatment, we observed: (i) clearance of GAG storage, (ii) improvement of long bone length, (iii) reduction of heart valve thickness, and (iv) improvement in spontaneous mobility. Thus, AAV2/8-mediated liver gene transfer represents a promising therapeutic strategy for MPS VI patients.