FELINE ALPHA-MANNOSIDOSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A colony of carriers of alpha-mannosidosis was derived from a family of Persian cats in which affected kittens were found. Breeding studies showed this to be an autosomal recessive trait, with progressive neurologic signs and death by 6 months of age. Clinical, pathologic, enzyme, and molecular studies have characterized this disorder as a potential model for gene therapy. Studies of bone marrow transplantation have shown substantial amelioration of neurologic signs and prolongation of life, indicating that gene transfer to bone marrow stem cells should be an effective means of therapy. We have developed a collaborative study using the cat model for in utero transplantation of activated adult cat monocytes and gene therapy with Janis Abkowitz, MD, University of Washington, Seattle, WA. This work is separately funded through a subcontract of Dr. Abkowitz. We have characterized the peripheral and central nervous system myelin abnormalities in cats with alpha-mannosidase which was necessary to plan gene transfer studies. Adeno-associated virus (AAV) vectors are capable of delivering a therapeutic gene to the mouse brain that can result in long-term and widespread protein production. However, the human infant brain is more than 1,000 times larger than the mouse brain, which will make the treatment of global neurometabolic disorders in children more difficult. We evaluated the ability of three AAV serotypes (1,2, and 5) to transduce cells in the cat brain as a model of a large mammalian brain. The human lysosomal enzyme fl-glucuronidase (GUSB) was used as a reporter gene because it can be distinguished from feline GUSB by heat stability. The vectors were injected into the cerebral cone.x, caudate nucleus, thalamus, corona radiata, internal capsule, and centrum semiovale of eight-week-old cats. The brains were evaluated for gene expression using in situ hybridization and enzyme histochemistry 10 weeks after surgery. The AAV2 vector was capable of transducing cells in the gray matter, while the AAV 1 vector resulted in greater transduction of the gray matter than AAV2 as well as transduction of the white matter. AAV5 did not result in detectable transduction in the cat brain. Based on these data, we treated six affected cats with an AAV I vector carrying the feline MANB cDNA, Intracranial injection of this vector resulted in remarkable improvement in clinical neurological signs and in magnetic resonance imaging of white matter. Although gene transfer was limited to the areas surrounding the injection tracks, storage lesions were reduced throughout the brain. Thus global improvement in neuropathology can be achieved in a large mammalian brain using a clinically feasible number of injections, and can mediate clinically significant improvement in the neurological disease syndrome.