Recent studies have demonstrated that an intrinsic endocrine pathway is present in salivary glands, distinct from the classical exocrine pathway whereby digestive enzymes are produced and secreted into the saliva by the salivary glands under normal physiological conditions. As such, this distinct endocrine pathway has recently been shown to be capable of robust synthesis and secretion of non-regulated (i.e. constitutive) gene products into the vascular space as a result of retroductal administration of a gene therapy vector. Fabry disease is a member of the family of lysosomal storage diseases, a group of monogenic disorders characterized by deficiency or lack of a class of enzymes (e.g. alpha-Galactosidase A in Fabry disease) involved in intra-lysosomal catabolism of macromolecules. An interesting feature of these diseases is the observation that tissues lacking the specific lysosomal enzyme implicated in the disease are capable of uptake of the specific lysosomal enzyme from the vascular space. This physiology has led to the proposal and subsequent validation of """"""""Enzyme Replacement Therapy"""""""" wherein the missing enzyme is produced syntheically and infused intravenously to Fabry patients, resulting in a mitigation of disease symptoms. We seek to combine these emergent technologies into a salivary gland-based gene therapy strategy for Fabry disease in highly relevant mouse knockout model, namely B6;129-Gla(tm1/Kul/J), an alpha- Galactosidase A (-/O) model. We seek to test the hypothesis that an AAV vector containing the sequence for human alpha-Gal A delivered to the salivary glands in alpha-Gal A deficient """"""""Fabry"""""""" mice will result in systemic replacement of the enzyme and reversal of the specific systemic biochemical defect underlying Fabry disease.
Our specific aims i nvolve: 1) delivery of an alpha-Gal A containing vector to the salivary glands of Fabry mice and biochemical testing of systemic delivery of the enzyme, 2) careful examination of the organ biodistribution of the enzyme, and 3) optimization of dosing and immune physiology to achieve long-term expression of the enzyme. These studies will produce important insights into the technical paramaters of this system, including: longevity of transgene expression, host immune response, and mitigation of Fabry-associated pathology, and form the basis whereby other systemic disorders could be addressed using salivary glands as the biosynthetic site for systemic therapeutics. ? ? ?
| Passineau, Michael J; Fahrenholz, Timothy; Machen, Laurie et al. (2011) ?-Galactosidase A expressed in the salivary glands partially corrects organ biochemical deficits in the fabry mouse through endocrine trafficking. Hum Gene Ther 22:293-301 |
