The long-range goal of this proposal is development of gene transfer therapy for human Alport syndrome, a genetic renal disease for which kidney transplantation currently is the only treatment. The disease results from mutations in genes for type IV collagen, which is an integral component of tissue structures known as basement membranes. Abnormalities leading to renal failure are initiated by deterioration of the glomerular basement membrane (GBM) that occurs because of an absence of normal type IV collagen in the GBM. The central hypothesis of this proposal is that the normal type IV collagen composition of the GBM can be adequately restored by transferring a correct copy of the defective gone into the glomerular cells that synthesize GBM proteins, thus stabilizing GBM structure and slowing or stopping progression of Alport renal disease. In X-linked Alport syndrome, the gene (COL4A5) that encodes the a5 chain of type IV collagen is mutated. The objective of this application is to use a new method of achieving gene transfer into glomerular cells to treat dogs with X-linked Aiport syndrome (XLAS).
Specific aims of the proposal are to: (1) use a virus vector delivered by an open surgical technique for closed-circuit renal perfusion that successfully transferred a cDNA encoding c_5type IV collagen into the glomeruli of normal pigs to treat dogs with XLAS, (2) construct new viral vectors containing full-length COL4A5 cDNAs that will enable stable transgene expression for up to one year, (3) develop minimally invasive methods for performing closed circuit perfusion of the kidney using trans-vascular catheterization techniques to permit repeated treatment of individual subjects, and (4) perform randomized trials of gene transfer therapy for XLAS in dogs. Effects of transgenic E5(IV) chain expression on the molecular, structural and functional properties of Alport GBM and on the clinical course of Alport renal disease will be determined. The mild renal disease phenotype manifested in female heterozygotes with XLAS suggests that even achieving mosaic expression of normal _5(IV) chains in male hemizygotes will produce a clinically satisfactory treatment result. Because canine XLAS is an animal model of human Alport syndrome, successful gene transfer therapy for XLAS in dogs will provide a basis for trials of such treatment for Alport syndrome in people. It will also lay the foundation for gene transfer therapy of other glomerular iseases.
