EVALUATION OF DELIVERY SYSTEMS FOR RENAL GENE THERAPY

Mount Sinai School Of Medicine Of Cuny, New York NY

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Abstract

A number of renal diseases are either a result of a genetic defect or the result of a chronic systemic disease resulting in renal injury from both local as well as systemic production of specific mediators. Gene therapy either to replace a missing factor or to suppress the production of deleterious exogenous (virus) or endogenous mediators represents a promising new therapeutic approach for chronic renal disease. The success and safety of genetic therapy will depend on both the successful expression of the exogenous gene as well as the efficient and specific delivery of the gene to the appropriate target cell. Thus, optimum genetic constructs for expression in specific renal cell types and optimum systems for either ex vivo or in vivo delivery of an exogenous gene to the kidney need to be defined. The function of strong constitutive promoters as well as potentially more renal-specific promoters will be examined in primary cells from human and mouse kidney (including mesangial and fibroblasts as well as proximal tubule, thick ascending limb and distal tubule cells) as well as in vivo. Each of these promoters will be inserted upstream from the indicator genes, beta-gal(alone) and luciferase (with therapeutic genes), which will allow convenient tracking and quantitation of expression in vivo. Since many of the diseases resulting in renal failure are chronic in nature, a delivery system that will result in the long-term stability and expression of a therapeutic gene is desirable; best achieved through integration of the gene into the host chromosome. The defective parvovirus, adeno-associated virus (AAV), efficiently integrates into the host genome and has the added advantage of efficient transduction into non-dividing cells making it an attractive candidate for gene therapy in the kidney. Furthermore, data suggest that delivery of a therapeutic gene flanked by genetic components of AAV system delivered as DNA in a liposome might result in the efficient integration of a delivered gene in a host cell without the use of a recombinant virus. These two delivery systems will be used to define the efficiency of gene delivery in vitro to primary renal cells and in vivo (using a murine model) to renal cells. Specific issues that will be addressed will include the efficiency of delivery to specific cell types, strategies to enhance transduction particularly to non-dividing renal cells, integration characteristics of the AAV-based constructs and the potential toxicity when a gene is delivered in this vector system. A model of disease, HIV-1 associated nephropathy in the transgenic mouse will be utilized to define efficacy of gene inhibition in a pathogenic model.