Efficient transduction of pancreatic islets by feline immunodeficiency virus vectors1

Pancreatic islets transplanted into immunocompetent diabetic subjects are rapidly lost to apoptotic or lytic death or both. Genetic engineering of islets before transplantation with protective genes may enhance their posttransplantation survival. Accomplishing this goal requires the development of a safe, efficient vector for islet gene delivery.

The ability of feline immunodeficiency virus (FIV) vectors to transfer a green fluorescent protein (GFP) gene to NIT-1 cells and primary islets was measured and compared with murine leukemia virus (MLV) and human immunodeficiency virus (HIV) vectors. Islets were examined using confocal microscopy to determine the extent and pattern of infection. Toxicity of the procedure was assessed via measurement of glucose stimulation indices and by reversion of diabetic mice using either FIV-infected or control islet transplants.

FIV effectively transduces islets with no untoward effect on the insulin secretion capacity of the beta cells. When FIV, HIV, and MLV GFP vectors were standardized to the same 293 cell titer and used to infect NIT-1 cells or whole islets, the FIV transduced equal or greater numbers of cells relative to the HIV vector and significantly more than the MLV vector. Islets transduced with FIV GFP were transplanted in a murine model for diabetes and were shown to revert diabetes and express GFP 4 weeks after transduction and 3 weeks after transplantation.

FIV transduction is a nontoxic and efficient method to genetically modify pancreatic islets and may prove promising for delivering genes to augment islet survival after transplantation.