Efficient ex vivo transduction of pancreatic islet cells with recombinant adeno-associated virus vectors

The ability to transfer immunoregulatory, cytoprotective, or antiapoptotic genes into pancreatic islet cells may allow enhanced posttransplantation su rvival of islet allografts and inhibition of recurrent autoimmune destructi on of these cells in type 1 diabetes. However, transient transgene expressi on and the tendency to induce host inflammatory responses have limited prev ious gene delivery studies using viral transfer vectors. We demonstrate her e that recombinant adeno-associated virus (rAAV) serotype 2, a vector that can overcome these limitations, effectively transduces both human and murin e pancreatic islet cells with reporter genes as well as potentially importa nt immunoregulatory cytokine genes (interleukin-4, interleukin-10), althoug h a very high multiplicity of infection (10,000 infectious units/islet equi valent) was required. This requirement was alleviated by switching to rAAV serotype 5, which efficiently transduced islets at a multiplicity of infect ion of 100. Although adenovirus (Ad) coinfection was required for efficient ex vivo expression at early time points, islets transduced without Ad expr essed efficiently when they were transplanted under the renal capsule and a llowed to survive in vivo, The rAAV-delivered transgenes did not interfere with islet cell insulin production and were expressed in both beta- and non -beta -cells. We believe rAAV will provide a useful tool to deliver therape utic genes for modulating immune responses against islet cells and markedly enhance longterm graft survival.