Bicistronic adenovirus-mediated gene transfer of CTLA4Ig gene and CD40Ig gene result in indefinite survival of islet xenograft

Blockade of CD40-CD154 costimulatory pathway in mice and primates with anti-CD154 monoclonal antibodies results in prolonged survival of vascularized organs and islet grafts. CD40Ig, a recombinant fusion protein comprised of the extracellular domain of human CD40 molecule in frame fused with the site-mutated human IgG1 Fc region, abrogated the cognate interaction of CD40-CD154 pathway by binding the CD154 molecule. In this study, replication-defective adenovirus containing the CD40Ig gene was prepared by homologous recombination and used to infect freshly isolated islets from LEW rats (RT-1(1)) in vitro using a titered dose. The islet transfectants (500 per recipient) were transplanted under the left kidney capsule of streptozocin-rendered diabetic C57BL/6 mouse recipient (H-2(b)). The mean survival time of AdCD40Ig-transfected islet grafts was significantly prolonged, while mock-infected grafts and AdEGFP-transfected grafts were rejected in normal fashion. Additionally, dose-dependent prolongation of islet graft survival was observed in mice receiving AdCD40Ig-transfected grafts. In conclusion, local production of Cd40Ig via adenoviral-mediated gene transfer induced dose-dependent prolongation of LEW --> Balb-c islet xenografts.