Targeted gene therapy with CD40Ig to induce long-term acceptance of liver allografts

Background. The purpose of this study was to modulate the immune response of rat liver transplant recipients by adenovirus-mediated gene transfer of CD40Ig, a secretable fusion protein designed to block the CD40-CD154 T-cell costimulation pathway. Methods. CD40Ig complementary DNA was created by joining the reverse transcriptase-polymerase chain,reaction complementary DNA products for the extracellular domain of marine CD40 to the Fc portion of murine IgG2a. AdCD40Ig and AdSIg (IgG2a-Fc control) recombinant adenoviruses were used to transduce donor liver grafts before nonarterialized orthotopic rat liver transplantation. Donor specific unresponsiveness was examined with skin transplants. Results. All rats (n = 6) that received liver allografts transduced with AdCD40Ig survived > 100 days with normal liver histology. Serum levels of CD401g at 10, 30, 60, and 100 days after transplantation ranged from 100 to 500, 100 to 250, 5 to 40, and 2 to 10 mug/mL, respectively. Mean survival of rats (n = 4) that received liver allografts transduced with AdSIg control adenovirus was 9.25 +/- 2.9 days. Long-term survivors were rechallenged with skin grafts 100 days after liver transplantations. Survival was 72, >100 (x 4) days for donor specific allogeneic skin grafts and 14, 14, 18, 19, and 21 days for third-party allogeneic skin grafts. Conclusions. Adenovirus-mediated gene transfer of CD40Ig into cold-preserved liver allografts before transplantation results in high levels of transgene expression with resultant long-term survival of hepatic allografts and donor specific unresponsiveness.